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050948032	claims	1. A steam generator utilized for a liquid-metal coolant reactor comprising: an outer body shell of hollow cylindrical structure provided with a water inlet chamber disposed at a lower portion of the body shell, an outlet steam chamber disposed at an intermediate portion of the body shell, and a liquid metal inlet portion disposed at an upper portion of the body shell; a heat transfer tube arranged in an annular space formed by an inner wall of the body shell so as to connect said water inlet chamber and said outlet steam chamber; a liquid metal outlet rising pipe axially extending along substantially a central portion of said body shell and an electromagnetic pump arranged at an upper portion inside said liquid metal outlet rising pipe; said electromagnetic pump comprising a hollow cylindrical iron core provided with a comb-shaped portion at an outer peripheral surface thereof and an annular stator coil assembled in the comb-shaped portion of the cylindrical iron core, a main passage of liquid metal being formed on a side on which said stator coil of the iron core is assembled, a cooling bypass passage being formed at substantially the central portion of said cylindrical iron core in a vertically penetrating fashion; and wherein said cylindrical iron core comprises an inner iron core portion and an outer iron core portion disposed proximate an outer peripheral surface of said inner iron core portion with a concentric space formed therebetween and said coil is assembled in an outer peripheral surface of said inner iron core portion and in an inner peripheral surface of said outer iron core portion. 2. A steam generator according to claim 1, further comprising additional cooling bypass passages formed at a central portion of said inner iron core portion and on an outer peripheral side of said outer iron core portion. 3. A steam generator according to claim 1, further comprising a reaction pressure suppressing cylinder disposed outside of said outlet rising pipe concentrically therewith with a space formed therebetween for the communication of liquid metal, and a reaction pressure releasing pipe arranged in association with said reaction pressure suppressing cylinder.
051805480	claims	1. A mixing grid for a nuclear fuel assembly, the grid comprising at least two sets of crossed plates fixed together at their cross-points and defining cells distributed in a regular array, some for receiving fuel rods and the others for receiving guide tubes, the plates being provided with coolant stirring fins extending the plates downstream and disposed to deflect the coolant transversely to its general flow direction, each plate being provided with abutment means projecting inwardly from each of the sides of those cells which are to receive fuel rods, thereby defining a passage that is larger than the size of the rods but small enough to prevent a rod contained in the cell coming into contact with the fins, wherein said abutment means comprise, in each plate separating two cells other than peripheral which receives a rod, two portions of said plate that are cut out and deformed into two scoops, and that are mutually offset in the coolant flow direction, said scoops projecting in mutually opposite directions and tending to cause coolant to pass from one cell to another across said plate. 2. A grid according to claim 1, wherein the scoops are formed by pressing out zones of the plates which are approximately semicircular and open either to an edge of the plate or to a slot formed in the plate transversely to the flow direction. 3. A grid according to claim 2, wherein the scoops are in the shape of truncated cone halves. 4. A grid according to claim 1, wherein two said mutually offset scoops occupy a fraction only on the width of the respective plate. 5. A grid according to claim 1, wherein the two mutually offset scoops have respective semicircular bases on their downstream sides and wherein the dowstream scoop is defined by a slot cut out in the plate while the upstream scoop is terminated by a deformed portion of the upstream edge of the plate, the downstream scoop projecting in a direction with respect to the plate which is opposite to the direction into which a fin carried by the same wall of the cell is sloped. 6. A grid according to claim 1, wherein the downstream scoop of said mutually offset scoops opens in the direction opposite to that of the upstream scoop and extends up to the downstream edge of the plate, the downstream scoop projecting from the plate in the direction opposite to the direction into which a fin carried by the same wall of the cell is sloped. 7. A grid according to claim 1, devoid of peripheral belt, wherein the plates are of such a length that they have an envelope smaller than the envelope of the fuel cells in the assembly, and wherein the walls separating the outermost cells include abutment means projecting from that side of the plate towards which a fin of the respective cell is sloped. 8. A nuclear fuel assembly having a bundle of mutually parallel fuel elements and a support structure including guide tubes and a plurality of grids, wherein each one of only some of said grids comprise at least two sets of crossed plates fixed together at their cross-points and defining cells distributed in a regular array, some for receiving fuel rods and the others for receiving guide tubes, the plates being provided with coolant stirring fins extending the plates downstream and disposed to deflect the coolant transversely to its general flow direction, each plate being provided with abutment means projecting inwardly from each of the sides of those cells which are to receive fuel rods, thereby defining a passage that is larger than the size of the rods but small enough to prevent a rod contained in the cell coming into contact with the fins, wherein said abutment means comprise, in each plate separating two cells other than peripheral which receives a rod, two portions of said plate that are cut out and deformed into two scoops, and that are mutually offset in the coolant flow direction, said scoops projecting in mutually opposite directions and tending to cause coolant to pass from one cell to another across said plate. 9. A mixing grid for a nuclear fuel assembly, said mixing grid comprising two sets of crossed plates fixed together at their cross-points and defining cells distributed in a regular array, some of said cells for receiving fuel rods and the others for receiving guide tubes, wherein said plates are formed with coolant mixing fins extending the plates on their downstream side and angularly disposed with respect to said plates to deflect coolant transversely to its general flow direction along the fuel rods; wherein each of said plates further comprises abutment means projecting inwardly from each of the sides of those cells which are to receive fuel rods by such amounts that they define in each said cell a passage that is larger than the size of the rod but small enough to prevent the rod contained in the cell from coming into contact with the respective fins; and wherein said abutment means comprise, in each portion of one of said plates which separates two cells which each receives one fuel rod, except peripheral cells, two cut out portions of said plate mutually offset in the coolant flow direction, projecting in mutually opposite directions and forming scoops having mutually confronting openings separated by a slot formed in the plate transversely to the general coolant flow direction. 10. A mixing grid according to claim 9, wherein each of said scoops merges with a current portion of the respective plate along a semi-circular line.
