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	description	The present U.S. patent application claims priority under the Paris Convention of Japanese Patent Application No. 2015-108208 filed on May 28, 2015 the entirety of which is incorporated herein by reference. Field of the Invention The present invention relates to an X-ray Talbot capturing apparatus using a Talbot interferometer or Talbot-Lau interferometer. Description of Related Art There is an X-ray capturing apparatus which uses a Talbot interferometer or Talbot-Lau interferometer and a radiation detector (Flat Panel Detector: FPD) to capture and image a phase shift of an X-ray generated when the X-ray passes through an object (For example, Japanese Patent Application Laid-Open Publication No. 2007-206075, Japanese Patent Application Laid-Open Publication No. 2012-13530). Such X-ray image capturing apparatuses which use the Talbot interferometer or Talbot-Lau interferometer is called a X-ray Talbot capturing apparatus. The X-ray Talbot capturing apparatus includes a first grating (also called G1 grating, etc.) and a second grating (G2 grating, etc.) provided with slits at a certain interval (when the Talbot-Lau interferometer is used, a ray source grating (G0 grating, multi gratin) is also included). The second grating is positioned in the position where a self-image of the first grating is focused at a certain interval downstream of the X-ray irradiating direction of the first grating by emitting the X-ray to the first grating from the X-ray source. The second grating is positioned so that the extending direction of the slit in the second grating is slightly tilted with respect to the extending direction of the slit in the first grating. With this, a moire fringe is formed on the second grating. The image with the moire fringe superimposed (hereinafter referred to as moire image) is detected with the X-ray detector positioned downstream of the second grating and captured. When the subject is positioned between the X-ray source (or ray source grating) and the first grating or the first grating and the second grating, the moire fringe is distorted by the subject. Therefore, a plurality of moire images are captured with the X-ray Talbot capturing apparatus while relatively moving the first grating and the second grating (fringe scanning method) and then image processing is performed to analyze the moire images to reconstruct and generate images such as a differential phase image, absorption image, small angle scattering image, etc. Alternatively, one moire image including the subject can be captured with the X-ray Talbot image capturing apparatus, and the image processing can be performed to perform Fourier transform on the moire image to reconstruct and generate the differential phase image (Fourier transforming method). In the X-ray Talbot capturing apparatus, the radiation irradiated from the radiation source (or the radiation which is irradiated from the radiation source and passes the ray source grating) normally spreads in a cone beam shape, and when the grating is formed in a flat plane shape, the problem of vignetting occurs in the periphery of the grating. In other words, although illustration is omitted, when the slit S of the grating (see later described FIG. 3) is formed to pass radiation entering the radiation entering surface of the grating in the normal vector direction, the radiation enters the radiation entering surface in a direction tilted with respect to the normal vector direction in the periphery of the grating. Therefore, the rate of passing of the radiation becomes worse in the periphery of the grating than the center of the grating. Therefore, for example, Japanese Patent Application Laid-Open Publication No. 2007-206075, Japanese Patent Application Laid-Open Publication No. 2012-13530 describe a configuration in which the first grating and the second grating (or ray source grating) are curved. In other words, according to the method shown in FIG. 6 of Japanese Patent Application Laid-Open Publication No. 2007-206075 both edges of the grating are pressed in a direction toward the radiation source, the inner side is pressed in the opposite direction, and the grating is curved. According to the method shown in FIG. 7 of Japanese Patent Application Laid-Open Publication No. 2007-06075, with both edges of the grating fixed, the pressure applied to the radiation entering surface of the grating is set differently from the pressure applied to the radiation exiting surface (surface opposite of the radiation entering surface) to bend the grating. According to Japanese Patent Application Laid-Open Publication No. 2012-13530, a plurality of plate shaped small gratings are aligned and placed between a first and second supporting substrate to form a combined grating plate. The combined grating plate is placed between a concave surface stage and a convex surface stage to bend the combined grating plate. According to the above configuration, the radiation enters the radiation entering surface in the normal vector direction in any portion of the radiation entering surface of the grating in the bent combined grating plate. Therefore, this prevents vignetting. However, when the grating is formed with a hard material such as a silicon wafer, if the method shown in FIG. 6 of Japanese Patent Application Laid-Open Publication No. 2007-206075 is employed, strong force needs to be applied to the grating to bend the hard grating. However, if both edges of the grating and points on the inside are pressed with such strong force (in other words, contact by point), the grating may break and be damaged. If the method shown in FIG. 7 of Japanese Patent Application Laid-Open Publication No. 2007-206075 is employed, it is necessary to form a space with high airtightness and then vacuum the space in at least one side of the grating, which is not practical. According to the method described in Japanese Patent Application Laid-Open Publication No. 2012-13530, a plurality of small gratings are placed between the first and second supporting substrates to form one combined grating plate, and the radiation is absorbed by the first and second supporting substrates. Therefore, the signal value of the differential phase image, etc. reconstructed and generated from the moire image captured as described above reduces and the S/N ratio of the differential phase image becomes worse. Therefore, in the X-ray Talbot capturing apparatus, it is preferable to form the first grating and the second grating (or the ray source grating) by bending one flat plate grating formed with silicon wafer or the like. Moreover, it is desired that the damage due to breaking does not occur, the radiation is not blocked by the members other than the grating and the grating is accurately bent at a certain curvature. The present invention has been made in consideration of the above problems, and one of the main objects is to provide an X-ray Talbot capturing apparatus in which the plurality of gratings such as a first grating and a second grating are not damaged and a plurality of gratings can be accurately curved to suitably pass radiation without causing vignetting. In order to achieve at least one of the above-described objects, according to an aspect of the present invention, there is provided an X-ray Talbot capturing apparatus including: a plurality of gratings in which slits are formed; a radiation source which irradiates radiation to pass through the plurality of gratings; a radiation detector which captures a moire image; and a holder which holds the gratings, wherein, the holder includes a receiving unit including a receiving surface with a curve and a pressing unit including a pressing surface with a curve; each grating is held between the receiving surface of the receiving unit and the pressing surface of the pressing unit of the holder and bent in an arc shape with a point of the radiation source as a center; an elastic member is positioned between a first surface of the grating and the pressing surface of the pressing unit or a second surface of the grating opposite of the first surface and the receiving surface of the receiving unit; and an opening is provided in each of the receiving unit and the pressing unit of the holder and the elastic member so as not to block radiation irradiated on the grating. According to the Talbot capturing apparatus of the present invention, the plurality of gratings such as a first grating and a second grating are not damaged and a plurality of gratings can be accurately curved to suitably pass radiation without causing vignetting. Therefore, it is possible to accurately capture a moire image with the X-ray Talbot capturing apparatus and to accurately reconstruct the moire image to accurately generate a differential phase image. An embodiment of a Talbot capturing apparatus of the present invention is described with reference to the drawings. FIG. 1 is a perspective view showing an entire X-ray Talbot capturing apparatus of the present embodiment. As shown in FIG. 1, the X-ray Talbot capturing apparatus 1 of the present embodiment includes, a radiation source 2, a first cover unit 3 including a later described ray source grating 20, a supporting portion 4 which supports a first cover unit 3, etc., a subject stage 5, a second cover unit 6 including a later-described first grating 21, a second grating 22, and a radiation detector 23 (see later-described FIG. 4), and a column 7. Here, the principle common to the Talbot interferometer and the Talbot-Lau interferometer used in the X-ray Talbot capturing apparatus 1 is described using FIG. 2. FIG. 2 describes an example using the Talbot interferometer, and basically, the same description applies for the Talbot-Lau interferometer. In the Talbot interferometer, the radiation source 2, the first grating 21, and the second grating 22 are positioned in order in the radiation irradiating direction (in other words, z-direction). Although illustration is omitted, a ray source grating 20 (see FIG. 1) is positioned near the radiation source 2 in the Talbot-Lau interferometer. As shown in FIG. 2, in the Talbot interferometer and the Talbot-Lau interferometer, a subject H is positioned in a position upstream of the first grating 21 in the radiation irradiating direction (in other words, z-direction). Although illustration is omitted, the subject H can be positioned in the position downstream of the first grating 21 in the radiation irradiating direction. As shown in FIG. 3, in the first grating 21 and the second grating 22 (in a Talbot-Lau interferometer, the ray source grating 20 also) a plurality of slits S are formed aligned in a predetermined interval d in a x-direction orthogonal to the z-direction which is the radiation irradiating direction. The predetermined interval d is different in each of the first grating 21, the second grating 22, and the ray source grating 20. FIG. 3 describes the slit S relatively and greatly larger than the grating to make the slit S easily viewable. Then, the radiation (in the Talbot-Lau interferometer, the radiation irradiated from the radiation source 2 and multiplied by the ray source grating 20) irradiated from the radiation source 2 passes the first grating 21, and the passed radiation focuses an image at a certain interval in the z-direction. This image is called a self-image (also called a grating image). The self-image is formed in a certain interval in the z-direction, and this is called the Talbot effect. As shown in FIG. 2, the second grating 22 is positioned in the position where the self-image of the first grating 21 is focused. Here, the second grating 22 is positioned so that the extending direction of the slit S of the second grating 22 (in other words, y-axis direction in FIG. 2) forms a slight angle with respect to the extending direction of the slit S of the first grating 21. With such positioning, a moire image Mo consisting of only the moire fringe appears on the second grating 22. If the moire image Mo is drawn on the second grating 22, the moire fringe and the slit S are mixed, and the diagram becomes difficult to understand. Therefore, in FIG. 2, the moire image Mo is drawn separated from the second grating 22, but actually the moire image Mo is formed on or downstream the second grating 22. When there is a subject H within the range of the irradiation of radiation, the phase of the radiation is shifted by the subject H. Therefore, there is disorder in the moire fringe of the moire image Mo with the edge of the subject as the border, and the moire image Mo with the disorder by the subject H as shown in FIG. 2 appears on or downstream of the second grating 22. With this, the principle of the Talbot interferometer and the Talbot-Lau interferometer is described. The radiation detector 23 (see later described FIG. 4) positioned downstream of the second grating 22 captures the above-described moire image Mo. According to the present embodiment, the X-ray Talbot capturing apparatus 1 is configured based on this principle. The configuration of the X-ray Talbot capturing apparatus 1 of the present embodiment is described below. According to the present embodiment, the X-ray Talbot capturing apparatus 1 uses a Talbot-Lau interferometer including the ray source grating 20. The description below similarly applies to the X-ray Talbot capturing apparatus using the Talbot interferometer including only the first grating 21 and the second grating 22 without the ray source grating 20. The description below describes a configuration in which the X-ray Talbot capturing apparatus 1 is configured so that the radiation source 2 provided in the upper side irradiates radiation to the subject below as shown in FIG. 1. The present invention is not limited to the above, and the radiation can be emitted from the radiation source 2 in a horizontal direction or arbitrary direction to capture the moire image Mo of the subject. The radiation source 2 of the present embodiment includes a radiation source such as a Coolidge X-ray source or a rotating anode X-ray source which is widely used in medical practice. Alternatively, other types of radiation sources (tube) can be used. According to the present embodiment, a ray source grating 20 is provided downstream of the radiation source 2 in the radiation irradiating direction (in other words, z-direction). In order to prevent the vibration of the radiation source 2 from transmitting to the ray source grating 20, the ray source grating 20 is not attached to the radiation source 2, and is attached to a fixing member 4 attached to a support 7. Although illustration is omitted, in addition to the ray source grating 20, a filter (additional filter) to change the state of the radiation passing through the ray source grating or the irradiation field focus to focus the irradiation field of the irradiated radiation is attached to the fixing member 4. The subject stage 5 on which the subject can be placed, and the cover unit 6 to protect the first grating 21, the second grading 22, and the radiation detector 23 (see later described FIG. 4) are provided downstream of the ray source grating 20 in the radiation irradiating direction (in other words, z-direction). Although illustration is omitted, a holding apparatus can be positioned on the subject table 5, or a holding apparatus can be provided in the subject table 5 to hold the subject with the holding apparatus and fix the position of the subject or the angle with respect to the radiation irradiating direction. As shown in FIG. 4, the first grating 21, the second grating 22, the radiation detector 23, etc. is positioned in the cover unit 6. As described above, the interval of the first grating 21 and the second grating 22 is adjusted so that the second grating 22 is positioned in a position where a self-image is focused at a certain interval from the first grating 21 in the z-direction with the radiation irradiated from the radiation source 2 and passing through the first grating 21. The radiation detector 23 is positioned directly below the second grating 22, and the moire image Mo generated on the second grating 22 is captured with the radiation detector 23. Although illustration is omitted, the radiation detector (FPD) 23 is composed of conversion elements which generate electric signals according to the irradiated radiation positioned two-dimensionally (matrix shape). The electric signal generated by the conversion element is read as the image signal to capture the moire image Mo as the image signal of each conversion element. When the X-ray Talbot capturing apparatus 1 captures a plurality of moire images Mo using the fringe scanning method, the relative position between the first grating 21 and the second grating 22 is shifted in the x-axis direction shown in FIG. 4 (direction orthogonal to the extending direction (y-axis direction) of the slit S) to capture the plurality of moire images Mo. Therefore, a moving device, etc. (not shown) is provided to shift the relative position between the first grating 21 and the second grating 22 in the x-axis direction. When the X-ray Talbot capturing apparatus 1 captures one moire image Mo and the differential phase image is reconstructed and generated by Fourier transform, the moving device, etc. does not need to be provided. Although illustration is omitted, the moire image Mo captured with the X-ray Talbot capturing apparatus 1 is transmitted to the controller or the image processing apparatus. The controller or the image processing apparatus reconstructs and generates the absorption image and the differential phase image based on one or a plurality of moire images captured by the radiation detector 23. [Bent Configuration of Grating] Next, the configuration to bend each grating (ray source grating 20, first grating 21, second grating 22) in the X-ray Talbot capturing apparatus 1 of the present embodiment is described in detail. FIG. 2 and FIG. 4 show the first grating 21, etc. in a plane shape. However, actually, according to the present embodiment, the gratings 20, 21, and 22 are bent in an arc shape with a point of the radiation source 2 as the center (for example, focus of the radiation source 2 or exit of the radiation source 2, both are not shown) so that the radiation enters the radiation entering surface R in the normal direction in any portion of the radiation entering surface R of the gratings 20, 21, and 22. The first grating 21 is described below as an example, but the same can be said for when the ray source grating 20 or the second grating 22 is bent. As shown in FIG. 5A, FIG. 5B, and FIG. 6, the first grating 21 is held in the holder 30 in the bent state. The holder 30 includes a receiving unit 31, a pressing unit 32, and an elastic member 33. FIG. 5A is a perspective view showing the first grating 21 attached to the holder 30, and FIG. 5B is a cross-sectional view along line A-A in FIG. 5A. FIG. 6 is an exploded view of the holder 30. According to the present embodiment, each grating such as the first grating 21 is formed with one silicon wafer, etc. The receiving unit 31 and the pressing unit 32 of the holder 30 is formed with aluminum, iron, etc. from the viewpoint of hardness, ease of processing, cost, etc., however, the grating and the holder 30 can be applied to the present invention regardless of the material. The radiation is irradiated from the upper side to the lower side (z-direction) in FIG. 5A, FIG. 5B, and FIG. 6. According to the description below, the upper side of the diagram, in other words, the upstream side of the irradiating direction of radiation is described as upper side or top, and the lower side of the diagram, in other words, the downstream side of the irradiating direction of radiation is described as lower side or bottom. Nevertheless, as described above, for example, when the radiation is emitted in a horizontal direction from the radiation source 2 of the X-ray Talbot capturing apparatus 1 to capture the moire image Mo, the upstream side and the downstream side of the irradiating direction of the radiation becomes a horizontal direction (left and right direction). Further, FIG. 5A and FIG. 6 show only one representative slit S in the first grating 21 and the slit S is omitted in FIG. 5B. However, as described above, a plurality of slits S are provided in the first grating 21. Basically, in the present embodiment, the receiving unit 31 of the holder 30 is positioned on the lower side of the first grating 21 (in other words, the radiation emitting surface r side of the first grating 21), the pressing unit 32 of the holder 30 is positioned on the upper side of the first grating 21 (in other words, the radiation entering surface R side of the first grating 21), and the periphery of the first grating 21 is held between the receiving unit 31 and the pressing unit 32 of the holder 30 in the horizontal direction (top and bottom direction). Then, as shown in FIG. 5B, according to the present embodiment, the receiving unit 31 and the pressing unit 32 of the holder 30 are connected with screws 34 throughout the whole circle of the periphery, and the first grating 21 is held between the receiving unit 31 and the pressing unit 32. When the receiving unit 31 and the pressing unit 32 of the holder 30 are connected with the screws 34 at only a predetermined position of the periphery, the first grating 21 may not be accurately bent at the portions which are not connected with the screw 34 due to the high stiffness of the first grating 21. According to the present embodiment, the receiving unit 31 and the pressing unit 32 of the holder 30 are connected with screws 34 throughout the whole circle of the periphery. Therefore, it is possible to accurately prevent problems as described above, and to hold the first grating 21 (and the later-described elastic member 33) with an even strength between the receiving unit 31 and the pressing unit 32. According to the present embodiment, in the holder 30, the receiving surface 31B of the receiving unit 31 pressing the first grating 21 (in other words, the portion of the receiving surface 31B in a frame shape other than a later-described opening 31A of the receiving unit 31 of the holder 30) has a curve with a predetermined curvature. Moreover, the pressing surface 32B of the pressing unit 32 facing the receiving surface 31B of the receiving unit 31 receiving the first grating 21 and the elastic member 33 with the first grating 21 and the elastic member 33 in between (in other words, the portion of the pressing surface 32B in a frame shape other than a later-described opening 32A of the pressing unit 32 of the holder 30) has a curve with a predetermined curvature. In other words, according to the present embodiment, the receiving surface 31B of the receiving unit 31 of the holder 30 and the pressing surface 32B of the pressing unit 32 are bent in an arc shape with the above-described point of the radiation source 2 (for example, focus of the radiation source 2 or the exit of the radiation source 2, both are not shown) as the center. Then, when the first grating 21 is held with the holder 30, the first grating 21 is held between the curved receiving surface 31B of the receiving unit 31 provided in the downstream side of the irradiating direction of the radiation (bottom side of the figure) and the curved pressing surface 32B of the pressing unit 32 provided on the upstream side of the irradiating direction of the radiation (top side of the figure). With this, as described above, the first grating 21 is bent in an arc shape with the above-described point of the radiation source 2 (for example, focus of the radiation source 2 or the exit of the radiation source 2, both are not shown) as the center. When the receiving unit 31 and the pressing unit of the holder 30 are made, as described above, the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32 are made bent in an arc shape with the above-described point of the radiation source 2 (for example, focus of the radiation source 2 or the exit of the radiation source 2, both are not shown) as the center. However, since there is a limit to the accuracy of processing by machine, actually, the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32 are not made in an arc shape with the point of the radiation source 2 as the center without any error. Therefore, the present application describing an “arc shape with the point of the radiation source 2 as the center”, includes error of processing by the machine. According to the present embodiment, the elastic member 33 is positioned between the radiation entering surface R of the first grating 21 and the pressing surface 32B of the pressing unit 32 of the holder 30. FIG. 5A, FIG. 5B and FIG. 6 show the elastic member 33 positioned between the first grating 21 and the pressing unit 32. Alternatively, as described in the later-described FIG. 9A and FIG. 9B, the elastic member 33 can be positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31 of the holder 30. The openings 31A, 32A, and 33A are each provided in the receiving unit 31 and the pressing unit 32 of the holder 30 and the elastic member 33 so as not to block the radiation irradiated to the first grating 21. Here, when the radiation irradiated to the first grating 21 hits the receiving unit 31 or the pressing unit 32 of the holder 30 and reflects or scatters causing bad effects, for example, the receiving unit 31 and the pressing unit 32 can be formed from metal which does not pass radiation, for example, lead, or a metallic layer such as lead, can be provided in the portion of the surface of the receiving unit 31 which may be hit by the radiation. [Operation] Next, the operation of the X-ray Talbot capturing apparatus 1 of the present embodiment, specifically, the grating portions such as the ray source grating 20, the first grating 21, and the second grating 22 are described below. Below, the first grating 21 is described as an example, but the same description applies for the ray source grating 20 and the second grating 22. Moreover, the example of positioning the elastic member 33 between the first grating 21 and the pressing unit 32 of the holder 30 is described, but the same description applies for when the elastic member 33 is positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31. As described above, diffraction grating described in Japanese Patent Application Laid-Open Publication No. 2012-13530 is formed by aligning a plurality of small gratings placed between a first and second supporting substrate to form one bonded grating plate, and the bonded grating plate is bent by placing the bonded grating plate between a concave surface stage and a convex surface stage. Therefore, the bonded grating plate corresponds to the first grating (ray source grating 20, second grating 22) of the present embodiment and the concave surface stage and the convex surface stage corresponds to the receiving unit 31 and the pressing unit 32 of the holder 30 of the present embodiment. The conventional grating portion including the diffraction grating described in Japanese Patent Application Laid-Open Publication No. 2012-13530 is not provided with the elastic member 33 of the present embodiment between the first grating 21 (bonded grating plate in Japanese Patent Application Laid-Open Publication No. 2012-13530), and the receiving unit 31 and the pressing unit 32 of the holder 30 (concave surface stage and convex surface stage in Japanese Patent Application Laid-Open Publication No. 2012-13530). As described above, even if the receiving unit 31 and the pressing unit 32 of the holder 30 are made so that the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32 are shaped in an arc shape with the point of the radiation source 2 as the center, since there is a limit to the accuracy of processing by machine, actually, the center of the arc of the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32 is not always the exact same point of the radiation source 2. Therefore, when the elastic member 33 as described in the present embodiment is not provided between the first grating 21 (bonded grating plate) and the receiving unit 31 and the pressing unit 32 of the holder 30 (concave surface stage and convex surface stage), if the receiving unit 31 and the pressing unit 32 (concave surface stage and convex surface stage) are connected with screws 34 with the first grating (bonded grating plate) in between (see FIG. 5B), as shown in FIG. 7A, for example, the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32 (convex surface stage) may be closer to the holder 30 than the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 (concave surface stage). In this case, the first grating 21 (bonded grating plate) matches with the pressing unit 32 (convex surface stage) at a point in a position at substantially the center. As shown in FIG. 7B, the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32 (convex surface stage) of the holder 30 may be farther from the holder 30 than the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 (concave surface stage). In this case, the first grating 21 (bonded grating plate) matches with the receiving unit 31 (concave surface stage) at points in positions at both edges. When the first grating 21 is formed with a material with stiffness such as a silicon wafer, etc., as shown in FIG. 7B, the first grating 21 follows the pressing surface 32B of the pressing unit 32 (convex surface stage). FIG. 7A and FIG. 7B are schematic cross-sectional diagrams along line B-B of FIG. 5A when the elastic member 33 is not provided, and the later-described FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B are schematic cross-sectional diagrams along line B-B of FIG. 5A when the elastic member 33 is provided as in the present embodiment. In FIG. 7A and FIG. 7B, and the later-described FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B for the purpose of ease of understanding, the difference of the curvature and the difference of the curvature radius of the arc between the receiving unit 31 (concave surface stage) and the pressing unit 32 (convex surface stage) of the holder 30 is emphasized than the actual difference. Actually, there is hardly any difference in the position of the center (not shown) of the arc formed in the above. However, a slight difference occurs in the position of the center due to the limit of accuracy of processing by machine. Therefore, as shown in FIG. 7A and FIG. 7B, the first grating 21 (bonded grating plate) is matched at the point with the receiving unit 31 (concave surface stage) and the pressing unit 32 (convex surface stage). As described above, when the first grating 21 (bonded grating plate) is matched at the point with the receiving unit 31 and the pressing unit 32 of the holder 30 (concave surface stage and convex surface stage), the stress is concentrated in the portion of the matching point. This may cause damage to the first grating 21 such as the first grating 21 breaking at the portion of the matching point similar to the method shown in FIG. 6 of Japanese Patent Application Laid-Open Publication No. 2007-206075. According to the present embodiment, the elastic member 33 is positioned between the radiation entering surface R of the first grating 21 and the pressing surface 32B of the pressing unit 32 of the holder 30 resulting in a state as shown in FIG. 8A and FIG. 8B. FIG. 8A and FIG. 8B respectively correspond to FIG. 7A and FIG. 7B, and the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32 of the holder 30 may be closer to the holder 30 (FIG. 8A) or farther from the holder 30 than (FIG. 8B) the center (no shown) of the arc formed in the receiving surface 31B of the receiving unit 31. The elastic member 33 is positioned between the radiation entering surface R of the first grating 21 and the pressing surface 32B of the pressing unit 32. Since the elastic member 33 is positioned between the radiation entering surface R of the first grating 21 and the pressing surface 32B of the pressing unit 32 of the holder 30, even if there is a slight difference between the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 and the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32, as shown in FIG. 8A and FIG. 8B, the elastic member 33 suitably shrinks (that is, crushed) by the pressing force of the pressing unit 32, and the first grating 21 is entirely pressed to the receiving surface 31B of the receiving unit 31. In other words, instead of being matched at the point, the periphery of the first grating 21 (see FIG. 6) has surface contact with the receiving surface 31B of the receiving unit 31. Therefore, in the first grating 21, the entire radiation entering surface R is pressed against the elastic member 33, and the entire radiation exiting surface r is pressed against the receiving surface 31B of the receiving unit 31. Therefore, since the elastic member 33 is positioned between the radiation entering surface R of the first grating 21 and the pressing surface 32B of the pressing unit 32 of the holder 30, it is possible to accurately prevent the first grating 21 being matched at the point with the pressing unit 32 of the holder 30. Moreover, the first grating 21 has surface contact with the receiving surface 31B of the receiving unit 31 and the elastic member 33 due to the pressing force from the pressing surface 32B of the pressing unit 32. Therefore, stress concentration as in matching at the point does not occur, and it is possible to accurately prevent damage such as the first grating 21 breaking. When the curvature of the receiving surface 31B of the receiving unit 31 of the holder 30 to which the first grating 21 is pressed is processed in advance to be a certain value, the first grating 21 having surface contact with the receiving surface 31B of the receiving unit 31 is bent at the same curvature (that is, the certain curvature) as the curvature of the receiving surface 31B of the receiving unit 31. In other words, the first grating 21 is bent in an arc with the center being the same point as the center (not shown) (that is, the above-described point of the radiation source 2) of the arc formed in the receiving surface 31B of the receiving unit 31. For example, as shown in FIG. 9A and FIG. 9B, the elastic member 33 can be positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31 of the holder 30. FIG. 9A and FIG. 9B respectively correspond to FIG. 7A and FIG. 7B, and the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32 may be closer to (FIG. 9A) or farther from (FIG. 9B) the holder 30 than the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31. The elastic member 33 is positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31. When the elastic member 33 is positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31 of the holder 30, even if there is a slight difference between the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31, and the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32, as shown in FIG. 9A and FIG. 9B, the elastic member 33 suitably shrinks with the pressing force of the receiving unit 31. With this, the first grating 21 is entirely pressed against the pressing surface 32B of the pressing unit 32. Therefore, in the first grating 21, the entire radiation exiting surface r is pressed against the elastic member 33, and the entire radiation entering surface R is pressed against the pressing surface 32B of the pressing unit 32. Therefore, since the elastic member 33 is positioned between the radiation exiting surface r of the first grating 21 and the receiving surface 31B of the receiving unit 31 of the holder 30, it is possible to accurately prevent the first grating 21 being matched at the point with the receiving unit 31 and the pressing unit 32. Moreover, the first grating 21 has surface contact with the pressing surface 32B of the pressing unit 32 and the elastic member 33 due to the pressing force from the receiving surface 31B of the receiving unit 31. Therefore, stress concentration as in matching at the point does not occur, and it is possible to accurately prevent damage such as the first grating 21 breaking. When the curvature of the pressing surface 32B of the pressing unit 32 of the holder 30 to which the first grating 21 is pressed is processed in advance to be a certain value, the first grating 21 having surface contact with the pressing surface 32B of the pressing unit 32 is bent at the same curvature (that is, the certain curvature) as the curvature of the pressing surface 32B of the pressing unit 32. In other words, the first grating 21 is bent in an arc with the center being the same point as the center (not shown) (that is, the above-described point of the radiation source 2) of the arc formed in the pressing surface 32B of the pressing unit 32. [Effect] As described above, according to the X-ray Talbot capturing apparatus 1 of the present embodiment, when the first grating 21, etc. (that is, the ray source grating 20, the first grating 21, and the second grating 22) is held with the holder 30, the elastic member 33 is positioned between the radiation entering surface R of the first grating 21, etc. and the pressing surface 32B of the pressing unit 32 or the radiation exiting surface r of the first grating, etc. and the receiving surface 31B of the receiving unit 31. Therefore, even if the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30 is different from the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32 due to the limit of accuracy of processing by machine, the elastic member 33 suitably shrinks with the pressing force of the pressing unit 32 and the receiving unit 31. With this, the first grating 21 can be entirely pressed against the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32, that is, the first grating 21 has surface contact. As described above, in the X-ray Talbot capturing apparatus 1 of the present embodiment, stress concentration such as matching at the point does not occur when the holder 30 holds the first grating 21, etc. Therefore, it is possible to accurately prevent damage occurring, such as the first grating 21, etc. breaking. The curvature of the receiving surface 31B of the receiving unit 31 of the holder 30 and the pressing surface 32B of the pressing unit 32 is processed in advance to be a certain curvature, and the first grating 21, etc. in surface contact with the above is bent to have a certain curvature. Therefore, the first grating 21, etc. can be accurately bent in an arc with the point of the radiation source 2 (see FIG. 1 and FIG. 2) of the radiation source 2 as the center. Therefore, since the radiation enters the radiation entering surface R in the normal direction in any portion of the radiation entering surface R of the first grating 21, etc., it is possible to accurately prevent problems such as vignetting, and the radiation can be accurately passed. In the X-ray Talbot capturing apparatus 1 of the present embodiment, the openings 31A, 32A, and 33A are respectively provided in the receiving unit 31 and the pressing unit 32 of the holder 30 and the elastic member 33 so that the radiation irradiated to the first grating 21, etc. is not blocked. The radiation is not reflected or scattered by the receiving unit 31, the pressing unit 32 or the elastic member 33, and the radiation can pass accurately. According to the present embodiment, as described above, although there is a limit to the accuracy of processing by machine, forming the receiving unit 31 and the pressing unit 32 so that the position of the center of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30 and the position of the center of the arc formed in the pressing surface 32B of the pressing unit 32 are basically the same point of the radiation source 2 (that is, positions which are not shown such as the focus or the exit of the radiation source 2). However, as described above, for example, as shown in FIG. 8A and FIG. 8B, even if there is a difference between the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30 and the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32, the elastic member 33 positioned between the radiation entering surface R of the first grating 21, etc. and the pressing surface 32B of the pressing unit 32 of the holder 30 shrinks (that is, crushed) with the pressing force of the pressing unit 32 and the entire first grating 21 is pressed against the receiving surface 31B of the receiving unit 31. With the elastic member 33, the first grating 21, etc. is not separated from the receiving surface 31B of the receiving unit 31, and has surface contact with the receiving surface 31B of the receiving unit 31. Therefore, it is possible to accurately bend the first grating 21, etc. in an arc (that is, a predetermined curvature) with the center at the same point as the center (not shown) (that is, the above-described point of the radiation source 2) of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30. Moreover, for example, as shown in FIG. 9A and FIG. 9B, even if there is a difference between the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30 and the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing unit 32, the elastic member 33 positioned between the radiation exiting surface r of the first grating 21, etc. and the receiving surface 31B of the receiving unit 31 of the holder 30 shrinks (that is, crushed) with the pressing force of the receiving unit 31 and the pressing unit 32 and the entire first grating 21 is pressed against the pressing surface 32B of the pressing unit 32. With the elastic member 33, the first grating 21, etc. is not separated from the pressing surface 32B of the pressing unit 32, and has surface contact with the pressing surface 31B of the receiving unit. Therefore, it is possible to accurately bend the first grating 21, etc. in an arc (that is, a predetermined curvature) with the center at the same point as the center (not shown) (that is, the above-described point of the radiation source 2) of the arc formed in the pressing surface 32B of the pressing unit 32 of the holder 30. Therefore, the position of the center (not shown) of the arc formed in the receiving surface 31B of the receiving unit 31 of the holder 30 and the position of the center (not shown) of the arc formed in the pressing surface 32B of the pressing surface 32 of the holder 30 can be different as long as the elastic member 33 can suitably shrink (that is, crushed) with the pressing force of the receiving unit 31 and the pressing unit 32 and the first grating 21, etc. can be formed having accurate surface contact without the first grating 21 etc. of the holder 30 being separated from the receiving surface 31B of the receiving unit 31 or the pressing surface 32B of the pressing unit 32. In this case, when the surface to which the first grating 21, etc. is pressed (that is, the receiving surface 31B of the receiving unit 31 of the holder 30 (in FIG. 8A and FIG. 8B) or the pressing surface 32B of the pressing unit 32 of the holder 30 (in FIG. 8A and FIG. 8B)) with the elastic member 33 is formed bent in an arc shape with the point of the radiation source 2 as the center, the first grating 21, etc. is pressed to the surface with the elastic member 33 to be in surface contact. Therefore, the first grating 21, etc. can be suitably bent at the same predetermined curvature. [Detailed Configuration of Elastic Member] The configuration described below is preferable to better achieve the above-described effects of the X-ray Talbot capturing apparatus 1. [Configuration 1] According to the present embodiment, as described above, the elastic member 33 is suitably crushed by the pressing force of the pressing unit 32 of the holder 30 (in FIG. 8A and FIG. 8B) and the pressing force of the receiving unit 31 (in FIG. 9A and FIG. 9B). With this, the first grating 21 is pressed entirely against the receiving surface 31B of the receiving unit 31 (in FIG. 8A and FIG. 8B) and the pressing surface 32B of the pressing unit 32 (in FIG. 9A and FIG. 9B), that is a surface contact state. In order to form this state, it is preferable that the thickness of the elastic member 33 is 1.6 mm or more. It is preferable that the crushing margin (that is, amount of change of thickness) of the elastic member 33 is within a range of 0.6 to 0.7 mm when a load of 400 g is applied per 1 cm2. If the elastic member 33 is too soft, it becomes difficult to press the first grating 21, etc. having high stiffness with pressing force of the elastic member 33. As shown in FIG. 7B, the first grating 21, etc. becomes separated from the receiving surface 31B of the receiving unit 31 of the holder 30, and the first grating 21, etc. cannot be maintained at the predetermined curvature or the predetermined arc. If the elastic member 33 is too hard, the receiving unit 31 and the pressing unit 32 is deformed by the stiffness of the elastic member 33 and the first grating 21, etc. when the receiving unit 31 is connected to the pressing unit 32 with the screws 34 (see FIG. 5B) with the elastic member 33 and the first grating 21, etc. in between. Therefore, the curvature and the arc of the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32 (that is, the surface to which the first grating 21, etc. is pressed) are shifted from the predetermined curvature and the predetermined arc. When the elastic member 33 has a degree of hardness (or flexibility) as described above, it is possible to accurately prevent the above situations, and the first grating 21, etc. can be accurately bent at a suitable curvature by holding the first grating 21, etc. with the holder 30. In other words, the first grating 21 can be accurately bent in an arc with the center at the same point as the center (not shown) (that is, the point of the radiation source 2) of the arc formed in the side having contact (that is, the receiving surface 31B of the receiving unit 31 of the holder 30 or the pressing surface 32B of the pressing unit 32). [Configuration 2] For example, as shown in FIG. 10A, when the elastic member 33 is positioned between the first grating 21, etc. and the pressing member 32 of the holder 30, if the edge of the elastic member 33 is outside the edge α of the receiving surface 31B of the receiving unit 31 in contact with the first grating 21, etc. (that is, in contact without elastic member 33 in between), when the elastic member 33 is pressed with the pressing unit 32, stress concentration occurs in the portion of the edge α of the receiving surface 31B of the receiving unit 31 and damage such as the first grating 21, etc. breaking at this portion may occur. The same can be said for when the elastic member 33 is positioned between the first grating 21, etc. and the receiving unit 31 of the holder 30. As shown in FIG. 10B, when the edge of the elastic member 33 is outside the edge β of the pressing surface 32B of the pressing unit 32 in contact with the first grating 21, etc., if the receiving unit 31 presses the elastic member 33, the stress concentration occurs in the portion of the edge β of the pressing surface 32B of the pressing unit 32, and damage such as the first grating 21, etc. breaking at this portion may occur. Therefore, as shown in FIG. 5B, it is preferable that the edge of the elastic member 33 is not outside the edge of the surface (that is, the receiving surface 31B of the receiving unit 31 and the pressing surface 32B of the pressing unit 32) of the holder 30 on the side in contact with the first grating 21, etc. According to such configuration, it is possible to accurately prevent damage such as the first grating 21, etc. breaking at this portion. [Measure for Deforming of the Holder Due to Temperature] For example, as described above, the receiving unit 31 and the pressing unit 32 of the holder 30 is formed from aluminum, iron, etc. and the first grating 21, etc. is formed from a silicon wafer, etc. Since the thermal expansion coefficient is different between the silicon wafer and aluminum or iron, when the temperature increases, the degree of deforming of the receiving unit 31 and the pressing unit 32 is different from the degree of deforming of the grating of the first grating 21, etc. For example, therefore, problems may occur such as not being able to capture the suitable moire image Mo with the X-ray Talbot capturing apparatus 1 due to the shift in position of the first grating 21 in the receiving unit 31. [Configuration 3] The thermal expansion coefficient of aluminum is about 23×10-6/K and the thermal expansion coefficient of iron is about 12×10-6/K whereas the thermal expansion coefficient of the silicon wafer is about 3.3×10-6/K. Therefore, the ratio of the thermal expansion coefficient of aluminum or iron to the thermal expansion coefficient of the silicon wafer is about 7 times (Al) or 3.6 times (Fe). When the temperature rises, the difference in the thermal expansion coefficient is considered to be one of the reasons the shift in position of the first grating 21 occurs in the holder 30. The present inventors found that by forming the receiving unit 31 and the pressing unit 32 of the holder 30 with invar (a type of Fe—Ni alloy, thermal expansion coefficient is about 1.5×10-6/K) which is known to have a small thermal expansion coefficient, and placing the elastic member 33 and the first grating 21, etc. which is formed from the silicon wafer between the above, there is no shift in the position of the first grating 21, etc. in the holder 30 within the range of the rise in temperature in a state under normal use of the X-ray Talbot capturing apparatus 1. The present inventors also found that when the receiving unit 31 and the pressing unit 32 of the holder 30 and the grating of the first grating 21, etc. are formed with various material with different thermal expansion coefficients, and the temperature is changed, when the absolute value of the difference between the thermal expansion coefficient of the receiving unit 31 and the pressing unit 32 with respect to the thermal expansion coefficient of the grating of the first grating 21, etc. is within the range of 4×10-6/K, the position of the first grating 21, etc. does not shift within the holder 30 and the moire image Mo can be suitably captured with the X-ray Talbot capturing apparatus 1. According to the findings of the present inventors, in addition to the above configuration 3, the moire image Mo can be suitably captured with the X-ray Talbot capturing apparatus 1 without the position of the first grating 21, etc. shifting in the holder 30 by employing the following configuration. [Configuration 4] As described above, it is effective to process the surface of the receiving surface 31B (see FIG. 8A, FIG. 8B) of the receiving unit 31 of the holder 30 and the pressing surface 32B of the pressing unit 32 (see FIG. 9A, FIG. 9B) in contact with the first grating 21, etc. so that the surfaces easily slide such as processing with alumite or fluorine coating. For example, if such surface processing is not performed, when the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 in contact with the first grating 21, etc., extends in the horizontal direction of the diagram from the state shown in FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B, the first grating 21, etc. is pulled by the receiving unit 31 or the pressing unit 32 and moves in the left direction or the right direction. Since the first grating 21, etc. moves as described above, the position of the first grating 21, etc. is shifted in the holder 30. However, as described above, if the surface is processed so that the surface in contact with the first grating 21, etc. slides easily, even if the temperature rises, and the receiving unit 31 and the pressing unit 32 of the holder 30 in contact with the first grating 21, etc., extends in the horizontal direction of the diagram from the state shown in FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B, the first grating 21, etc. is not pulled by the receiving unit 31 or the pressing unit 32 and does not move and stays in the original position. Therefore, by processing the surface as described above, even if the temperature rises, the position of the first grating 21, etc. shifting in the holder 30 can be prevented, and the moire image Mo can be suitably captured with the X-ray Talbot capturing apparatus 1. [Configuration 5] According to the configuration 1, the elastic member 33 is suitably crushed by the pressing force of the pressing unit 32 of the holder 30 (in FIG. 8A and FIG. 8B) and the pressing force of the receiving unit 31 (in FIG. 9A and FIG. 9B), and the first grating 21 suitably contacts the receiving surface 31B of the receiving unit 31 (in FIG. 8A and FIG. 8B) and the pressing surface 32B of the pressing unit 32 (in FIG. 9A and FIG. 9B) by the surface. The suitable hardness (or flexibility) of the elastic member 33 to realize the above is described above. If the elastic member 33 has suitable hardness (or flexibility), it is known that even if the temperature rises, and the receiving unit 31 and the pressing unit 32 of the holder 30 extends, the elastic member 33 suitably deforms and it is possible to suitably prevent the position of the first grating 21, etc. from shifting in the holder 30. In other words, when the temperature rises, as shown in FIG. 11, the receiving unit 31 and the pressing unit of the holder 30 extends horizontally from the original state (alternate long and short dash line). If the elastic member 33 is too hard (in other words, hard to deform), the first grating 21, etc. may be pulled in the left direction or the right direction of the drawing when the elastic member 33 extends together with the receiving unit 31 and the pressing unit 32, and the position of the first grating 21, etc. may be shifted in the holder 30. However, if the elastic member 33 has a suitable hardness (or flexibility), as shown in FIG. 11, the surface of the elastic member 33 in contact with the pressing unit 32 of the holder 30 (or the receiving unit 31 in FIG. 9A and FIG. 9B), moves horizontally pulled by the pressing unit 32 extending horizontally, and the elastic member 33 is deformed. Since the elastic member 33 is deformed symmetrically horizontally, (that is, for example, the left side portion of the elastic member 33 does not deform larger than the right side portion), the first grating 21, etc. is pulled evenly (in other words, with the same force) in the horizontal direction of the diagram. Therefore, the first grating 21, etc. does not move in the horizontal direction of the diagram. With this, it is possible to prevent the position of the first grating 21, etc. shifting in the holder 30. The present inventors found that through research the hardness demanded from the elastic member 33 in order to prevent the position of the first grating 21, etc. from moving in the holder 30 is preferably A15 or less in the durometer hardness (conforming to International Standard ISO7619). [Configuration 6] As described above, in order to prevent the position of the first grating 21, etc. from shifting in the holder 30, it is preferable that the elastic member 33 deforms flexibly. In order to enable the elastic member 33 to deform easily, for example, the surface of the elastic member 33 in contact with the pressing unit 32 of the holder 30 (or the receiving unit 31 in FIG. 9A and FIG. 9B) has a concave unit 33d in a predetermined shape such as a groove as shown in FIG. 12A or a circle as shown in FIG. 12B. Alternatively, the concave unit formed in a predetermined shape such as a circle as shown in FIG. 12B can be formed as a through hole 33h. Then, as shown in FIG. 12B, the concave unit 33d with the predetermined shape and the hole 33h can be formed regularly or can be formed randomly. In FIG. 12A and FIG. 12B, the groove shaped concave unit 33d, the predetermined shape concave unit 33d and the hole 33h are formed only in a predetermined side (that is, the side parallel to the slit S (see FIG. 6) of the first grating 21, etc.) of the elastic member 33. Alternatively, the above can be provided in all sides of the elastic member 33. According to the above configuration, the elastic member 33 easily deforms due to the concave unit 33d and the hole 33h. Therefore, even if the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 extends, the elastic member 33 suitably deforms, the first grating 21, etc. is pulled evenly, and the first grating 21, etc. does not move. With this, it is possible to accurately prevent the position of the first grating 21, etc. from moving in the holder 30. According to the above configuration, when the hardness of the elastic member 33 is larger than the durometer hardness A15, by accurately forming the concave unit 33d and the hole 33h in the elastic member 33, it is possible to accurately prevent the position of the first grating 21, etc. from moving in the holder 30. [Configuration to Prevent Deforming of the First Grating, Etc. Due to Temperature] For example, when the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 extend from the state shown in FIG. 13A, as shown in FIG. 13B, the first grating 21, etc. held between the receiving unit 31 and the pressing unit 32 may change and the curvature may become smaller than the original state shown in FIG. 13A (in other words, the curvature radius becomes larger). Then, when the curvature of the first grating 21, etc. changes, the radiation does not enter the curved first grating 21, etc. in the normal direction, and the problem of vigletting may occur. In FIG. 13A and FIG. 13B and the later described FIG. 14A and FIG. 14B, the deforming and the bending of the receiving unit 31 and the pressing unit 32 of the holder 30 is emphasized more than the actual state. In order to prevent the curvature of the first grating 21, etc. from changing when the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 extends, the receiving unit 31 can be made from a material including a thermal expansion coefficient larger than the thermal expansion coefficient of the pressing unit. According to the above configuration, when the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 extend from the state shown in FIG. 14A, since the thermal expansion coefficient of the receiving unit 31 is larger than that of the pressing unit 32, the receiving unit 31 sags in a direction separating from the pressing unit 32 as shown in FIG. 14B. Even if the receiving unit 31 sags, the elastic member 33 presses the first grating 21, etc. against the receiving unit 31. Therefore, the curvature of the first grating 21, etc. is the same as the curvature of the sagging receiving unit 31. The thermal expansion coefficient of the receiving unit 31 of the holder 30 and the thermal expansion coefficient of the pressing unit 32 can be suitably adjusted so that the curvature of the receiving unit 31 sagged due to the rise in temperature is the same curvature as the curvature of the receiving unit 31 before the rise in the temperature (or a curvature so that the problem of vigletting does not occur). Therefore, according to the above configuration, since the receiving unit 31 suitably sags even if the temperature rises and the receiving unit 31 and the pressing unit 32 of the holder 30 extend, the curvature of the first grating 21, etc. can be maintained before and after the receiving unit 31 and the pressing unit 32 extend (or the curvature of the first grating etc. can be maintained so that the problem of vigletting does not occur) and it is possible to prevent the problem of vigletting from occurring due to rise in temperature. According to the above described embodiment, the example of the ray source grating 20, the first grating 21, and the second grating 22 formed with the silicon wafer is described. Alternatively, the present invention can be applied when the above gratings are formed from different material. The detailed configuration and operation can be suitably modified without leaving the scope of the present invention.
	claims	1. A method for correcting for proximity heating of resist in an electron beam lithography system, comprising: determining an increase of temperature at a writing point by grouping past pixel values as cells of varying size and using resulting cell values as scalar products with one or more predetermined kernels. 2. A method according to claim 1 , wherein boundaries of said cells are selected such that a temperature contribution from said cells is substantially independent of a distribution of values within the cell. claim 1 3. A method according to claim 1 , wherein cell boundaries are selected such that a grouping of kernel values is substantially symmetric about a correction point. claim 1 4. A method according to claim 1 , wherein cell sizes are selected such that kernel values are approximately equal in value. claim 1 5. A method according to claim 1 , further comprising compensating for the effect of resist heating due to past writing on the exposure of the resist by backscattered electrons associated with the current flash. claim 1 6. A method according to claim 1 , wherein cells include varying, generally greater numbers of pixels as distance from a point of writing increases, which cells may include contiguous or non-contiguous regions of writing. claim 1 7. A system according to claim 1 , wherein said cells are of varying size. claim 1 8. A system, comprising: a lithographic printing machine; and one or more control processors, said one or more processors adapted to compensate for proximity resist heating by applying a kernel of values to one or more cells of pixels to determine a temperature effect of previously written pixels on a current writing pixel for determining the exposure compensation necessary to compensate for the temperature change on the lithographic quality due to earlier writing. 9. A system according to claim 8 , further including one or more memory devices adapted to store determinations of cells such that cells closer to a writing pixel include relatively fewer pixels and cells farther from said writing pixel include relatively more pixels. claim 8 10. A system according to claim 9 , wherein said one or more store kernels determined by approximating a pixel value distribution within said cells with a uniform distribution of values and solving a thermal diffusion equation. claim 9 11. A system according to claim 10 , wherein said applying said kernel further comprises grouping cells to minimize a number of calculations required to apply said kernel by varying the size, shape and contiguity of cells. claim 10 12. A system according to claim 8 , wherein said cells are of varying shape. claim 8 13. A method, comprising: determining a set of kernel values by solving a thermal diffusion equation for a plurality of cells of varying size, said cells comprising groupings of pixels assumed to have a uniform distribution of values within said cells; applying resulting kernel values during writing to a coverage map arranged as said plurality of cells. 14. A method according to claim 13 , comprising determining a cell arrangement by defining a number of bands in a beam-scan direction and varying a size of said cells in a stage-scan direction. claim 13 15. A method according to claim 14 , wherein boundaries of said cells are chosen with reference to a writing point such that said kernel is symmetric and independent of the point of writing. claim 14 16. A method according to claim 13 , wherein cell are generated from bands in the stage scan direction where the band height in the beam scan direction is scaled by the dimensions of electron diffusion in the substrate material. claim 13 17. A method according to claim 13 , wherein cells may be comprised of varying numbers of bands in the beam scan direction when the band cells would have a substantially common kernel value. claim 13 18. A method according to claim 13 , wherein cells may be comprised of groupings of band cells that are non contiguous but which would have a substantially common kernel value. claim 13 19. A method according to claim 18 , further comprising applying a shifted impulse response unction during said determining. claim 18 20. A method according to claim 13 , wherein said cells are of varying shape. claim 13
	description	This application is a U.S. national stage application under 35 U.S.C. §371 of PCT Application No. PCT/US2015/027455, filed Apr. 24, 2015, which claims the benefit of U.S. Provisional Application No. 61/983,606 filed Apr. 24, 2014, the entireties of which are incorporated herein by reference. The present invention relates generally to nuclear fuel containment, and more particularly to a capsule and related method for storing or transporting individual nuclear fuel pins or rods including damaged rods. Reactor pools store used fuel assemblies after removal and discharge from the reactor. The fuel assemblies and individual fuel rods therein may become damaged and compromised during the reactor operations, resulting in cladding defects, breaking, warping, or other damage. The resulting damaged fuel assemblies and rods are placed into the reactor pools upon removal and discharge from the reactor core. Eventually, the damaged fuel assemblies, rods, and/or fuel debris must be removed from the pools, thereby allowing decommissioning of the plants. The storage and transport regulations in many countries do not allow storage or transport of damaged fuel assemblies without encapsulation in a secondary capsule that provides confinement. Due to the high dose rates of used fuel assemblies post discharge, encapsulating fuel assemblies is traditionally done underwater. Furthermore, some countries may require removal of individual damaged fuel rods from the fuel assembly and separate storage in such secondary capsules. Processes already exist for removing single rods from a used fuel assembly and encapsulation. Subsequent drying of damaged fuel after removal from the reactor pool using traditional vacuum drying is exceedingly challenging because water can penetrate through cladding defects and become trapped inside the cladding materials. An improved fuel storage system and method for drying, storing, and transporting damaged fuel rods is desired. A nuclear fuel storage system and related method are provided that facilitates drying and storage of individual fuel rods, which may be used for damaged and intact fuel rods and debris. The system includes a capsule that is configured for holding a plurality of fuel rods, and further for drying the internal cavity of the capsule and fuel rods stored therein using known inert forced gas dehydration (FGD) techniques or other methods prior to long term storage. Existing forced gas dehydration systems and methods that may be used with the present invention can be found in commonly owned U.S. Pat. Nos. 7,096,600, 7,210,247, 8,067,659, 8,266,823, and 7,707,741, which are all incorporated herein by reference in their entireties. In one embodiment, a storage capsule for nuclear fuel rods includes: an elongated body defining a vertical centerline axis, the body comprising an open top end, a bottom end, and sidewalls extending between the top and bottom ends; an internal cavity formed within the body; a lid attached to and closing the top end of the body; and an array of axially extending fuel rod storage tubes disposed in the cavity; wherein each storage tube has a transverse cross section configured and dimensioned to hold no more than one fuel rod. In one embodiment, a fuel storage system for storing nuclear fuel rods includes: an elongated capsule defining a vertical centerline axis, the capsule comprising a top end, a bottom end, and sidewalls extending between the top and bottom ends; an internal cavity formed within the capsule; a lid attached to the top end of the capsule, the lid including an exposed top surface and a bottom surface; an upper tubesheet and a lower tubesheet disposed in the cavity; a plurality of vertically oriented fuel rod storage tubes extending between the upper and lower tubesheets; and a central drain tube extending between the upper and lower tubesheets; wherein each storage tube has a transverse cross section configured and dimensioned to hold no more than one fuel rod. A method for storing nuclear fuel rods is provided. The method includes: providing an elongated vertically oriented capsule including an open top end, a bottom end, and an internal cavity, the capsule further including a plurality of vertically oriented fuel rod storage tubes each having a top end spaced below the top end of the capsule, the storage tubes each having a transverse cross section configured and dimensioned to hold no more than a single fuel rod; inserting a first fuel rod into a first storage tube; inserting a second fuel rod into a second storage tube; attaching a lid to the top end of the capsule; and sealing the lid to the capsule to form a gas tight seal. A method for storing and drying nuclear fuel rods includes: providing an elongated vertically oriented capsule including an open top end, a bottom end, and an internal cavity, the capsule further including a plurality of vertically oriented fuel rod storage tubes each having a top end spaced below the top end of the capsule, the storage tubes each having a transverse cross section configured and dimensioned to hold no more than a single fuel rod; inserting a fuel rod into each of the storage tubes; attaching a lid to the top end of the capsule, the lid including a gas supply flow conduit extending between top and bottom surfaces of the lid and a gas return flow conduit extending between the top and bottom surfaces of the lid; sealing the lid to the capsule to form a gas tight seal; pumping an inert drying gas from a source through the gas supply conduit into the cavity of the capsule; flowing the gas through each of the storage tubes; collecting the gas leaving the storage tubes; and flowing the gas through the gas return conduit back to the source. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. All drawings are schematic and not necessarily to scale. The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by referenced in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls. nuclear fuel assemblies (also referred to as “bundles” in the art) each comprise a plurality of fuel pins or rods mechanically coupled together in an array which is insertable as a unit into a reactor core. The fuel assemblies traditionally have a rectilinear cross-sectional configuration such as square array and contain multiple fuel rods. A reactor core contains multiple such fuel assemblies. The fuel rods are generally cylindrical elongated metal tubular structures formed of materials such as zirconium alloy. The tubes hold a plurality of vertically-stacked cylindrical fuel pellets formed of sintered uranium dioxide. The fuel rod tubes have an external metal cladding formed of corrosion resistant material to prevent degradation of the tube and contamination of the reactor coolant water. The opposite ends of the fuel rod are sealed. FIGS. 1-9B show a damaged nuclear fuel storage system 100 according to the present disclosure. The system includes a vertically elongated fuel rod enclosure capsule 110 configured to hold multiple damaged fuel rods and a closure lid 200 mounted thereto. The lid 200 is configured for coupling and permanent sealing to the capsule 200, as further described herein. Capsule 110 has an elongated and substantially hollow body formed by a plurality of adjoining sidewalls 118 defining an internal cavity 112 that extends from a top end 114 to a bottom end 116 along a vertical centerline axis Cv. The bottom end 116 of the capsule is closed by a wall. The top end 114 of the capsule is open to allow insertion of the damaged rods therein. The sidewalls 118 are sold in structure so that the cavity 112 is only accessible through the open top end 114 before the lid is secured on the capsule. In one embodiment, capsule 110 may have a rectilinear transverse cross-sectional shape such as square which conforms to the shape of a typical fuel assembly. This allows storage of the capsule 110 in the same type of radiation-shielded canister or cask used to store multiple spent fuel assemblies, for example without limitation a multi-purpose canister (MPC) or HI-STAR cask such as those available from Holtec International of Marlton, N.J. Such canisters or casks have an internal basket with an array of rectilinear-shaped openings for holding square-shaped fuel assemblies. It will be appreciated however that other shaped capsules 110 may be used in other embodiments and applications. The body of the capsule 110 may be formed of any suitable preferably corrosion resistant material for longevity and maintenance of structural integrity. In one non-limiting exemplary embodiment, the capsule 110 may be made of stainless steel and have a nominal wall thickness of 6 mm. In certain embodiments, the capsule 110 may further include a laterally enlarged mounting flange 111 disposed at and adjacent to the top end 114, as shown in FIGS. 1-3 and 7-9A. Mounting flange 111 extends laterally outwards from the sidewalls 118 on all sides and vertically downwards from top end 114 along the sidewalls for a short distance. The mounting flange 111 is configured and dimensioned to engage a mounting opening 302 formed in a storage canister 300, thereby supporting the entire weight of a loaded capsule 110 in a vertically cantilevered manner as shown in FIGS. 11-13 and further describe herein. In other embodiments, different methods may be used to support the capsule 110 in the storage canister and mounting flange 111 may be omitted. Referring now particularly to FIGS. 3, 7, 8 and 9A, the capsule 110 further includes an internal basket assembly configured to store and support a plurality of damaged fuel rods. The assembly includes an upper tubesheet 120 and lower tubesheet 122 spaced vertically apart therefrom. The upper and lower tubesheets are horizontally oriented. The lower tubesheet 122 is separated from the interior bottom surface 116a of bottom end 116 of the capsule 110 by a vertical gap to form a bottom flow plenum 124. The upper tubesheet 120 is spaced vertically downwards from the top end 112 of the capsule 110 by a distance D1 sufficient to form a top flow plenum 126 when the closure lid 200 is mounted on the capsule as shown in FIG. 15. Top plenum 126 is therefore formed between the bottom 204 of the lid 200 and top surface 128 of the upper tubesheet 120. Both the bottom and top plenums 124, 126 are part of flow paths used in conjunction with the gas fuel rod drying/dehydration process after the capsule is closed and sealed, as further described herein. A plurality of fuel rod storage tubes 130 are each supported by the upper and lower tubesheets 120, 122 for holding the damaged (i.e. broken and/or leaking) fuel rods. In certain embodiments, intermediate supporting tubesheets or other support elements (not shown) may be used to provide supplementary support and lateral stability to the storage tubes 130 for seismic events. In one embodiment, the storage tubes 130 each have a diameter and internal cavity 131 with a transverse cross section configured and dimensioned to hold no more than a single fuel rod. Accordingly, the tubes 130 extend vertically along and parallel to the vertical centerline axis Cv of the capsule 110 from the upper tubesheet 120 to the lower tubesheet 122. Each of the tubes 130 is accessible through the upper tubesheet 120 (see, e.g. FIG. 9A). In one embodiment, the tubes 130 each have an associated machined lead-in guide in the upper tubesheet 120 to support the insertion of the fuel rods. An annular tapered or chamfered entrance 136 is therefore formed in the upper tubesheet 120 adjacent and proximate to the top open end 132 of each tube 130. The obliquely angled surface (with respect to the vertical centerline axis Cv) of the chamfered entranceways 136 help center and guide loading of the damaged fuel rods into each of the storage tubes 130. The top end 132 of the tubes may therefore be spaced slightly below the top surface 128 of the upper tubesheet 120 as shown. The bottom ends 134 of the fuel rod storage tubes 130 may rest on the bottom interior surface 116a of the capsule 110. Each storage tube 130 includes one or more flow openings 133 of any suitable shape located proximate to the bottom ends 134 of the tubes below the bottom tubesheet 122. The openings 133 allow gas to enter the tubes from the bottom plenum 124 during the forced gas dehydration process and rise upward through the tubes to dry the damaged fuel rods. The fuel rod storage tubes 130 may be mounted in the upper and lower tubesheets 120, 122 by any suitable method. In certain embodiments, the tubes 130 may be rigidly coupled to upper and/or lower tubesheets 120, 122 such as by welding, soldering, explosive tube expansion techniques, etc. In other embodiments, the tubes 130 may be movably coupled to the upper and/or lower tubesheets to allow for thermal expansion when heated by waste heat generated from the decaying fuel rods and heated forced gas dehydration. Accordingly, a number of possible rigid and non-rigid tube mounting scenarios as possible and the invention is not limited by any particular one. The fuel rod storage tubes 130 may be arranged in any suitable pattern so long as the fuel rods may be readily inserted into each tube within the fuel pool. In the non-limiting exemplary embodiment shown, the tubes 130 are circumferentially spaced apart and arranged in a circular array around a central drain tube 150 further described below. Other arrangements and patterns may be used. Referring now to FIGS. 7, 8, 9A, 9B, and 15, the central drain tube 150 of the capsule 110 may be mounted at approximately the geometric center of the upper tubesheet 120 as shown. The center drain tube 150 in one arrangement is supported by and extends vertically parallel to and coaxially with centerline axis Cv of the capsule from the upper tubesheet 120 to the bottom tubesheet 122. The drain tube 150 may be rigidly coupled to the tubesheets 120, 122 using the same techniques described herein for the fuel rod storage tubes. Drain tube 150 is a hollow structure forming a pathway for introducing insert drying gas into the tube assembly to dry the interior of capsule 110 following closure and sealing, as further described herein. The drain tube 150 includes an open top end 151 and an open bottom end 152. The top end functions as a gas inlet and the bottom end functions as a gas outlet, with respect to the dehydration gas flow path further described herein. The bottom end 152 is open into and may extend slightly below the bottom surface of the lower tubesheet 122 to place the drain tube in fluid communication with the bottom plenum 124 of the capsule 110, as shown for example in FIGS. 9A-B. This forms a fluid pathway for introducing drying gas into the bottom of the capsule 110. The outlet end 152 of the drain tube 150 is spaced vertically apart from the interior bottom surface 116a of the capsule 110. Drain tube 150 may include a sealing feature configured to form a substantially gas-tight seal between the closure lid 200 and drain tube for forced gas dehydration process. In one embodiment, the sealing feature may be a spring-biased sealing assembly 140 configured to engage and form a seal with the bottom of the closure lid 200 for gas drying. The sealing assembly 140 includes a short inlet tube 141, an enlarged resilient sealing member 142 disposed on top of the inlet tube, and spring 143. Inlet tube 141 has a length less than the length of the drain tube 150. Spring 143 may be a helical compression spring in one embodiment having a top end engaging the underside 142b of the sealing member 142 which extends laterally (i.e. transverse to vertical centerline axis Cv) and diametrically beyond the inlet tube 141, and a bottom end engaging the top surface 128 of the upper tubesheet 120. The inlet tube 141 is rigidly coupled to the sealing member 142 and has a diameter slightly smaller than the drain tube 150. This allows the lower portion of the inlet tube 141 to be inserted into the upper portion of the drain tube 150 through the top inlet end 151 for upward/downward movement in relation to the drain tube. Spring 143 operates to bias the sealing member 142 and inlet tube 141 assembly into an upward projected inactive position away from the upper tubesheet 120 ready to engage the closure lid 200, as further described herein. Accordingly, the sealing assembly 140 is axially movable along the vertical centerline axis from the upward projected inactive position to a downward active sealing position. In one embodiment, the sealing member 142 may have a circular shape in top plan view and a convexly curved or domed sealing surface 142a in side transverse cross-sectional view (see, e.g. FIGS. 9A and 9B). The curved sealing surface 142a ensures positive sealing engagement with a gas supply outlet extension tube 210 in the capsule closure lid 200 (see FIG. 6) to compensate for irregularities in the extension tube end surface edges and less than exact centering of the extension tube with respect to the sealing member 142, thereby preventing substantial leakage of drying gas when coupled together. The sealing member 142 includes a vertically oriented through-hole 144 to form a fluid pathway through the sealing member to the drain tube 150. In one embodiment, the sealing member 142 may be made of a resiliently deformable elastomeric material suitable for the environment of a radioactive damaged fuel rod storage capsule. The elastomeric seal provides sufficient sealing and a leak-resistant interface between the central drain tube 150 and closure lid 200 to allow the inert drying gas (e.g. helium, nitrogen, etc.) to be pumped down the central drain tube to the bottom of the capsule 110 during the forced gas dehydration process. It will be appreciated that other types of seals and arrangements may be used. Accordingly, in some embodiments metal or composite metal-elastomeric sealing members may be used. The sealing member may also have other configurations or shapes instead of convexly domed, such as a disk shaped with a flat top surface or other shape. In other embodiments, a non-spring activated sealing assembly may be used. Accordingly, the invention is not limited by the material of construction or design of the seal and sealing assembly so long as a relatively gas-tight seal may be formed between the closure lid gas outlet extension tube 210 and the drain tube 150 for forced gas dehydration of the capsule 110. The fuel rod basket assembly, including the foregoing tubesheets, rod storage tubes, central drain tube, and sealing assembly may be made of any suitable preferably corrosion resistant material such as stainless steel. Other appropriate materials may be used. The closure lid 200 will now be further described. Referring to FIGS. 1-6 and 15, lid 200 in one embodiment may have a generally rectilinear cube-shaped body to complement the shape of cavity 112 in capsule 110 in which at least a portion of the lid is received. Accordingly, in one embodiment the lid 200 and capsule 110 may have a square shape in top plan view. Lid 200 further has a substantially solid internal structure except for the gas flow conduits formed therein, as further described below. The lid 200 is formed of a preferably corrosion resistant metal, such as stainless steel. Other materials may be used. Lid 200 includes a top surface 202, bottom surface 204, and lateral sides 206 extending between the top and bottom surfaces. The lateral sides 206 of the lid have a width sized to permit insertion of a majority of the height of the lid into the cavity 112 of the capsule. The bottom of the lid 200 includes a peripheral skirt 212 extending around the perimeter of the bottom surface 204 that engages and rests on the top surface 128 of the upper tubesheet 120 of the capsule 110 when the lid is mounted in the capsule. In one embodiment, the skirt 212 is continuous in structure and extends around the entire perimeter without interruption. The skirt 212 projects downward for a distance from the bottom surface 204 of the lid which is recessed above the bottom edge 212a of the skirt. The forms a downwardly open space 211 having a depth commensurate with the height of the skirt 212. When the bottom edge 212a of skirt 212 rests on top surface 128 of the upper tubesheet 120, the top plenum 126 is formed between the bottom surface 204 of lid 200 and the upper tubesheet inside and within the skirt 212. The bottom edge 212a of the skirt 212 thereby forms a seal between the upper tubesheet 120 and lid 200 for forced gas dehydration of the capsule 110. An enlarged seating flange 208 extends around the entire perimeter of the lid 200 adjacent to top surface 202 and projects laterally beyond the sides 206. The top surface 202 may be recessed below the top edge 208a of the seating flange 208 as shown. A stepped shoulder 213 is formed between seating flange 208 and sides 206 which engages and seats on a mating shoulder 113 formed inside the mounting flange 111 of capsule 110 in cavity 112 (see particularly FIG. 15A). Both mating shoulders 213 and 113 extend around the entire perimeter regions of the lid 200 and capsule 110 respectively and limit the insertion depth of the lid into the capsule. In one embodiment, the top edges 111a and 208a of the mounting flange 111 and seating flange 208 respectively are flush with each other and lie in approximately the same horizontal plane when the closure lid 200 is fully mounted in the capsule 110 (see, e.g. FIGS. 10A, 10B, and 15A). This facilitates formation of an open V-groove weld 205 to hermetically seal the lid to the capsule. The mounting and seating flanges 111, 208 each include opposing beveled faces 115, 208 respectively to form the V-groove. Because of the recessed top surface 202 of the lid 200 and mounting flange 111, access is available to both sides of finished weld which advantageously permits full volumetric inspection of the weld such as by ultrasonic non-destructive testing or other methods. The source and detector of the ultrasonic test (UT) equipment may therefore be placed on opposite sides of the weld for full examination. A multi-pass welding process may be used which prevents any potential through-cracking of a single weld line in the case of an undetected defect. This parallels welding processes used in the United States for Multi-Purpose Canisters (MPCs), but is modified to allow volumetric weld examination (a key consideration for acceptance of weld integrity by some international regulators). Each pass is followed by a Liquid Penetrant Test (LPT) to identify defects in the weld layer as the weld is formed. The finished weld is then volumetrically tested using UT. Unlike a bolted joint sealed with gaskets, a welded joint with volumetric inspection typically does not require leak-monitoring or checks prior to future transport. FIGS. 10A and 10B show the lid 200 and capsule 110 before and after welding, respectively. This does not limit the capsule to having a bolted lid, similar to dual-purpose metal casks used for storage and transport of spent nuclear fuel. In such embodiment, the capsule would have one more seals, for example elastomeric or metallic, that would be compressed during tightening of the lid bolts on the capsule, forming a hermetic seal. According to another aspect of the invention, the closure lid 200 is configured to permit forced gas dehydration of the capsule 110 and plurality of damaged fuel rods contained therein after the lid is seal welded to the capsule. Accordingly, the lid 200 includes a combination of gas ports and internal fluid conduits to form a closed flow loop through capsule 110. Referring now to FIGS. 1-6 and 15, lid 200 includes a gas supply port 220 and gas return port 222 formed in the top surface 202 of the lid, and a gas supply outlet 224 and gas return inlet 226 formed in the bottom surface 204 of the lid. In one configuration, the gas supply outlet 224 and return inlet 226 may be located at diagonally opposite corner regions of the top surface 202 of the lid 200 proximate to the lateral sides 206. The gas supply port 220 is fluidly coupled to the gas supply outlet 224 via an internal flow conduit 228. The gas return port 222 is fluidly coupled to the gas return inlet 226 via another separate internal flow conduit 230 which is fluidly isolated from flow conduit 228. In one embodiment, the flow conduits 228, 230 each follow a torturous multi-directional path through the lid to prevent neutron streaming. In one configuration, flow conduit 228 includes a vertical section 222a connected to gas supply outlet 224, first horizontal section 228b connected thereto, second horizontal section 228c connected thereto, and second vertical section 228d connected thereto and gas supply port 220. The flow conduit sections 228a-d may be arranged in a rectilinear pattern. Flow conduit 228 includes a vertical section 230a connected to gas return port 222, horizontal section 230b connected thereto, and second vertical section 230c connected thereto and gas return inlet 226. The flow conduit sections 230a-c may also be arranged in a rectilinear pattern. Because the lid 200 has a solid internal structure, the flow conduits may be formed by drilling or boring holes through the lateral sides 206 and top and bottom surfaces 202, 204 of the lid to points of intersection between the conduits as best shown in FIGS. 5 and 15. After formation of the flow conduits, the penetrations 232 in the lateral sides 206 of the lid may be closed using threaded and/or seal welded metal caps applied before mounting and welding the lid 200 to the capsule 110. The penetrations 232 in the bottom surface 204 of the lid may remain open. The gas supply and return port penetrations 232 in the top surface 202 of the lid may be threaded and closed using threaded caps 234 to permit removal and installation of remote valve operating assemblies 240 (RVOAs) for forced gas dehydration of the capsule, as shown in FIGS. 14 and 15. It should be noted that the gas supply outlet 224 in lid 200 is fluidly coupled to the gas supply outlet extension tube 210. The extension tube 210 compensates for the height of the lid bottom skirt 212 to allow physical coupling of the tube to the sealing assembly 140 when the skirt rests on the top surface 128 of the upper tubesheet 120. In one embodiment, the extension tube 210 and gas supply outlet 224 are centered on the bottom surface 204 of the lid 200. In certain other embodiments, the extension tube may be omitted and the gas supply outlet 224 penetration may be directly coupled to the sealing assembly 140. A method for storing and drying fuel rods using capsule 110 will now be briefly described. The method may be used for storing intact or damaged fuel rods, either of which may be stored in capsule 110. The process begins with the top of the capsule 110 being open so that the storage tubes 130 are accessible for loading. The loading operation involves inserting the fuel rods into the storage tubes 130. After the capsule is fully loaded, the lid 200 is attached to the top end 114 and sealed to the capsule. In one preferred embodiment, the lid is sealed welded to the capsule as described elsewhere herein to form a gas tight seal After lid 200 is seal welded to the capsule 110, the interior of the capsule and fuel rods therein may be dried using heated forced gas dehydration (FGD) system such as those available from Holtec International of Marlton, N.J. Commonly owned U.S. Pat. Nos. 7,096,600, 7,210,247, 8,067,659, 8,266,823, and 7,707,741, which are all incorporated herein by reference in their entireties, describe such systems and processes as noted above. The remote operated valve assemblies 240 are first installed in the gas supply and gas return ports 220, 222. The valves are then connected to the gas supply and return lines from the FGD system. The next steps, described in further detail herein, include pumping the inert drying gas from the FGD system or source through the gas supply conduit into the cavity 112 of the capsule 110 and into the bottom plenum 124, flowing the gas through each of the storage tubes 130 to dry the fuel rods, collecting the gas leaving the storage tubes in the top plenum 126, and flowing the gas through the gas return conduit back to the FGD source. The process continues for a period of time until analysis of the drying gas shows an acceptable level of moisture removal from the capsule 110. Referring now to FIGS. 5, 9A, 14, and 15, threaded caps 234 may first be removed from the gas supply and return ports 220 and 222 in the lid 200 which is welded to the capsule 110. A remote valve operating assembly 240 is then threadably coupled to each port 220, 222. The gas supply and return lines from the FGD skid which holds the dehydration system equipment are then fluidly coupled to the valve assemblies. The dehydration and drying process is now ready to commence by pumping the inert and heat drying gas from the FGD system through the capsule 110 to dry the fuel rods in the storage tubes 130, as further described herein. Gas supplied from the FGD system first flows through the first valve assembly 240 into the lid 200 through the gas supply port 220. The supply gas then flows through flow conduit 228 to the gas supply outlet 224 and then into gas supply outlet extension tube 210. The supply gas enters the sealing assembly 140 and flows downwards through the central drain tube 150 into the bottom plenum 124 of the capsule 110. The gas in the bottom plenum enters the bottom of the fuel rod storage tubes 120 through openings 133 formed in and proximate to the bottom ends 134 of the tubes. The gas flows and rises upwards through each of the storage tubes 120 to dry the damaged fuel rods stored therein. The gas then enters the top plenum 126 above the upper tubesheet 120 beneath the lid 200. From here, the gas leaves the top plenum and enters the gas return inlet 226 in the lid. The gas flows through flow conduit 230 to the gas return port 222 and into the remote valve operating assembly 240 connected thereto. The return gas then flows through the return line back to the FGD system skid to complete the closed flow loop. Advantageously, the present invention allows drying of multiple damaged fuel rods in the capsule 110 simultaneously instead of on an individual, piece-meal basis. This saves time, money, and operator dosage of radiation. According to another aspect of the invention, the lid 200 includes a threaded lifting port 340 configured for temporary coupling to a lifting assembly 342 that may be used for moving and transporting the capsule 110 around the fuel pool and loading into transport casks or multi-purpose canisters. The lifting assembly 342 in one embodiment may include a lifting rod 344 including a bottom threaded end 346 for rotatable coupling to the threaded lifting port 340 and an opposite top operating end 348 configured for rigging to equipment such as a crane that may be used to lift and maneuver the capsule 110. According to yet another aspect of the invention, a lid-based capsule storage system is provided which is configured for holding and supporting a plurality of capsules 110. The capsule storage system includes a cask loading lid 400 which may be configured to retrofit and replace lids used in existing transport or transfer casks used for loading, storing, and transporting undamaged fuel bundles. Using the temporary lid, the existing casks may used to provide radiation shielding during the capsule 110 drying and closure operations described herein. Referring to FIGS. 11-15, the loading lid 400 can be designed for any dual-purpose metal casks, such as those supplied by Holtec, TNI, or GNS or transfer casks, such as the HI-STRAC used by Holtec International in Marlton, N.J. Loading lid 400 may have multiple mounting cutouts or openings 302 extending completely through the lid each of which are designed to allow insertion of a single capsule 110. The mounting openings 302 are sized smaller than the mounting flange 111 of the capsule 110 so that the flange remains above the top surface 402 of the lid 400. A shoulder 404 is formed beneath each mounting flange 111 between the flange and sidewalls 118 of the capsule which engages the top surface 402 of the lid 400. This allows the capsules to hang from the lid 400 in a vertically cantilevered manner. The top of the capsule 110 therefore sites about 10-15 mm above the lid surface 402 in one representative non-limiting embodiment to enable workers to easily access the top of the capsules to perform the closure operations. The location of the mounting openings 302 can be optimized to allow easy worker access to the capsules during the drying and closure operations. According to another aspect of the invention shown in FIG. 16, a leak testing lid 500 is provided which can be coupled and sealed to the mounting flange 111 of the capsule 110. The lid 500 attached to the mounting flange 111 of capsule 110 and includes a piping connection assembly 502 which allows hook-up to leak testing equipment for performance of an integrated leak test of the entire sealed capsule 110. Although the fuel rod encapsulation capsule is described herein for use with damaged fuel rods, it will be appreciated that the capsule has further applicability for use with intact fuel rods or debris storage as well. Accordingly, the invention is expressly not limited for use with damaged fuel rods alone. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
	summary
062401548	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Using the drawings, the preferred embodiments of the present invention will now be explained. FIG. 2 illustrates a first embodiment of the present invention which is an augmented cooling system for a head lift rig (106). As in FIG. 1, the head lift rig (106) is cooled by a forced air system in which cooled air is forced under pressure into the head lift rig (106) through piping (107). The cooled air moves around and cools the Control Element Drive Mechanism (CEDM) (105) and is expelled through exhaust holes (102). However, as shown in FIG. 2, vents (201) are added to the pipes 107. At the top of each of these vents (201) is a self-actuated louver (202). Each of these louvers (202) includes a series of substantially flat, elongated slats arranged parallel to each other across the opening of the vent (201). Each of the slats is freely rotatable about an axis which runs length-wise along each slat. Consequently, the slats may rotate between a closed position in which they lay flat across the vent (201), their edges overlapping such that the vent (201) is blocked, and an open position in which the slats are disposed perpendicular to their closed position so as to allow air to freely exhaust from the vent (201). As the cooled air is forced through the pipes (107), pressure is created by the forced movement of the cooled air. The slats of the louvers (202) are shaped and weighted to respond to this pressure by remaining in the above-described "closed" position so long as the forced flow of cooled air creates pressure. However, if the flow of forced air through the pipes (107) is discontinued for any reason, the pressure caused by that flow will dissipate. When this occurs, the slats of the louvers (202) will, under the influence of gravity, swing into the open position, thereby allowing hot air from the head lift rig (106) to vent and cooler ambient air to enter the head lift rig (106). The cool ambient air may enter through the exhaust holes (102). Alternatively or additionally, a louver (203) may be incorporated into the head lift rig (106). This louver (203) operates in the same manner as the louvers (202), remaining closed so long as forced air is circulating and automatically opening when the pressure caused by such circulating air is removed. Preferably, additional louvers (204) are added to the chamber (103). These louvers may be self-actuated louvers as well, which remain closed so long as the flow of air is maintained. However, when allowed to fall open, the louvers (204) allow cooler ambient air to flow directly into the chamber (103). This air is then heated by the heat in the chamber (103) and rises to escape through louver (203) or the upper louvers (202). This circulation allows the heat in chamber (103) to be quickly dissipated. A second embodiment of the present invention is illustrated in FIG. 3. The system of FIG. 3 is similar to that of FIG. 2. However, instead of the louvers (202), flap valve louvers (301) are used to regulate the vents (201). The flap valve louvers (301) rotate between a first position (301A) and a second position (301B). During normal operation of the cooling system, refrigerated air is forced under pressure through the pipes (107) the pressure of this moving air forces the flap valve louvers (301) into the first position (301A) and holds the louvers (301) in this position. In the first position (301A), the louvers (301) block the vents (201). Should the flow of air be discontinued for any reason, there will be no pressure holding the flap valve louvers (301) in the first position (301A). Under the influence of gravity, the louvers (301) will then fall to the second position (301B). In the second position (301B), the louvers (301) allow hot air from the head lift rig (106) to exhaust out the vents (201) and cooler ambient air to enter the head lift rig (106). The cool ambient air may enter through the exhaust holes (102). As shown in FIG. 3, this embodiment of the invention may also include the louver (203) in the head lift rig (106). However, the louver (203) need not be used, leaving the flap valve louvers (301) to provide ventilation for the head lift rig (106). The preceding description has been presented only to illustrate and describe the invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. The preferred embodiment was chosen and described in order to best explain the principles of the invention and its practical application. The preceding description is intended to enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims.