	abstract	An extreme ultraviolet light generation apparatus may be configured to generate extreme ultraviolet light by irradiating a target with a pulse laser beam outputted from a laser apparatus to generate plasma. The extreme ultraviolet light generation apparatus may include a chamber; a target supply device configured to supply a target to a plasma generation region inside the chamber; a target sensor located between the target supply device and the plasma generation region and configured to detect the target passing through a detection region; and a shield cover disposed between the detection region and the target supply device, having a through-hole that allows the target to pass through, and configured to reduce pressure waves that reach the target supply device from the plasma generation region.
	description	This is a continuation application based on application Ser. No. 12/659,261, filed Mar. 2, 2010, now U.S. Pat. No. 7,821,714, the entire contents of which is hereby incorporated by reference. 1. Field Embodiments relate to a method of manufacturing a semiconductor device. More particularly, embodiments relate to an apparatus and a method of measuring a defect of a mask used to form a fine pattern during a scanning process employable during manufacturing a semiconductor device. 2. Description of the Related Art Recently, as illumination light sources having shorter wavelengths are needed to further miniaturize the line width of a semiconductor circuit, research into a scanning process using an extreme ultra-violet (EUV) having a wavelength of 50 nm or less as a scanning light source has been actively performed. Since the complexity of a scanning process has gradually increased, even a small defect in a mask may cause a serious defect in a circuit pattern on a wafer. Thus, when a pattern is formed on a wafer by using a photomask, in order to identify in advance the influence of various defects formed in the photomask on the wafer, defects of the photomask are detected by measuring the aerial image of the photomask. A conventional apparatus for measuring an aerial image of a EUV mask includes a plurality of EUV mirrors. Thus, the manufacture and installation of the mirrors require use of various technologies. In addition, many mirrors are used because the reflection rate of one mirror is not 100%. Thus, a high power source is required. Accordingly, such conventional apparatus for measuring an aerial image of a EUV mask is expensive, and additionally, a long development period is necessary for making the apparatus. Embodiments are therefore directed to an apparatus for and a method of measuring a defect in a mask, which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. It is therefore a feature of an embodiment to provide an apparatus for and a method of measuring a defect in a mask employable for forming a fine pattern during a scanning process employable during manufacturing a semiconductor device. It is therefore another feature of an embodiment to provide an apparatus for measuring an aerial image of an extreme ultra-violet (EUV) mask, wherein the apparatus is capable of perfectly emulating a numerical aperture (NA) and off-axis degree (σ) of a scanner although the overall complexity and required technological level thereof may be simplified and/or reduced as compared to comparable conventional devices. It is therefore a separate feature of an embodiment to provide an apparatus for measuring an aerial image of a EUV mask, wherein the apparatus may have a shorter development period and/or lower development cost than a comparable conventional apparatus for measuring an aerial image of a EUV mask. At least one of the above and other features and advantages may be realized by providing an apparatus for measuring an aerial image, the apparatus including a movable unit adapted to move a reflective extreme ultra-violet (EUV) mask disposed thereon in an x-axis and/or y-axis direction, an X-ray mirror arranged on the movable unit, the X-ray mirror being adapted to selectively reflect a coherent EUV light having a selected wavelength, a zoneplate lens that is located between the movable unit and the X-ray mirror, the zoneplate lens being adapted to focus the coherent EUV light on a portion of the reflective EUV mask, and a detector arranged on the movable unit, the detector being adapted to sense energy of the reflected coherent EUV light when the focused coherent EUV light is reflected by the portion of the reflective EUV mask, wherein NAzoneplate=NAscanner/4 and NAdetector=NAscanner/4σ, where NAzoneplate denotes a numerical aperture (NA) of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of a scanner, and σ denotes an off-axis degree of the scanner. An aperture may be between the reflective EUV mask and the detector. The X-ray mirror may include a multi-layer structure including at least one molybdenum layer and at least one silicon layer, which are alternately arranged. The EUV light generator may include a high power femtosecond laser adapted to output a high power femtosecond laser beam, a gas cell adapted to generate the coherent EUV light having a selected wavelength from the high power femtosecond laser, and a lens adapted to focus the high power femtosecond laser beam on the gas cell. The gas cell may be filled with a neon gas so as to optimize a production efficiency of a coherent EUV light having a wavelength of 13.5 nm. The X-ray mirror may be adapted to reflect the coherent EUV light emitted from the EUV light generator toward the portion of the reflective EUV mask at an angle of about 4° to about 8° with respect to a normal line of the reflective EUV mask. The zoneplate lens may be adapted to focus the reflected coherent EUV light on the portion of the reflective EUV mask at an angle of about 4° to about 8° with respect to a normal line of the reflective EUV mask. The apparatus may include a computing unit adapted to reconstruct an image of the reflective EUV mask based on energy sensed by the detector. At least one of the above and other features and advantages may be separately realized by providing an apparatus for measuring an aerial image of a pattern corresponding to a semiconductor pattern to be formed by scanning the pattern using a scanner, the apparatus including an extreme ultra-violet (EUV) mask including the pattern, a zoneplate lens arranged on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on a second side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NAzoneplate=NAscanner/n and NAdetector=NAscanner/nσ, where NAzoneplate denotes a NA of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of the scanner, σ denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner. The apparatus may include a movable unit on which the EUV mask is arranged, the movable unit being adapted to move the EUV mask in an x-axis direction and/or an y-axis direction. The EUV mask may be a reflective EUV mask including a reflective material. The detector may be adapted to sense energy of reflected EUV light that is reflected from the reflective EUV mask. The apparatus may include an EUV light generator and an X-ray mirror adapted to selectively reflect the EUV light from the EUV light generator. The EUV light generator may include a high power femtosecond laser. The EUV mask may be a transmissive EUV mask. The detector may be adapted to sense energy of transmitted coherent EUV light that is transmitted through the transmissive EUV mask. At least one of the above and other features and advantages may be separately realized by providing a method of measuring an aerial image of a pattern corresponding to a semiconductor pattern to be formed by scanning the pattern using a scanner, the method including generating extreme ultra-violet (EUV) light, reflecting the generated EUV light using an X-ray mirror, transmitting the reflected EUV light from the X-ray mirror using a zoneplate lens toward the pattern on an EUV mask, sensing energy of the EUV light from the EUV mask using a detector, converting the sensed energy into image information and storing the image information, moving the EUV mask in an x-axis direction and/or a y-axis direction, and outputting the aerial image of the pattern of the EUV mask based on the stored image information, wherein NAzoneplate=NAscanner/4 and NAdetector=NAscanner/4σ, where NAzoneplate denotes a numerical aperture (NA) of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of a scanner, and σ denotes an off-axis degree of the scanner. Generating extreme ultra-violet (EUV) light may include generating a high power femtosecond laser beam. Reflecting the generated EUV light using an X-ray mirror may include reflecting the EUV light emitted from an EUV light generator toward a portion of the EUV mask at an angle of about 4° to about 8° with respect to a normal line of the EUV mask. Transmitting the reflected EUV light from the X-ray mirror using a zoneplate lens may include transmitting the EUV light reflected from the X-ray mirror toward a portion of the EUV mask at an angle of about 4° to about 8° with respect to a normal line of the EUV mask. Korean Patent Application No. 10-2009-0049097, filed on Jun. 3, 2009, in the Korean Intellectual Property Office, and entitled: “Apparatus and Method for Measuring Aerial Image of EUV Mask,” is incorporated by reference herein in its entirety. Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. FIGS. 1 and 2 illustrate schematic diagrams of an exemplary embodiment of an apparatus employable for measuring an aerial image. Referring to FIG. 1, the apparatus for measuring an aerial image may include a reflective extreme ultra-violet (EUV) light generation unit 10, an X-ray mirror 20, a zoneplate lens 30, a reflective EUV mask 40 (hereinafter referred to as a “mask”), a detector 50, and a computing unit 60. The EUV light generation unit 10 may generate EUV light having a wavelength about 12 nm to about 14 nm. The EUV light may be coherent EUV light. The EUV light may be reflected by the X-ray mirror 20 and may move toward the zoneplate lens 30. The X-ray mirror 20 may selectively reflect the EUV light having a wavelength of about 12 nm to about 14 nm. The reflected EUV light may be focused on a portion 45 of the mask 40 through the zoneplate lens 30. The EUV light focused on the portion 45 may be reflected to the detector 50 by the mask 40. The detector 50 may sense energy of the EUV light and may transfer energy information to the computing unit 60. The X-ray mirror 20 may include palladium (Pd)/carbon (C) and molybdenum (Mo)/silicon (Si). In some embodiments, the X-ray mirror 20 may include, e.g., a Mo/Si multi-layer structure including 80 Mo and Si layers, wherein the Mo layers and Si layers may be alternately formed. The Mo layers and the Si layers may be thin films formed by sputtering. The X-ray mirror 20 may selectively reflect EUV light having a wavelength of about 13.5 nm. The mask 40 may include a reflective material. The mask 40 may include an upper portion with a fine circuit pattern having a size of about 45 nm or less. The apparatus for measuring an aerial image may further include an aperture 46 for transmitting the EUV light reflected by the mask 40. The aperture 46 may include pinholes 47. A numerical aperture of the zoneplate lens 30 may be controlled by changing a hole size of the pinholes 47. Referring to FIG. 2, the EUV light generation unit 10 may include a light source 11, a lens 12, and a gas cell 13. The light source 11 may generate a high power femtosecond laser beam. The high power femtosecond laser may be a Ti:Sapphire laser outputting a wavelength of about 800 nm and may be focused on the gas cell 13 through the lens 12. The gas cell 13 may be evacuated and may include fine pores for allowing a laser to pass therethrough. The gas cell 13 may be filled with neon gas to improve and/or optimize generation efficiency of the EUV light with a wavelength of 13.5 nm. The X-ray mirror 20 may be arranged such that the generated EUV light may be incident on the portion 45 of the mask 40 at a same angle as an incident angle at which a scanner is disposed with respect to a normal line of the mask 40. The zoneplate lens 30 (see FIG. 1) may perform a same function as the X-ray mirror 20. That is, the zoneplate lens 30 may be arranged such that the EUV light reflected by the X-ray mirror 20 may be incident on the portion 45 of the mask 40 at the same angle as the incident angle at which a scanner may be disposed with respect to a normal line of the mask 40. In some embodiments, the incident angle of the scanner may be in a range of about 4° to about 8°, e.g., 6°. In such embodiments, the X-ray mirror 20 may be arranged such that the generated EUV light may be incident on the portion 45 of the mask 40 at an angle of, e.g., 6°, with respect to a normal line of the mask 40. Instead of the X-ray mirror 20, the zoneplate lens 30 may be arranged such that the EUV light reflected by the X-ray mirror 20 may be incident on the portion 45 of the mask 40 at an angle of 6° with respect to the normal line of the mask 40. In some embodiments, the apparatus for measuring an aerial image may include a movable unit 35 arranged adjacent, e.g., under, the mask 40. The movable unit 35 may move the mask 40 along an x-axis and/or y-axis direction, and may allow the detector 50 to scan an entire upper surface of the mask 40. FIG. 3A illustrates a schematic diagram of an exemplary embodiment of a zoneplate lens 30a and a detector 50a employable in an apparatus for measuring an aerial image, and FIG. 3B illustrates a schematic diagram of an exemplary embodiment of a scanner employable in an apparatus for measuring an aerial image. In the exemplary embodiment of an apparatus for measuring an aerial image illustrated in FIGS. 1 and 2, the mask (see 40 of FIGS. 1 and 2) reflects the EUV light toward the detector (see 50 of FIGS. 1 and 2). It should be understood that embodiments are not limited thereto. For example, as shown in FIG. 3A, a mask 40a may transmit EUV light toward the detector 50a. In a EUV scanning process, EUV light may be reflected and/or transmitted by a mask and the reflected/transmitted EUV light may be projected with reduction magnification on a photoresist on a surface of a wafer. For example, a size ratio of a pattern formed on a mask, e.g., 40, 40a, of a scanner to an entity pattern formed by projecting EUV light on the surface of the wafer by the scanner may be in range of about 4:1 to about 5:1. The size ratio of