048797367	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 an x-ray examination installation constructed in accordance with the principles of the present invention includes a stand 1 consisting of a column or pedestal 2 to which an arm 3 for a C-shaped carrier 4 is attached. An x-ray tube 5 is mounted at one free end of the carrier 4, and an x-ray image intensifier 6 is mounted at the opposite end. The x-ray tube 5 has a central ray 7 centered on the x-ray image intensifier 6. A patient support table 8, on which a patient 9 is disposed, is situated between the x-ray tube 5 and the x-ray image intensifier 6. The x-ray image intensifier 6 carriers an x-ray film changer 11 via a holder 10. A carriage 12 is connected to the holder 10, which permits the x-ray film changer 11 to be displaced by approximately 90.degree. from an exposure position 11d (shown in dashed lines) to a standby position (shown in solid lines). Such displacement can be undertaken, for example, by drive rollers 14, 15 and 16 entrained by a belt 13, one of the rollers being driven by a motor 17. In the view shown in FIG. 1, the motor 17 is disposed behind the roller 14. As shown in FIG. 2, the holder 10 surrounds the x-ray image intensifier 6, and permits the x-ray film changer 11 to be displaced to a standby position at any one of locations 11a, 11b or 11c, the latter position being shown in dashed lines. Such movement ensues as indicated by the curved arrows. As shown in FIG. 3, the holder 10 includes a bearing 18. The inner bearing race 19 in a the form of a ring, is rigidly connected to the x-ray image intensifier 6. The outer bearing race 20, also in the form of a ring, is rotatably seated around the inner race 19. The inner and outer bearing races 19 and 20 are relatively moveable via a bearing medium 21 (schematically indicated by a solid line) which may be, for example, rollers or a slip surface. As can also be seen in FIG. 3, the carriage 12 is integrated with the outer bearing race 20, so that the carriage 12 is also displaced when the film changer 11 is moved around the inner bearing race 20. The x-ray film changer 11 is manually displaceable to various standby positions by a handle 22. A spring-loaded pin 23 is provided for locking the x-ray film changer into anyone of positions 11aa, 11b or 11c shown in FIG. 2. The pin 23 engages one of the recesses 24, 25 or 26 provided in the inner bearing race 19, dependent on the desired position. If a right brachial catheterization is to be undertaken on the patient 9, the operator swivels the x-ray film changer 11 to the position 11a shown in FIG. 2, so that the pin 23 engages the recess 24. The physician can then conduct the examination without being impeded by the x-ray film changer 11, located at its standby position at the opposite side. For a left brachial catheterization, the x-ray film changer 11 is swiveled to the position llc shown in FIG. 2, so that the pin 23 engages the recess 26. If it is necessary to have access to the patient from both longitudinal sides of the support table 8 the film changer is brought to the position 11b, so that the pin 23 engages the recess 25. Given a cranial or caudal rotation of the x-ray image intensifier 6, or of the x-ray source 5, appropriate rotational movements can bring the x-ray film changer 11 to a standby position at which it does not impede the range of motion of the image intensifier 6. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonable and properly come within the scope of their contribution to the art.
	description	This is a continuation, under 35 U.S.C. §120, of copending international application PCT/EP 2004/006946, filed Jun. 25, 2004, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. 103 28 774.4, filed Jun. 25, 2003; the prior applications are herewith incorporated by reference in their entirety. The invention lies in the field of nuclear engineering. More specifically, the invention relates to a nuclear technology plant having a containment to which a pressure relief line is connected. It also relates to a method for the pressure relief of such a plant. In a nuclear power station, in case of incident or accident situations, depending on the incident in question and countermeasures instigated where appropriate, for example inerting the containment atmosphere, account must be taken of a possibly significant pressure increase inside the containment. In order to avoid structural damage possibly resulting from this to the containment per se, or system components arranged in it, nuclear power stations may be designed for contingent pressure relief of the containment by releasing the containment atmosphere (venting). To this end, a pressure relief line is conventionally connected to the containment of a nuclear technology plant. Such containments conventionally have low leakage rates of for example <0.1%/d, so that only very minor discharges to the environment take place via leaks, even in such accident situations. Other containments however, for example the Russian design of the type WWER 440, have significant sealing defects of for example 20-100 wt. % per day, so that the described positive pressure venting technique cannot be employed owing to the permanently unfiltered leaks. The containment atmosphere usually contains radioactive material however, for example noble gases, iodine or aerosol, which could reach the environment of the nuclear power station in the case of venting. Particularly in case of comparatively serious incidents with core meltdown possibly occurring, airborne activity quantities (aerosols) inside the containment could occur in particularly high concentrations so that release of significant quantities of such aerosols or activity quantities into the environment of the nuclear technology plant could take place in the presence of large sealing defects or if unacceptable positive pressure situations arise. Such airborne activities could cause land contamination lasting a comparatively long time, in particular owing to the long half-lives of possibly entrained components such as iodine or cesium isotopes. In order to avoid this, the pressure relief systems intended for venting the containment atmosphere are conventionally provided with filtering or activity retention devices, which are intended to prevent airborne activity quantities entrained in the containment atmosphere from being released to the environment. To this end, for example, European patent EP 0 285 845 B1 and U.S. Pat. No. 4,873,050 discloses a concept for the pressure relief of a nuclear power station, in which a venturi scrubber provided as a filter to retain airborne activities and a throttle device are connected in series into a pressure relief line connected to the containment of the nuclear power station. The venturi scrubber comprises a number of venturi tubes arranged in a scrubbing liquid held in a container, to which the gas stream conveyed in the pressure relief line can be applied. The venturi tubes respectively comprise a constriction designed similarly as a nozzle, at which the gas stream flowing through is accelerated to a particularly high flow rate. Entry openings for the scrubbing liquid are provided in the region of this constriction, the scrubbing liquid which enters being carried along by the gas stream flowing through. Fragmentation of the scrubbing liquid takes place owing to the comparatively high flow rate of the gas stream at this point, airborne activities or aerosols entrained in the gas stream being incorporated into the liquid droplets resulting from this. By subsequent droplet separation from the gas stream, it is therefore possible to remove a large part of the entrained aerosols or airborne activities. In the system described in EP 0 285 845 B1 and U.S. Pat. No. 4,873,050, the throttle device connected in series with the venturi scrubber is designed for operation with so-called critical expansion. The pressure conditions in the line system in the case of critical expansion, i.e. in particular the pressure drop across the throttle device, are set up so that the medium flowing in the line flows through the throttle device at the speed of sound. In case of intervention, i.e. in the event of pressure relief of the containment, this effect is used in the system according to EP 0 285 845 B1 and U.S. Pat. No. 4,873,050 in order to set up a volume throughput in the pressure relief line which is constant as a function of time. In nuclear technology plants whose containment has serious sealing defects owing to its design, however, significant airborne activities could enter the environment precisely in the event of comparatively long-lasting incident scenarios. In order to allow the safe continued operation of such plants, it is therefore desirable that the safety standard internationally required for nuclear technology plants should be complied with for such plants as well. It is accordingly an object of the invention to provide a nuclear plant and a pressure relief method for a nuclear plant which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and in which even very fine airborne activities or aerosols can be retained with a particularly high reliability in the venturi scrubber in the event of pressure relief, even if there are design-related sealing defects of the containment, so that release to the environment is precluded with a particularly high reliability. It is also an object to provide a method for the pressure relief of such a nuclear technology plant. With the foregoing and other objects in view there is provided, in accordance with the invention, a nuclear plant, comprising: a containment; a pressure relief line communicating with said containment; a blower device and a venturi scrubber connected in series in said pressure relief line, said venturi scrubber being disposed in a container with a scrubbing liquid; said blower device and said venturi scrubber being dimensioned to establish in said venturi scrubber, in an operating state of said blower device, a flow velocity of a medium conveyed in said pressure relief line of more than 130 m/s and preferably even more than 180 m/s. In other words, the objects of the invention are achieved in that a blower device and a venturi scrubber, arranged in a container with a scrubbing liquid, are connected in series into the pressure relief line, the blower device and the venturi scrubber being dimensioned so that a flow rate of the medium conveyed in the pressure relief line of more than 130 m/s, preferably more than 180 m/s, is set up in the venturi scrubber in the operating state of the blower device. The invention is based on the consideration that in order to separate airborne activities or aerosols in a venturi scrubber or a venturi tube by feeding water into the tube interior, a comparatively fine droplet mist is produced owing to the flow conditions prevailing there, the airborne activities or aerosols to be separated being incorporated into such droplets so that they can be removed with them from the gas stream. A particularly high separating effect can therefore be achieved, even for very fine aerosols, by keeping the probability particularly high that the aerosols will strike suitable water droplets and be incorporated into them. As has been surprisingly found, precisely with venturi tubes in which the scrubbing liquid can be fed into the tube interior in the manner of a passive design using the negative pressure prevailing at the constriction and therefore without external drive means, the striking and inclusion probability of even very fine aerosols in the droplet mist increases to a significant super-proportional degree, so that with very high flow rates of the gas stream in the venturi tube it is possible to achieve separation rates of more than 99.9% for mixed aerosols with a particle size of about 1 μm and of 98% or more for comparatively fine aerosols with a particle size of less than 0.5 μm in the scrubbing liquid. The pressure relief and activity retention system of the nuclear technology plant is therefore designed to sustain such high flow rates in case of pressure relief. In order to ensure such a high separation rate in each phase of a possible incident precisely in view of the characteristic parameters, for example plant pressure, possibly changing to a large degree over the full course of the incident in the event of a serious incident scenario, and therefore to prevent release of contaminating components into the environment to the greatest possible degree in each phase of an incident, the pressure relief and activity retention system of the nuclear technology plant is furthermore designed for such a high separation factor almost independently of gas and vapor quantities produced in the containment of the nuclear technology plant. In order to ensure this, the flow conditions intended according to design are to be set up in the venturi scrubber by generating high pressures in an upstream high-performance blower. The blower device used for this is preferably designed as a high-performance radial fan with a rated speed of more than 10,000 rpm and a pressure of at least 200 mbar, preferably more than 500 mbar. The venturi scrubber preferably comprises a multiplicity of venturi tubes. They may designed as so-called short venturi tubes, the outlets of which are arranged below the intended setpoint level of the scrubbing liquid so that the venturi tubes are immersed essentially fully in the scrubbing liquid. Preferably, however, a comparatively large number of the venturi tubes are designed as so-called long venturi tubes, the outlets of which are arranged above the intended setpoint level of the scrubbing liquid. Gas deviation for centrifugal drop separation is preferably provided in this case. By venturi nozzle tubes blowing out primarily above the scrubbing liquid, in particular because of the low gas density at atmospheric operation and the concomitant large volume flows, the water ejection determining the component size can be kept small and a particularly high idle tube speed can be set in the venturi scrubber device. The consequences are a significantly smaller venturi scrubber diameter and a smaller component height, as well as correspondingly reduced consumption of scrubbing liquid. Owing to the compact structure which this allows for the scrubber device, it is possible to design the high-pressure fan and scrubber as well as the fiber filter with a molecular sieve in merely two modules, for example in a so-called “skid-mounted” design, even with a very high extraction power of for example more than 10,000 m2/h to 30,000 m2/h. This leads to a significant reduction of the production and assembly outlay, because the machine and control technology equipment of the completed device, including optimization, acceptance tests etc. can already be carried out in the factory. The freely programmable digital control and E-engineering used can likewise already be tested and optimized in the factory. In order furthermore to prevent sedimentation in the region of the container, which could lead to increased servicing and maintenance requirements, the venturi scrubber in another preferred configuration is designed for comparatively intense turbulence and circulation of the scrubbing liquid in the operational case. To this end a small proportion of the venturi tubes, preferably up to about 10%, are arranged with an outlet direction directed downward inside the container and below the setpoint level of the scrubbing liquid. It has been found particularly favorable for ensuring high separation rates to set a comparatively high water load in the venturi scrubber, for example more than 5 liters, preferably more than 10 liters, of scrubbing liquid per cubic meter of gas. This is because precisely the combination of such high water loads with the high flow rates intended according to design favor reliable separation to a particular degree. In order to ensure this, the venturi tubes in another preferred configuration have an annular slot feed with an aperture angle of from 20° to 85°, preferably from 30° to 45°, extending over the nozzle circumference. For such a high water load, the venturi tubes of the venturi scrubber furthermore preferably have respectively a ratio of their throat cross-sectional area to the entry area for the scrubbing liquid of less than 10:1, preferably about 3:1. The throat cross-sectional area in this case indicates the cross-sectional area through which the flow medium can flow freely at the constriction inside the respective venturi tube. In a particularly preferred configuration, the venturi tubes of the venturi scrubber are designed so as to ensure passive scrubbing liquid intake and distribution, due to the negative pressure generated by the medium flowing through, as far as the core jet region in the interior of the venturi tube. To this end, the venturi tubes of the venturi scrubber are preferably designed as round or substantially round venturi tubes with a throat width of less than about 80 mm, preferably less than about 40 mm, or as flat or substantially flat venturi tubes with a throat width of less than about 100 mm. In addition or as an alternative, the venturi tubes of the venturi scrubber preferably have a height to throat width ratio of more than 20, preferably more than 50. A particularly compact design for the pressure relief and activity retention system assigned to the nuclear, technology plant, with correspondingly reduced production and assembly outlay, can be achieved in that the container equipped with the venturi scrubber is connected to a further scrubbing liquid reservoir on the scrubbing liquid side. The amount of scrubbing liquid held in the container itself can therefore be kept comparatively small and in case of need, i.e. particularly when consumption of scrubbing liquid takes place, a contingent top up from the further scrubbing fluid store may be provided. The (in this sense) inactive, comparatively large scrubbing liquid reservoir may in this case be held in a separate storage container and used, in particular, to replace evaporated scrubbing liquid. The filling level in the container may be adjusted passively by arranging the further scrubbing liquid reservoir at the same geodetic height or with a filling level float control. Further water reservoirs which are in any case already provided, for example wastewater containers, deionate supply or the like, may in particular also be used as a further scrubbing liquid reservoir, in which case the contingent additional feed of scrubbing water into the container may take place via gradients or by means of diaphragm pumps. Particularly effective activity retention can be achieved in that the pressure relief and activity retention system assigned to the nuclear technology plant is designed, in a particularly preferred configuration, for contingent recirculation of the airborne activities or aerosols separated in the scrubbing liquid into the containment. To this end, in a particularly preferred configuration, the container provided with the venturi scrubber is connected via a feedback line to the interior of the containment on the scrubbing liquid side. Using such a configuration, in case of need, i.e. in particular constantly or at cyclic intervals, some or all of the scrubbing liquid laden with activities or aerosols removed from the gas stream may be moved into the containment so that the overall activity requiring treatment remains reliably in the containment. In particular, the scrubbing liquid in the container may in this case be topped up from the further scrubbing liquid reservoir. Such recirculation or feedback of the activities can keep the overall activity quantity and concentration contained in the scrubbing liquid particularly low so that, for example, resuspension effects leading to activity extraction in the downstream filter devices can also be kept particularly low. In particular, this favors comparatively long-term venting operation over several days and weeks, without the subsequent metal fiber filter recleaning device being overloaded by resuspension aerosols and without the iodine separation at the iodine sorption filter being overloaded by iodine resuspension. Precisely by using the venturi tubes, direct gas cooling is achieved for the gas superheated by heat of decay and heat of compression, which allows feedback to the intake side—avoiding further coolers/cooling circuits—and the negative pressure in the container can thus be regulated simply. A molecular sieve, for example coated with silver nitrate or other silver compounds etc. is preferably provided in a bypass of the main stream—designed for a sub-stream of less than 50% of the design throughput—for effective organoiodine separation in long-term operation of the retention system. The superheating of the gas stream before entering the molecular sieve may be carried out electrically or by means of a heat exchanger, arranged in the line between the high-pressure fan and the scrubber. This allows passive and straightforward superheating, and the heat of compression introduced can be removed from the process at the relevant parts, so that less scrubbing liquid is evaporated and further component reduction can therefore be carried out. Continuous decontamination of the influx point of aerosol and iodine activities, and reduction of the heat of compression, can be carried out by spraying process liquid in on the intake side of the high-performance blower. For multiblock plants, for example, this provides the economically very favorable possibility of a central common activity retention device with externalized connecting lines to the various plants, without massive shielding measures being necessary. Significant improvement of the activity retention and a guarantee of long-term operation can therefore be achieved, particularly in the case of iodine and aerosols. By feeding back or recirculating the activities separated in the venturi scrubber, the heat of decay incurred via the aerosols or airborne activities is furthermore kept away from the container and can be moved back into the containment so that the possible burdens resulting from this in the container, for example due to liquid evaporation, can be kept particularly small. Precisely the avoidance of scrubbing liquid evaporation which can be achieved by this leads overall, i.e. also taking into account possible top ups of scrubbing liquid into the container, to an overall reduced demand for scrubbing liquid. In order to keep the required number of feed-throughs, which are designed with a view to significant safety requirements, through the containment of the nuclear technology plant particularly small, the feedback line in a further preferred configuration is then connected via the pressure relief line to the interior of the containment. The recirculation or feedback then takes place by jet feeding into the central region of the pressure relief line, so that transfer of the activity-laden scrubbing liquid into the containment can take place in counter flow with the pressure relief gas stream. The activity-laden scrubbing liquid is preferably sent back continuously or discontinuously via a separate containment feed-through of small diameter, or discontinuously by temporarily generating an increased negative pressure in the containment and briefly interrupting the intake and feedback through the same feed-through by means of jet injection and c>10 m/s—with a slow pressure rise—but maintenance of a negative pressure. The negative pressure may in this case be increased cyclically. In order then to allow feedback in the manner of a fully passive system, the container in a further preferred configuration is geodetically arranged lying at least about 5 m, preferably at least 10 m, higher than the exit point of the pressure relief line from the containment. Feedback of the activity-laden scrubbing liquid through the pressure relief line into the containment is therefore possible merely owing to the geodetic pressure in the water column between the pressure relief line and the container, so that jet feedback can be carried out in counter flow with the gas stream without further active assistance. Particularly high operational safety can be achieved in that the electrical power supply of the system components of the pressure relief and activity retention system, i.e. in particular the blower device or the controls assigned to it, is constructed independently of the nuclear technology plant so that reliable pressure relief is ensured even in case of incident. In case of need, the blower device may for example be supplied via a nuclear power block not affected by the incident or via a mobile diesel unit with a generator. Particularly favorable flow conditions in the venturi scrubber are ensured in that the blower device is designed to produce a suitably selected pressure gradient, preferably a slight negative pressure of for example less than 5 mbar in the interior of the containment and a positive pressure of about 500 mbar on the pressure side of the blower device. For particularly reliable activity retention overall, a separator system preferably comprising a centrifugal drop separator and/or a fiber separator, preferably with fibers >50 μm, in particular with decreasing fiber thicknesses, is connected downstream of the venturi scrubber in the pressure relief line. As an alternative or in addition, a metal fiber filter with a fiber thickness of up to 5 μm, preferably of stainless steel fibers or sintered filter fibers with pore or fiber diameters of less than 5 μm, is preferably connected downstream of the venturi scrubber in the pressure relief line. Precisely this ensures that even the minor quantity of fine aerosols <0.5 μm possibly penetrating can still be substantially retained. The filter elements are preferably made of stainless steel fibers. The fine filtering may also be carried out with sintered filter fibers having pore diameters <2 μm. The scrubbing liquid is preferably designed to a particular degree for effective retention of iodine and iodine compounds. To this end, the container preferably contains a scrubbing liquid with a pH of at least 9, this pH being obtained for example by adding NaOH, other alkalis and/or sodium thiosulfate. The addition of these chemicals to the scrubbing liquid may preferably be carried out by intake via a jet pump lying in a freshwater stream from a separate chemical container in order to set a concentration of from 0.5 to 5 percent by weight in the scrubbing liquid. Activity reduction and cooling of the reactor core by energy extraction is expediently furthermore simultaneously achieved by an additional direct feed of cold water fully or partially via the retention device into the reactor pressure vessel region, in counter flow with the vent gas, by means of existing systems as simple emergency measures, for example by means of a firefighting pump or via other systems. By high feed quantities with a rising filling level in the containment particularly in the early accident phase, a further advantageous reduction of the vapor-gas mixture to be extracted can thereby be achieved, and therefore also a reduction of the dimensions of the retention device or extraction device. With respect to the method for pressure relief of a nuclear technology plant of the type mentioned, the object is achieved in that a flow rate of the medium conveyed in the pressure relief line of more than 130 m/s, preferably more than 180 m/s, is applied to the venturi scrubber. The advantages achieved by the invention are, in particular, that by the deliberate combination of the venturi scrubber with the upstream blower unit and by a suitable design of these components, it is possible to ensure that a particularly high flow rate of the pressure relief gas stream flows through the venturi scrubber essentially throughout the course of an incident. In any event, this ensures a particularly high separating effect of more than 99.5%, preferably >99.9% of the entrained airborne activities or aerosols, in particular also taking into account the fine aerosol fraction with a particle size of <0.5 μm, so that quantitative retention in the liquid phase is achieved and an overall retention effect of from >99.99% to >99.999% is achieved in long-term operation without overloading the downstream metal filter unit, so that release of activities into the environment is avoided particularly reliably. The pressure relief and activity retention system formed by the venturi scrubber and the upstream blower unit automatically ensures reliable flow through the venturi scrubber in almost all phases of an incident, active atmosphere extraction from the containment also being ensured with a correspondingly high-performance blower unit. Precisely in nuclear technology plants with comparatively high leaks or sealing defects in the containment owing to their design, the blower device can therefore be used in the manner of a twofold function in order to pump off the containment atmosphere gas resulting from serious incidents—while maintaining a negative pressure in the containment—and feeding the activities in the liquid phase back into the containment, so that reliable operation without burdening the environment can be carried out even with such untight containments in case of need. The method and the devices are preferably used so that the gases or vapors, including their leaks, produced by the residual heat released in accident situations with core meltdown, can be completely extracted and cleaned almost fully with respect to airborne activities before release to the environment. The retained activities are furthermore fed back into the containment in the short term. Owing to the constant volume flow applied to the venturis, the high-pressure blower furthermore achieves a uniformly high venturi velocity without requiring elaborate height staggering of venturi tubes for partial load coverage. The combination of the high-speed venturi scrubber device with feedback, combined with the downstream metal fiber filters, can ensure an overall separation factor of from >99.99% to >99.999% even in long-term operation, independently of the aerosol concentration in the containment. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a nuclear technology plant and method for the pressure relief of a nuclear technology plant, 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 drawing figures in detail and first, particularly, to FIG. 1 thereof, there is shown a nuclear plant 1 (also: nuclear engineering installation, nuclear technology plant) with a containment 2, which contains nuclear components intended for generating electricity and other system components. In order to be able to reliably prevent structural damage or instabilities of the containment 2 even in case of a comparatively serious incident, in which case it is necessary to take into account a strong pressure rise inside the containment 2 due to processes taking place inside the containment 2, the nuclear technology plant 1 is equipped with a pressure relief and activity retention system 4 connected to the containment 2. In case of need, this allows rational and controlled release of the containment atmosphere, also referred to as venting, from the containment 2 into its environment. The pressure relief and activity retention system 4 comprises a pressure relief line 6, connected to the containment 2, which is connected to a vent 8 on the outlet side. In order to avoid contaminating the environment of the nuclear technology plant 1 in the case of venting or release of the containment atmosphere, the pressure relief and activity retention system 4 is also designed for reliable retention of airborne activities and aerosols contained in the containment atmosphere. To this end, the pressure relief and activity retention system 4 comprises a wet scrubber 10 intended as a filter device for such airborne activities or aerosols. For its part, the wet scrubber 10 comprises a venturi scrubber 12 which is connected to the pressure relief line 6 and is arranged in a container 14 with a scrubbing liquid W. The venturi scrubber 12 comprises a plurality of venturi tubes 16, which open with their outlets 18 into a gas space 22 lying above the setpoint level 20 of the scrubbing liquid W in the container 14. The gas space 22 is for its part connected on the output side to a further subsection of the pressure relief line 6, which is connected via a filter device 26 to the vent 8. For its part, the filter device 26 comprises a metal fiber filter 28, an intermediate throttle 30 and subsequently a molecular sieve 32. The metal fiber filter 28 is in this case designed particularly as a fine filter with fiber filter mats with a fiber diameter decreasing from 50 μm to approximately 1 μm so that, in particular, even fine aerosols penetrating with a particle size of less than 0.5 μm can be effectively retained. The pressure relief and activity retention system 4 of the nuclear technology plant 1 is designed for particularly reliable activity retention and, in particular, for a retention factor of 98% or more even for comparatively fine-grained aerosols with a particle size of less than 0.5 μm. To this end, and for reliable active atmosphere extraction from the containment 2 in case of need, a high-power blower device 34, also referred to as a turbo-blower, is connected upstream of the venturi scrubber 12 in the pressure relief line 6. As a design goal, this is based on the pressure relief gas flow flowing through the venturi scrubber 12 with a particularly high flow rate of more than 150 m/s, in particular more than 200 m/s in case of intervention. This is because as it has been found, with such high flow rates it is possible to achieve a virtually immediate rise in the separation rate, even fine and very fine aerosol particles in particular being incorporated into the scrubbing liquid droplets and therefore separated. Suitable selection particularly of the flow cross sections and the power of the blower device 34 in this case ensures that there is such a high flow rate in the venturi scrubber 12 in virtually all the phases of an incident scenario. In order to ensure correspondingly high system leaktightness, for example, the blower shaft feed-through is additionally designed with a barrier gas seal which is permanently applied. The effect achieved by this is also that the atmosphere is pumped actively out of the containment 2 through the blower device 34 in case of intervention, so that release of containment atmosphere to the environment is reliably avoided even if there are leaks or sealing defects of the containment 2. For safety reasons, the power supply of the blower device 34 is in this case independent of the nuclear technology plant 1. As an alternative in the case of multiblock plants, a redundant power supply may also be provided for the blower device 34, in which case the blower device 34 can be supplied via a power station block respectively unaffected by the incident in case of need. The power supply is therefore constructed separately, i.e. also independently of the existing switching station and control technology. Another design criterion is furthermore to select the power of the blower device 34 so that, taking into account the gases and vapor quantities produced and their possible sealing defects and leaks incurred during incidents in the core region, a small negative pressure of for example less than 5 mbar in the interior of the containment 2 and a positive pressure of about 500 mbar on the pressure side of the blower device 34 is set up in case of use. As can be seen in the enlarged representation according to FIG. 2, the venturi scrubber 12 comprises a multiplicity of venturi tubes 16. The venturi tubes 16 are in this case fed on the gas stream side from a common supply system 40 connected on the input side to the pressure relief line 6. A comparatively large proportion of the venturi tubes 16 are formed as so-called long venturi tubes, which are arranged with their outlets 18 above the intended setpoint level 20 of the scrubbing liquid W and therefore open directly into the gas space 22 in the manner of a “free blowing” arrangement. Provision is furthermore made to prevent contamination or damage of the operating behavior of the venturi scrubber 12 due to accumulation or sedimentation, in that a comparatively small proportion, i.e. less than 10%, of the venturi tubes 16 are directed obliquely downward. This venturi cyclone achieves intense circulation of the scrubbing liquid W inside the container 14, so that sedimentation is reliably prevented. In particular the venturi tubes 16 designed as long venturi tubes are designed for a comparatively high water load of the gas stream requiring treatment, i.e. more than 5 and in particular more than 10 liters of scrubbing liquid W per cubic meter of gas. To this end, an annular slot feed around the nozzle circumference at an aperture angle of from 30° to 45° is provided in the venturi tubes 16 in the entry region 42 for the scrubbing liquid W. The dimensioning is in this case carried out so that the ratio of the throat cross-sectional area, determined at the constriction 44 or so-called throat of each venturi tube 16, to an entry surface determined at the annular slot feed for the scrubbing liquid W is about 3:1. The constriction 44 is furthermore the point at which the gas stream flowing through has its maximum flow rate; the flow rate to be taken into account for the design and adaptation of the venturi scrubber 12 is consequently also determined at the constriction 44. In the exemplary embodiment, the venturi tubes 16 designed as long venturi tubes are configured as round venturi tubes with a throat width of less than 40 mm, so that feeding of the scrubbing liquid W as far as the core jet region in the interior of the venturi tube 16 is ensured with passive scrubbing liquid intake and distribution, due to the negative pressure generated by the medium flowing through. The venturi tubes 16 furthermore have a height to throat width ratio of more than 50. As can furthermore be seen from FIG. 1, multicomponent storage of the scrubbing liquid W is provided in order to allow a particularly compact design of the container 14. On the one hand, the container 14 contains scrubbing liquid W in which the venturi scrubber 12 is arranged. In addition and as a supplement to this, the container 14 is furthermore connected on the scrubbing liquid side via a feed line 48 to a further scrubbing liquid reservoir 50. The scrubbing liquid reservoir 50 may be a vessel specially designed for this, which is chosen to lie at a geodetically suitable height for reliable topping up of scrubbing liquid W into the container 14, in which case the setpoint level 20 of the scrubbing liquid W in the container 14 is adjusted by the height set in the further scrubbing liquid reservoir 50 for the scrubbing liquid W held in it. As an alternative, a water tank which is in any case provided, for example a wastewater container, a deionate supply or the like may also be provided as a further scrubbing liquid reservoir 50, in which case the contingent topping up of scrubbing water W into the container 14 may take place via suitably selected gradients or by, for example, means of diaphragm pumps or compressed air. The container 14 is furthermore connected on the scrubbing liquid side via a feedback line 52 with throughput limitation and an overflow line to the interior of the containment 2. This makes it possible to feed scrubbing liquid W laden with airborne activities or with aerosols back from the container 14 into the containment 2 in the manner of recirculation or feedback. The activity as a whole can therefore be kept particularly reliably inside the containment 2 by constant or cyclic recirculation of such laden scrubbing liquid W, so that the risk of output into the environment is kept particularly low. Precisely by such recirculation of the scrubbing liquid W, moreover, the heat of decay imported via the retained activities can consequently be moved back from the container 14 into the containment 2, so that the evaporation of scrubbing liquid W in the container 14 is kept particularly low. Despite the recirculation of scrubbing liquid W into the interior of the containment 2 and topping up of scrubbing liquid W from the further scrubbing liquid reservoir 50, the consumption of scrubbing liquid W overall can therefore be kept particularly low because evaporation is avoided. As indicated by the dashed line 54, the feedback line 52 may be connected via the pressure relief line 6 to the interior of the containment 2. As represented in the detail enlargement in FIG. 3, the recirculation is carried out in the manner of a passive configuration in counter flow with the gas stream emerging from the containment 2, no additional feed-through being required through the containment 2. In order to ensure a sufficient feed pressure for the scrubbing liquid W to be fed back, the container 14 in the exemplary embodiment with the scrubbing liquid W contained in it is arranged at a sufficient geodetic height, i.e. about 10 m above the exit point 56 of the pressure relief line 6 from the containment 2. Merely by the geodetic pressure in the water column in the feedback line 52, a sufficient feedback pressure for the scrubbing liquid W into the containment 2 is therefore ensured in the manner of a passive system. As an alternative, cyclic feedback could be provided by closing the outlet valve with a positive pressure in the containment or using a separate small line with a low subcritical cross section and corresponding application of pumps, for example a compressed air diaphragm pump or a rotary pump supplied from a gas store independent of the power supply. The components necessary for this, for example a compressed air reservoir 58 and a diaphragm valve controlled by its own medium, are schematically represented in FIG. 1. For reliable iodine retention, the pH in the scrubbing liquid W in the container 14 is adjusted to an alkaline value, in particular a value of more than 9. To this end, contingent addition of NaOH, other alkalis and/or sodium thiosulfate at from >0.5 to 5 wt. % is carried out by intake via a jet pump lying in the freshwater stream.
047160071	claims	1. A spectral shift pressurized-water reactor comprising: a pressure vessel enclosing a reactor core which includes fissile material fuel, said pressure vessel having an inlet and an outlet for circulating water coolant moderator in heat transfer relationship with said core, said core comprising a plurality of square-shaped adjacent fuel assemblies vertically disposed therein for generating heat by nuclear fission, and said fuel assemblies having a fuel enrichment which provides a measure of excess reactivity at the beginning of core life which is later drawn upon to lengthen core life; a plurality of spaced vertical guide tubes disposed in each of said fuel assemblies and adapted to have rod members vertically moved therein and therefrom during reactor operation, and a portion of said guide tubes in each said fuel assembly disposed in a cross-like configuration along the two diagonals which connect the corners of said square-shaped fuel assemblies; three separate types of rods adapted to be moved into and out of said guide tubes, a first type of said rods comprising neutron-absorbing control rods which are movable into and out of said core so that movement of said control rods into said core will substantially decrease reactivity and withdrawal of said control rods from said core will substantially increase reactivity, a second type of said rods comprising neutron-spectral-shift displacer rods which have a substantially lower absorptivity for neutrons than said control rods, each said neutron-spectral-shift displacer rod comprising a hollow thin-walled Zircaloy member containing a filling of solid or annular zirconium- or aluminum-containing material for providing internal support and mass for said thin-walled tubular member, each said displacer rod having overall neutron-absorbing and -moderating characteristics essentially not exceeding those of hollow tubular Zircaloy members with or without a filling of zirconium oxide pellets or aluminum oxide pellets, the third type of said rods comprising thick walled gray rods each of which have an absorptivity for neutrons intermediate that of each of said control rods and each of said neutron-spectral-shift displacer rods, and said rods all having substantially the same cross-sectional dimension; said gray rods and said control rods operable to be moved into and out of said core in a portion of said guide tubes which are positioned in said cross-like configuration, and said neutron-spectral-shift displacer rods operable to be moved into and out of substantially all of the remainder of said guide tubes, approximately half of said fuel assemblies operable to have only said neutron-spectral-shift displacer rods moved therein and therefrom, those of said fuel assemblies into which only said neutron-spectral-shift displacer rods are to be moved being alternated in position in said core with those of said fuel assemblies into which said control rods and said gray rods are to be moved, the total number of said neutron-spectral-shift displacer rods very substantially exceeding the total number of said control rods and said gray rods, and the total number of said control rods substantially exceeding the total number of said gray rods; spider members and associated shafts and drive members therefor positioned above said core, a separate spider member provided for substantially all of each of said fuel assemblies, each of said spider members being separately controllable and having only one type of said rods connected thereto in the form of a rod cluster, said control rods and said gray rods being connected to said spider members in the form of control-rod and gray-rod cross-like clusters to move into said guide tubes which are similarly disposed, and said neutron-spectral-shift displacer rods connected to said spider members as composite clusters which interfit into substantially all said guide tubes in a single fuel assembly in addition to those proximate guide tubes of adjacently positioned fuel assemblies so that those spiders which have said displacer rod clusters connected thereto serve one fuel assembly in addition to proximate portions of those fuel assemblies which are positioned adjacent thereto; and each said neutron-spectral-shift displacer rod cluster having a total reactivity worth when fully inserted into said core, each said gray rod cluster having a total reactivity worth when fully inserted into said core, and the total reactivity worth of each said neutron-spectral-shift displacer rod cluster substantially exceeding the total reactivity worth of each said gray rod cross-like cluster so that during reactor operation predetermined reactivity worths can be obtained by movement of said displacer rod clusters and said gray rod clusters. a pressure vessel enclosing a reactor core which includes fissile material fuel, said pressure vessel having an inlet and an outlet for circulating water coolant moderator in heat transfer relationship with said core, said core comprising a plurality of square-shaped adjacent fuel assemblies vertically disposed therein for generating heat by nuclear fission, and said fuel assemblies having a fuel enrichment which provides a measure of excess reactivity at the beginning of core life which is later drawn upon to lengthen core life; a plurality of spaced vertical guide tubes disposed in each of said fuel assemblies and adapted to have rod members vertically moved therein and therefrom during reactor operation, and a portion of said guide tubes in each said fuel assembly disposed in a cross-like configuration along the two diagonals which connect the corners of said square-shaped fuel assemblies; three separate types of rods adapted to be moved into and out of said guide tubes, a first type of said rods comprising neutron-absorbing control rods which are movable into and out of said core so that movement of said control rods into said core will substantially decrease reactivity and withdrawal of said control rods from said core will substantially increase reactivity, a second type of said rods comprising neutron-spectral-shift displacer rods which have a substantially lower absorptivity for neutrons than said control rods, each said neutron-spectral-shift displacer rod comprising a hollow thin-walled Zircaloy member containing a filling of solid or annular zirconium- or aluminum-containing material for providing internal support and mass for said thin-walled tubular member, each said displacer rod having overall neutron-absorbing and -moderating characteristics essentially not exceeding those of hollow tubular Zircaloy members with or without a filling of zirconium oxide pellets or aluminum oxide pellets, the third type of said rods comprising thick walled gray rods each of which have an absorptivity for neutrons intermediate that of each of said control rods and each of said neutron-spectral-shift displacer rods, said control rods and said neutron-sepctral-shift displacer rods and said gray rods when fully inserted into said core displacing an equivalent volume of water, and the volume of said water coolant moderator displaced by said neutron-spectral-shift displacer rods when fully inserted into said core very substantially exceeding the volume of said water coolant moderator which is displaced by said control rods and said gray rods if fully inserted into said core; said gray rods and said control rods operable to be moved into and out of said core in a portion of said guide tubes which are positioned in said cross-like configuration, and said neutron-spectral-shift displacer rods operable to be moved into and of substantially all of the remainder of said guide tubes, approximately half of said fuel assemblies operable to have only said neutron-spectral-shift displacer rods moved therein and therefrom, those of said fuel assemblies into which only said neutron-spectral-shift displacer rods are to be moved being alternated in position in said core with those of said fuel assemblies into which said control rods and said gray rods are to be moved, and the volume of said water coolant moderator displaced by said control rods if fully inserted into said core substantially exceeding the volume of said water coolant moderator displaced by said gray rods when fully inserted into said core; spider members and associated shafts and drive members therefor positioned above said core, a separate spider member provided for substantially all of each of said fuel assemblies, each of said spider members having only one type of said rods connected thereto in the form of a rod cluster, said control rods and said gray rods being connected to said spider members in the form of control-rod and gray-rod cross-like clusters to move into said guide tubes which are similarly disposed, and said neutron-spectral-shift displacer rods connected to said spider members as composite clusters which interfit into substantially all said guide tube in a single fuel assembly in addition to those proximate guide tubes of adjacently positioned fuel assemblies so that those spiders which have said neutron-spectral-shift displacer rod clusters connected thereto serve one fuel assembly in addition to proximate portions of those fuel assemblies which are positioned adjacent thereto; and each said neutron-spectral-shift displacer rod cluster having a total reactivity worth when fully inserted into said core, each said gray rod cluster having a total reactivity worth when fully inserted into said core, and the total reactivity worth of each said neutron-spectral-shift displacer rod cluster substantially exceeding the total reactivity worth of each said gray rod cross-like cluster so that during reactor operation predetermined reactivity worths can be obtained by movement of said displacer rod clusters and said gray rod clusters. 2. The reactor as specified in claim 1, wherein the substantial majority of said fuel assemblies which have only displacer rods movable therein and therefrom are surrounded by four adjacent fuel assemblies, and those of said spiders and associated shafts and drives which serve said fuel assemblies which have only displacer rods movable therein also control the movement of displacer rods into the proximate guide tubes of said four adjacent fuel assemblies. 3. The reactor as specified in claim 1, wherein said reactor has chemical shim control capability. 4. The reactor as specified in claim 1, wherein the total reactivity worth of each said displacer rod cluster is approximately four times the total reactivity worth of each said gray rod cluster. 5. A spectral shift pressurized-water reactor comprising: 6. The method as specified in claim 5 wherein said gray rods comprise material having an overall neutron absorptivity approximating that of hollow heavy walled stainless steel tubes.
048790877	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear power plant, and more particularly to a nuclear power plant suitably employing a nuclear reactor in which the core flow-rate is controlled by feed water. 2. Statement of the Related Art At present, reduction in construction expenses is a major task in a nuclear power plant. With respect to a boiling water reactor (hereafter referred to as the BWR power plant), for instance, development is under way of a new type of power plant which is provided with internal pumps. In this new type of power plant, since a recirculation system used in an existing BWR power plant is not required, the overall size of a reactor container becomes compact. However, it is desirable to make the reactor container even more compact. Examples in which the reactor container can be made compact are disclosed, though not directly referred to therein, in Japanese Patent Examined Publication No. 43-23117 (U.S. patent Ser. No. 497,787; application date: Oct. 19, 1965) and Japanese Patent Examined Publication No. 49-16920 (U.S. Pat. No. 3,621,926). In a BWR power plant disclosed in Japanese Patent Examined Publication No. 43-23117, a portion of the feed water is supplied to a reactor pressure vessel via a feed water sparger, while the remaining portion of the feed water is used as the driving water for jet pumps so as to supply cooling water to the core. The feed water introduced into the feed water sparger is used for controlling the water level in the reactor pressure vessel. Furthermore, in this BWR power plant, the cooling water discharged from the feed water sparger and the cooling water separated by a steam separator above the core (the two kinds of cooling water are in a mixed state) is cooled by the feed water used as the jet pump driving water, and is subsequently sucked into jet pumps. The cooling of the jet pump suction water by this heat exchanger is aimed at preventing the occurrence of cavitation in the jet pumps due to the boiling of the cooling water in the jet pumps. Japanese Patent Examined Publication No. 49-16920 discloses a BWR power plant which has jet pumps using as their driving water the cooling water discharged from a recirculation pipe and jet pumps using as their driving water a portion of the feed water, the remaining portion of the feed water being supplied from the feed water sparger into the reactor pressure vessel. In this publication as well, it is disclosed (column 6, lines 37-44) that the cooling water which is sucked from the feed water sparger into the jet pumps through an annular descending flow passage is cooled, as in the case of Japanese Patent Examined Publication No. 43-23117. Each of the foregoing examples of the prior art is arranged such that a heat exchanger is installed in a reactor pressure vessel, and the cooling water sucked into the jet pumps is cooled by the jet pump driving water, i.e., part of the feed water, by using this heat exchanger. However, the temperature difference between the cooling water sucked into the jet pumps and the jet pump driving water, both being allowed to flow into the heat exchanger, in the order of 5.degree.-60.degree. C., which the flow rate at the side, of the heat exchanger, to be cooled is 10 times as much as the flow rate at cooling side thereof. For this reason, the heat exchange efficiency of the cooling water sucked into the jet pumps and the jet pump driving water is very poor, so that the temperature of the cooling water sucked into the jet pumps does not decline appreciably. Accordingly, in these conventional examples, the range which makes it possible to prevent the occurrence of cavitation in the jet pumps is narrow, so that a reactor output through the core flow-rate control cannot be altered substantially. In particular, it is difficult to effect a load following operation in the conventional examples. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a nuclear power plant which is capable of simplifying the structure of a nuclear reactor. Another object of the present invention is to provide a nuclear power plant which is capable of preventing the occurrence of cavitation in jet pumps and of substantially altering a reactor power through core flow-rate control. Still another object of the present invention is to provide a nuclear power plant which is capable of preventing a decline in the water level of a reactor during a trip. A further object of the present invention is to provide a nuclear power plant which is capable of altering outputs with small amplitude and short cycles. A characteristic feature of the present invention lies in that there is provided feed water supplying means for introducing a portion of the feed water into jet pumps in a reactor container as driving water and introducing the remaining portion of the feed water into a feed water sparger in the reactor container at a temperature lower than that of the portion of the feed water introduced into the jet pumps. In accordance with the present invention, since it is not necessary to install in a reactor container a heat exchanger for heating the feed water used as the driving water for the jet pumps, the structure of the reactor can be simplified.
053965345	claims	1. A shutter apparatus for collimating x-rays comprising: a frame defining an opening with first and second opposing interior edges; an elongated flexible band extending in slidable engagement about at least a portion of said opening in said frame; drive means for translating said flexible band relative to said frame; a first shutter member made of an x-ray opaque material having a first end attached to said flexible band along said first interior edge; and a second shutter member made of an x-ray opaque material having a first end attached to said flexible band along said second interior edge. a frame defining an opening with first and second opposing interior edges, said frame further having: an elongated flexible band extending in slidable engagement in said interior channel of said frame; drive means for translating said flexible band relative to said frame; a first shutter member made of an x-ray opaque material having a first end extending through said first slot and attached to said flexible band within said interior channel of said frame, and a second end for slidably engaging said second track; and a second shutter member made of an x-ray opaque material having a first end extending through said second slot and attached to said flexible band within said interior channel of said frame, and a second end for slidably engaging said first track. a frame defining an opening substantially orthogonal to a predetermined axis with first and second opposing interior edges; an elongated flexible band extending in slidable engagement about at least a portion of said opening; drive means for translating said flexible band relative to said frame; a first shutter member made of an x-ray opaque material having a first end attached to said flexible band along said first interior edge; and a second shutter member made of an x-ray opaque material having a first end attached to said flexible band along said second interior edge; wherein said first shutter assembly and said second shutter assembly are oriented substantially orthogonally to one another. 2. The shutter apparatus of claim 1, wherein said first and second interior edges of said frame further comprise track means, said first shutter member further comprises a second end for slidably engaging said track means of said second interior edge, and said second shutter member further comprises a second end for slidably engaging said track means of said first interior edge. 3. The shutter apparatus of claim 1, wherein said frame has a channel extending around at least a portion of the periphery of said opening to hold said elongated flexible band. 4. The shutter apparatus of claim 1, wherein said first end of said first shutter member is attached to said elongated flexible band through a first slot in said first edge of said frame, and said first end of said second shutter member is attached to said elongated flexible band through a second slot in said second edge of said frame, whereby said slots define a maximum range of motion for said shutter members within said opening. 5. The shutter apparatus of claim 1, wherein said drive means comprises a stepper motor. 6. The shutter apparatus of claim 1, wherein said elongated flexible band comprises a thin strip of plastic. 7. The shutter apparatus of claim 1, wherein said frame has a substantially rectangular opening. 8. A shutter apparatus for collimating x-rays comprising: 9. The shutter apparatus of claim 8, wherein said drive means comprises a stepper motor. 10. The shutter apparatus of claim 8, wherein said elongated flexible band comprises a thin strip of plastic. 11. The shutter apparatus of claim 8, wherein said first and second slots define a maximum range of motion for said shutter members within said frame opening. 12. The shutter apparatus of claim 8, wherein said frame has a substantially rectangular opening. 13. A shutter apparatus for collimating x-rays comprising a first shutter assembly and a second shutter assembly, each of said shutter assemblies having: 14. The shutter apparatus of claim 13, wherein said first and second interior edges of said frame further comprise track means, said first shutter member further comprises a second end for slidably engaging said track means of said second interior edge, and said second shutter member further comprises a second end for slidably engaging said track means of said first interior edge. 15. The shutter apparatus of claim 13, wherein said frame further comprises a channel extending around at least a portion of the periphery of said opening to hold said elongated flexible band. 16. The shutter apparatus of claim 13, wherein said first end of said first shutter member is attached to said elongated flexible band through a first slot in said first edge of said frame, and said first end of said second shutter member is attached to said elongated flexible band through a second slot in said second edge of said frame, whereby said slots define a maximum range of motion for said shutter members within said opening. 17. The shutter apparatus of claim 13, wherein said drive means comprises a stepper motor. 18. The shutter apparatus of claim 13, wherein said elongated flexible band comprises a thin strip of plastic. 19. The shutter apparatus of claim 13, wherein said frame has a substantially rectangular opening.
051529572	claims	1. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly, the fuel assembly having clearances among fuel elements; a body fixing section for fixing the body to the fuel assembly for positioning; a recovering working unit for recovering foreign matter; a fiberscope for photographing a working state of the recovering working unit and sending a corresponding image to a remote location; a moving mechanism section for moving the recovering working unit and the fiberscope in one direction and in a direction toward or away from the fuel assembly, allowing the recovering working unit and the fiberscope to be operated in cooperation with each other, the recovering working unit adapted to be guided into the clearances of the fuel assembly, the fiberscope following the recovering working unit; and a remote control section for remotely controlling the operations of the moving mechanism and the recovering working unit on the basis of the image to recover the foreign matter. 2. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a moving mechanism section movable both in one direction and in a direction toward or away from the fuel assembly; a recovering working unit adapted to be moved by the moving mechanism section to gain access to clearances among fuel elements of the fuel assembly to allow foreign matter to be recovered thereby, wherein said recovering working unit is comprised of a needle-like probe; a fiberscope for following the movement of the recovering working unit, while covering the recovering working unit and foreign matter within a viewing field, to photograph a working state of the recovering working unit and to send a corresponding image to a remote location; and a remote control section for remotely controlling the operations of the moving mechanism and recovering working unit on the basis of the image to recover the foreign matter. 3. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly, wherein said body is equipped with a water stream generation section for imparting a propulsion force to the body; a body fixing section for fixing the body to the fuel assembly for positioning; a moving mechanism section movable both in one direction and in a direction toward or away from the fuel assembly; a recovering working unit adapted to be moved by the moving mechanism section to gain access to clearances among fuel elements of the fuel assembly to allow foreign matter to be recovered thereby; a fiberscope for following the movement of the recovering working unit, while covering the recovering working unit and foreign matter within a viewing field, to photograph a working state of the recovering working unit and to send a corresponding image to a remote location; and a remote control section for remotely controlling the operations of the moving mechanism and recovering working unit on the basis of the image to recover the foreign matter. 4. The foreign matter recovering apparatus according to claim 3, wherein said water stream generation section is comprised of a screw propeller and a rudder is provided for adjusting the attitude of said body. 5. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a moving mechanism section movable both in one direction and in a direction toward or away from the fuel assembly; a recovering working unit adapted to be moved by the moving mechanism section to gain access to clearances among fuel elements of the fuel assembly to allow foreign matter to be recovered thereby, wherein said recovering working unit includes a suction nozzle for sucking the foreign matter and a recovery case for recovering the sucked foreign matter; a fiberscope for following the movement of the recovering working unit, while covering the recovering working unit and foreign matter within a viewing field, to photograph a working state of the recovering working unit and to send a corresponding image to a remote location; and a remote control section for remotely controlling the operations of the moving mechanism and recovering working unit on the basis of the image to recover the foreign matter. 6. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a moving mechanism section movable both in one direction and in a direction toward or away from the fuel assembly; a recovering working unit adapted to be moved by the moving mechanism section to gain access to clearances among fuel elements of the fuel assembly to allow foreign matter to be recovered thereby; a fiberscope for following the movement of the recovering working unit, while covering the recovering working unit and foreign matter within a viewing field, to photograph a working state of the recovering working unit and to send a corresponding image to a remote location; and a remote control section for remotely controlling the operations of the moving mechanism and recovering working unit on the basis of the image to recover the foreign matter, wherein said remote control section includes an operation panel having a plurality of joysticks and a display unit for displaying the state of working by the working unit. 7. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a recovering working unit for gaining access to clearances among fuel elements of the fuel assembly and recovering the foreign matter; a fiberscope for recovering the recovering working unit and foreign matter and photographing a state of working by the recovering working; a positioning mechanism section for moving the recovering working unit and fiberscope, as one unit, in a plurality of directions for positioning; a display unit for displaying an image, photographed by the fiberscope, at a remote location; a remote control section for performing a remote control on the basis of the image displayed on the display unit; and a control section for controlling the positioning mechanism section and recovering working unit on the basis of an output of the remote control section. 8. The foreign matter recovering apparatus according to claim 7, wherein said body fixing section is comprised of a guide for guiding the fuel assembly and clamps for holding the fuel assembly therebetween. 9. The foreign matter recovering apparatus according to claim 7, wherein said recovering working unit is comprised of forceps. 10. The foreign matter recovering apparatus according to claim 7, wherein said body includes a water stream generation section for imparting a propulsion force to the body. 11. The foreign matter recovering apparatus according to claim 1 or 7, further comprising a fiberscope oscillation mechanism for swinging the fiberscope and adjusting the direction of its optical end face. 12. A foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a working unit for gaining access to clearances among fuel elements of the fuel assembly and recovering a foreign matter there; a fiberscope for covering the recovering working unit and foreign matter and photographing a state of working by the recovering working unit; positioning mechanism section for moving the working unit and fiberscope, as one unit, in a plurality of directions for positioning; a display unit for displaying an image, photographed by the fiberscope, at a remote location; a remote control section for performing a remote control operation on the basis of an image displayed on the display unit; a control unit for controlling the positioning mechanism and recovering working unit on the basis of an output of the remote control section; and a movement restriction section for preventing the recovering working unit from being moved toward the fuel assembly when it is incorrectly displaced relative to very small clearances of the fuel assembly and allowing the recovering working unit to be moved toward the fuel assembly when the recovering working unit is correctly oriented toward the clearance of the fuel assembly to allow it to gain access to the small clearance of the fuel assembly. 13. The foreign matter recovering apparatus according to claim 12, wherein said movement restriction section comprises an engaging projection adapted to, together with the working unit, be displaced as one unit in accordance with a movement of the recovering working unit in a predetermined direction; and a guide member provided integral with the body and having a guide recess which is so set as to have a positional relation to the clearances of the fuel assembly, said guide member being engaged by the engaging projection when the recovering working unit is moved toward the fuel assembly while being incorrectly displaced relative to the very small clearances of the fuel assembly, and being retracted back into the guide recess, upon the movement of the recovering working unit in a direction to correctly align with the small clearance of the fuel assembly, to enable the engaging projection to be moved along the guide recess. 14. The foreign matter recovering apparatus according to claim 12, wherein said movement restriction section is comprised of a guide member provided with the body and having a guide recess provided in a positional relation corresponding to the very small clearances of the fuel assembly and a plurality of proximity sensors which, together with the recovering working unit, are displaced as one unit in accordance with the movement of the working unit in a predetermined direction to detect the position of the guide recess; a position detection section is provided for detecting the position of the recovering working unit when the recovering working unit is spaced apart from the fuel assembly with the working unit placed outside the clearances of the fuel assembly; and said control unit controls the positioning mechanism section and recovering working unit in accordance with the outputs of the remote control section, proximity sensors and position detection section. 15. The foreign-matter recovering apparatus according to claim 14, wherein said position detection section includes a fixing section representing the position of the fuel assembly and a movable body for detecting the position of the clearances of the fuel assembly in a manner to follow the movement of the recovering working unit. 16. The foreign matter recovering apparatus according to claim 14, further comprising a limit sensor for restricting a spacing between the recovering working unit and the fuel assembly when the working unit is retracted back from the fuel assembly.
	summary
050154222	abstract	Making uranium dioxide pellets of controlled grain size by treating 50-500 g/l UO.sub.2 F.sub.2 with NH.sub.3 in a first and a second stages to form (NH.sub.4).sub.2 U.sub.2 O.sub.7 precipitate, wherein the NH.sub.3 /U molar ratio is between 3-5 in the first stage and between 6-12 in the second stage. The precipitate is then formed into UO.sub.2 pellets having grain size within the range from 10 to 100 .mu.m.
	summary
	abstract	A Radiation tolerant camera, including a camera module and having an electronic image sensor. The camera module is arranged in a radiation shielding enclosure, the enclosure having an opening for allowing passage of light into the image sensor. Furthermore, the camera module is connected to a heat absorbing cooling element dissipating heat from the camera module.
	claims	1. A computer infrastructure comprising:a computing device including:a system for managing a set of computing devices in the computer infrastructure that evaluate a trustworthiness of one another, the system for managing including: a system for managing membership in a sub-group of the computer infrastructure and a system for managing a trust level for communications between another computing device in the computer infrastructure and other computing devices;wherein the system for managing membership in the sub-group of the computer infrastructure includes:a system for detecting that a threshold number of computing devices has been exceeded for at least one of: the computer infrastructure or a sub-group of the computer infrastructure; anda system for dividing the at least one of: the computer infrastructure or the sub-group of the computer infrastructure into a plurality of sub-groups of computing devices for evaluating trust. 2. The computer infrastructure of claim 1, the computing device further including a system for providing device measurements for the computing device for processing by another computing device in the computer infrastructure. 3. The computer infrastructure of claim 1, the computing device further including a system for evaluating another computing device in the computer infrastructure based on a set of device measurements for the another computing device and a set of reference measurements. 4. The computer infrastructure of claim 1, the system for dividing assigning at least one computing device in the computer infrastructure to a plurality of sub-groups. 5. The computer infrastructure of claim 1, wherein the threshold number is selected based on an impact of the monitoring on a performance of a primary function of each computing device. 6. The computer infrastructure of claim 1, the system for managing membership in a sub-group of the computer infrastructure including:a system for detecting that a number of computing devices in a sub-group of the computer infrastructure has fallen below a threshold number; anda system for reassigning each computing device in the sub-group to a new sub-group. 7. The computer infrastructure of claim 6, wherein the new sub-group includes at least one computing device that is included in at least one additional sub-group. 8. The computer infrastructure of claim 1, wherein the system for managing a trust level for communications between another computing device in the set of computing devices and other computing devices isolates a particular computing device from communicating with other computing devices in response to a failure of the particular computing device. 9. A computer infrastructure comprising:a computing device including:a system for managing a set of computing devices in the computer infrastructure that evaluate a trustworthiness of one another, the system for managing including a system for managing membership in a sub-group of the computer infrastructure; wherein the system for managing membership in the sub-group of the computer infrastructure includes:a system for detecting that a threshold number of computing devices has been exceeded for at least one of: the computer infrastructure or a sub-group of the computer infrastructure; anda system for dividing the at least one of: the computer infrastructure or the sub-group of the computer infrastructure into a plurality of sub-groups of computing devices for evaluating trust. 10. The computer infrastructure of claim 9, the system for managing a set of computing devices further including a system for managing a trust level for communications between another computing device in the computer infrastructure and other computing devices. 11. The computer infrastructure of claim 9, the system for dividing assigning at least one computing device in the computer infrastructure to a plurality of sub-groups. 12. The computer infrastructure of claim 9, wherein the threshold number is selected based on an impact of the monitoring on a performance of a primary function of each computing device. 13. The computer infrastructure of claim 9, the system for managing membership in a sub-group of the computer infrastructure including:a system for detecting that a number of computing devices in a sub-group of the computer infrastructure has fallen below a threshold number; anda system for reassigning each computing device in the sub-group to a new sub-group. 14. The computer infrastructure of claim 13, wherein the new sub-group includes at least one computing device that is included in at least one additional sub-group. 15. A computer infrastructure comprising:a computing device including:a system for managing a set of computing devices in the computer infrastructure that evaluate a trustworthiness of one another, the system for managing including a system for managing a trust level for communications between another computing device in the computer infrastructure and other computing devices, wherein the system for managing the trust level for communications between another computing device in the set of computing devices and other computing devices isolates a particular computing device from communicating with other computing devices in response to a failure of the particular computing device. 16. The computer infrastructure of claim 15, the system for managing a set of computing devices further including a system for enabling a user to modify a set of reference measurements used to determine a corresponding trust level for a computing device. 17. The computer infrastructure of claim 15, the system for managing a set of computing devices further including a system for communicating an updated set of reference measurements to other computing devices in the computer infrastructure.
	abstract	A plasma source is provided. The plasma source includes a chamber body inside which plasma is generated, a first mirror magnet, a second mirror magnet, and a cusp magnet provided around the chamber body and spaced apart in a axial direction thereof, each comprising permanent magnets radially spaced apart from each other to form spaces between adjacent permanent magnets thereof; and a cooling medium flow passage provided in the spaces that passes a cooling medium for cooling the chamber body.
	abstract	Disclosed is a measuring apparatus for measuring the position, size and/or shape of a light convergent point of an EUV light source. In one preferred form, the apparatus includes a light receiving device for receiving EUV light diverging from a light convergent point, an optical system for directing the EUV light toward the light receiving device, a light blocking member disposed in a portion of light path for the EUV light and having a plurality of openings, and a system for detecting a spatial distribution of the EUV light at the light convergent point, on the basis of reception of EUV light by the light receiving device. In another preferred from, the apparatus includes a light receiving device for receiving EUV light diverging from a light convergent point, a gas filter disposed in a portion of a light path of the EUV light and being filled with a predetermined gas, and a system for detecting a spatial distribution of the EUV light at the light convergent point, on the basis of the reception of EUV light by the light receiving device.
	description	This application is a continuation of U.S. patent application Ser. No. 11/695,532, filed Apr. 2, 2007, which is a continuation of U.S. patent application Ser. No. 10/917,023, filed Aug. 12, 2004, now U.S. Pat. No. 7,199,382, issued Apr. 3, 2007, which claims the benefit of the U.S. Provisional Application No. 60/494,699, filed Aug. 12, 2003 and U.S. Provisional Application No. 60/579,095 filed Jun. 10, 2004 both entitled “Precision Patient Alignment and Beam Therapy System”. This invention was made with United States Government support under the DAMD17-99-1-9477 and DAMD17-02-1-0205 grants awarded by the Department of Defense. The Government has certain rights in the invention. 1. Field of the Invention The invention relates to the field of radiation therapy systems. One embodiment includes an alignment system with an external measurement system and local feedback to improve accuracy of patient registration and positioning and to compensate for misalignment caused by factors such as mechanical movement tolerances and non-strictly rigid structures. 2. Description of the Related Art Radiation therapy systems are known and used to provide treatment to patients suffering a wide variety of conditions. Radiation therapy is typically used to kill or inhibit the growth of undesired tissue, such as cancerous tissue. A determined quantity of high-energy electromagnetic radiation and/or high-energy particles is directed into the undesired tissue with the goal of damaging the undesired tissue while reducing unintentional damage to desired or healthy tissue through which the radiation passes on its path to the undesired tissue. Proton therapy has emerged as a particularly efficacious treatment for a variety of conditions. In proton therapy, positively charged proton subatomic particles are accelerated, collimated into a tightly focused beam, and directed towards a designated target region within the patient. Protons exhibit less lateral dispersion upon impact with patient tissue than electromagnetic radiation or low mass electron charged particles and can thus be more precisely aimed and delivered along a beam axis. Also, upon impact with patient tissue, the accelerated protons pass through the proximal tissue with relatively low energy transfer and then exhibit a characteristic Bragg peak wherein a significant portion of the kinetic energy of the accelerated mass is deposited within a relatively narrow penetration depth range within the patient. This offers the significant advantage of reducing delivery of energy from the accelerated proton particles to healthy tissue interposed between the target region and the delivery nozzle of a proton therapy machine as well as to “downrange” tissue lying beyond the designated target region. Depending on the indications for a particular patient and their condition, delivery of the therapeutic proton beam may preferably take place from a plurality of directions in multiple treatment fractions to achieve a total dose delivered to the target region while reducing collateral exposure of interposed desired/healthy tissue. Thus, a radiation therapy system, such as a proton beam therapy system, typically has provision for positioning and aligning a patient with respect to a proton beam in multiple orientations. In order to determine a preferred aiming point for the proton beam within the patient, the typical procedure has been to perform a computed tomography (CT) scan in an initial planning or prescription stage from which multiple digitally reconstructed radiographs (DRRs) can be determined. The DRRs synthetically represent the three dimensional data representative of the internal physiological structure of the patient obtained from the CT scan in two dimensional views considered from multiple orientations and thus can function as a target image of the tissue to be irradiated. A desired target isocenter corresponding to the tissue to which therapy is to be provided is designated. The spatial location of the target isocenter can be referenced with respect to physiological structure of the patient (monuments) as indicated in the target image. Upon subsequent setup for delivery of the radiation therapy, a radiographic image is taken of the patient, such as a known x-ray image, and this radiographic image is compared or registered with the target image with respect to the designated target isocenter. The patient's position is adjusted to, as closely as possible or within a given tolerance, align the target isocenter in a desired pose with respect to the radiation beam as indicated by the physician's prescription. The desired pose is frequently chosen as that of the initial planning or prescription scan. In order to reduce misalignment of the radiation beam with respect to the desired target isocenter to achieve the desired therapeutic benefit and reduce undesired irradiation of other tissue, it will be appreciated that accuracy of placement of the patient with respect to the beam nozzle is important to achieve these goals. In particular, the target isocenter is to be positioned translationally to coincide with the delivered beam axis as well as in the correct angular position to place the patient in the desired pose in a rotational aspect. In particular, as the spatial location of the Bragg peak is dependent both upon the energy of the delivered proton beam as well as the depth and constitution of tissue through which the beam passes, it will be appreciated that a rotation of the patient about the target isocenter even though translationally aligned can present a varying depth and constituency of tissue between the initial impact point and the target isocenter located within the patient's body, thus varying the penetration depth. A further difficulty with registration and positioning is that a radiation therapy regimen typically is implemented via a plurality of separate treatment sessions administered over a period of time, such as daily treatments administered over a several week period. Thus, the alignment of the patient and the target isocenter as well as positioning of the patient in the desired pose with respect to the beam is typically repeatedly determined and executed multiple times over a period of days or weeks. There are several difficulties with accurately performing this patient positioning with respect to the radiation treatment apparatus. As previously mentioned, patient registration is performed by obtaining radiographic images of the patient at a current treatment session at the radiation therapy delivery site and comparing this obtained image with the previously obtained DRR or target image which is used to indicate the particular treatment prescription for the patient. As the patient will have removed and repositioned themselves within the radiation therapy apparatus, the exact position and pose of a patient will not be exactly repeated from treatment session to treatment session nor to the exact position and pose with which the target image was generated, e.g., the orientation from which the original CT scan generated the DRRs. Thus, each treatment session/fraction typically involves precisely matching a subsequently obtained radiographic image with an appropriate corresponding DRR to facilitate the determination of a corrective translational and/or rotational vector to position the patient in the desired location and pose. In addition to the measurement and computational difficulties presented by such an operation, is the desire for speed in execution as well as accuracy. In particular, a radiation therapy apparatus is an expensive piece of medical equipment to construct and maintain both because of the materials and equipment needed in construction and the indication for relatively highly trained personnel to operate and maintain the apparatus. In addition, radiation therapy, such as proton therapy, is increasingly being found an effective treatment for a variety of patient conditions and thus it is desirable to increase patient throughput both to expand the availability of this beneficial treatment to more patients in need of the same as well as reducing the end costs to the patients or insurance companies paying for the treatment and increase the profitability for the therapy delivery providers. As the actual delivery of the radiation dose, once the patient is properly positioned, is a relatively quick process, any additional latency in patient ingress and egress from the therapy apparatus, imaging, and patient positioning and registration detracts from the overall patient throughput and thus the availability, costs, and profitability of the system. A further difficulty with accurately positioning the patient and the corresponding target isocenter in the desired position and pose with respect to the beam nozzle are the multiple and additive uncertainties in the exact position and relative angle of the various components of a radiation therapy system. For example, the beam nozzle can be fitted to a relatively rigid gantry structure to allow the beam nozzle to revolve about a gantry center to facilitate presentation of the radiation beam from a variety of angles with respect to the patient without requiring uncomfortable or inconvenient positioning of the patient themselves. However, as the gantry structure is relatively large (on the order of several meters), massive, and made out of non-strictly rigid materials, there is inevitably some degree of structural flex/distortion and non-repeatable mechanical tolerance as the nozzle revolves about the gantry. Further, the nozzle may be configured as an elongate distributed mass that is also not strictly rigid such that the distal emissions end of the nozzle can flex to some degree, for example as the nozzle moves from an overhead vertical position to a horizontal, sideways presentation of the beam. Accurate identification of the precise nozzle position can also be complicated by a cork screwing with the gantry. Similarly, the patient may be placed on a supportive pod or table and it may be connected to a patient positioning apparatus, both of which are subject to some degree of mechanical flex under gravity load, as well as mechanical tolerances at moving joints that are not necessarily consistent throughout the range of possible patient postures. While it is possible to estimate and measure certain of these variations, as they are typically variable and non-repeatable, it remains a significant challenge to repeatedly position a patient consistently over multiple treatment sessions in both location and pose to tight accuracy limits, such as to millimeter or less accuracy on a predictive basis. Thus, the known way to address gantry and patient table misalignment is to re-register the patient before treatment. This is undesirable as the patient is exposed to additional x-ray radiation for the imaging and overall patient throughput is reduced by the added latency of the re-registration. From the foregoing it will be understood that there is a need for increasing the accuracy and speed of the patient registration process. There is also a need for reducing iteratively imaging and reorienting the patient to achieve a desired pose. There is also a need for a system that accounts for variable and unpredictable position errors to increase the accuracy of patient registration and alignment with a radiation therapy delivery system. Embodiments of the invention provide a patient alignment system that externally measures and provides corrective feedback for variations or deviations from nominal position and orientation between the patient and a delivered therapeutic radiation beam. The alignment system can readily accommodate variable and unpredictable mechanical tolerances and structural flex of both fixed and movable components of the radiation therapy system. The patient alignment system reduces the need for imaging the patient between treatment fractions and decreases the latency of the registration process, thus increasing patient throughput. Other embodiments comprise a radiation therapy delivery system comprising a gantry, a patient fixation device configured to secure a patient with respect to the patient fixation device, a patient positioner interconnected to the patient fixation device so as to position the patient fixation device along translational and rotational axes within the gantry, a radiation therapy nozzle interconnected to the gantry and selectively delivering radiation therapy along a beam axis, a plurality of external measurement devices which obtain position measurements of at least the patient fixation device and the nozzle, and a controller which receives the position measurements of at least the patient fixation device and the nozzle and provides control signals to the patient positioner to position the patient in a desired orientation with respect to the beam axis. Another embodiment comprises a patient positioning system for a radiation therapy system having a plurality of components that are subject to movement, the positioning system comprising a plurality of external measurement devices arranged to obtain position measurements of the plurality of components so as to provide location information, a movable patient support configured to support a patient substantially fixed in position with respect to the patient support and controllably position the patient in multiple translational and rotational axes, and a controller receiving information from the plurality of external measurement devices and providing movement commands to the movable patient support to align the patient in a desired pose such that the positioning system compensates for movement of the plurality of components. Further embodiments include a method of registering and positioning a patient for delivery of therapy with a system having a plurality of components subject to movement, the method comprising the steps of positioning a patient in an initial treatment pose with a controllable patient positioner, externally measuring the location of selected points of the plurality of components, determining a difference vector between the observed initial patient pose and a desired patient pose, and providing movement commands to the patient positioner to bring the patient to the desired patient pose. Yet another embodiment comprises a positioning system for use with a radiation treatment facility wherein the radiation treatment facility has a plurality of components that includes a source of particles and a nozzle from which the particles are emitted, wherein the nozzle is movable with respect to the patient to facilitate delivery of the particles to a selected region of the patient via a plurality of different paths, the positioning system comprising a patient positioner that receives the patient wherein the patient positioner is movable so as to orient the patient with respect to the nozzle to facilitate delivery of the particles in the selected region of the patient, a monitoring system that images at least one component of the radiation treatment facility in proximity to the patient positioner, wherein the monitoring system develops a treatment image indicative of the orientation of the at least one component with respect to the patient prior to treatment, and a control system that controls delivery of particles to the patient wherein the control system receives signals indicative of the treatment to be performed, the signals including a desired orientation of the at least one component when the particles are to be delivered to the patient, wherein the control system further receives the treatment image and the control system evaluates the treatment image to determine an actual orientation of the at least one component prior to treatment and wherein the control system compares the actual orientation of the at least one component prior to treatment to the desired orientation of the at least one component and, if the actual orientation does not meet a pre-determined criteria for correspondence with the desired orientation, the control system sends signals to the patient positioner to move the patient positioner such that the actual orientation more closely corresponds to the desired orientation during delivery of the particles. These and other objects and advantages of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings. Reference will now be made to the drawings wherein like reference designators refer to like parts throughout. FIGS. 1A and 1B illustrate schematically first and second orientations of one embodiment of a radiation therapy system 100, such as based on the proton therapy system currently in use at Loma Linda University Medical Center in Loma Linda, Calif. and as described in U.S. Pat. No. 4,870,287 of Sep. 26, 1989 which is incorporated herein in its entirety by reference. The radiation therapy system 100 is designed to deliver therapeutic radiation doses to a target region within a patient for treatment of malignancies or other conditions from one or more angles or orientations with respect to the patient. The system 100 includes a gantry 102 which includes a generally hemispherical or frustoconical support frame for attachment and support of other components of the radiation therapy system 100. Additional details on the structure and operation of embodiments of the gantry 102 may be found in U.S. Pat. No. 4,917,344 and U.S. Pat. No. 5,039,057, both of which are incorporated herein in their entirety by reference. The system 100 also comprises a nozzle 104 which is attached and supported by the gantry 102 such that the gantry 102 and nozzle 104 may revolve relatively precisely about a gantry isocenter 120, but subject to corkscrew, sag, and other distortions from nominal. The system 100 also comprises a radiation source 106 delivering a radiation beam along a radiation beam axis 140, such as a beam of accelerated protons. The radiation beam passes through and is shaped by an aperture 110 to define a therapeutic beam delivered along a delivery axis 142. The aperture 110 is positioned on the distal end of the nozzle 104 and the aperture 110 may preferably be specifically configured for a patient's particular prescription of therapeutic radiation therapy. In certain applications, multiple apertures 110 are provided for different treatment fractions. The system 100 also comprises one or more imagers 112 which, in this embodiment, are retractable with respect to the gantry 102 between an extended position as illustrated in FIG. 2A and a retracted position as illustrated in FIG. 2B. The imager 112 in one implementation comprises a commercially available solid-state amorphous silicon x-ray imager which can develop image information such as from incident x-ray radiation that has passed through a patient's body. The retractable aspect of the imager 112 provides the advantage of withdrawing the imager screen from the delivery axis 142 of the radiation source 106 when the imager 112 is not needed thereby providing additional clearance within the gantry 102 enclosure as well as placing the imager 112 out of the path of potentially harmful emissions from the radiation source 106 thereby reducing the need for shielding to be provided to the imager 112. The system 100 also comprises corresponding one or more x-ray sources 130 which selectively emit appropriate x-ray radiation along one or more x-ray source axes 144 so as to pass through interposed patient tissue to generate a radiographic image of the interposed materials via the imager 112. The particular energy, dose, duration, and other exposure parameters preferably employed by the x-ray source(s) 130 for imaging and the radiation source 106 for therapy will vary in different applications and will be readily understood and determined by one of ordinary skill in the art. In this embodiment, at least one of the x-ray sources 130 is positionable such that the x-ray source axis 144 can be positioned so as to be nominally coincident with the delivery axis 142. This embodiment provides the advantage of developing a patient image for registration from a perspective which is nominally identical to a treatment perspective. This embodiment also includes the aspect that a first imager 112 and x-ray source 130 pair and a second imager 112 and x-ray source 130 pair are arranged substantially orthogonal to each other. This embodiment provides the advantage of being able to obtain patient images in two orthogonal perspectives to increase registration accuracy as will be described in greater detail below. The imaging system can be similar to the systems described in U.S. Pat. Nos. 5,825,845 and 5,117,829 which are hereby incorporated by reference. The system 100 also comprises a patient positioner 114 (FIG. 3) and a patient pod 116 which is attached to a distal or working end of the patient positioner 114. The patient positioner 114 is adapted to, upon receipt of appropriate movement commands, position the patient pod 116 in multiple translational and rotational axes and preferably is capable of positioning the patient pod 116 in three orthogonal translational axes as well as three orthogonal rotational axes so as to provide a full six degree freedom of motion to placement of the patient pod 116. The patient pod 116 is configured to hold a patient securely in place in the patient pod 116 so to as substantially inhibit any relative movement of the patient with respect to the patient pod 116. In various embodiments, the patient pod 116 comprises expandable foam, bite blocks, and/or fitted facemasks as immobilizing devices and/or materials. The patient pod 116 is also preferably configured to reduce difficulties encountered when a treatment fraction indicates delivery at an edge or transition region of the patient pod 116. Additional details of preferred embodiments of the patient positioner 114 and patient pod 116 can be found in the commonly assigned application (Ser. No. 10/917,022, filed Aug. 12, 2004) entitled “Modular Patient Support System” filed concurrently herewith and which is incorporated herein in its entirety by reference. As previously mentioned, in certain applications of the system 100, accurate relative positioning and orientation of the therapeutic beam delivery axis 142 provided by the radiation source 106 with target tissue within the patient as supported by the patient pod 116 and patient positioner 114 is an important goal of the system 100, such as when comprising a proton beam therapy system. However, as previously mentioned, the various components of the system 100, such as the gantry 102, the nozzle 104, radiation source 106, the imager(s) 112, the patient positioner 114, the patient pod 116, and x-ray source(s) 130 are subject to certain amounts of structural flex and movement tolerances from a nominal position and orientation which can affect accurate delivery of the beam to that patient. FIGS. 1A and 1B illustrate different arrangements of certain components of the system 100 and indicate by the broken arrows both translational and rotational deviations from nominal that can occur in the system 100. For example, in the embodiment shown in FIG. 1A, the nozzle 104 and first imager 112 extend substantially horizontally and are subject to bending due to gravity, particularly at their respective distal ends. The second imager 112 is arranged substantially vertically and is not subject to the horizontal bending of the first imager 112. FIG. 1B illustrates the system 100 in a different arrangement rotated approximately 45° counterclockwise from the orientation of FIG. 1A. In this orientation, both of the imagers 112 as well as the nozzle 104 are subject to bending under gravity, but to a different degree than in the orientation illustrated in FIG. 1A. The movement of the gantry 102 between different orientations, such as is illustrated in FIGS. 1A and 1B also subjects components of the system 100 to mechanical tolerances at the moving surfaces. As these deviations from nominal are at least partially unpredictable, non-repeatable, and additive, correcting for the deviations on a predictive basis is extremely challenging and limits overall alignment accuracy. It will be appreciated that these deviations from the nominal orientation of the system are simply exemplary and that any of a number of sources of error can be addressed by the system disclosed herein without departing from the spirit of the present invention. FIGS. 4A-4E illustrate in greater detail embodiments of potential uncertainties or errors which can present themselves upon procedures for alignment of, for example, the nozzle 104 and the target tissue of the patient at an isocenter 120. FIGS. 4A-4E illustrate these sources of uncertainty or error with reference to certain distances and positions. It will be appreciated that the sources of error described are simply illustrative of the types of errors addressed by the system 100 of the illustrated embodiments and that the system 100 described is capable of addressing additional errors. In this embodiment, a distance SAD is defined as a source to axis distance from the radiation source 106 to the rotation axis of the gantry, which ideally passes through the isocenter 120. For purposes of explanation and appreciation of relative scale and distances, in this embodiment, SAD is approximately equal to 2.3 meters. FIG. 4A illustrates that one of the potential sources of error is a source error where the true location of the radiation source 106 is subject to offset from a presumed or nominal location. In this embodiment, the therapeutic radiation beam as provided by the radiation source 106 passes through two transmission ion chambers (TIC) which serve to center the beam. These are indicated as TIC 1 and TIC 3 and these are also affixed to the nozzle 104. The source error can arise from numerous sources including movement of the beam as observed on TIC 1 and/or TIC 3, error in the true gantry 102 rotational angle, and error due to “egging” or distortion from round of the gantry 102 as it rotates. FIG. 4A illustrates source error comprising an offset of the true position of the radiation source 106 from a presumed or nominal location and the propagation of the radiation beam across the SAD distance through the aperture 110 providing a corresponding error at isocenter 120. FIG. 4B illustrates possible error caused by TIC location error, where TIC 1, the radiation source 106, and TIC 3 are offset from an ideal beam axis passing through the nominal gantry isocenter 120. As the errors illustrated by FIGS. 4A and 4B are assumed random and uncorrelated, they can be combined in quadrature and projected through an assumed nominal center of the aperture 110 to establish a total error contribution due to radiation source 106 error projected to the isocenter 120. In this embodiment, before corrective measures are taken (as described in greater detail below), the radiation source error can range from approximately ±0.6 mm to ±0.4 mm. FIG. 4C illustrates error or uncertainty due to position of the aperture 110. The location of the radiation source 106 is assumed nominal; however, error or uncertainty is introduced both by tolerance stack-up, skew, and flex of the nozzle 104 as well as manufacturing tolerances of the aperture 110 itself. Again, as projected from the radiation source 106 across the distance SAD to the nominal isocenter 120, a beam delivery aiming point (BDAP) error is possible between a presumed nominal BDAP and an actual BDAP. In this embodiment, this BDAP error arising from error in the aperture 110 location ranges from approximately ±1.1 mm to ±1.5 mm. The system 100 is also subject to error due to positioning of the imager(s) 112 as well as the x-ray source(s) 130 as illustrated in FIGS. 4D and 4E. FIG. 4D illustrates the error due to uncertainty in the imager(s) 112 position with the position of the corresponding x-ray source(s) 130 assumed nominal. As the emissions from the x-ray source 130 pass through the patient assumed located substantially at isocenter 120 and onward to the imager 112, this distance may be different than the SAD distance and in this embodiment is approximately equal to 2.2 meters. Error or uncertainty in the true position of an imager 112 can arise from lateral shifts in the true position of the imager 112, errors due to axial shifting of the imager 112 with respect to the corresponding x-ray source 130, as well as errors in registration of images obtained by imager 112 to the DRRs. In this embodiment, before correction, the errors due to each imager 112 are approximately ±0.7 mm. Similarly, FIG. 4E illustrates errors due to uncertainty in positioning of the x-ray source(s) 130 with the position of the corresponding imager(s) 112 assumed nominal. Possible sources of error due to the x-ray source 130 include errors due to initial alignment of the x-ray source 130, errors arising from movement of the x-ray source 130 into and out of the beam line, and errors due to interpretation of sags and relative distances of TIC 1 and TIC 3. These errors are also assumed random and uncorrelated or independent and are thus added in quadrature resulting, in this embodiment, in error due to each x-ray source 130 of approximately ±0.7 mm. As these errors are random and independent and uncorrelated and thus potentially additive, in this embodiment the system 100 also comprises a plurality of external measurement devices 124 to evaluate and facilitate compensating for these errors. In one embodiment, the system 100 also comprises monuments, such as markers 122, cooperating with the external measurement devices 124 as shown in FIGS. 2A, 2B, 6 and 7. The external measurement devices 124 each obtain measurement information about the three-dimensional position in space of one or more components of the system 100 as indicated by the monuments as well as one or more fixed landmarks 132 also referred to herein as the “world” 132. In this embodiment, the external measurement devices 124 comprise commercially available cameras, such as CMOS digital cameras with megapixel resolution and frame rates of 200-1000 Hz, which independently obtain optical images of objects within a field of view 126, which in this embodiment is approximately 85° horizontally and 70° vertically. The external measurement devices 124 comprising digital cameras are commercially available, for example as components of the Vicon Tracker system from Vicon Motion Systems Inc. of Lake Forrest, Calif. However, in other embodiments, the external measurement devices 124 can comprise laser measurement devices and/or radio location devices in addition to or as an alternative to the optical cameras of this embodiment. In this embodiment, the markers 122 comprise spherical, highly reflective landmarks which are fixed to various components of the system 100. In this embodiment, at least three markers 122 are fixed to each component of the system 100 of interest and are preferably placed asymmetrically, e.g. not equidistant from a centerline nor evenly on corners, about the object. The external measurement devices 124 are arranged such that at least two external measurement devices 124 have a given component of the system 100 and the corresponding markers 122 in their field of view and in one embodiment a total of ten external measurement devices 124 are provided. This aspect provides the ability to provide binocular vision to the system 100 to enable the system 100 to more accurately determine the location and orientation of components of the system 100. The markers 122 are provided to facilitate recognition and precise determination of the position and orientation of the objects to which the markers 122 are affixed, however in other embodiments, the system 100 employs the external measurement devices 124 to obtain position information based on monuments comprising characteristic outer contours of objects, such as edges or corners, comprising the system 100 without use of the external markers 122. FIG. 5 illustrates one embodiment of determining the spatial position and angular orientation of a component of the system 100. As the component(s) of interest can be the gantry 102, nozzle 104, aperture 110, imager 112, world 132 or other components, reference will be made to a generic “object”. It will be appreciated that the process described for the object can proceed in parallel or in a series manner for multiple objects. Following a start state, in state 150 the system 100 calibrates the multiple external measurement devices 124 with respect to each other and the world 132. In the calibration state, the system 100 determines the spatial position and angular orientation of each external measurement device 124. The system 100 also determines the location of the world 132 which can be defined by a dedicated L-frame and can define a spatial origin or frame-of-reference of the system 100. The world 132 can, of course, comprise any component or structure that is substantially fixed within the field of view of the external measurement devices 124. Hence, structures that are not likely to move or deflect as a result of the system 100 can comprise the world 132 or point of reference for the external measurement devices 124. A wand, which can include one or more markers 122 is moved within the fields of view 126 of the external measurement devices 124. As the external measurement devices 124 are arranged such that multiple external measurement devices 124 (in this embodiment at least two) have an object in the active area of the system 100 in their field of view 126 at any given time, the system 100 correlates the independently provided location and orientation information from each external measurement device 124 and determines corrective factors such that the multiple external measurement devices 124 provide independent location and orientation information that is in agreement following calibration. The particular mathematical steps to calibrate the external measurement devices 124 are dependent on their number, relative spacing, geometrical orientations to each other and the world 132, as well as the coordinate system used and can vary among particular applications, however will be understood by one of ordinary skill in the art. It will also be appreciated that in certain applications, the calibration state 150 would need to be repeated if one or more of the external measurement devices 124 or world 132 is moved following calibration. Following the calibration state 150, in state 152 multiple external measurement devices 124 obtain an image of the object(s) of interest. From the images obtained in state 152, the system 100 determines a corresponding direction vector 155 to the object from each corresponding external measurement device 124 which images the object in state 154. This is illustrated in FIG. 6 as vectors 155a-d corresponding to the external measurement devices 124a-d which have the object in their respective fields of view 126. Then, in state 156, the system 100 calculates the point in space where the vectors 155 (FIG. 6) determined in state 154 intersect. State 156 thus returns a three-dimensional location in space, with reference to the world 132, for the object corresponding to multiple vectors intersecting at the location. As the object has been provided with three or more movements or markers 122, the system 100 can also determine the three-dimensional angular orientation of the object by evaluating the relative locations of the individual markers 122 associated with the object. In this implementation, the external measurement devices 124 comprise cameras, however, any of a number of different devices can be used to image, e.g., determine the location, of the monuments without departing from the spirit of the present invention. In particular, devices that emit or receive electromagnetic or audio energy including visible and non-visible wavelength energy and ultra-sound can be used to image or determine the location of the monuments. The location and orientation information determined for the object is provided in state 160 for use in the system 100 as described in greater detail below. In one embodiment, the calibration state 150 can be performed within approximately one minute and allows the system 100 to determine the object's location in states 152, 154, 156, and 160 to within 0.1 mm and orientation to within 0.15° with a latency of no more than 10 ms. As previously mentioned, in other embodiments, the external measurement devices 124 can comprise laser measurement devices, radio-location devices or other devices that can determine direction to or distance from the external measurement devices 124 in addition to or as an alternative to the external measurement devices 124 described above. Thus, in certain embodiments a single external measurement device 124 can determine both range and direction to the object to determine the object location and orientation. In other embodiments, the external measurement devices 124 provide only distance information to the object and the object's location in space is determined by determining the intersection of multiple virtual spheres centered on the corresponding external measurement devices 124. In certain embodiments, the system 100 also comprises one or more local position feedback devices or resolvers 134 (See, e.g., FIG. 1). The local feedback devices or resolvers 134 are embodied within or in communication with one or more components of the system 100, such as the gantry 102, the nozzle 104, the radiation source 106, the aperture 110, the imager(s) 112, patient positioner 114, patient pod 116, and/or world 132. The local feedback devices 134 provide independent position information relating to the associated component of the system 100. In various embodiments, the local feedback devices 134 comprise rotary encoders, linear encoders, servos, or other position indicators that are commercially available and whose operation is well understood by one of ordinary skill in the art. The local feedback devices 134 provide independent position information that can be utilized by the system 100 in addition to the information provided by the external measurement devices 124 to more accurately position the patient. The system 100 also comprises, in this embodiment, a precision patient alignment system 200 which employs the location information provided in state 160 for the object(s). As illustrated in FIG. 8, the patient alignment system 200 comprises a command and control module 202 communicating with a 6D system 204, a patient registration module 206, data files 210, a motion control module 212, a safety module 214, and a user interface 216. The patient alignment system 200 employs location information provided by the 6D system 204 to more accurately register the patient and move the nozzle 104 and the patient positioner 114 to achieve a desired treatment pose as indicated by the prescription for the patient provided by the data files 210. In this embodiment, the 6D system 204 receives position data from the external measurement devices 124 and from the resolvers 134 relating to the current location of the nozzle 104, the aperture 110, the imager 112, the patient positioner 114, and patient pod 116, as well as the location of one or more fixed landmarks 132 indicated in FIG. 9 as the world 132. The fixed landmarks, or world, 132 provide a non-moving origin or frame of reference to facilitate determination of the position of the moving components of the radiation therapy system 100. This location information is provided to a primary 6D position measurement system 220 which then uses the observed data from the external measurement devices 124 and resolvers 134 to calculate position and orientation coordinates of these five components and origin in a first reference frame. This position information is provided to a 6D coordination module 222 which comprises a coordinate transform module 224 and an arbitration module 226. The coordinate transform module 224 communicates with other modules of the patient alignment system 200, such as the command and control module 202 and the motion control with path planning and collision avoidance module 212. Depending on the stage of the patient registration and therapy delivery process, other modules of the patient alignment system 200 can submit calls to the 6D system 204 for a position request of the current configuration of the radiation therapy system 100. Other modules of the patient alignment system 200 can also provide calls to the 6D system 204 such as a coordinate transform request. Such a request typically will include submission of location data in a given reference frame, an indication of the reference frame in which the data is submitted and a desired frame of reference which the calling module wishes to have the position data transformed into. This coordinate transform request is submitted to the coordinate transform module 224 which performs the appropriate calculations upon the submitted data in the given reference frame and transforms the data into the desired frame of reference and returns this to the calling module of the patient alignment system 200. For example, the radiation therapy system 100 may determine that movement of the patient positioner 114 is indicated to correctly register the patient. For example, a translation of plus 2 mm along an x-axis, minus 1.5 mm along a y-axis, no change along a z-axis, and a positive 1° rotation about a vertical axis is indicated. This data would be submitted to the coordinate transform module 224 which would then operate upon the data to return corresponding movement commands to the patient positioner 114. The exact coordinate transformations will vary in specific implementations of the system 100 depending, for example, on the exact configuration and dimensions of the patient positioner 114 and the relative position of the patient positioner 114 with respect to other components of the system 100. However, such coordinate transforms can be readily determined by one of ordinary skill in the art for a particular application. The arbitration module 226 assists in operation of the motion control module 212 by providing specific object position information upon receipt of a position request. A secondary position measurement system 230 provides an alternative or backup position measurement function for the various components of the radiation therapy system 100. In one embodiment, the secondary position measurement system 230 comprises a conventional positioning functionality employing predicted position information based on an initial position and commanded moves. In one embodiment, the primary position measurement system 220 receives information from the external measurement devices 124 and the secondary position measurement system 230 receives independent position information from the resolvers 134. It will generally be preferred that the 6D measurement system 220 operate as the primary positioning system for the previously described advantages of positioning accuracy and speed. FIG. 10 illustrates in greater detail the patient registration module 206 of the patient alignment system 200. As previously described, the 6D system 204 obtains location measurements of various components of the radiation therapy system 100, including the table or patient pod 116 and the nozzle 104 and determines position coordinates of these various components and presents them in a desired frame of reference. The data files 210 provide information relating to the patient's treatment prescription, including the treatment plan and CT data previously obtained at a planning or prescription session. This patient's data can be configured by a data converter 232 to present the data in a preferred format. The imager 112 also provides location information to the 6D system 204 as well as to an image capture module 236. The image capture module 236 receives raw image data from the imager 112 and processes this data, such as with filtering, exposure correction, scaling, and cropping to provide corrected image data to a registration algorithm 241. In this embodiment, the CT data undergoes an intermediate processing step via a transgraph creation module 234 to transform the CT data into transgraphs which are provided to the registration algorithm 241. The transgraphs are an intermediate data representation and increase the speed of generation of DRRs. The registration algorithm 241 uses the transgraphs, the treatment plan, the current object position data provided by the 6D system 204 and the corrected image data from the imager(s) 112 to determine a registered pose which information is provided to the command and control module 202. The registration algorithm 241 attempts to match either as closely as possible or to within a designated tolerance the corrected image data from the imager 112 with an appropriate DRR to establish a desired pose or to register the patient. The command and control module 202 can evaluate the current registered pose and provide commands or requests to induce movement of one or more of the components of the radiation therapy system 100 to achieve this desired pose. Additional details for a suitable registration algorithm may be found in the published doctoral dissertation of David A. LaRose of May 2001 submitted to Carnegie Mellon University entitled “Iterative X-ray/CT Registration Using Accelerated Volume Rendering” which is incorporated herein in its entirety by reference. FIGS. 11-13 illustrate embodiments with which the system 100 performs this movement. FIG. 11 illustrates that the command and control module 202 has provided a call for movement of one or more of the components of the radiation therapy system 100. In state 238, the motion control module 212 retrieves a current position configuration from the 6D system 204 and provides this with the newly requested position configuration to a path planning module 240. The path planning module 240 comprises a library of three-dimensional model data which represent position envelopes defined by possible movement of the various components of the radiation therapy system 100. For example, as previously described, the imager 112 is retractable and a 3D model data module 242 indicates the envelope or volume in space through which the imager 112 can move depending on its present and end locations. The path planning module 240 also comprises an object movement simulator 244 which receives data from the 3D model data module 242 and can calculate movement simulations for the various components of the radiation therapy system 100 based upon this data. This object movement simulation module 244 preferably works in concert with a collision avoidance module 270 as illustrated in FIG. 12. FIG. 12 again illustrates one embodiment of the operation of the 6D system 204 which in this embodiment obtains location measurements of the aperture 110, imager 112, nozzle 104, patient positioner and patient pod 114 and 116 as well as the fixed landmarks or world 132. FIG. 12 also illustrates that, in this embodiment, local feedback is gathered from resolvers 134 corresponding to the patient positioner 114, the nozzle 104, the imager 112, and the angle of the gantry 102. This position information is provided to the collision avoidance module 270 which gathers the object information in an object position data library 272. This object data is provided to a decision module 274 which evaluates whether the data is verifiable. In certain embodiments, the evaluation of the module 274 can investigate possible inconsistencies or conflicts with the object position data from the library 272 such as out-of-range data or data which indicates, for example, that multiple objects are occupying the same location. If a conflict or out-of-range condition is determined, e.g., the result of the termination module 274 is negative, a system halt is indicated in state 284 to inhibit further movement of components of the radiation therapy system 100 and further proceeds to a fault recovery state 286 where appropriate measures are taken to recover or correct the fault or faults. Upon completion of the fault recovery state 286, a reset state 290 is performed followed by a return to the data retrieval of the object position data library in module 272. If the evaluation of state 274 is affirmative, a state 276 follows where the collision avoidance module 270 calculates relative distances along current and projected trajectories and provides this calculated information to an evaluation state 280 which determines whether one or more of the objects or components of the radiation therapy system 100 are too close. If the evaluation of stage 280 is negative, e.g., that the current locations and projected trajectories do not present a collision hazard, a sleep or pause state 282 follows during which movement of the one or more components of the radiation therapy system 100 is allowed to continue as indicated and proceeds to a recursive sequence through modules 272, 274, 276, 280, and 282 as indicated. However, if the results of the evaluation state 280 are affirmative, e.g., that either one or more of the objects are too close or that their projected trajectories would bring them into collision, the system halt of state 284 is implemented with the fault recovery and reset states 286 and 290, following as previously described. Thus, the collision avoidance module 270 allows the radiation therapy system 100 to proactively evaluate both current and projected locations and movement trajectories of movable components of the system 100 to mitigate possible collisions before they occur or are even initiated. This is advantageous over systems employing motion stops triggered, for example, by contact switches which halt motion upon activation of stop or contact switches, which by themselves may be inadequate to prevent damage to the moving components which can be relatively large and massive having significant inertia, or to prevent injury to a user or patient of the system. Assuming that the object movement simulation module 244 as cooperating with the collision avoidance module 270 indicates that the indicated movements will not pose a collision risk, the actual movement commands are forwarded to a motion sequence coordinator module 246 which evaluates the indicated movement vectors of the one or more components of the radiation therapy system 100 and sequences these movements via, in this embodiment, five translation modules. In particular, the translation modules 250, 252, 254, 260, and 262 translate indicated movement vectors from a provided reference frame to a command reference frame appropriate to the patient positioner 114, the gantry 102, the x-ray source 130, the imager 112, and the nozzle 104, respectively. As previously mentioned, the various moveable components of the radiation therapy system 100 can assume different dimensions and be subject to different control parameters and the translation modules 250, 252, 254, 260, and 262 interrelate or translate a motion vector in a first frame of reference into the appropriate reference frame for the corresponding component of the radiation therapy system 100. For example, in this embodiment the gantry 102 is capable of clockwise and counterclockwise rotation about an axis whereas the patient positioner 114 is positionable in six degrees of translational and rotational movement freedom and thus operates under a different frame of reference for movement commands as compared to the gantry 102. By having the availability of externally measured location information for the various components of the radiation therapy system 100, the motion sequence coordinator module 246 can efficiently plan the movement of these components in a straightforward, efficient and safe manner. FIG. 14 illustrates a workflow or method 300 of one embodiment of operation of the radiation therapy system 100 as provided with the patient alignment system 200. From a start state 302, follows an identification state 304 wherein the particular patient and treatment portal to be provided is identified. This is followed by a treatment prescription retrieval state 306 and the identification and treatment prescription retrieval of states 304 and 306 can be performed via the user interface 216 and accessing the data files of module 210. The patient is then moved to an imaging position in state 310 by entering into the patient pod 116 and actuation of the patient positioner 114 to position the patient pod 116 securing the patient in the approximate position for imaging. The gantry 102, imager(s) 112, and radiation source(s) 130 are also moved to an imaging position in state 312 and in state 314 the x-ray imaging axis parameters are determined as previously described via the 6D system 204 employing the external measurement devices 124, cooperating markers 122, and resolvers 134. In state 316, a radiographic image of the patient is captured by the imager 112 and corrections can be applied as needed as previously described by the module 236. In this embodiment, two imagers 112 and corresponding x-ray sources 130 are arranged substantially perpendicularly to each other. Thus, two independent radiographic images are obtained from orthogonal perspectives. This aspect provides more complete radiographic image information than from a single perspective. It will also be appreciated that in certain embodiments, multiple imaging of states 316 can be performed for additional data. An evaluation is performed in state 320 to determine whether the radiographic image acquisition process is complete and the determination of this decision results either in the negative case with continuation of the movement of state 312, the determination of state 314 and the capture of state 316 as indicated or, when affirmative, followed by state 322. In state 322, external measurements are performed by the 6D system 204 as previously described to determine the relative positions and orientations of the various components of the radiation therapy system 100 via the patient registration module 206 as previously described. In state 324, motion computations are made as indicated to properly align the patient in the desired pose. While not necessarily required in each instance of treatment delivery, this embodiment illustrates that in state 326 some degree of gantry 102 movement is indicated to position the gantry 102 in a treatment position as well as movement of the patient, such as via the patient positioner 114 in state 330 to position the patient in the indicated pose. Following these movements, state 332 again employs the 6D system 204 to externally measure and in state 334 to compute and analyze the measured position to determine in state 336 whether the desired patient pose has been achieved within the desired tolerance. If adequately accurate registration and positioning of the patient has not yet been achieved, state 340 follows where a correction vector is computed and transformed into the appropriate frame of reference for further movement of the gantry 102 and/or patient positioner 114. If the decision of state 336 is affirmative, e.g., that the patient has been satisfactorily positioned in the desired pose, the radiation therapy fraction is enabled in state 342 in accordance with the patient's prescription. For certain patient prescriptions, it will be understood that the treatment session may indicate multiple treatment fractions, such as treatment from a plurality of orientations and that appropriate portions of the method 300 may be iteratively repeated for multiple prescribed treatment fractions. However, for simplicity of illustration, a single iteration is illustrated in FIG. 14. Thus, following the treatment delivery of state 342, a finished state 344 follows which may comprise the completion of treatment for that patient for the day or for a given series of treatments. Thus, the radiation therapy system 100 with the patient alignment system 200, by directly measuring movable components of the system 100, employs a measured feedback to more accurately determine and control the positioning of these various components. A particular advantage of the system 100 is that the patient can be more accurately registered at a treatment delivery session than is possible with known systems and without an iterative sequence of radiographic imaging, repositioning of the patient, and subsequent radiographic imaging and data analysis. This offers the significant advantage both of more accurately delivering the therapeutic radiation, significantly decreasing the latency of the registration, imaging and positioning processes and thus increasing the possible patient throughput as well as reducing the exposure of the patient to x-ray radiation during radiographic imaging by reducing the need for multiple x-ray exposures during a treatment session. Although the preferred embodiments of the present invention have shown, described and pointed out the fundamental novel features of the invention as applied to those embodiments, it will be understood that various omissions, substitutions and changes in the form of the detail of the device illustrated may be made by those skilled in the art without departing from the spirit of the present invention. Consequently, the scope of the invention should not be limited to the foregoing description but is to be defined by the appended claims.