the pattern formed by projecting EUV light by the scanner, i.e., a reduction ratio may be used to control a numerical aperture of the zoneplate lens, e.g., 30, 30a, and the detector, e.g., 50, 50a. In embodiments, to emulate the pattern formed by projecting EUV light by the scanner, the numerical aperture of the detector, e.g., 50, 50a, may be controlled in consideration of an off-axis degree of the scanner. Referring to FIG. 3A, a relationship between the zoneplate lens 30a, the detector 50a, and the scanner may be represented by Equation 1. NA zoneplate = NA scanner n ⁢ ⁢ NA detector = NA scanner n σ [ Equation ⁢ ⁢ 1 ] In Equation 1, NAzoneplate denotes the numerical aperture (NA) of the zoneplate lens 30a, NAdetector denotes the NA of the detector 50a, and NAscanner denotes the NA of the scanner, σ denotes the off-axis degree of the scanner, and n denotes a reduction magnification of the scanner. Referring to FIG. 3B, a relationship between the NAscanner and σ may be represented by Equation 2. NA scanner = sin ⁢ ⁢ y ⁢ ⁢ σ = sin ⁢ ⁢ x sin ⁢ ⁢ y Equation ⁢ ⁢ 2 In Equation 2, x denotes an angle formed by EUV light focused by a focusing lens 41 of the scanner with respect to a center of the focusing lens 41 and y denotes an angle formed by EUV light that is reflected toward a focusing mirror 42 by the mask 40 with respect to a center of the focusing mirror 42. More particularly, e.g., in an exemplary embodiment of the mask 40a, the zoneplate lens 30a and the detector 50a of FIG. 3A, a size ratio of a pattern formed in the mask 40a to the entity pattern formed by focusing and projecting EUV light on a surface of the wafer by the scanner may be 4:1. In such an embodiment, because the reduction magnification of the scanner is 4, NAscanner and σ may be calculated using Equation 2, and the zoneplate lens 30a and the detector 50a may designed such that Equation 1 in which NAzoneplate=NAscanner/4 and NAdetector=NAscanner/4σ is satisfied. Thus, referring, e.g., to FIG. 3A, embodiments of an apparatus for measuring an aerial image may be formed in consideration of a coherent EUV light, an incident angle 25 of the coherent EUV light that is set to be incident to a portion of the mask 40a at a same angle as an incident angle of a scanner with respect to a normal line of the mask 40a, and numerical apertures of the zoneplate lens 30a and the detector 50a (NAzoneplate and NAdetector) which may be set to satisfy Equation 1. Embodiments of the apparatus for measuring an aerial image formed as described above may substantially and/or perfectly emulate the numerical aperture and off-axis degree of a scanner. Thus, when the mask 40a is a reflective EUV mask including an upper portion having a circuit pattern, an aerial image that is identical to a circuit pattern projected, by the scanner, on a photoresist of a wafer may be measured using embodiments of an apparatus for measuring an aerial image including one or more features described herein. FIG. 4A illustrates a schematic diagram of an exemplary embodiment of the computing unit 60 employable in the apparatus of FIG. 1, and FIG. 4B illustrates a schematic diagram of an exemplary embodiment of a driving process of the detector 50 and the computing unit 60 employable in the apparatus of FIG. 1. Referring to FIG. 4A, the computing unit 60 may include a control unit 70, a storage unit 80, and an output unit 90. When EUV light 100 is reflected by the portion 45 of the mask 40 and energy of the reflected EUV light 100 is detected by the detector 50, an energy information 200 may be transferred to the control unit 70. The control unit 70 may reconstruct an image using the transferred energy information 200. The reconstructed image information 300 may be represented on a scale of 0 to 1 corresponding to the light intensity of the EUV light 100. The reconstructed image information 300 may be transferred to the storage unit 80. The storage unit 80 may store the reconstructed image information 300 about the portion 45 of the mask 40 in the form of a matrix data 400. For example, if the mask 40 is divided in regions (5×5), reconstructed image information about the respective regions may be stored using a matrix data (5×5). The control unit 70 may load the matrix data 400 stored in the storage unit 80. The control unit 70 may transmit the matrix data 400 to the output unit 90. The output unit 90 may output the aerial image of the mask 40 using the transmitted matrix data 400. More particularly, referring to FIG. 4B, the mask 40 may be divided, e.g., into 25 regions. Further, e.g., EUV light may be reflected in a first region 1, and the detector 50 may sense an energy of the reflected EUV light and transmit first energy information 110 to the computing unit 60. Using the transmitted first energy information 110, the control unit 70 of the computing unit 60 may reconstructs the image of the first region 1 of the mask 40. Reconstructed first image information 110′ of the first region may be transmitted to the storage unit 80. The storage unit 80 may store the reconstructed first image information 110′ in a region (1×1) of the matrix data 400 (5×5). Then, the movable unit 35 may move the mask 40 in a -x-axis direction. EUV light may then be reflected in a second region 2 of the mask 40, and the detector 50 may sense an energy of the reflected EUV light and may transmit second energy information 120 to the computing unit 60. Using the transmitted second energy information 120, the control unit 70 of the computing unit 60 may reconstruct the image of the second region 2 of the mask 40. Reconstructed second image information 120′ of the second region may be transferred to the storage unit 80. The storage unit 80 may store the reconstructed second image information 120′ in a region (1×2) of the matrix data 400. Then, the movable unit 35 may move the mask 40 in the -x-axis direction. In the exemplary embodiment illustrated in FIG. 4B, such operation may be repeated until an image of a fifth region of the mask 40 is reconstructed and the reconstructed fifth image is stored in the matrix data 400 of the storage unit 80. Then, the movable unit 35 may move the mask 40 in a +y-axis direction. EUV light may then be reflected in a sixth region 6 of the mask 40, and sixth energy information 160 may be generated by the detector 50. The sixth energy information 160 may be transmitted to the computing unit 60. The transmitted sixth energy information 160 may be reconstructed in the control unit 70, and reconstructed sixth image information 160′ of the sixth region may be transmitted to the storage unit 80 and stored in a region (2×5) of the matrix data 400. The images of the 25 regions of the mask 40 may be reconstructed by moving the mask 40 in the x-axis or y-axis, and respectively storing the reconstructed images in the matrix data 400 of the storage unit 80. When the reconstructed image information about the entire region of the mask 40 is stored in the storage unit 80, the control unit 70 may load the matrix data 400 of the storage unit 80. The output unit 90 may then output the aerial image of the mask 40 using the matrix data 400 loaded from the control unit 70. FIG. 5 illustrates a perspective view of an exemplary embodiment of the EUV mask 40 including a mask pattern 500 and a defect 600 thereon. FIG. 6 illustrates an exemplary output image corresponding an aerial image of the mask 40 of FIG. 5, which