	abstract	A seal arrangement for providing a seal between a nuclear reactor in-core instrument housing and an instrument contained within the housing includes a lower seal assembly surrounding an outer portion of the in-core instrument housing, an upper seal assembly surrounding an outer portion of the in-core instrument, a seal housing enclosing the lower and upper seal assemblies, and lower and upper compression assemblies positioned on respective ends of the seal housing. The compression assemblies each include a drive nut and a compression collar. The compression collars engage and apply an axial load on the seal assemblies to maintain a reliable seal between the seal housing and the outer portion of the in-core instrument housing, and between the seal housing and the outer portion of the in-core instrument.
	abstract	Methods and apparatuses are provided for removing thermal energy from a nuclear reactor, which are fault tolerant. The apparatus includes at least one heat pipe configured to absorb thermal energy produced by the nuclear reactor. In addition, the apparatus includes a first compartment thermally coupled to the at least one heat pipe. The first compartment is configured to contain a first gas. Furthermore, the apparatus includes a second compartment thermally coupled to the at least one heat pipe. The second compartment is configured to contain a second gas and configured to isolate the second gas from the first gas.
	abstract	Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.
	summary
047012994	claims	1. In a water moderated and cooled nuclear reactor having a core with a periphery comprising a plurality of vertically standing adjacent assemblies of prismatic shape and a cylindrical core containment with a vertical axis around said core and separated therefrom by an annular space, a modular lining adapting the containment to the periphery of said core, said lining comprising: a plurality of adjacent vertical columns of solid modular blocks having vertical surfaces and occupying substantially the whole volume of said annular sapce, each vertical surface of each of said modular blocks confronting a vertical surface of said core, said core containment, or another of modular blocks, localized thin packing pieces separating all mutually adjacent ones of said vertical surfaces which are formed on said modular elements and core containment, said packing pieces being constructed and arranged for maintaining a gap for water flow between said adjacent surfaces, whereby thermal expansion and water cooling are possible, and water cooled, threaded means for connection of each of said blocks to said cylindrical containment. a sleeve (16) fixes inside a blind hole (15) machined in the modular block (5), the axis of which is in the extension of the axis of a bore (12) passing through the core containment (1), possessing a central bore (24) of which the diameter is substantially equal to the diameter of the bore (12) passing through the core containment (1), and a non-cylindrical housing (21) into which the central bore (24) emerges at its end located in the region of the bottom of the blind hole (15), the sleeve (16) creating a space with this bottom (15b), and at least one radial hole (26) passing right through its lateral wall, and a screw (18) having an axially directed hole (28) over its entire length and comprising a tubular body (31), the external diameter of which is slightly less than the diameter of the bore (12) of the core containment (1) and of the central bore (24) of the sleeve (16), a head (20), the shape of which matches the shape of the housing (21) machined in the end of the sleeve (16) in which it is inserted, and a threaded part (29) provided with a tightening nut (30), the screw (18) inserted in the central bore (24) of the sleeve (16) and in the bore (12) of the core containment bearing against the sleeve (16) via its head (20) and against the outer surface of the core containment (1) via the nut (30) fitted to its threaded part (29), and the space created between the bottom (15b) of the blind hole and the end of the sleeve (16) communicating with the entrance of the radial hole (26) located on the outer surface of the sleeve (16), with the result that water circulation can be established, during operation, between the outside and the inside of the core containment (1) through the axial hole (28) in the screw (18), the terminal space in the blind hole (15), the radial hole (26) in the sleeve (16) and, finally, the space (32) between the mutually adjacent solid metal blocks having mutually confronting planar, surfaces separated by a narrow clearance, in continuous mutual abutment through thin spacers which maintain a path for circulation of cooling water which bypasses the upward water flow through the core, those of the blocks which are adjacent to the containment envelope being separated therefrom by additional spacers, thereby defining a narrow path with the envelope for circulation of cooling water, and screw means cooled by an internal flow of water and securing said blocks to said containment envelope. a blind hole formed in the modular block associated with said screw means, sleeve means removably secured in said hole defining an end chamber therewith and formed with an axial bore opening into said chamber, a passage formed in said envelope in alignment with said bore, a screw having a stem projecting through said bore and passage and defining an annular water flow passage between said chamber and said narrow path and a head in abutting connection with said sleeve in said chamber, and nut means threadedly received on said stem and in abutting contact with said envelope, wherein said axial bore, chamber and annular water flow passage constitute a circulation path for said internal flow of water between said path for downward circulation of water and said narrow path. 2. The modular lining as claimed in claim 1 wherein each of said blocks is fixed to the core containment by a set of screw devices constituting part of said threaded means. 3. The modular lining as claimed in claim 2, wherein only some of the modular blocks (45) possess holes (42) for the circulation of the reactor cooling water. 4. The modular lining as claimed in claim 8, wherein some of the modular blocks are (55a,55b) are joined to the core containment (51) by screw devices (60), and the other modular blocks (55c) are each joined to a modular block (55a or 55b), joined to the core containment (51), by means of a key (56) welded to the block (55a or 55b). 5. The modular lining as claimed in any of claims 1, 2, 3 and 4, wherein each of the threaded means for fixing the modular blocks to the core containment comprises: 6. The modular lining as claimed in claim 5, wherein the sleeve (16) is externally threaded so that it can be screwed into a tapped part of the blind hole (15), the sleeve (16) also being locked in rotation by means of a weld (17). 7. In a pressurized water reactor having a pressure vessel, a cylindrical containment envelope in said vessel having a vertical axis and defining with the reactor vessel a path for downward circulation of water, and a core consisting of a plurality of fuel assemblies of prismatic shape arranged vertically and side by side within said containment envelope and cooled by an upward flow of water which has previously circulated along said path, a modular lining which substantially fills an annular space between said containment envelope and said core and constitutes a neutron reflector, comprising: 8. A modular lining as claimed in claim 7, wherein said blocks comprise blocks of a plurality of different types and each of said blocks has part of its lateral surface confronting said containment envelope said part being directly secured to said envelope by said screw means. 9. A modular lining as claimed in claim 7, wherein each of said screw means comprises:
040594840	abstract	A hybrid fuel assembly for use in nuclear fuel reactors, such as a large pressurized water reactor, including a fuel assembly having a matrix of fuel rods of different sizes, wherein fuel rods of a first large size are disposed in island arrays which are located within the matrix of fuel rods of the second small size in the vicinity of the control rod guide tubes of the assembly, such that retention of the control rods normally associated with a reactor fuel assembly employing fuel rods only of the first size is possible while still allowing for the maximum linear heat generation rate (LHGR) for the larger first size rods to be reduced to the LHGR normal for the second smaller size fuel rods or lower.
048204722	abstract	Spent fuel racks for housing new or spent fuel assemblies at a nuclear reactor site. The racks are made to modular design and include upper and lower grid structures which provide aligned square openings. A container or cell shaped to the size of a fuel assembly fits in each of the aligned square openings. To provide verticality to the aligned and uniformly spaced cells, leveling pads beneath the base plate supporting the cells are adjustable vertically to cause the base plate to assume a horizontal plane and thereby align cell longitudinal axis with a vertical plane.
	abstract	A method for fabricating a supermirror for forming a neutron guide. In the method, a neutron supermirror, which is widely used in the formation of thin films in cold neutron guides and the spectrometer field, is fabricated with nickel thin films and titanium thin films, having varying thickness, using a combination of monochromator structures in which nickel thin films and titanium thin films, having the same thickness, are stacked in the form of periodic structures. According to the method, a combination of monochromator structures having a variety of different thicknesses is formed, such that the amount of the overlap of peaks due to the monochromator structures can be adjusted to increase reflectivity, and some of the monochromator structures can be removed during the fabrication of the supermirror to make it easy to extract monochromatic beams, such that it is easy to fabricate a transmission monochromator, rather than a reflection monochromator.
	description	This application is the U.S. National Phase of PCT/JP2017/034661, filed Sep. 26, 2017, which claims the benefit of priority from Japanese Patent Application Serial No. 2016-192386 filed Sep. 30, 2016, the contents of each of which are hereby incorporated by reference in entirety. A dedicated container for storing or conveying spent nuclear fuel (hereinafter, referred to as spent fuel) taken out of a nuclear reactor is referred to as a cask. As a type of this cask, there are a so-called metal cask for accommodating spent fuel in an extremely thick metal cylinder in a tightly closed state, and a so-called concrete cask for accommodating spent fuel in a metal container called a canister thinner than the metal cylinder in a tightly closed state, and accommodating this canister in a cylindrical thick concrete container body. As a material of the metal cylinder of the metal cask or the canister of the concrete cask, metal unlikely to get rusted such as stainless steel is used. In the concrete cask, the canister is stored in the concrete container body, and therefore the metal thickness of the canister can be made drastically thinner than the metal thickness of the metal cask, and the amount of metal to be used can be drastically reduced. Therefore, the manufacturing cost of the entire concrete cask including the concrete container body and the canister can be reduced compared to the metal cask. The concrete cask is disclosed in, for example, Patent Literatures 1, 2 and the like. The spent fuel generates decay heat. Therefore, in the concrete cask, in order to suppress excessive temperature rise due to the decay heat, as simply illustrated in FIG. 12 and FIG. 13, a container body 101 and a canister 102 are disposed in a state of having a gap formed from a cooling passage 103 between the internal peripheral surface of the container body 101 and the external peripheral surface of the canister 102, and air introduction passages 104 leading to the bottom end part of this cooling passage 103, and air discharge passages 105 leading to the top end part of the cooling passage 103 are provided so as to radially penetrate the container body 101. Reference numeral 101a denotes a lid of the container body 101. Cooling air is introduced in the bottom end part of the cooling passage 103 through the air introduction passages 104, and thereafter is naturally circulated upward while being warmed by decay heat emitted from the canister 102 (that is, while absorbing this decay heat), and is discharged from the air discharge passages 105 connected to the top end part of the cooling passage 103. In order to discharge the decay heat emitted from the top surface of the canister 102, a top space 106 is provided between the top surface of the canister 102 and the lid 101a of the container body 101. Air of this top space 106 is led to the top end part of the cooling passage 103, and is discharged from the air discharge passages 105 together with the cooling air of the cooling passage 103. As simply illustrated in FIG. 12 and FIG. 13, the air introduction passages 104 and the air discharge passages 105 are provided with bent parts or the like in the middle of the passages, and are configured such that radioactive rays do not leak out (or are unlikely to leak out) through the air introduction passages 104 and the air discharge passages 105. In FIG. 12 and FIG. 13, reference numeral 104a denotes an air inlet, and reference numeral 105a denotes an air outlet. The cylindrical canister 102 is composed of a canister body 102a having a bottomed cylindrical shape with an open top surface, and a lid 102b for closing an opening of the top surface of the canister body 102a. The cylindrical canister 102 has a sealed structure by closing the opening of the top surface of the canister body 102a with the lid 102b to be welded, after accommodating the spent fuel in the canister body 102a. The canister body 102a is manufactured by first curving a rectangular plate-like metal plate and welding the curved metal plate to manufacture a body, and then joining a bottom surface part to this body by welding, at a place without radioactivity such as a factory. On the other hand, the lid 102b is welded to be joined after spent fuel taken out of the nuclear reactor is accommodated in the canister body 102a, and therefore is weld and joined to the canister body 102a by using a robot or the like in high-concentration radioactivity atmosphere such as a fuel outlet of the nuclear reactor. Reference numeral 102c in FIG. 12 and FIG. 13 denotes a lid welded part, and reference numeral 102d denotes a side surface welded part. Japanese Patent Laid-Open No. 2001-141883 Japanese Patent Laid-Open No. 2007-108052 Japan is an island country surrounded by the sea, and therefore there are more than a few possibilities that a storage area of the concrete cask is a coast. In this case, air containing salt from sea water is introduced in the cooling passage 103 of the concrete cask. When the air introduced in the cooling passage 103 contains salt and the humidity becomes high due to condensation on the surface of the canister 102, there is a possibility that the salt is dissolved in water of humid air, and the dissolved chloride ions causes rust or corrosion to occur in a portion in which tensile stress remains in the metal canister 102, resulting in stress corrosion cracking (SCC: Stress Corrosion Cracking). Herein, the canister body 102a is manufactured in a factory or the like, and therefore can be freely worked such that tensile stress does not remain, by burnishing a welded part such as the side surface welded part 102d, or the like. On the other hand, the lid welded part 102c in the canister 102 is welded in the high-concentration radioactivity atmosphere, and therefore it is difficult to work the lid welded part such that tensile stress does not remain after welding. Accordingly, in the conventional concrete cask, there is a possibility that stress corrosion cracking (SCC) occurs in the lid welded part 102c of the canister 102. The present invention solves the aforementioned problem, and an object of the present invention is to provide a concrete cask enabling suppression of occurrence of stress corrosion cracking (SCC) in a lid welded part of a canister. In order to solve the aforementioned problem, a concrete cask according to the present invention including: a metal canister accommodating spent fuel; a concrete container body for accommodating the canister inside the container body; a cooling passage provided between the external peripheral surface of the canister and the internal peripheral surface of the container body, and allowing air for cooling the external peripheral surface of the canister to pass; and a top space provided between a top surface of the canister and inside of a lid of the container body, wherein a baffle plate for suppressing introduction of air rising through the cooling passage to the top space is provided. According to this configuration, direct introduction of air rising through the cooling passage to the top space is suppressed by the baffle plate. As a result, even in a case in which the air introduced inside the container body contains salt, the air containing the salt is unlikely to directly come into contact with the top surface including the lid welded part of the canister, and it is possible to suppress generation of chloride ions on the surface of the canister, particularly, the top surface including the lid welded part, and occurrence of stress corrosion cracking. It is suitable that the baffle plate is mounted on the top external peripheral surface of the canister, and has such a shape that the external periphery expands toward the top. According to this configuration, it is possible to satisfactorily suppress introduction of air rising through the cooling passage to the top space. A mounting bracket for mounting the baffle plate on the canister may be provided, and the baffle plate may be mounted on the top end part of the canister or near the top end part of the canister by the mounting bracket. It is suitable that a material having a coefficient of thermal expansion smaller than the coefficient of thermal expansion of a metal material forming the canister is used as the mounting bracket. According to this configuration, when the temperature of the canister is increased by decay heat of the spent fuel, the coefficient of thermal expansion of the canister is larger than the coefficient of thermal expansion of the mounting bracket, and therefore the canister expands more largely than the mounting bracket, and the baffle plate is satisfactorily mounted in a state of being fastened by strong force by the mounting bracket. A cover plate for covering a lid welded part provided in the top surface of the canister may be mounted. According to this configuration, even in a case in which air containing salt climbs over the baffle plate from the cooling passage to reach the top space, this air is prevented from coming into contact with the lid welded part. According to the present invention, a baffle plate for suppressing introduction of air rising through a cooling passage to a top space is provided, so that even in a case in which air introduced in a container body contains salt, the air containing salt is unlikely to directly come into contact with a top surface including a lid welded part of a canister, and it is possible to suppress generation of chloride ions on a surface of the canister, particularly, the top surface including the lid welded part, and occurrence of stress corrosion cracking, and reliability as a concrete cask is improved. Hereinafter, a concrete cask according to an embodiment of the present invention will be described with reference to the drawings. Reference numeral 10 in FIG. 1 and FIG. 2 denotes the concrete cask according to the embodiment (first embodiment) of the present invention. The concrete cask 10 has a cylindrical metal canister 2 for accommodating spent fuel (spent nuclear fuel) in the canister in a tightly closed state, a cylindrical concrete container body 1 for accommodating this canister 2 in the container, and a cooling passage 3 and a top space 6 described below. As a metal material of the canister 2, a metal material unlikely to get rusted such as stainless steel is used. The spent fuel accommodated in the canister 2 in the tightly closed state generates decay heat, and therefore in the concrete cask 10, in order to suppress excessive temperature rise due to the decay heat, the gap of the substantially cylindrical cooling passage 3 is provided between the internal peripheral surface of the container body 1 and the external peripheral surface of the canister 2, and a gap of the top space 6 is provided between the top surface of the canister 2 and the inside of a lid la of the container body 1. Air introduction passages 4 leading to the bottom end part of the cooling passage 3, and air discharge passages 5 leading to the top end part of the cooling passage 3 are each provided at a plurality of portions so as to penetrate the container body 1 radially (in the direction of a radius). Air for cooling introduced in the bottom end part of the cooling passage 3 through the air introduction passages 4 is naturally circulated upward while being warmed by decay heat emitted from the canister 2 (particularly, the external peripheral surface of the canister 2) (that is, absorbing the decay heat from the canister 2 and cooling the canister 2), and is discharged from the air discharge passages 5 connected to the top end part of the cooling passage 3 to the outside of the concrete cask 10. The top space 6 is connected to the top end part of the cooling passage 3 at the external peripheral part, and the air in the top space 6 is discharged from the air discharge passages 5 to the outside of the concrete cask 10 and the like together with the air in the cooling passage 3, while being warmed by the decay heat emitted from the top surface part of the canister 2 (that is, absorbing the decay heat from the top surface part of the canister 2 and cooling the top surface of the canister 2). The canister 2 has a structure in which spent fuel (spent nuclear fuel) is accommodated in a body 2a having a bottomed cylindrical shape and having an opened top surface part, and thereafter a lid 2b is fixed to the body 2a by welding or the like, and the inside is sealed. For example, the body 2a is manufactured by curving rectangular sheet metal, and welding curved both end parts to form a cylindrical peripheral surface, and joining a bottom surface part to this cylindrical part by welding. As illustrated in FIG. 3, the lid 2b is composed of, for example, an external peripheral ring-shaped part 2ba, and a central disk-shaped part 2bb having a recessed external periphery. In many cases, in a state in which spent fuel is accommodated in the body 2a, the central disk-shaped part 2bb is first welded to the body 2a, and thereafter the external peripheral ring-shaped part 2ba is fitted into the recessed external peripheral part of the central disk-shaped part 2bb to be fixed by welding or the like. However, the lid is not limited to this. Reference numeral 2c in FIG. 1 to FIG. 3 is a lid welded part (top surface welded part) that joins the body 2a of the canister 2 to the lid 2b, and reference numeral 2d denotes an external peripheral welded part provided so as to substantially linearly extend along the vertical direction in the external peripheral surface of the canister 2. As illustrated in FIG. 1, the air introduction passages 4 and the air discharge passages 5 are provided with bent parts or the like in the middle of the passages, and are configured such that radioactive rays from the canister 2 do not leak out (or are unlikely to leak out) through the air introduction passages 4 and the air discharge passages 5. In. FIG. 1, reference numeral 4a denotes an air introduction port, and reference numeral 5a denotes an air discharge port. Reference numeral 7 denotes a bottom space leading to the bottom end part of the cooling passage 3 provided between the bottom surface part of the canister 2 and the inside of the bottom surface part of the container body 1, and reference numeral 8 denotes a canister support placed on the bottom surface part of the container body 1, and supporting the canister 2 from below. A structure of directly supporting the canister 2 from below by the bottom surface part of the container body 1 without providing the canister supports 8 may be employed. As illustrated in FIG. 1 to FIG. 4, in addition to the aforementioned configuration, a baffle plate 11 for suppressing introduction of air rising while passing through the cooling passage 3 to the top space 6 is provided in the concrete cask 10. The baffle plate 11 is mounted over the whole periphery on the top external peripheral surface (external peripheral surface near the top end part) of the canister 2 by a mounting bracket 12. The baffle plate 11 has a ring-shaped (annular) schematic whole shape, and is composed of a mounting part 11a mounted along the top external peripheral surface of the canister 2 by the mounting bracket 12, and a baffling part 11b continuous to the top of this mounting part 11a, as illustrated in FIG. 3, in this embodiment. In a state in which the mounting part 11a at the bottom end part of the baffle plate 11 is in close contact with the top external peripheral surface of the canister 2, the mounting bracket 12 is wound from the external peripheral side of the baffle plate 11, and mounted on the top external peripheral surface of the canister 2. The baffle plate 11 (specifically, the baffling part 11b of the baffle plate 11) has a sectional shape in which the external periphery obliquely expands toward the top. As the baffle plate 11 extends upward from the bottom end part of the baffling part 11b, the baffle plate 11 separates from the top external peripheral surface of the canister 2 and comes close to the internal peripheral surface of the container body 1. Therefore, the baffle plate 11 is configured such that a clearance between the top end (top edge) of the baffle plate 11 and the internal peripheral surface of the container body 1 is smaller than a clearance between the bottom end part of the baffle plate 11 and the internal peripheral surface of the container body 1. The mounting bracket 12 is formed of, for example, a flexible thin belt material, and fixes the baffle plate 11 in a state in which the both ends are fastened by bolts 13, nuts 14, and the like, as illustrated in FIG. 4. In place of this, a pair of halved mounting brackets each having a semicircular shape in a plan view may be fixed to each other by bolts 13, nuts 14, and the like. Herein, the mounting bracket 12 has a coefficient of thermal expansion smaller than the coefficient of thermal expansion of a metal material forming the canister 2. In the concrete cask 10 having the aforementioned structures, air for cooling is introduced in the bottom end part of the cooling passage 3 through the air introduction passages 4, and thereafter is naturally circulated upward while being warmed by decay heat emitted from the canister 102 (that is, absorbing this decay heat), and is discharged from the air discharge passages 5 connected to the top end part of the cooling passage 3. In this case, the baffle plate 11 is mounted over the whole periphery on the top external peripheral surface (external peripheral surface near the top end) of the canister 2, and therefore as illustrated by the solid arrows in FIG. 3, the air rising while passing through the cooling passage 3 is guided to the top external peripheral side region of the cooling passage 3 provided with the air discharge passages 5 along the baffle plate 11. Then, the air is discharged from the air discharge passages 5 to the outside. However, the top end part of the cooling passage 3 is continuous to a gap of the top space 6 between the top surface of the canister 2 and the inside of the lid 1a of the container body 1, and therefore one part of the air rising while passing through the cooling passage 3 flows into the top space 6, and the air in the top space 6 is discharged from the air discharge passages 5 together with the air in the cooling passage 3 to be discharged from the air discharge passages 5 to the outside, as illustrated by the dotted arrows in FIG. 3. That is, while a part of the air rising while passing through the cooling passage 3 flows into the top space 6, most of the air is guided to the top external peripheral side region of the cooling passage 3 along the baffle plate 11, and is discharged from the air discharge passages 5 to the outside. Thus, direct introduction of the air rising while passing through the cooling passage 3 to the top space 6 is suppressed by the baffle plate 11. As described above, the canister body 2a of the canister 2 is manufactured in a factory or the like, and therefore can be freely worked such that tensile stress does not remain, for example, by burnishing a welded part such as the side surface welded part 2d. On the other hand, the lid welded part 2c in the canister 2 is welded in high-concentration radioactivity atmosphere, and therefore it is difficult to work the lid welded part such that tensile stress does not remain after welding. Accordingly, in the conventional concrete cask, there is a possibility that stress corrosion cracking (SCC) occurs in the lid welded part of the canister. On the contrary to this, in this configuration, the direct introduction of the air rising while passing through the cooling passage 3 to the top space 6 is suppressed by the baffle plate 11, and therefore even in a case in which the air introduced in the cooling passage inside the container body 1 contains salt, the air containing the salt is unlikely to directly come into contact with the top surface part of the canister 2, and it is possible to suppress generation of chloride ions on the surface of the canister 2, particularly, the top surface including the lid welded part 2c, and occurrence of stress corrosion cracking. In the aforementioned configuration, the mounting bracket 12 has the coefficient of thermal expansion smaller than the coefficient of thermal expansion of the metal material forming the canister 2. Therefore, when the temperatures of the canister 2, the baffle plate 11 and the mounting bracket 12 are increased by the decay heat of the spent fuel, as the coefficient of thermal expansion of the canister 2 is larger than the coefficient of thermal expansion of the mounting bracket 12, the canister 2 expands more largely than the mounting bracket 12. As a result, the baffle plate 11 is satisfactorily mounted in a state of being fastened by stronger force by the mounting bracket 12. Consequently, the baffle plate 11 can be more reliably prevented from dropping out of a mounting position of the canister 2, and reliability as the concrete cask 10 is improved. In the aforementioned embodiment, a structure in which the lid 2b of the canister 2 is composed of the external peripheral ring-shaped part 2ba, and the central disk-shaped part 2bb having the recessed external periphery is already described. However, the present invention is not limited to this. As illustrated in FIG. 5, even in a case in which a lid 2b of a canister 2 is composed of a primary lid 2bc first closed on the inside of a top surface opening of a canister body 2a to be welded, and a secondary lid 2bd further welded on the outside of this primary lid 2bc, a similar working effect is obtained. As illustrated in FIG. 6, even in a case in which a primary lid 2bc in a lid 2b of a canister 2 is thinner than the aforementioned primary lid 2bc, and a shielding lid 2be is further provided on the inside of the primary lid 2bc, a similar working effect is obtained. FIG. 7 and FIG. 8 are a partially cutout perspective view and a main part sectional front view of a concrete cask 10 according to another embodiment of the present invention. In this concrete cask 10, in addition to the configuration of the aforementioned embodiment, a cover plate 15 covering the top surface part of a canister 2 is mounted on a baffle plate 11. As a constituent material of the cover plate 15, a metal material unlikely to get rusted such as stainless steel is preferable. However, the constituent material is not limited to this, and a resin material or the like may be used. The cover plate 15 is mounted on the top external peripheral surface and the like of the canister 2 over the whole periphery in a state of being interposed between the baffle plate 11 and the external peripheral surface of the canister 2, similarly to the baffle plate 11. As illustrated in FIG. 8, the cover plate 15 is composed of a cylindrical part 15a extending upward along the top external peripheral surface of the canister 2, and a cover part 15b extending in the radially inward direction from the upper end of the cylindrical part, and covering the top surface part of the canister 2, and a holding part 15c extending to the external peripheral side such as a flange shape from the bottom end part of the cylindrical part 15a, and supporting the bottom end part of the baffle plate 11 (or the bottom end part of the baffle plate 11 and the bottom end part of the mounting bracket 12) from below. The cover part 15b extends in the radially inward direction up to such a position as to cover the lid welded part 2c in the top surface part of the canister 2. According to the aforementioned configuration, the cover part 15b covers the lid welded part 2c at the top surface part of the canister 2, and therefore even in a case in which air containing salt climbs over the baffle plate 11 from the cooling passage 3 to reach the top space 6, this air is prevented from coming into contact with the lid welded part 2c. Consequently, it is possible to more reliably prevent generation of chloride ions on the surface of the canister 2, particularly, the surface of the top surface part including the lid welded part 2c, and occurrence of stress corrosion cracking, and reliability as the concrete cask 10 is improved. According to this configuration, the cover plate 15 is mounted together with the baffle plate 11 by the mounting bracket 12, and this cover plate 15 (specifically, the cover part 15b of the cover plate 15) covers the top surface part of the canister 2, and therefore even in a case in which tightening force by the mounting bracket 12 is weakened, the baffle plate 11 (or the baffle plate 11 and the mounting bracket 12) is held from below by the cover plate 15, and the baffle plate 11 (or the baffle plate 11 and the mounting bracket 12) is prevented from dropping off. Consequently, reliability as the concrete cask 10 is improved. In the aforementioned embodiment, the baffling part 11b of the baffle plate 11 has such a sectional shape that the external periphery uniformly expands obliquely toward the top. However, the prevent invention is not limited to this. As illustrated in FIG. 9, only a part (central part in the vertical direction in this modification) of a baffling part may have such a shape that the external periphery uniformly expands obliquely toward the top, or such a shape that the external periphery expands stepwise toward the top (not illustrated). In this configuration, a cover plate 15 similar to FIG. 8 may be provided (not illustrated). As simply illustrated in FIG. 10 and FIG. 11, a member 16 for mounting for also functioning as, for example, a spacer may be disposed between the external peripheral surface of a canister 2 and the internal peripheral surface of a container body 1 (that is, a cooling passage 3), in a state of not hindering the vertical flow of air in a cooling passage 3 much. A groove part (recessed part) 16a for placing a baffle plate 11 may be formed in the top part of this member 16 for mounting, and the baffle plate 11 may be supported by this groove part (recessed part) 16a.
	claims	1. A method of removing radioactive gases and hydrogen gas from a nuclear reactor coolant comprising the steps of:diverting a portion of the reactor coolant to an inlet of an inlet chamber of a contactor housing having a membrane separating the inlet chamber from an outlet chamber, the membrane having pores that pass the radioactive gases and hydrogen gas, but not the reactor coolant, into the outlet chamber;drawing a vacuum on the outlet chamber;providing a relatively small inert gas flow through the outlet chamber;conveying the radioactive gases and hydrogen gas in the outlet chamber to a waste gas system; andtransporting a portion of the reactor coolant that has been degassed through an outlet in the inlet chamber to a desired location. 2. The method of claim 1 wherein the inert gas is nitrogen. 3. The method of claim 1 wherein the inert gas is helium. 4. The method of claim 1 wherein the contactor housing comprises a plurality of contactor housings with the respective inlet chambers connected in parallel. 5. The method of claim 1 wherein the contactor housing comprises a plurality of contactor housings with the respective inlet chambers connected in series. 6. The method of claim 1 wherein the contactor housing comprises a plurality of contactor housings with at least some of the respective plurality of inlet chambers connected in parallel and some of the parallel connected inlet chambers connected in series with at least one other of the plurality of the contactor housings. 7. The method of claim 1 wherein the diverting step occurs during a nuclear reactor plant outage.
	summary
	claims	1. A variable pin-hole type collimator applied to a radiation imaging device comprising:a hole forming module having a plurality of apertures which are stacked in a direction of irradiation such that each aperture defines a penetrating-space through which radiation passes;a plurality of driving modules which are configured such that each driving module varies each penetrating-space of the aperture independently; anda collimating controller to control the driving modules such that each penetrating-space of the aperture varies independently and the hole forming module forms a pin-hole, which is divided into a first cone region, a penetrating hole region and a second cone region, through which radiation passes. 2. The variable pin-hole type collimator according to claim 1, wherein the penetrating-space formed by each aperture has a circular shape or an oval shape. 3. The variable pin-hole type collimator according to claim 1, wherein each aperture is made from a radiation-shielding material. 4. A radiation imaging device to which a variable pin-hole type collimator according to claim 1 is applied.
	claims	1. A coolant injection system for supplementing an RCIC system in a nuclear reactor, the system comprising:the nuclear reactor;a coolant source including a suppression pool;an injection device configured to suck a liquid coolant against gravity;the RCIC system including an RCIC turbine, an RCIC pump powered by the RCIC turbine, and an RCIC line connecting steam to the RCIC turbine from the nuclear reactor;a steam connection connecting steam from the RCIC line to the injection device before the RCIC turbine;a coolant connection connecting the liquid coolant from the suppression pool to the injection device; andan outlet connection connecting the steam and the liquid coolant to the nuclear reactor, wherein the injection device is configured to entrain the liquid coolant in the steam and inject the entrained liquid coolant and steam into the nuclear reactor, and wherein there are no pumps or turbines along the outlet connection between the injection device and the nuclear reactor. 2. The system of claim 1, wherein the steam is at less than 150 pounds per square inch pressure. 3. The system of claim 1, wherein the injection device is a venturi including a narrowing section configured to increase a velocity and reduce a pressure of the steam flowing through the narrowing section. 4. The system of claim 3, wherein the venturi connects to the coolant connection at the narrowing section so as to draw the liquid coolant into the venturi with the pressure. 5. The system of claim 3, wherein the venturi further includes a diffuser section configured to increase a pressure of the entrained liquid coolant and steam. 6. The system of claim 1, wherein,the nuclear reactor is a light water reactor,the RCIC line is a line connecting a main steam line of the reactor to the steam connection,the coolant connection is a line connecting the suppression pool of the reactor to the injection device, andthe outlet connection is a line connecting the injection device to a main feedwater line of the reactor. 7. The system of claim 6, wherein the suppression pool is below the reactor and below the injection device, and wherein the coolant connection is a line running upward from below a coolant level in the suppression pool to the injection device. 8. The system of claim 6, wherein the main steam line connects to a turbine with a generator to produce electricity, and wherein the steam connection diverts from the main steam line before the turbine. 9. The system of claim 6, wherein the steam connection includes a steam diversion line diverting from the RCIC line that diverts from the main steam line, and wherein the main feedwater line is connected to the reactor and a coolant source that provides only liquid water coolant. 10. The system of claim 1, wherein at least one of the steam connection, the coolant connection, and the outlet connection includes a swing check valve to control operation of the system. 11. The system of claim 1, wherein the injection device is configured to entrain a volumetric flow rate of the liquid coolant sufficient to maintain a liquid coolant level in the reactor when the reactor is generating only decay heat. 12. The system of claim 1, wherein the coolant is entirely below the injection device, and wherein the injection device is configured to entrain the coolant by suction up through the coolant connection. 13. The system of claim 1, wherein the coolant is entirely below the injection device, wherein the injection device is passive and includes no moving parts, and wherein the injection device is configured to draw the coolant up through the coolant connection to the injection device when the steam is at about 50 pounds per square inch of pressure. 14. The system of claim 1, wherein the coolant source is a reservoir holding liquid coolant with a top level entirely below the injection device, and wherein the coolant connection connects between the injection device to below the top level in the reservoir. 15. The system of claim 14, wherein the injection device is a venturi, and wherein the coolant connection connects to the venturi at a narrowest portion of the venturi. 16. The system of claim 15, further comprising:a main steam line connecting the reactor to a turbine with electrical generator, wherein the steam connection diverts from the RCIC line to the venturi. 17. The system of claim 16, wherein the reactor is in a shut down condition and provides steam that is at less than 150 pounds per square inch pressure in the reactor and the main steam line, and wherein the venturi is configured to entrain the liquid coolant in the steam and inject the liquid coolant and steam into the reactor. 18. A coolant injection system for providing coolant in a shutdown nuclear reactor, the system comprising:a decay-heat driven system including a turbine, a pump, and a coolant source, wherein the turbine is configured to extract power from steam generated in the shutdown nuclear reactor to power the pump, and wherein the pump is configured to inject liquid coolant from the coolant source into the shutdown nuclear reactor under power from the turbine;an injection device configured to entrain the liquid coolant in the steam at steam pressures below which the turbine cannot operate the pump, wherein the injection device is configured to entrain the liquid coolant in the steam without electrical power;a steam connection connecting the steam from the shutdown nuclear reactor to the injection device, wherein the steam connection connects directly to the shutdown nuclear reactor and the injection device and consists only of piping and a valve controlling steam flow through the steam connection;a coolant connection connecting the liquid coolant from the liquid coolant source to the injection device, wherein the injection device consists only of a venturi with the coolant connection connecting to the venturi at a narrowest flow area of the venturi, and wherein the coolant connection connects directly to the liquid coolant source and the injection device and consists only of piping and a valve controlling liquid water flow through the coolant connection; andan outlet connection connecting the steam and the liquid coolant as entrained in the injection device to the nuclear reactor, wherein the outlet connection connects directly to the injection device and the shutdown nuclear reactor and consists only of piping and a valve controlling entrained steam and liquid water flow through the outlet connection.
	abstract	An extreme ultraviolet light source apparatus comprises a target supply unit supplying a target into a vacuum chamber, a laser oscillator outputting a laser light into the vacuum chamber, a collector mirror outputting an extreme ultraviolet light outside by reflecting the extreme ultraviolet light emitted from the target being ionized as a plasma by irradiation with the laser light at a plasma luminescence point in the vacuum chamber, and an ion debris removal unit at least a part of which is located in an obscuration region including the plasma luminescence point.
	claims	1. A containment enclosure for processing or storing material containing civilian or military origin plutonium in the form of plutonium oxide, plutonium carbide or plutonium nitride, said containment enclosure comprises a perimeter and a bottom, said containment enclosure being dimensioned to enclose a vessel having a predetermined volume and provided for storing said material, said containment enclosure comprises at its bottom a bottom catcher comprising a plurality of sub-critical spaces which are separated by passive parts forming separators and provided for catching spilt plutonium-containing material, each one of said sub-critical spaces define a space and a volume and is demarcated by at least two substantially parallel and vertical walls having a height (h) between 30 and 50 cm, and separated by a distance e between 8 and 12 cm, said sub-critical spaces being provided to be filled with a solid, mineral and neutron-absorbing material, said bottom catcher being dimensioned to retain a further volume being at least equal to said predetermined volume. 2. The containment enclosure according to claim 1, wherein the further volume of said sub-critical spaces is higher than the predetermined volume of said vessel. 3. A containment enclosure, enclosing a vessel, said containment enclosure being provided for processing or storing material containing civilian or military origin plutonium in the form of plutonium oxide, plutonium carbide or plutonium nitride, said containment enclosure comprises a perimeter and a bottom, said vessel having a predetermined volume and provided for storing said material, said predetermined volume is comprised between 20 to 70 liters, demarcated at least by two substantially parallel walls for containing said material, these two walls being separated by a distance between 8 and 15 cm, said containment enclosure comprises at its bottom a bottom catcher comprising a plurality of sub-critical spaces which are separated by passive parts and provided for catching spilt plutonium-containing material each one of said sub-critical spaces define a space and a volume and being demarcated by at least two substantially parallel and vertical walls having a height (h) between 30 and 50 cm, and separated by a distance e between 8 and 12 cm, said sub-critical spaces being provided to be filled with a solid, mineral and neutron-absorbing material, said bottom catcher being dimensioned to retain a further volume being at least equal to said predetermined volume.
	description	This application claims the benefit of Korean Patent Application No. 10-2014-0102485 filed on Aug. 8, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 1. Field The present disclosure relates to a voloxidizer for processing spent fuel rods. 2. Description of the Related Art Nuclear fuel means substances loaded into a nuclear reactor and generating available energy through continuous nuclear fission and spent fuel rods means residual substances obtained after nuclear fission. According to a conventional method, a nuclear fuel assembly which is burnt up in a nuclear power plant is not treated any longer and is kept/stored in a water tank. However, as an operating hour of nuclear power plant is increased, the amount of spent fuel rods is gradually accumulated so that a huge storage space is required. In addition, the necessity and riskiness of disposing waste materials accumulated as above has been continuously pointed out. Therefore, recycling the solid type spent fuel rods is proposed as disclosed in Korean Patent No. 10-0662085 (published on Dec. 20, 2006). An aspect of the present invention is to provide a voloxidizer with a double reactor for spent fuel rods decladding and a double reactor for use, which increase a separation and collection ratio of hulls and pellets, can form stable oxide powders, and reflects a remote operability in a hot cell. The task to be solved is not limited to the task mentioned above, and another task to be solved which is not mentioned above may be apparently understood by one skilled in the art through the above detail description. One aspect provides a voloxidizer with a double reactor for spent fuel rods decladding according to one embodiment of the present invention includes a reactor module into which spent fuel rods are loaded, the reactor module including a reactor having a dual structure; a heater module for heating the reactor module; and a drive module for providing a driving force to the reactor module. A double reactor utilized in a voloxidizer with a double reaction for spent fuel rods decladding according to another embodiment of the present invention includes an internal reactor into which spent fuel rods are loaded; and an external reactor formed on an outer circumferential surface of the internal reactor, wherein a first transport part and a second transport part are formed on inside surfaces of the internal reactor and the external reactor, respectively, and the spent fuel rods are moved by the first transport part and the second transport part and oxidized when the internal reactor and the external reactor are rotated. Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings. For recycling the solid type spent fuel rods, in an example method, an apparatus for pulverizes the spent fuel rods, oxidizes the powders, and transfers the oxidized powders to a subsequent process. Since hulls and pellets are mixed together in a reactor, a typical oxidizer for oxidizing the spent fuel rods requires an additional separation system for increasing a collection ratio. A typical mesh type oxidizer for the spent fuel rods is disadvantageous in that since powders passing through a mesh are got out of a heater zone, unstable oxide powers are foamed. In embodiments of the invention, first of all, FIG. 1 and FIG. 2 are perspective views for illustrating a voloxidizer with a double reactor for spent fuel rods decladding, and the voloxidizer with the double reactor for spent fuel rods decladding includes a support module 100 to which a plurality of frames are connected, a heater module 200 seated on the support module 100, a reactor module 300 heated by the heater module 200. Here, spent fuel rods are loaded into the reactor module 300. In addition, the voloxidizer with the double reactor for spent fuel rods decladding further includes an utility module 600 mounted to the reactor module 300 for adjusting an internal state of the reactor module 300, a drive module 400 providing the reactor module 300 with a driving force, and a vessel module 500 for collecting the spent fuel rods oxidized in and discharged from the reactor module 300. Since a plurality of clamped rings 700 to which a handling tool (not shown) such as a crane can be coupled are mounted to each module, the above modules can be easily separated from each other or assembled to each other by means of the handling tool and it is possible to perform a remote operation and a remote maintenance. The heater module 200 and the drive module 400 are provided with a plurality connectors 800, and wires (not shown) for supplying electric power to the heater module 200 and the drive module 400 and signal cables (not shown) for controlling the heater module 200 and the drive module 400 are coupled to and decoupled from the connectors 800. FIG. 3 to FIG. 5 are perspective views for illustrating the heater module 200 in the voloxidizer with the double reactor for spent fuel rods decladding according to an embodiment of the present invention, and the heater module 200 is configured to heat the reactor module 300 to 500 to 800° C. for oxidizing the spent fuel rods. In order to perform the above function and to prevent a shape from being largely changed at a high temperature, it is preferable that the heater module 200 be formed of a material having a low thermal expansion coefficient. The heater module 200 includes a first heating body 210 and a second heating body 220, and the first heating body 210 and the second heating body 220 have side walls concaved to an inside to enable the reactor module 300 to be received therein as shown in FIG. 1 and FIG. 2. Therefore, the heater module 200 has a shape in which the reactor module 300 is surrounded, and if the first heating body 210 and the second heating body 220 are slid, the first heating body 210 and the second heating body 220 are coupled to each other in a state where the reactor module 300 is interposed between the two heating bodies and the reactor module 300 is placed in a reactor module through hole 230 formed in the heater module 200. The heater module 200 is placed on a heating body seating plate 250, and the heating body seating plate 250 is composed of a first heating body seating plate 251 on which the first heating body 210 is placed and a second heating body seating plate 252 on which the second heating body 220 is placed. Here, a plurality supporting pieces 253 are formed on a circumference of the heating body seating plate 250 for securing and supporting the heating bodies 210 and 220, and a discharge part through hole 254 through which a discharge part 340 of a reactor 320 (which will be described later) passes is formed at a central portion of the heating body seating plate 250. The heater module 200 is slid by a heating body moving part 240 and a heating body guide part 260, and the heating body moving part 240 is composed of a first rotary knob 241, a first driving gear 242, a first driven gear 243, and a first drive shaft 245 connected to the first driven gear 243. The first drive shaft 245 is connected to first drive shaft connection parts 251a and 252a formed at one side of the heating body seating plate 250. The heating body guide part 260 includes a first sliding plate 261 connected to a lower side of the heating body seating plate 250 in parallel with the first drive shaft 245 and a first sliding guide 262 for guiding the first sliding plate 261. In addition, the first sliding guide 262 is connected to a heating body support plate 270 having an opening formed at a central portion thereof, and transfer rollers 263 are provided at both sides of the heating body support plate 270 to allow the heating bodies 210 and 220 to be smoothly slid. In other words, the heating body seating plate 250 is slid by the heating body moving part 240 along the heating body guide part 260, and the heating bodies 210 and 220 are coupled to each other at both sides of the reactor module 300. As shown in FIG. 2, therefore, in a case in which the reactor module 300 is mounted or decoupled, the first heating body 210 and the second heating body 220 are slid in the opposite directions with respect to a center of the heater module 200, and this sliding is obtained by opposite movements of the first heating body seating plate 251 and the second heating body seating plate 252. FIG. 6 is a perspective view for illustrating the drive module 400 in the voloxidizer with the double reactor for spent fuel rods decladding according to an embodiment of the present invention. The drive module 400 includes a motor 410, a rotary shaft 430 passing through the reactor module 300, and a power transmission part 420 for transmitting a driving force of the motor 410 to the reactor module 300. The power transmission part 420 includes an input part 421 mounted to the motor 410, a delivery part 422 geared with the input part 421, and an output part 423 geared with delivery part 422 and mounted to the rotary shaft 430. Therefore, the motor 410 is operated, a driving force is transmitted to the rotary shaft 430 via the power transmission part 420, and the rotary shaft 430 is rotated so that the reactor 320 placed in the reactor module 300 is rotated. In the power transmission part 420, here, the input part 421, the delivery part 422, and the output part 423 are sequentially and vertically stacked in the direction of gravity. This configuration is devised to prevent a damage of teeth which may occur due to an expansion of the output part 423 mounted to the rotary shaft 430 caused by a high temperature in the reactor module 300 which will be described later. FIG. 7 to FIG. 9 are sectional views for illustrating the reactor module 300 and the utility module 600 in the voloxidizer with the double reactor for spent fuel rods decladding according to an embodiment of the present invention. The reactor module 300 includes a cylindrical body 310, the reactor 320 placed in the body 310, and an input part 330 passing through the body 310 and the reactor 320. Here, an oxidation reaction of the spent fuel rods occurs in the reactor 320. In addition, the reactor 320 includes an internal reactor 321 into which the spent fuel rods are loaded and an external reactor 322 surrounding the internal reactor 321, and the input part 330 is composed of an input tube 331 acting as a passage through which the spent fuel rods are loaded from an outside into the internal reactor 321 and a stopper 332 mounted to the input tube 331. And, the spent fuel rods loaded in the reactor 320 is divided into hulls and pellets through an oxidation process, and the discharge part 340 is formed on the body 310 for discharging the hulls and pellets. The reactor 320 has a cylindrical shape and is surrounded with a mesh 323. Also, a plurality of transport parts 324 having a spiral screw shape are formed on an inner circumferential surface of the reactor 320. The rotary shaft 430 passes through the reactor 320, the reactor is rotated by an operation of the drive module 400, and the spent fuel rods loaded in the reactor 320 are divided into hulls and pellets through the oxidation process performed for 16 hours. Here, a screw blade of a first transport part 324a of the internal reactor 321 is inclined in a direction which is opposite to the direction in which a screw blade of a second transport part 324b of the external reactor 322 is inclined. In this structure, once the reactor 320 is rotated, the spent fuel rods are moved from the other end to one end in the internal reactor 321 and are moved from one end to the other end in the external reactor 322 by the transport part 324. Once the spent fuel rods are moved by the transport part 324, the spent fuel rods may be concentrated in the direction in which the spent fuel rods are moved. In particular, if the spent fuel rods are concentrated in one end portion of the external reactor 322, there is a risk that the spent fuel rods may overflow into the internal reactor 321 through an internal mesh 323a. In order to prevent the above risk, a step portion may be formed on some screw blades of the transport part 324 to prevent the spent fuel rods from being concentrated. In the first transport part 324a, therefore, some screw blades adjacent to one end of the internal reactor 321 have step portions formed thereon, respectively, and when the reactor 320 is rotated in a clockwise direction, a height of the screw blade is decreased by a predetermined value H along the direction in which the spent fuel rods received in the internal reactor 321 are moved. In the second transport part 324b, in addition, some screw blades adjacent to the other end of the external reactor 322 have step portions formed thereon, respectively, and when the reactor 320 is rotated in a counterclockwise direction, a height of the screw blade is decreased by the predetermined value H along the direction in which the spent fuel rods received in the external reactor 322 are moved. In other words, some of screw blades of the first transport part 324a, which are adjacent to the input part 330, have the step portion formed thereon and a height of the screw blade is gradually reduced by the predetermined value H towards the input part 330. Also, some of screw blades of the second transport part 324b, which are adjacent to the drive module 400, have the step portion formed thereon and a height of the screw blade is gradually reduced by the predetermined value H towards the drive module 400. And, during the oxidation process performed in the reactor 320, the reactor 320 is normally rotated in the clockwise direction for 8 hours, and the spent fuel rods loaded in the internal reactor 321 are moved toward the input part 330 by the first transport part 324a and are oxidized. At this time, the spent fuel rods in the internal reactor 321 are moved to the external reactor 322 through the internal mesh 323a by gravity and are fully oxidized in the external reactor 322. Then, once the reactor 320 is reversely rotated in the counterclockwise direction for 8 hours, the oxidized spent fuel rods are moved toward the drive module 400 and divided into pellets and hulls. In other words, when the reactor is normally rotated in the clockwise direction, the spent fuel rods are moved to one end of the internal reactor 321 and are subjected to the oxidation. While the spent fuel rods are being moved toward the one end, the spent fuel rods do not pass through the internal mesh 323a. However, the spent fuel rods moved to the one end of the internal reactor 321 pass through the internal mesh 323a and are finally moved to the external reactor 322 by gravity. And, when the reactor is reversely rotated in the counterclockwise direction, the spent fuel rods moved to the external reactor 322 are moved to the other end of the external reactor 322 and are fully oxidized to be divided into pellets and hulls. Each spent fuel rod is divided into hulls and pellets after performing the oxidation process, hulls and pellets are moved to a hull discharge part 342 and a pellet discharge part 341 constituting the discharge part 340, respectively, and are then collected to a vessel 520 which will be described later. Therefore, the oxidation process for the spent fuel rods is completed. In the reactor module 300, heatsinks 350 are provided at both sides of the body 310 for radiating heat in the body 310 to an outside, and sealing parts 360 are provided at both sides of the body 310 for preventing a high temperature gas in the body 310 from leaking to an outside. The utility module 600 is connected to the reactor module 300 to adjust a state of the reactor module 300, and this utility module 600 includes a thermocouple part 610, a gas removal part 620, and an oxidizer supply part 630. Two thermocouple parts 610 are employed in an embodiment of the present invention, portions of thermocouple parts 610 pass through an upper portion and one side portion of the body 310 of the reactor module 300, respectively. Therefore, it is possible to verify an internal temperature of the reactor module 300 through the thermocouple parts 610. One end portion of each of the gas removal part 620 and the oxidizer supply part 630 is connected to an inner space of the body 310 of the reactor module and the other end portion is exposed to an outside. The gas removal part 620 removes a volatile gas such as krypton (Kr), cesium (Cs), iodine, technetium (Tc), ruthenium (Ru), tritium (H-3), and the like which are in the form of gas and generated from the spent fuel rods during the oxidation process performed at a high temperature. The oxidizer supply part 630 provides a passage for supplying an oxidizer into the body 310. Oxygen (O2) which has been widely used as an oxidizer is employed as the oxidizer in an embodiment of the present invention. FIG. 10 to FIG. 12 are perspective views for illustrating the vessel module 500 in the voloxidizer with the double reactor for spent fuel rods decladding according to an embodiment of the present invention. The vessel module 500 includes a hull vessel 522 for receiving hulls discharged through the discharge part 340, a pellet vessel 521 for receiving pellets, a vessel moving part 510 for moving the vessel 520 toward the discharge part 340, and a vessel guide part 540. Here, in order to secure an air-tightness, a first cylindrical joint tube 531 and a cylindrical second joint tube 532 are mounted to the discharge part 340, and a first insertion part 533a and a second insertion part 533b, which are inserted into the vessel 520, are formed on one side of a joint tube 530. It is preferable that a sealing member (not shown) be provided on an insertion part 533 or an inner circumferential surface of an entrance of the vessel 520 to secure a more reliable air-tightness. The vessel moving part 510 includes a lifting part 512 provided above a vessel moving part support plate 560 and a driving part 511 for generating a driving force for the lifting part 512. And, the driving part 511 includes a second rotary knob 511a, a second driving gear 511b mounted to the second rotary knob 511a, a second driven gear 511c geared with the second driving gear 511b, and a second drive shaft 511d passing through the second driven gear 511c. As shown in FIG. 12, the lifting part 512 includes a vessel mounting part 512c on which the vessel 520 is placed and first and second link parts 512a and 512b connected to the second drive shaft 511d. Here, the first and second link parts 512a and 512b are extended and retracted for enabling the vessel mounting part 512c to be moved upward and downward. The vessel guide part 540 includes a vessel seating plate 541 on which the vessel 520 is placed, and a vessel fixing part 542 for preventing a location of the vessel 520 from being changed when the vessel 520 is slid. In addition, the vessel guide part 540 further includes a second sliding plate 543 coupled to a lower portion of the vessel seating plate 541 in parallel with the second drive shaft 511d; second sliding guides 544 provided at both sides of the lifting part 512 and mounted to first and second vessel support plates 551 and 552 which are connected and perpendicular to the vessel moving part support plate 560; and a grip 545 connected to one side of the vessel seating plate 541. Here, the second sliding plate 543 is slid on the second sliding guides 544. Therefore, after the vessel 520 is secured to the vessel fixing part 542, an operator slides the vessel seating plate 541 using the grip 545 to allow the vessel 520 to be placed below the joint tube 530. Then, the first and second link parts 512a and 512b are extended by an operation of the driving part 511 so that the vessel 520 is attached to the joint tube 530. Once the vessel 520 is filled with hulls and pellets, the first and second link parts 512a and 512b are retracted by an operation of the driving part 511 so that the vessel 520 is decoupled from the joint tube 530. Then, the operator slides the vessel seating plate 541 using the grip 545 to collect the vessel 520. FIG. 13 is a perspective view of the support module in the voloxidizer with the double reactor for spent fuel rods decladding according to an embodiment of the present invention. The support module 100 includes rectangular upper and lower frames 120 and 110 formed by connecting a plurality of frames; side frames 130 connected to corner portions of the upper and lower frames 120 and 110; and middle frames connecting the facing upper frames 120 and the facing lower frames 110. A heater module support frame 160 on which the heating body support plate 270 is placed is placed on the upper frame 120, and a pedestal support frame 150 is placed between the upper frame 120 and the heater module support frame 160. Here, first and second pedestals 151 and 152 are provided at both longitudinal sides of the pedestal support frame 150 for supporting the rotary shaft 430, and semicircular-shaped first and second rotary shaft pedestal parts 153 and 154, which are concaved inward, are formed on the first and second pedestals 151 and 152, respectively. A caster 170 is mounted to each corner of the lower frame 110 for allowing the support module 100 to be easily moved. The voloxidizer with a double reactor for spent fuel rods decladding and the double reactor for use in the same according to an embodiment of the present invention are advantageous in that hulls and pellets separated from the spent fuel rods during the oxidation process for the spent fuel rods can be separately and simultaneously collected so that the collect ratio can be increased. In addition, due to the double mechanism consisting of the internal reactor and the external reactor, oxidation efficiency of pellets is increased so that stable oxide powders can be obtained. The remote operation and remote maintenance can be performed by modularization of parts of the device. The effect obtained by embodiments of the present invention is not limited to the effects mentioned above, and another effect which is not mentioned above may be apparently understood by one skilled in the art through the above detail description. The embodiments described in the above detailed description and the accompanying drawings only exemplarily describe and illustrate a portion of the technical spirit included in embodiments of the present invention. Therefore, since the embodiments disclosed in the detailed description do not limit the technical spirit of the present invention, it is obvious that the technical spirit and scope of the present invention is not limited to the embodiments. While embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
	description	This is a divisional of U.S. patent application Ser. No. 12/887,933, filed Sep. 22, 2010, the contents of which are incorporated by reference. This application is directed toward production and use of radioactive isotopes, or radioisotopes. Radioactive isotopes have many beneficial uses. As one example, positron-emitting copper isotopes, such as copper-64 (64Cu) and copper-60 (60Cu) have a number of uses in clinical and pre-clinical nuclear medicine. These uses include, but are not limited to, the labeling of compounds and the creation of phantom objects suitable for localization and coregistration of multimodality imaging systems, such as those which combine magnetic resonance and positron-emission (MR-PET) imaging. In some instances these radioisotopes are used for oncology imaging and oncological therapy. The production of radioisotopes is one of the factors that limit their use. Production may involve expensive starting materials, such as isotopically enriched substances, and expensive and time-consuming procedures using large, unmovable, and scarce equipment. If a desired radioisotope has a very short half-life it must be used very soon after it is made. This may not be possible unless the radioisotope is made at, or very close to, the location where it is to be used. It may not be economically or physically feasible, however, to have the necessary equipment at or near that location. As an example, 64Cu is produced using either a cyclotron or a nuclear reactor, both of these being large, immobile machines with relatively high operating expenses. A starting material used is Nickel-64 (64Ni), which is a rare isotope requiring expensive enrichment before being transformed into 64Cu. For the particular case of 64Cu, two methods are known for producing this isotope. In one method, 64Ni is bombarded with protons from a particle accelerator. A 64Ni nucleus absorbs a proton and emits a neutron and is thereby transmuted into a 64Cu nucleus. This series of reactions, also referred to as a channel, is designated 64Ni(p,n)64Cu. In a second method, naturally occurring copper is bombarded with neutrons. A 63Cu nucleus absorbs a neutron and is thereby transmuted into 64Cu nucleus. The nucleus is created with excess energy, which it reduces by emitting gamma radiation immediately after the transmutation. This channel is designated 63Cu(n,γ)64Cu. In a variation known as the Szilard-Chalmers effect, a particular atom is a constituent of a molecule dissolved in a liquid. A nuclear reaction involving the nucleus of such atoms results in the nucleus emitting one or more gamma rays, causing a recoil effect in which the atoms, now each transformed into a radioisotope, are ejected from the molecules and into solution in the liquid. The radioisotope atoms may then be chemically or electrolytically extracted from the liquid. Disclosed are method and apparatus for making a radioisotope using a portable neutron source. A material comprising a particular isotope is obtained and exposed to neutrons from a portable neutron source, the particular isotope reacting with a neutron and transforming into the radioisotope. FIG. 1 shows a method of making a radioisotope. A material is obtained which includes a particular isotope which will be transformed into the radioisotope 110. The particular isotope may be present in its natural concentration—the method described here may not require initial enrichment. As an example, naturally occurring copper comprises 69% copper-63 (63Cu) and 31% copper-65 (65Cu). The particular isotope 63Cu, in this naturally occurring abundance, may be transformed, without being enriched, into 64Cu, as described below. The material may be a bulk solid or powdered solid containing the particular isotope. The material may be a pure liquid or a mixture of liquids containing the particular isotope. The material may be a solution of a compound containing the particular isotope, the compound being dissolved in a liquid, solid, or gas. The material may be a gas or vapor including the particular isotope or a mixture of gasses, at least one of which includes the particular isotope. The particular isotope may be a nucleus of a single atom or a nucleus of an atom bound in a molecule. Other appropriate configurations of matter may be considered by one of ordinary skill in the art without departing from the scope of the claims. The material is exposed to neutrons from a portable neutron source 120. A portable neutron source is to be understood as a neutron source that is easily moved between different locations and that occupies a relatively small space, as distinct from, for example, a cyclotron or a nuclear reactor. Examples of known, commercially available portable neutron sources include plutonium-beryllium sources, americium-beryllium sources, deuterium-tritium neutron sources, and californium 252 (252Cf) sources. In a deuterium-tritium source, deuterium gas is ionized, accelerated in an electrostatic field, and allowed to impact on a sealed tritium target, creating neutrons as a result of the t(d,n)4He nuclear reaction. In an americium-beryllium source, alpha particles emitted by the americium react with beryllium nuclei, resulting in the emission of neutrons. A plutonium-beryllium source works in similar fashion with plutonium emitting the alpha particles. 252Cf undergoes spontaneous fission with the emission of a neutron. 252Cf neutron sources are available that emit a total flux of 1011 neutrons per second. Neutron sources can be fabricated in a large range of sizes including portable sizes as described above. For example, 252Cf neutron sources shaped as cylinders, including ones with outer diameter 5.5 mm and outside length 25 mm, are available from Frontier Technology Corporation, Xenia, Ohio. The portable neutron source may be situated within the material. The portable neutron source may be completely surrounded by the material. Alternatively, at least a portion of the portable neutron source may be situated outside the material. Nuclei of the particular isotope react with neutrons from the portable neutron source 120 resulting in the particular isotope transforming into the desired radioisotope. The transformation may occur through any of several different reaction paths, or channels, such as those described below. After the material has been exposed to the neutrons 120 for a time sufficient to produce a desired quantity of the radioisotope, the radioisotope may be extracted from the material 130. Extraction 130 may be carried out by, for example, chemical methods known to those of ordinary skill in the art for the particular element in question. Alternatively, the radioisotope may be left within the material. The material may then be used as a source of the radiation emitted by the radioisotope. FIG. 2 shows an embodiment of an apparatus 200 for producing a radioisotope using a portable neutron source 240 in proximity to a container 220. Container 220 contains a material 210 which includes a particular isotope 250. Portable neutron source 240 is shown completely surrounded by material 210. Alternatively, at least a portion of portable neutron source 240 may be situated outside material 210. Portable neutron source 240 emits neutrons 260 into material 210. Neutrons 260 emerging from portable neutron source 240 may have energies in excess of thermal energy of material 210, as depicted by thick arrows. These neutrons 260 are known as fast neutrons. Within a short distance of portable neutron source 240, several centimeters for example, fast neutrons 260 may slow down and come into thermal equilibrium with material 210 after undergoing many collisions with atoms or molecules in material 210. These slower neutrons 230, depicted by thin arrows, are known as thermalized neutrons or thermal neutrons. Neutrons from portable neutron source 240, either fast neutrons 260 or thermal neutrons 230, may then react with the nuclei of a particular isotope 250, represented by filled-in circles, included in material 210. As a result, the nuclei of particular isotope 250 are transformed into nuclei of a desired radioisotope 270, represented by unfilled circles. Depending on neutron cross-sections and neutron reaction dynamics for particular isotope 250, either fast neutrons 260 or thermal neutrons 230 or both may contribute significantly to formation of radioisotope 270. Material 210 may be a bulk solid or powdered solid containing particular isotope 250. Material 210 may be a pure liquid or a mixture of liquids containing particular isotope 250. Material 210 may be a solution of a compound, the compound containing particular isotope 250. The compound may be dissolved in a liquid, in a solid, or in a gas. Material 210 may be a gas or vapor including particular isotope 250 or a mixture of gasses, at least one of which includes particular isotope 250. Particular isotope 250 may be a nucleus of a single atom or a nucleus of an atom bound in a molecule. A portion of material 210 may act as a moderator that reduces energy of neutrons emitted from portable neutron source 240. Such moderated neutrons may be slowed down to energies less than energies with which they are emitted. The neutrons may be thermalized in this way. For example, if particular isotope 250 is in a water solution, the water may act as a moderator. Thus, portable neutron source 240 may be completely surrounded by both particular isotope 250 and by a moderator. This geometry is shown in the embodiment illustrated in FIG. 2. Other appropriate states of matter and other geometrical configurations may be considered by one of ordinary skill in the art without departing from the scope of the claims. Once a desired amount of particular isotope 250 has been transformed into radioisotope 270, the latter may be separated from material 210 by, for example, chemical or physical methods known to those of ordinary skill in the art. As an example, if radioisotope 270 can be ionized in solution it may be separated by electroplating. Alternatively, the separation may be carried out using separate extraction apparatus known as a chemistry kit (not shown). The chemistry kit may be integral with apparatus 200. Alternatively, radioisotope 270 may be left within the material. The material may then be used as a source of the radiation emitted by the radioisotope. As examples not to be considered limiting, the method, apparatus, and composition of matter described above may be applied to the production of the copper isotope 64Cu. In a particular embodiment, portable neutron source 240 may be a plutonium-beryllium (Pu—Be) source, an americium-beryllium (Am—Be) source, a deuterium-tritium (D—T) source, a 252Cf source, or another portable neutron source. Material 210 may be an aqueous solution of a copper-containing compound such as copper phthalocyanine, or copper salicylaldehyde o-phenylene diamine. The compound may contain copper isotopes in their natural abundances, which are 69% 63Cu and 31% 65Cu. The 63Cu may serve as particular isotope 250. Thermal neutrons 230 may react with the 63Cu particular isotopes 250 which transform into 64Cu as an example of formed radioisotope 270. In this embodiment the 64Cu radioisotope is produced by the 63Cu(n, γ)64Cu reaction, in which a 63Cu nucleus absorbs a neutron to become 64Cu, emitting a γ photon in the process. Experiments in which a copper-containing solid was bombarded with thermal neutrons have yielded about 50 nanoCuries of 64Cu. By using a stronger portable neutron source and a geometry such as that shown in FIG. 2, it is estimated that 100-1000 times as much 64Cu—that is to say a large number of microCuries—may be generated in this manner. Materials including radioisotopes made using the method and apparatus described above may be shaped into objects with geometrical shapes such as markers, arrows, right-left designating shapes, text, and numbers. Such objects may be used in medical imaging for image registration, aligning, testing, and labeling. In particular, objects that include the positron-emitting isotope 64Cu may be useful in positron-emission tomography (PET) imaging. Compared with currently known technologies for making radioisotopes, the method, apparatus, and composition of matter described above, making use of a portable neutron source, present possibilities for making radioisotopes less expensively with equipment taking up much less space. Also presented is the possibility of making radioisotopes with short half lives at the location where they are needed, such as a hospital. In this way, a larger number of useful radioisotopes may become available to a practitioner, such as a physician. While the preceding description refers to certain embodiments, it should be recognized that the description is not limited to those embodiments. Rather, many modifications and variations may occur to a person of ordinary skill in the art which would not depart from the scope and spirit defined in the appended claims.
	abstract	An energy modulator for use with a particle source that provides a beam of particles includes a first block moveable between a first position and a second position, wherein when the first block is at the second position, it is in a path of the beam, and a second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam, wherein the first block has a first energy absorption characteristic, and the second block has a second energy absorption characteristic that is different from the first energy absorption characteristic.
061954055	abstract	A gap forming structure for use with water cooled nuclear reactors is invented to prevent overheating and ultimately structurally failing of the lower head of a reactor vessel in a nuclear reactor core meltdown accident by virtue of a cooling effect in the gap structure for facilitating the retention of accumulated molten core debris. Single layer or multilayer gap structures can be installed either inside or outside the vessel lower head by joining, or fastening structures or secured to the instruments/control guide tubes within the vessel. The water cooling capacity inside the gap can prevent the vessel lower head from overheating and subsequently failing and thus defend against severe accidents by preventing the lower head of the reactor vessel from rupturing.
	abstract	A method for dismantling a steam generator or heat exchanger, such as found in nuclear power plants, which steam generator or heat exchanger includes a plurality of primary circuit tubes with a contaminated inner surface and wherein one or more tubes are sealed with a plug at both end is provided, the method comprising a) opening one or both ends of each sealed tube by creating an opening in or removing, the plug (13); b) introducing a viscous polymer to cure inside the tube wherein the polymer fills the tube across the full tube cross-section at least at the tube ends, immobilizing contaminations in the filled portion inside the tube (11); c) curing the polymer, then detaching the tubes with cured polymer the detached tubes being sealed by the polymer d) sorting out the detached tubes with polymer.
	claims	1. A uranium oxide fuel pellet comprising an inner region and an outer rim region about the inner region, and that the fuel pellet is cylindrical and the inner region and outer rim region are coaxial cylindrical regions, wherein the outer rim region has an excess of oxygen in comparison to the inner region, wherein high burnup structure (HBS) formation will be suppressed or delayed, and wherein said excess oxygen in the outer rim region of the pellet is 5% extra O, by molar content. 2. The uranium oxide fuel pellet according to claim 1, wherein the excess of oxygen is obtained by adding oxygen only to the outer rim region of the pellet. 3. The uranium oxide fuel pellet according to claim 1, wherein the excess oxygen is obtained by a chemical treatment by immersing the pellet in hydrogen peroxide (H2O2) in solution. 4. The uranium oxide fuel pellet according to claim 1, wherein the excess oxygen is obtained by a chemical treatment by immersing the pellet in potassium permanganate (KMnO4) in solution. 5. The uranium oxide fuel pellet according to claim 1, wherein the outer rim region has a maximum thickness of 100 μm. 6. A fuel rod comprising a cladding tube in which a plurality of uranium fuel pellets according to claim 1 are packed in axial alignment. 7. The fuel rod according to claim 6, wherein the cladding tube is at its inner surface provided with an oxide coating, and wherein said oxide coating is obtained by a chemical treatment by immersing the cladding tube in hydrogen peroxide (H2O2) or potassium permanganate (KMnO4) in solution. 8. A fuel rod assembly comprising a plurality of fuel rods according to claim 6. 9. A method of preparing a uranium oxide fuel pellet comprising an inner region and an outer rim region about the inner region, and that the fuel pellet is cylindrical and the inner region and the outer rim region are coaxial cylindrical regions, wherein the method comprises providing an excess of oxygen in the outer rim region in comparison to the inner region, wherein high burnup structure (HBS) formation will be suppressed or delayed, and wherein said excess oxygen in the outer rim region of the pellet is 5% extra O, by molar content. 10. The method according to claim 9, comprising immersing the pellet in hydrogen peroxide (H2O2) in solution for obtaining the excess oxygen by a chemical treatment by. 11. The method according to claim 9, comprising immersing the pellet in potassium permanganate (KMnO4) in solution for obtaining the excess oxygen by a chemical treatment. 12. The method according to claim 9, comprising adding the excess oxygen after the pellet has been formed and ground. 13. A method in relation of a fuel rod comprising a plurality of uranium fuel pellets obtained by the method according to claim 9, and providing a cladding tube in which said fuel pellets are intended to be packed in axial alignment, and wherein the method comprises providing an oxide coating at the inner surface of the cladding tube. 14. The method according to claim 13, comprising providing the oxide coating by a chemical treatment by immersing the cladding tube in hydrogen peroxide (H2O2) or potassium permanganate (KMnO4) in solution.
	abstract	A mirror, in particular for a microlithographic projection exposure apparatus has an optically effective surface, wherein the mirror has a reflectivity of at least 0.5 for electromagnetic radiation which has a prescribed working wavelength and impinges on the optically effective surface at an angle of incidence based on the respective surface normal of at least 65°, wherein the mirror has at least one layer (160, 170, 320) which comprises a compound of an element of the second period and an element of the 4d transition group, wherein the mirror has a protective layer (430, 530, 630, 730) arranged on top in the direction of the optically effective surface, wherein the material of the layer (420, 510, 620, 705) arranged in each case underneath the protective layer in the direction of the optically effective surface has a lower absorption than the material of the protective layer (430, 530, 630, 730).
	description	This application is a divisional under 35 U.S.C. § 121 of U.S. application Ser. No. 13/721,346, filed Dec. 20, 2012, the entire contents of which is incorporated herein by reference. The present disclosure relates to the reduction or prevention of the entrainment of gases into the suction of a pump during a loss of coolant accident (LOCA). During a Loss of Coolant Accident (LOCA), the Emergency Core Cooling System (ECCS) must pump water to maintain the reactor core water level and to provide a cooling function to the reactor core. However, this same transient may cause gases to be forced downward into an operating Emergency Core Cooling System (ECCS) suction strainer, resulting in gas entrainment. In particular, during a Loss of Coolant Accident (LOCA), both condensable gases (e.g., steam) and non-condensable gases (e.g., nitrogen (N2)) may be directed into a suppression pool, thereby elevating the level of the suppression pool. An Emergency Core Cooling System (ECCS) pump may be used to maintain the suppression pool at an acceptable level by suctioning excess liquid from the suppression pool and supplying the excess liquid to the reactor core. However, the non-condensable gases may become entrained along with the liquid into the suction of the Emergency Core Cooling System (ECCS) pump, thereby causing loss of suction and decreased flow to the reactor core. Furthermore, the presence of non-condensable gases within the Emergency Core Cooling System (ECCS) pump causes cavitation and pump damage, which poses additional safety hazards. The present disclosure describes various devices, assemblies, systems, and methods for preventing pumps (e.g., Emergency Core Cooling System (ECCS) pumps) from receiving relatively large quantities of entrained gas in the suction piping, which would cause cavitation and ultimately result in the failure of the pump. The teachings herein also promote the mitigation or prevention of non-condensable gases from reaching the suction strainers within the wetwell. Specially-designed deflector shields or baffles may be arranged between the drywell-to-wetwell vent downcomer and the Emergency Core Cooling System (ECCS) pump suction strainer. By preventing gases from the reaching the Emergency Core Cooling System (ECCS) suction water, the availability of pump operation for the duration of a postulated accident may be increased. An entrainment-reducing assembly may include a container configured to hold a liquid. The container may include an upper portion and a lower portion. A venting arrangement may extend into the container. The venting arrangement may be configured to direct gases into the container. A suction structure may extend into the lower portion of the container. The suction structure may be configured to carry out an extraction of the liquid from the container. A deflector may be disposed between the suction structure and the venting arrangement within the container. The deflector may be configured to reduce the entrainment of uncondensed gases during the extraction of the liquid. A reactor system may include a first container and a second container. The first container may define a drywell therein. The second container may define a wetwell therein. The second container may include an upper portion and a lower portion. A venting arrangement may connect the drywell to the wetwell. The venting arrangement may include a proximal end extending into the drywell and a distal end extending into the upper portion of the wetwell. A suction structure may extend into the lower portion of the wetwell. A deflector may be disposed between the suction structure and the distal end of the venting arrangement within the second container. A method of reducing entrainment may include discharging gases from a venting arrangement into a liquid. The method may additionally include alleviating an elevated level of the liquid resulting from condensing gases by performing an extraction of the liquid with a suction structure. The method may further include shielding the suction structure from the entrainment of uncondensed gases in the liquid with a deflector during the extraction of the liquid. 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. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Various embodiments of the present disclosure relate to devices and assemblies, which when used inside a nuclear reactor (e.g., Boiling Water Reactor (BWR) Mark I or Mark II wetwells (torus)), will mitigate or solve the issue of “loss of suction” to Emergency Core Cooling System (ECCS) pumps due to the entrainment of steam and/or non-condensable gases during a Loss of Coolant Accident (LOCA) in the drywell. Various embodiments of the present disclosure also relate to systems and methods for reducing the entrainment of gases. Although the description herein is in the context of a Boiling Water Reactor (BWR), it should be understood that example embodiments are not limited thereto. In addition to the various types of Boiling Water Reactors (BWR), the present disclosure may also be applied to Pressurized Water Reactor (PWR) emergency water sumps with suction strainers. Furthermore, the teachings herein may be applied to non-reactor settings. For instance, the devices, assemblies, systems, and methods may be used in other situations in which a suction is taken from a large reservoir of liquid (e.g., water), whereupon a large injection of non-condensable gases could result in these gases being entrained or swept into the suction pipe, thereby causing the downstream pump to fail. FIG. 1 is a simplified, cross-sectional view of a reactor system according to a non-limiting embodiment. Referring to FIG. 1, a reactor system 100 includes a first container 102 defining a drywell 104 and a second container 108 defining a wetwell 110. A reactor pressure vessel 106 is situated within the drywell 104. A body of liquid 112 (e.g., suppression pool) is disposed within the wetwell 110. The drywell 104 is connected to the wetwell 110 via a venting arrangement 114. The details of FIG. 1 are discussed in connection with the subsequent drawings. The present disclosure details the mitigation or prevention of gases from being entrained in the suction of Emergency Core Cooling System (ECCS) pumps. Such mitigation or prevention may improve the safety operation and availability of the Emergency Core Cooling System (ECCS) pumps during a Loss of Coolant Accident (LOCA). In particular, a relatively large Loss of Coolant Accident (LOCA) may force gas into the Emergency Core Cooling System (ECCS) piping. A relatively large gas entrainment may lead to gas entering an Emergency Core Cooling System (ECCS) pump, resulting in pump damage from cavitation and reduced flow (if any flow at all) to the reactor core. Consequently, the ability of the Emergency Core Cooling System (ECCS) pumps to maintain the proper water level in the reactor core may be affected. That being said, the present disclosure is directed to mitigating or preventing the possibility of gas reaching the suction of the Emergency Core Cooling System (ECCS) piping. A centrifugal pump is used in the Emergency Core Cooling Systems (ECCS) of Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR). A centrifugal pump requires a net positive suction head (NPSH) at a given location relative to a reference point as defined by the following equation: NPSH = P o - P v ρ ⁢ ⁢ g + Δ ⁢ ⁢ z - h L ( 1 ) wherein P0 is the pressure acting upon the fluid at the reference point, Pν is the saturation pressure for the fluid at the current temperature, ρ is the fluid density, g is gravitational acceleration, Δz is the height difference from the current point to the reference point, and hL is the head loss between the two points. If a centrifugal pump does not have a sufficient net positive suction head (NPSH), then low or no flow, pump wear, and in the worst case, seizing of the pump will result. During a Loss of Coolant Accident (LOCA), as will be explained, gases (e.g., non-condensable nitrogen, which was previously used to inert the drywell, and steam, resulting from the flashing flow from a design basis line break) can be forced through the suction strainer in the wetwell (e.g., torus-shaped wetwell) and then into the Emergency Core Cooling System (ECCS) suction header and finally into the pump. Depending on the anticipated Emergency Core Cooling System (ECCS) configuration and potential active failures, the ranges of flow1 in an Emergency Core Cooling System (ECCS) header range from 600 to 30,000 gal/min (5,010 to 417,000 lbs/min). With a ring header diameter of 2 feet, this results in a Reynolds number ranging from 105 to 107. Reynolds number2* is the ratio of inertial forces within a fluid to its vicious forces and is defined by the following equation: Re = QD vA ( 2 ) wherein Q is the Emergency Core Cooling System (ECCS) flow rate, D is the hydraulic diameter, ν is the kinematic viscosity, and A is the cross-sectional area of the ring header. 1Assuming RCIC˜600 gpm, HPCS (BWR/5 s and 6 s)˜7,175 gpm, Low pressure systems that take SP suction: LPCI˜4 pumps8400 gpm/pump=33,600 gpm, LPCS˜2 pumps8400 gpm/pump=16,800 gpm.2Assuming Viscosity at 100° F.=4.579E-4 lbm/ft/s; Density at 100° F.=8.34 lbm/gallon; Kinematic viscosity=4.579E-4/8.3460=0.003294 gal/ft/min; D=2 ft; D/A=D/(¼ pi D2)=4/(pi D)=0.6366 1/ft; Re=Q [gal/min]193.2 min/gal. Due to the relatively high Reynolds number, the flow regime is highly turbulent and the inertial force dominates over buoyant forces of gas entrained in the water. Therefore, to remove entrained gases from the water the Reynolds number needs to reach a value below 1000, so that buoyancy of the entrained gas can allow phase separation. Even at a Reynolds number of about 100, a wobble occurs that causes bubbles to rise in a spiral or helical path. This velocity of the fluid can occur with expansion of the flow area and is enhanced with flow direction changes. These entrained air bubbles in the pool will take much longer to rise to the surface because of the viscosity of the water. Air bubbles will rise and achieve a terminal velocity governed by Stoke's law. FIG. 2 is cross-sectional view of an entrainment-reducing assembly according to a non-limiting embodiment that may be used in the reactor system of FIG. 1. Although the entrainment-reducing assembly of FIG. 2 is shown in connection with a Boiling Water Reactor (BWR) Mark I suppression pool, it should be understood that example embodiment are not limited thereto. Referring to FIG. 2, the entrainment-reducing assembly 200 includes the second container 108, which defines the wetwell 110 and holds the body of liquid 112 (e.g., suppression pool of water) therein. The venting arrangement 114 connects the drywell 104 (FIG. 1) to the wetwell 110. The venting arrangement 114 includes a vent pipe 202, a header 204, and a plurality of downcomers 206. A suction structure 212 protrudes into the second container 108 at a position below the surface of the liquid 112. The suction structure 212 includes a suction pipe 214 and a strainer 216 secured to the suction pipe 214. The strainer 216 may have a variety of configurations and shapes and is designed to allow the liquid 112 to enter with relative ease while filtering out relatively large-sized debris. A deflector 210 is arranged between the suction structure 212 and the venting arrangement 114 to deflect uncondensed gas 208 away from the suction structure 212 so as to reduce or prevent the entrainment of the uncondensed gas 208 with the liquid 112. A spacing distance between the deflector 210 and the suction structure 212 may be equal to or less than half of a total distance between the venting arrangement 114 and the suction structure 212. The deflector 210 may be secured to the second container 108 such that the deflector 210 does not directly contact the suction structure 212. After passing through the strainer 216 and entering the suction pipe 214, the liquid 112 is directed through the suction line to a pump. Optionally, a gas/liquid separator may be additionally connected to the suction line to separate out any uncondensed gases that may have been entrained with the liquid 112. The gases may be separated based on density, and the separated gases may be redirected back into the wetwell 110. The common term for a Mark I wetwell is a torus, since the second container 108 defining the wetwell 110 may be in the form of a torus. When the second container 108 is in a form of a torus, eight vent pipes 202 may connect the drywell 104 to the wetwell 110. In such an example, the header 204 may be in form of a ring within the torus that connects the vent pipes 202. In addition to the vent pipes 202, the gas flow from the drywell 104 is further divided by a plurality of downcomers 206 which discharge the gas below the surface of the liquid 112 (e.g., subcooled water). Steam quenchers may be optionally attached to the downcomers 206. The strainer 216 is positioned so as to remain submerged near the bottom of the second container 108. The liquid 112 is removed from the wetwell 110 via the suction structure 212 and is conveyed through the suction pipe 214 to the Emergency Core Cooling System (ECCS) pumps. The deflector 210 is positioned between the strainer 216 and the downcomer 206 to reduce or prevent the entrainment of an uncondensed gas 208 into the suction line. Although not shown in the drawings, it should be understood that a suction structure 212 and/or a deflector 210 may be provided for each downcomer 206. The entrainment-reducing assembly 200 will be described in additional detail with regard the following three states: normal operations “Steady State,” a state after a “Large LOCA” in the drywell, and the resulting system transient “Gas to ECCS Pumps” state. A “Steady State” assumes that the reactor is at normal operating temperature and pressure and assumed at 100% power. In such a state, the liquid 112 in the wetwell 110 is at a normal level. During a “Large LOCA” state, there is a break at rated power, which involves an instantaneous rupture of a steam or recirculation line in the dry well 104. As a result of the rupture, a shock wave exits with a wave amplitude approaching the reactor operating pressure (e.g., 1000 psig). The attenuated wave enters the venting arrangement 114 and progresses into the wetwell 110. The high pressure gases (e.g., N2 and steam) from the drywell 104 are forced downward through the venting arrangement 114. The high pressure gases exit the downcomer 206 and set off several phenomena, such as pool swell in the torus increasing from the steady state (normal) level to an elevated level, condensation oscillation as the steam chaotically condenses and pool water voids, and forcible downward direction of the gas mixture. In a conventional system, if the Emergency Core Cooling System (ECCS) suction strainer is located in the vicinity of the downcomer nozzle, the gas jet can be forced into the suction strainer, thereby introducing a slug of gas into the Emergency Core Cooling System (ECCS) header. If the Emergency Core Cooling System (ECCS) pumps have already been activated, with water flow from the wetwell established, this slug of gas can move into the Emergency Core Cooling System (ECCS) pump, resulting in reduced pump flow, cavitation, and/or pump damage. In contrast, in the present disclosure, a deflector 210 is in place as the gas jet is forced towards the strainer 216. As a result, the deflector 210 deflects the gas flow, thereby allowing for buoyancy effects to permit the gas to separate and rise to the headspace of the wetwell 110. The strainer 216 under the deflector 210 still maintains suction of the liquid 112 from the wetwell 110. Additionally, as schematically shown in FIG. 2, gas/liquid separator may be used to remove gas that may have become entrained with the liquid 112 into the Emergency Core Cooling System (ECCS) suction line. The gas that is removed from the suction line may be put back into the headspace of the wetwell 110. FIG. 3 is a cross-sectional view of a deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. Referring to FIG. 3, the deflector 210 may include a first surface 302a with a first ridge 304a and a second surface 302b with a first furrow 304b. When installed in the entrainment-reducing assembly 200, the first furrow 304b will face the strainer 216, while the first ridge 304a will face the downcomer 206. A first angle α1 of the first furrow 304b, as defined by the second surface 302b, should be of a magnitude that is sufficient to cause the uncondensed gas 208 of the impinged two phase jet hitting the deflector 210 to be deflected upward towards the surface of the wetwell liquid 112 to inhibit or prevent the uncondensed gas 208 from entering the strainer 216 and to allow for a separation when the uncondensed gas 208 reaches the headspace of the wetwell 110. In a non-limiting embodiment, the first angle α1 may range from about 155° to 170°. The deflector 210 may optionally have a periphery 308 that slopes away from the suction structure 212 so as to form a second ridge 310a and a second furrow 310b, wherein the periphery 308 enhances the deflection of the uncondensed gas 208 away from the suction structure 212. A second angle α2 of the second furrow 310b may range from 155° to 180°. Although not shown, it should be understood that the second ridge 310a and/or the second furrow 310b may be curved instead of being angular. The deflector 210 may also include a plurality of perforations 306 extending from the first surface 302a to the second surface 302b. The plurality of perforations 306 allow the liquid 112 to flow through the deflector 210, thereby reducing the differential force across the deflector 210 and allowing the liquid 112 to enter the strainer 216. The plurality of perforations 306 may be angled inward toward the suction structure 212 and/or the first furrow 304b so as to allow entry of the liquid 112 while deflecting the uncondensed gas 208 away from the suction structure 212. In FIG. 3, assuming that A-A is a center line that bisects the deflector 210 and B-B is a line that corresponds to a longitudinal axis of the perforation 306 and intersects A-A to form a third angle α3, the third angle α3 may range from about 45° to 135° (e.g., 60° to 90°). The diameter of each of the plurality of perforations 306 may be sized to be about two times the average expected bubble size of the uncondensed gas 208 impinging on the deflector 210. As noted above, the plurality of perforations 306 are at a third angle α3 that reduces or prevents bubble entrainment as the two phase jet impinges on the first surface 302a. The amount of uncondensed gas 208 entrained through the plurality of perforations 306 is a function of perforation diameter, perforation length, and the water flow rate. A method to optimize the diameter of the perforations 306 use the Froude number (Fr): Fr = V L / g ⁡ ( ( ρ l - ρ G ) ρ l ) ⁢ D ( 3 ) wherein VL is the liquid velocity in the perforations, g is the acceleration due to gravity, ρl is the density of the liquid, ρG is the density of the gas, and D is the inside diameter of the perforations. The Froude number (Fr) should be a value that gives the uncondensed gas 208 an adequate opportunity to be deflected and rise toward the headspace of the wetwell 110. In a non-limiting embodiment, Fr<0.31. Although the perforations 306 have been discussed in the context of a circular hole, it should be understood that example embodiments are not limited thereto. For instance, the perforations 306 may be in the form of other curved shapes or polygonal shapes (e.g., slits) FIG. 4A is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. FIG. 4B is a plan view of the deflector of FIG. 4A. Referring to FIGS. 4A-4B, the deflector 210 is in the form of a bent sheet 210a including a first ridge 304a and a first furrow 304b. Although not shown, it should be understood that one or more of the features discussed in connection with FIG. 3 may be applied to this example. FIG. 5A is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. FIG. 5B is a plan view of the deflector of FIG. 5A. Referring to FIGS. 5A-5B, the deflector 210 is in the form of a curved shield 210b including a convex side 504a and a concave side 504b. Although not shown, it should be understood that one or more of the features discussed in connection with FIG. 3 may be applied to this example. FIG. 6A is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. FIG. 6B is a plan view of the deflector of FIG. 6A. Referring to FIGS. 6A-6B, the deflector 210 is in the form of a curved-type louvered arrangement 210c including a first curved portion 600a, a second curved portion 600b, and a third curved portion 600c. The second curved portion 600b and a third curved portion 600c are provided with an opening in the center thereof such that when arranged with the first curved portion 600a into an overlapping louvered arrangement, the first curved portion 600a and the second curved portion 600b define a first passage 606a therebetween, while the second curved portion 600b and the third curved portion 600c define a second passage 606b therebetween. Although not shown, it should be understood that one or more of the features discussed in connection with FIG. 3 may be applied to this example. FIG. 7A is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. FIG. 7B is a plan view of the deflector of FIG. 7A. Referring to FIGS. 7A-7B, the deflector 210 is in the form of a linear-type louvered arrangement 210d including a first slat 700a, a second slat 700b, and a third slat 700c. When arranged in an overlapping louvered arrangement, the first slat 700a and the second slat 700b define a first slit 706a therebetween, while the second slat 700b and the third slat 700c define a second slit 706b therebetween. Although not shown, it should be understood that one or more of the features discussed in connection with FIG. 3 may be applied to this example. FIG. 8A is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of FIG. 2. FIG. 8B is a plan view of the deflector of FIG. 8A. Referring to FIGS. 8A-8B, the deflector 210 is in the form of a radially-configured corrugated sheet 210e including a plurality of alternating radially-oriented ridges 804a and radially-oriented furrows 804b that expand outward radially from a point of common convergence 802. Although not shown, it should be understood that one or more of the features discussed in connection with FIG. 3 may be applied to this example. 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 multi-leaf collimator device for radiotherapy, comprising:a frame that has a box shape and through-holes formed in top and bottom surfaces thereof;a plurality of collimators that are received in the frame, wherein each of the collimators comprises a rack gear formed on a top surface of the collimator, and the collimators are symmetrically arranged in a left-right direction about a central portion of to the frame and are slidably provided on the frame; anda motion driving unit that comprises a pinion gear that is formed to be detachable from the rack gear formed on the top surface of the collimator, and is provided on the frame to move the pinion gear in a front-back direction of the frame and a up-down direction of the frame. 2. The multi-leaf collimator device of claim 1, wherein two motion driving units are symmetrically arranged in the left-right direction of the frame. 3. The multi-leaf collimator device of claim 1, wherein the motion driving unit comprises:a ball screw that extends in a direction perpendicular to a direction in which the collimator slides;a first motor that is coupled to an end portion of the ball screw;a ball nut that is coupled to the ball screw;a moving member that is fixed to the ball nut;an elevation member that is elevatably coupled to the moving member;the pinion gear that is provided on a lower end portion of the elevation member to be rotatable relative to the elevation member;a pulley that is integrally coupled to a rotational shaft of the pinion gear;a second motor that is fixed to an upper end portion of the elevation member; anda timing belt that connects a rotational shaft of the second motor and the pulley. 4. The multi-leaf collimator device of claim 3, further comprising a linear motion guide that is disposed parallel to the ball screw such that the moving member is slidable. 5. The multi-leaf collimator device of claim 3, wherein the elevation member is elevatable by using air pressure. 6. The multi-leaf collimator device of claim 5, wherein the motion driving unit is controlled by a computer.
	abstract	A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
056028873	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS During the installation procedure, the tie rod/lower spring assembly (items 54 and 56 in FIG. 2) is lowered into the downcomer annulus 8. This is accomplished using a crane (not shown) on the refueling floor of the reactor. First, the tie rod/lower spring assembly must be raised from horizontal position on the refueling floor to a vertical position suspended from the end of the crane cable. This is accomplished by means of a tie rod adaptor which couples the upper end of the tie rod to the end of the cable. When the cable is wound, the upper end of the tie rod is lifted off the refueling floor into an upright position with all of the weight of the tie rod being supported by the cable. The tie rod/lower spring assembly can then be lowered into the annulus by unwinding the cable. Referring to FIG. 2, when vertical access to the downcomer annulus 8 is limited by internal reactor structures such as the feedwater sparger 26 and core spray header 28, a rigid frame or strongback 90 can be used to bypass the obstruction. The strongback is designed to circumvent the piping obstructions so that the tie rod/lower spring assembly is freely suspended from the end of the cable and the cable remains plumb. The tie rod strongback 90 is suspended from cable 84 via a cable adaptor 86 at its upper end. The lower end of the strongback 90 is coupled to the tie rod adaptor 88, which in turn couples to the top of the tie rod 54. As the cable is lowered, the tie rod/lower spring assembly 54/56 must be guided into the narrow space between adjacent jet pump assemblies 44a and 44b (see FIG. 2). Maneuvering of the tie rod/lower spring assembly must be done with extreme care to avoid damaging reactor hardware such as the jet pump restrainer brackets 48a, 48b and the jet pump sensing lines (not shown). In a specific application, the bottom end of the assembly is displaced radially inward until the clevis hook clears the clevis pin installed on the gusset plate. Then the tie rod assembly is lowered a few inches until the tip of the clevis hook clears the bottom of the clevis pin. During this brief descent of the tie rod assembly, it slides against the saddle of the pusher tool. The saddle is made of ultra-high-molecular weight (UHMW) polyethylene or other suitable material to prevent scratching of the tie rod assembly. Alternatively, only the surface layer of the saddle is made of UHMW polyethylene. When the pressurized fluid to the spreader is cut off, the suspended tie rod assembly drifts radially outward, causing the clevis pin to enter the clevis hook. Then the tie rod assembly is lifted to fully engage the clevis pin in the clevis hook prior to installing a vertical support tool which braces the clevis hook against the clevis pin from below. Ultimately, the assembly is positioned so that it hangs plumb over the gusset plate 18. At this juncture, the tie rod/lower spring assembly must be maneuvered so that the clevis hook 56c is hooked underneath the clevis pin 20 on the gusset plate 18, as seen in FIG. 3. To accomplish this, the clevis hook at the bottom of the suspended assembly must be displaced radially inward in the downcomer annulus until there is radial clearance vis-a-vis the clevis pin. With the clevis hook in this radially inwardly displaced position, the tie rod assembly is lowered a few inches until the tip T of the clevis hook 56c clears the bottom of the clevis pin 20. Then the force displacing the bottom end of the suspended tie rod assembly radially inward is removed, allowing the lower spring clevis 56c to "drift" under the clevis pin 20 until the latter contacts the inclined surface S of the clevis hook slot. The tie rod assembly is now properly positioned and simply lifted up to fully engage the clevis pin 20 in the clevis hook. Referring to FIGS. 4A and 4B, the pusher tool 100 in accordance with one preferred embodiment of the invention comprises a pole adaptor 102 for coupling to the end of a service pole (not shown). In particular, the pole adaptor 102 has a pair of J-shaped slots 102a (only one of which is visible in FIG. 4A) for receiving respective pins on the end of the service pole (not shown). Pusher tool 100 further comprises a pole adaptor extension 104, the upper end of which is attached to the pole adaptor 102. Preferably, extension 104 is a rod made of aluminum alloy. The lower end of extension 104 has a clevis which is coupled to a support post 108 by a clevis pin 106, as best seen in FIG. 4B. The clevis arrangement allows the extension 104 and support post 108 to articulate, which facilitates passage of the tool through tight spots in the annulus during insertion and removal. The support post 108 is securely mounted on a mounting channel 110. In particular, the support post can be inserted in a pair of coaxial holes (not shown) formed in the arms of the channel 110. The support post and channel are also preferably made of aluminum alloy. The arms of channel 110 may optionally have contoured reaction surfaces which conform to the contour of the cladded surface 11 of the RPV wall 10, which the channel is placed in contact with, as seen in FIG. 5. The face of the channel 110 is preferably planar and supports a hydraulic spreader or pry bar. The hydraulic spreader, which resembles a duckbill, has a fixed member or jaw 112 attached to the mounting channel 110 by screws 134 and a pivoting member or jaw 114 which is pivotably coupled to the fixed member 112 by means of a pivot pin 116. The pivoting member 114 pivots relative to the fixed member 112 about an axis which lies generally parallel to the flat face of mounting channel 110 in response to the supply of pressurized fluid, e.g., water, to a hydraulic cylinder 118 situated between the fixed and pivoting members. Hydraulic cylinder 118 is arranged such that the pivoting member 114 is pushed open when the piston of the hydraulic cylinder is extended. The hydraulic cylinder 118 is connected to a source (not shown) of pressurized fluid via a hydraulic line 122 and a quick disconnect coupling 124. The piston of hydraulic cylinder is extended when pressurized fluid, e.g., water, is supplied to the cylinder and retracted when the supply of pressurized fluid is cut off. The end of the piston contacts the pivoting member 114 of the hydraulic spreader at a point which is offset from the axis of pivot pin 116. Thus, extension of the piston in response to actuation of the hydraulic cylinder produces a torque on the pivoting member 114 which causes it to rotate away from the fixed member 112. Preferably, a spring return is provided so that the pivoting member 114 retracts automatically when the hydraulic pressure is released. The pusher tool 100 further comprises an adaptor bracket 120 having a proximal end connected to the pivoting member 114 of the hydraulic spreader via a set of four screws 132. The adaptor bracket 120 is a weldment of a plate 120a and a channel 120b, as best seen in FIG. 5. Plate 120a has four holes for passage of screws 132. At a distal end of the channel 120b, the channel arms have a pair of coaxial holes (not shown) for receiving a socket head shoulder screw 138. Screw 138, which is coupled to channel 120b by a nut 140, serves as a pivot pin for a rocker plate 126. The axis of pivot pin 138 is parallel to the axis of pivot pin 116 of the hydraulic spreader. The plate 120a, channel 120b and rocker plate 126 are all preferably made of aluminum alloy. A saddle 130 is securely mounted on the rocker plate 126 by means of a pair of screws 136. (Preferably, screws 132, 134 and 136 are socket head cap screws.) Saddle 130 has a shallow depression 130a for receiving member 56d of the lower spring 56, as shown in FIG. 5. Depression 130a extends for the full height of the saddle and defines a contact surface which is a cylindrical section having a curved concave profile. The depression resists any tendency for the pushed member 56d to slide off of the saddle. Saddle is made of UHMW polyethylene or other suitable material to prevent scratching of member 56d as the latter descends relative to saddle 130 while in contact therewith. The rocker plate 126 is pivotable about pivot pin 138 to allow the saddle 130 to adjust its orientation Vis-a-vis the pushed member. As seen in FIG. 5, counterclockwise rotation of the rocker plate 126 relative to the adaptor bracket 120 will be blocked when the rocker plate contacts the base of the channel 120b. Conversely, clockwise rotation of the rocker plate 126 relative to the adaptor bracket 120 will be blocked when the rocker plate contacts a restrictor plate 128 which is affixed to the endface of channel 120b. Rocker plate 126 comprises a base 126a pivotably mounted on pivot pin 138 and an extension 126b on one side which extends generally perpendicular to said base 126a and beyond the portion of saddle 130 furthermost from base 126a. The projecting end of extension 126b of rocker plate 126 prevents side slippage of member 56d off of the saddle. Referring to FIG, 5, the open state of the pusher tool is shown in solid lines and the closed state of the pusher tool is shown in dashed lines. In response to actuation of the hydraulic spreader, the pivot pin 138 travels along an arc. When the saddle contacts the member 54d, the rocker plate 126 adjusts so that the saddle will push member 54d radially inward. The amount of this radially inward displacement is a function of the length of the adaptor bracket 120 and the angle of rotation of pivoting member 114 of the hydraulic spreader. For different applications using the same hydraulic spreader, the radially inward displacement can be controlled by proper selection of the length of the adaptor bracket, or more specifically, the distance between the axis of pivot pin 116 and the axis of pivot pin 138. Interchangeable adaptor brackets can be attached to the hydraulic spreader using screws 132. Similarly, interchangeable rocker plates can be attached to the end of the adaptor bracket. For example, as shown in FIG. 6, a rocker plate 126' carrying a roller 146 can be substituted for the rocker plate 126 and saddle 130 of the first preferred embodiment. The rocker plate 126' is in the form of a channel having apertured arms which support a pivot pin 142 coupled thereto by a nut 144. The roller is rotatably mounted on the pivot pin 142. A pusher tool having a roller is preferred when the member being pushed by the tool undergoes a lengthy descent while in contact with the pusher tool. For example, the roller can be configured to roll against the tie rod of the tie rod/lower assembly while the assembly is being lowered into the downcomer annulus. Roller 146 has a shallow depression 146a for receiving the tie rod 54. This depression extends around the circumference of the roller and defines a contact surface having a curved concave profile. The depression 146a resists any tendency for the tie rod 54 to slide off of the roller. Roller 146 is made of UHMW polyethylene or other suitable material to prevent scratching of the tie rod 54 as the assembly descends relative to roller 146 while in contact therewith. The cost of fabricating shroud repair installation tools for specific applications can be further reduced in accordance with the present invention by providing a support structure wherein support post 108 is connected to extension 104 by a clevis pin 106. By adopting this as a standard connection, the same adaptor/extension assembly (102/104) can be used interchangeably in conjunction with multiple alternative tools. The preferred embodiments of the hydraulic pusher tool in accordance with the present invention have been disclosed for the purpose of illustration. Variations and modifications of the disclosed structure which fall within the concept of this invention will be readily apparent to persons skilled in the art of tooling design. All such variations and modifications are intended to be encompassed by the claims set forth hereinafter.
053368940	abstract	The controller for a single infrared source is capable of being programmed to act as a target for an AIM-9 target seeker. Data are read by the controller comprises (a) temperature data, (b) aperture data, (c) shutter-filter data, and (d) missile ID data. The controller includes a microprocessor CPU, with a program stored in a read only memory. The CPU reads aperture data from the stand, compares the data to signals derived from a potentiometer coupled to an aperture wheel, operates a motor to select an aperture on the wheel, and then sends an aperature ready signal to the stand. For temperature control, the black body is part of a resistance bridge circuit. A plurality of MOSFETs are used to select a value of resistance for a reference voltage in the bridge. The CPU reads temperature data from the stand and uses it to control the MOSFETs. An instrumentation amplifier across a diagonal of the bridge has its output coupled to a transistor circuit which controls power to the bridge, which thereby controls the temperature and resistance of the black body. The CPU reads shutter-filter data from the stand, and uses the data to generate signals to control solenoids for a shutter and two filters which are part of the IR heat source. A black body protection circuit opens a solid state relay to disable the 24-volt power supply to the bridge when the thermocouple indicates a temperature of approximately 905 degrees C. The results of testing this circuit shows that the fuse for the 24-volt supply will blow or the black body temperature will be maintained at approximately 905 degrees.
	claims	1. A method of evaluating a remaining lifetime of structural components of metal alloys, the method comprising the steps of:measuring a change in properties of the structural components of metal alloys based on a degree of short range ordering (SRO); andevaluating the remaining lifetime of the structural components of the metal alloys based on the change in the properties. 2. The method as set forth in claim 1, wherein the structural components of metal alloys are for use in nuclear power plants. 3. The method as set forth in claim 1, wherein SRO occurs in reactor operating conditions. 4. The method as set forth in claim 1, wherein the structural components of metal alloys are in contact with a coolant in nuclear power plants. 5. The method as set forth in claim 2, wherein the structural components of metal alloys for use in nuclear power plants are made from austenitic Fe—Cr—Ni alloys. 6. The method as set forth in claim 1, wherein the structural components of metal alloys are selected from a group consisting of coolant pipes, baffles, core barrels, instrumentation guide tubes, holddown springs, upper core supports, lower core supports, upper guide tube structures, core shrouds, bolts and pins. 7. The method as set forth in claim 4, comprising evaluating stress corrosion cracking by evaluating intergranular cracking susceptibility based on a quantitative determination of the degree of SRO. 8. The method as set forth in claim 1, wherein the properties are selected from a group consisting of hardness, thermal conductivity, and electrical resistivity. 9. The method as set forth in claim 8, wherein the hardness is measured using a nano indentation method. 10. The method as set forth in claim 8, wherein the thermal conductivity is measured in a transient plane source measurement or laser flash method. 11. The method as set forth in claim 8, wherein the electrical resistivity is measured in a four point probe measurement method. 12. The method as set forth in claim 5, wherein the structural components of metal alloys are made from 300 series austenitic stainless steels.
	summary
046506330	summary	The invention relates to a method and apparatus for protecting pumps and pump prime movers. Among numerous applications of the invention is the protection of such pump systems where used in returning condensate to a steam generator, such as that of a nuclear reactor. BACKGROUND OF THE INVENTION In well known, commercial, boiling water nuclear power reactors, a pressure vessel contains a core of fuel material submerged in a liquid such as light water, which serves both as a working fluid and a neutron moderator. The water is circulated through the core, whereby a portion thereof is converted to steam. The steam is taken from the pressure vessel and applied to a prime mover, such as a turbine, for driving an electric generator. The turbine exhaust steam is condensed and, along with any necessary makeup water, is returned to the pressure vessel by a condensate delivery system. Typically, nuclear reactors are provided with water level control systems which monitor water level within the vessel, steam outflow from the vessel, and feedwater inflow into the vessel. Water level control systems manipulate the operation of the condensate delivery system to control water level in the reactor vessel. Should steam outflow exceed feedwater inflow, the water level control system will tend to direct an increase in feedwater flow into the vessel. Similarly, for an excess of feedwater flow over steam flow, the fluid level control system will tend to direct a decrease in feedwater flow into the vessel. An indication of water level imbalance in the vessel will, however, dominate a signal generated by a steam and feedwater flow imbalance. A high water level indication will result in a demand for a reduction in feedwater flow. A low water level indication will result in a demand for an increase in feedwater flow. U.S. Pat. No. 4,302,288 discloses exemplary reactor water level control systems and is expressly incorporated herein by reference. Feedwater pumps in condensate delivery systems are typically driven by one of two means. Where feedwater pumps are driven by electric motors, feedwater flow can be controlled by directing the feedwater through a flow control valve and positioning the valve, according to the demands of the water level control system, to reduce or increase resistance to flow. In some nuclear plants, feedwater pumps are driven by turbines which utilize steam from the reactor vessel. In such cases, feedwater flow can be controlled by varying the amount of steam delivered to these turbines. A flow control valve is included in the steam delivery pipes to permit such control. Adjustments affecting feedwater flow through the feedwater pump also affect water pressure at both the pump outlet and inlet. By way of example, opening a valve used for flow control in the feedwater line will result in an increase in flow with a commensurate increase in the load on the motor driving the pump. Pressure at the pump inlet will fall. As another example, an increasing quantity of steam delivered to a turbine driving a pump will cause the pump to accelerate with an attendant decrease in inlet pressure. Feedwater flow will increase. The typical condensate delivery system comprises a plurality of centrifugal pumps. The feedwater pumps are those pumps which raise feedwater water pressure to the level of pressure inside the reactor vessel. The feedwater is typically at an elevated temperature. Water pressure is subject to variation at various internal points of a centrifugal pump during pump operation. Although average water pressure increases as the water penetrates the pump, local pressure within the pump may, through turbulence and other factors, drop considerably below pump inlet pressure. Should local pressure fall enough, flash boiling of the water with consequent pump cavitation can result. This adversely effects pump efficiency and can result in damage to the pump. Boiling occurs at saturation of the water at local pressure. That is to say, water is saturated when further additions of heat, or a decrease in local pressure, causes some of the water to change to a vapor. If a sufficient difference between the enthalpy of the water in the pump inlet and the enthalpy at saturation of the water at local pressure within the pump is maintained, boiling is prevented. This difference in enthalpy from inlet to pump interior is termed subcooling and is expressed in units of enthalpy, e.g. BTU/LBM. The subcooling required by any given pump varies with water temperature. Such characteristics of centrifugal pumps have long been known and data thereon is generally available from the pump manufacturer. Heretofore, protective measures to prevent pump cavitation have typically employed a pressure trigger to shut down the pump prime mover whenever pump inlet pressure has fallen below a predetermined value. Such pressure triggers operate at the chosen predetermined value for all water temperatures. Pressure trigger protective measures have been utilized in nuclear power plants. While the required subcooling for a given pump may increase or decrease for various combinations of temperature and pressure, adequate subcooling for a given pump can be obtained at lower pump inlet pressures as water temperature falls. Consequently, unnecessary triggering of protective steps can occur where a simple pressure trigger is used. In a nuclear power plant, a pressure-triggered feedwater pump shutdown resulting in a partial cut-off of water flow to the reactor could undesirably necessitate a scram of the reactor. Such pump system shutdowns are more likely to occur when maintaining maximum feedwater flow to the vessel is especially important to avoid a reactor scram. An example of such a case would be when reactor water level is low, and the feedwater level control system is attempting to increase feedwater flow. Another concern with existing systems is that increased flow demand results not only in reduced pressure, but in increased load on the pump motor, where motors are used. As the motor slows with increased load from its normal operating speed, it consumes more power and draws more current. For especially high load demands, the excessive current drawn can trigger a relay which shuts off the motor, again potentially resulting in a reactor scram. The operating history of nuclear reactors shows that cavitation and pump motor overloading in pump systems occurs far more frequently in feedwater pump systems than in condensate pump systems. Thus various embodiments of the invention are depicted as employed with feedwater pumps. Accordingly, it is an object of the present invention to provide a system for controlling the feedwater flow rate, which overrides demands for feedwater flow that are not sustainable by the condensate delivery system. It is another object of the present invention to monitor the subcooling of a liquid before introduction of the liquid into a motive pump and to compare the subcooling to the subcooling required in the liquid to prevent cavitation in the pump. It is a still further object of the present invention to monitor a parameter indicative of power consumed by a pump prime mover and to effect changes in pump load to reduce power consumption by the prime mover when power consumption is excessive. It is an object of the present invention to allow the condensate delivery system to achieve maximum feedwater flow under adverse system operating conditions. It is an additional object of the present invention to monitor system parameters most directly indicative of conditions within a liquid flow line and actuate protective apparatus on the basis thereof. It is a yet further object of the present invention to prevent cascading shutdowns of equipment resulting in unnecessary scrams of a nuclear reactor. SUMMARY OF THE INVENTION The present invention achieves these and other objects, according to one aspect of the invention, by providing, in a feedwater flowline including at least one feedwater pump, means in the flow line downstream from the pump for controlling flow through the line, a prime mover for the feedwater pump, sensors in the inlet of the pump for generating signals indicative of feedwater pressure and temperature, means for calculating the subcooling of the liquid in the pump inlet and generating a signal proportional thereto, means for providing a signal proportional to the predetermined required subcooling for the pump at the measured temperature of the liquid, a first comparator circuit for generating a first control signal should the subcooling be less than the required subcooling, means for monitoring a parameter related to power consumption by the pump prime mover and generating a signal proportional thereto, means generating a signal indicative of maximum permissible power consumption, a second comparator circuit for generating a second control signal should power consumption exceed a predetermined limit, a logical OR circuit for transmitting a positioning signal in response to either comparator generating a control signal, integrator means for boosting the positioning signal in response to the signal duration, and means to transmit the positioning signal to valve positioning means to position the valve so as to progressively reduce flow through the flow line. The aforesaid system provides an improvement over existing nuclear reactor water level control systems and pump system protection apparatus. By providing valve positioning signals to the feedwater flow control valve indicative of excessive power use and/or conditions conducive for pump cavitation, flow is progressively reduced and flowline system resistance to flow is progressively increased for as long as out of bounds conditions persist. Two significant parameters are controlled. Pressure through the pump system immediately upstream of the valve increases. Such a pressure increase improves water subcooling for any given temperature. Secondly, flow is reduced, and thus the load on the pump prime mover is reduced. A second preferred embodiment is disclosed below which sets forth application of the invention to turbine driven feedwater pumps. The second embodiment teaches generation of a pressure difference signal correlated with required subcooling. Either of the disclosed embodiments may be adapted for use with feedwater pumps driven by electric motors or with steam driven turbines. Each disclosed embodiment is shown incorporating an optional delay line which is used to trigger prime mover shutdowns should excessive power usage or reduced subcooling levels persist beyond certain time limits. Thus, it can readily be seen that the invention aids in maintaining pump efficiency and can, in combination with a water level control apparatus, maintain maximum sustainable flow through the flow line while avoiding pump damage or an unnecessary reactor scram.
052415708	abstract	In a boiling-water nuclear reactor, a core-control assembly comprises a control rod, a fuel support, a control-rod guide tube, a control-rod drive, and a control-rod-drive housing. The fuel support is welded to the control-rod guide tube. To remove the control-rod drive, the reactor vessel can be opened and the adjacent fuel bundles removed from the fuel support. Then the control-rod can be rotated after clearing the fuel support. The control rod is then rotated to decouple its bayonet connection to the control-rod drive. The control rod can then be lifted out of the reactor. This arrangement allows a control rod to be replaced without handling of the fuel support. In addition, the fuel support can be more securely installed since it does not need to be removed.
	description	Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0052663, filed on May 9, 2013, the contents of which is incorporated by reference herein in its entirety. 1. Field of the Disclosure The present disclosure relates to a passive containment spray system that when an accident occurs in a nuclear power plant, sprays coolant passively into a containment, condenses steam discharged from a reactor coolant system or a secondary system of the nuclear power plant, and lowers pressure within the containment. 2. Background of the Disclosure A nuclear reactor is categorized by a method of configuring a safety system or by an installation position of a main apparatus. First, the nuclear reactor is categorized by the method of configuring the safety system into an active nuclear reactor that uses active force such as one produced by a pump and a passive nuclear reactor that uses passive force such as force of gravity or gas pressure. Then, the nuclear reactor is categorized by the installation position of the main components into a loop type nuclear reactor (for example, a conventional pressurized water reactor) in which the main components (a steam generator, a pressurizer, a pump and the like) are installed outside of a reactor vessel and an integral nuclear reactor (for example a SMART nuclear reactor) in which the main apparatuses are installed within a reactor vessel. A containment spray system is used as one among systems that suppress an increase in pressure when an accident, such as a loss of coolant accident or a steam line break, that causes an increase in pressure within a containment (a reactor building, a containment vessel, a safeguard vessel and the like may substitute for the containment, the containment building or the reactor building is made up of reinforced concrete, and the containment vessel or the safeguard vessel is made up of steel) occurs in the various nuclear reactors including the integral reactor. Examples of application of an active containment spray system that sprays coolant into the containment using a spray pump is a SMART nuclear reactor of KOREA, a conventional pressurized water reactor, and the like. In addition to the containment spray system, a suppression tank or pool (a conventional boiling water reactor, U.S.A Westinghouse IRIS), a heat exchange or condenser (France SWR 1000 and India AHWR), a containment external spray and cooling (U.S.A. Westinghouse AP 1000) and the like are used as a system for suppressing the increase in pressure within the containment. If the pressure within the containment increases due to water(evaporated) or steam discharging, in the suppression tank method, steam and air is introduced into the suppression tank due to a difference in pressure and the steam is condensed, thereby decreasing the pressure. In the heat exchanger method, the steam within the containment is condensed using a cold wall surface of a heat exchanger tube, thereby decreasing the pressure. In the spray method, the cold coolant is sprayed and the steam within the containment is condensed, thereby decreasing the pressure. In addition, in the containment external spray and cooling method, the containment vessel is cooled by spraying the coolant (applying air-cooling later) to an external wall of a steel containment vessel and the steam is condensed on an internal wall, thereby decreasing the pressure within the containment vessel. An active spray system (internal spraying) is operated by a spray pump is used in many conventional nuclear reactors (active nuclear reactor), and a passive containment spray system (external spraying) is operated by gravity after opening an isolation valve is used in U.S.A. Westinghouse AP 1000 (passive nuclear reactor) and the like. However, the passive containment spray system in the related art, although it has much advantages as a passive system, includes the isolation value that is operated with a driving electric power source including an operation signal and an electric power source. Thus, if failure to an actuation signal generation system or an electric power system occurs, there is a possibility that the passive containment spray system in the related art will not be operated. Therefore, an aspect of the detailed description is to provide a passive containment spray system which is operated based on a natural phenomenon such as an increase in pressure within a containment when an accident occurs. The passive containment spray system is operated without an actuation signal generation system or an electric power system for opening an isolation valve. Another aspect of the detailed description is to provide a passive containment spray system that has much reliability to maintain integrity of a containment safely in a nuclear power plant. To achieve these and other advantages in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a passive containment spray system including: a spray coolant storage unit that communicates with a containment accommodating a reactor vessel and maintains equilibrium of pressure with the containment; a spray pipe that is installed within the containment in such a manner that when an accident occurs, a coolant supplied from the spray coolant storage unit is sprayed into the containment through the spray pipe due to an increase in pressure within the containment; and a connection pipe having one end inserted into the spray coolant storage unit to provide a flow path along which the coolant flows, and the other end connected to the spray pipe to supply the coolant passively to the spray pipe when the pressure within the containment increases due to an occurrence of an accident and a flow of the coolant occurs therein. In the passive containment spray system, the connection pipe may includes: an upward flow path portion inserted into the spray coolant storage unit, and providing a flow path along which the coolant flows when the pressure within the containment increases, the upward flow path extending up to a predetermined height such that the flow of the coolant from the spray coolant storage unit to the spray pipe is prevented from occurring within a normal plant operation pressure range for the containment; and a downward flow path portion extending downward from the upward flow path portion and connected to the spray pipe such that the coolant is supplied continuously to the spray pipe therethrough due to a difference of a gravitational head of water when the pressure within the containment increases and the flow of the coolant occurs at a height of the upward flow path portion or above. In the passive containment spray system, the upward flow path portion and the downward flow path portion are configured to have different flow path areas to facilitate gas discharging. The passive containment spray system may further include an intermediate cavity unit installed around the other end of the connection pipe to enhance the flow of the coolant that occurs in a direction from the spray coolant storage unit to the connection pipe, the intermediate cavity unit generating a difference in pressure from the spray coolant storage unit, and connected to the spray pipe to supply the coolant that passes through the connection pipe to the spray pipe. In the passive containment spray system, the spray pipe is connected to an upper portion of the intermediate cavity unit such that the spraying of the coolant starts after the coolant level in the intermediate cavity unit reaches a predetermined height. The passive containment spray system may further include a check valve installed in a pipe that is connected to an upper portion of the intermediate cavity unit, and opened to discharge gas within the intermediate cavity unit when pressure within the intermediate cavity unit is greater than that within the containment due to the coolant through the connection pipe. The passive containment spray system may further include an orifice installed in the pipe to limit an amount of flowing fluid discharged through the check valve such that an amount of the flowing coolant supplied to the spray pipe is secured enough. The passive containment spray system may further include a check valve installed in the spray pipe such that steam discharged into the containment or air is prevented from being introduced through the spray pipe into the connection pipe, the check valve being opened in a direction toward the spray pipe such that the coolant within the spray coolant storage unit flows through the spray pipe. In the passive containment spray system, at least one of the check valves installed in the pipe connected to the upper portion of the intermediate cavity unit and the check valve installed in the spray pipe is provided in plurality to prevent the passive containment spray system from malfunctioning due to a single failure. The passive containment spray system may further include at least one spray nozzle connected to the spray pipe to spray the coolant into the containment therethrough. In the passive containment spray system, the spray coolant storage unit is installed at a predetermined height inside of the containment to allow for spraying of the coolant due to a gravitational head of water, and is maintained in an opened state to achieve equilibrium of pressure between the spray coolant storage unit and the containment. In the passive containment spray system, the spray coolant storage unit is installed at a predetermined height outside of the containment such that the coolant is possible to spray due to a gravitational head of water, and an upper portion of the spray coolant storage unit is connected to the inside of the containment with a pipe to achieve equilibrium of pressure between the spray coolant storage unit and the containment. The passive containment spray system may further include an isolation valve installed in a pipe diverged from the connection pipe, and opened and closed to prevent an occurrence of the flow of the coolant from the spray coolant storage unit based on a siphon break phenomenon when a nuclear power plant is in a normal plant operation condition, when the spray coolant storage unit is being filled with the coolant, or when the spray coolant storage unit is in maintenance. The passive containment spray system may further include a pipe configured to connect a lower portion of the spray coolant storage unit and the spray pipe, and an isolation valve installed in the pipe and opened in case of non-operation of the system when an accident occurs. According to another aspect of the present invention, there is provide a nuclear power plant including: a reactor vessel; a containment that is installed outside of the reactor vessel such that radioactive material is prevented from releasing from the reactor vessel to outside of the containment; and a passive containment spray system, wherein the passive containment spray system include: a spray coolant storage unit that communicates with a containment accommodating the reactor vessel and maintains equilibrium of pressure between the spray coolant storage unit and the containment, a spray pipe that is installed within the containment in such a manner that when an accident occurs, a coolant supplied from the spray coolant storage unit is sprayed into the containment through the spray pipe due to an increase in pressure within the containment building, and a connection pipe having one end inserted into the spray coolant storage unit to provide a flow path along which the coolant flows, and the other end connected to the spray pipe to supply the coolant passively to the spray pipe when the pressure within the containment increases due to an occurrence of an accident and a flow of the coolant occurs therein. Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from the detailed description. Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. A passive containment spray system according to the present invention is described in detail below referring to the drawings. In the present disclosure, if constituents according to different embodiments are the same, they are given the same reference numerals and a description of the first one substitutes for that of the next one. In the present disclosure, although in the singular number, a noun is construed as in the plural number, except as distinctively expressed in context. FIG. 1 is a diagram illustrating a passive containment spray system 100 according to one embodiment of the present invention and a nuclear power plant 10 equipped with the passive containment spray system 100. The nuclear power plant 10 includes various systems in such a manner that heat generated in a reactor core 11a arranged within a reactor vessel 11 is used to produce useful energy. In addition, the nuclear power plant 10 includes various safety systems for maintaining integrity of the nuclear power plant 10 against a loss of coolant accident or a non-loss of coolant. Various pipes 11b may be connected to reactor vessel 11. Isolation valves 11b′ may be installed in the pipe 21b. Along with the safety system, a containment 12 is installed outside of the reactor vessel 11 in such a manner that radioactive material is prevented from releasing from the reactor vessel 11 to outside of the containment 12. Regardless of whatever this term denotes, the containment 12 may be whatever prevents the radioactive material from releasing and may be replaced with a containment building, a containment vessel, a reactor building or a safeguard vessel according to a design characteristics of the nuclear power plant 10. Among the safety systems, a safety injection system 13 is a system that injects coolant to within the reactor vessel 11 and thus maintains a coolant level in the reactor vessel 11, and a residual heat removal system 14 is a system that circulates coolant through the reactor vessel 11 and thus removes sensible heat of the reactor vessel 11 and residual heat of the reactor core 11a. The passive containment spray system 100 is one of the safety systems. When an accident occurs in the nuclear power plant 10, the passive containment spray system sprays cold coolant into the containment 12 and thus cools down and condenses high-temperature steam, thereby maintaining structural integrity of the containment 12. The passive containment spray system 100 includes a spray coolant storage unit 110, a spray pipe 120 and a connection pipe 130 in such a manner that performs an operation that is entirely based only on a natural principle without an operator's operation. The coolant that is to be sprayed into the containment 12 is stored in the spray coolant storage unit 110, and the spray coolant storage unit 110 is installed at a predetermined height within the containment 12. In the present disclosure, the storage unit collectively refers to a tank or a pool. The coolant stored in the spray coolant storage unit 110 is sprayed into the containment 12 based on the difference of a gravitational head of water. Thus, the spray coolant storage unit 110 should be suitably installed above the reactor vessel 11 so that a proper difference in height between the spray coolant storage unit 110 and the reactor vessel 11 can be maintained to facilitate spraying. The spray coolant storage unit 110 is formed to communicate with the containment 12 and thus maintains equilibrium of pressure with the containment 12. To allow the spray coolant storage unit 110 to communicate with the containment 12, for example, i) the spray coolant storage unit has an opening in at least one portion thereof, or ii) a hollow pipe connects the spray coolant storage unit 110 and the containment 12 such that steam or air can flow between the spray coolant storage unit 110 and the containment 12. The spray coolant storage unit 110, unlike the one illustrated, may be installed outside of the containment 12. If the spray coolant storage unit 110 is installed outside of the containment, the equilibrium of pressure cannot be maintained between the spray coolant storage unit 110 and the containment 12 in a state where the spray coolant storage unit 110 has an opening in the upper portion thereof. Therefore, the spray coolant storage unit 110 is held airtight and is connected with the containment 12 through the pipe inserted into an upper portion of the spray coolant storage unit 110 to maintain the equilibrium of pressure between the spray coolant storage unit 110 and the containment 12 (refer to FIG. 11). Since the equilibrium of pressure is maintained between the spray coolant storage unit 110 and the containment 12, as pressure increases within the containment 12, pressure increases within the spray coolant storage unit 110. Conversely, as the pressure decreases within the containment 12, the pressure decreases within the spray coolant storage unit 110. The spray coolant storage unit 110, which may be termed storage tank, a coolant storage pool, or whatever might be proper, may be whatever is formed in such a manner to accommodate the coolant inside and is installed inside of or outside of the containment 12 in such a manner as to maintain a proper difference in height between the spray coolant storage unit 110 and the reactor vessel 11. The spray pipe 120 is installed within the containment 12 in such a manner that the coolant supplied from the spray coolant storage unit 110 is sprayed into the containment 12. The spray pipe 120 should be suitably installed below the spray coolant storage unit 110 to facilitate the supplying of the coolant from the spray coolant storage unit 110 due to a gravitational head of water. The spray nozzle 121 is connected to the spray pipe 120 in such a manner that the coolant is injected into the containment 12 through the nozzle 121. The multiple spray nozzles 121 may be connected to the spray pipe 120. A direction in which the coolant is sprayed from the spray pipe 120 differs depending to a position in which the spray nozzle 121 is installed and a direction in which the coolant is injected through the spray nozzle 121. Because of this, the direction in which the coolant is injected through the spray nozzle 121 should be suitably set in such a manner that the coolant is spread out into the containment 12 in an evenly distributed manner. A check valve 122 may be installed in the spray pipe 120. The check valve 122 is opened by a flow that occurs in one direction and prevents the flow that occurs in the opposite direction. Accordingly, the check valve 122 prevents steam being discharged into the containment from being introduced into the spray pipe 120 and then moving toward the spray coolant storage unit 110. Conversely, when the flow of the coolant from the spray coolant storage unit 110 to the spray pipe 120 occurs, the check valve 122 is opened and thus allows the coolant being stored in the spray coolant storage unit 110 to pass through. The coolant that passes through the check valve 122 is sprayed into the containment 12 through the spray nozzle 121. The connection pipe 130 connects between the spray coolant storage unit 110 and the spray pipe 120 in such a manner as to provide a flow path along which the coolant is supplied from the spray coolant storage unit 110 to the spray pipe 120. One end of the connection pipe 130 may be inserted into the spray coolant storage unit 110, and the other end may be connected to the spray pipe 120. The connection pipe 130 includes an upward flow path portion 130a and a downward flow path portion 130b, in such a manner that an operation is performed differently when an accident occurs than in a normal plant operation condition. The upward flow path portion 130a is inserted into the spray coolant storage unit 110 and extends upward, and the downward flow path portion 130b extends downward from the upward flow path portion 130a. The upward flow path portion 130a is inserted into the spray coolant storage unit 110 and provides an upward flow path along which the coolant flows. Since the equilibrium of pressure is maintained between the spray coolant storage unit 110 and the containment 12, as the pressure increases within the containment 12, the pressure increases within the spray coolant storage unit 110. As the pressure increases within the spray coolant storage unit 110, the coolant within the spray coolant storage unit 110 is pushed up along the upward flow path portion 130a. When the nuclear power plant 10 is in the normal plant operation condition, pressure within the containment 12 is not always constant but continuously changes within a normal plant operation pressure range. Even though the pressure within the containment 12 is within the normal plant operation pressure range, when the pressure increases to some extent, the coolant within the spray coolant storage unit 110 is pressurized and thus there is a possibility that the passive containment spray system 100 will be operated. In order to remove such a possibility, the upward flow path portion 130a extends to a predetermined height above the coolant level. Therefore, the flow of the coolant from the spray coolant storage unit 110 to the spray pipe 120 is prevented from occurring within a normal plant operation pressure range for the containment 12. The predetermined height varies depending on a normal pressure range for the containment 12. As the normal pressure range increases, the upward flow path portion 130a increases in height. Accordingly, as long as the pressure within the containment 12 is within the normal plant operation pressure range, even though the pressure increases to some extent, the coolant does not flow above the highest position on the upward flow path portion 130a (a connection point between the upward flow path portion 130a and the downward flow path portion 130b). Thus, in the normal plant operation condition of the nuclear power plant 10, the flow of the coolant from the spray coolant storage unit 110 to the spray pipe 120 is prevented from occurring. When the steam is discharged into the containment 12 by an accident, the pressure within in the containment 12 increases up to high pressure exceeding a normal pressure range. When due to the increase in the pressure within the containment 12, the flow of the coolant occurs at the height of the upward flow path portion 130a or above, the downward flow path portion 130b extends downward from the upward flow path portion 130a and is connected to the spray pipe 120 in such a manner that the coolant is continuously supplied to the spray pipe 120 due to the head difference. The connection pipe 130 that includes the upward flow path portion 130a and the downward flow path portion 130b is for using a siphon phenomenon. When the flow occurs at the height of the upward flow path portion 130a or above due to the high-pressure steam that is discharged into the containment 12, the coolant is continuously supplied from the spray coolant storage unit 110 to the spray pipe 120 due to the head difference until the coolant is all used up. The normal plant operation pressure range for the containment 12 and the height of the upward flow path portion 130a vary according to the design characteristics of the nuclear power plant 10. Thus, the passive containment spray system 100 can spray the coolant by properly adjusting the height of the upward flow path portion 130a, entirely based only on a natural force. An isolation valve 131 may be installed a pipe that branches off from the connection pipe 130, in order to perform maintenance of the passive containment spray system 100 or fill the spray coolant storage unit 110 with the coolant. When the nuclear power plant 10 is in the normal plant operation condition, the isolation valve 131 is closed. At the time when the maintenance of the passive containment spray system 100 are necessary, the isolation valve 131 is opened to prevent the flow from occurring from the spray coolant storage unit 110 based on a siphon break phenomenon. When the isolation valve 131 is opened, the equilibrium of pressure is achieved between the connection pipe 130 and the containment 12, and thus the flow of the coolant from the spray coolant storage unit 110 through the connection pipe 130 to the spray pipe 120 does not occur. Accordingly, the passive containment spray system 100 does not be operated and this makes it possible to fill the spray coolant storage unit 110 with the coolant or perform maintenance of the spray coolant storage unit 110. The isolation valve 131 is kept closed when the nuclear power plant 10 is in the normal plant operation condition after filling the spray coolant storage unit 110 with the coolant or finishing maintenance of the spray coolant storage unit 110. The connection pipe 130 is kept filled with air whose pressure is the same as that of air within the containment, except for a portion below the coolant level in the spray coolant storage unit 110. When an accident occurs, the passive containment spray system 100 sprays the coolant into the containment 12 and thus condenses the steam discharged into the containment 12 and suppresses an increase in pressure within the containment 12. As the passive containment spray system 100 condenses the steam within the containment 12, a radioactive material concentration decreases within the containment 12. FIG. 2 is a diagram illustrating a passive containment spray system 200 according to another embodiment of the present invention and a nuclear power plant 20 equipped with the passive containment spray system 200. The nuclear power plant 20 includes various systems in such a manner that heat generated in a reactor core 21a arranged within a reactor vessel 21 is used to produce useful energy. The passive containment spray system 200 includes a spray coolant storage unit 210, a spray pipe 220, a connection pipe 230, and an intermediate cavity unit 240. An isolation valve 231 may be installed a pipe that branches off from the connection pipe 230. The intermediate cavity unit 240 is installed around an end of a downward flow path portion 230a and generates a difference in pressure between the intermediate cavity unit 240 and the spray coolant storage unit 210, in such a manner as to enhance the flow of the coolant that occurs in the direction from the spray coolant storage unit 210 to the connection pipe 230. The occurrence of the flow from the spray coolant storage unit 210 to the spray pipe 220 is due to the siphon phenomenon. Thus, the greater difference in pressure is generated between the intermediate cavity unit 240 and the spray coolant storage unit 210, the more enhanced the flow occurring in the direction from the spray coolant storage unit 210 to the spray pipe 220. The downward flow path portion 230a is inserted into the intermediate cavity unit 240, and the intermediate cavity unit 240 is connected to the spray pipe 220 in such a manner that the coolant that passes through the connection pipe 230 is supplied to the spray pipe 220. As the coolant is introduced into the intermediate cavity unit 240, the coolant level in the intermediate cavity unit 240 increases and the pressure increases. A check valve 241 is installed in a pipe above the intermediate cavity unit 240 in such a manner that when pressure within the intermediate cavity unit 240 is greater than that within a containment 22 due to the coolant introduced through the connection pipe 230, gas within the intermediate cavity unit 240 is discharged. Fluid that is discharged through the check valve 241 from the intermediate cavity unit 240 remains in a gas phase until before the coolant level reaches a full coolant level, but when the coolant level reaches the full coolant level, is discharged in a liquid phase. The liquid that is discharged through the check valve is very small in amount. As the fluid is discharged in the gas phase, a single liquid phase flow state of the coolant is maintained between the spray coolant storage unit 210, the intermediate cavity unit 240, and the spray pipe 220. Since the single phase flow state is maintained, a function of spraying due to the siphon phenomenon can be maintained even though the pressure within the containment 22 increases or decreases. The normal plant operation condition of the nuclear power plant 20 illustrated in FIG. 2 is described below referring to FIG. 3. Operation of the passive containment spray system 200 that is performed when an accident occurs is described step by step below referring to FIGS. 4 to 8. FIG. 3 is a diagram illustrating the passive containment spray system 200 illustrated in FIG. 2 in the normal plant operation condition and the nuclear power plant 20 equipped with the passive containment spray system 200. Various pipes 21b are connected to a reactor vessel 21. The pipes 21b are required to operate in the normal plant operation condition of the nuclear power plant 20. Isolation valves 21b′ installed in the pipe 21b are opened. The coolant is stored in the spray coolant storage unit 210, but there is a height difference H between an upward flow path portion 230a of the connection pipe 230 and the coolant level in the spray coolant storage unit 210. Therefore, even though the pressure within the containment 22 changes within the normal plant operation pressure range, the pressure does not increase enough to overcome the height difference H. Because of this, the passive containment spray system 200 does not be operated. Accordingly, a case where in the spray system in the related art, the isolation valve malfunctions while the nuclear power plant 20 is in the normal plant operation condition and the operation of the spray system starts is fundamentally excluded. As long as the coolant is not supplied from the spray coolant storage unit 210, the intermediate cavity unit 240 is empty. Therefore, the equilibrium of pressure is maintained between the spray coolant storage unit 210 and the containment 22, and the intermediate cavity unit 240 is filled with air whose pressure is the same as that within the containment 22 under a normal plant operation condition. Thus, under the normal plant operation condition for the nuclear power plant 20, the equilibrium of pressure is maintained between the spray coolant storage unit 210, the intermediate cavity unit 240, and the containment 22. FIG. 4 is a diagram for describing operation of the passive containment spray system 200 that is performed when the loss of coolant accident occurs in the nuclear power plant 20 illustrated in FIG. 2. When an accident, such as a steam line break or a loss of coolant accident occurs in the nuclear power plant 20, a safety injection system 23 and a residual heat removal system 24 are operated according to an actuation signal of an associated system. If when an accident, such as the steam line break or the loss of coolant accident occurs, the coolant (evaporated) or the steam is discharged into the containment 22 through a break portion, the temperature or the pressure within the containment 22 increase. The coolant is introduced into the connection pipe 230 due to the increase in the pressure within the containment 22 and thus the coolant level in the upward flow path portion 230a gradually increases. Unlike in the normal plant operation condition of the nuclear power plant 20, when the pressure within the containment 22 exceeds the normal plant operation pressure range, the coolant level in the upward flow path portion 230a goes over an bent portion of the connection pipe 230 and thus the flow of the coolant that passes through the downward flow path portion 230b of the connection pipe 230 occurs. Cutouts on the left of FIG. 2 show different cross-sectional areas between the upward path portion 230a and downward path portion 230b. The intermediate cavity unit 240 is gradually filled with the coolant that is introduced from the spray coolant storage unit 210 into connection pipe 230. When the flow occurs in the direction of the spray pipe 220 due to the coolant with which the intermediate cavity unit 240 is filled, a check value 222 installed in the spray pipe 220 is opened. The coolant that passes through the spray pipe 220 is injected through the spray nozzle 221 into the containment 22. As the coolant level in the intermediate cavity unit 240 is gradually raised, the difference of pressure between the intermediate cavity unit 240 and the containment 22 decreases gradually. When the pressure within the intermediate cavity unit 240 increases higher than that within the containment 22, the check valve 241 that is installed in the pipe above the intermediate cavity unit 240 is opened and thus gas within the intermediate cavity unit 240 is discharged. When the gas within the intermediate cavity unit 240 is discharged, the single phase flow state between the spray coolant storage unit 210, the intermediate cavity unit 240, and the spray pipe 220 is maintained. Since the single phase flow state is maintained, even though the pressure within the containment 22 changes (decreases or increases), the flow of the coolant due to the siphon phenomenon can be maintained. An orifice 242 for limiting an amount of fluid may be installed in the pipe in which the check valve 241 above the intermediate cavity unit 240 is installed, accordingly, the amount of fluid that is discharged through the check valve 241 is limited and the amount of fluid that is sprayed through the spray pipe 220 is effectively formed. FIG. 5 is a diagram for describing a step of filling the intermediate cavity unit 240 with the coolant when a loss of coolant accident occurs in the nuclear power plant 20 equipped with the passive containment spray system 200 that are illustrated in FIG. 2. When pressure P1 within the containment 22 increases and thus the coolant is introduced from the spray coolant storage unit 210 through the connection pipe 230 into the intermediate cavity unit 240, pressure P2 within the intermediate cavity unit 240 increases. Then, the coolant level in the intermediate cavity unit 240 increases gradually and thus a gravitational head of water PH is formed. However, when the pressure P1 within the containment 22 is greater than a sum PT (=P2+PH) of the pressure P2 within the intermediate cavity unit 240 and the gravitational head of water PH in the intermediate cavity unit 240 (P1>PT), the check valve 222 is not opened. Even though the check valve 222 is not opened, the coolant that passes through the connection pipe 230 is continuously introduced into the intermediate cavity unit 240, and the pressure P2 within the intermediate cavity unit 240 and the gravitational head of water PH in the intermediate cavity unit 240 increase gradually. FIG. 6 is a diagram for describing a spraying step that is performed by the passive containment spray system 200, which is subsequent to the step that is described in FIG. 5. The coolant is gradually introduced from the spray coolant storage unit 210 through the connection pipe 230 into the intermediate cavity unit 240. The sum PT (P2+PH) of the pressure P2 within the intermediate cavity unit 240 and the gravitational head of water PH in the intermediate cavity unit 240 is greater than the pressure P1 within the containment 22 (P1<PT), the check valve 222 installed in the spray pipe 220 is opened. Accordingly, the coolant flows through the spray pipe 220 and the spraying of the coolant into the containment 22 through the spray nozzle 221 starts. The steam discharged into the containment 22 is condensed by the operation of the passive containment spray system 200 and thus the increase in the pressure within the containment 22 is suppressed. FIG. 7 is a diagram for describing a gas-discharging operation step that is performed by the intermediate cavity unit 240, which is subsequent to the step described in FIG. 6. FIG. 8 is a diagram for describing a coolant-discharging operation step that is performed by the intermediate cavity unit 240, which is subsequent to the step described in FIG. 7. The coolant from the spray pipe 220 continues to be sprayed, and the coolant introduced through the connection pipe 230 increases the pressure P2 within the intermediate cavity unit 240 and raises the coolant level in the intermediate cavity unit 240. When the pressure P2 within the intermediate cavity unit 240 is greater than the pressure P1 within the containment 22, the check valve 241 is opened that is installed in the pipe above the intermediate cavity unit 240. Referring to FIG. 7, gas (air) within the intermediate cavity unit 240 is discharged through the check valve 241 until before the coolant level in the intermediate cavity unit 240 is highest. Referring to FIG. 8, the coolant level in the intermediate cavity unit 240 reaches the full coolant level and the liquid (coolant) within the intermediate cavity unit 240 is discharged through the check valve 241. The orifice is installed in the pipe in which the check valve 241 is installed, in such a manner that the amount of fluid being discharged through the check valve 241 is throttled and thus the amount fluid being discharged through the spray pipe 220 is secured enough. When most of all the gas is discharged from the intermediate cavity unit 240, the single phase flow state of being filled with the liquid (coolant) is maintained between the spray coolant storage unit 210, the intermediate cavity unit 240, and the spray pipe 220. Since the single phase flow state is maintained, even though the pressure within the containment 22 changes (decreases or increases), the flow of the coolant due to the siphon phenomenon can be maintained. Accordingly, the passive containment spray system 200 can continuously spray the coolant into the containment 22. The spraying of the coolant by the passive containment spray system 200 proceeds continuously until the coolant within the spray coolant storage unit 210 and the intermediate cavity unit 240 are almost used up. The increase in the pressure within the containment 22 is suppressed until the operation of the passive containment spray system 200 is stopped due to the using-up of the coolant. The passive containment spray system 200 is operated at an early stage of an accident, such as the steam line break or the loss of coolant accident, in which the pressure within the containment 22 increases comparatively abruptly, and thus protects the containment 22. However, the coolant is used up and thus the passive containment spray system stops the operation at a middle or latter stage in which an amount of discharge of the steam decreases. However, because there is a large space available within an upper portion of the containment 22, the operation time can be extended depending on the design capacity of the spray coolant storage unit 210. FIG. 9 is a diagram illustrating a passive containment spray system 300 according to another embodiment of the present invention and a nuclear power plant 30 equipped with the passive containment spray system 300. The nuclear power plant 30 includes various systems in such a manner that heat generated in a reactor core 31a arranged within a reactor vessel 31 is used to produce useful energy. Among the safety systems, a safety injection system 33 may be a system that injects coolant to within the reactor vessel 31 and a residual heat removal system 34 may be a system that circulates coolant through the reactor vessel 31. Various pipes 31b may be connected to reactor vessel 31. Isolation valves 31b′ may be installed in the pipe 31b. The passive containment spray system 300 may include a spray coolant storage unit 310, a spray pipe 320 and a connection pipe 330. An isolation valve 331 may be installed in a pipe that branches off from the connection pipe 330. Unlike in the normal plant operation condition of the nuclear power plant 30, when the pressure within the containment 32 exceeds the normal plant operation pressure range, the coolant level in the upward flow path portion 330a goes over a bent portion of the connection pipe 330 and thus the flow of the coolant that passes through the downward flow path portion 330b of the connection pipe 330 occurs. The spray pipe 320 is connected to an upper portion of the intermediate cavity unit 340 in such a manner that the coolant in the intermediate cavity unit 340 reaches a predetermined level and then the spraying of the coolant starts. As illustrated in FIG. 9, when the spray pipe 320 is connected to the uppermost portion of the intermediate cavity unit 340, the coolant level in the intermediate cavity unit 340 is raised and thus the gas (air) within the intermediate cavity unit 340 passes first through the spray pipe 320 and is discharged into a containment 32. Then, after the intermediate cavity unit 340 reaches the full coolant level, the coolant passes through the spray pipe 320 and is sprayed into the containment 32. When the flow occurs in the direction of the spray pipe 320 due to the coolant with which the intermediate cavity unit 340 is filled, a check value 322 installed in the spray pipe 320 is opened. The coolant that passes through the spray pipe 320 is injected through the spray nozzle 321 into the containment 32. When the spray pipe 320 is connected to the upper portion of the intermediate cavity unit 340, the gas is first discharged from the intermediate cavity unit 340, and thus the passive containment spray system 300 can be operated continuously without being provided with the separate check value for discharging the gas within the intermediate cavity unit 340. FIG. 10 is a diagram illustrating a passive containment spray system 400 according to another embodiment of the present invention and a nuclear power plant 40 equipped with the passive containment spray system 400. The nuclear power plant 40 includes various systems in such a manner that heat generated in a reactor core 41a arranged within a reactor vessel 41 is used to produce useful energy. Among the safety systems, a safety injection system 43 may be a system that injects coolant to within the reactor vessel 41 and a residual heat removal system 44 may be a system that circulates coolant through the reactor vessel 41. Various pipes 41b may be connected to reactor vessel 41. Isolation valves 41b′ may be installed in the pipe 41b. The passive containment spray system 400 may include a connection pipe 430. An isolation valve 431 may be installed in a pipe that branches off from the connection pipe 430. Unlike in the normal plant operation condition of the nuclear power plant 40, when the pressure within the containment 42 exceeds the normal plant operation pressure range, the coolant level in the upward flow path portion 430a goes over a bent portion of the connection pipe 430 and thus the flow of the coolant that passes through the downward flow path portion 430b of the connection pipe 430 occurs. When the flow occurs in the direction of the spray pipe 420 due to the coolant with which the intermediate cavity unit 440 is filled, a check value 422 installed in the spray pipe 420 is opened. A check valve 441 may be installed in a pipe above the intermediate cavity unit 440. The passive containment spray system 400 includes a pipe 450 that connects between the lower portion of a spray coolant storage unit 410 and a spray pipe 420 and an isolation value 451 that is installed in the pipe 450. Since the passive containment spray system 400 is operated entirely based on a natural phenomenon, it is not possible to completely remove a possibility that an unexpected malfunction or non-operation will occur. In order to handle the unexpected non-operation, the passive containment spray system 400 includes the isolation value 451 that can be opened in case of the non-operation of the system when an accident occurs. When the isolation value 451 is opened, due to the gravitational head of water the coolant is supplied directly from the spray coolant storage unit 410 to the spray pipe 420 and is sprayed through a spray nozzle 421 into a containment 42. FIG. 11 is a diagram illustrating a passive containment spray system 500 according to another embodiment of the present invention and a nuclear power plant 50 equipped with the passive containment spray system 500. The nuclear power plant 50 includes various systems in such a manner that heat generated in a reactor core 51a arranged within a reactor vessel 51 is used to produce useful energy. Among the safety systems, a safety injection system 53 may be a system that injects coolant to within the reactor vessel 51 and a residual heat removal system 54 may be a system that circulates coolant through the reactor vessel 51. Various pipes 51b may be connected to reactor vessel 51. Isolation valves 51b′ may be installed in the pipe 51b. A spray coolant storage unit 510 is installed at a predetermined height outside of a containment 52 in such a manner that the coolant can be sprayed due to the gravitational head of water, and is connected to the inside of the containment 52 with a pipe 511 in such a manner that the equilibrium of pressure is achieved. An isolation valve 512 may be in the pipe 511 that connects between the spray coolant storage unit 510 and the containment 52. The isolation valve 512 is normally opened, but can be closed if necessary for the isolation when the maintenance of a passive containment spray system 500 is performed or when an accident and a break of the pipe 511 for the spray system occur at the same time. An intermediate cavity unit 540, as illustrated, is also installed outside of the containment 52, but the intermediate cavity unit 540 may be installed inside of the containment 52. In this case, a connection pipe 530 may pass through the containment 52 in order to connect between the spray coolant storage unit 510 outside of the containment 52 and the intermediate cavity unit 540 inside of the containment 52. An isolation valve 531 may be installed in a pipe that branches off from the connection pipe 530. Unlike in the normal plant operation condition of the nuclear power plant 50, when the pressure within the containment 52 exceeds the normal plant operation pressure range, the coolant level in the upward flow path portion 530a goes over a bent portion of the connection pipe 530 and thus the flow of the coolant that passes through the downward flow path portion 530b of the connection pipe 530 occurs. When the flow occurs in the direction of the spray pipe 520 due to the coolant with which the intermediate cavity unit 540 is filled, a check value 522 installed in the spray pipe 520 is opened. The coolant that passes through the spray pipe 520 is injected through the spray nozzle 521 into the containment 52. A check valve 541 may be installed in a pipe above the intermediate cavity unit 540. Isolation valves 523 and 542 may be installed also in the pipes that are connected to the intermediate cavity unit 540, respectively, and may be closed if necessary when the maintenance is performed or when an accident and a break of the pipe associated with the spray occur at the same time. A position and a height at which the spray coolant storage unit 510 or the intermediate cavity unit 540 is installed are differently determined according to the design characteristics of a nuclear power plant 50. The passive containment spray system and the nuclear power plant equipped with the passive containment spray system, which are described, are not limited to the configurations and manners of the embodiments described above, but all of or some of the embodiments may be selectively combined with each other to achieve various modifications to the embodiments. According to the present invention with the configurations described above, when an accident occurs, if the pressure within the containment increases to a predetermined value or above, the passive containment spray system can be operated entirely based only on a natural force without receiving any actuation signal. This can improve reliability of the system. According to the present invention, a probability that the passive containment spray system will be operated is increased. Thus, the integrity of the containment can be maintained more safely, and the safety of the nuclear power plant can be improved. The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.
	claims	1. A nuclear fuel pellet laminate structure having enhanced thermal conductivity, comprising:a nuclear fuel pellet; anda thermally conductive metal layer disposed above or below the nuclear fuel pellet,wherein the nuclear fuel pellet is a nuclear fuel matrix, and does not include thermally conductive metal powder,wherein a ratio of a diameter to a height of the nuclear fuel pellet is in a range of 1.6 to 2.0,wherein formation of impurities due to chemical reactions of the thermally conductive metal layer is suppressed,wherein the impurity comprises one or more selected from the group consisting of a thermally conductive metal hydride, a thermally conductive metal oxide, a thermally conductive metal nitride, a thermally conductive metal-uranium compound, a thermally conductive metal-plutonium compound, and a thermally conductive metal-thorium compound,wherein the thermally conductive metal layer is a plate shape, a cross shape or radial shape for connecting a peripheral portion in contact with a nuclear fuel cladding tube in a radial direction from the center, andwherein the thermally conductive metal layer comprises one or more selected from the group consisting of molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf), tantalum (Ta), rhodium (Rh), zirconium (Zr), beryllium (Be), and aluminum (Al). 2. The nuclear fuel pellet laminate structure of claim 1, wherein the height of the nuclear fuel pellet is 3 mm to 6 mm. 3. The nuclear fuel pellet laminate structure of claim 1, wherein the content of the thermally conductive metal layer is 1 wt. % to 10 wt. % based on the total weight of the nuclear fuel pellet. 4. A method for manufacturing a nuclear fuel pellet laminate structure having enhanced thermal conductivity, comprising:(a) a step of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet; and(b) a step of disposing a thermally conductive metal layer above or below the nuclear fuel pellet manufactured in step (a),wherein the nuclear fuel pellet is a nuclear fuel matrix, and does not include thermally conductive metal powder,wherein a ratio of a diameter to a height of the nuclear fuel pellet is in a range of 1.6 to 2.0,wherein formation of impurities due to chemical reactions of the thermally conductive metal layer is suppressed,wherein the impurity comprises one or more selected from the group consisting of a thermally conductive metal hydride, a thermally conductive metal oxide, a thermally conductive metal nitride, a thermally conductive metal-uranium compound, a thermally conductive metal-plutonium compound, and a thermally conductive metal-thorium compound,wherein the thermally conductive metal layer is a plate shape, a cross shape or radial shape for connecting a peripheral portion in contact with a nuclear fuel cladding tube in a radial direction from the center, andwherein the thermally conductive metal layer comprises one or more selected from the group consisting of molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf), tantalum (Ta), rhodium (Rh), zirconium (Zr), beryllium (Be), and aluminum (Al). 5. The method of claim 4, wherein the molding in step (a) is performed for 30 seconds to 20 hours under a pressure of 100 MPa to 500 MPa, and the thermally treating is performed for 1 hour to 20 hours at a temperature of 1,300° C. to 1,800° C. under a hydrogen atmosphere. 6. The method of claim 4, wherein the disposing of the thermally conductive metal layer in step (b) is performed through one or more methods selected from the group consisting of a coating method, a vapor deposition method, and a three-dimensional printing method.