may be output by the output unit 90 (see FIG. 4B) in the form of light and darkness using the values of the transmitted matrix data (see 400a of FIG. 5). FIG. 7 illustrates exemplary cross-sectional aerial images of diagrams that may be output by the output unit 90 (see FIG. 4B), wherein the cross-sections are taken along lines a-a′, b-b′, and c-c′ of FIG. 5. Referring to FIGS. 5, 6 and 7, operations of the control unit for reconstructing an image and the output unit 90 for outputting an aerial image of the mask 40 are described below. Based on the reconstructed image, it may be determined whether a defect, e.g., 600, exists in a mask pattern 500. Referring to FIG. 5, the exemplary embodiment of the mask 40 may be divided into 36 regions and the images of the 36 regions of the mask 40 may be reconstructed by moving the mask 40 in the x-axis and y-axis directions. The reconstructed respective image information may be stored in the matrix data 400a (3×12) of the storage unit 80 (See FIG. 4B). In the exemplary embodiment of FIG. 5, with regard to a first region 1 of the mask 40, energy of most and/or all incident EUV light may be reflected from the first region 1 and may be sensed by the detector, e.g., 50 of FIG. 4B. Thus, in a corresponding region (1×1) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 (FIG. 4B) based on a first energy information generated by the detector 50 with regard to the first region 1 may have a value of ‘1’. More particularly, the control unit 70 may transmit the value ‘1’ to the storage unit 80 and the value ‘1’ may be stored in the corresponding region (1×1) of the matrix data 400a. The movable unit 35 may then move the mask 40 in the −x-axis direction. EUV light may then be irradiated to a second region 2 of the mask 40. Referring to FIGS. 4B and 5, with regard to the second region 2, energy of most and/or all incident EUV light may be reflected from the second region 2 and may be sensed by the detector 50. Thus, in a corresponding region (1×2) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a second energy information generated by the detector 50 with regard to the second region 2 may have a value of ‘1’. More particularly, the control unit 70 may transmit the value ‘1’ to the storage unit 80 and the value ‘1’ may be stored in the corresponding region (1×2) of the matrix data 400a. The movable unit 35 may then move the mask 40 in the −x-axis direction. EUV light may then be irradiated to a third region 3 of the mask 40. Referring to FIGS. 4B and 5, with regard to the third region 3, energy of most and/or all incident EUV light may be reflected from the third region 3 and may be sensed by the detector 50. Thus, in a corresponding region (1×3) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a third energy information generated by the detector 50 with regard to the third region 3 may have a value of ‘1’. More particularly, the control unit 70 may transmit the value ‘1’ to the storage unit 80 and the value ‘1’ may be stored in the corresponding region (1×3) of the matrix data 400a. The movable unit 35 may move the mask 40 in the −x-axis direction. EUV light may then be irradiated to a fourth region 4 of the mask 40. Referring to FIGS. 4B and 5, with regard to the fourth region 4, energy of about 50% of all incident EUV light may be absorbed by the mask pattern 500 and about 50% may be reflected from the fourth region 4, and may be sensed by the detector 50. Thus, in a corresponding region (1×4) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a fourth energy information generated by the detector 50 with regard to the fourth region 4 may have a value of ‘0.5’. More particularly, the control unit 70 may transmit the value ‘0.5’ to the storage unit 80 and the value ‘0.5’ may be stored in the corresponding region (1×4) of the matrix data 400a. The movable unit 35 may move the mask 40 in the −x-axis direction. EUV light may then be irradiated to a fifth region 5 of the mask 40. Referring to FIGS. 4B and 5, with regard to the fifth region 5, energy of about 100% of all incident EUV light may be absorbed by the mask pattern 500 and about 0% may be reflected from the fifth region 5, and may be sensed by the detector 50. Thus, in a corresponding region (1×5) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a fifth energy information generated by the detector 50 with regard to the fifth region 5 may have a value of ‘0’. More particularly, the control unit 70 may transmit the value ‘0’ to the storage unit 80 and the value ‘0’ may be stored in the corresponding region (1×5) of the matrix data 400a. The operations described above may be repeated until EUV light is irradiated to each of a sixth through twelfth regions of the mask 40, and the corresponding energy information of the EUV light is reconstructed. In such embodiments, at this stage, the image information of the first through twelfth regions of the mask 40 may be stored in regions (1×1, 1×2, . . . , 1×12) of the matrix data 400a. Then, in such embodiments, e.g., the movable unit 35 may move the mask 40 in the +y-axis direction. EUV light may then be irradiated to a 13th region 13 of the mask 40. Referring to FIGS. 4B and 5, with regard to the 13th region 13, energy of about 50% of all incident EUV light may be absorbed by the mask pattern 500 and about 50% may be reflected from the 13th region 13, and may be sensed by the detector 50. Thus, in a corresponding region (2×12) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a thirteenth energy information generated by the detector 50 with regard to the thirteenth region 13 may have a value of ‘0.5’. More particularly, the control unit 70 may transmit the value ‘0.5’ to the storage unit 80 and the value ‘0.5’ may be stored in the corresponding region (2×12) of the matrix data 400a. The movable unit 35 may then move the mask 40 in the +x-axis direction. Likewise, EUV light may be irradiated to 14th through 24th regions of the mask 40 and the control unit 70 may respectively reconstruct energy information of EUV light reflected from each of the respective regions. The reconstructed 14th through 24th image information may be stored in regions (2×11, 2×10 through 2×1) of the matrix data 400a. Further, e.g., with regard to the 17th region 17, a portion of EUV light may be absorbed by the defect 600 of the mask pattern 500. Referring to FIGS. 4B and 5, when EUV light is irradiated to the 17th region 17 of the mask 40, Referring to FIGS. 4B and 5, energy of about 20% of all incident EUV light may be absorbed by the defect 600 and about 80% may be reflected from the 17th region 17, and may be sensed by the detector 50. Thus, in a corresponding region (2×8) of the matrix data 400a, corresponding image information reconstructed by the control unit 70 based on a seventeenth energy information generated by the detector 50 with regard to the seventeenth region 17 may have a value of ‘0.8’. More particularly, the control unit 70 may transmit the value ‘0.8’ to the storage unit 80 and the value ‘0.8’ may be stored in the corresponding region (2×8) of the matrix data 400a. When the respective image information about the 13th through 24th regions of the mask 40 is reconstructed and stored in the corresponding regions (2×9 through 2×1) the matrix data 400a of the storage unit, the movable unit 35 may move the mask 40 in the +y-axis direction. EUV light may then be irradiated to 25th through 36th regions of the mask 40 and the control unit 70 may reconstruct respective energy information of EUV light reflected from the respective regions. The reconstructed 25th through 36th image information may be stored in regions (3×1 through 3×12) of the matrix data 400a of the storage unit 80. The matrix data 400a stored in the storage unit 80 may be transmitted to the output unit 90. The output unit 90 may output the corresponding aerial image in the form of, e.g., light and darkness and/or in the form of a cross-sectional view based on the values of the matrix data 400a. Referring to FIG. 6, the output unit 90 may output the corresponding aerial image of the mask 40 in the form of light and dark regions, e.g., 36 regions, based on the respective values of the transmitted matrix data (see 400a of FIG. 5). For example, according to the values of the matrix data 400a, 0 may be output as black, 1 may be output as white, 0.5 may be output as gray, and 0.8 may be output as gray, with darkness of gray decreasing as the value approaches 1. When the aerial image of the mask 40 is output according to the corresponding matrix data (see 400a of FIG. 5), it may be determined whether a defect, e.g., defect 600, has occurred or not. In the exemplary embodiment of FIGS. 5-7, the defect 600 is present. Referring to the exemplary aerial image of FIG. 6, with regard to the aerial image of the exemplary mask 40 illustrated therein, the first through 12th regions repeat a pattern unit 510 (1-1-1-0.5-0-0.5), and thus it may be expected that scanning can be performed without any problem. The 19th through 24th (14→24) regions also have the pattern unit 510, and the 25th through 36th regions have two of the pattern unit 510, and thus it may be expected that scanning can be performed without any problem. However, the 13th through 18th regions have a defective pattern unit 520 (1-0.8-1-0.5-0-0.5) including a defect 550, corresponding to the defect 600 (see FIG. 5) of the 17th region 17. Thus, it may be expected that a defect may be formed in a photoresist when developed after scanning. Referring to FIG. 7, the output unit 90 (see FIG. 4B) may output aerial images of the mask 40 based on the values of the corresponding transmitted matrix data (see 400a of FIG. 5). In FIG. 7, the exemplary aerial images are cross-sectional views along lines a-a′, b-b′, and c-c′ of FIG. 5. For example, the output unit 90 may output the aerial image of a portion of the mask taken along line a-a′ based on values of regions along a first row of the matrix data (see 400a of FIG. 5). Likewise, the aerial images of portions of the mask taken along lines b-b′ and c-c′ may be output based on values of the second and third rows of the matrix data (see 400a of FIG. 5). Referring to FIGS. 5, 6 and 7, the a-a′ cross-section (first through 12th regions), and the c-c′ cross-section (25th through 36th regions) may each include two of a pattern unit 610 (1-1-1-0.5-0-0.5), and thus, it may be expected that scanning (13th may be performed without any problem. With regard to the b-b′ cross-section through 24th regions), the 19th through 24th regions may include the pattern unit 610 (1-1-1-0.5-0-0.5), and thus, it may be expected that scanning may be performed without any problem. However, the 13th through 18th regions may include a defective pattern unit 620 (1-0.8-1-0.5-0-0.5) including a defect 650 of the 17th region, and thus, it may be expected that a defect may be formed in a photoresist developed after scanning. In some embodiments, the output unit 90 may output aerial images that are symmetric to the aerial images described above with respect to an x-axis, and thus, an expected image of a photoresist pattern on a wafer that is developed after scanning, not the aerial image of the mask, may be obtained. FIGS. 8A and 8B each illustrate a cross-sectional view of an image projected onto a photoresist and a corresponding aerial image of a mask reconstructed by an output unit of an apparatus for measuring an aerial image according to another embodiment of the inventive concept, wherein the aerial image shows a cross-sectional view of the mask. Referring to FIG. 8A, in an exemplary embodiment, NAscanner is 0.25 and σ is 0. Thus, the zoneplate lens 30 and the detector 50 (see, e.g., FIG. 1) of the apparatus for measuring an aerial image may be designed in consideration of numerical apertures obtained using Equation 1 (NAzoneplate=0.25/4=0.0625, and NAdetector=0). Referring to FIG. 8B, in an other exemplary embodiment, NAscanner is 0.25 and σ is 1. Thus, the zoneplate lens 30 and the detector 50 of the apparatus for measuring an aerial image may be designed in consideration of numerical apertures obtained using Equation 1 (NAzoneplate=0.25/4=0.0625, NAdetector=0.0625). Referring to FIGS. 8A and 8B, it may be seen that images 800a and 800b projected onto a respective photoresist are identical to aerial images 810a and 810b that are output using the apparatus (see, e.g., FIG. 1) for measuring an aerial image designed according to Equation 1, wherein the aerial images 800a, 800b, 810a and 810b illustrate cross-sectional views. Thus, an apparatus for measuring an aerial image employing one or more features described herein may emulate an image projected on a photoresist based on the numeric aperture and off-axis degree of a scanner. FIG. 9A illustrates an exemplary mask pattern 900 that includes a defect 910 and from which energy information may be obtained and supplied to the output unit of FIG. 4B. FIG. 9B illustrates an exemplary light aerial image, which may be output from, e.g., the output unit 90 of FIG. 4B, and FIG. 9C illustrates an exemplary dark aerial image, which may be output from the output unit 90 of FIG. 4B. Referring to FIG. 9A, in an exemplary embodiment, NAscanner is 0.25, and, according to Equation 1, NAzoneplate=NAscanner/4=0.0625. In the exemplary embodiment, because σ is 0.5, NAdetector=NAscanner/4σ=0.03125. As described above with regard to Equation 1 and Equation 2, in embodiments, a zoneplate lens, e.g., 30 of FIG. 1, and a detector, e.g., 50 of FIG. 1, may be designed according to NAzoneplate and NAdetector. In the exemplary embodiment of FIG. 9A, the mask 900 including the defect 910 having a size of 40 nm may be measured using an embodiment of apparatus for measuring an aerial image including one or more features described herein. Referring to FIGS. 9B and 9C, in corresponding light and dark aerial images of the mask 900, the defect 910 may appear white and black, respectively, a corresponding region 920 of the output image. In the exemplary embodiment of FIGS. 9A, 9B and 9C, the defect 910 affects 10% or more of the aerial image intensity. In some embodiments, whether a defect may be detected may be based on an extent of the defect. That is, e.g., in some embodiments, only defects affecting more than a predetermined amount of an aerial image intensity may be detected. In the exemplary embodiment of FIGS. 9A, 9B, and 9C, a defect affecting 10% or more of the aerial image intensity may be flagged. Thus, the defect 910 may be flagged as a defect, and the mask pattern 900 may be corrected, e.g., removed/filled, before the mask may be scanned, e.g., during a semiconductor fabrication process. That is, by employing a method or apparatus for detecting a defect accordingly a defect of a mask may be sensed and removed before the scanning. FIG. 10 illustrates a