	description	This application claims priority based on International Patent Application No. PCT/FR02004/050049, entitled “Method and Device for Capturing Ruthenium Present in a Gaseous Effluent” by Bruno Courtaud, Fabrice Morel, Georges Pagis and Carol Redonnet, which claims priority of French Application No. 03/01538, filed on Feb. 10, 2003, and which was not published in English. The present invention relates to a method and to a device for trapping ruthenium present in a gaseous effluent. The invention is particularly applicable in the filtration of the gaseous effluents coming from the reprocessing of nuclear fuels that contain or are likely to contain ruthenium. Ruthenium is one of the atomic fission products generated during the nuclear reaction. In this context, it is found in the irradiated fuel rods. It represents 6% by weight of all of the fission products, and its isotopes 103Ru and 106Ru are radioactive. In the processes for processing nuclear fuels, the fuel rods are firstly sheared and dissolved in nitric acid. Most of the components making up the rods, including ruthenium, then pass into solution in the form of nitrates. This dissolution solution is then sent to liquid/liquid extraction shops. The ruthenium is present at this step of the process in the aqueous phase called the fission product (FP) solution. This solution is sent to the vitrification shops where it is calcined in a furnace and the elements in oxide form resulting therefrom are then vitrified. Thus, ruthenium, like the other radioelements, is vitrified. Unfortunately, the oxide form RuO4 is extremely volatile and, although trapped by the treatment carried out on the gaseous effluents coming from these processes, a fraction, albeit a minute one, is likely to escape, especially via the possible leaks in the processing circuit. Ruthenium in this gaseous form RuO4 can then be transferred into the building ventilation system and pass through the ventilation ducts. It then passes through all the filtration barriers of the ventilation system. It then gets into the primary stack and is discharged into the environment. At the present time, in most irradiated fuel reprocessing plants, the gaseous effluents coming from the cells emitting ruthenium pass through a set of two filters that strip them of the coarsest particles and prevent too rapid clogging of the following filtration stages. They then pass through the first and second barrier filters placed in shielded containers. It is in particular on these filter elements that the present invention, which constitutes a very effective means of preventing the discharge of ruthenium, can preferably be attached. When the ruthenium is in the form of solid RuO2, it is relatively simple to trap it using absolute filtration. This is currently the case in vitrification shops that possess several filtration barriers in their ventilation systems. The very high efficiency (VHE) filters of the first, second and third barriers prevent the passage of solid RuO2 particles. Of course, the VHE filters trap only the RuO2 that is formed upstream. If the reduction of RuO4 takes place downstream of the VHE filters, it is obvious that RuO2 may be discharged into the environment. This is because the glass-fibre filter medium of the VHE barriers is not capable of stopping gaseous RuO4, which can then pass into the stack, possibly being reduced to RuO2 in transit. One way of stopping this RuO4 therefore consists in reducing it to RuO2 upstream of the filtration barriers and then in trapping it on a VHE filter. It is also possible to pass the gaseous effluent containing ruthenium over a reducing medium such as poly(4-vinylpyridine) (PVP) or wet metal surfaces that act as catalysts. However, solid traps, which are effective at room temperature, particularly commercially available PVP, generate very substantial head losses and therefore require a significant increase in the power of the ventilation fans. It is also possible to carry out a scrubbing operation on the gaseous effluent by means of an aqueous solution, possibly containing a reactant such as sodium hydroxide. However, the carbonation of sodium hydroxide by picking up atmospheric CO2 requires substantial replenishment of the reactant, and therefore the generation of a large volume of liquid effluent. In general, the efficiency of these systems proves to be limited. This is because the filter elements of the prior art stop most of the aerosols but are incapable of effectively stopping RuO4. Obviously from the environmental standpoint there is a real need to have an effective method of trapping ruthenium likely to be present in particular in the gaseous effluents coming from irradiated nuclear fuel reprocessing plants. The inventors have developed a ruthenium trapping method and device that meet this need. In particular, the method of trapping ruthenium present in a gaseous effluent of the present invention is characterized in that it comprises bringing the said gaseous effluent into contact with an aqueous solution or slurry comprising at least one alkylene glycol polymer and/or at least one alkylene glycol copolymer, in which the alkylene(s) has (have) from 2 to 6 carbon atoms. The present invention also relates to the use of the aforementioned aqueous solution or slurry for trapping ruthenium present in a gaseous effluent. The method of the invention may be employed either in a gas scrubbing unit, the polymer or copolymer then being used as a reactant added to the scrubbing water, or by manufacturing a ruthenium-trapping cartridge. The said cartridge comprises, for example, a substrate on which an alkylene glycol polymer or an alkylene glycol copolymer is placed, in which polymer or copolymer the alkylene(s) has (have) from 2 to 6 carbon atoms. Thanks to the aforementioned polymer or copolymer in aqueous solution, for example used in a gaseous effluent scrubbing unit, the present invention makes it possible to achieve, unexpectedly, an efficiency comparable to that using sodium hydroxide while avoiding the aforementioned carbonation problem. The scrubbing units that can be used for scrubbing a gaseous effluent using the method of the present invention are those known to a person skilled in the art. For example, the unit may be a packing column, a venturi scrubber, etc. When a cartridge is used, the flexibility of the method and of the device of the present invention that are based on the aforementioned polymers and copolymers advantageously makes it possible to design ruthenium traps suitable for existing irradiated nuclear fuel processing plants. Furthermore, the amount of polymer that has to be used is very small, which really does prevent any safety problem and creates no difficulty in management of the waste produced by the invention when carrying out the periodic replacement operations that may be necessary. The polymer or copolymer may be selected according to the operating conditions, for example according to the surface temperature, to the nature of the other chemical species present in the gaseous effluent, possibly according to the substrate used, to the cost, to the ventilation power, etc. According to the invention, the properties of choice of the polymers and copolymers that can be used in the present invention may be the following: the polymer or copolymer is advantageously soluble in water so that it can be deposited on a substrate by impregnation of aqueous solutions; the composition of the polymer or copolymer is advantageously simple, for example consisting solely of carbon, oxygen and hydrogen, thereby reducing the costs of the method and the device of the present invention; and the polymer or copolymer is capable of trapping the RuO4 owing to the fact that it contains one or more reducing groups —OH by analogy with the reducing effect of sodium hydroxide. Preferably, the polymer or copolymer has hydroxyl end groups. In this case, these are alkylene glycol polymers and copolymers terminated with hydroxyl end groups. Advantageously, according to the invention, the alkylene glycol polymer may for example be selected from the group consisting of polyethylene glycol, polypropylene glycol, polybutylene glycol or a blend of these. Advantageously, the alkylene glycol copolymer is a copolymer consisting of polymers selected from the group consisting of polyethylene glycol, polypropylene glycol and polybutylene glycol. For example, the alkylene glycol copolymer may be a copolymer based on ethylene glycol, propylene glycol and butylene glycol at the same time. Advantageously, according to the invention, the alkylene glycol copolymer may be of the following formula (I): in which m and p are integers such that, independently, 1≦m≦8 and 3≦p≦12. The copolymer of formula (I) may for example be a polyethylene glycol/polypropylene glycol copolymer. According to the invention, a solution or slurry of an aforementioned polymer or an aforementioned copolymer alone, of a blend of various aforementioned alkylene glycol polymers, or of a blend of various aforementioned alkylene glycol copolymers, or of a blend of one or more aforementioned polyalkylene glycols and of one or more aforementioned alkylene glycol copolymers may be used in the method and the device of the present invention. Also, in the present description, the expression “polymer or copolymer” and the expression “alkylene glycol polymers or copolymers” cover, of course, these various embodiments of the present invention. For trapping ruthenium on a solid substrate, the aforementioned polymers furthermore have the advantage of being able, because of their wetting properties, to be easily deposited as thin layers on a substrate, thus offering better characteristics in terms of head loss and of developed surface area than the products of the prior art. Thus, when a substrate is used to implement the present invention, the aqueous polymer or copolymer slurry is placed on the substrate. This embodiment advantageously makes it possible to reduce the interfacial surface tension between the substrate and the ambient moisture and thus favour the trapping of water from the water contained in the gaseous effluent to be treated on the surface of the substrate, thus making it easier to absorb the ruthenium and to reduce it. The forms of ruthenium covered by the present invention are essentially RuO4 and RuO2. After contact with the substrate, the RuO4 may be absorbed by the polymer or copolymer placed on the surface and react with the latter. This is because the aforementioned polymers and copolymers favour the absorption of RuO4 and limit its desorption, and therefore allow the RuO4 to remain on the surface for a long enough time for it to be reduced. Furthermore, the hydroxyl functional groups of these polymers and copolymers reduce this form of ruthenium to RuO2. The present invention therefore makes it possible both to favour the trapping of RuO4 ruthenium and the chemical operation of its reduction. Also advantageously according to the invention the substrate may be preferably selected so that it has a large area of contact with the gaseous effluent to be treated for a low head loss. This is because the ruthenium present in the effluent comes into contact with the surface by collision, and it is preferable for the collision factor to be as high as possible so that the maximum amount of ruthenium is trapped. Thus, very preferably, the substrate is a divided substrate, for example a substrate in the form of fibres, for example a wool or mass of fibres, preferably one that is not compacted when it is desired to avoid head losses by the flow of the gaseous effluent through said substrate. A fibrous substrate furthermore has the advantage of retaining the possible solid ruthenium (RuO2) particles. In the case of such a substrate, the contacting with the gaseous effluent will advantageously take place by forcing the said effluent to pass through the fibrous substrate. According to the invention, the substrate may for example be a metal wool, preferably of low density and of highly developed surface area, such as a stainless steel wool. This is because such a substrate makes it possible to achieve a very high efficiency, while generating only a very low head loss, not requiring the existing ventilation fans to be changed. The substrate may also be a glass wool. The polymer or copolymer may be placed on the substrate by any suitable means known to those skilled in the art. Preferably, for example when the substrate is fibrous, this means prevents the substrate from being clogged so that the gaseous effluent can pass through it, if necessary limiting the head losses. Advantageously, the polymers and copolymers used in the present invention are soluble in water and therefore allow aqueous solutions, called impregnation solutions, to be prepared, these being practical for placing the polymers or copolymers on the substrate, for example by simply dipping it into the said impregnation solutions. The concentration of the solution will in particular be determined according to the amount of polymer or copolymer to be placed on the substrate. The manufacture of this solution and the impregnation are described in the examples below. Preferably, after impregnation, the substrate, for example the fibres of which it is composed, will be covered with a thin layer or film of aqueous slurry of the selected polymer or copolymer over its entire surface, that is to say, in the case of fibres, over all its constituent fibres. According to the invention, the operation of contacting the effluent with the solution or slurry of the polymer or copolymer, optionally deposited on a substrate, may be carried out at a suitable temperature so that the contacted materials (polymers, substrate) are not destroyed. This operation will in general be carried out at a temperature ranging from 20 to 50° C. In the device of the present invention, the cartridge may furthermore comprise a structure supporting the substrate on which the alkylene glycol polymer or copolymer is placed. According to the invention, this structure, in addition to its function of supporting the said substrate, may be a structure suitable for the insertion of the cartridge into a possibly pre-existing gaseous effluent line. For example, it may be in the form of a basket. This structure is preferably made of a material suitable for its use under the conditions of the present invention, for example stainless steel. In general, the said structure gives the cartridge its geometry. According to the invention, the geometry of the said cartridge is preferably designed so that it can be placed, advantageously in a removable manner, in a ruthenium-containing gas line so as to force the gaseous effluent to pass through the said cartridge. Thus, this allows prefabrication of modules, which consist of the substrate and a support, the fitting of which requires no modification of the units nor of the procedures. Furthermore, the cartridge may be provided with peripheral seals intended to force the said ruthenium-containing gaseous effluent to pass through the said cartridge, preferably without any loss. This may be important in order to force the effluent to pass through the polymer-impregnated or copolymer-impregnated substrate, and avoid any loss, so as to trap all of the ruthenium present in the effluent in the cartridge. In a preferred embodiment, the cartridge of the present invention may therefore comprise: the substrate on which the alkylene glycol polymer or copolymer is placed, the said surface being in the form of glass wool or stainless steel wool; a structure, or support, supporting the said substrate on which the alkylene glycol polymer or copolymer has been placed, the said structure preferably being in the form of a basket, preferably a latticed basket; and peripheral means for sealing the said cartridge, for example seals, for example of the type made of Viton (brand name) or silicone, making it necessary for the gaseous effluent to pass through the said substrate. According to the invention, one or more cartridges may of course be used if necessary, for example mounted in series, so that the gaseous effluent can pass through them in succession. The ventilation systems involved in the present invention for trapping ruthenium are especially those for extraction and for treatment of the vitrification cells, and also those for the cells for dismantling irradiated nuclear fuel reprocessing plants. The ventilation systems for reprocessing plants are generally composed of several filtration barriers: medium-efficiency (ME) pre-prefilters and high-efficiency (HE) prefilters directly in the cell; very high-efficiency (VHE) filters for the first and second barriers in shielded containers; VHE filters for the third barrier in sealed airlock containers; and HE traps at the base of the stack. To succeed in trapping the RuO4, at least one cartridge of the present invention may for example be inserted in one or more of the aforementioned filter elements. One embodiment of the present invention in a plant will be described below in the examples. A cartridge according to the invention may be positioned either in the first barrier or in the second barrier. The filter elements of the first barrier will preferably be replaced at least about every two years. They will be changed in particular when they become too highly irradiating owing to trapped radioactive particles, and possibly in the event of them being clogged. The filter elements of the second barrier are in general more rarely replaced, as no substantial rise in irradiation or in clogging is observed therein. Fitting the ruthenium trapping system of the present invention in the first barrier has the advantage, should it suffer a loss of efficiency, of benefiting from the periodic changing of this first barrier. However, when installed in this way, the ruthenium trapping substrate or medium will undergo more substantial irradiation, liable to accelerate its ageing. Other features and advantages of the present invention will become further apparent to those skilled in the art on reading the illustrative examples that follow, with reference to the appended figures. Grouped together in Table 1 below are various polymers, copolymers and blends that can be used in the present invention. They are commercially available, for example from: Lambert Rivière (manufacturer: ICI); Albright & Wilson; Roth Sochiel. TABLE 1Melting pointNameMeaning(° C.)PEGPolyethylene glycol—300 toPolyethylene glycols having—35 000 PEGmolecular weights rangingfrom 300 to 35 000 g/molCopol 1Polyethylene<0glycol/polypropylene glycolblock copolymerCopol 2Ethylene glycol/propylene27glycol/butylene glycolcopolymerCopol 7PEG 2000 + PEG 300 in25proportions of 50/50 byweightCopol 9PEG 2000 + PEG 300 + Copol 134in proportions of 70/20/10 byweightCopol 10PEG 2000 + PEG 300 + Copol 123in proportions of 45/45/10 byweightCopol 11PEG 2000 + Copol 2 in38proportions of 50/50 byweightCopol 14Copolymer based on ethylene37glycol, propylene glycol andbutylene glycol Stainless steel wool (fibre diameter (Ø): 12 μm), called WB12 (trade name), specimens, as substrates, were impregnated with a 5 wt % solution of a copolymer according to the present invention. The copolymer of the present invention, used here, which has surfactant properties, is a PEG/PPG (polyethylene glycol/polypropylene glycol) copolymer, which is liquid at room temperature, denoted in the above Table 1 by Copol 1. It comes from Albright and Wilson, with the trade name AMPLICAN. The operating conditions for the trials were the following: temperature: 18.5° C.; relative humidity: 42%; [O3]: 1.8 mg/l; flow rate: 2.24 m3/h; duration of the trial: 5 h; 1 unimpregnated disc+3 WB12 discs impregnated 100% with Copol 1. FIG. 1 shows a test bed (1) used for this example. It consists of a glass tube (2) in which the three WB12 discs (S) 100% impregnated with Copol 1 and the unimpregnated stainless steel control disc (6) have been placed. The arrow (8) indicates the direction of flow of the ruthenium-containing gaseous effluent through the tube. The three discs and the upstream control disc of the traps were analyzed—the amount of trapped ruthenium (QRu) in the discs is given in Table 2 below. The % trapped Ru corresponds to the amount of ruthenium trapped on a disc relative to the total amount of ruthenium generated. The trapped % of Ru impinging on the trap corresponds to the amount of ruthenium trapped on a disc relative to the amount of ruthenium impinging on this disc. A guard placed downstream of the device allows the amount of Ru not trapped by the discs to be determined. TABLE 2Disc 1:Disc 2:Disc 3:UnimpregnatedWB12 +WB12 +WB12 +WB12 discCopol 1Copol 1Copol 1GuardQRu (mg)0.0560.8180.2120.014<0.01% Ru574191—trappedTrapped57894——% of Ruimpingingon the trap The results are plotted on the graph in appended FIG. 2. In this figure, “Du” indicates the unimpregnated stainless steel disc and “D1, D2 and D3” indicate the various aforementioned discs, in the direction of flow of the gaseous effluent (from D1 towards D3). The results are very satisfactory since practically all of the ruthenium has been trapped on the three traps mounted in series. To study the impact of a change in melting point of the polymer on its efficiency, the inventors worked on a series of polymers of the same family, for which only the molecular weight and the hydroxyl number varied. These polymers were polyethylene glycols (PEGS) whose characteristics are given in Table 3 below: TABLE 3MeltingState at roomMolecular weightpointHydroxyltemperature(g/mol)(° C.)number IOHPEG 600Liquid 60015-25° C.178-197PEG 1500Solid 150042-48° C.70-80PEG 35 000Solid35 00060-65° C.3-4 The graph in FIG. 3 shows the trapping efficiency at room temperature of a layer of WB12 substrate impregnated with polymer at a level of about 100% by weight (polymer mass=stainless steel mass). The capture efficiency greatly decreases with an increase in molecular weight (MW) and with a reduction in hydroxyl number (IOH). These two properties vary inversely with each other—the hydroxyl number is an indicator of the number of polymer chain ends (HO-ether chain-oxide-OH). If a polymer chain is shortened, the number of chain ends (OH) is increased while, on the other hand, its molecular weight decreases. These parameters are linked in the manner indicated in Table 4 below: TABLE 4Molecular weightHydroxyl numberPEG 1500Reduced by aIncreased by a↓factor of 2.5factor of 2.5PEG 600 The higher the melting point of a polymer is raised, so as to increase its mechanical strength, the less effective it appears. There is therefore a compromise to be found between mechanical strength and efficiency, which a person skilled in the art would readily be able to find from the present description. For the following examples, the inventors have chosen to adopt the polymers that have a melting point lying within the selected operating range of about 40° C. At this temperature, the polymer is waxy, that is to say non-liquid, in the form of a soft solid. In parallel with seeking a polymer whose melting point is 40°, the inventors produced polymer blends allowing a 40° C. melting point of the blend to be achieved. The basis of the blend was to combine a polymer having a high molecular weight and a high melting point with a low-mass polymer which provides it with the surface activity and the hydroxyl number. The blends prepared were Copol 7, Copol 11, Copol 2, Copol 9 and Copol 10 defined in Table 1 above. WB12 stainless steel wool was impregnated to an amount of about 100% by each of these blends, before the test on the test bed described above. The tests were carried out at 20° C. and 40% relative humidity. The results are given in the graph shown in the appended FIG. 4 which indicates the % by weight of ruthenium trapped for each disc D1, D2 and D3. The fact that the efficiency of the layer 3 is greater than that of the upstream layers results from saturation of these upstream layers with Ru. All the products tested were very effective, but the selection was made based on, as single criterion, lead time constraints and therefore commercial availability of the reactants. Since PEG 2000 and Copol 2 were available in sufficient quantity for carrying out impregnation on an industrial scale, the inventors took Copol 11 as reference product in this example. A blend may sometimes have drawbacks, such as demixing, which may result in the behaviour of the polymer being modified over time. This is why, advantageously, according to the invention, copolymers are preferred and especially those having all the characteristics of Copol 11 in terms of melting point and efficiency. A copolymer having these useful characteristics is, for example, Copol 14, which is a copolymer based on ethylene glycol, propylene glycol and butylene glycol, sold for example by Lambert Rivière (manufacturer ICI) under the trade name SYMPERONIC A20. The impregnation with the copolymer on the substrate is an important step in producing the trap cartridge according to the invention. If this is carried out incorrectly, and especially if the copolymer does not cover all of the substrate, for example all of the stainless steel wool as in this example, the cartridge may let some RuO4 through and the efficiency of the cartridge will in general be affected. In addition, it is necessary for the impregnation to be homogeneous in order not to create preferential paths. These trials were therefore aimed at controlling the amount of polymer or copolymer deposited on a substrate during the impregnation step. The first trials consisted in varying the concentration of the impregnation polymer. The substrate was a WB12 (trade name) stainless steel wool. The WB12 stainless steel wool specimens in this example had dimensions of 70×100 mm. They were immersed in the polymer solution and then placed on a metal (stainless steel) mesh before drying overnight at 40° C. The impregnation results are given in Table 5 below: TABLE 5[Copol 14]WB12Dry WB12 + CopolDegree of(g/l)(g)14 (g)impregnation1001.88023.8863107%501.87292.701144%251.83882.250122%101.94692.11909%52.12222.21354% The amount of polymer deposited therefore varied almost linearly with the concentration of the impregnation solution. The inventors therefore adopted, by practical choice, a 10 g/l impregnation solution for manufacturing the industrial traps from this wool. In the same way, trials were carried out with WB22 (trade name) stainless steel wool. This stainless steel wool differs from WB12 (trade name) by the diameter of the fibres (12 μm in the case of WB12 and 22 μm for WB22). The weight per unit area of each layer remained the same for both wools (300 g/m2). The inventors used a 25 g/l impregnation solution for this wool. The impregnation results are given in Table 6 below: TABLE 6[Copol 14] (g/l)Degree of impregnation4027%3018%2510%207.5% 15 6% The amount of polymer deposited therefore varied almost linearly with the concentration of the impregnation solution. The 25 g/l concentration was used here. To control the uniformity of polymer deposition on the surface of the substrate formed from stainless steel wool (WB12), the inventors subjected a WB12 disc impregnated with Copol 14 to a stream of ruthenium-containing air. They observed this specimen under a scanning electron microscope (SEM). They then compared the X-ray image of the specific lines of ruthenium on the same specimen and showed clearly that these two images were superposable and almost identical. This confirmed that the ruthenium was deposited uniformly on the surface of the stainless steel wool and therefore that the polymer covered the stainless steel wool fibres perfectly. Since nitrogen oxides or nitrous vapours (NOx) and ozone are possibly present in industrial gaseous effluents, the inventors carried out tests on the behaviour of the Copol 14-impregnated support with respect to NOx and ozone. The Copol family is sensitive to NOx and the reaction results in the formation of degradation products that are unstable and decompose, releasing heat. However, this reaction is neither explosive nor violent. In the same way as for NOx, stainless steel wool 30% impregnated with Copol 14 was subjected to an ozone stream using, for this, the test bed described above. The conditions were defined on the basis of the assumption of ozone generation by radiolysis of air. Specimens were subjected to a 2.5 m3/h stream of ozonated air with an ozone content of 0.7 g/m3 of wet air. Copol 14 seems to behave in a similar manner with respect to NOx and to ozone. However, the ozone-induced degradation phenomena are much less accentuated: less heat is generated, exotherms starting at 85° C. The solution presented in this example made it possible to avoid any modification of the installations in place. It consisted in placing the ruthenium trap of the present invention and the core of a cylindrical VHE filter of the second barrier. This was produced by cutting the upper strips of the filter and inserting a basket containing Copol 14-impregnated WB12 wool. Copolymer The copolymer selected in this example was Copol 14 (see Table 1).Substrate The substrate selected was a stainless steel wool because this offered a large contact area with the gaseous effluent for a lower head loss. The stainless steel wool WB12 (trade name) is composed of stainless steel fibres with a diameter of 12 microns. Its specific surface area is 13 m2/m2 for a wool 7 mm in thickness, i.e. about 1857 m2/m3 of non-compacted wool. Its weight per unit area is 300 g/m2, i.e. about 43 kg/m3 (again not compacted). Impregnation Several impregnation techniques were tested with the objective of impregnating the trap entirely; basket+2 kg of stainless steel wool. After many trials, it was decided to impregnate, sheet by sheet, stainless steel wool and to assemble the trap as follows. The intended degree of impregnation was 5% using the method of immersing the sheets of stainless steel wool. A quality criterion was set in this experiment, this consisting in discarding any sheet whose degree of impregnation was less than 2% or greater than 10%. Thus, for a trap containing about 2 kg of stainless steel wool, the maximum amount of Copol 14 was 200 g. The impregnation solution used was 10 g of copolymer per litre of water (see the example above). The impregnated wool was dried flat at 40° C. The Cartridge The basket-type metal support of the trap cartridge had the shape of a double cylinder, as shown in the appended FIG. 5, namely an internal cylinder (Ci) and an external cylinder (Ce). The internal cylinder (Ci) was made of perforated C10U12 stainless steel sheet, i.e. perforated with holes of 10 mm2 and a centre-to-centre distance of 12 mm (mesh). This cylinder was welded to a circular base (Bc) made of a stainless steel sheet of larger diameter, with a hole at its centre in order to allow passage of a shaft for supporting the filter element (if such a cylinder is needed; a support with no hole at its centre is of course possible). Eight layers of copolymer-impregnated stainless steel wool were wound around the first cylinder (Ci), which layers formed the substrate (S) as shown in FIG. 6. Two additional layers of stainless steel wool, not impregnated with copolymer, were then added on top. The external cylinder (Ce) covered the stainless steel wool and comprised a stainless steel mesh measuring 12.7×12.7. The base of the support was a flat bottom made of stainless steel, with a hole so as to allow passage of the shaft for supporting the VHE filter element. The trap cartridge therefore possessed in total 10 layers of stainless steel wool. The two layers wound last were not impregnated, that is to say contained no copolymer. They prevented any migration of the impregnation copolymer to the outside of the element. The cartridge (CA) obtained according to the invention is shown in FIG. 7. Its total mass, consisting of the basket+wool+copolymer, was about 8 kg distributed approximately in the following manner: basket structure: about 5.5 kg; stainless steel wool: between 2 and 2.5 kg; copolymer deposited: 200 g (maximum); Viton (trade mark) and silicone seals (idem VHE): 300 to 400 g.Insertion of the Cartridge According to the Invention into an Existing Unit To conclude, the trap cartridge manufactured according to the invention was inserted inside a VHE filter element consisting of glass fibres (F) supported by a perforated sheet (Tp). The whole assembly is shown in the appended FIG. 8. The supporting shaft (Ax) was therefore removed from the filter element (F) and the trap cartridge (CA) slid onto the inside of it. A silicone seal (J) was then applied at the ends of the trap cartridge in order to ensure adhesion and sealing between the trap cartridge and the filter element (F). The support shaft was then put back into place. The filter element and its trap cartridge were ready to be fitted into the shielded containers of vitrification shops. Head Loss Measurements The head loss measurements were carried out on this assembly for various flow rates of gas to be treated. They are given in Table 7 below. These values were measured on several trials to ±25%. The impregnation of the stainless steel wool with the copolymer therefore had, in the present case, no significant effect on the head loss. TABLE 7Flow ratem3/h100020003000Head loss in the VHE filterPa90180270elementHead loss in the trapPa40100200cartridge supportHead loss in the 10Pa110200360stainless steel wool layersTotalPa240480830 An experimental loop comprising, in this order; one or two experimental cartridges in series (Exp. 1 and Exp. 2) according to the present invention, no or one PVP cartridge, a filter paper and two PVP cartridges in series (PVP1 and PVP2), a volumetric counter and a pump were manufactured. The gaseous effluent passed through this loop in the above order. The diameter of the cartridges was 5 cm. The draw-off rates allowed flow speeds (empty drum) of 0.5 to 1 m/s to be achieved, these being representative of the flow speeds in the 2nd barrier VHE filters of existing irradiated fuel reprocessing plants. The device was fitted in a vitrification shop, downstream of the filters. A first series of trials was carried out on a 100% Copol 1-impregnated glass wool. The results are given in Table 8 below, in which 106Ru.Rh (Bq) represents the amount of ruthenium (and its descendent, rhodium) measured by radiometry. TABLE 8106Ru.Rh (Bq)Exp. 1PVP Filter paperPVP1PVP2Volume (m3)1 week3206.2<5.7<8.6<76202 weeks,4104.94.2<7.7<6.7>200newcartridge Over one week of operation, the results were encouraging, the PVP just downstream of the experimental cartridge being at the limit of detection, indicating that no leakage had taken place. A second series of trials was carried out on WB12 stainless steel wool impregnated with Copol 1 to 100%. The cartridge consisted of 8 layers of WB12. It was left in place for an endurance test. The results are given in Table 9 below: TABLE 9106Ru.Rh (Bq)Exp. 1PVPFilter paperPVP1PVP2Volume (m3) 7 daysns<6.35.45.5<7.853314 daysns<7.86.25.8<6.130921 daysns189.216<6.335931 days6500600160110040122638 days59002500<6.8<8.217396(ns: not sampled)106Ru.Rh (Bq) represents the amount of ruthenium (and its descendent, rhodium) measured by radiometry. After 21 days testing, the inventors suspected a leak and the cartridge was removed 7 days later. The results on the downstream PVP, and the repositioning of the cartridge for 7 days, confirmed this leak, which was due to slow migration of the Copol 1, this product being too fluid under the test conditions (40° C.). A third series of trials consisted in evaluating the efficiency of a WB22 stainless steel wool impregnated with Copol 2 sold for example by Lambert Rivière (manufacturer: ICI), under the trade name SYMPERONIC A11. It was used in an amount of 22%. The cartridge consisted of a single layer of WB22. The results are given in Table 10 below: TABLE 10106Ru.Rh (Bq)EmptyExp. 1cartridgeFilter paperPVP1PVP2Volume (m3)7 days400011074927.51054 A single layer already proved to be very effective, despite a flow speed from 2 to 3 times higher than during the previous trials. The fourth trial was an endurance trial in a configuration similar to that used for the second barrier traps, namely 8 layers of WB12 impregnated with 5.7% Copol 14 (these 8 layers were distributed over 2 cartridges (Exp. 1 and Exp. 2), i.e. 8 cm in thickness). The results are given in Table 11 below: TABLE 11106Ru.Rh (Bq)Exp. 1Exp. 2Filter paperPVP1PVP2Volume (m3)9 days 860028057712585820 daysnsns3.7ns597025 daysnsns4.1<7.4<7.136932 daysnsns<5.4<8.4<4.962139 daysnsns<7<9.6<8.259649 daysnsns<7.2<4.2<8.872356 daysnsns<4.7<3.1<4.452863 daysnsns<5<6.5<7/70 daysnsns6.7<7<6.958679 daysnsns<6<7.2<775986 daysnsns<6.2<4.2<6.850493 daysnsns<5.2<7.4<8.7539100 days nsns<4.7<5.9<7561109 days nsns178<8830118 days nsns26<7.9<7.4563124 days nsns22<9.2<6.5443133 days nsns18<8.7<6.8619140 days nsns10<7.4<7.4585144 days 34 000430<8.1<7.4<7.5320ns: not sampledAfter 144 days of the trial, corresponding to the treatment of 11 790 m3, the experimental cartridges were removed without any lowering of efficiency being observed.A sealing fault was identified, manifested by a slight activity on the PVPs. The cartridges were removed in order to fit seals and were counted before being reinstalled. According to the invention, the ethylene glycol, propylene glycol and butylene glycol polymers and copolymers can be used as reactants added to the scrubbing water in a gas scrubbing unit (packing column, venturi, etc.). Specifically, comparative trials were carried out with various reactants, in which RuO4-laden air flowed over the surface of the liquid. The physical parameters (geometry and air speed) were the same for all the trials, only the chemical composition for the solution varying. The results given in Table 12 below show, for example, that an ethylene glycol/propylene glycol copolymer, called here Copol 1, is very effective for absorbing RuO4. TABLE 12pHRuO4RuO4(measuredgeneratedabsorbed%or(10−6 mol)(10−6 mol)absorbedcalculated)Trials with pure waterPure water:19.046.0231.65.7Trial APure water:9.803.2132.85.7*Trial BTrials in the presence of reactantsNa2CO3(0.4M) +19.734.0220.410.1NaHCO3 (0.2M)Na2CO3(0.4M) +9.432.0021.29.5NaHCO3 (0.2M)Buffer (pH = 7)3.831.0427.26.9Na2SO49.482.6427.87.5HNO35.311.7633.11.60.01M sodium21.697.1332.9—hydroxide0.1M sodium11.926.6655.9hydroxide:Trial A0.1M sodium23.6113.3756.6hydroxide:Trial B1M sodium11.6911.1795.6hydroxide:Trial A1M sodium12.1110.183.4hydroxide:Trial B0.5M NHA3.793.0680.70.0475M NHA7.156.2587.55% Copol 113.2813.198.6
053961412	description	DETAILED DESCRIPTION OF THE INVENTION The various embodiments of the present invention are best understood by referring to the FIGUREs, wherein like numerals are used for like and corresponding parts of the various drawings. Radioisotopes have tremendous power density that can be converted to electricity via P-N or N-P junctions. These could be put to use keeping SRAM cells alive or in making very lightweight batteries. But these are just some of the applications that the present invention addresses. The present invention, therefore, provides an internal radioisotope battery or power cell for integrated circuit memory and other low-power applications. The energy density of radioisotopes is unparalleled by any chemical reaction such as those that conventional chemical batteries use. This relationship is based in physics and will hold true regardless of advances in power cell technology. The present invention recognizes the difference between these two physical regimes to provide a method and system to power integrated circuits by using a radioisotope associated with one or more P-N junctions. These power cells may be placed in association with an electronic circuit such as a data processing circuit as a standby power source so that a primary power failure will not destroy the contents of a memory, for example. The present invention may also prove practical in outer space applications to provide power to an entire system. The problem of particulate radiation leaking into integrated circuitry and causing damage or power disruption is solved in the present invention by placing the power source at least twice the distance from the circuitry that the particles travel in the semiconductor material that forms part of the power cell. For example, by placing a power source that uses .alpha. radiation at least 50 microns from any circuitry in a silicon semiconductor material, no interruption or damage to associated circuitry occurs. This is because the distance an .alpha. particle can travel in silicon is 25 microns. That a small amount of radioactive material can produce a great deal of power can be seen by the following example. An example of this phenomenon appears in the radioisotope Am.sub.241, which has a half-life of 458 years. Suppose that a source composed of Am.sub.241 is placed in association with a P-N junction of a silicon semiconductor material. The .alpha. particles leaving the radioactive material have an energy of 5.5 MeV per particle. In the semiconductor material, an electron-hole pair requires 3.6 eV to form. Thus, at the P-N junction 1.53.times.10.sup.6 electron-hole pairs can form from each .alpha. particle traveling through the silicon semiconductor material. It can be shown using these principles that for every 0.23 grams of .alpha.-producing radioisotope, one watt of energy can be produced in the semiconductor material. Based on this output and the charge requirements of a static RAM (SRAM) cell, it can also be shown that as little as 58 micrograms of .alpha.-producing radioisotope are necessary to maintain the SRAM charge. The present invention can, therefore, use these small amounts of .alpha. -producing radioactive isotopes to maintain SRAM charges in the event of a primarily power failure. Notwithstanding design considerations such as voltage fluxuations, heat dissipation, and damage due to radioactive particles traveling through the semiconductor material, the present invention provides an attractive source of power for electronic circuitry. As yet a further example of the present inventions utility, one embodiment may provide an energy source that is easily adaptable to micromachines, micromotors, and general nanomechanics. Since .alpha. fluxations occur as .sqroot.N .vertline.N, voltage fluxations should not prohibit use of .alpha.-producing radioisotopes in most applications. On the other hand, since radioisotopes produce approximately 2.5 watts of heat energy for every one watt of electrical energy, dissipating heat energy in the circuit is a design consideration. One solution, however, is to place the radioisotope power cell under a bond pad to both protect the associated circuitry and to make the pad and bond leads operate as a heat sink. Another alternative is to place the radioisotope on the reverse side of a chip or printed circuit board from that containing the integrated circuitry to protect the associated circuitry from potentially harmful .alpha. particles and allow for better heat dissipation. FIG. 1 shows one power cell 10 of the present invention. In power cell 10, semiconductor material 12 includes an N material 14 and a P material 16 that form P-N junction 18. An equally useful scheme is to form an N-P junction with N material occupying the relative position of P material 16 and P material occupying the relative position of N material 14. Lead 20 electrically connects to N material 14, while lead 22 electrically connects to P material 16. Shown conceptually in FIG. 1, .alpha. source 24 covers N material 14 and P material 16 causing .alpha. particles 26 to travel into and through N material 14 and P material 16. This produces the desired electron-hole pairs. The internal fields of the P-N junction separate these pairs and allow the extraction of useful power through leads 20 and 22. Power cell 10 of FIG. 1 may be formed first by diffusing P region 16 into N region 14 of semiconductor material 12. The .alpha. source 24, in this example, may be painted on or otherwise deposited on semiconductor material 12 using a wide variety of techniques available to semiconductor device manufactures. These include techniques such as vapor deposition, sputtering or thin film deposition, electroplating, and polymer bonding. Another method of forming a radioactive source may be to use a tape or polymer containing tritium as a .beta. particle emitting radioactive source, instead of an .alpha. particle emitting source. Leads 20 and 22 may be made of aluminum or other material to provide electrical connection from N material 14 and P material 16, respectively. The .alpha. source 24 may be an uranium, thorium, or other material or may be artificial isotope such as americium or californium. These sources are inexpensive and commercially available and are practical within the purpose of the present invention. Other radioisotope may be selected from the Handbook of Chemistry and Physics--56th, CRC Press (Cleveland, Ohio 1975), pp. B-252 through B-336, according to their half-lives, fission products, and other characteristics. It may be desirable to select .alpha. or .beta. emitters that do not emit .gamma. radiation. This is because .gamma. radiation are more difficult than is .alpha. or .beta. radiation. Although embodiment 10 shows .alpha. source 24 as the radioactive source of one embodiment, other radioactive sources such as .beta. emitters or .gamma. emitters may be used within the scope of the present invention. What is important is to have a radioactive material that emits charged particles that travel through semiconductor material 12. Other design or engineering and environmental considerations may dictate the particular type of radioactive material to use. As a further example, one particularly attractive radioisotope is tritium. Tritium emits a .beta. particle that is absorbed very shallowly, and this permits semiconductor material 12 to have a very shallow P-N junction. In addition, the half-life of tritium is 12 years which for many power applications is advantageous. Tritium, therefore, is not as dangerous because its half-life is not long and it does not localize in the human body. That is, it is not ones of the more dangerous radioactive materials, whereas plutonium or other heavy materials produce physically damaging radioactive particles. FIG. 2 shows another power cell 30 of the present invention that forms a "sandwich-type" configuration with .alpha. source 24. In FIG. 2, semiconductor material 12 includes N material 14 and P material 16 each associated with P-N junction 18. Lead 20 connects electrically to N material 14, while lead 22 connects electrically to P material 16. On the opposite side of .alpha. radioactive source 24 appears semiconductor material 32 that includes N material 34 and P material 36 each associated with P-N junction 38. Lead 40 connects to N material 34 while lead 42 connects electrically to P material 36. Because the .alpha. particles from .alpha. source 24 emit in all directions, those .alpha. particles that travel in a direction opposite that of particles 26 of FIG. 1 will not reach semiconductor material 12. In large part, power cell 30 of FIG. 2 addresses this situation. By forming a sandwich-type configuration, .alpha. particles that are emitted upwardly are captured by semiconductor material 32, while those that emitted downwardly are captured by semiconductor material 12. Leads 20 and 40 connect to N materials 14 and 34, respectively. Likewise, leads 22 and 42 connect to P materials 16 and 36, respectively. Forming power cell 30 of FIG. 2 is similar to forming power cell 10 of FIG. 1. An exception to this statement is that .alpha. source 24 may fully cover P material 16 and N material 14. Over .alpha. material 24 leads 40 and 42 may be formed, after which semiconductor material 32 may be formed to include P material 36 and N material 34. A variety of well-established techniques may be employed to form the sandwich-type embodiment 30 of FIG. 2. FIG. 3 shows a further power cell trench configuration 50 of the present invention wherein semiconductor material forms a trench 61 for receiving .alpha. source 54. In particular, N material 56 of semiconductor 52 forms P-N junction 58 with P material 60. Lead 62 electrically connects to N material 56, while lead 64 electrically connects to P material 60. The trench power cell 50 of FIG. 3 may have particular application in forming integrated circuits that use DRAMS. The P material 60 may be formed, for example, in a trench shape that is several microns deep and approximately 3 microns wide. By diffusing P material 60 within trench 61, the desired configuration is achieved. Placing contact 64 in connection with P material 60 and lead 62 in connection with N material 56 has the effect of trapping .alpha. radiation-producing source 54 within trench 61 so that little or no radiation passes through semiconductor material 52 to contaminate circuitry or other things on the top or associated with the top portion of semiconductor material 52. The trench 61 of FIG. 3 provides an aspect ratio of approximately 20:1 so that the likelihood of radiation passing out of trench 61 is essential zero. The trench configuration 50 of FIG. 3 may also be placed under a bond pad to provide a significant amount of power to an associated circuit with essentially no harmful effects to the associated integrated circuitry. FIG. 4 shows a further application 70 of the present invention. In particular, semiconductor material 12 includes N material 14 that forms with P material 16 a P-N junction 18. Lead 20 connects to N material 14, while lead 22 electrically connects to P material 16. The .alpha. source material 24 covers semiconductor material 12. In addition, oxide layer 72 covers .alpha. source material 24. Bond pad 74 covers .alpha. source 24. The application 70 of FIG. 4 is a design that may be used with bond pad 74 over oxide layer 72. Because bond pad 74 is typically large and consumes a considerable amount of surface area, a power cell using .alpha. source 24 over P-N junction 18 could serve as a small standby power source. While this configuration may not generate a substantial amount of current, it may provide a trickle amount of current to keep circuit information stored in the event of a loss of primary power. In CMOS circuits, very small amounts of current are necessary to maintain stored information in a circuit. The application 70 of FIG. 4, therefore, provides a trickle amount of current that would be sufficient to maintain a charge on certain components, such as SRAM or other memory device of a CMOS integrated circuit. In addition, the power cell in configuration 70 may be placed on the back of semiconductor chip without disrupting the operation of the associated integrated circuitry. This concept is shown even more clearly in FIG. 5. FIG. 5 shows a further application 80 of the present invention. In FIG. 5, semiconductor material 12 includes N material 14 and P material 16 in association with P-N junction 18. Lead 82 connects to N material 14 and passes through to surface 84 of semiconductor material 12. Likewise, lead 86 connects to P material 16 through semiconductor material 12 to top side 84. Application 80 of FIG. 5 protects active circuitry 88 from potentially harmful .alpha. particles of .alpha. source 24 by physically isolating the source such a distance from the circuitry that no particles can hit the circuitry. The FIG. 5 application 80 makes use of what would most likely be an otherwise unused backside 81 of semiconductor material 12. Placing .alpha. source 24 over P material 16 and placing holes for leads 82 and 86 through semiconductor material 12 permits leads to go from N material 14 and P material 16 to active circuitry 88. A large number of such sources could be placed on semiconductor material 12 to provide standby power to active circuitry 88, for example. This is shown more particularly in FIG. 6. FIG. 6 shows yet another application of the present invention in the form of power cell array 90 that includes semiconductor chip 92 having embedded within it numerous micropower cells for powering associated electronic circuitry. For example, electronic semiconductor chip 92 includes substrate 94 embedded within which are larger power cells 96 and 98 that may be positioned under the bond pads in a configuration similar to that shown in FIG. 4. Also, on semiconductor chip 92 are arrays 100, 102, 104, and 106 that include microminiature radioactive sources such as power cell 108. Power cell 108 may be used to provide standby power to circuitry that may subsequently be placed on semiconductor chip 92. Silicon semiconductor chip 92 even further includes radioactive sources such as radioactive sources 110 that are miniature sources to provide more power than the power cell 108 but not the amount of power available from bond-pad power cells 96 and 98. Power cell array 90 of FIG. 6 may be used to support a complicated integrated circuit. For example, if an associated integrated circuit includes static RAMs, SRAMs power cell array 90 has the ability to maintain a charge on the static RAMs by providing very tiny trickle currents to the static RAMs. By depositing power cells 108 in arrays such as array 100, 102, 104, and 106, circuitry on the opposite side of power cell array 90 can be energized so that information in the SRAMs or other memory circuitry is not lost upon a failure of the primary power source. Because of the high energy density and lower power requirements of such integrated circuit devices, each power cell 108 may be on the order of a cubic micron or smaller. Depending on whether .alpha. particles, .beta. particles, or .gamma. particles are used to provide power, different size power cells 108 may be used. FIG. 7 shows yet a further application 120 of the present invention that embeds an array such as array 122 within a semiconductor substrate 124. Semiconductor substrate 124 includes solar cells 126 and 128. Power cell array 122 is positioned between solar cells 126 and 128 and may electrically connect with associated circuitry that provide standby power to circuitry associated with semiconductor material 124 in the event of insufficient photon energy to generate amounts of power from solar cells 126 and 128 that the associated circuit may require. Invented by TI research engineers Jules Levine, Millard Jensen, Milford Hammerbocker and Gregg Hodgekiss, spherical solar cells possess a broad range of applications. Solar spherical technology can bring low-cost, reliable electrical power to remote areas and serve as an energy source for industrial telecommunications. U.S. Pat. No. 4,637,855 and its progery by Levine, et al. is assigned to Texas Instruments Incorporated, describes the use of solar spherical cells, and is here incorporated by reference to provide examples of these types of crystalline silicon spheres. The power cell array 122 of the present invention, therefore, improves the operation of solar cells 126 and 128, to provide a minimum amount of current in the event of insufficient solar energy to provide the necessary power to associated circuitry. OPERATION Although it is clear how the radioisotope power cells of the various above embodiments operate, for completeness, the following describes how one embodiment produces electrical current. Referring, for example, to FIG. 1, power cell 10 generates power by an .alpha. source 24, such as Am.sub.241, directing .alpha. particles 26 into P material 16 and N material 14. Each .alpha. particle 26 can deposits six MeV into semiconductor material 12. As the .alpha. particles 26 travel through semiconductor material 12, they form electron-hole pairs. In fact, from each .alpha. particle approximately 1.6.times.10.sup.6 electron-hole pairs may form. The electron-hole pairs are swept to their corresponding sides of P-N junction 18 to form electrons in N material 14 and holes in P material 16, thereby causing a current to flow across P-N junction 18. This causes current to flow through leads 20 and 22. This current may be used for powering associated electronic circuitry. In summary, therefore, the present invention provides an electrical power source in the form of radioisotope power cells that include a semiconductor material and at least one P-N junction within the semiconductor material. A radioactive source is associated with the P-N junction and emits electrically-charged radioactive particles into the semiconductor material. This produces electron-hole pairs in the semiconductor material. As the electron-hole pairs form, they generate an electrical current that passes through the P-N junction to cause electrical current to flow through leads 20 and 22 and from electrical source 10. The radioactive particles may be .alpha. particles, .beta. particles, .gamma. particles or other radioactive particles. A technical advantage of the present invention is that it provides long-lived, inexpensive power from relatively minuscule amounts of radioactive material to provide power to electronic circuitry. Because of the large magnitude of deposited energy per radioactive decay, only a very small amount of the radioactive source material is necessary to produce a sufficiently large number of electron-hole pairs to power electronic circuitry connected with the power cells. Therefore, a sufficient amount of shielding can be applied to the radioactive source to prevent radiation emitting from the radioactive source from affecting associated electronic circuitry. Yet another technical advantage of the present invention is that the power cells may be formed in a variety of configurations or embodiments for the purpose of different applications. For example, one embodiment includes the use of an array of power cells distributed and embedded within an electronic circuit board for providing standby power in the event of a primary power source failure. Another embodiment includes embedding the radioactive power source in a trench formed of a P-N junction within a semiconductor material. This also will discretely configure the radioactive power source. Still another embodiment has the power cells on one side of a semiconductor chip while active integrated circuitry appears on the opposite side. This will also prevent the radioactive source from affecting the integrated circuitry. This flexibility is due primarily to the small size requirements of the radioactive source. Still another technical advantage of the present invention is that a wide variety of radioactive materials may be used as the radioactive source for emitting the radioactive particles. Thus, based on engineering design limitations, the present invention may use a long-lived, low-energy system for some applications. Other applications may require short-lived high-energy radioactive sources. Furthermore, based on the engineering design objectives, it may be more advantageous to use .beta. or .gamma. radiation sources instead of .alpha. radiation sources. The present invention contemplates this degree of flexibility in radiation source selections. The above description and the accompanying drawings, therefore, are merely illustrative of the application of the principals of the present invention and are not limiting. Numerous other embodiments are arrangements which employ the principals of the invention and which fall within its spirit and scope may be readily devised by those skilled in the art. Accordingly, the invention is not limited by the foregoing description, but by the scope of the appended claims.
044366779	claims	1. A method of making a pellet from a powder comprising: (A) placing said powder in a heat-shrinkable self-supporting bottle; (B) sealing said self-supporting bottle; (C) isostatically pressing said self-supporting bottle at a temperature which causes it to shrink at about the same rate that the powder within it is compressed; and (D) decomposing said self-supporting bottle and sintering said powder. (A) preparing a free-flowing fissile powder and a free-flowing fertile powder; (B) mixing said free-flowing fissile powder with said free-flowing fertile powder; (C) filling a heat-shrinkable self-supporting bottle with said mixed powders; (D) sealing said self-supporting bottle; (E) heating and isostatically pressing said self-supporting bottle so that the bottle shrinks at about the same rate that the powder within it is compressed; and (F) decomposing said self-supporting bottle and sintering said powder. 2. A method according to claim 1 wherein said powder is a mixture of fissile and fertile nuclear fuel. 3. A method of making a nuclear fuel pellet comprising 4. A method according to claim 1 wherein said powder is fissile nuclear reactor fuel and a fertile core of nuclear reactor fuel is placed in said self-supporting bottle before said powder. 5. A method according to claim 3 wherein said fissile powder is a mixture of .sup.235 UO.sub.2 and PuO.sub.2 and said fertile powder is .sup.238 UO.sub.2. 6. A method according to claim 3 wherein said fissile powder is UO.sub.2 and said fertile powder is ThO.sub.2. 7. A method according to claim 3 wherein said heat-shrinkable self-supporting bottle is made of cross-linked polyethylene. 8. A method according to claim 3 wherein said self-supporting bottle is sealed with a plug which is fused to said self-supporting bottle. 9. A method according to claim 3 wherein said mixed powder is about 20 to about 25% by weight fissile powder and about 75 to about 80% by weight fertile powder. 10. A method according to claim 3 wherein said mixed powder is about 1 to about 5% by weight fissile powder and about 95 to about 99% by weight fertile powder. 11. A method according to claim 3 wherein said powders are mixed only as needed to fill said self-supporting bottle. 12. A method according to claim 3 wherein said self-supporting bottle is heated at about 100.degree. to about 150.degree. C. and pressed at a pressure sufficient to reduce its volume by about 40 to about 60%. 13. A method according to claim 3 wherein said self-supporting bottle is pressed at about 30,000 to about 60,000 psi. 14. A method according to claim 3 wherein said sintering is under conditions sufficient to reduce the volume of said self-supporting bottle by about 40 to about 60%. 15. A method according to claim 3 wherein said sintering is performed under a greater than atmospheric partial pressure of oxygen at a temperature of about 1100.degree. to about 1400.degree. C. which is followed by reduction in hydrogen. 16. A method according to claim 3 including the additional last step of grinding said pellets to a desired tolerance. 17. A method according to claim 3 wherein said free-flowing fertile powder and said free-flowing fissile powder are prepared by the sol-gel technique.
	abstract	Disclosed are examples of methods and systems for cutting up a reinforced concrete mass, in which a drilling tool is provided. In various embodiments, the drilling tool comprises: a drill tube carrying a cutter member; a device for causing the drill tube to vibrate, the device comprising a vibration generator for generating longitudinal vibration in the drill tube; a device for injecting a drilling fluid at the distal end of the drill tube; and a device for moving the drill tube along its longitudinal direction. In the disclosed methods and systems, the reinforced concrete mass is cut up by drilling at least one hole with the help of the drill tool by causing the drill tube to vibrate while injecting the drilling fluid into the mass from the distal end of the drill tube.
	description	This application is based upon and claims the benefit of priority from Japanese patent application No. 2006-241331, filed on Sep. 6, 2006, the disclosure of which is incorporated herein in its entirety by reference. 1. Field of the Invention The present invention relates to a variable shaped electron beam lithography system for drawing a figure pattern including an oblique line with an arbitrary angle by forming a single electron beam shot in the same shape as the figure pattern, and a method for manufacturing a substrate. 2. Description of the Related Art In a photo mask electron beam lithography system including an electron optical system having a 50 kV electron gun, a raster scan system and a variable shaped beam system (hereinafter, called “VSB system”) have been developed, and at the present day, both of them are put into practical use. The raster scan system is, as shown in FIG. 1A, a system which scans a resist layer of a photographic dry plate (blank) by moving the position of a spot of beam irradiation 31 and by projecting electron beam 30 at a position of target drawing pattern 29. On the one hand, the VSB system is, as shown in FIG. 1B, a system which divides target drawing pattern 29 into a plurality of rectangular figures, forms electron beam shot 32 into an electron beam shape coincident with the divided rectangular figures for each of them, and draws patterns on a dry plate or a semiconductor wafer. The raster scan system has higher drawing accuracy, but lower throughput because of a large number of shots. Therefore, in the field for manufacturing a critical photo-mask, the VSB system is primarily adopted because the VSB system is expected to draw a fine pattern of several hundred μm accurately at a high speed. A lithography system of the VSB system, as shown in FIG. 2, forms an electron beam emitted from electron gun 1 into rectangular beam 7 through two apertures 101, 102. Then, the formed rectangular beam 7 is reduced by reducing lens system 6, and the deflection angle of the beam is changed by deflector 9 of object lens system 8 to converge and subject to a drawn target substrate 10. Specifically, first aperture 101 and second aperture 102 for forming a beam are fixed as shown in FIG. 3, and they have a square opening portion in a plate to shield against an electron beam. Therefore, an electron beam which passed through opening portion 101a of first aperture 101 is formed into the same, square shape as opening portion 101a (FIG. 4 (a)). Then, the electron beam is shifted by deflector 5 of forming lens system 4 relative to XY rectangular coordinates of second aperture 102 in the X-axis direction and/or in the Y-axis direction, generating rectangular beam shape 11 formed by a common opening portion between two aperture 101, 102 (FIG. 3, FIG. 4 (b)). That is, by allowing only a part of the electron beam which passed through first aperture 101 to pass through opening portion 102a of second aperture 102, a desired, rectangular beam 7 is formed. Subsequently, rectangular beam 7 is reduced by reducing lens system 6 to project a desired, rectangular beam shot 12 onto the drawn target substrate 10 (FIG. 3, FIG. 4 (c)). Nowadays, as an LSI pattern is made finer in higher integration, complexity in an LSI pattern shape drawn on a photo-mask is increased, and also the number of LSI patterns tends to be increased exponentially, as the process generation goes forward. This means that, in a process for directly drawing an LSI pattern on a dry plate or a semiconductor wafer, patterns to be drawn by a lithography system are enlarged, or the number of drawing figures divided into a rectangle by the VSB system is increased. This tendency may be a factor for largely lowering productivity, because the time period required to draw is approximately linearly increased corresponding to an increase in the number of figures. On the one hand, in drawing a trapezoidal FIG. 13 in which both of the two opposite sides have an oblique line with an arbitrary angle, as shown in FIG. 5 (a), a beam formation method by the VSB lithography system shown in FIG. 2 cannot form an electron beam shot that has an oblique line relative to the rectangular coordinate axis of the target that is to be, drawn (hereinafter, called “drawing rectangular coordinate system”). Therefore, as shown in FIG. 5 (b), the trapezoidal figure is divided into a rectangular figure and a triangular figure, further the triangular figure is finely divided into a plurality of elongated rectangular figures, and single electron beam 14 is formed into a rectangular shape coincident with each of the divided figures, and converged and subjected, respectively. In addition, the lithography system (from NuFlare Technology, Inc., EBM series) normally equipped with the second aperture having an opening side at 45° angle can form a beam shot into a triangle having an oblique side at 45° angle, but cannot be applied, when the triangle has an oblique side at an arbitrary angle. Of course, if an aperture for drawing obliquely is provided, for now, it may be addressed, but an oblique side with any arbitrary angle may not be covered, then it cannot be an actual solution. Further, in the case of FIG. 15 obtained by rotating trapezoidal FIG. 13 shown in FIG. 5 (a) around the center of the figure by an arbitrary angle, as shown in FIG. 6 (a), all four oblique side portions have to be approximated by a plurality of elongated rectangular figures 16 parallel or vertical relative to the XY drawing rectangular coordinate system. Therefore, the total number of divided drawing figures of the figure shown in FIG. 6 (b) is largely increased compared to that of the figure shown in FIG. 5 (b). In current design of LSI pattern, the mainstream is a system called “Manhattan System” in which a pattern is arranged along an X-axis or a Y-axis direction in the XY drawing rectangular coordinate system. While there have been significant advances in the wiring design of LSI patterns, an element arrangement in a direction that has an arbitrary angle is expected to be a useful means to allow a design region to be used effectively, but this arrangement is not permitted in the current Manhattan System. However, in addition to drawing a photo-mask having LSI design involving such oblique arrangement, in the case of forming a pattern of MEMS (micro Electro Mechanical Systems) or a pattern of a nanoimprinting mold for an optical element, a complex pattern using many oblique sides with an arbitrary angle has to be drawn. As the result, in a drawing process using the current VSB lithography system, the number of the divided drawing figures becomes enormous. Therefore, to improve productivity in this process, the largest, technical challenge is to reduce the number of the divided figures in order to shorten the drawing time. Then, as for a method for forming an oblique pattern, there are technologies disclosed in Japanese Patent Laid-Open No. 61-255022 and No. 9-82630. In Japanese Patent Laid-Open No. 61-255022, there is disclosed a technology that, by rotating a first aperture and a second aperture shown in FIGS. 13 and 14 in synchronization with each other, a shape of a beam shot is formed into a rectangular pattern having two oblique sides opposite to each other. However, in this drawing method, the other two opposite sides except the opposite, oblique side portions do not become parallel or vertical to the XY drawing rectangular coordinate system. Therefore, there arises a problem of lack of versatility, because it is difficult to connect with rectangular shaped electron beam shot having four sides along the X/Y-axis direction in the XY drawing rectangular coordinate system. Further, in Japanese Patent Laid-Open No. 9-82630, disclosed is a technology that, in a conventional VSB lithography system having the first and second fixed aperture as shown in FIGS. 2 and 3, a third rotatable aperture having a slit is provided. In this lithography system, in order to conform to a drawing figure pattern including two opposite, oblique sides parallel to each other that are inclined at an arbitrary angle, a rectangular beam formed by the first and second aperture is formed by the slit of the third aperture rotated up to an angle made between the parallel, oblique sides of the target drawing pattern, thereby the oblique side portions are formed. Two opposite sides, except the oblique side portions, are formed horizontally or vertically relative to the XY drawing rectangular coordinate system, by both the first and second aperture. In such a drawing system, a beam shape formed by the third aperture becomes a similar figure to a drawing figure, and the reduction rate in projecting onto a wafer etc. is represented by the ratio of the distance between two oblique sides of a target drawing figure, to the slit width (fixed value) of the third aperture. Therefore, the reduction rate of the formed beam has to be changed, every time a size of the divided figures to be drawn becomes different, and a settling time required for calibration for each reduction rate adjustment is accompanied. Further, when the target drawing figure is in a trapezoidal shape in which opposite oblique sides have an arbitrary angle and are not parallel to each other (FIG. 5 (b), FIG. 6 (b)), the number of divided figures involved in drawing a figure pattern is increased. The total required drawing time of the VSB system is approximately represented as the product obtained by multiplying the sum of the settling time necessary for a system to deflect a beam for each drawing and the beam emission time in drawing figures (in exposing resist) by the total number of figures to be drawn. Therefore, the larger the total number of drawing figures is, the more the total drawing time is increased. Further, in the conventional VSB lithography system which divides a drawing figure pattern having opposite, oblique line portions that are inclined at an arbitrary angle into a rectangular figure, and which converges and emits a formed beam for each rectangular figure, the total drawing time is prolonged linearly due to an increase in the total number of divided figures. Therefore, compared to a drawing figure pattern having a completely rectangular shape the side of which are each parallel or vertical relative to the X-axis or the Y-axis direction in the XY drawing rectangular coordinate system, in a drawing figure such as a parallelogram, a trapezoid, and a rotated trapezoid formed by rotating the trapezoid around the center of the figure, the number of rectangular figures approximating oblique side portions is increased, and the total drawing time is prolonged accordingly. To shorten the total drawing time, setting a size of a divided rectangular figure to be coarse may be also effective, but on the other hand, approximate accuracy in oblique side portions is degraded, so that it cannot be a fundamental solution. An object of the present invention is to achieve a drawing figure pattern based on the very small number of divided figures compared to that of a related art in order to largely shorten the total drawing time, in drawing, by the VSB system, a figure pattern including an oblique line figure portion including two opposite, oblique lines, each forming an arbitrary, different angle relative to a coordinate axis in an XY drawing rectangular coordinate system. In addition, “XY drawing rectangular coordinate system” means a rectangular coordinate system for representing the shape and position of a figure pattern to be drawn on a drawn target substrate such as a dry plate or a semiconductor wafer, and a lithography system also has a rectangular coordinate system corresponding to it, and in drawing figure patterns, the rectangular coordinate system is used to control hardware, such as an aperture, based on figure pattern information. Further, “oblique line, each forming an arbitrary, different angle relative to a coordinate axis of the XY drawing rectangular coordinate system” or “oblique side” means that a side of a drawing figure pattern forms an arbitrary angle relative to the X-axis direction/the Y-axis direction in the XY drawing rectangular coordinate system except when it is parallel or vertical. According to the present invention, to achieve the object described above, when a figure pattern to be drawn on a drawn target substrate includes an oblique line figure portion including two opposite, oblique lines, each forming an arbitrary, different angle relative to the coordinate axis in the XY drawing rectangular coordinate system, a single electron beam is formed into the same shape as the oblique line figure portion so as to draw the figure pattern. Further, when the figure pattern described above is a ring pattern, the drawing region between an outer peripheral line and an inner peripheral line of the ring pattern is equally divided into a plurality of the same trapezoidal figures in order to approximate the drawing region, and a single electron beam is formed for each of the trapezoidal figures divided into the same shape as the trapezoidal figure so as to draw each of the trapezoidal figures in sequence. To draw the oblique line figure and the trapezoidal figure as described above, a variable shaped electron beam lithography system according to the present invention is configured as follows. That is, the lithography system of the present invention includes a first, second and third aperture for forming a single electron beam in each of the rectangular opening portions that are provided, and draws a figure pattern using a single electron beam shot formed by sequentially passing the beam through the first, second and third aperture in sequence. In each of the first and second aperture described above, a rotary drive mechanism is provided, which rotationally drives the aperture around an optical axis up to an arbitrary angle from 0 to 360°. Further, in the third aperture, a variable slit width mechanism is provided, which varies an opening slit width of the rectangular opening portion provided in the aperture. This lithography system operates as follows, when a figure pattern that includes two opposite, oblique sides, each which forms an arbitrary angle relative to the coordinate axis in the XY drawing rectangular coordinate system (a figure such as a triangle, parallelogram or trapezoid), is drawn on a drawn target substrate. A position at which each side of the rectangular opening portion of each aperture becomes parallel or vertical to the coordinate axis in the XY drawing rectangular coordinate system is defined as a rotary reference for each aperture. The first aperture is rotated from the rotary reference by an angle coincident with an angle of one of the two oblique sides, and the second aperture is rotated from the rotary reference by an angle coincident with an angle of the other of the two oblique sides. Then, a single electron beam is formed into a shape of the figure pattern using the rectangular opening portions of the first and second aperture that has been rotated, and the rectangular opening portion of the third aperture, and the single electron beam is projected onto the drawn target substrate. In addition, the drawn target substrate means a dry plate (blank) or a semiconductor wafer etc. Further, the lithography system configured in the way described above operates as follows, in drawing, on the drawn target substrate, a figure pattern (trapezoidal figure) which is a quadrangle and which is composed of two opposite, oblique sides, each forming an arbitrary angle relative to the coordinate axis in the XY drawing rectangular coordinate system and two opposite, parallel sides parallel or vertical to the coordinate axis in the XY drawing rectangular coordinate system. The first aperture is rotated from the rotary reference described above by an angle coincident with an angle of one of the two oblique sides described above, and the second aperture is rotated from the rotary reference by an angle coincident with an angle of the other of the two oblique sides. Further, the opening slit width of the rectangular opening portion of the third aperture is changed to a dimension obtained by multiplying the distance between the two parallel sides by the inverse of the reduction rate of a reduction lens system for reducing and projecting the single electron beam on the drawn target substrate, which was formed by passing the electron beam through the first, second and third aperture in turn. Then, the single electron beam is formed into a shape of the figure pattern of the quadrangle by using the rectangular opening portions of the first and second aperture that has been rotated, and by using the rectangular opening portion of the third aperture. Subsequently, the formed single beam is reduced by the reduction lens to be the same size as the figure pattern, and is projected onto the drawn target substrate. Further, the lithography system configured as described above, preferably, further includes a rotary drive mechanism for rotationally driving the third aperture around an optical axis up to an arbitrary angle from 0 to 360°. Also, this lithography system can draw a rotated figure pattern (rotated trapezoidal figure) formed by rotating the figure pattern of the quadrangle described above around the center of the figure thereof by an arbitrary angle. In this case, the lithography system can form the single electron beam into a shape of the rotated figure pattern, by rotating each aperture from the rotary reference by the value which is summed the rotation angle of each aperture when the figure pattern of the quadrangle is drawn, and the same angle as a rotation angle of the rotated figure pattern. According to the present invention described above, even a figure pattern (for example, a trapezoidal figure) including two opposite, oblique sides, each forming a different arbitrary angle relative to the coordinate axis in the XY drawing rectangular coordinate system, can be drawn all together by a single beam that has been formed, without dividing into a plurality of figures. Therefore, a figure pattern including a trapezoidal figure etc. can be accurately drawn, and the total drawing time can be largely shortened. The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention. Now, a description will be provided, using the same symbols with respect to the same functional components in the lithography system (FIG. 2, FIG. 3) described in the related art. A lithography system of this exemplary embodiment uses a VSB system. Referring to FIG. 7, an electron gun 1, an illuminating lens system 2, a first aperture 103, a first forming lens system 4A, a second aperture 104, a second forming lens system 4B, a third aperture 105, a reduction lens system 6, an object lens system 8, and a drawn target substrate (a dry plate or a semiconductor wafer) 10 are provided in this order in the beam emission direction of the electron gun 1. In addition, illuminating lens system 2, first forming lens system 4A, second forming lens system 4B, reduction lens system 6, and object lens system 8 respectively have deflectors 3, 5, 17, and 9 for deflecting a beam. Each of first aperture 103, second aperture 104 and third aperture 105 for forming an electron beam has an opening portion in a plate to shield against an electron beam, respectively. Then, each aperture 103, 104, 105 is adapted to be able to independently rotate in both the counterclockwise and clockwise direction around the center of the aperture opening made coincident with optical central axis 18, i.e. the optical axis of this lithography system (FIG. 8), as a basic axis, within a range from 0 to 360°. As for a mechanism for rotationally driving these apertures 103, 104, 105, for example, a configuration for rotating and controlling a plate, as an aperture rotatably installed within a range from 0 to 360° around the center of the aperture opening as a basic axis, using a motor and a gear may be applied. As shown in FIG. 8, the opening portions 103a, 104a of first and second aperture 103, 104 are square, and shapes of the opening portions are not changed. On the contrary, the opening portion 105a of third aperture 105 is an opening portion in a slit shape, and the width of the slit is adapted to be varied. Specifically, as shown in FIGS. 9 and 10, third aperture 105 has a large, rectangular opening, and a pair of shielding plates 41, 42 is disposed on third aperture 105 so as to cover the rectangular opening. The pair of shielding plates 41, 42 is disposed so that end sides thereof abut on each other, and opening slit 43 is formed by making a gap between the end sides by shifting the plates in the opposite direction in synchronization with each other. For that purpose, each of shielding plates 41, 42 is disposed on third aperture 105 slidably in one direction (the direction shown by the arrow in a dotted line) using ball bearing 44. As for a mechanism for moving each of shielding plates 41, 42 close to, or away from each other in synchronization with each other, for example, there may be applied a configuration for rotating and controlling a pinion gear by a motor, the pinion gear being engaged between rack rails fixed on each of the shielding plates. By moving shielding plates 41, 42 close to, or away from each other in synchronization with each other using such construction, the slit opening width formed between the shielding plates 41, 42 can be varied. In the lithography system of this exemplary embodiment, as shown in FIGS. 7 and 8, an electron beam emitted from the electron gun 1 is passed through three apertures 103, 104, 105 to be formed into the shape of a drawing figure pattern. Then, formed beam 7 is reduced by reduction lens system 6, the deflection angle of the beam is changed by deflector 9 of object lens system 8, and then the beam is converged and projected onto the drawn target substrate 10 such as a semiconductor wafer or a dry plate. According to this system, formed beam 7 can be formed into various figures having an oblique side that forms an arbitrary angle relative to the XY drawing rectangular coordinate system. For example, in drawing a drawing FIG. 20 (trapezoidal pattern) 20 by a single electron beam, as shown in FIG. 11 (d) and that includes two opposite, nonparallel oblique sides having an arbitrary angle and having two sides parallel to each other, and parallel or vertical to the XY drawing rectangular coordinate system, a figure is formed as following: First, based on angle data (tilt angle R1) of an oblique side shown on the right side of the target drawing FIG. 20 relative to the XY drawing rectangular coordinate system, first aperture 103 is rotated counterclockwise by tilt angle R1 (FIG. 11 (a)). On the other hand, based on angle data (tilt angle R2) of an oblique side shown on the left side of drawing FIG. 20 relative to the XY drawing rectangular coordinate system, second aperture 104 is rotated clockwise by tilt angle R2. In addition, a rotary reference position for each of apertures 103, 104 is a position at which each side of the square, opening portions 103a, 104a becomes parallel or vertical to the XY drawing rectangular coordinate system. Next, an electron beam which passes through opening portion 103a of first aperture 103 to be projected onto second aperture 104 is shifted in the X and/or Y-direction relative to the XY drawing rectangular coordinate system using deflector 5 of forming lens system 4. Accordingly, a common opening portion between the two apertures 103, 104 forms beam shape 19a having two oblique sides that are inclined at an arbitrary angle and are nonparallel to each other (FIG. 11 (b)). Further, an electron beam formed into beam shape 19b by passing through second aperture 104 is formed by opening portion 105a in the slit shape of third aperture 105. Accordingly, there is provided beam shape 19b having, in addition to the two nonparallel, oblique sides that are inclined at an arbitrary angle, two sides parallel to each other and parallel or vertical to the XY drawing rectangular coordinate system. At this time, third aperture 105 is not rotated and remains at the rotary reference position, and shielding plates 41, 42 are moved in the opposite direction by d/2, forming a slit having an opening width of d. At the rotary reference position of third aperture 105, the long side of the slit is parallel to the X-axis direction in the XY drawing rectangular coordinate system. Subsequently, rectangular beam 7 which passed through third aperture 105 is reduced by the reduction lens system 6, and a beam shot of target drawing FIG. 20 is projected onto drawn target substrate 10. In addition, the slit opening width d of third aperture 105 for forming beam shape 19b is set to a dimension obtained by multiplying the distance between two sides parallel to each other, and parallel or vertical to the XY drawing rectangular coordinate system in target drawing FIG. 20, by the inverse of the reduction rate (fixed value) of reduction lens system 6. That is, beam shape 19b is formed so as to approximate the shape of target drawing FIG. 20 by using a scale multiplied by the inverse of the reduction rate (fixed value). Further, based on figure data of target drawing FIG. 20, to obtain beam shape 19b described above, the deflection position of a beam projected onto second aperture 104 or third aperture 105 is also determined. On the other hand, in drawing drawing figure 22 (FIG. 12 (d)) obtained by rotating drawing figure 20 shown in FIG. 11 (d) around the center of the figure thereof clockwise by an arbitrary angle (R3=R4=R5) as shown in FIG. 12 (d), the figure is formed as follows. First, first aperture 103 is rotated clockwise by an angle (R1+R3) (FIG. 12 (a)), second aperture 104 is rotated clockwise by angle (R2+R4) (FIG. 12 (b)), and third aperture 105 is rotated clockwise by angle R5 (FIG. 12 (c)). That is, by a value obtained by respectively adding the same value to the rotation angle of each of apertures 103, 104, 105 set when drawing figure 20 shown in FIG. 11 (d) is formed, each of apertures 103, 104, 105 is rotated. Accordingly, as shown in FIG. 12 (c), beam shape 21b formed by rotating beam shape 19b shown in FIG. 11 (c) by arbitrary angle (R3=R4=R5) can be obtained. In addition, in the case of the first drawing of drawing FIG. 22, based on angle data of each side of target drawing FIG. 22 relative to the XY drawing rectangular coordinate system, the rotation angle of each of the apertures 103, 104, 105 may be determined. For example, two sides parallel to each other included in drawing FIG. 22 have an arbitrary angle (R3=R4=R5) relative to the XY drawing rectangular coordinate system. Using the VSB lithography system configured as described above, a drawing figure in a trapezoidal shape having a pair of two opposite, nonparallel, oblique sides with an arbitrary angle, as well as a drawing figure obtained by rotating the trapezoidal drawing figure around the center thereof by an arbitrary angle can be drawn all together by a single beam, without the need to divide a drawing region into a plurality of drawing figures as conventionally (FIG. 5 (b), FIG. 6 (b)). Further, specifically, in a conventional VSB lithography system, when drawing figures 23, 25 shown in FIG. 13 (a), FIG. 14 (a) are drawn, it is necessary to divide a drawing region including an oblique line portion as shown in FIG. 5 (b), FIG. 6 (b) into an elongated, rectangular figure horizontal or vertical relative to the XY drawing rectangular coordinate system, to form a single beam for each of divided figures to draw them in turn. On the contrary, in the VSB lithography system according to the present invention, a single beam can be, as shown in FIG. 13 (b), FIG. 14 (b), formed into the same shape 24, 26 as drawing figures 23, 25, therefore the drawing figures can be drawn all together by the single beam. Such a large decrease in the number of divided drawing figures can contribute to a significant reduction in the total drawing time. In the manufacturing field of a photo-mask having an LSI pattern whose shape has increased in complexity, this allows for a dramatic reduction in manufacturing cost of a photo-mask. Of course, this may be expected to be highly effective for improving the productivity of MEMS or a mold for nanoimprinting of optical elements that is required to form a complex pattern using many oblique sides that have an arbitrary angle. In addition, obviously, the VSB lithography system of the present exemplary embodiment can draw a trapezoid or a rotated trapezoidal figure at a time which were not drawn at once by a conventional system, as well as a figure pattern such as a square, a parallelogram and a triangle by controlling the rotation angle of the first to third aperture or the slit width of the third aperture. Further, the exemplary embodiment described above will be described in detail. In the VSB lithography system according to the present invention, for processing data of a drawing figure pattern having an oblique line that is inclined at an arbitrary angle, the drawing figure pattern is divided into a plurality of figures by using a maximum beam size allowed to be formed, which is a minimum unit. Among the divided figures, a figure having an oblique line that is inclined at an arbitrary angle is drawn at once by forming a single beam into a shape of the figure using three apertures 103, 104, 105 configured as described above. As a general rule, the maximum beam size allowed to be formed is the upper limit of the single beam, and only drawing data whose size is not smaller than this is divided into a figure as large as possible within the maximum beam size. At this time, if a portion having an oblique side that is inclined at an arbitrary angle is present, the portion is divided into either a triangle, a parallelogram, or a trapezoid including the oblique side that is inclined at an arbitrary angle. In this case, there is no condition in which one side or two sides constituting each of the divided figures are parallel or vertical relative to the X and/or Y-axis in the XY drawing rectangular coordinate system. The lithography system according to the present invention creates data of a drawing figure to be drawn at once, using a figure division/data generation algorithm described above and a software program coding the algorithm. Then, a single beam is formed based on the drawing figure data, and a beam that has been subsequently formed is converged and projected onto a dry plate (blank) or a wafer. In addition, a specific configuration for once drawing a drawing figure pattern having an oblique side that is inclined at an arbitrary angle in the XY drawing rectangular coordinate system by a single beam is as described with reference to FIG. 7 to FIG. 12. Next, an exemplary embodiment of division of a drawing figure pattern in the lithography system of the present invention will be described. FIG. 15 illustrates an example of an LSI wiring pattern having an oblique line that is inclined at an arbitrary angle. When the LSI wiring pattern as shown is drawn by an electron beam, in a conventional VSB lithography system, all pattern portions having an oblique side that is inclined at an arbitrary angle are finely divided into a plurality of rectangular figures 27 as shown in FIG. 15 (a), thereby an oblique side portion of the pattern portion is approximated by using fine step portions formed of the plurality of rectangular figures 27. Then, the pattern portion is drawn in turn by forming a single beam for each of the rectangular figures 27. On the contrary, in the VSB lithography system according to the present invention, a pattern portion having an oblique side that is inclined at an arbitrary angle, as it is, is divided as oblique line FIG. 28 composed of four sides including an oblique line portion, as shown in FIG. 15 (b). Then, divided figures generated by such data processing are respectively drawn at once by a single beam. Therefore, the drawing time of the LSI wiring pattern can be significantly shortened. Further, FIG. 16 illustrates a silicon micro ring pattern. When the silicon micro ring as shown or a silicon wire of a photonic network system is drawn by a beam, in a conventional VSB lithography system, the ring pattern, as shown in FIG. 16 (a), is divided into a plurality of elongated, rectangular figures 45 horizontal to the X-axis in the XY drawing rectangular coordinate system, and each of the divided rectangular figures 45 is drawn. On the contrary, in the lithography system according to the present invention, an angle 46-1c is, as shown in FIG. 17, smaller than 180°, which is made between two tangents 46-3c, 46-5c touching the outer peripheral circle of the ring pattern at points of tangency 46-2c, 46-4c. Moreover, the two points of tangency 46-2c, 46-4c are selected so as to define a threshold for meeting a desired approximate accuracy and an angle which can equally divide the circumference by the distance between the points of tangency 46-2c, 46-4c. Then, the ring pattern is approximated by an aggregate of a trapezoidal FIG. 46-6c defined by four apexes at which two straight lines connecting the two selected points of tangency 46-2c, 46-4c with the center of the outer peripheral circle intersect with the outer peripheral line and an inner peripheral line of the ring pattern. Subsequently, a single beam is formed into the same shape as trapezoidal FIG. 46-6c, and a single beam 46 subsequently formed is rotated by a varied angle, respectively, and is drawn in turn, as shown in FIG. 16 (b). Using the lithography system of the present invention as shown in FIG. 16 (b), the total number of the divided figures of a pattern can be smaller and the approximate accuracy in the circumference portion can be better, compared to the case of the divided drawing figures shown in FIG. 16 (a). Next, industrial applicability will be described. In the field of LSI design, as fine wiring processing technology improves, it is believed that transistor technology will advance. Concerning a memory device, a reduction in size of a device chip leads directly to a decrease in unit cost of a chip. Therefore, LSI design effective for the reduction in size of a chip will becomes increasingly important in the future. To achieve an effective LSI design, a design method is newly studied by which a pattern is positioned in the oblique direction that is inclined at an arbitrary angle, as opposed to a conventional design method by which a pattern is positioned in the horizontal or vertical direction in the XY drawing rectangular coordinate system. In this design method, a figure having an oblique line that is inclined at an arbitrary angle relative to the XY drawing rectangular coordinate system is used. Therefore, when an LSI pattern having such figure is drawn on a photo-mask, by using the VSB lithography system according to the present invention, device makers can be provided with a high-quality and low-cost photo-mask. Further, an LSI pattern is conventionally an aggregate of a square and a rectangle, but on the contrary, in a pattern drawing for a photo-mask used in a lithography process for MEMS or a mold for nanoimprinting, or in a pattern drawing directly on a wafer used in maskless lithography, an unusual figure having an oblique side, a circle and an arc is used. The present invention is a technology suitable for drawing such figure, therefore also in the industrial field described above, the present invention can be widely used as means for efficient manufacturing technology. While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.
	summary
	summary
	claims	1. A method for fabricating a compound zone plate comprising:fabricating a first zone plate by depositing zones on sidewalk of a first patterned resist template using a conformal thin film coating process;fabricating a second zone plate by depositing zones on sidewalls of a second patterned resist template using a conformal thin film coating process, wherein the second patterned resist template provides complementary zone placement relative to the zones of the first zone plate; andstacking the first zone plate on the second zone plate to form a compound zone plate and aligning the first zone plate with the second zone late so that the zones of the first zone plate are interlaced with the zones of the second zone plate, wherein the resist templates have been retained in the stacked first zone plate and second zone plate. 2. A method as claimed in claim 1, wherein thefirst zone plate has an initial pitch frequency andwhen the zone plates are mechanically stacked together to form the compound zone plate, the compound zone plate has a pitch frequency that is greater than the initial pitch frequency. 3. The method as claimed in claim 1, wherein the compound zone plate has a mark-to-space ratio of 1:1 in the outermost zones, and the first and second zone plates have a mark-to-space ratio of 1:2n+1, wherein n is an integer equal to 1 or higher. 4. The method as claimed in claim 1, wherein zones of the first and second zone plates include Gold. 5. The method as claimed in claim 1, wherein zones of the first and second zone plates include Platinum. 6. The method as claimed in claim 1, wherein zones of the first and second zone plates include Tungsten. 7. The method as claimed in claim 1, wherein zones of the first and second zone plates include Iridium. 8. The method as claimed in claim 1, further including a third zone plate mechanically stacked with the first and second zone plates. 9. The method as claimed in claim 8, further including a fourth zone plate mechanically stacked with the first, second, and third zone plates. 10. The method as claimed in claim 1, wherein the compound zone plate has a mark-to-space ratio of 1:1 in the outermost zones. 11. The method as claimed in claim 1, wherein fabricating the first zone plate and the second zone plate comprises using atomic layer deposition to deposit Gold zones. 12. The method as claimed in claim 1, wherein fabricating the first zone plate and the second zone plate comprises using atomic layer deposition to deposit Platinum zones. 13. The method as claimed in claim 1, wherein fabricating the first zone plate and the second zone plate comprises using atomic layer deposition to deposit Tungsten zones. 14. The method as claimed in claim 1, wherein fabricating the first zone plate and the second zone plate comprises using atomic layer deposition to deposit Iridium zones. 15. The method as claimed in claim 1, further comprising:fabricating a third zone plate using atomic layer deposition to deposit zones on sidewalk of a third patterned resist template; andstacking the third zone plate with the first zone plate and the second zone plate to form the compound zone plate. 16. The method as claimed in claim 15, further comprising:fabricating a fourth zone plate using atomic layer deposition to deposit zones on sidewalls of a fourth patterned resist template; andstacking the fourth zone plate with the first zone plate, the second zone plate, and the third zone plate to form the compound zone plate.
	claims	1. A method of processing projection data that has been taken by a system, the system comprising a pixel array having a plurality of pixels and a radiation source that emits cone-beam radiation toward the pixel array, the method comprising:acquiring a set of radiographic projections of an object that has been taken by the system with a portion of the plurality of pixels being obscured from the cone-beam radiation, each radiographic projection having a plurality of pixel values corresponding to the plurality of pixels of the pixel array, each pixel value being representative of an amount of radiation received by its corresponding pixel for the projection;acquiring an indication of which pixels have been obscured; andgenerating estimates of scattered radiation from the pixel values of the obscured pixels. 2. The method of claim 1 wherein acquiring the set of radiographic projections of the object comprises receiving the set of radiographic projections. 3. The method of claim 1 wherein acquiring the set of radiographic projections of the object comprises obtaining the set of radiographic projections from a cone-beam CT system. 4. The method of claim 1 wherein acquiring an indication of which pixels have been obscured comprises receiving the indication. 5. The method of claim 1 wherein acquiring an indication of which pixels have been obscured comprises analyzing the pixel values to determine which pixels have been obscured. 6. The method of claim 1 wherein generating estimates of scattered radiation from the pixel values of the obscured pixels comprises generating an interpolation profile that spans at least some of the unobscured pixels of the set of radiographic projections. 7. The method of claim 1 wherein generating estimates of scattered radiation from the pixel values of the obscured pixels comprises generating two or more averages of pixel values of two or more groups of obscured pixels, and generating an interpolation profile from the two or more averages that spans at least some of the unobscured pixels of the projections. 8. The method of claim 1 further comprising generating a plurality of corrected projections from the set of radiographic projections and the estimates of the scattered radiation. 9. A computer-program product that directs a data processor to process projection data that has been taken by a system, the system comprising a pixel array having a plurality of pixels and a radiation source that emits cone-beam radiation toward the pixel array, the computer-program product comprising:a non-transitory computer-readable medium;a first set of instructions embodied on the computer-readable medium that directs a data processor to acquire a first set of radiographic projections of an object with a portion of the plurality of pixels being obscured from the cone-beam radiation, each radiographic projection having a plurality of pixel values corresponding to the plurality of pixels of the pixel array, each pixel value being representative of an amount of radiation received by its corresponding pixel for the projection;a second set of instructions embodied on the computer-readable medium that directs the data processor to acquire an indication of which pixels have been obscured in at least the first set of radiographic projections; anda third set of instructions embodied on the computer-readable medium that directs the data processor to generate estimates of scattered radiation from the pixel values of the obscured pixels. 10. The computer-program product of claim 9 wherein the first set of instructions directs the data processor to obtain the first set of radiographic projections from a computer-readable medium. 11. The computer-program product of claim 9 wherein the first set of instructions directs the data processor to obtain the first set of radiographic projections from a cone-beam CT system. 12. The computer-program product of claim 9 wherein the second set of instructions directs the data processor to receive the indication of which pixels have been obscured comprises receiving the indication. 13. The computer-program product of claim 9 wherein the second set of instructions directs the data processor to analyze the pixel values to generate the indication of which pixels have been obscured. 14. The computer-program product of claim 13 wherein the second set of instructions directs the data processor to generate a histogram of the pixel values. 15. The computer-program product of claim 13 wherein the second set of instructions directs the data processor to convolve the pixel values of one of the radiographic projections of the first set of radiographic projections with a derivative operator. 16. The computer-program product of claim 9 wherein the third set of instructions directs the data processor to generate an interpolation profile that spans at least some of the unobscured pixels of the projections. 17. The computer-program product of claim 9 wherein the third set of instructions directs the data processor to generate two or more averages of pixel values of two or more groups of obscured pixels, and to generate an interpolation profile from the two or more averages that spans at least some of the unobscured pixels of the projections. 18. The computer-program product of claim 9 further comprising a fifth set of instructions that directs the data processor to generate a plurality of corrected projections from the first set of radiographic projections and the estimates of the scattered radiation.
058833943	abstract	A radiation shield, and a radiation shield assembly. The shield assembly is designed to allow use of conveniently fabricated radiation shield portions to provide a single completed radiation shield. The shield portions are mechanically fastened together, preferably with deck screws. A completed radiation shield assembly is coated with a flexible elastomeric epoxy coating to protect the radiation shielding material, preferably lead, from becoming dislodged. Preferably, the radiation shield is provided in a sequence of layers, with each layer having one or more radiation shield portions. In an alternate embodiment a lightweight, portable radiation shield is provided which has an inner layer with at least one sheet of solid radiation shielding material, an outer stainless steel casing, and a sealant located between at least portions of the at least one sheet of solid radiation shielding material and the outer stainless steel casing. Flanges on the stainless steel casing are fastened together, preferably by riveting to seal the casing. A stainless steel U-shaped cap is provided at the top of the shield for extra protection during use. The sealant and the stainless steel casing, including the cap, cooperate to effectively seal the solid radiation shielding material against leakage outward through the outer stainless steel casing.