flowchart of an exemplary embodiment of a method of measuring an aerial image. Referring to FIG. 10, EUV light may be generated (S100), and the generated EUV light may be reflected by an X-ray mirror (S200). The X-ray mirror may be arranged such that the EUV light is incident on a portion of a mask at an angle of about 4° to about 8° with respect to a normal line of the mask. The reflected EUV light may be transmitted by a zoneplate lens (S300). The zoneplate lens may be arranged such that the EUV light is incident on a portion of the mask at an angle of about 4° to about 8° with respect to the normal line of the mask. The EUV light focused on the portion of the mask may be reflected by the mask including a reflective material (S400). The detector may sense energy of the EUV light reflected by the mask (S500). In embodiments, the zoneplate lens and the detector may be formed such that Equation 1 is satisfied. The sensed energy may be reconstructed in the form of image information represented as a numeric value, the numerical value of the image information may be stored in a matrix data of a storage unit (S600). Then, a movable unit may move the mask in an x-axis or y-axis direction (S700), and the operations described above may be repeatedly performed. When image information of an entire region of the mask is stored in the matrix data, the aerial image of the mask may be output by using the matrix data (S800). It will also be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout the specification. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept. 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” 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. It will be understood that, although the terms first, second, 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 the present inventive concept. Embodiments are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments of the present inventive concept. 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, the illustrations should not be construed as limited to the particular shapes of regions illustrated therein, but are to include deviations in shapes that result, for example, from manufacturing. For example, in the drawings used to describe the exemplary embodiments, the shapes of the respective components are for illustrative purposes only. The respective components may have various other shapes. Exemplary embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
	description	The invention relates to a method for modelizing the core of a nuclear reactor. Such a modelizing method is helpful to calculate neutron flux and/or thermohydraulics parameters within the core. The results of such a modelizing method can be used to prepare safety analysis reports before building and starting a reactor. These results can also be useful for existing nuclear reactors and especially for managing the nuclear fuel loaded therein. In particular, these results can be used to assess how the core design should evolve in time and decide of the positions of the fuel assemblies in the core, especially the positions of the fresh assemblies to be introduced in the core. Such modelizing methods are implemented by computers. To this end, the core is partitioned in cubes, each cube constituting a node of a grid for implementing a digital computation. In the state of the art methods, the cubes are numbered one after the other in a lexicographical order. In such methods, most of the computational efforts are concentrated in the part dedicated to the iterative solving of large sparse systems, which end up being either linear systems or eigensystems. When calculating thermohydraulics parameters, the system to be solved is a linear system and corresponds, in mathematical form, to a linear equation of the form:Ax=b (1) A typical whole nuclear core computation amounts to a sparse linear system being defined on the basis of between 150 and 200 fuel assemblies and typically several tens of thousands of cubes, meaning that a nontrivial computational effort is required for solving the associated algebraic systems. The actual structure of the matrix A is characterized by the systematic presence of diagonal elements plus a limited number of nonzero offdiagonal elements, which each represent interactions between a cube and the directly neighbouring cubes only. In other words, only interactions between cubes sharing common surfaces are considered. With a lexicographical grid, the few nonzero values [AD+ALD]ij, with AD and ALD being respectively the diagonal and lower diagonal part of A, represent the interaction of a cube i with itself and with directly neighbouring cubes j that have lower lexicographical indices, so with j≦i. In order to solve the above-mentioned linear equation, a Gauss-Seidel (GS) procedure is usually implemented, meaning that the matrix A is split into its diagonal AD plus lower-diagonal part ALD on the one hand and its upper-diagonal part AUD on the other hand:A=[AD+ALD]+AUD (2) With the diagonal plus lower-triangular part being easy to invert implicitly, the GS procedure amounts to the iteration:x(n+1)=[AD+ALD]−1(b−AUDx(n)) (3) which can and has been programmed very compactly and efficiently in the form:x(n+1)=[AD]−1(b−ALDx(n+1)−AUDx(n))=x(n)−r(n+1/2) (4)with r(n+1/2)=[AD]−1(b−[AD+ALD]x(n+1)−AUDx(n)), (5) according to which, during a new GS iteration, each update for cube i “profits” from already realized updates (during the same iteration) for its neighbours cubes that have lower lexicographical indices. As for the coupling with the remaining neighbours, i.e. the ones with higher lexicographical indices, other values must be used that emerged from previous GS iterations. The convergence speed of this GS procedure is usually accelerated by application of a systematic Successive Over-Relaxation (SOR) measure with relaxation factor ω, which amounts to the final implementation of:x(n+1)=x(n)−ωr(n+1/2) (6) Upon convergence, the residual r converges toward 0 and the iterant x converges toward the exact solution of the linear system. On a sequential basis, i.e. with the GS iteration being performed sequentially by a single processor, the performance of this GS/SOR procedure is certainly not bad. However, an important issue of concern in the currently implemented GS/SOR procedure is the highly sensitive dependence of computational performance on the choice of a value for the relaxation factor ω to be applied in the SOR scheme. Minor variations in the value for the relaxation factor ω have been found to lead to substantial differences in convergence speed, meaning that small departures from a typically empirically determined optimum will lead to heavy losses in computational efficiency. The relaxation factor ω is currently a parameter to be set by the user of the computer implementing the modelizing method. This user cannot be expected to be able to determine the optimum choice for the factor ω for each individual case of relevance. The value of this optimum choice may indeed depend on several parameters, like channel dimensions, material properties, temperature, etc., anything which determines the individual components of the matrix in the linear system to be solved. For a user, it is therefore not possible to predetermine shifts in this optimum choice depending on state changes. With the identified performance sensitivity, it can be expected that default values for the