056384149	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the following, description will be given of an embodiment of the present invention in connection with the drawings. FIG. 1 represents the structure of a fuel assembly for a basic type fast reactor. FIG. 1 (a) is a general bird's-eye view of a fuel assembly, FIG. 1 (b) shows the fuel assembly, and FIG. 1 (c) is a cross-sectional view of the fuel assembly. In these figures, reference numeral (1) represents a fuel assembly, (11) represents a handling head, (12) an upper spacer pad, (13) an intermediate spacer pad, (14) a wrapper tube, (15) a wire spacer, (16) a lower spacer pad, (17) an entrance nozzle, (2) a fuel element, (21) an upper end plug, (22) a cladding tube, (23) a gas plenum, (24) an upper blanket fuel pellet, (25) a core fuel pellet, (26) a lower blanket fuel pellet, and (27) a lower end plug. In the fuel assembly (1), wrapping wires in spiral shape wound on fuel element (2) that closely fitted adjacent fuel elements are not brought into contact with each other. The upper end of the fuel assembly is the handling head (11) for suspending the fuel assembly. Each of the upper spacer pad (12), the intermediate spacer pad (13), and the lower spacer pad (16) is designed larger than that of the wrapper tube to prevent the wrapper tubes from being in contact with each other in the reactor. On the lower portion of the fuel assembly the entrance nozzle (17) is provided for the liquid sodium coolant. In the fuel element the upper blanket fuel pellet (24), the core fuel pellet (25) and the lower blanket fuel pellet (26) fill the cladding tube (22) as shown in FIG. 1 (b). The gas plenum (23) for accommodating the released fission products is provided above the upper blanket fuel pellet (24). Upper and lower ends are closed with the end plugs (21) and (27), and ends of the wire spacer (15) are welded to these end plugs. In general, fission products are accumulated in a burnt fuel element and most of them are radioactive substances, mainly radiating gamma rays. These radioactive substances collect in the gas plenum (23) as fissioned gas. This F.P gas can be utilized as a nuclide, which offers information on failure of the fuel element. Specifically, when the fuel element fails the F.P gas accumulated in the gas plenum (23) is released. As a result, the failed fuel element has a lower radiation intensity than a normal fuel element. In particular, such a difference in the radiation intensity becomes extremely marked at the gas plenum where the F.P gas is accumulated. Accordingly, it is possible to identify the failure by determining major nuclides in the F.P gas in the gas plenum, i.e. krypton (Kr), xenon (Xe) or iodine (I). The present invention is based on these findings. By obtaining a tomographic image of intensity distribution of the radiation emitted from the nuclides, using the ECT method, it is possible to identify the position of a failed fuel element, which may be present in the fuel assembly, and to display it on a cross-section of the fuel assembly. Unlike the methods used in the past, the failure can be detected quickly, accurately and economically without disassembling the fuel assembly. FIG. 2 shows a method for the identification of failed fuel elements according to the present invention. FIG. 3 represents a general configuration of a detecting system, and FIG. 4 represents positions of failed fuel elements detected by the method of the present invention. Explaining the arrangement of the detecting system referring to FIG. 3, a fuel assembly (1) is supported on a base (6) and is movable in the vertical direction and is also rotatable. A radiation detector 3 is provided which moves along a rail on a mobile base (4) and detects radiation from the fuel assembly (1). The radiation detector is driven and controlled by an ECT processing and drive control system (7) at a position shielded by a radiation shielding member (8). Thus, a CT image can be obtained. In FIG. 2, the fuel assembly (1) is moved in the vertical direction, and the gas plenum is set, for example, to a position where radiation can be detected by the radiation detector. The radiation detector (3) scans, with a predetermined spacing, a plane perpendicular to the axial direction of the fuel assembly, and radiation from a given direction is detected by a collimator (32) via a slit (31). The fuel assembly is rotated by one turn around the axis with given angular movements for each translated position of the radiation detector. Based on the radiation intensity data thus obtained, a tomographic image of radiation intensity distribution is obtained by means of the ECT processing and drive control system (7). Although the fuel assembly is rotated in the above, it is needless to say that the radiation detecter may be rotated instead. In FIG. 4 (a), there are four failed fuel elements marked with black circles in a fuel assembly. Some radiation from the gas plenum is from an activated nuclide in the 316 stainless steel used as the material for the wrapper tube and the fuel element. In the tomographic image of total radiation, only the outline of the fuel element from which the F.P gas has been released is displayed. In contrast, in a tomographic image using the F.P gas nuclide, only the information on the position of the gas plenum is given. Thus, radiation intensity is lower in the portion of the fuel element, from which F.P gas has been discharged, and the portion of the fuel element is displayed as an empty space as shown in FIG. 4 (c). As shown in FIGS. 4 (b) or (c), it is possible according to the present invention to use either of the tomographic images. As explained above, the high intensity fission products of the spent fuel element itself are used as the radiation source in the present invention, and the position of the radiation source is defined within the fuel element. As a result, the failed fuel element can be detected efficiently and accurately using emission computer tomography. This makes it possible to overcome inefficiency in the conventional method for identifying the failed fuel element in a fuel assembly, to provide timely action for operation and control of reactor core and to improve efficiency in nuclear reactor operation.
	claims	1. A charged particle beam apparatus comprising a detector that detects a charged particle released from a sample that is irradiated by a charged particle beam, and a vacuum chamber that surrounds the sample that was irradiated by the charged particle beam,wherein a lubricant that underwent heat purification at a temperature greater than or equal to 80° C. and less than 220° C. inside a vacuum is coated on a sliding part of a sliding member disposed inside the vacuum chamber. 2. The charged particle beam apparatus according to claim 1, wherein the lubricant includes a fluorochemical compound. 3. The charged particle beam apparatus according to claim 2, wherein the fluorochemical compound includes perfluoropolyether. 4. The charged particle beam apparatus according to claim 2, wherein the lubricant is a substance from which a part of CF3, C2F5, and/or C3F7 was removed by the heat purification. 5. The charged particle beam apparatus according to claim 1, wherein the lubricant includes a hydrocarbon compound. 6. The charged particle beam apparatus according to claim 1, wherein a kinetic viscosity of the lubricant is 400 to 700 mm2/s. 7. A charged particle beam apparatus comprising a detector that detects a charged particle released from a sample that is irradiated by a charged particle beam, and a vacuum chamber that surrounds the sample that was irradiated by the charged particle beam,wherein a lubricant including perfluoropolyether is coated on a sliding part of a sliding member disposed inside the vacuum chamber and the lubricant has a kinetic viscosity of 400 to 700 mm2/s and is a substance that is obtained after undergoing a process that removes a part of CF3, C2F5, and/or C3F7. 8. The charged particle beam apparatus according to claim 7, wherein the part of CF3, C2F5, and/or C3F7 is removed by heat purification at a temperature greater than or equal to 80° C. and less than 220° C. inside a vacuum.
	description	The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory. The present invention relates to spectroscopy, and more particularly to spectroscopy materials, systems and methods. Radioactive materials are often detected and identified by measuring gamma-rays and/or neutrons emitted from the materials. The energy of gamma-rays is specific to that particular material and acts as a “finger print” to identify the material. Similarly, neutron energy is particular to the material, and may be used to identify the material. Of very high value are detectors capable of identifying the distinctive time-correlated signatures corresponding to neutrons and gamma rays, or “gammas” emitted by fissioning material from within a background of uncorrelated natural radiation. A detector capable of distinguishing neutrons from gammas, as well as offering a fast response time typically has better capability for detecting the distinctive time-correlated events indicative of the presence of fissioning nuclei. The ability to detect gamma rays and/or neutrons is a vital tool for many areas of research. Gamma-ray/neutron detectors allow scientists to study celestial phenomena and diagnose medical diseases, and they have been used to determine the yield in an underground nuclear test. Today, these detectors are important tools for homeland security, helping the nation confront new security challenges. The nuclear non-proliferation mission requires detectors capable of identifying diversion of or smuggling of nuclear materials. Government agencies need detectors for scenarios in which a terrorist might use radioactive materials to fashion a destructive device targeted against civilians, structures, or national events. To better detect and prevent nuclear incidents, the Department of Energy (DOE) and the Department of Homeland Security (DHS) are finding projects to develop a suite of detection systems that can search for radioactive sources in different environments. One particularly useful type of radiation detection, pulse shape discrimination (PSD), which is exhibited by some organic scintillators, involves subtle physical phenomena which give rise to the delayed luminescence characteristic of neutrons, providing a means of distinguishing neutrons from the preponderance of prompt luminescence arising from background gamma interactions. The mechanism by which this occurs begins with the excitation process which produces excited singlet (S1) and excited triplet (T1) states nonradiatively relaxes to the configuration, as shown in FIG. 1. In FIG. 1, the basic physical processes leading to the delayed fluorescence characteristic of neutron excitation of organics with phenyl groups is shown. Since the triplet is known to be mobile in some compounds, the energy migrates until the collision of two triplets collide and experience an Auger upconversion process, shown as Equation 1:T1+T1S0+S1 Equation 1 In Equation 1, T1 is a triplet, S0 is the ground state, and S1 is a first excited state. Finally, the delayed singlet emission occurs with a decay rate characteristic of the migration rate and concentration of the triplet population, which is represented as Equation 2:S1→S0+hv Equation 2 In Equation 2, hv is fluorescence, while S0 is the ground state and Sa is a first excited state. The enhanced level of delayed emission for neutrons arises from the short range of the energetic protons produced from neutron collisions (thereby yielding a high concentration of triplets), compared to the longer range of the electrons from the gamma interactions. The resulting higher concentration of triplets from neutrons, compared to gamma interactions, leads to the functionality of PSD. The observation of PSD is believed to be in part related to the benzene ring structure, allowing for the migration of triplet energy. FIG. 2A shows a typical plot of logarithmic population versus linear time (ns) for stilbene. Population is the singlet excited state population, which is proportional to the output of light from a test crystal under examination, in this case a stilbene crystal, after the crystal it is excited by high energy radiation. As can be seen from the plot, some light is produced by the crystal almost immediately, referred to as prompt luminescence, and other light is produced from the crystal over a period of time, referred to as delayed luminescence. Generally, the plot for each type of radiation will have a steep component 202 and a tail component 204, where the differentiation point 206 between the two is defined in the region where the slope of the line changes dramatically. In this example, the steep component 202, tail component 204, and differentiation point 206 for the Neutron curve is labeled. Note that the steep component, tail component, and differentiation point for the Gamma curve is different for stilbene, and other compounds which possess good PSD properties. Compounds which do not possess good PSD properties will generally not have substantial differences in the curves plotted for Gamma and Neutron radiation. The upper line in the plot shown in FIG. 2A is a Neutron-induced scintillation pulse shape, while the lower line is a Gamma-induced scintillation pulse shape. As can be seen, stilbene is able to differentiate between the Neutron and Gamma pulse shapes, and produces noticeably different luminescence decay lineshapes for each radiation type. However, not every compound has this ability to separate between Gamma and Neutron pulse shapes, and therefore compounds which do are very useful for PSD, as Gamma and Neutron luminescence decay plots have different pulse shapes for these compounds. Once the population versus time plot has been determined for each test crystal under examination, if it appears that there is PSD for the crystal type, the area (QS) under the tail component of the curve for each type of radiation is calculated, along with the area (QF) under the entire line for each type of radiation. By dividing the total area (QF) into the tail area (QS), a scatter plot of the ratio of charge versus the pulse height can be produced, as shown in FIG. 2B for stilbene. FIG. 2B shows a plot of the ratio of charge (QS/QF) versus the pulse height, which correlates to an output of a light detector, such as a photomultiplier tube. The x-axis represents the pulse height, which is proportional to the energy of the event. Gamma events correspond to light produced by Compton electrons generated in the detector material. Neutron events correspond to proton recoils in the detector material; lower energy proton recoil events correspond to “glancing angle” interactions between the neutron and proton in the detector material, while a high energy “knock-on” interaction between a neutron and a proton will produce a higher energy event. Referring to FIG. 2B, at hv equal to about 1600V, conventional scintillators utilizing stilbene exhibit a neutron-to-gamma (n°/γ) separation S of about 0.132. The greater the separation S of neutron-to-gamma, the better PSD performance can be expected. It is with these scatter plots that good PSD separation can be determined, which is defined as PSD separation, S, which is the gap between the mean ratio of charge (QS/QF) for Gamma and the mean ratio of charge (QS/QF) for Neutron taken over an extended period of time. The higher this separation, S, is, the better the compound is at PSD separation. It is generally accepted in the prior art that stilbene offers good PSD. However, stilbene, generally grown from melt, is difficult to obtain. Therefore, a number of other organic molecules have been examined. Unfortunately, most research in this area has concluded that many known liquid and solid materials, including many compounds having benzene rings, do not possess PSD properties comparable to single-crystal stilbene. Despite the difficulty in identifying compounds with suitable PSD properties, the inventors previously succeeded in demonstrating several exemplary compounds with suitable PSD properties and capable of being grown from solution, including 1-1-4-4-tetraphenyl-1-3-butadiene; 2-fluorobiphenyl-4-carboxylic acid; 4-biphenylcarboxylic acid; 9-10-diphenylanthracene; 9-phenylanthracene; 1-3-5-triphenylbenzene; m-terphenyl; bis-MSB; p-terphenyl; diphenylacetylene; 2-5-diphenyoxazole; 4-benzylbiphenyl; biphenyl; 4-methoxybiphenyl; n-phenylanthranilic acid; and 1-4-diphenyl-1-3-butadiene. Moreover, crystals such as stilbene, generally grown from melt, are difficult to obtain. Therefore, organic liquid scintillator cocktails comprised of an aromatic solvent, such as toluene, a primary and a secondary fluor, have been developed and are commercially available, however, liquid scintillators do not exhibit PSD properties comparable to single-crystal stilbene, and are also hazardous to field, because these compounds typically include flammable, toxic, and otherwise hazardous materials that limit application to sensitive environments such as aviation, military applications, medical applications, and etc. Moreover, the above crystals, especially when grown from solution, tend to be relatively fragile, making safe and efficient transport difficult. The patent application referenced above and incorporated by reference described organic materials comparable to or better than stilbene in relation to PSD properties for neutron radiation detection, and in a form that is easier to fabricate into large monoliths which are durable, and which do not introduce hazardous material into the radiation detection process. However, the foregoing application, while describing plastic scintillators with pulse shape discrimination (PSD) that allowed for the efficient discrimination of fast neutrons from gamma radiation background, did not specifically disclose simultaneous detection of thermal and fast neutrons discriminated from each other and from the background gamma radiation. In real detection conditions, a fraction of neutrons interacting with hydrogenated materials can lose their energy converting into low-energy (thermal) neutrons. Detection of both types of neutrons in previous solutions required simultaneous use of two different types of scintillators. Particularly, capture nuclei-loaded glass and plastic scintillators not capable of PSD were used for thermal neutron detection, while detection of fast neutrons was made mainly using liquid scintillators with PSD. Even this multiple-scintillator approach is insufficient to satisfy demand, as the present techniques for detection of thermal neutrons are based on 3He detectors, which have a well-known problem of sharply decreasing availability due to the diminishing supply of 3He obtained as a side product of tritium production. Moreover, for many decades, the most commonly used PSD materials have been liquid scintillators and single crystal stilbene, which enabled efficient discrimination between fast neutron and gamma radiation, due to the high content of hydrogen in their composition (FIG. 12B). However, the detrimental attributions of liquid scintillators, such as significant thermal expansion, moderate freezing point, toxicity, and flammability, produce an environmental hazard and serious handling problems in field conditions, while low availability and high cost of single crystals limits the wide-spread use of stilbene in neutron detectors. A scintillator material according to one embodiment includes a polymer matrix; a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount of 3 wt % or more; and at least one component in the polymer matrix, the component being selected from a group consisting of B, Li, Gd, a B-containing compound, a Li-containing compound and a Gd-containing compound, wherein the scintillator material exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays. A method for fabricating the scintillator material in one embodiment includes creating a solid structure comprising the polymer matrix having the primary dye and the component therein. A system according to one embodiment includes a scintillator material as disclosed herein and a photodetector for detecting the response of the material to fast neutron, thermal neutron and gamma ray irradiation. A method for fabricating a scintillator material according to another embodiment includes placing a precursor mixture in a heating vessel; and heating the precursor mixture until a polymerization process is complete, wherein the precursor mixture comprises: a monomer present in an amount ranging from about 60 wt % to about 95 wt %; a primary fluor present in an amount ranging from about 3 wt % to about 40 wt %; an initiator; and at least one component selected from a group consisting of B, Li, Gd, a B-containing compound, a Li-containing compound and a Gd-containing compound Other aspects and embodiments of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention. The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified. The term “about” as used herein refers to ±10% of the denoted value, unless otherwise noted herein. The description herein is presented to enable any person skilled in the art to make and use the invention and is provided in the context of particular applications of the invention and their requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art upon reading the present disclosure, including combining features from various embodiment to create additional and/or alternative embodiments thereof. Moreover, the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Unless otherwise noted herein, all percentage values are to be understood as percentage by weight (wt %). Moreover, all percentages by weight are to be understood as disclosed in an amount relative to the bulk weight of an organic plastic scintillator material, in various approaches. The following description describes several embodiments relating to the use of the fabrication of polymer scintillator materials with distinctively different scintillation pulse shapes resulting from neutron and gamma excitation, respectively. Moreover, various embodiments of the present invention describe the fabrication of polymer scintillator materials capable of simultaneous detection of thermal neutrons and fast neutrons discriminated from the gamma radiation background. Neutron radiation detectors can play a central role in detecting radioactive materials and illicit nuclear weapons, since neutrons are a strong indicator for the presence of fissile materials. Accurate detection of neutrons is required in many areas; examples are nuclear nonproliferation, international safeguards, national security, scientific research, etc. In particular, for nuclear nonproliferation, fast and robust methods for the identification of special nuclear materials (SNM) are needed. According to their energy, neutrons are typically divided in two major groups: thermal (low-energy) neutrons and fast (high-energy) neutrons. Detection of both types requires the separation of the neutron signatures from the always-present strong gamma radiation background. In common radiation detection practice, identification of both thermal and fast neutrons requires simultaneous use of two different types of detectors. Traditionally, gamma excitation in the conventional organic plastic scintillator materials using conventional fluor concentrations in the range of about 0.1-5 wt % fluor have exhibited low excitation density, and weak delayed luminescence. Thus, the ability to distinguish high-energy neutron radiation from gamma radiation has previously been achievable only with liquid scintillators, which are difficult to field, and organic single crystals, which can be fragile and difficult to produce in very large volumes. Accordingly, the inventive approaches detailed in the present disclosures have not been demonstrated in the past, presumably since very few fluors are soluble at >5 wt % in a polymer matrix. Indeed, the traditional polymer scintillator materials have been limited to including fluors in concentrations which demonstrably lack PSD characteristics, discouragingly suggesting that organic plastic polymer materials would be unsuitable for use as a scintillator material capable of exhibiting PSD characteristics. However, the inventors of the presently disclosed scintillator have surprisingly discovered that in some embodiments, loading an organic plastic polymer material with high concentrations of fluors, (≧10 wt %) results in sufficient migration of triplet excitation within the material that the higher excitation density produced by neutron-induced proton recoil results in delayed singlet luminescence from triplet-triplet annihilation. Without wishing to be bound to any particular theory, it is speculated that loading an organic plastic scintillator material with ≧10 wt % of a primary fluor and ≦1 wt % of a secondary fluor with better spectral match to standard photomultipliers may produce an even more effective pulse shape discrimination material. Thus, the use of plastic scintillator material for this application enables passive detection of high-energy neutron radiation as distinguishable from gamma radiation, as well as active interrogation methods, according to various approaches. In particular, recent studies conducted with organic crystals showed that the main reason for the absence of PSD in mixed systems results from the excitation traps formed by a lower-band-gap fluorescent impurity (fluor) present in the host material (solvent) at low concentration. Moreover, increasing the concentration of the fluor can provide conditions suitable for formation of a network for excitation energy migration and triplet annihilation, and may lead to the appearance of PSD comparable to that typical for pure single crystals of the fluor, in various approaches. The present disclosure introduces the results of studies conducted with mixed liquid and plastic scintillating systems. Analysis of the results shows that explanations of the conditions leading to the formation of PSD in crystals and liquids can be similarly applied to the mixed plastic systems. The properties of the exemplary plastics scintillators fabricated with efficient neutron/gamma discrimination are discussed in comparison with commercially available liquid and single crystal organic scintillators. In one general embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount of 3 wt % or more; wherein the scintillator material exhibits an optical response signature for neutrons that is different than an optical response signature for gamma rays. In another general embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount greater than 10 wt %. General Scintillator-Based Radiation Detector System FIG. 3 depicts a simplified spectroscopy system according to one embodiment. The system 300 comprises a scintillator material 302, such as of a type described herein, and which is referred to herein interchangeably as a scintillator. The system 300 also includes a photodetector 304, such as a photomultiplier tube or other device known in the art, which can detect light emitted from the scintillator 302, and detect the response of the material to at least one of neutron and gamma ray irradiation. The scintillator 302 produces light pulses upon occurrence of an event, such as a neutron, a gamma ray, or other radiation engaging the scintillator 302. As the gamma ray, for example, traverses the scintillator 302, photons are released, appearing as light pulses emitted from the scintillator 302. The light pulses are detected by the photodetector 304 and transduced into electrical signals that correspond to the pulses. The type of radiation can then be determined by analyzing the integral of the light pulses and thereby identifying the gamma ray energy absorbed by the scintillator. In some embodiments, the system 300 may be, further comprise, or be coupleable/coupled to, a processing device 306 for processing pulse traces output by the photodetector 304. In other embodiments, the system 300 may include a processing device that receives data from a photodetector that is not permanently coupled to the processing device. Illustrative processing devices include microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), computers, etc. The result of the processing may be output and/or stored. For example, the result may be displayed on a display device 308 in any form, such as in a histogram or derivative thereof. The program environment in which one embodiment of the invention may be executed illustratively incorporates one or more general-purpose computers or special-purpose devices such hand-held computers. Details of such devices (e.g., processor, memory, data storage, input and output devices) are well known and are omitted for the sake of clarity. It should also be understood that the techniques of the present invention might be implemented using a variety of technologies. For example, the methods described herein may be implemented in software miming on a computer system, or implemented in hardware utilizing one or more processors and logic (hardware and/or software) for performing operations of the method, application specific integrated circuits, programmable logic devices such as Field Programmable Gate Arrays (FPGAs), and/or various combinations thereof. In particular, methods described herein may be implemented by a series of computer-executable instructions residing on a storage medium such as a physical (e.g., non-transitory) computer-readable medium. In addition, although specific embodiments of the invention may employ object-oriented software programming concepts, the invention is not so limited and is easily adapted to employ other forms of directing the operation of a computer. Portions of the invention can also be provided in the form of a computer program product comprising a physical computer readable medium having computer code thereon. A computer readable medium can include any physical medium capable of storing computer code thereon for use by a computer, including optical media such as read only and writeable CD and DVD, magnetic memory or medium (e.g., hard disk drive), semiconductor memory (e.g., FLASH memory and other portable memory cards, etc.), etc. Polymer The inventive organic plastic scintillator system as encompassed by the present disclosures may include any suitable polymer as the plastic component. Particularly suitable are rigid, durable, transparent plastics, possessing an aromatic struction having pi-conjugated rings, and capable of supporting high concentrations of primary, secondary, tertiary, and etc. fluors, e.g. with a total concentration in the range of about 3-75 wt % fluor, according to some embodiments. In a preferred embodiment, the organic plastic component may include a polymer comprising polyvinyltoluene (PVT). In other embodiments, similar polymers may be utilized, such as polystyrene (PS), polyvinyl xylene (PVX), polymethyl, 2,4-dimethyl, 2,4,5-trimethyl styrenes, polyvinyl diphenyl, polyvinyl naphthalene, polyvinyl tetrahydronaphthalene polymers, other complex aromatic polymers, and certain non-aromatic polymers capable of solubilizing high fluor concentrations, etc. as would be understood by one having ordinary skill in the art upon reading the present descriptions. As described herein, suitable polymers may be preferably at least 95% light transmissive in a wavelength of interest, e.g. a wavelength emitted by one or more fluors present in the organic plastic scintillator system, in some embodiments. Moreover, the polymer may be provided as a liquid polymer matrix, a non-liquid polymer matrix, a dry powder, etc. as would be understood by one having ordinary skill in the art upon reading the present descriptions. Moreover, in various approaches the polymer matrix may include aromatic functional groups, such as phenyl groups, among others. Fluors Primary fluors suitable for use in the presently disclosed scintillator system include any fluor as known in the art and capable of exhibiting characteristics of pulse-shape discrimination as described herein. Moreover, the primary fluor of the exemplary organic plastic scintillator system is present in high concentration, e.g. about 3-5 wt % or more, in one embodiment. In preferred embodiments, the primary dye may be present in an amount of 20 wt % or more, and in particularly preferred embodiments, the primary dye may be present in an amount ranging from about 20 wt % to about 75 wt % or an amount ranging from about 30 wt % to about 75 wt %. As discussed herein, the concentrations of fluor are described relative to a weight of the bulk scintillator material, in various embodiments. In one particular embodiment, a scintillator system may include a polymer matrix and a primary fluor disposed in the polymer matrix. Moreover, the primary fluor may be a fluorescent dye present in an amount of 3-5 wt % or more, and such fluorescent dye results in the scintillator material exhibiting an optical response signature for neutrons that is different than an optical response signature for gamma rays. Accordingly, where primary fluors are present in high concentration in the exemplary organic plastic scintillator system, a corollary principle is that the solubility of the fluor in the polymer is preferably high. In one embodiment, for example, the polymer may be characterized by having a solubility of about 3-5 wt % or more with respect to a particular fluor. Moreover, in some approaches the primary fluor may include multiple dyes. In further approaches the primary fluor may include multiple fluorescent dyes. Moreover still, a primary fluor may be incorporated into the polymer according to any suitable mechanism. For example, in one embodiment the primary fluor may be suspended in the polymer matrix and dispersed to an approximately uniform distribution. In other embodiments, the primary fluor may be crosslinked to the polymer matrix. FIG. 14 illustrates a simplified representation of one such embodiment in which the primary fluor 1402 may be crosslinked to the polymer matrix 1404. In still other embodiments, the primary fluor may be copolymerized with the polymer matrix, and/or with another component of the polymer matrix, etc. as would be understood by one having ordinary skill in the art upon reading the present descriptions. Of course, other arrangements of fluor and polymer matrix may be utilized without departing from the scope of the present descriptions. The secondary fluor of the exemplary plastic scintillator system is characterized by wavelength-shifting qualities, such that in the presence of another fluor, particularly a primary fluor present in high concentration in a plastic scintillator system, PSD characteristics of the plastic scintillator system with the primary fluor and the secondary fluor in combination are superior to PSD characteristics of a plastic scintillator system having the same primary fluor exclusively present in high concentration, according to one embodiment. Suitable secondary fluors include any fluor characterized by wavelength-shifting as described herein, and several exemplary embodiments may utilize secondary fluors such as diphenyl anthracene (DPA), tetraphenyl butadiene (TPB) 1,1,4,4-tetraphenyl-1,3-butadiene, 1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOP), p-bis(o-methylstyryl)benzene, 1,4-bis-2-(4-methyl-5-phenyloxazolyl)benzene, 2,2′-p-phenylenebis(5-phenoxazole), diphenylstilbene, 1,3,5-triaryl-2-pyrazolines, 4-(n-butylamino)-2-(4-methoxyphenyl)benzo[b]pyrylium perchlorate, sodium salicylate, 1,4-bis(2-methylstyryl)benzene (Bis-MSB), 7-dimethylamino-4-methyl-2-quinoline, 7-amino-4-methylcoumarin, 4,6-dimethyl-7-ethylamino coumarin, etc. as would be understood by one having ordinary skill in the art upon reading the present descriptions. Particularly preferred secondary fluors include DPA, TPB, POPOP, and Bis-MSB according to one embodiment. Regarding the concentration of the secondary fluor, as described herein the exemplary organic plastic scintillator system may include secondary fluor in a low concentration in order to maximize the beneficial wavelength-shifting effects on PSD performance. For example, in one embodiment the secondary fluor may be present in an amount of about 2 wt % or less. As described herein, secondary fluors may be present in an amount described relative to a weight of the bulk scintillator material. Particularly impressive PSD values have surprisingly been obtained with a plastic scintillator embodiment including polyvinyl toluene (PVT) with ˜30% 2,5-diphenyl oxazole (PPO) as primary fluor and 0.5% diphenyl anthracene (DPA), as secondary fluor, according to one embodiment. Particularly surprising is the solubility of PPO in the PVT polymer, which allows for excellent PSD characteristics described herein. One preferred embodiment of a PSD plastic can by formed by combining: 0.1-1% Benzoyl peroxide (initiator), 30% 2,5-diphenyl oxazole (PPO) as primary fluor, 0.2-0.5% diphenyl anthracene (DPA), or tetraphenyl butadiene (TPB) as secondary fluor and balance vinyl toluene. The process of creating the plastic corresponding to this embodiment may include: adding the materials listed above to a container in a glovebox under an N2 atmosphere, such as a wide mouth glass jar in one exemplary embodiment, placing the container in an oven at 80 C, and allowing the jar to sit in the oven undisturbed for four days, after which it is cooled to room temperature in ambient conditions. The resultant polymer is rigid, substantially transparent and offers excellent scintillation properties for pulse shape discrimination. Scintillator Fabrication Various embodiments may employ any known scintillator material without departing from the scope of the present disclosure. However, several preferred approaches for fabricating scintillators with suitable PSD characteristics from organic plastic are described below. In one embodiment, liquid scintillator mixtures were fabricated from anhydrous p-xylene (>99%), 2,5-diphenyloxazole (PPO, 99%), and 9,10-diphenylanthracene (DPA, >98%) in the oxygen-free atmosphere of a nitrogen-filled glovebox. PPO was used as received. DPA was stirred for 0.5 h in warm acetone, collected by filtration, dried, and stored in, nitrogen atmosphere prior to sample preparations. The liquid mixtures of required concentrations were transferred into sealed 50 mm×10 mm cylindrical quartz cuvettes and subsequently used for further measurements. In another approach, plastic scintillator mixtures were fabricated as follows. Vinyl toluene was filtered through a chromatographic support material to remove inhibitor prior to polymerization. Filtered vinyl toluene and an initiator, e.g. benzoyl peroxide, were sparged with nitrogen for 40 minutes and stored in sealed containers in a glovebox refrigerator at −20 C. To conduct polymerization, required amounts of PPO and DPA were weighed in a glovebox into 20 mL scintillation vials, initiator (10-30 mg) and vinyl toluene were then added to make up the final weight proportions of polymer parts. The vials were tightly sealed, removed from the glovebox, and placed in an oven at 80 C. Two hours later they were shaken to ensure complete mixing, and then held at 80 C for a total of 96 hours. After cooling to room temperature the glass was scored and broken with a mallet to remove the bare scintillator part. Of course, the above fabrication methodologies are provided only by way of example, and organic plastic scintillator systems comprising polymers other than PVT and/or fluors other than DPA/PPO may be fabricated under similar conditions, but taking account for slight variations in various approaches, e.g. to temperature, incubation time, amount of respective components, etc. as would be understood by a skilled artisan reading the present descriptions. Furthermore, the present descriptions also encompass methods for fabricating scintillator materials as described herein, as particularly represented by FIG. 11, in various approaches. FIG. 11 depicts a method 1100. As will be appreciated by the skilled artisan reading the present descriptions, the method 1100 may be performed in any environment, including those depicted in FIGS. 1-10, among others. Regardless of environment, the method 1100 is characterized by operation 1102, where a scintillator precursor mixture is placed in a heating vessel, and subsequently heated until a polymerization process has completed in operation 1104. In one embodiment, the scintillator precursor mixture is a combination of about 60-95 wt % of a monomer, about 5-40 wt % of a primary fluor, and about 0.1 wt % of a free radical initiator. Any monomer capable of polymerizing and solvating the primary fluor in an amount ranging from about 5-40 wt % may be employed in the exemplary fabrication process, according to one embodiment and as would be understood by one having ordinary skill in the art upon reading the present descriptions. In one particular embodiment, the fabrication process may include combining about seven grams of vinyl toluene, about 2.94 grams of PPO, and about 0.01 grains of benzoyl peroxide in a heating vessel, mixing the combination, and heating the mixture at about 80° C. for approximately 96 hours. In another embodiment, the fabrication process may include combining about seven grams of vinyl toluene, about 2.94 grams of PPO, about 0.05 grams of DPA, and about 0.01 grams of benzoyl peroxide in a heating vessel, mixing the combination, and heating the mixture at about 80° C. for approximately 96 hours. Notably, the solid structure may include any of the structures described herein, and the primary fluor may include any fluor as described herein, according to some approaches. Experimental Results: Photoluminescence Growth and characterization of mixed single crystals led to an understanding of the mechanisms of excited state migration and interaction, prompting an exploration of compositions of polymer scintillator with sufficient fluor to reach the percolation threshold whereupon triplet excitation is able to migrate and annihilate. Experiments with complex liquid mixtures lead to findings that high loading with fluors helps improve pulse shape discrimination (PSD) in such organic scintillators as well. So far, the polymer scintillators offering PSD exhibit a figure of merit (FOM) for PSD of ˜3, compared to >4 for certain single crystal organics, such as stilbene, etc. This performance metric is already sufficient to distinguish neutrons from gammas down to the few hundred keV/gamma equivalent regime, and will be very useful for non-proliferation, homeland security and safeguards applications. Photoluminescence (PL) spectra were measured under UV excitation using a commercial Spex Fluoromax-2 spectrometer. The scintillation light yield efficiency was evaluated from the position of the Compton edge in the 137Cs spectra, in which 480 keVee (electron-equivalent energy) was defined by 50% of the Compton edge peak. Neutron detection properties of samples were studied using a 252Cf source shielded with 5.1 cm of lead, which reduced the gamma rates to the same order of magnitude as neutrons, to irradiate liquid or plastic samples coupled to Hamamatsu R6231-100-SEL photomultiplier tube (PMT). The signals collected at the PMT anode were recorded using a 14-bit high-resolution waveform CompuScope 14200 digitizer with a sampling rate of 200 MS/s, for offline analysis. The ability of scintillators to discriminate between the neutrons and gamma rays emitted from the 252Cf source was evaluated using the charge integration method. In particular, waveforms were numerically integrated over two time intervals: ΔtTotal and a subinterval ΔtTail, corresponding to the total charge (QTotal) and the delayed component (QTail) of the signal, respectively. The value of the ratio of charge R=QTail/QTotal for the two time intervals indicated whether the considered event was likely produced by a neutron (high R value) or a gamma ray (small R value). Quantitative evaluation of PSD was made using Figures of Merit (FOM) as represented in Equation 3, where S is the separation between gamma and neutron peaks, and δgamma and δneutron are the full width at half maximum (FWHM) of the corresponding peaks, as shown in FIG. 5, according to one embodiment.FOM=S/(δgamma+δneutron) Equation 3 The experimental separation S was calculated as a difference between the mean delayed light fraction, (QTail/QTotal) for neutrons and gammas taken as a normal distribution in PSD over a specified energy range. In total 40000 events were collected for each scintillator sample, with approximately 20% of the statistics used for FOM calculation in the energy range near the Compton edge. A reasonable definition for well separated Gaussian distributions of similar population sizes is shown in Equation 4, below, where σ is the standard deviation for each corresponding peak.σ>3(σgamma+σneutron) Equation 4 Noting that where FWHM 2.36, a reference parameter FOM≧3(σgamma+σneutron)/2.36(σgamma+σneutron) was used to define efficient PSD in the tested samples. The experimentally determined efficiency value was ≈1.27 One characteristic of the exemplary scintillator material described herein is that the system exhibits an optical response signature for neutrons that is different than an optical response signature for gamma rays, according to one embodiment. In particular, the neutron optical response signature may be in the range of about 600-800 keV gamma equivalent, according to one embodiment. FIGS. 4A-4B show examples of PSD patterns measured in some organics with phenyl groups according to several embodiments. FIG. 4A shows a comparison of the charge ratio QO/QF as exhibited by one embodiment of an organic plastic scintillator as described in the present disclosures, and a scintillator utilizing a stilbene crystal. As can be seen from the figure, the inventors have successfully created organic plastic scintillator embodiments that exhibit similar PSD characteristics as single crystal systems employing stilbene as the scintillating material. Accordingly, it is possible to generate a more rigid and durable, scintillator material from organic plastic while retaining the advantageous neutron and gamma radiation separation characteristics of more expensive and fragile alternatives such as liquid and single crystal scintillators. FIG. 4B depicts comparative FOM readings taken from an exemplary organic plastic scintillator exhibiting PSD as described herein and according to one embodiment as compared to a FOM reading of a LLNL Eljen liquid scintillator, according to one embodiment. When comparing FOM readings from FIG. 4B, both of which used test samples of approximately the same volume, a clear improvement in the FOM levels is apparent. Particularly, the FIG. 4B illustrates a FOM reading of 3 taken from a LLNL plastic scintillator, according to one embodiment. This FOM reading shows PSD approaching the level of typical liquid and single crystal organic scintillators, thus improving neutron/gamma discrimination properties of both liquid and plastic scintillators in the embodiments shown, among others within the scope of the present descriptions. The discovery that organic plastic scintillators are suitable alternatives for more dangerous, expensive, burdensome, etc. systems such as single crystal scintillators and liquid scintillators led the inventors to experiment with a variety of polymer and fluor candidates. With reference to FIG. 5, several exemplary embodiments of organic plastic scintillators as described herein are depicted according to FOM performance of various embodiments including different fluor(s) in a range of concentrations, in some approaches. As shown in FIG. 5, the top row of graphs represent measurements that were taken from liquid scintillator systems comprising diphenyl anthracene (DPA) as a fluor. Conversely, the bottom row of graphs represent measurements that were taken from scintillator systems comprising 2,5-diphenyl oxazole (PPO) as a fluor. Each fluor exhibits characteristic FOM as a crystal, shown in FIG. 5 as FOM=4.42 for DPA crystal and FOM=1.76 for PPO crystal powder, respectively. Moreover, as can be seen from FIG. 5, fluor FOM generally decreases as a function of concentration in solution. For example, a solution of about 2.2% DPA yields a FOM value of about 3.79, according to one embodiment, while a solution of about 0.05% DPA exhibits a FOM value of about 1.12, according to another embodiment, and a solution of about 0.01% DPA exhibits a FOM value of about 0.58, according to yet another embodiment. Similarly, liquid solutions of PPO yield FOM values that decrease as a function of PPO concentration. For example, as shown in FIG. 5 a solution of about 37.5% PPO yields a FOM value of approximately 3.26, while a solution of about 0.05% PPO yields a FOM value of about 1.52, and a solution of about 0.01% PPO yields a FOM value of about 0.71, according to several embodiments. Referring now to FIG. 6, a plot comparing integrated gamma/neutron separation for scintillator systems including a plastic scintillator and a primary fluor, a plastic scintillator, a primary fluor and a secondary fluor, an Eljen liquid, and a stilbene crystal is shown, according to various embodiments. Panel A of FIG. 6 depicts PSD characteristics of an organic plastic scintillator system including PPO as a primary fluor, and no secondary fluor. As can be seen from the figure, this system exhibits a FOM value of about 2.82, according to one embodiment. Comparatively, panel B shows a similar system comprising an organic plastic scintillator with a primary fluor including PPO and further including a secondary fluor. As can be seen from FIG. 6, this system exhibits superior FOM values compared to the similar system lacking a secondary fluor, and in one embodiment exhibits a FOM value of approximately 3.31. Further still, Panels C and D of FIG. 6 provide reference points from which to compare the performance of the exemplary organic plastic scintillator systems as described herein against the performance of liquid and single crystal stilbene scintillator systems, respectively. As can be seen from the figure, the liquid scintillator system shown in Panel C exhibits a FOM value of approximately 3.21, while the single crystal stilbene scintillator system shown in Panel D exhibits a FOM value of about 4.70, according to some embodiments. Notably, the exemplary organic plastic scintillator system including PPO as a primary fluor and a secondary fluor outperforms the liquid scintillator system in terms of FOM value, and approximates the performance of the industry-standard single crystal stilbene system. Accordingly, high quality PSD characteristics may be imparted to modern scintillator systems without incorporating expensive, fragile, and/or hazardous materials of the conventional scintillator system. Referring now to FIGS. 7A and 7B, the comparative effects of including multiple fluors in a scintillator crystal are shown, according to one embodiment. As may be seen particularly from FIG. 7A, a plastic scintillator having, e.g. 30% w/v PPO as a primary fluor is capable of neutron detection. Moreover, neutron detection may be improved by incorporating a low concentration of a secondary fluor, where the secondary fluor is characterized by emitting photons of lower energy (longer wavelength) than photons emitted by the primary fluor, according to one embodiment. As shown in FIG. 7B, embodiments of plastic scintillators containing only the primary fluor PPO exhibit an emission spectrum with a major peak near 360 nm. By contrast, embodiments of plastic scintillators containing primary and secondary fluor, such as DPA, exhibit emission spectra characterized by a peak shift to a longer wavelength (lower energy). Moreover, including a secondary fluor also results in greater luminescence than in systems including only a primary fluor, according to one embodiment. Moreover, including high concentrations of primary fluor improves PSD behavior, but at higher concentrations disadvantageous self-absorption of emitted photons traps the light and prevents its emission from the scintillator. In one approach, including a secondary fluor with a lower emission wavelength than the primary fluor shifts the energy of the emitted photon and preventing unfavorable absorption thereof by the primary fluor molecules. Preferably, secondary fluor may be included in such low concentration that self-absorption is negligible, thereby circumventing the disadvantages inherent to high concentrations of a single fluor, according to one embodiment. Referring now to FIG. 8, the dependence of PSD on fluor concentration is shown as measured in one embodiment including PPO as a primary fluor and DPA as a secondary fluor through the entire range of respective solubility in xylene. For both types of solutions, there is a region of very low fluor concentrations (<1 μmole/g solution, or ˜0.02 wt. %) with negligibly small PSD. Increasing the concentration leads to a gradual enhancement of PSD which, despite the large difference in the solubility, surprisingly exhibits a similar slope for both fluors up to a molecular concentration of about 10 μmole/g solution. It is further interesting to note that the separation of the PSD curves unexpectedly occurs at a concentration corresponding to the maximum light yield for both PPO and DPA (˜10 μmole/g), as particularly shown in panel B of FIG. 8, according to one embodiment. This decrease of the scintillation light efficiency at increasing fluor concentration (concentration quenching) is ascribed to the formation of excimers (S0S1). Therefore, the separation of the PSD curves may relate to different kinetics of these processes for different types of the molecules. For example, in one embodiment a rise in PSD to efficient values above a concentration threshold as measured in DPA and PPO solutions is similar to that observed in mixed crystal scintillation systems, which exhibit PSD behavior according to the simple model of energy transfer and triplet-triplet annihilation shown in FIG. 1. Accordingly, at very small concentrations, excited singlet states of the solute molecules still produce scintillation light, while excited triplets behave more like energy traps, since direct fluorescence from the triplets is effectively forbidden. Meanwhile, at relatively large intermolecular distances and low probability of collisions, e.g. in dilute solutions, fluor molecules cannot interact, thus leading to quenched triplet migration, recombination, and a resulting degradation, or even worse, absence of PSD behavior. At the higher concentrations, increased probability of triplet-triplet collisions leads to the enhancement of the delayed light and a rise of the PSD above a certain concentration threshold corresponding to the establishment of a continuous network of interacting fluor molecules. Several exemplary organic plastic scintillators with varied fluor concentration were analyzed, and some results of several exemplary embodiments are shown in FIG. 9. As evidenced by FIG. 9, a general trend is observable wherein quality of separation between neutron radiation signals and gamma radiation signals exhibits improved resolution with increasing primary fluor concentration. For example, as shown in FIG. 9 one embodiment of an organic plastic scintillator system including only 1 wt % PPO as a primary fluor exhibits no resolution of neutron and gamma radiation signals, respectively, and therefore is incapable of discriminating between the two as required for suitable PSD performance. At about 6 wt % PPO, neutron radiation and gamma radiation signals begin to resolve, but still insufficiently to achieve desirable PSD characteristics, according to some embodiments. In some approaches, true separation between neutron radiation and gamma radiation signals can be seen at primary fluor concentrations of about 10 wt %, and improve with increased primary fluor concentration to about 15 wt %, as shown in FIG. 9, according to one embodiment. Moreover, separation continues to improve with increasing primary fluor concentration, and signals are completely distinguishable according to one embodiment including about 30 wt % primary fluor. Of course, further increases in primary fluor concentration may be expected to further increase signal separation and hence PSD performance, but the inventors have observed that primary fluor concentrations above about 75 wt % may exhibit inhibitory effects on signal resolution and PSD performance. Accordingly, primary fluor concentrations in a range of about 10 wt % to about 75 wt % relative to the bulk weight of the scintillator material are preferred, in some approaches. FIG. 10 further depicts the generally observed relationship between fluor concentration and PSD performance with particular reference to fraction of delayed light for both neutron and gamma radiation, according to one embodiment. As can be seen from FIG. 10, organic plastic scintillators as described herein and utilizing PPO as a primary fluor exhibit a direct relationship between PPO concentration and amount of delayed light, whether from gamma or neutron radiation. Accordingly, FOM values and corresponding PSD characteristics also improve with increasing primary fluor concentration, in some embodiments. Accordingly, the fixed position of molecules in a polymer matrix indicate advantageous performance where the concentration of a fluor required for efficient PSD is closer to that in mixed crystals rather than in liquid solutions, in various approaches. Digital Processing for Pulse Shape Discrimination In one digital processing approach, signals corresponding to a subset of the events are selected and processed. Yet another approach includes processing two or more integration windows (e.g., 0-τ1, τ1-τ2), and employing this ratio to deduce a pulse shape discrimination factor, derived from each individual scintillation pulse. In any approach, and particularly approaches utilizing digitization as described herein, the exemplary scintillator system employing an organic plastic polymer may further include additional components. In one embodiment, for example, the exemplary scintillator system may include a processor, e.g. for performing a discrimination method for processing an output of the photodetector using pulse shape discrimination for differentiating responses of the material to the neutron and gamma ray irradiation. In another embodiment, the exemplary scintillator system may additionally and/or alternatively include a photodetector, e.g. for detecting the response of the material to at least one of neutron and gamma ray irradiation. Of course, other components as would be understood by the skilled artisan reading the present descriptions may be included and/or excluded according to various approaches. In various embodiments, digital processing for pulse shape discrimination may be performed substantially as described in U.S. patent application Ser. No. 13/024,066, filed Feb. 9, 2011, which is incorporated in its entirety herein by reference. Thermal and Fast Neutron Discrimination As noted above, various embodiments of the present invention describe polymer scintillator materials capable of simultaneous detection of thermal neutrons and fast neutrons discriminated from the gamma radiation background. Fabrication of such polymer scintillator materials is also discussed. Experiments conducted with organic single crystals showed that addition of a thermal neutron capture component to a scintillator with PSD properties leads to its ability to produce three different shape pulses corresponding to the gamma, fast neutron and thermal neutron radiation (“triple” PSD). Further studies confirmed that similar phenomenon occurs in plastic scintillators capable of PSD. It was surprisingly and unpredictably found that, by following the teachings presented herein, it is now possible to incorporate capture nuclei in PSD plastic scintillators that now can detect and distinguish between thermal neutrons, fast neutrons, and gammas in one piece of material. Several advantages of plastics are that they can be manufactured as homogeneous, and optically transparent or translucent solids of various sizes and shapes that should prove very useful for the wide-spread use in radiation detection. Moreover, plastic scintillators in some embodiments may exhibit color when they are adapted for longer wavelength luminescence. In various embodiments, plastic scintillators with “dual” PSD, such as any of the plastic scintillators described elsewhere herein, are loaded with at least one component selected from a group consisting of Lithium, Boron, Gadolinium, Lithium-containing compounds, Boron-containing compounds, and/or Gadolinium-containing compounds. The signal discrimination between fast neutrons and gamma rays is achieved, in some approaches, by the use of hydrogen-rich aromatic polymer matrices, such as but not limited to polyvinyltoluene (PVT) or polystyrene (PS), loaded with high concentration of scintillation dyes, such as but not limited to 2,5-diphenyloxazole (PPO). The short range of the energetic protons produced from neutron collisions, compared to the longer range of the electrons from the gamma interactions, leads to the higher proportions of the delayed light in the scintillation pulses produced by fast neutrons in comparison with the gamma-induced pulses. Heavier charged particles, such as alphas resulting from the capture reactions with 6Li or 10B produce an even greater fraction of delayed light, giving the basis for thermal neutron discrimination from both fast neutrons and gamma radiation background. Thermal neutron capture on Gd can be identified by detection of a cascade of gamma-rays amounting to total energy of about 8 MeV and/or characteristic capture time distributions (e.g., specific time correlations). To further demonstrate, consider FIGS. 12A-12D, which illustrate different shapes of neutron and gamma scintillation pulses in a PSD scintillator (FIG. 12A) that does not have Li, B or Gd; and in a Lithium-containing PSD scintillator (FIG. 12C), and the corresponding digitally separated signals detected from neutrons and gamma scintillation pulses (FIGS. 12B and 12D, corresponding to FIGS. 12A and 12C, respectively). A preferred way of detecting fast and thermal neutrons utilizes pulse-shape discrimination (PSD) with organic scintillators, which builds on the PSD mechanism for discriminating between fast neutrons and gammas described above. In general, PSD for discriminating between neutrons and gammas is based on the existence of two-decay component fluorescence, in which, in addition to the main component decaying exponentially (prompt fluorescence), there is usually a slower emission that has the same wavelength, but longer decay time (delayed emission). The short range of the energetic protons produced from neutron collisions, compared to the longer range of the electrons from the gamma interactions, leads to the different proportions of the delayed light in the scintillation pulses produced by neutrons and gammas. Heavier charged particles, such as alphas produce an even greater fraction of delayed light. Modern digital techniques enable easy separation of the pulses based on the ratio of charge between the signal integrals collected in the time gates corresponding to the prompt and delayed components of different shape pulses, e.g., as in FIG. 12A. It has recently been demonstrated that detection of fast neutrons can be efficiently achieved with plastic scintillators capable of neutron-ganuna PSD. Plastic scintillators are non-hazardous. They can be easily produced at different sizes and shape, in large volumes at low cost, which make them promising materials for potential replacement of liquid scintillators. When composed of pure, light-weight hydrocarbons, plastic scintillators provide fast neutron-gamma discrimination similar to that illustrated by FIGS. 12A and 12B. However, thermal neutrons have lower energy, and so may not be detectable using the dual PSD plastic scintillators described above. Fortunately, as found in further studies, if certain additional components containing atoms with high thermal neutron cross-section are added to the composition of PSD organic scintillators, they gain the ability to simultaneously detect thermal neutrons and fast neutrons discriminated from each other and from the background gamma radiation. The sensitivity of the new materials to thermal neutrons is based on one or more of the following capture reactions on such nuclei as 10B, 6Li, or Gd:10B+n°=7Li+α+2.79 MeV6Li+n°=3H+α+4.8 MeV157Gd+n°=158Gd+γ+7.87 MeV155Gd+n°=156Gd+γ+8.46 MeV,Note that thermal neutron capture on Gd can be identified by detection of a cascade of gamma-rays amounting to total energy of about 8 MeV, or conversion electrons, mainly about 29 keV, and/or by characteristic capture time distributions. Previous use of capture agents in combination with traditional plastic scintillators without PSD was based on identification of thermal neutrons via analysis of the total scintillation light generated due to the energy deposition by the reaction products and/or by capture time distributions. Absence of discrimination capabilities in such detectors led to ambiguity in detection of neutrons mixed with gamma-ray background. On the contrary, plastic scintillators with efficient PSD, such as those described elsewhere herein, and further loaded with thermal neutron capture components enable clear separation of scintillation pulses produced by thermal neutrons, fast neutrons and gamma rays, e.g., as depicted in FIGS. 12C and 12D. The use of the new materials described herein allows for simultaneous detection of thermal and fast neutrons discriminated from the gamma radiation background across a wider energy range. A unique possibility of wide-energy range neutron detection in one detector unit is to substantially simplify the design and use of radiation detectors, being especially beneficial for the processes requiring time correlated signals, such as, for example, neutron imaging, multiplicity information, or antineutrino detection. Due to the low cost and simplicity in large-scale manufacturing, such neutron detectors in some embodiments can be considered 3He replacement. Of particular importance, many sources of radiation such as uranium and plutonium tend to produce fast neutrons. However, when a hydrogen-containing material such as a plastic is introduced, the hydrogen-containing material tends to slow or “thermalize” the fast neutrons, converting them to thermal neutrons. The present scintillator material enables detection of both fast and thermal neutrons in one device. See, e.g., FIG. 3 and related description, above for an illustrative system which may be used with the scintillator material. Of course, those skilled in the art, upon being apprised of the teachings herein, will appreciate that any type of detection system may be adapted for use with the scintillator material. Moreover, a plastic shielding may be implemented in one embodiment to thermalize some of the incoming fast neutrons. In another approach, a lead-based shield may be implemented to reduce a number of gamma rays encountering the scintillator. In general, the scintillator material may be fabricated as described elsewhere herein, with the exception that one or more components selected from: Li, B, Gd, a Li-containing compound, a B-containing compound, and/or a Gd-containing compound is added to the precursor mixture when forming the plastic scintillator. In another approach, the component may include at least two of B, Li and Gd. The component may be added to the precursor mixture in any way. In one approach, the component is added as a solid or liquid and becomes entrained in the precursor materials via dissolution. For example, the solid may be a powder or dissolvable solid in some approaches. The liquid may be a suspension of the component in a fluid, a liquid-state compound of the component, etc. in various approaches. In another approach, the component is co-polymerized with other components in the precursor mixture to form the final material. One skilled in the art, upon reading the present disclosure, will appreciate that known B-, Li- and/or Gd-containing compounds may be utilized in various approaches to practice the invention without the need to resort to undue experimentation. Nonlimiting examples include B-carborane, organo-lithiums, organo-gadoliniums, etc. Likewise, elemental B, Li and/or Gd can be used in some approaches. The component may be present in the scintillator material in an effective amount, defined as at least an amount that provides a detectable signature resulted from a capture reaction. In general, the amount of the component may be present from about 1/100 wt % (or lower) of the scintillator material up to a saturation amount in the precursor mixture. The resulting scintillator material includes the one or more components, and exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays. Where the scintillator material is based on a mixture that would otherwise provide only dual PSD between fast neutron and gammas in the absence of the component, the otherwise identical scintillator material with the component additionally exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays. Particular benefits associated with plastic scintillator materials incorporating B, according to some embodiments, include the following: Triple Discrimination (fast neutrons, thermal neutrons, gamma-rays) Increased Neutron Efficiency higher cross-sections than 6Li higher solubility in precursor mixture than 6Li Moderate light efficiency for thermal neutron reaction products (e.g., 70 keVee) limits scintillator size Potential for moderate size detectors Particular benefits associated with plastic scintillator materials incorporating Li, according to some embodiments, include the following: Triple Discrimination (fast neutrons, thermal neutrons, gamma-rays) Higher Light Yield (less quenching) High light efficiency for thermal neutron reaction products (e.g., 450 keVee) Potential for large active volume detectors Potential for applications where fast neutrons are considered as background FIG. 13A depicts an experimental pattern having separated signatures of different types of radiation. Separated signatures of different types of radiation make it possible to establish presence of thermal neutrons, fast neutrons, and gamma rays detected in one piece of the new material. FIG. 13B depicts a PSD pattern showing simultaneous detection of mutually discriminated thermal neutrons, fast neutrons, and gammas in the energy range (250-320) keVee obtained with a Boron-loaded PSD plastic. The results shown in FIGS. 13A and 13B were obtained with a plastic scintillator comprised of polyvinyl toluene (PVT) with 28% of 2,5-diphenyloxazole (PPO), as primary fluorophore, 5% of meta-carborane, as thermal neutron capture agent, and 0.2% diphenylanthracene (DPA), as secondary fluorophore. In one illustrative embodiment, which is not meant to be considered limiting in any way, a colorless, optically transparent PSD plastic for simultaneous detection of thermal and fast neutrons can by formed by combining: 0.001-1% Luperox 231 (initiator); 28-30% 2,5-diphenyloxazole (PPO), as primary fluorophore; 0.1-2.0% a longer-wavelength compound, such as 9,10-diphenylanthracene (DPA), or 1,1′,4,4′-tetraphenyl-1,3-butadiene (TPB), as secondary fluorophore; 0.01-10% of any soluble or co-polymerizable component containing 10B, 6Li, or Gd. balance 4-methylstyrene or styrene precursor. The materials are added to scintillation vials or glass jars, degassed prior to entrance into a glovebox under N2 or Ar. Once the monomer of choice is added, the vessel is sealed and then placed in an oven at 50-95° C. under inert gas flow, and allowed to cure for 72-240 hrs., after which it is cooled to room temperature. The resulting polymer is rigid, transparent and offers excellent scintillation properties for pulse shape discrimination. Applications and Uses Embodiments of the present invention may be used in a wide variety of applications, and potentially any application in which high light yield and/or pulse shape discrimination between gammas, fast and thermal neutrons, charged particles, etc. is useful. Illustrative uses of various embodiments of the present invention include, but are not limited to, applications requiring radiation detection. Detection, surveillance and monitoring of radioactive materials, including identification of special nuclear materials (SNM), are a few such examples. Various embodiments can also be used in the nuclear fuel cycle, homeland security applications, nuclear non-proliferation, medical imaging, special nuclear material, high energy physics facilities, etc. Moreover, the figure of merit (FOM) performance metric is already sufficient to distinguish neutrons from gammas down to the few hundred keV/gamma equivalent regime, and will be very useful for non-proliferation, homeland security and safeguards applications. Yet other uses include detectors for use in treaty inspections that can monitor the location of nuclear missile warheads in a nonintrusive manner. Further uses include implementation in detectors on buoys for customs agents at U.S. maritime ports, cargo interrogation systems, and instruments that emergency response personnel can use to detect or search for a clandestine nuclear device. Assessment of radiological dispersal devices is another application. Further applications include radiography, dosimetry, and scientific research. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
	claims	1. A canister for final repository of spent fuel elements from a nuclear reactor comprising:an insert that contains said spent fuel elements;an inner copper casing that encloses said insert; andat least one outer casing that encloses said copper casing and that comprises a passive-film-forming metal or metal alloy, the passive film on the casing comprising an essentially oxidic film that is rich in one or more of the metals in the group of metals consisting of the metals zirconium, chromium and titanium. 2. A canister according to claim 1, wherein said essentially oxidic film essentially consists of one or more oxides of one or more of the metals that contain the group of metals consisting of the metals zirconium, chromium and titanium. 3. A canister according to claim 2, wherein said essentially oxidic film principally consists of one or more oxides of one or more of the metals that contain the group of metals that consist of the metals zirconium, chromium and titanium. 4. A canister according to claim 1, where the outer casing consists of cast, forged and/or rolled elements. 5. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is titanium or a titanium based alloy, which forms a titanium rich oxide, and wherein the outer casing has a material thickness in the range of 4-30 mm. 6. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is titanium or a titanium based alloy, which forms a titanium rich oxide, and wherein the outer casing has a material thickness in the range of 6-20 mm. 7. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is zirconium or a zirconium based alloy, which forms a zirconium rich oxide, and wherein the outer casing has a material thickness in the range of 3-20 mm. 8. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is a cobalt based or nickel based alloy that comprises at least 12% by weight of chromium. 9. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is a cobalt based or nickel based alloy that comprises at least 14% by weight of chromium. 10. A canister according to claim 8, wherein the outer casing has a material thickness in the range of 8-40 mm. 11. A canister according to claim 8, wherein the outer casing has a material thickness in the range of 10-30 mm. 12. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is stainless steel comprising at least 18% by weight of chromium, and wherein the outer casing has a material thickness in the range of 8-50 mm. 13. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is stainless steel comprising at least 18% by weight of chromium, and wherein the outer casing has a material thickness in the range of 10-40 mm. 14. A canister according to claim 12, wherein the stainless steel is an austenitic steel comprising at least 12% by weight of nickel. 15. A canister according to claim 12, wherein the stainless steel is a duplex steel with a nickel content in the range of 1.5-10% by weight of nickel. 16. A canister according to claim 12, wherein the stainless steel is a ferritic steel with a chromium content of at least 22% by weight of chromium. 17. A canister according to claim 12, wherein the passive-film-forming metal is alloyed with tungsten and/or molybdenum such that W+Mo>0.15% by weight. 18. A canister according to claim 1, wherein the inner copper casing has a material thickness of at least 25 mm. 19. A canister according to claim 1, wherein the insert is made of cast iron. 20. A canister according to claim 18, wherein the insert is made of cast iron with a chromium content of more than 13% by weight. 21. A canister according to claim 1, wherein the outer casing constitutes the outermost metal layer. 22. A canister for final repository of spent fuel elements from a nuclear reactor comprising:an insert constructed and arranged for containing spent fuel elements;an inner copper casing enclosing said insert; andat least one outer casing enclosing said copper casing, the outer casing being formed from at least one passive-film-forming metal or metal alloy selected from the group consisting of zirconium, chromium and titanium.
051924960	claims	1. A fuel assembly comprising: a plurality of fuel rods arranged in a square 10.times.10 lattice other than at a central region thereof corresponding to a rectangular space for accommodating an arrangement of 4.times.4 fuel rods; four fuel rods arranged so that a respective one of the four fuel rods is disposed at each of four corner portions of the central region; and water rod means including one of a plurality of water rods and a plurality of spectral shift water rods being disposed in the central region, one of the plurality of water rods and the plurality of spectral shift water rods being arranged adjacent to and spaced form one another along a circular path so as to delimit intervals therebetween in the central region in a space of the central region other than the four corner portions for accommodating 12 fuel rods. 2. A fuel assembly according to claim 1, wherein a plurality of water rods are provided, each of the water rods having a large diameter. 3. A fuel assembly according to claim 1, wherein a plurality of spectral shift water rods are provided, each of the spectral shift water rods having an internal liquid level adjustment by control of coolant flow rate in a reactor core. 4. A fuel assembly according to claim 1, wherein one of the plurality of water rods and the plurality of spectral shift rods are arranged to surround a central portion of the central region and enable formation of a first coolant flow path which communicates with second coolant flow paths formed at fuel rods surrounding the central region. 5. A fuel assembly according to claim 4, wherein the first coolant flow path communicates with the second coolant flow paths through the intervals delimited between the water rod means. 6. A fuel assembly according to claim 1, wherein the plurality of fuel rods arranged in the square lattice includes at least first fuel rods and the four fuel rods arranged at the four corners of the central region are second fuel rods. 7. A fuel assembly according to claim 6, wherein the second fuel rods have a shorter axial length than an axial length of the first fuel rods. 8. A fuel assembly according to claim 2 wherein the plurality of fuel rods arranged in the square lattice includes at least first fuel rods and the four fuel rods arranged at the four corners of the central region are second fuel rods. 9. A fuel assembly according to claim 8, wherein each of the water rods has a large cross-section and a horizontal cross-sectional area corresponding to a cross-sectional area of three first fuel rods, the plurality of water rods including four water rods arranged along the circular path. 10. A fuel assembly according to claim 8, wherein the second fuel rods have a shorter axial length than an axial length of the first fuel rods. 11. A fuel assembly according to claim 8, further comprising an upper tie plate for supporting upper end portions of at least the first fuel rod, the upper tie plate delimiting an opening corresponding to a central portion of the central region delimited by the plurality of water rods arranged along the circular path. 12. A fuel assembly according to claim 8, wherein the fuel rods arranged in the square lattice further include third fuel rods, the third fuel rods having an axial length shorter than an axial length of the first fuel rods and being arranged in the outermost portion of the square 10.times.10 lattice. 13. A fuel assembly according to claim 12, wherein the fuel rods arranged in the square lattice include third fuel rods, the third fuel rods having an axial length longer than an axial length of the second fuel rods.
	summary
	description	This is a Continuation Application of application Ser. No. 13/939,346, filed on Jul. 11, 2013, which is a Continuation Application of application Ser. No. 13/530,192, filed on Jun. 22, 2012, now U.S. Pat. No. 8,537,460, which is a Continuation Application of application Ser. No. 13/118,028, filed on May 27, 2011, now U.S. Pat. No. 8,243,364, which is a Continuation Application of application Ser. No. 12/399,775 filed Mar. 6, 2009, now U.S. Pat. No. 7,952,797, which is a Continuation Application of application Ser. No. 11/216,560 filed Aug. 31, 2005, which is a Continuation-in-Part Application of PCT Application No. PCT/EP2004/002014 filed Mar. 1, 2004 and published as WO 2004/079753 on Sep. 16, 2004, which claims priority from German Application No. 103 09 084.3 filed Mar. 3, 2003. The entire disclosures of the prior applications are hereby incorporated by reference. The invention concerns a reflective optical element for the EUV and soft X-ray wavelength region, having a multilayer system and a protective layer system, wherein the side of the multilayer system facing the protective layer system terminates in an absorber layer. Furthermore, the invention concerns an EUV lithography appliance with a reflective optical element of this kind. Multilayers are composed of periodic repetitions, and in the most simple case a period consists of two layers. The one layer material should consist of a so-called spacer material, while the other layer material should consist of a so-called absorber material. Spacer material has a real part of the refractive index close to 1, absorber material has a real part of the refractive index significantly different from 1. The period thickness and the thicknesses of the individual layers are chosen in dependence on the operating wavelength, so that the reflectivity is generally maximized at this operating wavelength. Depending on the requirement of the reflective optical element in regard to the reflection profile, various configurations of the multilayer system are conceivable. Bandwidth and reflectivity, for example, can be adjusted by having more than just two materials in one period or by deviating from a constant layer thickness or even from constant thickness ratios (so-called depth-graded multilayers). EUV lithography appliances are used in the production of semiconductor components, such as integrated circuits. Lithography appliances which are used in the extreme ultraviolet wavelength region primarily have multilayer systems of molybdenum and silicon, for example, as the optical reflective element. Although EUV lithography appliances have a vacuum or a residual gas atmosphere in their interior, it is not entirely possible to prevent hydrocarbons and/or other carbon compounds from being inside the appliance. These carbon compounds are split apart by the extreme ultraviolet radiation or by secondary electrons; resulting in the depositing of a carbon-containing contamination film on the optical elements. This contamination with carbon compounds leads to substantial reflection losses of the functional optical (surfaces, which can have a considerable influence on the economic effectiveness of the EUV lithography process. This effect is intensified in that typical EUV lithography appliances have eight or more reflective optical elements. Their transmission is proportional to the product of the reflectivities of the individual optical reflective elements. The contamination leads not only to reflectivity losses, but also to imaging errors, which in the worst case make an imaging impossible. Thus, cleaning cycles have to be provided when operating an EUV lithography appliance or when using reflective optical elements. These significantly increase the operating costs. But the cleaning cycles not only increase the down time, but also entail the risk of worsening of the homogeneity of the layer thickness of the reflective optical elements and the risk of increasing the surface relief, which leads to further reflectivity losses. One approach to controlling the contamination for Mo/Si multilayer mirrors is found in M. Malinowski et al., Proceedings of SPIE Vol. 4688 (2002), pages 442 to 453. A multilayer system of 40 pairs of molybdenum and silicon with pair thickness of 7 nm and a Γ=(dMo/(dMo+dSi), with dMo being the thickness of the molybdenum layer and dSi the thickness of the silicon layer, of around 0.4, was provided with an additional silicon layer on the uppermost molybdenum layer. Multilayer systems with different thickness of silicon protective layer were measured, extending from 2 to 7 nm. Traditional Mo/Si multilayer systems have a silicon protective layer of 4.3 nm, which helps protect against contamination, although it very quickly becomes oxidized. The measurements revealed that there is a reflectivity plateau for a silicon protective layer of 3 nm, depending on the radiation dose. It is therefore recommended to use silicon protective layers with a thickness of 3 nm, instead of silicon protective layers with a thickness of 4.3 nm. For a longer operating time can be achieved with a silicon protective layer 3 nm in thickness, for the same tolerance in the reflectivity loss. The problem of the present invention is to provide a reflective optical element for the EUV and soft X-ray wavelength region that has the longest possible lifetime. Furthermore, the problem of the invention is to provide an EUV lithography appliance with the shortest possible down time. The problem is solved by a reflective optical element, as well as an EUV lithography appliance according to the claims. It has been found that reflective optical elements for the EUV and soft X-ray wavelength region with long lifetime are achieved if they are provided with a protective layer system that has one or more layers of materials with a particular refractive index, and in which the overall thickness of the protective layer system is chosen according to particular criteria. The one or more layers of the protective layer system should have a refractive index at operating wavelengths between 12.5 nm and 15 nm whose real part is between 0.90 and 1.03, preferably between 0.95 and 1.02, and whose imaginary part is between 0 and 0.025, especially preferably between 0 and 0.015. Thus, as compared to the layers of the multilayer system situated underneath, the layers of the protective layer system have the optical properties of a spacer or lie between those of a spacer and an absorber. The choice of a material with the smallest, possible imaginary part and a real part as close as possible to 1 results in a plateau-shaped reflectivity curve, depending on the thickness of the protective layer system between two thicknesses d1 and d2. This means that, with these selected materials, the reflective optical element made of a multilayer system and a protective layer system is insensitive to fluctuations in the thickness of the protective layer system in a particular region. According to the invention, the reflective optical element has a protective layer system with a thickness smaller than d2. The reflective optical elements of the invention have the benefit that their relative insensitivity to thickness variations in the protective layer system also translates into an insensitivity to the build-up of a contamination layer. Without substantial change in reflectivity, much thicker carbon layers can be tolerated than with traditional reflective optical elements. This also has a positive impact on the homogeneity of the imaging, since even thickness fluctuations over the entire area are negligible. Basically, for a given operating wavelength, one will select the material, the layer makeup of the protective layer system, and the individual layer thicknesses so that a plateau in the reflectivity is formed between two thicknesses d1 and d2 as a function of the thickness of the protective layer system. The specific thickness of the protective layer system is then advantageously chosen to be as small as possible, but still within the reflectivity plateau. In practice, one must make sure that the minimum layer thickness is always observed for each layer, so that one can produce a closed layer. It has been found that a standing wave field is formed by reflection at the reflective optical element, whose minimum for a protective layer thickness d1 lies in the vacuum at a distance of a fraction of the operating wavelength. Now, if the layer thickness of the protective layer system is increased, the minimum of the standing wave field approaches the surface. Accordingly, the value of the standing wave field at the surface increases until the maximum is also achieved. Thus, the formation of the reflectivity plateau in dependence on the thickness of the protective layer system results because, with increasing layer thickness, the additionally created absorption, i.e., the resulting decrease in reflectivity, is compensated in that reflectivity gains are produced by increasingly constructive interference after a certain layer thickness. As an additional effect, fewer photoelectrons are emitted near the minimum of a standing wave field. Since the photoelectrons also break down the hydrocarbons from the residual gas atmosphere into carbon or carbon-containing particles, this has the result of a noticeably slower build-up of the contamination. A preferred embodiment is therefore characterized in that the thickness d1 of the protective layer system is such that a standing wave formed by reflection at operating wavelength λB has a minimum at a distance from the surface of the reflective optical element of 0.λB, or less. Thus, the minimum lies in the vacuum. With increasing thickness, the surface as it were migrates through the minimum until the thickness d2 is reached. This corresponds to a distance from the surface to the minimum of at most 0.2λB, and the minimum is located inside the reflective optical element. The specification of the essentially constant curve of the reflectivity is to be understood as meaning that all reflectivity fluctuations in a region that does not limit the functional capability of the reflective optical element are considered to be constant. In an especially preferred embodiment, a reflectivity decrease of 1% of the maximum reflectivity in the protective layer thickness region between d1 and d2 is considered harmless and regarded as being a constant reflectivity curve in the context of this invention. It is to be assumed that the reflectivity curve as a function of the protective layer thickness between d1 and d2 goes through at least one inflection point at the protective layer thickness dW. For due to the partial compensation of the reflectivity loss in the protective layer thickness region between d1 and d2, the slope of the reflectivity curve changes in this protective layer thickness region. Advantageously, the particular thickness of the protective layer system is chosen to be ≦dW. This ensures that the thickness of the protective layer corresponds to a reflectivity which lies in the region of constant reflectivity in the sense of this invention. As a result, the reflective optical element becomes insensitive to an increase in the thickness of the protective layer, for example, due to contamination. In an especially preferred embodiment, the thickness of the protective layer system is equal to d1. The advantageous properties of the invented reflective optical element have especially positive impact when they are used in an EUV lithography appliance Especially when several reflective optical elements are connected in succession, the more uniform reflectivity and also more uniform field illumination for lengthy periods of time have especially positive impact. It has been found that even with increasing contamination the wavefront errors in the complex optical systems of EUV lithography appliances can be kept small. A major benefit consists in that fewer cleaning cycles are required for the EUV lithography appliance, thanks to the longer lifetime of the reflective optical elements. This not only reduces the down time, but also the risk of degeneration of the layer homogeneity, greater roughness of the surface, or partial destruction of the uppermost protective layer from too intense cleaning are significantly reduced. In particular, the cleaning processes for the reflective optical elements of the invention can be controlled such that the contamination layer is deliberately not entirely removed,’ but rather a minimal contamination layer always remains on the uppermost layer. This protects the reflective optical element against being destroyed by too intense cleaning. The thickness of the contamination layer can be measured in traditional manner during its build-up or during the cleaning with a suitable in situ monitoring system. It has proven to be especially advantageous for the protective layer system to consist of one or more materials from the group Ce, Be, SiO, SiC, SiO2, Si3N4, C, Y, MoSi2, B, Y2O3, MoS2, B4C, BN, RuxSiy, Zr, Nb, MoC, ZrO2, RuxMoy, RhxMoy, and RhxSiy. The SiO2 should preferably be amorphous or polycrystalline. The best results are achieved with a multilayer system that consists of Mo/Si layers and that ends with the molybdenum layer on the side facing the protective layer system. Depending on the operating wavelength, multilayer system, and requirement for the reflective optical element, it can be advantageous for the protective layer system to consist of precisely two or precisely three layers. In a preferred embodiment, the protective layer system terminates toward the vacuum with a layer of a material for which the build-up of carbon-containing substances is suppressed. It has been found that certain materials have a low affinity for carbon-containing substances, in other words, carbon-containing substances get stuck to them only with a low probability or they have a slight adsorption rate. Thus, for these materials, the build-up of carbon-containing substances is drastically reduced or suppressed. It has been found that such materials can be used as a protective layer for reflective optical elements for the EUV and soft X-ray wavelength region, without showing significant negative effects on the optical behavior of the reflective optical element. Especially preferred as such are the materials ZrO2, Y2O3, and silicon dioxide in various stoichiometric relations. The silicon dioxide can be in the amorphous or polycrystalline, or possibly even the crystalline state. In another preferred embodiment, the protective layer system terminates toward the vacuum with a layer of a material that is inert to energy deposition, that is, to bombardment with EUV protons or to external electric fields. This decreases the probability of spontaneous electron emission, which in turn might split apart the residual gases into reactive cleavage products. Hence, the deposition of contamination on the protective layer system is further reduced. One can influence the inertia to external electromagnetic fields, for example, by giving the surface the lowest possible relief and/or using materials that have a large gap between the valency band and the conduction band. Especially preferred for this are the materials Nb, BN, B4C, Y, amorphous carbon, Si3N4, SiC, as well as silicon dioxide in various stoichiometric relations. The silicon dioxide can be in the amorphous or polycrystalline, or possibly even the crystalline state. FIGS. 6a and 6b show schematically the structure of exemplary embodiments of a reflective optical element 10 for the EUV and soft X-ray wavelength region comprising a multilayer system 12 and a protective layer system 13, 13′ on a substrate 11. The multilayer system 12 is made of spacer layers 14 and absorber layers 15. The multilayer system 12 terminates with an absorber layer 15 on which the protective layer system 13, 13′ is arranged. In exemplary embodiments, the multilayer system 12 consists of silicon layers as spacer layers 14 and of molybdenum layers as absorber layers 15. The protective layer system 13, 13′ has at least one layer of a material with a refractive index whose real part at an operating wavelength between 12.5 nm and 15 nm is between 0.90 and 1.03, preferably between 0.95 and 1.02, and whose imaginary part at an operating wavelength between 12.5 nm and 15 nm is between 0 and 0.025, preferably between 0 and 0.015, so that the reflectivity plotted as a function of the thickness of the protective layer system 13, 13′ at first drops, until a thickness d1 is reached, the reflectivity remains essentially constant between thickness d1 and another thickness, d2, where d2>d1, and the reflectivity further drops for a thickness >d2, and the thickness of the protective layer system 13, 13′ is smaller than d2. The protective layer system 13, 13′ consists of one or more materials from the group Ce, Be, SiO, SiC, SiO2, Si3N4, C, Y, MoSi2, B, Y2O3, MoS2, B4C, BN, RuxSiy, Zr, Nb, MoC, ZrO2, RuxMoy, RhxMoy, or RhxSiy. In exemplary embodiments of the present invention, the protective layer system 13, 13′ consists of two layers 16, 17 (see FIG. 6a) or three layers 16′, 17′, 18 (see FIG. 6b). Advantageously, the protective layer system 13 of the example illustrated in FIG. 6a ends on a side of a vacuum, i.e. terminates with a layer 16 of a material for which the build-up of carbon is suppressed, and the protective layer system 13′ of the example illustrated in FIG. 6b ends toward a side of a vacuum, i.e. terminates with a layer 17′ of a material that is inert to energy deposition. It will be noted that the terminating of the protective layer system 13, 13′ with a layer of a material for which the build-up of carbon is suppressed or with a layer of a material that is inert to energy deposition or with an other kind of layer is independent of the protective layer system consisting of one, two, three or more layers, as well as independent of the features of any other layers present in the protective layer system. On a Mo/Si multilayer system located on a substrate of amorphous silicon dioxide, consisting of 50 pairs of 2.76 nm molybdenum and 4.14 nm amorphous silicon (a-SiO2), a three-layer protective layer system is deposited. The protective layer system borders on the uppermost molybdenum layer of the multilayer system with a Y-layer 1.2 nm thick. On the Y-layer is placed a 1.5 nm Y2O3 layer. At the vacuum side, the protective layer system is closed by a 1 nm thick amorphous silicon dioxide layer. The choice of the materials and their thickness is based on the criteria of the invention. In particular, the materials are also selected so as to suppress carbon build-up (Y2O3, a-SiO2) or to be inert to energy deposition (Y, a-SiO2). Disregarding the interface and surface roughness, one obtains a reflectivity of 70.2% at an operating wavelength of 13.5 nm for an angle of incidence of 0° with the normal to the surface. FIG. 1 shows the reflectivity of the entire reflective optical element under these conditions as a function of the thickness of the protective layer system, but holding constant the thickness of 1.2 nm for Y and 1.5 nm for Y2O3. A distinct reflectivity plateau is formed between a thickness d1=3.7 nm and a thickness d2=6.68 nm of the protective layer system, or an a-SiO2 layer of 1 nm and 2.98 nm. Accordingly, the thickness of the silicon dioxide layer was selected to be 1.0 nm. In FIGS. 2a and 2b, the resulting standing wave field is shown for a protective layer system thickness of 3.7 nm (FIG. 2a) and for a protective layer system thickness of 6.68 nm (FIG. 2b). Segments a-c corresponding to the protective layer system of amorphous SiO2 (a), Y2O3 (b), and Y (c) and segments d, e corresponding to the multilayer system of molybdenum (d) and amorphous silicon (e). As can be clearly seen, with increasing thickness of the protective layer system the surface of the reflective optical element is situated in the vicinity of the minimum of the existing wave field, it migrates through the minimum, so to speak. This would suggest a slight contamination due to secondary electrons. FIG. 3 shows the reflectivity of the reflective optical element with the protective layer system of Y, Y2O3, and a-SiO2 as a function of the built-up contamination layer. If one selects a tolerance range of 1% for the fluctuation in reflectivity, a carbon layer up to 4 nm thick can be tolerated without significant change in reflectivity. The operating time is therefore a multiple higher than for traditional reflective optical elements. In FIGS. 4a and b, these positive results are also shown by means of an EUV lithography appliance with six reflective optical elements (S1-S6) according to the invention as mirrors. The tested mirror construction is shown in FIG. 4a. In FIG. 4b, the wavefront error is shown as a function of the carbon thickness. Although the wavefront varies periodically with the increased carbon thickness, the absolute value of the wavefront error does not exceed a value that would significantly impair the imaging quality of the lithography system for any carbon thickness. Because of the insensitivity of the reflective optical element discussed here with respect to the build-up of a carbon contamination layer, it is possible to only remove the contamination layer down to a layer of 0.5 nm when cleaning the reflective optical element or when cleaning the entire EUV lithography appliance. This will ensure, on the one hand, that the cleaned optical element once again has a long lifetime. But it will also make sure that the risk of degeneration of the layer homogeneity or roughening of the surface or partial destruction of the topmost layer by too intense cleaning is reduced. On a multilayer system of 50 Mo/Si pairs located on an amorphous silicon dioxide substrate, optimized for an operating wavelength of 13.5 nm, a protective layer system of a 2.0 nm thick cerium layer, which adjoins the topmost molybdenum layer of the multilayer system, and a 1.5 nm thick silicon dioxide layer is placed. The minimum of a standing wave produced by reflection on the uncontaminated reflective optical element at operating wavelength λB lies in the vacuum, 0.05λB from its surface. For a maximum reflectivity of 70.9% at an operating wavelength of 13.5 nm and a tolerated reflectivity decrease of 1%, a carbon contamination layer can tolerate a thickness of up to 3.5 nm (see FIG. 5). This reflective optical element as well is suitable for use in an EUV lithography appliance. The above description of the preferred embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various changes and modifications to the structures disclosed. The applicant seeks, therefore, to cover all such changes and modifications as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof.
047553502	summary	BACKGROUND OF THE INVENTION The present invention relates generally to thermionic power conversion systems, and more specifically to modules for a nuclear energy powered thermionic reactor for space-based operation capable of providing large amounts of power in short pulses. In the operation of a thermionic converter, heat energy is converted directly to electrical current by heating a metallic emitter to sufficiently high temperatures so that electrons escape the emitter and flow to a cooler collector. The source of heat energy for conversion to electrical current may be any of several types, including exothermic chemical reactions and the heat of nuclear fission. In order to promote efficient operation of a thermionic system to generate useful amounts of electrical power, the system must not only generate large amounts of heat required for energizing the thermionic components, but must also provide for rejection of waste heat from the cold side of the thermionics. High power thermionic energy systems are proposed as power supplies for space-based beam or kinetic energy weapons. Those devices require substantial power, but only for short bursts. It is seen, therefore, that there is a need for a thermionic power system able to rapidily absorb very large amounts of waste heat during a high output power pulse, and then remove the absorbed waste heat energy to prepare for another pulsed output of power. It is, therefore, a principal object of the present invention to provide an efficient high power thermionic power system particularly adaptable to high powered pulsed operations in space. It is another object of the present invention to provide a nuclear fission powered thermionic system. These and other objects of the present invention are achieved by the following described nuclear energy powered thermionic reactor system. A unique discovery of the present invention is the use of a heat sink material contained within the core of each reactor module to absorb the waste heat of the thermionic conversion process. An advantage of the present invention is that the heat sink material may act as a neutron moderator, thereby reducing the amount of needed nuclear fuel. A further advantage of the present invention is that containing the heat sink material within the reactor core eliminates any need for an intermediate heat exchanger. Yet another advantage of the present invention is that the reactor radiation shield may be used as part of a heat sink for cooling the heat sink material in the reactor core. The reactor, unlike open-cycle turbine generators, emits no effluents, thereby avoiding problems with thrust cancellation, contamination, and so forth. Also unlike open-cycle power supplies, the reactor is completely reusable. Further, the reactor has no moving parts, eliminating any need in a space based system for torque cancellation and reducing or eliminating vibration. SUMMARY OF THE INVENTION The present invention is directed to a thermionic energy conversion system assembly comprising a heat source which surrounds a plurality of emitter electrodes which surround a plurality of corresponding collector electrodes which in turn surround a heat sink. The heat source may be fissionable nuclear fuel. The heat sink may be a container of heat sink material, which may be a lithium salt, such as lithium hydride. The heat sink material may also be a neutron moderator, such as lithium hydride enriched in the Li-7 isotope. The invention additionally includes a heat pipe, enclosed in the heat sink material, for transferring heat out of the heat sink material. The invention further includes a thermionic energy conversion system module comprising a plurality of stacked-in-series thermionic conversion assemblies. The heat sources and the heat sinks may be made continuous from one assembly to another, and a heat pipe enclosed in the heat sink material removes heat from the heat sink material. The invention further includes an array of thermionic energy conversion system modules to form a thermionic nuclear reactor. The invention additionally includes the method of thermionic energy conversion by using a heat sink positioned inside the thermionic converter assembly.
	claims	1. A scattered radiation grid or collimator for absorbing secondary radiation scattered by an object, the scattered radiation grid or collimator comprising:a support; anda plurality of spaced-apart absorbing elements, the plurality of absorbing elements comprising tubes or pins affixed to the support via plug-in or clamping fixtures,wherein the plug-in fixtures or clamping fixtures project outwardly from a plane of the support or are molded into the plane of the support, andwherein the tubular absorbing elements mountedly engage the plug-in fixtures or clamping fixtures via respective interiors of the tubular absorbing elements. 2. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of the absorbing elements comprises an absorbent material. 3. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of the absorbing elements comprises a support element, the support element comprising a radio-transparent material and being coated on at least one side face with a coating of an absorbent material. 4. The scattered radiation grid or collimator of claim 3, wherein the support element comprises a hollow tube coated on an inner and/or outer side face. 5. The scattered radiation grid or collimator of claim 3, wherein each of the tubular absorbing elements has a wall thickness of about 20 μm to about 50 μm. 6. The scattered radiation grid or collimator of claim 1, wherein the tubes have hollow cylindrical or hollow polygonal outer and/or inner cross sections. 7. The scattered radiation grid or collimator of claim 1, wherein the pins have cylindrical or polygonal cross sections. 8. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of absorbing elements has a length of about 1 mm to about 10 mm. 9. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of absorbing elements has a length of about of 2 mm to about 6 mm. 10. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of absorbing elements has a length of about 2 mm to about 3 mm. 11. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of absorbing elements has an outer diameter of about 0.3 mm to about 2 mm. 12. The scattered radiation grid or collimator of claim 1, wherein each of the plurality of absorbing elements has an outer diameter of about 0.5 mm to about 1 mm. 13. The scattered radiation grid or collimator of claim 1, wherein a length of the plug-in fixtures or clamping fixtures is equal to or shorter than a length of the absorbing elements. 14. The scattered radiation grid or collimator of claim 13, wherein the length of the plug-in fixtures or clamping fixtures is not greater than half of the length of the absorbing elements. 15. The scattered radiation grid or collimator of claim 1, wherein the plug-in fixtures or clamping fixtures are disposed such that each of the plurality of the absorbing elements is axially aligned along a rectilinear path passing through a common focus. 16. The scattered radiation grid or collimator of claim 1, wherein the support comprises a plastic material. 17. The scattered radiation grid or collimator of claim 16, wherein the support is produced via stereo-lithography implemented via a prototyping technique. 18. The scattered radiation grid or collimator of claim 1, wherein the plurality of absorbing elements is potted with a radio-transparent potting material. 19. The scattered radiation grid or collimator as defined by claim 1, wherein the absorption elements are prefabricated. 20. The scattered radiation grid or collimator as defined by claim 1, wherein the support is a single element. 21. The scattered radiation grid or collimator as defined by claim 1, wherein the absorption elements are supported by a single support. 22. A method for producing a scattered radiation grid, the method comprising:providing a support;providing plug-in fixtures or clamping fixtures that project outwardly from a plane of the support or are molded into the plane of the support;positioning a plurality of spaced apart absorbing elements on the support via an automatic positioning mechanism, the plurality of absorbing elements comprising tubes or pins;affixing securely the plurality of absorbing elements to the plug-in fixtures or clamping fixtures provided on the support via respective interiors of the absorbing elements. 23. The method as defined by claim 22, wherein the plurality of absorbing elements is securely affixed to the plug-in fixtures or clamping fixtures separately on an individual basis or simultaneously on a subset basis. 24. The method as defined by claim 22, further comprising:embedding the plurality of the absorbing elements in a potting material. 25. A scattered radiation grid or collimator for absorbing secondary radiation scattered by an object, the scattered radiation grid or collimator comprising:a support; anda plurality of spaced-apart absorbing elements, the plurality of absorbing elements comprising tubes or pins affixed to the support via plug-in or clamping fixtures;wherein the absorbing elements are affixed to the support via plug-in or clamping fixtures near only one end of the absorbing elements. 26. A scattered radiation grid or collimator for absorbing secondary radiation scattered by an object, the scattered radiation grid or collimator comprising:a support; anda plurality of spaced-apart absorbing elements, the plurality of absorbing elements comprising tubes or pins affixed to the support via plug-in or clamping fixtures;wherein the absorbing elements are affixed to the support via plug-in or clamping fixtures on an underside of the absorbing elements.
	abstract	A machine monitoring system and method uses a machine monitoring device (MMD) which is connected to the monitored machine. Outputs from the machine are attached to input connectors on the MMD. The MMD receives inputs from the machine via the input connectors and performs desired transformations. Results of the transformations are stored in an on-board database system within the MMD. Reports on machine status, quality, maintenance, production, and performance are generated by consulting the database system. Reports can be generated at fixed intervals or on demand and may be transmitted over a network. A server, such as a web server or the like, resident within the MMD makes reports remotely viewable from client computing devices on the network via web page interfaces or the like and also allows for remote configuration of the MMD via such interfaces. The monitoring device also has output connectors for transmitting MMD output signals, such as digital output signals or the like, that may be used for activating buzzers, lights or email notifications that can be escalated. MMD output signals may also be used for pausing or stopping machines.
	claims	1. A method of reconstructing a tomographic image of a subject imaged with a nuclear imaging detector having a non-parallel hole collimator comprising:acquiring first projection data of a radiation field within the subject at a first view angle of said detector;acquiring second projection data of said radiation field within the subject at a second view angle of said detector different than said first view angle;combining the first and second projection data to form a difference image; anddetermining a location of the radiation field relative to the collimator surface using the difference image based on Point Spread Function (PSF) which is non-stationary and dependent on a location of a gamma event with respect to the collimator surface of the non-parallel hole collimator. 2. The method as recited in claim 1, wherein the non-parallel hole collimator is one of a group consisting of: a multi-focal collimator, a varying-focal length collimator, a fan beam collimator, and an astigmatic collimator. 3. The method as recited in claim 1, wherein the location determined using the difference image is used in a SPECT image reconstruction algorithm. 4. The method as recited in claim 1, wherein the location determined using the difference image is used in a nuclear planar image reconstruction algorithm. 5. The method as recited in claim 1, wherein said detector is swiveled about its central axis at said second view angle prior to acquiring said second projection data. 6. The method as recited in claim 1, wherein said detector at said second view is translated with respect to a center of a gantry on which said detector is mounted prior to acquiring said second projection data. 7. The method as recited in claim 1, wherein said detector at said second view angle is swiveled about its central axis and is translated with respect to a center of a gantry on which said detector is mounted prior to acquiring said second projection data. 8. A system for reconstructing images including:a nuclear imaging detector having a non-parallel hole collimator;a gantry supporting said detector; anda computer for combining two images of a radiation field obtained from said detector at different positions relative to said gantry, to form a difference image, and computing a location of said radiation field using the difference image based on Point Spread Function (PSF) which is non-stationary and dependent on a location of a gamma event with respect to a collimator surface of the non-parallel hole collimator. 9. The system as recited in claim 8, wherein the non-parallel hole collimator is one of a group consisting of a multi-focal collimator, a varying-focal length collimator, a fan beam collimator, and an astigmatic collimator. 10. The system as recited in claim 8, wherein said computed location is used in an image reconstruction algorithm. 11. A computer program embodied as computer-executable instructions stored on a computer-readable medium, the program comprising instructions for:combining at least two nuclear images of a radiation field within an imaging subject acquired by a nuclear detector having a non-parallel hole collimator, taken from different locations relative to said non-parallel hole collimator, to form a difference image; andcalculating a location of the radiation field relative to the surface of the non-parallel hole collimator using the difference image based on Point Spread Function (PSF) which is non-stationary and dependent on a location of a gamma event with respect to the surface of the non-parallel hole collimator. 12. The computer program as recited in claim 11, wherein said location is calculated using a chi-squared algorithm. 13. The computer program as recited in claim 11, wherein the program further comprises determining the distance between the radiation field and a surface of the collimator. 14. The computer program as recited in claim 11, wherein the program further comprises instructions to reconstruct a SPECT image. 15. The computer program as recited in claim 11, wherein the program further comprises instructions to reconstruct a nuclear planar image. 16. A method of estimating depth information of a radiation event from different planar images acquired using a detector having a non-parallel hole collimator, comprisingobtaining a difference image between said different planar images; andestimating depth information based on Point Spread Function (PSF) which is non-stationary and dependent on a location of a gamma event with respect to a collimator surface of the non-parallel hole collimator. 17. The method as recited in claim 16, wherein the non-parallel hole collimator is one of a group consisting of: a multi-focal collimator, a varying-focal length collimator, a fan beam collimator, and an astigmatic collimator.
	summary
051704188	summary	FIELD OF THE INVENTION AND RELATED ART This invention relates to an X-ray exposure apparatus and, more particularly, to an X-ray exposure apparatus for executing exposure by using synchrotron orbital radiation light (hereinafter "SOR light"). In another aspect, the invention is concerned with a semiconductor processing method which uses such an X-ray exposure apparatus. An X-ray exposure apparatus for executing exposure by using SOR light includes a synchrotron radiation device for producing the SOR light. The synchrotron radiation device is maintained in an ultra high vacuum, and an exposure chamber for accommodating a mask or a wafer is coupled to the synchrotron radiation device by means of a beam line. In an X-ray exposure apparatus of such a structure, there is a possibility that if leakage occurs in the beam line or the exposure chamber an atmospheric gas enters the synchrotron radiation device. In an attempt to avoid this, an arrangement such as shown in FIG. 5 has been proposed (Japanese Laid-Open Patent Application No. Sho 64-61700). SOR light 501 produced by a synchrotron radiation device (not shown) goes along a beam line 503 and through a window material 507, provided on the beam line 503, and irradiates a mask 512 and a wafer 511 placed in an exposure chamber 503. The beam line is equipped with a shock wave delay tube 502, for retarding advancement of shock waves resulting from vacuum leakage, and a mirror chamber 505 for expanding the SOR light 501, disposed in this order. Provided between the mirror chamber 505 and the window material 507 is a pressure sensor 506, and provided between the synchrotron radiation device and the delay tube 504 is an emergency cutoff valve 502 which is operable in response to the detection by the pressure sensor 506. The mask 515 and the wafer 511 accommodated in the exposure chamber 513 can be replaced by any one of masks 515 accommodated in a mask pre-chamber 516 and any one of wafers 511 accommodated in a wafer pre-chamber 509, respectively, with the cooperation of gate valves 514 and 510, respectively. If the window material 507 is broken as a result of leakage in the beam line 503 or in the exposure chamber 513, in response the pressure detected by the pressure sensor 512 increases and the emergency cutoff valve 502 closes to block entry of atmospheric gas into the synchrotron radiation source device. SUMMARY OF THE INVENTION In the X-ray exposure apparatus of the type described above, the pressure sensor for detecting abnormal pressure is provided at a side (upstream side) of the window material closer to the synchrotron radiation device. If, therefore, the leakage occurs in the exposure chamber, the sensor does not directly detects the leakage but it detects the same after the window material breaks. If the window material breaks, the fractions thereof scatter into the exposure chamber and the beam line. This necessitates complicated operations for recovery as well as a long time until the exposure operation starts again. It is accordingly an object of the present invention to provide an X-ray exposure apparatus by which, in an occasion where leakage occurs in an exposure chamber, protection of a synchrotron radiation device can be done without breakage of a window material. In accordance with an aspect of the present invention, there is provided an X-ray exposure apparatus, comprising: an exposure chamber to be coupled with a synchrotron radiation device through a beam line for receiving synchrotron radiation applied through a window material provided on the beam line to execute an exposure process in said exposure chamber; pressure detecting means for detecting pressure in said exposure chamber; a cutoff valve provided in a portion of the beam line between the window material and the synchrotron radiation device; a bypass having a communication valve for communicating a portion of the beam line between the window material and said cutoff valve with a portion between the window material and said exposure chamber; vacuum evacuating means for vacuum evacuating a portion of the beam line between the window material and said cutoff valve; a pump valve provided in a conduit for coupling the beam line with said vacuum evacuating means; and a controller responsive to a pressure detected by said pressure detecting means, wherein, when in the exposure operation the detected pressure represents a steady state lower than a predetermined pressure, said controller operates to open said cutoff valve and said pump valve and to close said communication valve, and wherein, when in the exposure operation the detected pressure is higher than the predetermined pressure, said controller operates to close said cutoff valve and said pump valve and thereafter to open said communication valve. A second cutoff valve may be provided in a portion of the beam line between the window material and the exposure chamber, the opening and closing being controlled in a similar way as the cutoff valve provided in a portion of the beam line between the window material and the synchrotron radiation device. The structure may be modified so that it includes only a cutoff valve in a portion of the beam line between the window material and the exposure chamber as well as the controller. If leakage occurs in the exposure chamber during the exposure operation and the detected pressure increases beyond the predetermined pressure, the cutoff valve and the pump valves are closed and, thereafter, the communication valve is opened. Since the cutoff valve is closed before the communication valve is opened, there is no possibility of entry of a gas in the exposure chamber into the synchrotron radiation device. The opening of the communication valve is effective to avoid application of a pressure to the window material and, as a result, the window material is not damaged. A vacuum pump is provided to vacuum evacuate a predetermined portion of the beam line. When the exposure operation is to be re-started, the communication valve is closed and, thereafter, the pump valve is opened so as to vacuum evacuate any gas in the exposure chamber having been entered into between the window material and the cutoff valve. After this, the cutoff valve is opened. Thus, similarly to the moment as the cutoff valve is closed, it is possible to prevent entry of the gas in the exposure chamber into the synchrotron radiation device. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
	description	This application claims priority from Korean Patent Application No. 10-2009-0036611, filed on Apr. 27, 2009, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 1. Technical Field The present disclosure relates to an apparatus and system for separating remaining powder of hulls, and more particularly, to an apparatus and system for separating remaining powder of hulls, which may collect remaining powder remaining on hulls of a spent nuclear fuel that is separated into the hulls and pellet powder by a high-temperature oxidation process. 2. Related Art A nuclear fuel may designate substances by which available energy is obtained such that the nuclear fuel is charged into a nuclear reactor to create a nuclear fission chain reaction, and a spent nuclear fuel may designate remaining substances after creating the nuclear fission chain reaction. There are two management methods for the spent nuclear fuel as follows. One is a method in which the spent nuclear fuel is embedded below a rock bed of an underground having a depth of 500 m or more to thereby completely isolate the spent nuclear fuel from a human ecology, which is referred to as ‘permanent disposal’. The other is a method in which recyclable substances are separated from a spent nuclear fuel, so that nuclear fuel substances are re-used and high radioactive wastes are permanently disposed. In these conventional methods, spent nuclear fuels having been ignited in a nuclear power plant may be deposited and stored in a water tank in a state where a supplementary treatment for the ignited spent nuclear fuels is no longer carried out, however, an amount of spent nuclear fuel rods may be gradually accumulated with an increase in a period during which a nuclear power is operated, and thus a huge storage space may be required. Also, needs and risks in managing and processing accumulated nuclear wastes may arise. Accordingly, a development in management technologies for recycle of the spent nuclear fuel having a solid type may be urgently required. In this regard, a partial process apparatus for powdering/oxidizing the spent nuclear fuel and transmitting the oxidized nuclear fuel to subsequent processes has been developed. There is a need for separating and recovering remaining powder remaining on hulls even after the spent nuclear fuel is separated into the hulls and pellet powder by a high oxidation process. An aspect of the present disclosure provides an apparatus and system of separating remaining powder of hulls, which may separate remaining powder from hulls obtained by a high-temperature oxidation process. Another aspect of the present disclosure also provides an apparatus and system of separating remaining powder of hulls, which may separate remaining powder from the hulls in several times, thereby increasing a degree of recovery of the remaining powder. Still another aspect of the present disclosure also provides an apparatus and system of separating remaining powder of hulls, which may respectively receive hulls and the remaining powder being automatically separated. According to an aspect of the present disclosure, there is provided an apparatus of separating remaining powder of hulls, including: a first remaining powder separating unit, a hull alignment unit, a second remaining powder separating unit, and a third remaining powder separating unit. In this instance, the apparatus may further include a hull receiving unit to receive the hulls transported from the third remaining powder separating unit, and a remaining powder receiving unit to receive the separated remaining powder from the hulls. Also, the remaining powder receiving unit may be positioned in a lower portion of the second remaining powder separating unit or of the third remaining powder receiving unit. Also, the first remaining powder separating unit may be supplied with hulls of a spent nuclear fuel subjected to a high-temperature oxidation, and may include a first brush for separating remaining powder adhered on an outer peripheral surface of the hulls. Also, the first remaining powder separating unit may include a charging port where the hulls are charged, the charging port being formed in an upper portion of the first remaining powder separating unit, and a discharging port where the hulls are discharged, the discharging port being formed in a lower portion of the first remaining powder separating unit, and the discharging port being selectively opened and closed. Also, the hull alignment unit may be a parts feeder for aligning the hulls by using vibration. Also, a second remaining powder separating unit may be supplied with the aligned hulls from the hull alignment unit, and may include a second brush for separating remaining powder adhered on an inner peripheral surface of the hulls. Also, the second remaining powder separating unit may include a clamp for fixing the hulls, and two second brushes may be inserted into each of the hulls to separate the remaining powder. Also, a third remaining powder separating unit may be supplied with the hulls from the second remaining powder separating unit, and may separate the remaining powder remaining on the inner/outer peripheral surface of the hulls by using air. Also, the apparatus may further include a counting unit to determine a quantity of hulls. In this instance, the counting unit may be an optical sensor positioned on a movement path of the hulls. According to an aspect of the present disclosure, there is provided a system of separating remaining powder of hulls, the system including: an oxidation unit to powder and separate a pellet of hulls of a spent nuclear fuel subjected to a high-temperature oxidation; a first remaining powder separating unit to be supplied with the hulls separated in the oxidation unit, and to include a first brush for separating remaining powder adhered on an outer peripheral surface of the hulls; a hull alignment unit to be supplied with the hulls from the first remaining powder separating unit, and to align the hulls; a second remaining powder separating unit to be supplied with the aligned hulls from the hull alignment unit, and to include a second brush for separating remaining powder adhered on an inner peripheral surface of the hulls; a third remaining powder separating unit to be supplied with the hulls from the second remaining powder separating unit, to separate the remaining powder remaining on the inner/outer peripheral surface of the hulls using air; a hull receiving unit to receive the hulls transported from the third remaining powder separating unit; a remaining powder receiving unit to receive the remaining powder separated from the hulls; and a high-temperature vacuum heating unit to be supplied with at least one of the pellet separated in the oxidation unit or the remaining powder received in the remaining powder receiving unit, and to heat the pellet or the remaining powder in a high temperature vacuum. Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. Although a few exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. FIG. 1 illustrates a configuration of an apparatus 100 of separating remaining powder of a hull (H) according to embodiment of the present disclosure, FIG. 2 illustrates a configuration of a hull alignment unit of the apparatus 100 of FIG. 1, FIG. 3 illustrates a configuration of a second remaining powder separating unit, a third remaining powder separating unit, and a receiving unit of the apparatus 100 of FIG. 1, and FIG. 4 is a diagram used for describing a hull and remaining powder are separately received in the receiving unit of FIG. 3. Referring to FIG. 1, the apparatus 100 includes a drum 110 of a first remaining powder separating unit, a parts feeder 120 of a hull alignment unit, a second remaining powder separating unit 130, an air shower 140 of a third remaining powder separating unit, and a receiving unit 150. The drum 110 may be a cylindrically-shaped hollow vessel. The drum 110 may include a charging port 112 formed in an upper portion thereof. Hulls (H) being cut by a predetermined length may be charged into the charging port 112. In this instance, the charging port 112 may include a cap formed thereon. The cap may be opened when the hulls (H) are charged into the charging port 112, and may be closed when injection of the hulls (H) into the charging port 112 is completed. The drum 110 may include a brush shaft 116 formed in both ends of the drum 110 in such a manner as to be rotated. In this instance, the brush shaft 116 may be extended to outside the drum 110. The brush shaft 116 may include a power transfer means, such as a belt or a pulley, formed on both end portions thereof. The power transfer means may be connected with a driving motor 118. Accordingly, a rotation power transferred from the driving motor 118 may be transmitted to the brush shaft 116 via the power transfer means to thereby enable the brush shaft 116 to be rotated. The drum 110 may include a first brush (not illustrated) formed therein. The first brush may be attached on the brush shaft 116 to thereby be rotated inside the drum 110 when the brush shaft 116 is rotated. When the hulls (H) are charged into the drum 110, and the brush shaft 116 is rotated, the hulls (H) may be rotated together with the first brush. The first brush mounted in the drum 110 may separate remaining powder adhered to an outer peripheral surface of the hull (H). The drum 110 may include a discharging port 114 formed in a lower portion thereof. The hulls (H) with the separation of the remaining powder adhered to the outer peripheral surface of the hull (H) completed in the drum 110 may be discharged through the discharging port 114. The discharging port 114 may be a knife gate valve that is selectively opened/closed to discharge the hulls (H). That is, when the separation of the remaining powder adhered on the outer peripheral surface of the hull (H) is completed in the drum 110, the knife gate valve of the discharging port 114 may be opened to discharge the hulls (H), and when the hulls (H) are completely discharged out from the drum 110 by their gravity, the knife gate value may be closed. Referring to FIGS. 1 and 2, the parts feeder 120 of the hull alignment unit may be provided below the discharging port 114. The parts feeder 120 may align the hulls (H) supplied from the drum 110, using a vibration, so that the hulls (H) are aligned in a certain direction and position. The hulls (H) provided to a center portion of the parts feeder 120 may be moved to a rim portion of the parts feeder 120 in a state where the hulls are aligned in the certain direction and position by the vibration. The hulls (H) moved to the rim portion of the parts feeder 120 may be transported to a transportation path 122 formed in an end of the parts feeder 120. In this instance, the hulls (H) transported to the transportation path 122 may be aligned to be readily transported to the second remaining powder separating unit 130. The transportation path 120 may serve as a path where the hulls (H) aligned in the parts feeder 120 are transported to the second remaining powder separating unit 130, and may transport the hulls (H) in one direction using a conveyor, inclination, or vibration. Referring to FIGS. 1 and 3, the second remaining powder separating unit 130 connected with the transportation path 122 may include a clamp (not illustrated) for holding the provided hulls (H) and a second brush (not illustrated) for separating remaining powder adhered on an inner peripheral surface of the hull (H). The hulls (H) transported to the second remaining powder separating unit 130 may be fixed by the clamp, and two second brushes may be inserted into the hull (H) to secondly separate the remaining powder adhered on the inner peripheral surface of the hull (H). The air shower 140 of the third remaining powder separating unit may be connected with the second remaining powder separating unit 130. The air shower 140 may be externally connected with an air spraying unit (not illustrated) for spraying air to separate the remaining powder of the hull (H). That is, when the remaining powder adhered on the inner peripheral surface of the hull (H) is completely separated by means of the second brush of the second remaining powder separating unit 130, and the hulls (H) are transported forward, air may be sprayed to the inner/outer peripheral surface of the hull (H) using the air shower 140 to thereby thirdly separate remaining powder remaining on the inner/outer peripheral surface of the hull (H). The apparatus 100 may include a counting unit to determine a quantity of the hulls (H). As the counting unit, an optical sensor 160 may be used, and the optical sensor may be positioned on a movement path of the hulls (H). According to the present exemplary embodiment, the optical sensor 160 may be disposed between the parts feeder 120 and the second remaining powder separating unit 130 to thereby determine the quantity of the transported hulls (H). When the above described remaining powder separation process being separated into the hulls (H) and the remaining powder (P) is completed, the separated hulls (H) and the remaining powder (P) may be separately received in the receiving unit 150. The receiving unit 150 may be positioned under the second remaining powder separating unit 130 and the air shower 140. The receiving unit 150 may include a hull receiving unit 152, a remaining powder receiving unit 154, a mesh 156, and a guidance vessel 158. The guidance vessel 158 may be a funnel-shaped vessel disposed under the second remaining powder separating unit 130 and the air shower 140. The separated hulls (H) and the remaining powder (P) may be fed to an upper portion of the guidance vessel 158, and may be collected in a lower portion of the guidance vessel 158 by a shape of the guidance vessel 158. The mesh 156 may be provided in the guidance vessel 158, and disposed to be obliquely inclined in a direction from the parts feeder 120 toward the hull receiving unit 152. The remaining powder (P) may be received in the remaining powder receiving unit 154 passing through the mesh 156, and the hulls (H) may be guided and received in the hull receiving unit 152. As illustrated in FIG. 4, the remaining powder receiving unit 154 may be disposed under the guidance vessel 158. The remaining powder receiving unit 154 may be detachably mounted to a lower portion of the guidance vessel 158. Accordingly, a cover of the remaining powder receiving unit 154 may be closed when the reception of the remaining powder (P) is completed, and then the received remaining powder (P) may be readily moved to a place where a subsequent process is performed. The hull receiving unit 152 may be disposed in a side of the guidance vessel 158. An end of the hull receiving unit 152 may be connected with the side of the guidance vessel 158 in a position of being adjacent to an end of the mesh 156. The hull receiving unit 152 may be detachably coupled to the guidance vessel 158. Accordingly, a cover of the hull receiving unit 152 may be closed when the reception of the hulls (P) is completed, and then the received hulls (H) may be readily moved to a place where a subsequent process is performed. A process of separating the hulls (H) and the remaining powder (P) using the apparatus 100 will be herein described in detail. First, hulls (H) from which powder is separated by performing a high temperature oxidation process on a spent nuclear fuel may be provided. In this instance, the hulls (H) may be desirably provided to be cut by a predetermined length. More desirably, a length of the hull (H) may be about 5 cm. Next, the charging port 112 of the drum 110 may be opened, the hulls (H) may be charged into the charging port 112, and then the charging port 112 may be closed. In this instance, the discharging port 114 formed in the lower portion of the drum 110 may be maintained in a state of being closed. Next, the first brush and the hulls (H) may be rotated together by the driving motor 118. The remaining powder (P) adhered on the outer peripheral surface of the hull (H) may be separated using the first brush formed inside the drum 110. When the separation of the remaining powder (P) adhered on the outer peripheral surface of the hull (H) is completed, the discharging port 114 may be opened. When a transportation of the hulls (H) to the part feeder 120 is completed, the discharging port 114 may be closed. Next, the hulls (H) supplied to the parts feeder 120 may be transported to the second remaining powder separating unit 130 while being aligned by vibration. Next, in the second remaining powder separating unit 130, the hulls (H) may be fixed by the clamp, and two second brushes may be inserted into the hull (H) through both ends of the hull (H) to thereby second separate remaining powder (P) adhered on an inner peripheral surface of the hull (H). The hulls (H) in which second separation is completed may be moved forward, and remaining powder (P) remaining on the inner/outer peripheral surface of the hull (H) may be third separated from the hull (H) using the air shower 140. Next, the separated remaining powder (P) may be downwardly dropped to be guided to the guidance vessel 158, and may be received in the remaining powder receiving unit 154 passing through the mesh 156 mounted in the guidance vessel 158. The separated hulls (H) may be downwardly dropped to the guided to the guidance vessel 158, and may be received in the hull receiving unit 152 along the mesh 156. Next, when the separation of the hulls (H) and the remaining powder (P) is completed, the separated hulls (H) and remaining powder (P) may be respectively moved to a place where a corresponding subsequent process is performed. A system of separating remaining powder of a hull according to an exemplary embodiment may include an oxidation unit, a first remaining powder separating unit, a hull alignment unit, a second remaining powder separating unit, a third remaining powder separating unit, a hull receiving unit, a remaining powder receiving unit, and a high-temperature vacuum heating unit. Configurations of the first remaining powder separating unit, the hull alignment unit, the second remaining powder separating unit, the third remaining powder separating unit, the hull receiving unit, and the remaining powder receiving unit of the system may be similar to those of the drum 110, the parts feeder 120, the second remaining powder separating unit 130, and the air shower 140, and the hull receiving unit 152, and the remaining powder receiving unit 154 of the apparatus 100, and thus descriptions thereof will be omitted. The oxidation unit may be supplied with a spent nuclear fuel being cut by a predetermined length, and the spent nuclear fuel may be heated at a high-temperature and in a vacuum state using an oxidant and a ceramic ball, and thereby the spent nuclear fuel may be separated into pellet powder and hulls. The separated pellet powder and hulls may be selectively discharged, and the hulls may be transported to the first remaining powder separating unit to separate remaining powder from the hulls. The hulls and the remaining powder may be separated while passing through the first remaining powder separating unit, the hull alignment unit, the second remaining powder separating unit, the third remaining powder separating unit, the hull receiving unit, and the remaining powder receiving unit, and volatile toxic substances within remaining powder received in the remaining powder receiving unit may be removed by the high-temperature vacuum heating unit. The high-temperature vacuum heating unit may be supplied with at least one of the pellet separated in the oxidation unit and the remaining powder received in the remaining powder receiving unit, and may heat the pellet or the remaining powder in a high temperature vacuum. Since the volatile toxic substances within the remaining powder heated in the high temperature vacuum in the high-temperature vacuum are removed, treatments for the remaining powder in a subsequent process may be simplified. As described above, according to the apparatus and the system of separating the remaining powder of the hull, it may be possible to automatically separate remaining powder remaining on the hulls. In particular, the remaining powder remaining on the inner/outer peripheral surface of the hull may be separated from the hull three times, thereby completely separating the remaining powder from the hull. Also, the remaining powder and the hulls separated by the apparatus and the system may be automatically received in the respective receiving unit, thereby reducing supplementary costs created due to a subsequent process. Although a few exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.
	abstract	Methods and systems for controlling critical dimension (CD) in a process system, including computing an exposure dose error based on at least one output of the process system, normalizing the computed exposure dose error based on a target exposure dose, and providing an exposure dose to the process system based on at least one normalized exposure dose error. The target exposure dose can be associated with a process system characteristic(s) and can be updated based on normalized computed exposure dose errors.
043303706	abstract	A combination seal and bearing arrangement for use in a nuclear reactor including a vessel and vessel cover is disclosed herein. The vessel cover itself includes at least one rotatable plug which serves to perform certain position related functions within the reactor vessel and the combination seal and bearing arrangement is provided for sealing the annular opening around the rotation plug while, at the same time, providing a bearing support for the latter.
059784326	summary	This invention is directed to high-density dispersion fuel having spherical particles solidified rapidly by an atomization process. It more particularly refers to a novel method of making dispersion fuel. BACKGROUND OF THE INVENTION Conventionally powder for dispersion nuclear fuel is produced by alloying and comminution. Alloying metals are alloyed into ingots by induction or arc heating in a vacuum atmosphere. The as-cast ingots are heat-treated in a vacuum for 100 hours at 900.degree. C. to ensure compositional homogeneity, and then quenched to form a meta-stable gamma phase. The ingots are machined into chips and milled under liquid argon using a hardened steel mill to obtain the appropriate particle size. The chips of uranium alloys are very pyrophoric due to its high oxidative characteristics. Thus, it is necessary to machine under a sufficient amount of cutting fluid to substantially prevent oxidation. The fuel powder is contaminated by the cutting fluid. Processes of rinsing with an organic solvent such as acetone etc. and drying under vacuum atmosphere at a high temperature are required. Also, during milling the small particles containing ferrous impurities are introduced by the wear of milling machine parts. A close-up of the particle surface reveals many dark spots on the surface which energy dispersive spectroscopy has determined to be iron-rich. Most of the particles containing ferrous components are removed by magnetic separation. As it is difficult to comminute uranium alloy ingots due to its tough property, the yield of uranium alloy through a mechanical powdering process, which consists of many steps of chipping, milling, rinsing, and drying, is very low, in the range of 5 to 20%. In addition, during magnetic separation about 30% of fuel powder is lost because separated powder contains a considerable amount of fuel particles. In the case of directly making powder having a particle size from alloy ingots using a high speed lathe equipped with a rotary file, the productivity of usable powder is very low, as it yields 12 grams per hour. The yield of powder smaller than 212 .mu.m ranges from 32.about.63% of the total powder, depending on the alloy composition. The powder is produced by grinding ingots with a tungsten/tantalum carbide tool rotating at approximately 2,500 rpm. This process has the drawback of carbide and nitride contamination in the powder due to the wear of the rotary file. Contamination levels range from 0.1.about.7.6% and are generally higher for uranium alloys with larger alloy contents. The comminuted particles with longish and irregular shapes, arranged along the rolling or extruding direction perpendicular to heat flow, inhibit thermal conduction in fuel meat. The large specific surface area of these irregular particles enhances the interaction between the fuel particles and an Al matrix to form uranium-aluminide (UAl.sub.x) with low-density around the perimeter of the uranium alloy particles, with the consequence of thermal swelling of the nuclear fuel meats. SUMMARY OF THE INVENTION This invention is concerned with dispersion fuels having atomized spherical particles and fuel fabrication processes related thereto. Spherical particles of (1) uranium and about 4-9 wt % Q alloys and (2) uranium, about 4-9 wt % Q and about 0.1-4 wt % X alloys wherein (Q is selected from Mo, Nb, and Zr; X is selected from Mo, Nb, Zr, Ru, Pt, Si, Ir, Pd, W and Ta, with proviso that; Q.noteq.X); are directly obtained from alloy melt through the rapid cooling by an atomization method. A homogenization treatment and a mechanical comminution of alloy ingots are not required. An investigation has been carried out for applying this atomization process to the development of high-density dispersion fuels. Many kinds of advantages have been obtained for exanple: 1) direct formation of meta-stable .gamma.-U phase, 2) process simplification, 3) minimization of fabrication space, 4) improvements to uranium yield, fuel productivity, powder purity, and fuel formability, 5) higher thermal conductivity in the real heat flow direction, 6) the decrease of as-fabricated porosity, and a smaller thermal swelling. The invention is directed to the particles themselves, and the dispersion furls containing the particles.
	abstract	In a method for automatic adjustment of a diaphragm in an x-ray system, the diaphragm having a number of adjustable diaphragm elements for a subsequent x-ray exposure of an examination subject, the individual diaphragm elements are respectively positioned such that, considered in a projection lying in a detector plane, abut the contours of the acquisition subject or are situated at a small distance therefrom for this positioning, first a subject localization exposure is generated with a low radiation dose with an open diaphragm. This subject localization exposure is analyzed to determine contours of the exposure subject. The positions of the diaphragm elements are calculated using the determined contours, and then the diaphragm elements are moved into the calculated positions.
	description	FIG. 1 shows an inventive system 1 composed of a radiation pick-up device 2 and a control device 3 that controls the operation thereof. The radiation pick-up device 2 is arranged in a housing 4 (which is not shown in detail). Since the sides of the housing 4 are relatively large in area, they can be provided with stabilization elements 4a, to assist in withstanding the high forces acting on the walls of the housing 4. The device 2 has a substrate 5 at the beam entry side identified with the arrow, for example in the form of a glass carrier, on which a scintillator layer 6 is applied, for example, in the form of Csl needles. This is followed by a conductive electrode layer 7 of, for example, ITO (indium tin oxide) or SnO2. This electrode layer 7 should be as thin as possible (in the range of a few 100 xc3x85) in order to avoid stray effects. A charge layer 8, preferably of amorphous silicon, is applied on this electrode layer 7. X-ray quanta incident thereon initially penetrate through the substrate 5 and subsequently penetrate into the scintillator 6 wherein conversion into visible light occurs. This light subsequently penetrates the extremely thin electrode layer and is incident on the charge layer 8. Dependent on the intensity of the penetrating light, charges are generated in the charge layer 8. These charges are read out by an electron beam with a following read-out device. This read-out device has a cooperating cathode 9 followed by a of linear cathodes 10 which can, for example, be coated tungsten wires. These linear cathodes 10 serve as electron beam sources. Further, vertically converging electrodes 11, 12 are provided, as are vertically deflecting electrodes 13. Further, an electron beam control electrode 14 as well as a horizontally converging electrode 15 and a horizontally deflecting electrode 16 are provided. The read-out device also has an electrode 17 that accelerates the electron beam, and a retarding electrode 18. In the illustrated example, the linear cathodes 10 extend horizontally and enable the generation of an electron beam having a linear horizontal expanse. Of course, more than the four electrodes 10 that are shown can be provided, dependent on the size of the panel. The cooperating electrodes 9 serve the purpose of generating a potential gradient with the vertically converging electrodes 11 in order to prevent the generation of electron beams from cathodes 10 other than the cathode driven for the emission of the electron beam. Each vertically converging electrode 11 and 12 is plate-shaped and has a of oblong slots 19, each slot lying opposite a linear cathode 10. Each of the electron beams emitted by the cathodes 10 passes through a slot 19, causing the beam to converge vertically. The vertically deflecting electrodes 13 are allocated to the respective slots 19 and are composed of upper and lower conductor 20 between which an insulator 21 is provided. When a voltage is applied between two conductors 20 lying opposite one another in two different electrodes 13, then an electron beam that passes therethrough is deflected. The electron beam control electrode 14 is composed of a number of individual electrodes that each have an oblong slot 22. An electron beam can pass only through the slot of a correspondingly driven electron beam control electrode. An electron beam that passes through is employed for reading out the signals of a number of horizontally arranged pixels, for example ten pixels, i.e. distributions of electrical potential on the charge layer 8. After the ten pixels adjacent to this currently driven electrode are read out, then the electron beam control electrode skips ahead to the next driven electrode. The horizontally converging electrode 15 is likewise plate-shaped and has a number of individual slots 23 that are respectively positioned opposite the slots 22. This electrode 15 causes the electron beam to be contracted horizontally to form a thin ray corresponding to the size of a pixel or to a distribution of potential. The horizontally deflecting electrode 16 also has the shape of a conductive plate that is composed of individual plate segments. When a voltage is applied between two neighboring plate segments, then the electron beam can be horizontally deflected, and the allocated pixels or distributions of potential, for example ten pixels, are horizontally scanned. The acceleration electrodes 17 also are plate-shaped here and serve the purpose of accelerating the electron beam. The retarding electrode 18 has the shape of a grid conductor with numerous grid openings and serves the purpose of retarding the electron beam immediately before the charge layer 8 and of guiding the electron beam such that it strikes the charge layer at the correct angle. As shown, a high-voltage V is applied to the electrode layer 7, the amplitude thereof being controlled via the control device 3. As a result, a high-voltage is also present across the charge layer 8. This induces an avalanche effect in the charge layer 8, dependent on the amplitude of the high-voltage that is applied as well as on the number of electrons that are generated in the quanta-to-photon. By variation of the high-voltage V, the gain via the charge layer 8 can be set, so that switching can be carried out in a simple way between different operating modes that need different gains. This can ensue very quickly, particularly by using reset light 24 serving the purpose of exposing the charge layer 8. This reset light 24 can be operated, for example, in a pulsed manner by the control device 3 and causes the potential at the free surface of the charge layer 8 to be stabilized. The reset light 24 is mainly utilized for stabilizing the potential and thus for setting a desired potential when the following image exposure was previously preceded by an image exposure having low radiation dose, and thus a high gain. FIG. 2 shows the enlarged excerpt II from FIG. 1 in the form of a schematic diagram, showing the substrate 15, for example in the form of a glass plate, onto which the scintillator 6 is applied. An intermediate carrier 25 is in turn applied on the scintillator 6, for example in the form of the glass plate. An intermediate carrier 25, for example in the form of a glass film, is in turn applied thereon, the electrode layer 7, preferably being printed on the intermediate carrier 25, for in the form of the ITO electrode. The electrode layer 7 can be composed of a number of parallel, preferably vertically arranged, electrode stripes 7a (see FIG. 4). Finally, the charge layer 8 is applied onto the electrode layer 7. As shown, the high-voltage V is applied to the electrode layer 7. FIG. 3 is a schematic diagram of a second embodiment of an inventive system 26. The structure at the beam entry side (substrate, scintillator, electrode layer, charge layer) is the same as in the previously described embodiment, however, a different readout device is employed in the embodiment of FIG. 3. In this read-out device, a micro-structured electron emitter cathode 27 is provided as a flat emitter device, this being shown in the form of a schematic diagram. Any micro-structured emitter cathode that allows a targeted, punctiform emission of the electrons can be utilized, for example in the form of nano-tubes or micro-tips. Here, as well, the emitted electron beam is shaped by corresponding electrodes (not shown) and strikes the charge layer for the readout, a potential due to the high-voltage V at the electrode layer also being present across the charge layer. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.
	abstract	Self-loading systems and methods for disposal of waste materials in a deep underground formation may include at least one wellbore that runs from the Earth's surface to the deep underground formations, wellbore viscous fluid within that at least one wellbore, and at least one waste capsule, wherein the at least one waste capsules houses some waste and is configured to fall within both the at least one wellbore and the wellbore viscous fluid. The systems and methods may also include at least one human-made cavern located in the deep underground formation and connected to the at least one wellbore, wherein the at least one human-made cavern may be configured to receive the at least one waste capsule. The systems and methods may also include a counter for counting waste capsules and/or a robot for dropping waste capsules into a wellhead leading to the at least one wellbore.
	description	This invention was made with Government support under contract number DE-FC07-07ID14778, awarded by the U.S. Department of Energy. The United States Government has certain rights in the invention. 1. Field Example embodiments relate to neutron monitoring systems including gamma thermometers and methods of calibrating nuclear instruments using gamma thermometers. Also, example embodiments relate to neutron monitoring systems including gamma thermometers in which nuclear instruments of the neutron monitoring systems are calibrated using compensated signals from the gamma thermometers. Additionally, example embodiments relate to methods of calibrating nuclear instruments using compensated signals from the gamma thermometers. 2. Description of Related Art FIG. 1 is a sectional view, with parts cut away, of reactor pressure vessel (“RPV”) 100 in a related art boiling water reactor (“BWR”). As known to a person having ordinary skill in the art (“PHOSITA”), during operation of the BWR, coolant water circulating inside RPV 100 is heated by nuclear fission produced in core 102. Feedwater is admitted into RPV 100 via feedwater inlet 104 and feedwater sparger 106 (a ring-shaped pipe that includes apertures for circumferentially distributing the feedwater inside RPV 100). The feedwater from feedwater sparger 106 flows down through downcomer annulus 108 (an annular region between RPV 100 and core shroud 110). Core shroud 110 is a stainless steel cylinder that surrounds core 102. Core 102 includes a multiplicity of fuel bundle assemblies 112 (two 2×2 arrays, for example, are shown in FIG. 1). Each array of fuel bundle assemblies 112 is supported at or near its top by top guide 114 and at or near its bottom by core plate 116. Top guide 114 provides lateral support for the top of fuel bundle assemblies 112 and maintains correct fuel-channel spacing to permit control rod insertion. The coolant water flows downward through downcomer annulus 108 and into core lower plenum 118. The coolant water in core lower plenum 118 in turn flows up through core 102. The coolant water enters fuel assemblies 112, wherein a boiling boundary layer is established. A mixture of water and steam exits core 102 and enters core upper plenum 120 under shroud head 122. Core upper plenum 120 provides standoff between the steam-water mixture exiting core 102 and entering standpipes 124. Standpipes 124 are disposed atop shroud head 122 and in fluid communication with core upper plenum 120. The steam-water mixture flows through standpipes 124 and enters steam separators 126 (which may be, for example, of the axial-flow, centrifugal type). Steam separators 126 substantially separate the steam-water mixture into liquid water and steam. The separated liquid water mixes with feedwater in mixing plenum 128. This mixture then returns to core 102 via downcomer annulus 108. The separated steam passes through steam dryers 130 and enters steam dome 132. The dried steam is withdrawn from RPV 100 via steam outlet 134 for use in turbines and other equipment (not shown). The BWR also includes a coolant recirculation system that provides the forced convection flow through core 102 necessary to attain the required power density. A portion of the water is sucked from the lower end of downcomer annulus 108 via recirculation water outlet 136 and forced by a centrifugal recirculation pump (not shown) into a plurality of jet pump assemblies 138 (only one of which is shown) via recirculation water inlets 140. Jet pump assemblies 138 are circumferentially distributed around core shroud 110 and provide the required reactor core flow. As shown in FIG. 1, a related art jet pump assembly 138 includes a pair of inlet mixers 142. A related art BWR includes 16 to 24 inlet mixers 142. Each inlet mixer 142 has an elbow 144 welded to it that receives water from a recirculation pump (not shown) via inlet riser 146. An example inlet mixer 142 includes a set of five nozzles circumferentially distributed at equal angles about the axis of inlet mixer 142. Each nozzle is tapered radially inwardly at its outlet. Jet pump assembly 138 is energized by these convergent nozzles. Five secondary inlet openings are radially outside of the nozzle exits. Therefore, as jets of water exit the nozzles, water from downcomer annulus 108 is drawn into inlet mixer 142 via the secondary inlet openings, where it is mixed with coolant water from the recirculation pump. The coolant water then flows into jet pump assembly 138. FIG. 2 is a top plan view of a related art core 200. As known to a PHOSITA, core 200 may include fuel bundles 202, peripheral fuel bundles 204, and/or control rods 206. Two or more of fuel bundles 202 may be included in fuel bundle assemblies 208. Core 200 may include, for example, hundreds or thousands of fuel bundles 202 and/or tens or hundreds of peripheral fuel bundles 204. As shown in FIG. 2, for example, core 200 may include approximately one thousand and twenty-eight (1,028) fuel bundles 202, approximately one hundred and four (104) peripheral fuel bundles 204, and/or approximately two hundred and sixty-nine (269) control rods 206. The distribution of fuel bundles 202, peripheral fuel bundles 204, and/or control rods 206 in core 200 may or may not be symmetric. Additionally, if symmetry exists, it may include one or more of mirror-image symmetry, diagonal symmetry, rotational symmetry, translational symmetry, quadrant symmetry, and octant symmetry. As shown in FIG. 2, for example, one or more control rods 206 may be disposed in or near a geometric center of core 200. Core 200 also may include one or more types of neutron monitors. These monitors may include, for example, one or more source range monitors, one or more intermediate range monitors, and/or one or more power range monitors. In a related art BWR, the one or more source range monitors may be fixed or movable. Similarly, in a related art BWR, the one or more intermediate range monitors may be fixed or movable. At least some of the overall range of a related art source range monitor and/or a related art intermediate range monitor may be covered by a startup range neutron monitor (“SRNM”) or wide range neutron monitor (“WRNM”). Similarly, at least some of the overall range of a related art intermediate range monitor and/or a related art power range monitor may be covered by a local power range monitor (“LPRM”). In a related art BWR, the SRNMs and/or the LPRMs may be fixed. Core 200 may include, for example, tens of SRNM detectors and/or tens or hundreds of LPRM detectors. Although not shown in FIG. 2, core 200 may include, for example, approximately twelve (12) SRNM detectors. As shown in FIG. 2, for example, core 200 may include approximately two hundred and fifty-six (256) LPRM detectors in approximately sixty-four (64) LPRM assemblies 210. For example, one or more LPRM assemblies 210 may include four LPRM detectors (i.e., each LPRM assembly 210 may include four LPRM detectors). FIG. 3 is a perspective view, partly broken away, showing a structure of a related art gamma thermometer (“GT”) assembly 300. FIG. 4 is a view showing a principle for measuring a gamma ray heating value of GT assembly 300. As known to a PHOSITA and as discussed, for example, in U.S. Pat. No. 6,310,929 B1 (“the '929 patent”) and U.S. Pat. No. 6,408,041 B2 (“the '041 patent”), GT assembly 300 may include a thin and long rod-like assembly having a length substantially covering an effective fuel length of core 200 (e.g., between about 3 m and about 5 m in an axial direction of core 200. The equations and associated explanations of the '929 patent and the '041 patent are incorporated herein by reference. As shown in FIG. 3, GT assembly 300 may include cover tube 302 and core tube 304. Annular space portions 306 may be formed between cover tube 302 and core tube 304. Each annular space portion 306 may form an adiabatic portion of GT assembly 300. For that purpose, annular space portions 306 may be filled with a gas having a low heat conductivity, such as argon (or another inert gas) or nitrogen. GT assembly 300 may include four or more annular space portions 306 (e.g., eight or nine). Annular space portions 306 may be discretely arranged at equal intervals in an axial direction of GT assembly 300. Core tube 304 may have an internal hole 308 (see FIG. 4) that may extend through a center portion of core tube 304 along an axial direction of core tube 304. Cable sensor assembly 310 may be fixed inside internal hole 308. Cable sensor assembly 310 may include built-in heater 312, plurality of differential-type thermocouples 314, and cladding tube 316. Built-in heater 312 may function as an exothermic member of a heater wire for calibrating GT assembly 300. Differential-type thermocouples 314 may function as temperature sensors around built-in heater 312. Spaces within cladding tube 316 that are not occupied by built-in heater 312 or differential-type thermocouples 314 may be filled with electric insulating layer or metal/metal-alloy filler 318. Built-in heaters 312 may include cladding tubes 320, electric insulating layers 322, and/or heater wires 324. Differential-type thermocouples 314 may include cladding tubes 326, electric insulating layers 328, and/or thermocouple signal wires 330. GT assembly 300 may include gamma ray heating detectors 332 (i.e., GT detectors 332). GT detectors 332 may be fixed at an axial position of GT assembly 300 near corresponding annular space portions 306. Each GT detector 332 may include high-temperature point 334 (also known as the insulated or hot junction) and low-temperature point 336 (also known as the uninsulated or cold junction) of differential-type thermocouple 314. High-temperature point 334 may be near corresponding annular space portion 306. Low-temperature point 336 may be below or above corresponding annular space portion 306. During steady-state operation, gamma ray flux may be proportional to thermal neutron flux. The gamma ray flux may deposit energy in the form of heat in structural elements of GT assembly 300, such as core tube 304. The deposited heat energy may be proportional to the gamma ray flux. Because the removal of heat energy from GT detector 332 in a vicinity of annular space portions 306 is relatively low while the removal of heat energy from GT detectors 332 not in a vicinity of annular space portions 306 is relatively high, a temperature difference may develop between high-temperature point 334 and low-temperature point 336 of differential-type thermocouple 314. This temperature difference may be detected as a voltage difference in differential-type thermocouple 314, may be proportional to the gamma ray flux and, thus, may be proportional to thermal neutron flux. Therefore, during steady-state operation, GT assembly 300 effectively may measure thermal neutron flux. Characteristic values for GT detector 332 may include sensitivity S0 (in millivolts per watt per gram or mV/(W/g)) and/or alpha factor α (in 1/mV or mV−1). Although typically written as S0, sensitivity S0 may be understood to be time-dependent and, thus, may be written as S0(t). Alpha factor α may represent a temperature dependence related to physical properties of the structural material of GT detector 332. Alpha factor α may be considered to have a constant value. Due to exposure in the high neutron and/or gamma flux environment of core 200, sensitivity S0(t) generally may decrease over time. This decrease may be expressed using Equation (1) below, where S0(0)=a+b.S0(t)=a+bexp(−λt) (1) As known to a PHOSITA, values for a, b, and λ may be predicted based on previous data and/or experience. As also known to a PHOSITA, values for a, b, and λ may be calculated and/or verified based on data recorded during GT calibrations. As discussed above, when calibrating GT assembly 300, built-in heater 312 may function as an exothermic member, providing additional heating PH (in W/g). A relationship between sensitivity S0(t), alpha factor α, unheated output voltage U (in mV) of GT detector 332, heated output voltage U′ (in mV) of GT detector 332, and additional heating PH of GT detector 332 may be expressed using Equation (2) below.S0(t)={[U′/(1+αU′)]−[U/(1+αU)]}/PH (2) When not calibrating GT assembly 300, a relationship between sensitivity S0(t), alpha factor α, output voltage Uγ (in mV) of GT detector 332, and gamma ray heating value Wγ (in W/g) of GT detector 332 may be expressed using Equation (3) below.Uγ=S0(t)(1+αUγ)Wγ (3) Rearranging Equation (3) above may allow the calculation of gamma ray heating value Wγ using Equation (4) below.Wγ=Uγ/[S0(t)(1+αUγ)] (4) FIG. 5 is a perspective view, partly broken away, showing an arrangement relationship of detectors of an in-core fixed nuclear instrumentation system of a related art power distribution monitoring system. FIG. 6 is a front view, partly broken away, showing the arrangement relationship of the detectors in FIG. 5. As known to a PHOSITA, core 500 may include a large number of groups of four fuel assemblies 502. An in-core nuclear instrumentation system may include a plurality of in-core nuclear instrumentation assemblies 504. In-core nuclear instrumentation assemblies 504 may be disposed at corner water gap 506, surrounded by a group of four fuel assemblies 502. In-core nuclear instrumentation assemblies 504 may be disposed at different positions in core 500 from control rods 508. In-core nuclear instrumentation assemblies 504 may include a thin and long nuclear instrumentation tube 510, LPRM detector assembly 512, and GT detector assembly 514. LPRM detector assembly 512, housed in nuclear instrumentation tube 510, may function as a fixed neutron detection means. LPRM detector assembly 512 may include a plurality (e.g., four) of LPRM detectors 516. LPRM detectors 516 may be discretely arranged in an axial direction of core 500, at equal intervals L in nuclear instrumentation tube 510. LPRM detectors 516 may substantially cover an effective fuel length H (see FIG. 6) of core 500. Each LPRM detector 516 may be configured to measure neutron flux so as to generate a neutron flux signal (LPRM signal) according to the measured neutron flux. And each LPRM detector 516 may be electrically connected to an LPRM signal processing unit (not shown). GT detector assembly 514, also housed in nuclear instrumentation tube 510, may function as a fixed gamma ray detection means. GT detector assembly 514 may include a plurality (e.g., eight) of GT detectors 332. GT detectors 332 may be discretely arranged in an axial direction of core 500 in nuclear instrumentation tube 510. GT detectors 332 may substantially cover the effective fuel length H of core 500. Each GT detector 332 may be configured to measure gamma ray flux so as to generate a gamma ray flux signal (GT signal) according to the measured gamma ray flux. And each GT detector 332 may be electrically connected to a GT signal processing unit (not shown). A large number of fuel rods (not shown) may be housed in channel box 518. Channel box 518 may be, for example, rectangular or cylindrical. FIG. 7 is a block diagram showing schematically a structure of a reactor power distribution monitoring system of a BWR. As known to a PHOSITA, reactor power distribution monitoring system 700 of a BWR may include an in-core fixed nuclear instrumentation system 702. In-core fixed nuclear instrumentation system 702 may have detectors, signal processing units, and process control computer 704 for monitoring an operating mode of the BWR and/or core performance. Process control computer 704 may include, for example, central processing unit (“CPU”) 706, memory unit 708, input console 710, and/or display unit 712. CPU 706 may be electrically connected to memory unit 708, input console 710, and display unit 712 so as to enable communication between them. Process control computer 704 may include a function for simulating a core power distribution of the BWR and/or a function for monitoring a core performance of the BWR according to the simulated core power distribution. As shown in FIG. 7, core 500 may be housed in reactor pressure vessel 714. Reactor pressure vessel 714 may be housed in primary containment 716. As discussed above, each LPRM detector 516 may be configured to measure neutron flux so as to generate a neutron flux signal (LPRM signal) according to the measured neutron flux. And each LPRM detector 516 may be electrically connected to LPRM signal processing unit 718 using signal cables 720 through penetration portion 722, forming power range neutron flux measuring system 724. LPRM signal processing unit 718 may include a computer having a CPU, a memory unit, and so on. As known to a PHOSITA, LPRM signal processing unit 718 may be operative to perform, for example, analog-to-digital (“A/D”) conversion operations and/or gain processing operations of each LPRM signal S2 transmitted from each LPRM detector 516 so as to obtain digital LPRM data D2, and then to transmit digital LPRM data D2 to process control computer 704. As discussed above, GT detector assembly 514 may be configured so that a plurality of GT detectors 332 may be discretely arranged in the axial direction of core 500. A gamma ray heating value may be measured by each GT detector 332. The number of GT detectors 332 should be the same as or more than the number of LPRM detectors 516. Each GT detector 332 may be electrically connected to GT signal processing unit 726 using signal cable 728 through penetration portion 730, forming GT power distribution measuring system 732. As known to a PHOSITA, GT signal processing unit 726 may be configured to obtain digital GT data D1 using GT signals S1 outputted from GT detectors 332, as well as sensitivity S0 and alpha factor α of the respective GT detector 332. Digital GT data D1 may represent a gamma ray heating value in watts per gram of unit weight (W/g). GT signal processing unit 726 may be operative to transmit digital GT data D1 to process control computer 704. In-core fixed nuclear instrumentation system 702 may include gamma ray thermometer heater control unit 734. Gamma ray thermometer heater control unit 734 may be electrically connected to each built-in heater 312 using power cables 746. Core state data measuring device 736 may be provided in reactor pressure vessel 714 and/or primary system piping (not shown). Core state data measuring device 736 may provide core state data signal S3. Core state data signal S3 may include, for example, control rod pattern, core coolant flow rate, internal pressure of reactor pressure vessel 714, feed water flow rate, feed water temperature (e.g., core inlet coolant temperature), and so on. Core state data signal S3 may be used as various operating parameters indicative of a reactor operating mode (state) of the BWR. A first part of core state data measuring device 736, inside reactor pressure vessel 714, may be connected to core state data processing unit 738 using signal cable 740 through penetration portion 742. A second part of core state data measuring device 736, outside reactor pressure vessel 714, may be connected using signal cable 740 to core state data processing unit 738. The first and/or second parts of core state data measuring device 736 may form process data measuring system 744. As known to a PHOSITA, core state data processing unit 738 may be configured to obtain digital core state data D3 using core state data signal S3. Core state data processing unit 738 may be operative to transmit digital core state data D3 to process control computer 704. CPU 706 may include nuclear instrumentation control process module 748 and/or power distribution simulation process module 750. Nuclear instrumentation control process module 748 may monitor and/or control in-core fixed nuclear instrumentation system 702. As known to a PHOSITA, power distribution simulation process module 750 may correct the power distribution simulation result of nuclear instrumentation control process module 748, using digital GT data D1, digital LPRM data D2, and/or digital core state data D3, in order to obtain a core power distribution reflecting the actually measured data in core 500. Memory unit 708 may include nuclear instrumentation control program module PM1, power distribution simulation program module PM2, and/or power distribution learning (adaptive) program module PM3. Power distribution simulation program module PM2 may include a physics model, such as a three-dimensional thermal-hydraulic simulation code. Power distribution simulation process module 750 may simulate neutron flux distribution in core 500, may simulate power distribution in core 500, and/or may simulate margins with respect to one or more operational thermal limits (e.g., maximum linear heat generation rate (“MLHGR”) and/or minimum critical power ratio (“MCPR”)) using power distribution simulation program module PM2. Power distribution simulation process module 750 may be operative to correct the simulation results in order to obtain a core power distribution reflecting the actually measured core nuclear instrumentation data on the basis of power distribution learning (adaptive) program module PM3. As discussed above, power distribution simulation process module 750 may correct the simulated results (neutron flux distribution and/or power distribution in core 500) stored in memory unit 708—according to inputted digital GT data D1, digital LPRM data D2, and/or digital core state data D3—in order to determine an accurate core power distribution and/or an accurate margin with respect to the one or more operational thermal limits, which reflect the actual core nuclear instrumentation data (digital GT data D1, digital LPRM data D2, and/or digital core state data D3). As known to a PHOSITA, LPRM detectors generally may include a cathode having fissionable material coated on the cathode. The fissionable material may be a mixture of U234 and U235. The U235 may be used to provide a signal proportional to the thermal neutron flux. But due to the extremely high thermal neutron flux in the nuclear reactor core, the U235 may be subject to burnout, which may cause the LPRM detector reading corresponding to a constant thermal neutron flux to gradually decrease over time. The U234 may absorb thermal neutrons to become U235, lengthening the life of the LPRM detector. Eventually, however, the LPRM detector reading corresponding to a constant thermal neutron flux may still gradually decrease over time. As also known to a PHOSITA, a gamma thermometer may provide a capability to calibrate an associated LPRM detector. During steady-state operation, gamma flux may be proportional to thermal neutron flux. Thus, a gamma thermometer—located near the associated LPRM detector—may measure local gamma flux during a steady-state heat balance, as known to a PHOSITA. The local gamma flux may be related to the proportional thermal neutron flux and the associated LPRM detector may be calibrated based on the related proportional thermal neutron flux. Various solutions to the problem of calibrating nuclear instruments in nuclear reactors—using gamma thermometers—have been proposed, as discussed, for example, in U.S. Pat. No. 4,614,635 (“the '635 patent”), U.S. Pat. No. 5,015,434 (“the '434 patent”), U.S. Pat. No. 5,116,567 (“the '567 patent”), and U.S. Pat. No. 5,204,053 (“the '053 patent”), as well as U.S. Patent Publication No. 2009/0135984 A1 (“the '984 publication”). The disclosures of the '635 patent, the '434 patent, the '567 patent, the '053 patent, and the '984 publication are incorporated in the present application by reference. However, these various solutions do not include calibrating nuclear instruments in nuclear reactors—using gamma thermometers—wherein the calibrating of the nuclear instruments may be performed simply, automatically, in real-time, and/or with reduced cost when the associated nuclear reactor is not in steady-state operation. FIG. 8 is a block diagram of a related art GT signal processor 800 of a BWR. As known to a PHOSITA and as discussed, for example, in Japanese Laid-Open Patent Publication No. 2001-083280 (“JP '280”)—and its associated machine translation—GT signal processor 800 of a BWR may include GT signal site board 802, GT control panel 804, and/or a communication circuit (via transmitter 834 and optical cable 836) between GT signal site board 802 and GT control panel 804. The equations and associated explanations of JP '280 and its associated machine translation are incorporated herein by reference. GT signal site board 802 may include amplifiers 806, low-pass filters 808, multiplexer 810, A/D converter 812, signal holding circuit 814, digital signal processor (“DSP”) 816, memory 818, and/or input/output (“I/O”) buffer 820. Delayed gamma compensation module 822 may include signal holding circuit 814, digital signal processor (“DSP”) 816, and/or memory 818. GT control panel 804 may include transmitter 824, CPU 826, I/O buffer 828, memory 830, and/or display console 832. FIG. 8 also depicts transmitter 834, optical cable 836, GT heater control panel 838, I/O machine 840, heater wires 842, additional GT signal site board or boards 844, and/or differential thermocouples 846. Delayed gamma compensation module 822 of GT signal processor 800 may disclose calibrating nuclear instruments in nuclear reactors—using gamma thermometers—wherein the calibrating of the nuclear instruments may be performed when the associated nuclear reactor is not in steady-state operation. Delayed gamma compensation module 822 may define a total GT signal R(t) (in mV) to include a prompt component [a0P(t)] (in mV) and a delayed component [Σ amum(t), where in the summation Σ, m=1, 2, . . . , M] (in mV), as shown in Equation (5) below.R(t)=a0P(t)+Σ(amum(t)) (5) In Equation (5), a0 may represent a constant term, P(t) may represent an instant response term, am may represent constant terms, and um(t) may represent a delayed response term, defined by Equation (6) below.um(t)=1/τm∫P(t′)exp[−(t−t′)/τm]dt′ (6) The integration in Equation (6) may be performed from t=−∞ to t, and τm may be a thermal time constant. Rearranging Equation (5) above may allow the calculation of instant response term P(t) using Equation (7) below.P(t)=[R(t)−Σ(amum(t))]/a0 (7) As known to a PHOSITA, instant response term P(t) for a given GT detector 332 may be converted to digital GT data D1 and then compared to digital LPRM data D2 for the purpose of calibrating a corresponding LPRM detector 516. Example embodiments may relate to neutron monitoring systems including gamma thermometers and methods of calibrating nuclear instruments using gamma thermometers. Also, example embodiments may relate to neutron monitoring systems including gamma thermometers in which nuclear instruments of the neutron monitoring systems are calibrated using compensated signals from the gamma thermometers. Additionally, example embodiments may relate to methods of calibrating nuclear instruments using compensated signals from the gamma thermometers. In example embodiments, a method of calibrating a nuclear instrument using a gamma thermometer may include: measuring, in the nuclear instrument, local neutron flux; generating, from the nuclear instrument, a first signal proportional to the measured local neutron flux; measuring, in the gamma thermometer, local gamma flux; generating, from the gamma thermometer, a second signal proportional to the measured local gamma flux; compensating the second signal; and/or calibrating a gain of the nuclear instrument based on the compensated second signal. Compensating the second signal may include: calculating selected yield fractions for specific groups of delayed gamma sources; calculating time constants for the specific groups of delayed gamma sources; calculating a third signal that corresponds to delayed local gamma flux based on the selected yield fractions and time constants; and/or calculating the compensated second signal by subtracting the third signal from the second signal. The specific groups of delayed gamma sources may have decay time constants greater than 5×10−1 seconds and less than 5×105 seconds. In example embodiments, a method of using a gamma thermometer may include: measuring, in the gamma thermometer, local gamma flux; generating, from the gamma thermometer, a first signal proportional to the measured local gamma flux; compensating the first signal; and/or calibrating a gain of a nuclear instrument based on the compensated first signal. Compensating the first signal may include: calculating selected yield fractions for specific groups of delayed gamma sources; calculating time constants for the specific groups of delayed gamma sources; calculating a second signal that corresponds to delayed local gamma flux based on the selected yield fractions and time constants; and/or calculating the compensated first signal by subtracting the second signal from the first signal. The specific groups of delayed gamma sources may have decay time constants greater than 5×10−1 seconds and less than 5×105 seconds. In example embodiments, a neutron monitoring system may include: a plurality of nuclear instruments; a plurality of gamma thermometers; a processor; and/or a memory. Each gamma thermometer may be associated with one of the nuclear instruments. Each nuclear instrument may measure local neutron flux and/or may generate a first signal proportional to the measured local neutron flux. Each gamma thermometer may measure local gamma flux and/or may generate a second signal proportional to the measured local gamma flux. Selected yield fractions for specific groups of delayed gamma sources may be calculated by the processor, stored in the memory, or calculated by the processor and stored in the memory. Time constants for the specific groups of delayed gamma sources may be calculated by the processor, stored in the memory, or calculated by the processor and stored in the memory. The processor may calculate, for each gamma thermometer, a third signal that corresponds to delayed local gamma flux based on the selected yield fractions and/or time constants. The processor may calculate a compensated second signal, for each gamma thermometer, by subtracting the third signal from the second signal. A gain of each nuclear instrument may be calibrated based on the compensated second signal for the associated gamma thermometer. The specific groups of delayed gamma sources may have decay time constants greater than 5×10−1 seconds and less than 5×105 seconds. Example embodiments will now be described more fully with reference to the accompanying drawings. Embodiments, however, may be embodied in many different forms and should not be construed as being limited to the example 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 to those skilled in the art. It will be understood that when a component is referred to as being “on,” “connected to,” “coupled to,” or “fixed to” another component, it may be directly on, connected to, coupled to, or fixed to the other component or intervening components may be present. In contrast, when a component is referred to as being “directly on,” “directly connected to,” “directly coupled to,” or “directly fixed to” another component, there are no intervening components present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that 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 element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments. Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like may be used herein for ease of description to describe one component and/or feature relative to another component and/or feature, or other component(s) and/or feature(s), as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” 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, and/or components. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a PHOSITA to which example embodiments belong. It will be further understood that terms, such as 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 should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Reference will now be made to example embodiments, which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like components throughout. As discussed above, although the example embodiments are described in terms of BWRs (such as, for example, an Economic Simplified BWR (“ESBWR”)), a PHOSITA should recognize that example embodiments also apply to other types of nuclear reactors such as, for example, other water-cooled and/or water-moderated reactors [e.g., pressurized water reactors (“PWR”), pool-type reactors, and heavy water reactors], gas-cooled reactors (“GCR”) [e.g., advanced gas-cooled reactors (“AGR”)], liquid-metal-cooled reactors, and molten-salt reactors (“MSR”). FIG. 9 is a block diagram showing schematically a structure of a reactor power distribution monitoring system according to example embodiments. Reactor power distribution monitoring system 900 may include an in-core fixed nuclear instrumentation system 902. In-core fixed nuclear instrumentation system 902 may have detectors, signal processing units, and process control computer 904 for monitoring an operating mode of the BWR and/or core performance. Process control computer 904 may include, for example, CPU 954, memory unit 956, input console 958, and/or display unit 960. CPU 954 may be electrically connected to memory unit 956, input console 958, and display unit 960 so as to enable communication between them. Process control computer 904 may include a fimction for simulating a core power distribution of the BWR and/or a function for monitoring a core performance of the BWR according to the simulated core power distribution. As shown in FIG. 9, core 906 may be housed in reactor pressure vessel 908. Reactor pressure vessel 908 may be housed in primary containment 910. In-core nuclear instrumentation assemblies 912 may include a thin and long nuclear instrumentation tube 914, LPRM detector assembly 916, and GT detector assembly 918. LPRM detector assembly 916 may function as a fixed neutron detection means. LPRM detector assembly 916 may include a plurality (e.g., four) of LPRM detectors 920. LPRM detectors 920 may be discretely arranged in an axial direction of core 906, at equal intervals. LPRM detectors 920 may substantially cover an effective fuel length of core 906. Each LPRM detector 920 may be configured to measure neutron flux so as to generate a neutron flux signal (LPRM signal) according to the measured neutron flux. And each LPRM detector 920 may be electrically connected to an LPRM signal processing unit 922. GT detector assembly 918, also housed in nuclear instrumentation tube 914, may function as a fixed gamma ray detection means. GT detector assembly 918 may include a plurality (e.g., seven) of GT detectors 924. Each LPRM detector 920 may be configured to measure neutron flux so as to generate a neutron flux signal (LPRM signal) according to the measured neutron flux. And each LPRM detector 920 may be electrically connected to LPRM signal processing unit 922 using signal cables 926 through penetration portion 928, forming power range neutron flux measuring system 930. LPRM signal processing unit 922 may include a computer having a CPU, a memory unit, and so on. LPRM signal processing unit 922 may be configured to receive LPRM signals S2 outputted from LPRM detectors 920. LPRM signal processing unit 922 may be operative to perform, for example, analog-to-digital (“A/D”) conversion operations and/or gain processing operations of each LPRM signal S2 transmitted from LPRMs detector 920 so as to obtain digital LPRM data D2. LPRM signal processing unit 922 may be operative to transmit digital LPRM data D2 to process control computer 904. GT detector assembly 918 may be configured so that the plurality of GT detectors 924 may be discretely arranged in the axial direction of core 906. A gamma ray heating value may be measured by each GT detector 924. The number of GT detectors 924 should be the same as or more than the number of LPRM detectors 920. Each GT detector 924 may be electrically connected to GT signal processing unit 932 using signal cables 934 through penetration portion 936, forming GT power distribution measuring system 938. GT signal processing unit 932 may be configured to receive GT signals S1 outputted from GT detectors 924, as well as sensitivity S0 and alpha factor α of the respective GT detectors 924. Digital GT data D1 may represent a gamma ray heating value in watts per gram of unit weight (W/g). GT signal processing unit 932 may convert GT signals S1 into digital GT data D1. GT signal processing unit 932 may be operative to transmit digital GT data D1 to process control computer 904. In-core fixed nuclear instrumentation system 902 may include gamma ray thermometer heater control unit 940. Gamma ray thermometer heater control unit 940 may be electrically connected to each built-in heater using power cables 942. Core state data measuring device 944 may be provided in reactor pressure vessel 908 and/or primary system piping (not shown). Core state data measuring device 944 may represent multiple measurement systems, including thermocouples, pressure sensors, venturies, pressure sensors, electrical position sensors, and others, many of which may be physically located outside reactor pressure vessel 908 and/or primary containment 910. Core state data measuring device 944 may provide core state data signals S3. Core state data signals S3 may include, for example, control rod pattern, core coolant flow rate, internal pressure of reactor pressure vessel 908, feed water flow rate, feed water temperature (e.g., core inlet coolant temperature), and so on. Core state data signals S3 may be used as various operating parameters indicative of a reactor operating mode (state) of the BWR. A first part of core state data measuring device 944, inside reactor pressure vessel 908, may be connected to core state data processing unit 946 using signal cable 948 through penetration portion 950. A second part of core state data measuring device 944, outside reactor pressure vessel 908, may be connected using signal cable 948 to core state data processing unit 946. The first and/or second parts of core state data measuring device 944 may form process data measuring system 952. Core state data processing unit 946 may be configured to receive core state data signals S3. Core state data processing unit 946 may convert core state data signals S3 into digital core state data D3. Core state data processing unit 946 may be operative to transmit digital core state data D3 to process control computer 904. CPU 954 may include, for example, a nuclear instrumentation control process module (not shown) and/or a power distribution simulation process module (not shown). The nuclear instrumentation control process module may monitor and/or control in-core fixed nuclear instrumentation system 902. The power distribution simulation process module may correct the power distribution simulation result of nuclear instrumentation control process module, using digital GT data D1, digital LPRM data D2, and/or digital core state data D3, in order to obtain a core power distribution reflecting the actually measured data in core 906. Memory unit 956 may include, for example, a nuclear instrumentation control program module (not shown), a power distribution simulation program module (not shown), and/or a power distribution learning (adaptive) program module (not shown). The power distribution simulation program module may include a physics model, such as a three-dimensional thermal-hydraulic simulation code. The power distribution simulation process module may simulate neutron flux distribution in core 906, may simulate power distribution in core 906, and/or may simulate margins with respect to one or more operational thermal limits (e.g., maximum linear heat generation rate (“MLHGR”) and/or minimum critical power ratio (“MCPR”)) using the power distribution simulation program module. The power distribution simulation process module may be operative to correct the simulation results in order to obtain a core power distribution reflecting the actually measured core nuclear instrumentation data on the basis of the power distribution learning (adaptive) program module. As discussed above, the power distribution simulation process module may correct the simulated results (neutron flux distribution and/or power distribution in core 906) stored in memory unit 956—according to inputted digital GT data D1, digital LPRM data D2, and/or digital core state data D3—in order to determine an accurate core power distribution and/or an accurate margin with respect to the one or more operational thermal limits, which reflect the actual core nuclear instrumentation data (digital GT data D1, digital LPRM data D2, and/or digital core state data D3). In example embodiments, gamma compensation may be performed in GT signal processing unit 932 and/or process control computer 904. For the gamma compensation, core 906 may be assumed to be close to thermal equilibrium, with the temperature in core 906 changing slowly, so that thermal lag may be ignored (thermal lag may have, for example, a time constant between about 15 seconds and 30 seconds). In example embodiments, gamma compensation values may be calculated that may express the uncompensated and compensated yield fractions of gamma ray energy released in the fission process due to delayed gamma rays. The values may vary depending on the fissionable nuclide(s) and/or other actinide(s) considered. The effect of the delayed gamma rays may be approximated by a weighted sum of decaying exponential functions, each having an associated decay time constant. In example embodiments, the sources of the delayed gamma rays may have decay time constants greater than 5×10−1 seconds and/or less than 5×105 seconds. In example embodiments, the sources of the delayed gamma rays may be divided into groups, with the groups of delayed gamma sources having decay time constants greater than 5×10−1 seconds and/or less than 5×105 seconds. In example embodiments, the sources of the delayed gamma rays may be divided into groups, with a subset of the groups of delayed gamma sources having decay time constants greater than 5×10−1 seconds and/or less than 5×105 seconds. In example embodiments, the sources of the delayed gamma rays may have decay time constants greater than 0.4 seconds, 0.5 seconds, 0.6 seconds, 0.7 seconds, 0.8 seconds, 0.9 seconds, 1 second, 1.1 seconds, 1.2 seconds, 1.3 seconds, or 1.4 seconds. In example embodiments, the sources of the delayed gamma rays may have decay time constants less than 1.5×106 seconds, 1.4×106 seconds, 1.3×106 seconds, 1.2×106 seconds, 1.1×106 seconds, 1×106 seconds, 9×105 seconds, 8×105 seconds, 7×105 seconds, 6×105 seconds, 5×105 seconds, or 4×105 seconds. In example embodiments, the sources of the delayed gamma rays may be divided into groups, with characteristic data for the groups available from one or more sources in, for example, tables and/or equivalent analytical representations. Such sources may include, for example, nuclear industry standards published by the American Nuclear Society. One such standard is the American National Standard “Decay Heat Power in Light Water Reactors”, ANSI/ANS-5.1-2005, incorporated by reference in the present application. In Section 3 of the ANS standard, Tables 9-12 provide αi and λi parameters (i=1, 2, . . . , 23) for exponential fits to fission functions f(t) and F(t,T). As known to a PHOSITA, fission function f(t) may represent decay heat power per fission following an instantaneous pulse of a significant number of fission events. As also known to a PHOSITA, fission function F(t,∞) may represent decay heat power from fission products produced at a constant rate over an infinitely long operating period without neutron absorption in the fission products. The fission functions may be defined by Equations (8), (9), and/or (10) below, with t in seconds, f(t) in MeV/fission-second, αi in MeV/fission-second, λi in seconds−1, F(t,T) in MeV/fission, F(t, ∞) in MeV/fission, and i=1, 2, . . . , 23.f(t)=Σ[αiexp(−λit)] (8)F(t,T)=Σ{(αi/λi)exp(−λit)[1−exp(−λiT)]} (9)F(t,∞)=F(t,1013) (10) Table 9 of the ANS standard provides αi and λi parameters for 235U thermal fission functions f(t) and F(t,∞). Table 10 of the ANS standard provides αi and λi parameters for 239Pu thermal fission functions f(t) and F(t,∞). Table 11 of the ANS standard provides αi and λi parameters for 238U fast fission functions f(t) and F(t,∞). Table 12 of the ANS standard provides αi and λi parameters for 241Pu thermal fission functions f(t) and F(t,∞). In example embodiments, a decay time constant τi for each group may be defined by Equation (11) below, with τi in seconds, λi in seconds−1, and i=1, 2, . . . , 23.τi=1/λi (11) As discussed below, decay time constants τi may be used to determine the groups of interest. In example embodiments, an amount MEVPFi of delayed gamma ray energy released by each group may be defined by Equation (12) below, with amount MEVPFi in MeV/fission, αi in MeV/fission-second, λi in seconds−1, and i=1, 2, . . . , 23.MEVPFi=αi/λi (12) In example embodiments, a total amount TMEVPF of delayed gamma ray energy released may be defined by Equation (13) below, with total amount TMEVPF in MeV/fission, amount MEVPFi in MeV/fission, and i=1, 2, . . . , 23.TMEVPF=Σ MEVPFi (13) In example embodiments, an uncompensated yield fraction UYFi may be defined by Equation (14) below, with uncompensated yield fraction UYFi having no units, amount MEVPFi in MeV/fission, total amount TMEVPF in MeV/fission, and i=1, 2, . . . , 23.UYFi=MEVPFi/TMEVPF (14) In example embodiments, a compensated yield fraction CYFi may be defined by Equation (15) below, with compensated yield fraction CYFi having no units, uncompensated yield fraction UYFi having no units, and i=1, 2, . . . , 23. FDG, having no units, may be defined by Equation (15) below.CYFi=UYFiFDG (15) In example embodiments, a value may be calculated that may express the fraction of gamma ray energy released in the fission process due to delayed gamma rays. The value may vary depending on the fissionable nuclide(s) and/or other actinide(s) considered. In example embodiments, three quantities may be used: (a) delayed gamma ray energy released in the fission process (QDG); (b) prompt gamma ray energy released in the fission process (QPG); and (c) capture gamma ray energy released in the fission process (QCG). Although some capture gamma ray energy released in the fission process is delayed, its effect is minor, so capture gamma ray energy released in the fission process (QCG) may be treated as a prompt effect. The fraction (FDG) of gamma ray energy released in the fission process due to delayed gamma rays may be calculated using Equation (16) below.FDG=QDG/(QDG+QPG+QCG) (16) As known to a PHOSITA, values for QDG may be found, for example, in the Evaluated Nuclear Data File (“ENDF”). The ENDF may be accessed online, for example, via the website of the National Nuclear Data Center of Brookhaven National Laboratory at http://www.nndc.bnl.gov/. The current online database version of the ENDF is ENDF/B-VII.0 (released Dec. 15, 2006). Clicking on “ENDF”, selecting “Basic Retrieval”, and using 235U as the target (entered, for example, as “235u”), brings a user to a page labeled “ENDF Data Selection” that includes fourteen entries, numbered 1-14, with each numbered entry having options such as Info, Summary, MAT, ENDF-6, Interpreted, σ, and/or Plot. Clicking on the Interpreted option for entry number 4 (“U-235(E_REL_FIS)U-235, INFO MT458”) brings a user to a page labeled “Interpreted ENDF File”, listing components of energy released in 235U fission. The listed value of QDG is 5.6000 MeV (235U). As also known to a PHOSITA, values for QPG may be found, for example, in the ENDF using a similar procedure. On the page labeled “Interpreted ENDF File”, the listed value of QPG is 6.6000 MeV (235U). Additionally, as known to a PHOSITA, values for QCG may be found, for example, at the website of the Atomic Mass Data Center (“AMDC”). The databases of the AMDC maybe accessed online, for example, via the website of the National Nuclear Data Center at http://www.nndc.bnl.gov/amdc/. Clicking on “Q-value Calculator”, using 235U as the target (entered, for example, as “235u”), a neutron as the projectile (entered, for example, as “n”), and a gamma ray as the ejectile (entered, for example, as “g”), brings a user to a page labeled “Reaction Q-values for 235U+n” with three columns of data, including the gamma ray Q-value. The listed value of QCG is 6.54545 MeV (235U). In example embodiments, using the values of QDG=5.6000 MeV, QPG=6.6000 MeV, and QCG=6.54545 MeV in Equation (16) yields FDG=0.298739 (235U). In example embodiments, values for QDG, QPG, and/or QCG may be obtained from other sources. For example, using older data with the values of QDG=6.2600 MeV, QPG=6.9600 MeV, and QCG=7.7500 MeV in Equation (16) yields FDG=0.298522 (235U). As discussed above, values for QDG may be found, for example, in the ENDF. Accessing the ENDF online, clicking on “ENDF”, selecting “Advanced Retrieval”, and using 239Pu as the target (entered, for example, as “239pu”) and a neutron as the projectile (entered, for example, as “n”), brings a user to a page labeled “ENDF Data Selection” that includes 130 entries, numbered 1-122 and also 1-8, with each numbered entry having options such as Info, Summary, MAT, ENDF-6, Interpreted, σ, and/or Plot. Clicking on the Interpreted option for entry number 4 (“PU-239(E_REL_FIS)PU-240, INFO MT458”) brings a user to a page labeled “Interpreted ENDF File”, listing components of energy released in 239Pu fission. The listed value of QDG is 5.1700 MeV (239Pu). As also known to a PHOSITA, values for QPG may be found, for example, in the ENDF using a similar procedure. On the page labeled “Interpreted ENDF File”, the listed value of QPG is 6.7410 MeV (239Pu). In example embodiments, accessing the databases of the AMDC online, clicking on “Q-value Calculator”, using 239Pu as the target (entered, for example, as “239pu”), a neutron as the projectile (entered, for example, as “n”), and a gamma ray as the ejectile (entered, for example, as “g”), brings a user to a page labeled “Reaction Q-values for 239Pu+n” with three columns of data, including the gamma ray Q-value. The listed value of QCG is 6.5342 MeV (239Pu). In example embodiments, using the values of QDG=5.1700 MeV, QPG=6.7410 MeV, and QCG=6.5432 MeV in Equation (16) yields FDG=0.280153 (239Pu). As discussed above, values for QDG may be found, for example, in the ENDF. Accessing the ENDF online, clicking on “ENDF”, selecting “Advanced Retrieval”, and using 238U as the target (entered, for example, as “238u”) and a neutron as the projectile (entered, for example, as “n”), brings a user to a page labeled “ENDF Data Selection” that includes 124 entries, numbered 1-116 and also 1-8, with each numbered entry having options such as Info, Summary, MAT, ENDF-6, Interpreted, σ, and/or Plot. Clicking on the Interpreted option for entry number 4 (“U-238(E_REL_FIS)U-239, INFO MT458”) brings a user to a page labeled “Interpreted ENDF File”, listing components of energy released in 238U fission. The listed value of QDG is 8.2500 MeV (238U). As also known to a PHOSITA, values for QPG may be found, for example, in the ENDF using a similar procedure. On the page labeled “Interpreted ENDF File”, the listed value of QPG is 6.6800 MeV (238U). In example embodiments, accessing the databases of the AMDC online, clicking on “Q-value Calculator”, using 238U as the target (entered, for example, as “238u”), a neutron as the projectile (entered, for example, as “n”), and a gamma ray as the ejectile (entered, for example, as “g”), brings a user to a page labeled “Reaction Q-values for 238U+n” with three columns of data, including the gamma ray Q-value. The listed value of QCG is 4.80638 MeV (238U). In example embodiments, using the values of QDG=8.2500 MeV, QPG=6.6800 MeV, and QCG=4.80638 MeV in Equation (16) yields FDG=0.418010 (238U). As discussed above, values for QDG may be found, for example, in the ENDF. Accessing the ENDF online, clicking on “ENDF”, selecting “Advanced Retrieval”, and using 241Pu as the target (entered, for example, as “241pu”) and a neutron as the projectile (entered, for example, as “n”), brings a user to a page labeled “ENDF Data Selection” that includes 71 entries, numbered 1-65 and also 1-6, with each numbered entry having options such as Info, Summary, MAT, ENDF-6, Interpreted, σ, and/or Plot. Clicking on the Interpreted option for entry number 4 (“PU-241(E_REL_FIS)PU-242, INFO MT458”) brings a user to a page labeled “Interpreted ENDF File”, listing components of energy released in 241Pu fission. The listed value of QDG is 6.4000 MeV (241Pu). As also known to a PHOSITA, values for QPG may be found, for example, in the ENDF using a similar procedure. On the page labeled “Interpreted ENDF File”, the listed value of QPG is 7.6400 MeV (241Pu). In example embodiments, accessing the databases of the AMDC online, clicking on “Q-value Calculator”, using 241Pu as the target (entered, for example, as “241pu”), a neutron as the projectile (entered, for example, as “n”), and a gamma ray as the ejectile (entered, for example, as “g”), brings a user to a page labeled “Reaction Q-values for 241Pu+n” with three columns of data, including the gamma ray Q-value. The listed value of QCG is 6.30972 MeV (241Pu). In example embodiments, using the values of QDG=6.4000 MeV, QPG=7.6400 MeV, and QCG=6.30972 MeV in Equation (16) yields FDG=0.314501 (241Pu). Additionally, as known to a PHOSITA, values for QDG, QPG, and/or QCG also may be found, for example, in the Japanese Evaluated Nuclear Data Library (“JENDL”), the Joint Evaluated File (“JEF”), and/or the files of the Joint Evaluated Fission and Fusion (“JEFF”) project. FIG. 10 is a table based on Table 9 of the ANS standard (235U), including values for group number (no units), αi (in MeV/fission-second), λi (in seconds−1), τi (in seconds), MEVPFi (in MeV/fission), UYFi (no units), and CYFi (no units). FIG. 10 uses a value for FDG of 0.298739. FIG. 11 also is a table based on Table 9 of the ANS standard (235U), including values for group number (no units), αi (in MeV/fission-second), λi (in seconds−1), τi (in seconds), MEVPFi (in MeV/fission), UYFi (no units), and CYFi (no units). FIG. 11 uses a value for FDG of 0.298522. FIG. 12 is a table based on Table 10 of the ANS standard (239Pu), including values for group number (no units), αi (in MeV/fission-second), λi (in seconds−1), τi (in seconds), MEVPFi (in MeV/fission), UYFi (no units), and CYFi (no units). FIG. 12 uses a value for FDG of 0.280153. FIG. 13 is a table based on Table 11 of the ANS standard (238U), including values for group number (no units), αi (in MeV/fission-second), λi (in seconds−1), τi (in seconds), MEVPFi (in MeV/fission), UYFi (no units), and CYFi (no units). FIG. 13 uses a value for FDG of 0.418010. FIG. 14 is a table based on Table 12 of the ANS standard (241Pu), including values for group number (no units), αi (in MeV/fission-second), λi (in seconds−1), τi (in seconds), MEVPFi (in MeV/fission), UYFi (no units), and CYFi (no units). FIG. 14 uses a value for FDG of 0.314501. Tables 9-12 of the ANS standard divide the sources of the delayed gamma rays into 23 groups. As a result, FIGS. 10-14 do, as well. However, each of the groups generally has a different value for CYFi. Thus, some groups are more important than others. For example, Group 1 generally has a small value of CYFi. Similarly, Groups 20-23 generally have small values of CYFi. Therefore, in order for the gamma compensation process to be simple, automatic, real-time, and/or with reduced cost, groups with small values of CYFi may be ignored in the gamma compensation calculations. The higher numbered groups also have large values of τi. Thus, their contribution, typically small, also occurs over an extended time period. Therefore, in order for the gamma compensation process to be simple, automatic, real-time, and/or with reduced cost, groups with large values of τi may be ignored in the gamma compensation calculations. Applicants note that a typical refueling outage for a nuclear reactor is on the order of about 25 days. Assuming that represents 5 time constants (τi), then one time constant (τi) is about 5 days or about 4.32×105 seconds. Therefore, in order for the gamma compensation process to be simple, automatic, real-time, and/or with reduced cost, groups with have values of τi greater than 4.32×105 seconds may be ignored in the gamma compensation calculations. In example embodiments, the gamma compensation method may use thirteen groups, specifically Groups 2-14. In addition or in the alternative, the gamma compensation method may use groups of delayed gamma sources having decay time constants, for example, greater than 5×10−1 seconds and/or less than 5×105 seconds. This may account for approximately 94% of the effect of all delayed gamma sources, and much of the remaining 6% would not have an effect until after the refueling outage would be over. The compensation—using gamma thermometers—may allow calibration of the nuclear instruments to be performed when the associated nuclear reactor is not in steady-state operation, by removing the effect of the delayed gamma sources using Equations (17)-(19) below.Prompt Signal=Total Signal−Delayed Signal (17) The prompt signal, GTprompt(t), represents prompt gamma energy deposition in watts per gram. In Equation (17), t represents time in seconds. The total signal may be expressed using Equation (18) below.Total Signal={GT(t)/[(1,000S0)+(GT(t)S0α)]} (18) In Equation (18), t represents time in seconds, GT(t) represents a signal from a gamma thermometer in microvolts, S0 represents sensitivity of the gamma thermometer in millivolts/(watt/gram), and α represents an alpha factor of the gamma thermometer in millivolts−1. The delayed signal may be expressed using Equation (19) below.Delayed Signal=Σ{[αnGTprompt(t)]/[1+(t/τn)]} (19) In Equation (19), n represents a number associated with a delayed gamma group (n=1, 2, . . . , 13—recognizing that the 13 groups are Groups 2-14), αn represents a group fraction of the delayed gamma group, t represents time in seconds, GTprompt(t) represents prompt gamma energy deposition in watts per gram, and τn represents a time constant of the delayed gamma group. The prompt signal, GTprompt(t), for a given GT detector 924 may be converted to digital GT data D1 and then compared to digital LPRM data D2 for the purpose of calibrating a corresponding LPRM detector 920 and/or providing information to GT signal processing unit 932, GT power distribution measuring system 938, and/or process control computer 904. In addition or in the alternative, the prompt signals, GTprompt(t), for two or more GT detectors 924 in GT detector assembly 918 may converted to corresponding digital GT data D1 and combined to determine a power distribution (e.g., an axial power distribution) for core 906. Values from such a power distribution may be compared to digital LPRM data D2 for the purpose of calibrating one or more LPRM detectors 920 and/or providing information to GT signal processing unit 932, GT power distribution measuring system 938, and/or process control computer 904. In example embodiments, initial values for sensitivity S0 and/or alpha factor α may be calculated when the GT is manufactured and calibrated. These initial values may be determined, for example, as a best fit to data using Equation (20) below, where U (in mV) may represent a measured signal from the GT thermocouple and/or W (in W/g) may represent sensor heating applied by a current source used for calibration.U=S0(0)W+α[S0(0)*W]2 (20) While example embodiments have been particularly shown and described, it will be understood by a PHOSITA that various changes in form and details may be made in the example embodiments without departing from the spirit and scope of the present invention as defined by the following claims.
	description	The present invention relates to an electron beam irradiation device and more particularly to an electron beam irradiation device for improving use of inert gas more efficient. There is known an electron beam irradiation device for irradiating an electron beam to a belt-shaped irradiated object and conducting a processing such as bridging, hardening or reforming to the irradiated object. As an irradiated object, for example, a resin film itself or a resin film coated with an electron beam curing resin coating is representative. However, in general, the reaction (processing) such as bridging of molecule induced by an electron beam is inhibited by oxygen existing in the atmosphere. For preventing the inhibition, for example, following methods are employed. In an electron beam irradiation device described in the patent publication 1 an irradiated object is a film coated by an electron beam curing resin coating material. When the coating material coated on the film is bridged or cured by the electron beam, the coated film is brought into contact with a metal dram rotating at a circumferential speed synchronizing with the traveling speed of the film with a coating material being sandwiched therebetween, and in this state, the electron beam is irradiated from the film side. The electron beam irradiation device is of the type in which the electron beam curing resin coating material is blocked from oxygen existing in the atmosphere by making it contact the metal drum, and then the inhibition of curing (process for the irradiated object by electron beam) is prevented. Hereinafter such type is referred to as “type A”. In the electron beam irradiation device of the type A, the electron beam is transmitted and penetrates all layers of the irradiated object and then reaches the layer (coating material) which need be processed by the electron beam. Therefore, a layer existing on the way of the beam, even though its do not need to be processed by the electron beam, is affected by the electron beam and undesirable reaction (such as yellowing or strength degradation) occurs. Part of the energy is absorbed in the layer on the way, thus the energy of the electron beam reaching the layer (coating material) which really need to be processed is wasted. The electron beam irradiation device needs a metal drum and a rotation drive mechanism thereof. Therefore, the device becomes heavy, thick, long and large more than required. Further, in a processing by the electron beam irradiation, especially in a curing process of coating material, a surface luster of the coating material is inevitably controlled by a surface luster of the metal drum. As an electron beam irradiation device of the type which does not have such defects, following devices are known. An electron beam irradiation device, described the patent application 2, the patent application 3, or the patent application 4 is of the type in which an electron beam is irradiated to an irradiated object in an irradiation chamber consisting of a shut space where an inert gas such as nitrogen is supplied, and is filled with the space. Hereinafter such type is referred to as “type B”. Above irradiation chamber has a feed-in opening for feeding a belt-shaped irradiated object into the irradiation chamber and a feed-out opening for feeding the belt-shaped irradiated object out of the irradiation chamber. At the upstream (the upstream of the feeding direction of the irradiated object) of the feed-in opening in the irradiation chamber, a duct and a cavity for catching an X-ray of a bremsstrahlung are formed, and an air knife projecting as a nozzle toward the irradiated object for blowing an inert gas (nitrogen) in the cavity is provided. The air knife blocks oxygen in the air entering accompanied the irradiated object from the outside, and dilutes the oxygen which cannot be blocked. That is to say, the type B prevents the inhibition of oxygen which may occur in the processing of the irradiated object by electron beam by dipping the irradiated object within an inert gas such as nitrogen which does not inhibit a process reaction by electron beam. Patent Publication 1: JP-B-H05-36212 Patent Publication 2: JP-B-S63-8440 Patent Publication 3: JP-A-H05-60899 Patent Publication 4: J-U-H06-80200 The type B prevents the electron beam irradiation device from becoming heavy and big. Further, the type B, especially when the processing of the irradiated object by electron beam is the curing of coating material, has another advantage that the processing surface (coated surface) does not controlled by a luster of others. On the other hand, during the electron beam is irradiating while the belt-shaped irradiated object is traveling, oxygen accompanying the irradiated object is continuously flowing into the irradiation chamber from the outside. Therefore, for continuously keeping an oxygen concentration at adequately low level, it is necessary to supply a large quantity of inert gas continuously, and as a result, the cost thereon also becomes high. In particular, if a processing speed (traveling speed) of the irradiated object becomes high, quantity of inflow oxygen also increases along with the increase of the speed, so that the oxygen concentration in the irradiation chamber suddenly rises, and that it becomes impossible to prevent the inhibition occurring in the electron beam processing. An object of the present invention is to prevent an electron beam irradiation device from becoming heavy and big, and is to improve the electron beam irradiation device of the type B having an advantage that a processing face does not controlled by the luster in the case of the curing of coating especially in a curing processing, thereby restraining an increase of the oxygen concentration in the irradiation chamber and reducing a consumption of the inert gas even though the traveling speed of the belt-shaped irradiated object becomes high. To solve the above problems, (D) An electron beam irradiation device for irradiating an electron beam to a belt-shaped irradiated object while making the irradiated object travel is, (E) the electron beam irradiation device comprising: (A) an electron beam generating section which generates the electron beam and emits the electron beam to an outside from a transmission window part; (B) an irradiation chamber adjacent to the transmission window part of the electron beam generating section, having partitions surrounding a periphery, a feed-in opening which opens on the partition to allow the belt-shaped irradiated object to be fed in, and a feed-out opening which opens on the partition to allow the belt-shaped irradiated object to be fed out, and formed as a closed space filled with inert gas, in which the electron beam emitted from the transmission window section is irradiated to the belt-shaped irradiated object fed in from an outside and travels the inside; and (C) an oxygen cutoff section adjacent to the irradiation chamber on an upstream side in an irradiated object traveling direction, having a feed-in opening for feeding in the belt-shaped irradiated object, and a feed-out opening for feeding out the belt-shaped irradiated object, and formed as a closed space, in which the belt-shaped irradiated object travels to be introduced to the irradiation chamber, the inert gas is blown to the irradiating surface side of the irradiated object, and oxygen in the air accompanying a vicinity of a surface of the irradiated object to flow in is shut off or diluted, wherein: (C1) the oxygen cutoff section surrounds the irradiated object with a surface side partition facing a side of the irradiating surface of the traveling belt-shaped irradiated object, a backface side partition facing to a side opposite to the irradiating surface of the irradiated object, and a pair of sideface side partitions facing both sideface sides of the irradiated object, (C2) a gap Ws between the surface side partition and the backface side partition of the oxygen cutoff section, and a gap We between the surface side partition and the backface side partition of the irradiation chamber and across the belt-shaped irradiated object in the irradiation chamber satisfy an inequality Ws<We, (C3) the gap Ws between the surface side partition and the backface side partition of the oxygen cutoff section is made uniform or almost uniform throughout an entire area of the oxygen cutoff section and, (C4) a blowing slit for the inert gas is provided on the surface side partition of the oxygen cutoff section, with a blowing opening thereof being not projected form or caved in the surface side partition of the oxygen cutoff section. Having such a configuration, firstly it is possible to prevent the electron beam irradiation device from becoming heavy and big because a metal drum is unnecessary in this system, and especially when the processing is a curing of a coating material, the processing surface is not controlled by a luster of others. Moreover, by the oxygen cutoff section which is a characteristic configuration of the present invention, even though the traveling speed of the belt-shaped irradiated object becomes high, an increasing in an oxygen concentration in the irradiation chamber can be restrained, and consumption of the inert gas can be reduced. Therefore, the use of the inert gas becomes effectively. In one embodiment of the present invention, a coating part for coating a liquid electron beam curing resin in a non-curing state on the surface of the irradiated object on the upstream side in the irradiated object traveling direction in the oxygen cutoff section may be provided. Having such a configuration, coating film formation of the electron beam curing resin and processing of the coating film by the electron beam are effectively conducted in line. In one embodiment of the present invention, the gap Ws between the surface side partition and the backface side partition of the oxygen cutoff section may be set to be wider than a thickness of the irradiated object by a range of 1-20 mm. By setting in this range, even if the traveling speed of the irradiated object increases up to about 200 m/min., the oxygen concentration in the irradiation chamber can be restrained equal to or less than 100 ppm. In one embodiment of the present invention, the slit may be formed so that a blowing direction of the inert gas from the slit inclines toward the upstream side in the traveling direction relative to a direction perpendicular to the traveling direction of the irradiated object. By inclining the slit in this way, the inert gas blown from the slit collides against the entering air accompanying the irradiated object like a knife edge, and the accompanying air is striped off from the irradiated object effectively, then the air can be pushed out from the feed-in opening of the oxygen cutoff section. In one embodiment of the present invention, on a downstream side relative to the slit in the traveling direction of the irradiated object, a gas supplying hole for supplying the inert gas for the irradiated object from the same side as the slit may be provided. According to this embodiment, the air accompanying the irradiated object is striped off by the inert gas blowing from the slit to restrict the entering of the accompanying air to the irradiation chamber, while the irradiated object can be supported by a supporting layer formed by the inert gas which is supplied from the gas supplying hole. Accordingly, the flapping of the irradiated object caused by a variation of pressure balance between the front and back of the irradiated object, which is involved by the blowing of the inert gas from the slit, is restrained, while the irradiated object is allowed to travel in the oxygen cutoff section smoothly. In a configuration provided with the gas supplying hole, a throttle valve for reducing a flow velocity of the inert gas blowing out from the gas supplying hole lower than a flow velocity of the inert gas blowing from the slit may be comprised. By providing such throttle valve, it is possible to blow the inert gas from the slit at a high speed to thereby drain the accompanying air adequately, while to supply the inert gas of the amount necessary for supporting the irradiated object from the gas supplying hole to thereby restrain the flapping of the irradiated object adequately. In a configuration provided with the gas supplying hole, the gas supplying hole may be formed as a through hole extending in a direction perpendicular to the traveling direction of the irradiated object. By forming the gas supplying hole as a through-hole in such a way, the inert gas supplied from the gas supplying hole is allowed to stay around the gas supplying hole relatively for a long time, and the supporting layer of the irradiated object by the inert gas can be formed effectively. Further, by setting a diameter of the gas supplying hole grater than the gap of the slit, the flow velocity of the inert gas supplied from the gas supplying hole can be restrained relatively easy. (1) According to the electron beam irradiation device of the present invention, firstly, it is possible to prevent the electron beam irradiation device from becoming heavy and big, and the processing surface is not controlled by the luster of others when the curing process of the coating material is conducted, so that any luster surface can be allowed. Moreover, when the traveling speed of the belt-shaped irradiated object becomes high, an increase of the oxygen concentration in the irradiation chamber is restrained, and a consumption of the inert gas can be reduced. Therefore, the use of inert gas becomes effectively. (2) Further, in a case that the coating part is provided on the upstream side of the oxygen cutoff section, coating film formation of the electron beam curing resin and an electron beam processing of the coating film can effectively be conducted in-line. C Cooler D Drying-Machine E Electron Beam E Irradiation Chamber Ea Irradiation Chamber Moving Side Eb Irradiation Chamber Fixing Side E1 Feed-in Opening of Irradiation Chamber E2 Feed-out Opening of Irradiation Chamber E3 Surface Side Partition E4 Backface Side Partition E5 Transmission Window Part F Irradiated Object Lc Feeding Roller Ln Conveying Roller M Moving Means Mw Truckle M1 Rail N Inert Gas P Conduit P1 Gathering Part P2 Gathering Part P3 Distribution Pipe P4 Distribution Pipe P5 Junction Part P6 Main Pipe P7 Valve P8 Valve P9 Valve P10 Valve R Electron Beam Generating Section Ra Wind-off Roll Rr Wind-up Roll SA Oxygen Cutoff Section Moving Side SB Oxygen Cutoff Section Fixing Side S1 Feed-in Opening of Oxygen Cutoff Section S2 Feed-out Opening of Oxygen Cutoff Section S3 Surface Side Partition S4 Backface Side Partition S5 Blowing Slit S6 Space S7 Gas Supplying Hole S8 Space T Coating Part T1 Plate Cylinder T2 Ink Pan T3 Doctor Blade T4 Impression Cylinder V Traveling Direction Ws Gap Between Partitions in Oxygen Cutoff Section We Gap Between Partitions in Irradiation Chamber In the followings, the best mode for carrying out the present invention will be described with reference to the drawings. [Brief Description of the Drawings] First, FIG. 1 is an explanatory view showing a fundamental embodiment (with no coating part) of the electron beam irradiation device of the present invention in conceptual partly sectional view. FIG. 2 is an enlarged sectional view showing an embodiment of the oxygen cutoff section S which is characteristic part of the present invention. FIG. 3 is an explanatory view showing an embodiment in which the oxygen cutoff section S and the irradiation section E can be divided into two pieces each. That is to say, FIG. 3 is the explanatory view showing an embodiment in which the oxygen cutoff section S is provided with an oxygen cutoff section moving side SA and an oxygen cutoff section fixing side SB, both of which can be engaged mutually, divided horizontally and separated from each other, and in which the irradiation section E is provided with an irradiation section moving side EA and an irradiation section fixing side EB, both of which can be engaged mutually divided horizontally and separated from each other. FIG. 4 is an explanatory view showing an embodiment also having a coating part on the upstream side of the oxygen cutoff section S. The electron beam irradiation device of the present invention is not limited by the drawings without departing from the scope of the present invention. [Summary of Entire Device] A summary of the entire device will be explained with reference to a fundamental embodiment of the irradiation device of the present invention illustrating in FIG. 1. As illustrated in FIG. 1, the electron beam irradiation device of the present invention comprises an electron beam generating section R generating an electron beam e, an irradiation chamber E for irradiating electron beam to a traveling belt-shaped irradiated object F, and an oxygen cutoff section S disposed next to and on the upstream side of the irradiation chamber E. In the figure, the belt-shaped irradiated object F is wound off from a wind-off roll Ra, guided by feeding rollers Lc, enters in the electron beam irradiation device from the feed-in opening S1 of the oxygen cutoff section S. Then, the object F is irradiated with the electron beam e during traveling in the irradiation chamber E, exits from the out side of the device from a feed-out opening E2 of the irradiation chamber, guided by a conveying rollers Ln, and wound up by wind-up rolls Rr. The oxygen cutoff section S is provided adjacent on the upstream side of the irradiation chamber E as shown in the sectional view of FIG. 2. In the present invention, the words “an upstream” and “a downstream” are on the basis of a traveling direction V of the belt-shaped irradiated object F. Seeing from the electron beam irradiation device, the direction to the supplying source of the irradiated object F, that is to say, the direction to the wind-off roll Ra is referred to as “an upstream”. On the hand, seeing from the electron beam irradiation device, the direction from which the irradiated object F is supplying, that is to say, the direction to the wind-up roll Rr is referred to “a downstream”. In such an electron beam irradiation device, characteristic configurations of the present invention are that a gap Ws between a surface side partition and a backface side partition across the irradiated object F in the oxygen cutoff section S and a gap We between a surface side partition and a backface side partition across the irradiated object in the irradiation chamber E satisfy an inequality Ws<We, the gap Ws is made uniform or almost uniform throughout the entire area of the oxygen cutoff section, and a blowing slit S5 for blowing inert gas is provided in the surface side partition with not projecting from and not caving in the partition. An inside of the chamber is maintained in the condition that oxygen concentration is low by introducing the inert gas into the irradiation chamber E from conduits P. The electron beam e generated in the electron beam generating section R transmits through a transmission window part E5, and the electron beam is irradiated to the irradiated object F. A cooler C (electron beam acquisition device) is provided on the backside of the irradiated object where the electron beam is irradiated. The inert gas N which is used in the oxygen cutoff section and the irradiation chamber is, for example, rare gas such as argon, helium, neon, or nitrogen, however, the nitrogen is usually used mainly because of the cost. As for the irradiated object F, as far as it is a belt-shaped thin film or sheet, any object can be used. As for the thickness, the irradiated object F having a thickness of about 5-300 μm is usually intended. As for a concrete electron beam processing, for example, there is a processing for conducing bridging (reaction) of molecule by an electron beam irradiation on the irradiated object of a resin film itself such as polyethylene film as an irradiated object. In addition, for example, there is a processing for conducting a bridging or curing the coating material contained on the irradiated object by electron beam irradiation, wherein the irradiated object is a film made of resin of polyester or film-like material such as paper or metallic foil coated by an electron beam curing resin coating material consisted of monomer of acrylate or prepolymer. [Oxygen Cutoff Section] Next, the configuration of the oxygen cutoff section S which is a characteristic part of the present invention will be described in detail, with reference to FIG. 2 showing an embodiment of the configuration. The oxygen cutoff section S is formed as closed space surrounded by partitions (except feed-in part and the feed-out part of the irradiated object F). These partitions comprise a surface side partition S3 facing toward the irradiating side of the traveling belt-shaped irradiated object F, a backface side partition S4 facing toward the opposing side of the irradiating side of the irradiation surface of the irradiated object, and a pair of sideface side partitions facing toward to the both sides of the irradiated object (not shown). Metal such as an iron on aluminum is usually used for material of these partitions. The oxygen cutoff section S also has a feed-in opening S1 for feeding the irradiated object F into the oxygen cutoff section S and a feed-out opening S2 for feeding it out from the oxygen cutoff section S. Moreover, the surface side partition S3 of the oxygen cutoff section S is provided with one or more blowing slits S5 for blowing inert gas in to the oxygen cutoff section. In the present invention, a gap Ws between the surface side partition S3 and the backface side partition S4 of the oxygen cutoff section S, and a gap We between the surface side partition E3 and the backface side partition E4 of the irradiation chamber and across the belt-shaped irradiated object in the irradiation chamber described later satisfy an inequality Ws<We. Accordingly, first, an air existing outside of the feed-in opening S1 is blocked by the partitions when entering in the feed-in opening S1 of the oxygen cutoff section S. Subsequently, because the gap Ws is narrow, the fluid resistance becomes high against a high oxygen concentration air which adhering to front and back surfaces of the irradiated object F by a viscous resistance and entering into the oxygen cutoff section S accompanying the object. Therefore, the accompanying air is stripped off from the irradiated object surface, and velocity of the accompanying air toward the irradiation chamber E is reduced. In addition, the inert gas N is continuously supplied to the oxygen cutoff section S from the blowing slits S5 for blowing the inert gas provided on surface side partition S3. Therefore, oxygen in the oxygen cutoff section S is diluted (decreased in concentration). Further, the oxygen in the upper streams of the oxygen cutoff section S is dragged and forced out by the inert gas flowing out from the feed-in opening S1. Moreover, the gap Ws is made uniform or almost uniform throughout the entire area of the oxygen cutoff sections in the traveling direction of the irradiated object. The less the gap Ws is, the more preferable because the rising of the oxygen concentration in the irradiation chamber caused by an inflow of the oxygen in the air is prevented. However, if the gap Ws becomes too narrow, there is a possibility of raising the inconvenience that the traveling irradiated object tends to touch the partitions. Therefore, taking both into consideration, the appropriate width is decided. Usually, the width of the gap Ws is greater than the thickness of the irradiated object by the extent of 1-20 mm. With in this range, even if the traveling speed of the irradiated object is increased around 200 m/min, the oxygen concentration in the irradiation chamber E can be restrained less than 100 ppm. Moreover, on the surface side partition S3 of the oxygen cutoff section S, one of more blowing slits S5 for blowing inert gas to the oxygen cutoff section are provided. As shown in FIG. 2, each blowing slit S5 is formed with not projecting from and not caving the surface side partition S3, more in detail, the inside surface of the partition S3. That is to say, the inside surface of the surface side partition S3 on the side of irradiated object F, which includes the part of the blowing slit S5, is formed in generally flat surface on which concavity and convexity can be substantially ignored thereover. However, other than complete flat surface as shown in the figure, a smoothly curvature surface is also admitted. In the case, traveling path of the fed belt-shaped irradiated object has also the same or almost the same curvature surface as the partition. As described above, as well as the gap Ws in the oxygen cutoff section S being narrow, the gap Ws is made uniform or almost uniform throughout the entire area of the oxygen cutoff section S. Further as the blowing slit S5 is provided with not projecting from and not caving (almost flat) on the surface side partition S3, the inert gas blown to the oxygen cutoff section S does not circulate or stagnate, then separation of the accompanying air layer, dilution of oxygen, and pushing out the air to the upper stream or the like is conducted smoothly. Therefore quantity of oxygen flowing into the irradiation chamber E from the oxygen cutoff section S is excessively reduced. Further, from the aspect of quantity of inert gas used, the gap Ws between the surface side partition and the backface side partition of the oxygen cutoff section S is set small of narrow, and the gap Ws is made uniform or almost uniform throughout the entire area of the oxygen cutoff section S, so that the internal volume of the oxygen cutoff section S is kept in necessary minimum. Therefore quantity of inert gas to be supplied to the oxygen cutoff section S is kept in necessary minimum. Consequently, quantity of the inert gas use to make the oxygen concentration low can be saved. In addition, in view point of stopping an oxygen flow into the air, the blowing slit S5 for blowing inert gas is preferably provided on the upper streams in the oxygen cutoff section S. The conduits P are connected to the blowing slits S5, and via the conduits P, inert gas N is supplied. Further, in the embodiment of FIG. 2, for buffering the fluctuation of quantity of spout and blowing pressure of the inert gas, spaces S6 are provided in behind of the blowing slits S5. Therefore, the inert gas N from conduits P is supplied to the slits S5 via the spaces s6. In addition, each blowing slit S5 is provided at least on the processing surface side of the electron beam irradiation of irradiated object F. Usually, the electron beam irradiation side becomes the processing surface, thus in the configuration such as shown in FIG. 2, the blowing slit S5 can be provided on the surface side partition S3. However, the blowing slit S5 can be provided on both sides of the processing surface of the electron beam irradiation and the opposite side. [Electron Beam Generating Section] An electron beam generating section R generates electron beam and emits the electron beam to outside from transmission window part E5, and an existing electron beam generator can appropriately be employed as it. Such an electron beam generator is available from NHV Corporation Co., Ltd., or Energy Science Company (ESI Company) in USA, for example. [Irradiation Chamber] The irradiation chamber E, as shown in FIG. 1, is adjacent to the transmission window part E5 of the electron beam generating section R, and constructs a closed space (excepting feed-in/feed-out parts of the irradiated object) which is surrounded by partitions in periphery. By filling the irradiation chamber E with inert gas N to keep oxygen concentration low (equal to or less than about 300 ppm normally), and in such a low oxygen concentration atmosphere, by irradiating the electron beam e on the irradiated object F, the electron beam processing such as bridging, polymerization, decomposition or curing is conducted. The partitions of the irradiation chamber E are usual made by metal such as ferrum or aluminum. Parts especially required to be cut off from X-rays of bremsstrahlung are formed with enough thickness using metal having a high X-ray shielding capability, such as plumbum. Furthermore, the irradiation chamber E connects to the oxygen cutoff section S provided on up side thereof. The partition of the oxygen cutoff section S on the side of the irradiation chamber E is provided with a feed-in opening E1 for feeding in the irradiated object F. The downstream in the irradiation chamber E is provided with a feed-out opening E2 for feeding out the irradiated object F. The belt-shaped irradiated object F travels between the feed-in opening E1 and the feed-out opening E2. In addition, for aiding the traveling of the irradiated object F, a feeding roller Lc is optionally provided in the irradiation chamber. In the embodiment of FIGS. 1 and 2, the feed-in opening E1 of the irradiation chamber E and the feed-out opening S2 of the oxygen cutoff section S are identical to each other on dual purposed. For keeping the oxygen concentration in the irradiation chamber E low, the inert gas N is supplied via a conduits P to the irradiation chamber E, and the chamber is filled up with the gas. In addition, on the opposite side of the electron beam generating section R of the irradiated object F, there is provided a cooler (an electron beam capture device) C for catching the electron beam transmitted through the irradiated object F and for cooling heat occurring when the transmitted beam is caught. As described above, the gap We between both partitions across the irradiated object F in the irradiation chamber E, is made greater or wider than the gap Ws between the surface side partition S3 and the backface side partition S4 of the oxygen cutoff section S. The oxygen which could not be removed completely in the oxygen cutoff section S may enter into the irradiation chamber E accompanying the traveling irradiated object F. Although the quantity thereof is low, if it is integrated for a long time, the increase of the oxygen concentration becomes impossible to ignore. Thus, it is necessary for supplying the inert gas continuously to the irradiation chamber E via conduits P, and for making a volume big to some extent to dilute the flowing-in oxygen and to desensitize to density increase. Therefore, setting the gap We slightly greater while satisfying We>Ws. In this way, by making the volume of the irradiation chamber E greater than that of oxygen cutoff section S while satisfying We>Ws, the oxygen flowing to the irradiation chamber E from the oxygen cutoff section S can be largely diluted. Further, by lowering density of the oxygen in the oxygen cutoff section S and in the irradiation chamber E, it becomes possible to keep the oxygen concentration in the irradiation chamber low. Therefore, when traveling speed of irradiated object F is high, the oxygen concentration hardly increases. Furthermore, in view of quantity of usage of the inert gas, by providing the oxygen cutoff section S on upstream part, when the accompanying air around the irradiated object enters in the irradiation chamber E, the oxygen concentration of the irradiation chamber E has already been reduced. Consequently, a little quantity of the inert gas to be supplied to the irradiation chamber is enough. In the oxygen cutoff section S described above, by setting the gap Ws between the surface side partition and the backface side partition small or narrow, and by making the gap Ws be uniform or almost uniform throughout the entire area of the oxygen cutoff section, a size of the internal volume of the oxygen cutoff section S is necessary minimum. Therefore, quantity of the inert gas to be supplied to the oxygen cutoff section S becomes necessary minimum. Thus, quantity of usage of the inert gas for reducing the oxygen concentration can be reduced. [Dividable Construction] Not explicitly illustrated in FIGS. 1 and 2, however, in order to facilitate a “paper passing” for passing the irradiated object through the electron beam irradiation device and such as maintenance of the device, the electron beam irradiation device employs a structure capable of being divided, with a traveling face of the irradiated object traveling in the device or the vicinity thereof serving as a dividing face. Of course, if there are no obstacles for the paper passing and for maintenance, the dividing structure is not required. FIG. 3 is one example of the dividable structure employed in the electron beam irradiation device of the present invention. It is an example of the structure in which the irradiated object traveling face in the electron beam irradiation device is vertical or substantially vertical and which the device can be divided horizontally in two. The dividable structure shown in FIG. 3 shows one embodiment of the configuration, in which the oxygen cutoff section S thereof is divided in two of an oxygen cutoff section moving side SA and an oxygen cutoff section fixing side SB, and both of which are engaged mutually, and of an irradiation section E is also divided in two of an irradiation section moving side EA and an irradiation section fixing side EB, both of which can be engaged mutually. The oxygen cutoff section moving side SA and the irradiation section moving side EA are movable horizontally, and the oxygen cutoff section fixing side SB and the irradiation section fixing side EB are fixed. By providing seal means such as a packing on the engaging faces of each moving side of the oxygen cutoff section moving side SA and the irrigation section moving side EA, and each fixed side of the oxygen cutoff section fixing side SB and the irradiation section fixing side EB, the irradiation chamber E and the oxygen cutoff section S are sealed and shut off from the outside when they are engaged. When the operation of the electron beam irradiation device is stopped, and maintenance, checking, cleaning or the like of the inside is conducted, both of moving sides of the oxygen cutoff section moving side SA and the irradiation section moving side EA and fixing sides of the oxygen cutoff section fixing side SB and the irradiation section fixing side EB are divided. FIG. 3 illustrates the divided state. The oxygen cutoff section moving side SA and the irradiation section moving side EA of the moving side are approachable to and dividable from the oxygen cutoff section fixing side SB and the irradiation section fixing side EB which are fixed on floor by displacement means M. As a moving mechanism M, it is possible to use a mechanism having a rail M1 provided on the floor and truckles Mw, and a drive mechanism (not illustrated) such as a hydraulic cylinder and a piston may be provided, if necessary. In FIG. 3, the side to which the electron beam generating section R is attached is the fixed sides SB and EB, however, the side to which the electron beam generating section R may be the moving sides. Next, referring to FIG. 4, another embodiment according to the electron beam irradiation device of the present invention will be explained. FIG. 4 shows an explanatory view which illustrates another embodiment of the electron beam irradiation device, in which a coating part T is further provided to the electron beam irradiation device of the embodiment illustrated in FIG. 1. The electron beam irradiation device shown in FIG. 4 has the coating part T between the oxygen cutoff section S and the wind-off roll Ra of the electron beam irradiation device of FIG. 1 along with the irradiated object F. The coating part T may appropriately employ a known coating means. In the illustrated example, the coating part T is a known photogravure coater, comprising an ink pan T2 in which liquid ink consisting of electron beam curing resin is filled, a plate cylinder T1 consisting of a graver printing plate rotating with a bottom half dipping into the coating material in the ink pan T2, a doctor blade T3 for scraping off surplus coating material on the surface of the plate cylinder T1, and an impression cylinder T4 for transferring the coating material filled in a minute cell on the surface of plate cylinder T1 to the surface of the irradiated object F by pressurizing the irradiated object F from the opposite side of the plate cylinder T1. As a coating part, a roll coater, curtain flow coater, comma coater or the like may be used other than the illustrated gravure coater, Furthermore, in the illustrated embodiment, a drying-machine D is provided between the coating part T and the oxygen cutoff section S along with the irradiated object F. The drying-machine D is used for drying and removing dilution solvent when the solvent is included in the coating material. If the solvent is not included in the coating material, the drying-machine D may be omitted. As a drying-machine D, a known system on structure such as hot blast blowing or infrared radiation can be used. Next, referring to FIGS. 5 to 7, still another embodiment of the oxygen cutoff section S will be descried. The same reference numeral is denoted to the part which is common to the above described embodiment shown in FIGS. 1 to 4, and differences will be explained mainly. As shown in FIG. 5, in this embodiment, a slit S5 is provided on the upstream of the oxygen cutoff section S, and plural gas supplying holes S7 are provided on the downstream of the slit S5. The slit S5 is formed so that the blowing direction of the inert gas N inclines toward the upstream of the traveling direction V relative to the direction perpendicular to the traveling direction V of the irradiated object F. In other words, the blowing angle in FIG. 5 is an acute angle, for example it is set at 60°, for example. Accordingly, the inert gas blowing from the slit 5 to the irradiated object F acts on the irradiated object F so as to apply a knife edge, so that the effect of stripping off accompanying air can be improved, thereby effectively restricting the entering of the accompanying air to the irradiation chamber E. In the same way as that of the embodiment of FIG. 2, the blowing opening of the slit S5 is provided on the surface side partition S3 with not projecting from and not caving in the partition and a space S6 for introducing the inert gas N from conduit P is provided behind the blowing slit S5. In this embodiment, as shown in FIG. 6, the slit S5 is provided so as to linearly extend in the width direction of the oxygen cutoff section S, that is to say, in the left and right direction of FIG. 6 over the length as same as that of the irradiated object F or more than that. The number of the slit S5 is not limited one, and plural number of the slits can be provided along the traveling direction of the irradiated object F. On the other hand, as shown in FIGS. 5 and 6, each gas supplying hole S7 has a circular blowing opening, and is formed as a through-hole extending in the direction perpendicular to the traveling direction of the irradiated object F. Gas supplying holes S7 are provided on the surface side partition S3 so as to supply the inert gas from the same side as the slit S5 to the irradiated object F. Gas supplying holes S7 are arranged in a staggered manner with regard to the width direction of the oxygen cutoff section S. The number, the arrangement and the size of gas supplying holes S7 may be decided in appropriately, however, in view of the reason described later, when the inert gas is supplied from the gas supplying holes S7, the knife edge effect for stripping off the accompanying air as occurred at the slit S5 needs not to be considered. Therefore, a cross-section of the gas supplying holes S7 may be a shape having no or less anisotropy such as a round shape, and the diameter d thereof may be grater than gap t (see FIG. 6) of the slit S5. Each opening of the gas supplying holes S7 on the surface side partition S3 are formed with not projecting from and not caving in the surface side partition S3. A space S8 in which the inert gas N is introduced from the conduit P is provided behind each of the gas supplying holes S7. FIG. 7 shows a pipe arrangement for the oxygen cutoff section S. For each space S6 and S8, plural conduits P are connected in a line at appropriate pitches along the width direction of the oxygen cutoff section S. Conduits P to the space S6 are gathered at a gathering part P1, conduits P to the space S8 are gathered at a gathering part P2. Gathering parts P1 and P2 are further merged at a junction part P5 through distribution pipes P3 and P4, and the junction part P5 is connected to a common gas source through a main pipe P6. The distribution pipes P3 and P4 are provided with throttle valves P7 and P8 for regulating a flow rate or a pressure of the inert gas, and similarly throttle valves P9 and P10 are also provided between the each of the gathering parts P2 and P3 and the conduits P. By providing the throttles valves P7 and P8, the flow velocity of the inert gas blown from slit S5 and the flow velocity of inert gas blowing from gas supplying holes S7 are adjustable independently from each other. Moreover, by adjusting valve opening of each throttle valve P9, unevenness of the flow velocity of the inert gas blown from the slit S5 may be restrained in the width direction of the oxygen cutoff section S. By adjusting valve opening of each throttle valve P10, in the width direction of the oxygen cutoff section S, unevenness of flow velocity of the inert gas blown from each gas supplying hole S7 may be restrained. In the above described embodiment, the accompanying air is stripped off and forced out from the feed-in opening S1 by the inert gas blowing from the slit S5 of the oxygen cutoff section S, while a flapping of the irradiated object F is restrained by the pressure of the inert gas supplying from the gas supplying holes S7. Consequently, the incursion of the oxygen is further restrained effectively. That is to say, when the inert gas is blown at high speed from the slim hole such as a slit S5, a pressure balance is destroyed between the front and the back of the film-shaped irradiated object F, and the irradiated object F is drawn to the surface side partition S3. Because tension is acting on the irradiated object F along the traveling direction, if the irradiated object F is drawn to the surface side partition S3, the force for returning the object F is generated. By the force being act on alternately, the irradiated object F may flap in direction of gap Ws. If the flapping occurs, there is a risk that quantity of oxygen passing through the oxygen cutoff section S and breaking into the irradiation chamber E increases. In particular, in this embodiment, the tendency is high because the gap Ws is small, and thus, the faster the velocity of irradiated object, the higher the tendency becomes. However, according to the embodiment of FIGS. 5 to 7, because a lot of gas supplying holes S7 are provided adjacent to the downstream of the slit S5, a support layer of the inert gas for the irradiated object F is formed by the inert gas supplied from these gas supplying holes S7. Consequently, the flapping of the irradiated object F about the direction of the gap Ws can be restrained by the support layer and the irradiated object F can travel linearly and smoothly. Then, the oxygen screening effect in the oxygen cutoff section S can be improved. The throttle valves P7 to P10 may be omitted or added appropriately as far as the flow velocity of the inert gas blowing from the gas supplying holes S7 can be controlled slower than a flow velocity of the inert gas blowing from the slit S5. If it is possible to blow the inert gas from both of the slit S5 and the gas supplying hole S7 using fixed throttle in a desired state, the throttle valve capable of adjusting the openings may be omitted. As far as the flapping of the irradiated object F is restrained, an appropriate more than one gas supplying holes S7 may be provided.
	abstract	A system for filling a container with hazardous waste includes a primary confinement chamber that houses a lid handling mechanism and a filling head. The lid handling mechanism may be used to remove and/or recouple the lid to the container as part of the process of filling the container in such a way to ensure the exterior of the container is not contaminated by the hazardous waste. The filling head may be configured to add the hazardous waste to the container, mix the contents of the container, and/or vent air from the container.
	abstract	A low-power nuclear reactor includes a housing and a reflector forming a reactor core. The core includes inner and outer primary tubes therein, arranged together as bayonet tubes and intended for circulating a coolant, and secondary tubes, accommodating elements of a control and protection system. The reactor further includes an intake chamber for coolant of a primary loop, and a discharge chamber for coolant of the primary loop, separated by a partition. The outer primary tubes are secured on the intake chamber's bottom, and the inner primary tubes are secured on the partition. Fuel assemblies are mounted in the inner primary tubes on suspensions, which are mounted on the discharge chamber's upper portion. The secondary tubes are sealed off from the intake and discharge chambers for the coolant of the primary loop, and an inter-tube space of the core is filled with a medium or material transparent to neutrons.
	summary
060318937	abstract	A stray radiation grid, particularly for a medical X-ray apparatus, is composed of a carrier material with absorption elements, particularly in the form of lead lamellae, that are arranged in rows spaced from one another and proceeding essentially parallel to one another, with the respective spacings between the successive rows of absorption elements being larger in the region of the edges of the grid than in the middle region.
	summary
060524243	summary	BACKGROUND OF THE INVENTION The present invention relates to a method of welding to fabricate double-wall structures composed of inner and outer wall and reinforcing ribs provided between the outer and inner walls. The invention also relates to a double-wall structure produced by the method. Double-wall structures that can be produced by the method include ship, airplane and car bodies, as well as bridge structures, various containers for use in industrial plants, and vacuum vessels. The present invention relates particularly to a method of welding a vacuum vessel composed of a double-wall structure reinforced with ribs between the outer and inner walls. The invention also relates to a vacuum vessel produced by this welding method. The invention further relates to a method of welding a double-walled vacuum vessel for a nuclear fusion device which consists of an inner wall to be exposed to a plasma and an outer wall that surrounds it, with the walls being reinforced with ribs and welded to each other. The invention also relates to a vacuum vessel for a nuclear fusion device that is produced by this welding method. An electron beam welding method is conventionally applied to fabricate double-wall structures such as ship, airplane and car bodies, as well as bridge structures and vacuum vesslels by welding the inner and outer walls together with reinforcing ribs. In the class of nuclear fusion devices called "tokamak", a plasma created within a vacuum vessel is heated and sufficiently maintained with a strong external magnetic field to initiate a fusion reaction. The plasma-confining vacuum vessel is required to be capable of sustaining a high vacuum and function as a primary barrier against radiations. It is also required to withstand the large electromagnetic force produced by plasma disruption. In addition, in order to secure plasma control characteristics and reduce the loss of magnetic flux that occurs when a plasma is brought to energy break-even conditions, the electrical resistance of the vacuum vessel as measured in the toroidal direction of the torus must be held higher than a certain value. These requirements can be met by a vacuum vessel of double-wall structure that consists of an inner wall to be exposed to a plasma and an outer wall that surrounds it and in which the inner and outer walls are joined with ribs to segment the vessel wall in compartments. If the reinforcing ribs are arranged in a poloidal direction, only a small effect is caused on the electrical resistance of the vacuum vessel in the toroidal direction. An example of this type of vacuum vessel for use in fusion devices is described in Japanese Patent Public Disclosure No. 731919/1990. The double-wall structure adopted by such vacuum vessels has the additional advantage of securing mechanical strength and rigidity. On the other hand, extensive use of welding is required to fabricate this double-wall structure. In addition, the welding of the outer wall to ribs, which is performed after inserting a shield between adjacent ribs, can only be effected from outside. Conventionally, the outer wall is externally joined to ribs by plug welding which is illustrated in FIG. 13. However, it is difficult to secure the desired weld strength by this method. If slot welding is substituted with a view to increasing the throughput, the distortion in welding is also increased and, what is more, the man-hour required is exorbitant. SUMMARY OF THE INVENTION The present invention has been accomplished under these circumstances and has as an object providing a method of welding a double-wall structure such that even if its size is increased, the fabrication efficiency is not compromised and the distortion in welding is sufficiently reduced to enable precise assembling of a structure that can reasonably withstand the great electromagnetic force caused by plasma disruption. Another object of the invention is to provide a double-wall structure that is produced by the method. A particular object of the invention is to provide a double-walled vacuum vessel by the method that is suitable for use in a fusion device. The first object of the invention can be attained by a piercing welding method for fabricating a double-wall structure consisting of an inner wall, an outer wall surrounding said inner wall and reinforcing ribs that connect said outer and inner walls, in which an electron beam is externally applied at right angles to the outer wall such that the applied electron beam penetrates the outer wall to reach the abutting rib, whereupon the outer wall is welded to the rib, characterized in that the welded structure of the outer wall and the rib is composed of at least two piercing weld beads that are spaced apart by an unwelded area, with the sum of the widths of the weld beads being at least 25% of the rib width and the length of the unwelded area exterior to the root of each bead being no more than 20% of plate thickness. The second object of the invention can be attained by a double-wall structure consisting of an inner wall, an outer wall surrounding said inner wall and reinforcing ribs that connect said outer and inner walls, said structure being produced by a piercing welding method in which an electron beam is externally applied at right angles to the outer wall such that the applied electron beam penetrates the outer wall to reach the abutting rib, whereupon the outer wall is welded to the rib, characterized in that the welded structure of the outer wall and the rib is composed of at least two piercing weld beads that are spaced apart by an unwelded area, with the sum of the widths of the weld beads being at least 25% of the rib width and the length of the unwelded area exterior to the root of each bead being no more than 20% of plate thickness. The particular object of the invention is attained by a double-walled vacuum vessel for a fusion device which is a torus-shaped plasma container consisting of an inner wall to be exposed to a plasma, an outer wall surrounding said inner wall and reinforcing ribs that connect said outer and inner walls, with shields being inserted between the two walls and the outer wall being combined with each rib to form a T shape, further characterized by being fabricated by a piercing welding method in which an electron beam is externally applied at right angles to the outer wall such that the applied electron beam penetrates the outer wall to reach the abutting rib, whereupon the outer wall is welded to the rib and that the welded structure of the outer wall and the rib is composed of at least two piercing weld beads that are spaced apart by an unwelded area, with the sum of the widths of the weld beads being at least 25% of the rib width and the length of the unwelded area exterior to the root of each bead being no more than 20% of plate thickness. In a preferred embodiment, wraparound welding is applied to the piercing welded end of each rib such that the distortion in welding is sufficiently reduced to enable precise assembling of a structure that can reasonably withstand the large electromagnetic force caused by plasma disruption.
	description	This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-10393 filed on Jan. 19, 2004, the entire contents of which are incorporated herein by reference. The present invention relates generally to a radiotherapy apparatus which treats a diseased part, such at a tumor by using a radiation ray, and relates to its multi-leaf collimator limiting a range of the radiation ray. A multi-leaf collimator of a radiotherapy apparatus includes groups of leaves, a main material of which is heavy metal, such as tungsten, and the leaves in each group are closely adjacent. Pairs of the groups of leaves are positioned in a radiation direction of a radiation ray. The groups of each pair move in close and opposite directions, mutually. A drive unit which moves each leaf in a conventional radiotherapy apparatus includes drive gears which contacts cogs formed in edges of leaves and are connected to a motor via shafts. The drive unit is described in Japanese Patent Disclosure (Kokai) No. 2002-253686, page 3 and FIG. 12, for example. Since it is required to move each leaf in the close and opposite directions according to a range of the radiation ray, namely a diseased part to be treated, a driving mechanism is provided with respect to each leaf A conventional multi-leaf collimator includes the groups, each of which has about 40 adjacent leaves with a thickness of about 3 mm. Although it is theoretically possible to approximate the radiation range to the medical treatment range by reducing thickness of the leaves and increasing number of leaves, it is actually difficult to reduce the thickness of the leaves due to the drive gears which move the leaves and the shafts which connects the drive gears and the motor. Moreover, it is also a problem that the drive unit increases in size and in weight. Furthermore, backlash could occur in such a gear mechanism, and accuracy of move control of the leaf is reduced. Therefore, when the radiation range is set, positions of the leaves are shifted, it is difficult to accurately set the radiation range, and it could be a problem that the radiation ray is radiated to a normal part of a patient. The above mentioned Japanese Patent Disclosure (Kokai) No. 2002-253686 discloses a gear mechanism which avoids the backlash, however the gear mechanism increases in size. One object of the present invention is to ameliorate the above-mentioned problems. According to one aspect of the present invention, there is provided a radiotherapy apparatus comprising a radiation source configured to radiate a radiation ray, a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray and a drive unit configured to move at least one of the leaves with an ultrasonic wave. According to another aspect of the present invention, there is provided a radiotherapy apparatus comprising a radiation source configured to radiate a radiation ray, a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray and means for moving at least one of the leaves with an ultrasonic wave. According to another aspect of the present invention, there is provided a method for controlling a radiotherapy apparatus comprising radiating a radiation ray, limiting a radiation range of the radiation ray with a plurality of leaves and moving at least one of the leaves with an ultrasonic wave. An embodiment of a radiotherapy apparatus is explained in detail with reference to FIGS. 1 to 9. The radiotherapy apparatus is mainly explained with reference to FIG. 1 which is a perspective view. The radiotherapy apparatus includes a radiation unit 10 which radiates a radiation ray from a radiation source to a patient, and a bed unit 20 on which the patient P is laid and a position of the radiation range is set. The radiation unit 10 includes a fixed gantry 11 which is fixed on a floor, a rotation gantry 12 which rotates and is supported by the fixed gantry 11, a radiation head 13 which is positioned on a top part of the rotation gantry 12, and a collimator 14 is included in the radiation head 13. The rotation gantry 12 can be rotated through about 360 degrees around a horizontal rotation center axis H of the fixed gantry 11, and the collimator 14 can be also rotated around radiation axis I. An intersection of the rotation center axis H and the radiation axis I is called as an isocentre IC. The rotation gantry 12 stops when a fixed radiation method is performed or rotates when several radiation methods, such as a rotation radiation method, a pendulum radiation method, or an intermittent radiation method is performed. The bed unit 20 is positioned on the floor and rotates within a predetermined angle range in a G-arrow direction along a circular arc around the isocentre IC. A top plate 22 on which the patient is laid is supported by an upper mechanism 21 of the bed unit 20. The upper mechanism 21 moves the top plate 22 in a forward and backward direction shown as Arrow e and in a right and left direction shown as Arrow f. The upper mechanism 21 is supported by a lift mechanism 23. The lift mechanism 23 includes a link mechanism, for example, when the link mechanism goes up and down in a direction shown as Arrow d, the upper mechanism 21 and the top plate 22 move in the up and down direction in a predetermined range. The lift mechanism 23 is supported by a lower mechanism 24. The lower mechanism 24 includes a rotation mechanism which rotates the lift mechanism 23 in a direction shown as Arrow F centering on a center at a distance L from the isocentre IC. That is, the upper mechanism 21 and the top plate 22 with the lift mechanism 23 can move in the direction shown as Arrow F in a predetermined range. A positioning of the patient P to be treated and a setting of the radiation range of the collimator 14 are performed a staff D, such as a doctor. When the radiation treatment is performed, it is desired that the radiation ray is radiated only to a diseased part, such as a tumor and that a normal tissue is not damaged. Therefore, in order to reduce the radiation ray radiated to the normal part, the collimator 14 which limits the radiation range is provided in the radiation head 13 as the collimator 14 can rotate around the radiation axis I. The collimator 14 is shown in FIGS. 2 to 4, and is explained in detail. FIGS. 2 and 3 are illustrations for explaining a first pair of the leaves and a second pair of groups of leaves and are perpendicular, mutually. FIG. 4 is a flat view indicating the second pair of leaves. The collimator 14 includes the first pair 140 of leaves mainly made of heavy metal, such as tungsten, and the second pair 141 of leaves, and the first and second pairs are arranged along a radiation direction of the radiation ray radiated from a radiation source S. As shown in FIGS. 2 and 3, the pairs 140 and 141 are divided into two groups 140A and 140B, and 141A and 141B, respectively. The first leaves 140A and 140B which are close to the radiation source S work as a single component, and move in a direction shown as Arrow X along an arc-shaped plane centering on the radiation source S. Each group is moved closer and farther, mutually, by first drive units I 42A and 1 42B which transfer mechanical powers to the leaves from the motor via the gear mechanisms. The second groups 141A and 141B of leaves which is far from the radiation source S, as shown in FIG. 3, mutually move closer and farther, in a direction shown as Arrow Y which is along an arc-shaped plane centering on the radiation source S and which is perpendicular to the direction of the movement of the first leaves 140A and 140B. The second groups 141A and 141B of leaves, as shown in FIG. 2 and FIG. 4, includes a plurality of leaves 141A1 to 141An and 141B1 to 141Bn, and the leaves 141A1 to 141An and 141B1 to 141Bn are adjacent, respectively. The leaves 141A1 to 141An and 141B1 to 141Bn are mainly made of heavy metal. The leaves 141A1 to l4lAn and 141B1 to l4lBn of the second groups 141A and 141B are moved in the arc-shaped plane by second drive units. The second drive units include stators STA1 to STAn and STB1 to STBn which are attached to edges of the leaves, signal lines LA1 to LAn and LB1 to LBn connected with the stators and a high-voltage generation units GA1 to GAn and GB1 to GBn which supply high-voltage to the stators via the signal lines. In this embodiment, an operation of the second drive units and 113B1 to 113Bn which move the leaves 141A1 to 141An and 141B1 to 141Bn of the second groups 141A and 141B is different from an operation of the first drive units 142A and 142B which move the first leaves 140A and 140B. Switch circuits which are connected to the second drive units select the leaf to be moved among the second groups of leaves. By a combination of the close and far movement of the first leaves 140A and 140B in the X direction and the close and far movement of the second groups of leaves 141A and 141B in the Y direction, an irregular radiation range U which is approximated to a diseased part T can be created, as shown in FIG. 5. The second drive units which move the leaves 141A1 to 141An and 141B1 to 141Bn of the second groups 141A and 141B. FIG. 6 shows an illustration for explaining the second drive units which move the leaves 141A1 and 141B1. The edges of the leaves 141A1 and 141B1 strongly contact the stators STA1 and STB1 with contact pressure. The stators STA1 and STB1 include metal materials M, elastic bodies EL and piezoelectric transducers CE. The piezoelectric transducer CE is known as an ultrasonic transducer, such as piezoelectric ceramic, which generates ultrasound according to received high frequency electric signal. The piezoelectric transducers CE are connected to the high-voltage generation units GA1 and GB1 via the signal lines LA1 and LB1, and high frequency electric signals are supplied to the piezoelectric transducers. With reference to FIG. 7, the leaf 141 and the drive unit 143 are explained. The second drive units and the leaves 141A1 to 141An and 141B1 to 141Bn are the same as or similar to the following drive unit 143 and the leaf 141. The stator ST which strongly contacts the edge of the leaf 141 with the contact pressure is first explained. The stator ST, as a single unit, includes a piezoelectric transducer CE, a metal material M and an elastic body EL positioned therebetween, and a surface of the metal material M directly contacts the edge of the leaf 141. Furthermore, a plurality of comb-shaped grooves t are created on a contact side of the metal material to the leaf 141, and the groove extends in a direction perpendicular to a width direction of the leaf 141. Each piezoelectric transducer includes an electrode, and the high frequency electric signal is supplied from the high-voltage generation unit G to the electrode via the signal line L. An operation of the drive unit is explained with reference to FIG. 8. In FIG. 8, the same reference numbers are attached as illustrated in FIG. 7. When the predetermined high frequency voltage of the high frequency signal is supplied from the high-voltage generation unit G to the piezoelectric transducer CE, an ultrasonic vibration is generated in the piezoelectric transducer CE. This generated ultrasonic vibration proceeds in one direction continuously, bending a metal material M of the stator ST. That is, as if a wave of a sea wimples in one direction, the ultrasonic vibration generated in the piezoelectric transducer CE bends the stator ST. Therefore, a plane, which contacts the stator ST, of the leaf 141 includes a portion where a head of the wave contacts and another portion where the head does not contact. On the head (peak) of the wave which contacts the plane of the leaf 141, elliptic movement occurs on the contacting point, a track of the elliptic movement is drawn in an opposite direction to a movement direction of the wave proceeding on the stator ST, and a long axis of the elliptic movement is different from the movement direction of the wave. Therefore, in response to influence of the elliptic movement, the leaf 141 moves in an opposite direction to the movement direction of the wave proceeding on the stator ST. Therefore, when the stator ST is fixed, the leaf 141 is movable and the wave occurs on the stator ST in a right direction, the elliptic movement occurs in a left direction on each peak which contacts the leaf 141. In response to the elliptic movement, the leaf 141 moves in the left direction to the stator ST. On the other hand, when the wave proceeds in the left direction on the stator ST, the leaf 141 moves in the right direction. Thus, by controlling the high frequency signal supplied to the piezoelectric transducer CE of the stator ST, it is possible to move the leaf 141 in an arbitrary direction. The plurality of comb-shaped grooves t are provided on a side, which contacts the leaf 141, of the metal material M of the stator ST, in order to enlarge amplitude of the elliptic movement and reduce friction The present invention may be not limited to the above embodiments, and various modifications may be made without departing from the spirit or scope of the general inventive concept. For example, although it is explained in the above embodiment that the outside surface of the leaf 141 contacts the stator ST, an inside surface of the leaf 141 may contact the stator ST to move the leaf 141. As explained above, according to the embodiment, the following various effects, which does not limit the present invention, are considered, for example. In a first effect, when the leaf is moved directly by the stator which mainly includes the piezoelectric transducer, a driving mechanism can be simplified and miniaturized. Therefore, it is possible to reduce the thickness of each leaf and increase the number of leaves, and the irradiation range of radiation can be approximated to the medical treatment range more. In a case where the collimator 14 is the same size, radiation ranges, about the second groups of leaves 141A and 141B, formed by conventional small number of thick leaves and by large number of thin leaves in the embodiment are illustrated in FIGS. 9A and 9B, respectively. In FIG. 9A showing the conventional small number of thick leaves, large gaps (unnecessary radiation range) occur even when the radiation range is approximated to a shape of diseased part F as much as possible. In FIG. 9B showing the large number of thin leaves in the embodiment, since the radiation range is approximated to the shape of the diseased part F more, the unnecessary radiation range can be reduced. In a second effect, since a gear mechanism is not used to move the leaves, the backlash does not occur, and an error of a stop position of the leaves can be reduced, and setting accuracy of the radiation range can be improved. In a third effect, since speed is controllable in stepless, high accurate speed control and position control are possible, and the stop position accuracy of the leaves is improved. Moreover, since operation noise is reduced, it is suitable as a medical apparatus. In a forth effect, since the leaf and the metal material of the stator are contacted in high contact pressure, even after the supply of the high frequency voltage to the piezoelectric transducer is stopped, namely power supply is stopped, a brake function which maintains holding power continues. Once the position of the leaf fixed, the position is maintained and interference between adjacent leaves is reduced, and therefore the setting accuracy of the radiation range is improved. In addition, the metal material M may be placed on farther positions from the isocentre than a maximum radiation range when the leaves 141A1 and 141A2 are positioned in furthermost positions. In this case, the metal materials do not block the radiation ray.
	claims	1. A containment vessel comprising:a horizontally-extending base mat supporting a load of a boiling water reactor pressure vessel accommodating a core;an inner shell disposed on the base mat so as to gas-tightly cover the boiling water reactor pressure vessel; andan outer shell disposed on the base mat so as to horizontally cover only an outer periphery of the inner shell in a gas-tight manner, the outer shell not covering the whole inner shell,the inner shell including:a first cylindrical side wall having a lower end connected to the base mat and an upper end located higher than at least an upper end of the core and horizontally surrounding a periphery of the boiling water reactor pressure vessel;a containment vessel head covering an upper portion of the boiling water reactor pressure vessel and being formed of a steel so as to be capable of being removed upon refueling;a first top slab gas-tightly connecting a periphery of the containment vessel head and an upper end portion of the first cylindrical side wall;a dry well constituting a part of the first cylindrical side wall and accommodating the boiling water reactor pressure vessel;a wet well constituting a part of the first cylindrical side wall;a suppression pool accommodated in the wet well; anda vent pipe connecting the dry well to the suppression pool, the outer shell including:a second cylindrical side wall having a lower end connected to the base mat and surrounding an outer periphery of the first cylindrical side wall in a gas-tight manner, a top of the second cylindrical side wall being not higher than a top of the first top slab;a second top slab gas-tightly connecting an upper end of the second cylindrical side wall and the inner shell, the second cylindrical side wall not extending above the second top slab; andan outer well which is a space gas-tightly surrounded by the second cylindrical side wall, the second top slab, and the base mat, an atmosphere in the outer well being replaced by nitrogen to make an oxygen concentration lower than ordinary air, whereinthe second cylindrical side wall and the second top slab form a pressure boundary. 2. The containment vessel according to claim 1, further comprising:a gas-phase vent pipe connecting a gas-phase portion of the wet well and the outer well; andan isolation and connection switching system mounted to the gas-phase vent pipe and configured to be closed during reactor normal operation and be opened upon occurrence of a reactor accident. 3. The containment vessel according to claim 1, whereinatmosphere in the dry well and the wet well and atmosphere in at least some space in the outer well are replaced by nitrogen to make an oxygen concentration lower than air during reactor normal operation. 4. The containment vessel according to claim 3, whereina part of the outer well is partitioned to form an equipment room with air atmosphere, andatmosphere in the outer well excluding the equipment room during reactor normal operation is replaced by nitrogen to make an oxygen concentration lower than normal air. 5. The containment vessel according to claim 1, whereinan outer pool in which pool water is pooled is provided in lower part of the outer well. 6. The containment vessel according to claim 5, further comprising a gas-phase vent pipe connecting a gas-phase portion of the wet well and the outer well, wherein a leading end of the gas-phase vent pipe is disposed in the pool water of the outer pool. 7. The containment vessel according to claim 6, whereina scrubbing nozzle is attached to a leading end of the gas-phase vent pipe. 8. The containment vessel according to claim 5, whereina medication that increases a dissolving property of radioactive iodine is mixed in the pool water of the outer pool. 9. The containment vessel according to claim 5, whereinnon-radioactive iodine is mixed in the pool water of the outer pool. 10. A nuclear power plant comprising:a core;a boiling water reactor pressure vessel accommodating the core; anda containment vessel including:a horizontally-extending base mat supporting a load of the boiling water reactor pressure vessel accommodating the core;an inner shell disposed on the base mat so as to gas-tightly cover the boiling water reactor pressure vessel; andan outer shell disposed on the base mat so as to horizontally cover only an outer periphery of the inner shell in a gas-tight manner, the outer shell not covering the whole inner shell,the inner shell including:a first cylindrical side wall having a lower end connected to the base mat and an upper end located higher than at least an upper end of the core and horizontally surrounding a periphery of the boiling water reactor pressure vessel;a containment vessel head covering an upper portion of the boiling water reactor pressure vessel and being formed of a steel so as to be capable of being removed upon refueling;a first top slab gas-tightly connecting a periphery of the containment vessel head and an upper end portion of the first cylindrical side wall;a dry well constituting a part of the first cylindrical side wall and accommodating the boiling water reactor pressure vessel;a wet well constituting a part of the first cylindrical side wall;a suppression pool accommodated in the wet well; anda vent pipe connecting the dry well to the suppression pool, the outer shell including:a second cylindrical side wall having a lower end connected to the base mat and surrounding an outer periphery of the first cylindrical side wall in a gas-tight manner, a top of the second cylindrical side wall being not higher than a top of the first top slab;a second top slab gas-tightly connecting an upper end of the second cylindrical side wall and the inner shell, the second cylindrical side wall not extending above the second top slab; andan outer well which is a space gas-tightly surrounded by the second cylindrical side wall, the second top slab, and the base mat, an atmosphere in the outer well being replaced by nitrogen to make an oxygen concentration lower than ordinary air, whereinthe second cylindrical side wall and the second top slab form a pressure boundary. 11. The nuclear power plant according to claim 10, whereina fuel pool is arranged above the first and second top slabs. 12. The nuclear power plant according to claim 10, whereinan upper protective barrier covering an upper portion of the containment vessel is provided.
048636819	summary	FIELD OF THE INVENTION This application relates to an elongated replacement rod for use with nuclear fuel assemblies of the type having two end fittings connected by guide tubes. A plurality of fuel rod and guide tube cell defining spacer grids containing fuel rod support features and optional reactor coolant mixing vanes are secured to the guide tubes in register between the end pieces at spaced intervals. BACKGROUND OF THE INVENTION Pressurized Water Reactors (PWR) for nuclear steam generating systems require fuel reconstitution in the form of fuel rod and "poison" rod replacement for proper fuel cycle management within the core. Removal and replacement of rods after operation of the assembly must be accomplished remotely because of the radiation field surrounding the fuel assembly. Grid damage during subsequent rod insertion, or the use of specialized tooling or procedures to prevent grid damage, can be expensive and time-consuming. The use of specially fabricated replacement rods as substitutes for removed fuel and poison rods has been a common past practice, and the current invention is a design for these replacement rods which minimizes the potential for grid damage.
039829944	summary	BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to fuel elements for nuclear reactors and, more particularly, to methods and apparatus for inserting and withdrawing fuel rods from fuel element grid structures, and the like. 2. SUMMARY OF THE PRIOR ART In order to function, nuclear reactors must have an inventory of fissionable material that will sustain a continuous sequence of fission reactions. Frequently, the uranium, or other nuclear fuel, is loaded into long, hollow and slender metal rods that are termed "fuel rods". These loaded fuel rods then are mounted together into groups each of perhaps 200 rods to form "fuel elements". A number of these fuel elements, when assembled, form one array which comprises the reactor core that provides the concentration of fissionable material which is needed to continue the fission process. The fuel rods within the fuel elements usually are subjected to a number of adverse environmental conditions during reactor operation. In this respect, the heat generated in the fuel rods often is removed by means of the primary cooling water that flows through the reactor core in a direction which is parallel to the longitudinal axes of the fuel rods. Especially in connection with power reactors, the water flow velocity and the flow rate must be very high in order to remove the large quantity of heat that is generated. The surface area of the individual fuel rods, moreover, must be as fully exposed as possible to the flowing water in order to promote a high thermal conductivity between the fuel rod and the primary coolant and to prevent the development of "hot-spots" on the fuel rod due to poor local flow conditions, or the like. Thus, fuel element structures are confronted with the need to satisfy two essentially conflicting requirements; the need to stabilize a large number of long, dense, nuclear fuel-filled thinwalled tubes that are exposed to the vibratory and other forces which are caused by very high cooling water flow rates, and the need to reduce the structural restraints on these fuel rods to a minimum in order to promote heat transfer from the rods to the coolant. To satisfy these essentially conflicting needs, fuel element grids often are used to stabilize the array of fuel rods within the grid structure. Usually, these grids comprise a cellular structure that is formed through the mutually perpendicular intersections of a group of interlocking metal plates. One fuel rod is lodged in each of the cells thus formed in the grid structure. Bosses and the like protrude from the surfaces of the portions of these interlocking plates that form the individual cell walls. These bosses engage the outer surface of the fuel rod within the particular cell and serve to restrain rod motion. These bosses are of two basic types. One type of boss is of a very resilient character, being essentially spring-mounted. These resilient bosses permit the fuel rods to be inserted into the grid structure with relative ease. During reactor operation, however, the resilient nature of the boss mountings enables the bosses to move relative to the adjacent fuel rod surfaces. This motion produces an undesirable wearing or "fretting" of the rod surface that weakens the rod structure and can cause a failure. The other type of boss is a very stiff and non-resilient arrangement that essentially eliminates relative movement between the fuel rods and the respective bosses. These stiff bosses, although eliminating "fretting" problems, nevertheless, lead to other difficulties. In this respect, it is difficult to lodge a fuel rod within a grid cell without scraping and gouging the rod surface against the relatively unyielding bosses. Scratches of this nature also weaken the fuel rod structure and establish corrosion loci, too. Thus, there exists a need to provide an efficient and economical means for inserting fuel rods into the cells of a fuel element grid that has protruding non-resilient bosses without marring the rod surfaces. SUMMARY OF THE INVENTION These and other problems that have characterized the prior art are overcome, to a large extent, through the practice of the invention. Illustratively, the corners of the mutually perpendicular interlocking plates that form the cellular structure of the fuel element grids are provided with slits that are generally parallel to the longitudinal axes of the fuel rods. A long thin bar is inserted into the grid structure through these slits in a direction that is generally parallel to one of the grid plates and perpendicular to those other plates that are normal to and interlock with the plate in question. Stubs are formed on one side of the bar. These stubs are spaced from each other along the length of the bar by distances that are each equal to the width of a cell. These stubs protrude in a transverse direction relative to the length of the bar, moreover, for a distance that is substantially greater than the slit's transverse gap. The bar is inserted into the grid structure by orienting the stubs in a direction that is essentially parallel to the longitudinal axes of the fuel rods. In this manner, the bar will pass through the slits. The bar then is rotated through an angle of 90.degree. in a direction that turns the stubs away from the grid plate with which the bar is parallel. The bar is then moved in a lengthwise direction to enable the stub extremities each to engage a portion of the adjacent respective plates which are perpendicular to and interlock with the grid plate with which the bar is parallel. A further application to the bar of force in a lengthwise direction permits the stubs to deflect the bosses on the perpendicular plates out of their usual orientation. This temporary distortion of the individual cells, when duplicated with respect to one of the perpendicular plates in each of the cell structures, provides sufficient clearance for the fuel rods to be lodged in the grid structure without being gouged and scratched by protruding bosses. On lodging the fuel rods within the grid structure, the lengthwise forces that are applied to the bars are relaxed to enable the deflected bosses to return to their normal positions within the cells and grasp or clutch the respective rods. The bars are once more rotated through 90.degree. in order to disengage the stubs from the perpendicular plates and bring the stubs into general alignment with the longitudinal axes of the fuel rods. The bars then are withdrawn from the grid structure through the slits. Thus, there is provided a technique for inserting fuel rods into a fuel assembly grid structure that prevents the rods from being marred or otherwise damaged during assembly. An essentially reverse, albeit similar procedure, is employed to withdraw fuel rods from a grid structure. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention .
	abstract	When IMRT technology for a radiation therapy system utilizing an X-ray or the like is applied to a particle beam therapy system having a conventional wobbler system, it is required to utilize two or more boluses. The present invention solves the problem of excess irradiation in IMRT by a particle beam therapy system. More specifically, the problem of excess irradiation in IMRT by a particle beam therapy system is solved by raising the irradiation flexibility in the depth direction, without utilizing a bolus. A particle beam irradiation apparatus has a scanning irradiation system that performs scanning with a charged particle beam accelerated by an accelerator and is mounted in a rotating gantry for rotating the irradiation direction of the charged particle beam. The particle beam irradiation apparatus comprises a columnar-irradiation-field generation apparatus that generates a columnar irradiation field by enlarging the Bragg peak of the charged particle beam.
063209225	description	DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, particularly to FIGS. 1 and 2, there is illustrated a preferred embodiment of a tool, generally designated 10, constructed in accordance with the present invention. Tool 10 is useful both as an extractor tool for extracting fuel rods from a fuel assembly and as an insertion tool for inserting fuel rods into the fuel assembly. Tool 10 includes an inner rod 12 mounting a handle H at one end and which rod 12 is, in part surrounded by a coaxially extending outer tube 14. An externally threaded portion or locking sleeve 16 is secured to the inner rod 12 by a pinned connection at an intermediate location along the rod. A cover sleeve 18 is secured to the proximal end of the outer tube 14, for example, by welding. The opposite end of the cover sleeve 18 includes a flange 20 (FIG. 3A) rotatably received within an internal recess of a retaining ring 22 secured by bolts to a locking tube nut 24. It will be appreciated that, with the flange 20 locked by the retaining ring 22 to the locking tube nut 24, the outer tube 14, cover sleeve 18 and locking tube nut 24 are jointly axially displaceable while the locking tube nut 24 is rotatable relative to the cover sleeve 18, outer tube 14 and threaded locking sleeve 16. The locking tube nut 24 is internally threaded for threaded engagement with the locking sleeve 16 and serves as a drive element as described below. Inner rod 12 also includes a laterally extending pin 26. The pin 26 is received in a slot 28 formed through a side wall of the outer tube 14. The outer sleeve 18 overlies the end of the pin 26 received in the slot 28 but is not connected to the pin 26. As a consequence, it will be appreciated that the pin 26 prevents relative rotation between the inner rod 12 and outer tube 14 while enabling relative axial movement of the inner rod 12 and outer tube 14 to the limited extent of the slot 28. With the above described arrangement, it will be appreciated that rotating the locking tube nut 24 in a direction to cause the locking sleeve 16 to thread relative to the tube nut 24 for movement to the right in FIG. 1 the pin 26 will advance to the opposite of the slot, i.e., as illustrated in FIG. 3B. Rotation of the locking tube nut 24 in the opposite direction causes relative displacement of the inner rod 12 and outer tube 14 to the position illustrated in FIG. 3A, locating the locking pin 26 in the left-hand end of slot 28 as illustrated. Consequently, the inner rod 12 and outer tube 14 are axially displaceable relative to one another for the full extent of the length of the slot 28. Referring to FIG. 2, the outer tube 14 terminates in an outer sleeve 30 having a split inwardly directed flange 32 at its distal end. The end of inner rod 12 is reduced in diameter at 34 and has a transitional outwardly tapered section 36 between its end 34 and the inner rod proper. The end of the inner rod 12 terminates in a flat end face 38. An opening 40 extends laterally through the end of inner rod 12 adjacent to the transition between the reduced diameter section 34 and tapered section 36. Referring to FIGS. 2, 4 and 4A, there is provided at the end of tool 10 a collet, generally designated 42, having split collet sections 44 which are the mirror images of one another. The split collet sections 44 have generally semi-circular aligned openings at lateral sides thereof for receiving the pin 46 extending through the opening 40 of the inner rod 12. The proximal ends of the split collet sections 44 are tapered at 48 (FIG. 4) to permit the collet sections to pivot about pin 46 between opened and closed positions with a clearance along a diametrical plane. The proximal end of the collet sections also have split flanges 49 for reception in the open areas between the split flanges 32 of the outer sleeve 30 to facilitate assembly of the collet sections 44, distal end of inner rod 12 and the outer sleeve 30. The distal ends of collet sections 44 include jaws 50. Referring to FIG. 2, a first end plug 52 of a nuclear fuel rod F.R. includes a barbed end cap 54 having a flat end face 55 and a tapered distal end portion defining a groove or neck portion 56 with the body 58 of the end plug 52. The tapered and neck portions 54 and 56 are circular in configuration and form a barbed end on the end plug 52. The jaws 50 of the split collet sections are geometrically sized for reception about the neck portion 56 between the tapered section 54 and the main body 58 of the end plug 52. With this design, capture and retention of end plug 52 by barbed area 54 and neck 56 is fully mechanical and does not rely on springs or other ancillary moving parts. The opposite end of the nuclear fuel rod F.R. mounts a second or lower end plug 60 which is generally cylindrical in shape for reception in or a snap fit with a complementary-sized opening 61 in the lower tie plate L.T.P. To use the tool of the present invention to extract a fuel rod from a nuclear fuel bundle, the collet end of the extractor tool 10 is initially closed. With the collet closed, the extractor tool 10 is inserted axially into the fuel bundle through the spacer openings or ferrules in axial alignment with the end plug mounted on the fuel rod desired to be removed. The tool 10 may be inserted to the extent that the collet, i.e., the end faces of jaws 50, butts the end face 55 of the end plug 52. The tool may then be slightly backed off the end plug 52. The locking tube nut 24 is then rotated in a direction causing the outer tube 14 to be withdrawn relative to the inner rod 12. Upon withdrawal of the outer tube 14, the flanges 32 of the outer sleeve 30 cam against the split flanges 49 of the collet sections 44 to pivot the collet sections 44 about pin 46, displacing the jaws 50 away from one another into a collet-open position. Once opened, the extractor tool can be axially advanced to butt the end face 38 of the inner rod 12 against the end face of the end cap surface 55. With this abutting arrangement, the jaws 50 straddle the neck portion 56 of the end cap. By rotating the locking tube nut 24 in an opposite direction threading on locking sleeve 16, the outer tube 14 is advanced relative to the inner rod 12 whereby flanges 32 cam along the outer surfaces 43 of collet sections 44, displacing the sections 44 toward one another and the jaws 50 into the annular slot straddling neck portion 56. With the end cap thus engaged by the collet, the extractor tool and fuel rod can be withdrawn axially from the fuel bundle. In the event the fuel rod is stuck or cannot be readily axially withdrawn, a slide hammer 62 on the inner rod 12 can be impacted upwardly against the handle H or downwardly against the end 64 of the locking sleeve 16, the locking sleeve end or handle in effect forming anvils for the hammer. In this manner, the fuel rod can be jarred loose such that the extractor tool can then withdraw the fuel rod from the fuel bundle. It will be appreciated that a fuel rod can be disposed in a bundle using the tool hereof as an insertion tool. With the collet engaged about the upper end cap of the fuel rod, the fuel rod and extractor tool can be inserted into the bundle with the fuel rod passing through the openings or ferrules of the spacers. Because of the tapered end of the lower end plug 60, the fuel rod end plug 60 can be inserted or snapped into a complementary opening in the lower tie plate. The hammer and anvil arrangement can be employed to drive or further insert the fuel rod into the tie plate opening by impacting hammer 62 against sleeve 16. Upon final insertion of the fuel rod, the locking tube nut 24 can be threaded on sleeve 16 to withdraw the outer tube 14 relative to the inner rod 12 to displace the collet sections to a collet-open position whereby the tool can be displaced upwardly above the end plug. Once disposed above the end plug and before the collet can be withdrawn through the opening or ferrule of the spacers above the fuel rod end plug, the locking tube nut 24 is threaded on sleeve 16 to close the collet sections, thereby reducing the diameter of the collet to a size for reception through the spacer openings or ferrules to facilitate withdrawal of the tool 10 from the fuel bundle assembly. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
	summary
046541829	claims	1. Apparatus for containing plasma in a high energy plasma device, said apparatus comprising: a confinement vessel having a wall defining a closed interior including a plasma path, said wall having an inside surface; a magnet system including first conductors disposed outside said vessel for generating a magnetic field extending inside said closed interior; an armature ring disposed inside said wall; means for supporting said ring for rotation in a plane extending transversely of said plasma path and for preventing substantial movement of said ring in the direction of said plasma path, said ring including armature conductors extending at an angle to lines of force of said magnetic field; means for supplying direct current to said armature conductors; a protective coating carried by said ring and facing said plasma path to provide a first wall whereby the interaction of said magnetic field and the current in said armature conductors causes rotation of said armature ring to prevent damage to said wall due to localized heating. a vacuum tight liner wall made up, at least in part, by a series of sections, each section having a closed peripheral wall defining an interior with open ends, with adjacent interiors of adjacent sections forming, at least in part, a plasma path, at least one of said sections having an inside surface and an outside surface with its interior being generally circular in section; a magnet system including first conductors disposed outside said one section for generating a magnetic field extending inside said one section; an armature ring supported inside said one section, said ring carrying means for entering into rolling engagement with the inside surface of said one section, said ring comprising current carrying armature conductors extending at an angle to lines of force of said magnetic field; and armor tiles carried by said ring and facing said plasma path for acting as plasma limiters whereby the interaction of said magnetic field and the current in the armature conductors causes rotation of said armature ring in said one section to prevent damage to said liner wall due to localized heating. rotatably mounting inside said section an armature ring comprising rollers for engaging said inside surface and further comprising armature conductors extending at an angle to lines of force of said magnetic field; affixing armor tiles to said ring facing said plasma path for acting as plasma limiters; causing direct current to flow through said armature conductors whereby the interaction of said magnetic field and the current in said armature conductors results in rotation of said armature ring to prevent damage to said section due to localized heating. 2. Apparatus as set forth in claim 1 further comprising a plurality of said armature rings disposed at spaced locations along said plasma path. 3. Apparatus for containing plasma in a high energy plasma device, said apparatus comprising: 4. Apparatus as set forth in claim 3 wherein said liner wall defines a torus. 5. Apparatus as set forth in claim 3 further comprising means for supplying direct current to said armature conductors of said armature ring. 6. Apparatus as set forth in claim 5 wherein said armature ring is electrically conductive and comprises a first annular end and a second annular end with said armature conductors comprising spaced bars interconnecting said first and second ends. 7. Apparatus as set forth in claim 6 wherein said means for supplying direct current comprises a first brush mounted on a first conductive standard extending through said liner and slidably engaging said one annular end, and a second brush mounted on a second conductive standard extending through said liner and slidably engaging said second annular end, said brushes functioning to direct current through said bars and to hold said armature ring from substantial axial movement. 8. Apparatus as set forth in claim 6 wherein said means for entering into rolling engagement comprises rollers extending between said first and second annular ends between adjacent bars. 9. Apparatus as set forth in claim 8 wherein each of said annular ends has a plurality of cavities, one cavity in each of said annular ends forming an aligned pair, each roller having a pair of oppositely extending lugs received in a respective pair of cavities to retain the roller. 10. Apparatus as set forth in claim 9 wherein each cavity holds spring means bearing against one of said lugs for biasing its corresponding roller against the interior surface of said one section. 11. Apparatus as set forth in claim 3 wherein said armature ring is formed of material having a greater coefficient of thermal expansion than the coefficient of expansion of the material of said one section so that upon heating, said armature ring expands into engagement with the interior surface of said one section. 12. A method of protecting a vacuum tight liner wall in a high energy plasma device, said liner wall including a section having a closed peripheral wall defining an interior with open ends and forming, in part, a plasma path, said section having an inside surface and an outside surface with said interior being generally circular in section, said plasma device including a magnet system including first conductors disposed outside said section for generating a magnetic field extending inside said section, said method comprising the following steps:
047611278	description	In the drawing a drum 1 to receive radioactive wastes and a cement or grout is shown in phantom outline. The drum 1 comprises a cylindrical vessel having rolling rings 10 which is open at its upper end and located on a platform 2. The platform 2 is provided with three feet 3 spaced apart at equal intervals around the periphery of the drum. Each foot 3 is mounted on a respective pistonless pneumatic actuator. Each actuator comprises a cushion 4 which is connected through a respective hose pipe 5 to a manifold 6 which in turn is connected to compressed gas supply, conveniently compressed air, via isolation valve 7. The latter can be positioned at a location remote from the drum 1. For example, in the encapsulation of radioactive wastes, the drum can be located within a cave and behind shielding with the valve 7 outside the cave. In use, the drum 1 is positioned on the platform 2 with the cushions 4 in a deflated condition such that the upper open end of the drum can be located beneath the end of a charge chute 8. The cushions 4 are then inflated from the gas supply via valve 7 whereby to lift the drum such that its upper open end makes sealing contact with a plate 9 at the bottom of the charge chute and compress the rolling rings 10 by a pre-determined amount. Wastes together with cement or grout are delivered into the drum and at the same time a vibrator or vibrators 11 secured to and mounted under platform 2 is or are operated to thereby vibrate the drum and its contents but without breaking the sealing engagement between the end of the drum and the charge chute due to the pre-compression of the rolling rings. The amplitude of vibration is small, for example it can be a fraction of a millimetre and the frequency can be in the range 20 to 50 cycles per second. The vibration serves to pack efficiently the contents of the drum and assists in the distribution of the cement or grout about the radioactive wastes thereby avoiding voids and gaps within the drum. The sealing engagement serves to prevent possible contamination of the exterior of the drum during filling. After filling the cushions are deflated to permit removal of the drum.
052260658	summary	BACKGROUND OF THE INVENTION The present invention relates generally to a device for disinfecting medical materials and more particularly to a device for disinfecting medical materials by exposing the materials to a combination of heat and gamma radiation. The term medical materials encompasses medical waste, veterinary waste and medical products. The problems with current waste handling methods will be discussed first. The problem of disposal of solid waste is becoming increasingly acute. The primary methods of solid waste disposal have been burning or burial in landfills. These two methods have severe disadvantages. Burning liberates waste particles and fumes which contribute to acid rain. Burying wastes results in toxic chemicals leaking into the surrounding earth and contaminating the water supply. Although increasing amounts of solid waste are being recycled, which alleviates the problems of the other two disposal methods, presently available recycling methods do not provide a complete solution to the disposal problem. Waste disposal is of even more urgent concern when the waste may cause infection. Such infectious waste is a by-product of medical and veterinary care. For example, regulated medical waste consists of the following categories: 1. Cultures and stocks of infectious agents and associated biologicals, PA0 2. Pathological wastes, PA0 3. Human blood and blood products, PA0 4. Contaminated sharps (including needles, syringes, blades, scalpels, and broken glass), PA0 5. Animal waste, PA0 6. Isolation waste (gloves and other disposable products used in the care of patients with serious infections), and PA0 7. Unused sharps. These wastes can be generally divided between general medical waste, including waste listed above in categories 1, 2, and 3; veterinary waste, or category 5; and waste that is predominantly plastic, including categories 4 and 6. Hospitals typically segregate types of waste. Contaminated sharps and isolation waste are categories of special concern, as this waste may carry highly dangerous infections such as AIDS or hepatitis. Sharps in particular have caused public panic when observed on beaches and other public areas. Hospitals and other generators of medical and veterinary waste employ three main methods of waste handling: 1) on-site incineration of the waste, 2) on-site steam autoclaving of the waste and later shipment to a landfill, and 3) no on-site processing before turning the waste over to a waste hauler. Predominantly located in urban areas, many hospital incinerators emit pollutants at a relatively high rate. In the emissions of hospital incinerators, the Environmental Protection Agency (EPA) has identified harmful substances, including metals such as arsenic, cadmium, and lead; dioxins and furans; organic compounds like ethylene, acid gases, and carbon monoxide; and soot, viruses, and pathogens. Emissions from these incinerators may be a bigger public health threat than improper dumping. (Stephen K. Hall, "Infectious Waste Management: A multi-faceted Problem," Pollution Engineering, 74-78 (Aug. 1989)). Although steam autoclaving may be used to disinfect waste before further processing, it is expensive and time-consuming. Temperature monitoring devices such as thermocouples and biological indicators such as heat-resistant Bacillus stearothermophilus spores may be used to assure effective disinfection. The application of heat denatures the protein in microorganisms causing death in a short time. Viruses are rapidly inactivated; bacteria and particularly bacterial spores survive somewhat longer than viruses. U.S. Pat. No. 2,731,208 (Dodd) teaches a steam-sterilizing apparatus for disposing of contaminated waste which incorporates shredding the waste ("including paper containers such as used sputum cups," Col. 1, Lines 28-29). This reference teaches processing only limited types of items; it teaches the use of steam sterilization alone and has the further disadvantage of depositing the shredded mixture into a sewer. (Col. 4, line 49). Whether or not the hospital first autoclaves its medical waste, including broken needles and glass, the waste is then turned over to a waste handler for transport to a landfill or other depository. U.S. Pat. No. 3,958,936 (Knight) teaches compaction of hospital waste for more efficient landfill disposal. Specifically, this reference teaches the application of heat in the range of about 400.degree. to 600.degree. F. to hospital and other waste to melt the plastic and turn it into a hard, compact block for safer disposal in landfills. The waste is disinfected and needles become imbedded in the plastic. This method has the disadvantages of requiring high temperatures and landfill disposal. As mentioned above, metropolitan landfills are becoming filled and unauthorized dumping is becoming a problem. Another area of concern is the sterilization of medical products. By medical product we mean any product which must be disinfected or sterilized prior to use in patient or animal care. This area is exemplified by, but not limited to, the following: needles, syringes, sutures, scalpels, gloves, drapes, and other disposable items. Many reusable items also must be provided in sterile form. Primary sterilization methods include the use of autoclaving, ethylene oxide, and ionizing radiation. The heat and humidity of autoclaving are quite damaging to many disposable medical products; hence autoclaving is not preferably used, and ethylene oxide and ionizing radiation are preferred commercially. To sterilize medical products with known methods, poisonous ethylene oxide gas fills a closed chamber containing the products to be sterilized. For effective sterilization, not only must the ethylene oxide concentration be carefully controlled, but the temperature, humidity and porosity of the sterilizer load also must be regulated. Ethylene oxide is slow to dissipate from plastics and may require that the medical products be stored until the ethylene oxide falls to a safe level. Ethylene oxide also must be carefully vented to the atmosphere after the sterilization cycle to avoid poisoning workers. If ionizing radiation such as gamma radiation is used by itself, it must be administered at such intense doses that many plastics become yellow and brittle. For example, U.S. Pat. No. 3,940,325 (Hirao) teaches ways to adjust the formulas of plastics for syringes to avoid yellowing and cracking after exposure to gamma radiation. Other substances may also be damaged by radiation. Ionizing radiation, or gamma radiation, is produced by electron accelerators or radioisotopes such as cobalt 60 or cesium 137. Both sources produce high-energy photons which disinfect by inactivating the DNA of viruses and bacteria. These irradiated microorganisms lose their ability to reproduce and cause infections. Gamma radiation rapidly inactivates bacteria but is less effective against viruses. On a large-scale industrial basis, gamma irradiation with cobalt 60 has been used to sterilize medical products prior to their use in patients. The dosage of gamma radiation, measured in rads or megarads (Mrads), varies but a dose of 2.5 Mrads is usually selected as a starting point in known methods. However, such doses also damage the product being sterilized. The following patents teach methods to sterilize medical products with less harm to the product. U.S. Pat. No. 3,617,178 (Clouston) teaches a method of improving sterilization efficiency by increasing hydrostatic pressure. Elevated hydrostatic pressure causes sterilization-resistant bacterial spores to germinate or begin to grow, but it has no effect on viruses. Germination makes the bacteria more sensitive to radiation. This reference teaches optimizing the hydrostatic pressure effect by adjusting temperature (up to 80.degree. C.), and then disinfecting the sutures with lower doses of gamma radiation or other modes of disinfection. According to Clouston, elevated pressure and fluid or moist gas are essential to his method; raised temperature alone has a negligible effect. Furthermore, the pressure/heat/moisture treatment this reference teaches is intended to cause bacterial spores to germinate, not to immediately sterilize or inactivate microorganisms. In contrast, U.S. Pat. Nos. 4,620,908 (Van Duzer) and 3,704,089 (Stehlik) teach pre-freezing injectable proteins and surgical adhesive respectively before irradiation with cobalt 60. In these methods, the temperature is reduced not to sterilize the product, but to protect the product from damage by gamma radiation. U.S. Pat. No. 3,602,712 (Mann) describes an apparatus for gamma irradiation and disinfection of sewage and industrial waste. Gamma radiation by itself, however, is impractical for disinfecting medical waste. Gamma radiation in the doses used to sterilize medical products is considered too expensive for medical waste processing. Besides gamma radiation, other energy sources are being considered as potential sterilants in known systems. Microwaves are increasingly being investigated for rapid sterilization of individual medical devices and shredded medical waste. Recently, an experiment showed that metallic instruments could be disinfected in only 30 seconds in a microwave. (N. Y. Times, "Science Watch: Microwave Sterilizer is Developed," Jun. 20, 1989). A problem is that this particular method can handle only a few instruments at a time. According to one publication, a medical waste disposal system utilizing microwaves has apparently been developed. This system first shreds the waste, sprays it with water and passes the mixture through a microwave chamber designed to raise the temperature of the mixture to 205.degree. C. After the disinfection step, the system compresses the waste and packages it for shipment to landfills or incinerators. (The Wall Street Journal, p. B3, Apr. 10, 1989). One potential problem with this system is that shredding before disinfection could release infectious particles to the environment and may thus spread contagion. Another problem is ultimate disposal of the waste: It persists in landfills or may pollute the air when incinerated. Further, microwaves are limited in their penetration. If applied to large-scale, boxed medical waste, the microwaves alone do not heat very effectively. In contrast, radio-frequency (R-F) waves are relatively low-frequency waves which penetrate more effectively. Radio-frequency waves have been used directly and indirectly for sterilization. U.S. Pat. No. 2,114,345 (Hayford) teaches a radio-frequency applicator with electroscopic control for destroying bacteria in bottled beer and similar articles. This reference teaches an apparatus that sterilizes with radio-frequency waves alone. Therefore, it teaches away from the combination of radio-frequency waves with gamma radiation. U.S. Pat. No. 3,948,601 (Fraser et al.) teaches the indirect use of radio-frequency waves in disinfecting a wide variety of medical and hospital equipment as well as human waste. This reference teaches the use of radio-frequency waves to heat certain gases (particularly argon) to ionize into gas plasma at approximately 100.degree. to 500.degree. C. This references teaches that "cool" plasma, (Col. 1, Line 12) reaches the article to be sterilized at a temperature of only 25.degree. to 50.degree. C. and very low pressure and effectively sterilizes the article. However, sterilization by plasma gas does not suggest the direct use of radio-frequency waves in sterilization. Reprocessing of waste and especially medical waste is vital for several reasons. First, landfills, particularly in many urban areas, are becoming filled. In addition, older landfills may leak. Thus, burying wastes is becoming more of a problem. Second, merely burning waste can pollute the atmosphere and cause acid rain. Current reprocessing technology should be employed to process medical waste for effective utilization. What was needed before the present invention was a device to disinfect or destroy the infectious potential of medical waste and to dispose of it in a manner harmless to health care workers, waste handlers, and the public at large. BRIEF SUMMARY AND OBJECTS OF THE INVENTION The present invention provides a device for processing medical materials, such as medical and veterinary waste and medical products, which disinfects or sterilizes the material by a combination of heating and gamma radiating. The device comprises a source of heat (for example, a source of radio-frequency waves) to raise the internal temperature of medical materials to at least about 60.degree. C., which is sufficient to inactivate most viruses. The device further comprises a source of gamma irradiation which applies a reduced dose of gamma irradiation to the medical materials to complete the disinfection or sterilization process by inactivating other microorganisms, mostly bacteria. The invention additionally comprises an apparatus for further processing of pre-sorted medical and veterinary waste either as recycled plastic or as refused-derived fuel. Therefore, in view of the foregoing, it is a primary object of the present invention to disinfect medical materials by heating the materials and exposing them to gamma radiation. A further object of the invention is to dispose of medical and veterinary waste in an environmentally safe manner. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be obtained by means of the devices and combinations particularly pointed out in the appended claims.

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