relaxation factor ω will, on average, lead to performance losses when applied as a fixed SOR parameter for different computational cases. Further, with the current GS procedure, the distribution of iterative workload on different processors would lead to a severe degradation of computational efficiency, even for low numbers of parallel processors, so that no major speed computation improvement could be obtained through parallelization. An object of the present invention is to solve the above-mentioned problems by providing a modelizing method which offers a better computational robustness and a better computational efficiency so that relevant core simulations can be obtained within short computational time period. The present invention provides a computer implemented method for modelizing a nuclear reactor core, comprising the steps of: partitioning the core in cubes (1B, 1R) to constitute nodes of a grid for computer implemented calculation, splitting the cubes into a first category (1R) and a second category (1B), each cube of the first category (1R) being adjacent only to cubes (1R) from the second category so that the first category and second category of cubes constitute a checkerboard-like pattern, ordering the cubes (1R) of the first category and then the cubes (1B) of the second category, calculating neutron flux and/or thermohydraulics parameters by using an iterative solving procedure of at least one linear system and/or an eigensystem, the components of an iterant of the linear system and/or the eigensystem constituting the neutron flux and/or thermohydraulics parameters to be calculated, wherein, during the iterative solving procedure, calculations are conducted on the cubes of the first category then on the cubes of the second category. The present invention also provides a computer program product residing on a computer readable medium and comprising a computer program means for running on a computer the method provided in the present invention. In the following description, the case of a pressurized water reactor (PWR) will be considered, but it should be kept in mind that the present invention applies to other types of nuclear reactors. In a first step of the computer implemented modelizing method according to the invention, the core of the reactor is partitioned in cubes as in the state of art methods. Each cube corresponds to a node of a grid or network 3 on which numerical computation will be implemented through the computer. In order to ease the representation, the grid is shown on FIG. 1 as being two-dimensional, but it should be kept in mind that the grid is actually three-dimensional in order to represent the whole core. According to a first aspect of the invention, the cubes are split into a first category and a second category. In the following description, the cubes 1R of the first category will be called the red cubes and the cubes 1B of the second category will be called the black cubes but no specific restrictive meaning should be associated with the words “black” and “red”. Each red cube 1R has only black cubes 1B as direct neighbours. Thus, most of the red cubes 1R have six direct black neighbours 1B. It should be understood by “direct” neighbours, the cubes sharing a common surface with the considered cube. Consequently, and as illustrated by FIG. 1, the grid has a visual analogy with respect to the dark and light regions of a checkerboard. Then, the cubes are numbered, starting for example by the red cubes 1R and ending by the black cubes 1B. In the following description, such a split of the cubes in two categories and the numbering of one category after the other will be referred to as red-black ordering. An advantage of a red-black ordering of the cubes in comparison with the state of the art lexicographical ordering is that, for a red cube 1R, all its direct neighbours will be black, and vice versa. In the following first embodiments of the description, a modelizing method will be implemented to calculate thermohydraulics parameters. The linear Equation (1), which the computer has to solve in order to calculate the thermohydraulics parameters of the core, can be written in the general, diagonally preconditioned form:(1+AND)x=b (7) The nondiagonal matrix AND is sparse, coupling red cubes 1R only to direct black neighbours 1B and vice versa. Thus, the red-black ordering enables the following convenient relationship between the red and the black parts of the equation: { x _ red + A ND ⁢ x _ black = b _ red x _ black + A ND ⁢ x _ red = b _ black ( 8 ) From a calculation point of view, the use of a red-black ordering means that, during an iterative solving procedure if, in the first half of an iteration, the red components xred of the iterant x are updated, then, during the second part of the iteration, all the black components xblack will be updated on the basis of the red components of their red neighbours xred. In other words, the value for each black cube 1B will be calculated on the basis of the values for all its direct red neighbours 1R. Thus, an iteration amounts to: ( 9 ) { x _ red ( n + 1 ) = b _ red - A ND ⁢ x _ black ( n ) x _ black ( n + 1 ) = b _ black - A ND ⁢ x _ red ( n + 1 ) ( 9 ) The use of a red-black ordering helps improving the computational efficiency. Indeed, FIG. 2 shows that the number of iterations would be higher for a state of the art method based on lexicographical ordering and using a GS procedure (curve 5) than for a method according to the invention based on a red-black ordering and using a GS procedure (curve 7). Indeed, and as previously stressed, if in the first half of the GS iteration the red components of the iterant x are updated, during the second part of the iteration all the black updates will receive co-updates from all of their red neighbours, instead of from only half of them like in the case of the lexicographical ordering. It is this particular property difference which explains the observed convergence speed difference between the two different orderings. The red-black ordering constitutes a first aspect of the present invention which can be used with various solving procedures. Such a red-black ordering proves to be especially useful when used with a particular solving procedure which constitutes a second aspect of the invention. This procedure is a particular highly robust stabilized Bi-Conjugate Gradient Stabilized (Bi-CGStab) procedure. An adequate introductory description of this procedure can be found in the following references: Y. Saad, “Iterative Methods for Sparse Linear Systems”, second edition, Society for Industrial and Applied Mathematics (SIAM) (2003); H. A. van der Vorst, “Bi-CGSTAB: a Fast and Smoothly Converging Variant of Bi-CG for the solution of nonsymmetric linear systems”, SIAM J. Sci. Stat. Comput. 13(2), pp. 631-644 (1992), The Bi-CGStab method is derived from a minimization principle for a functional of x, with given A and b, for which stationarity applies with regard to small variations δx around the specific optimum x which satisfies, exactly, the linear system Ax=b, and for which the functional assumes a minimum value. Thus, it is possible to define a solving procedure driven by the minimization of a functional rather than by more direct considerations on how to solve Ax=b efficiently. The Bi-CGStab procedure follows from such a minimization principle, where the successive changes in the iterant are organized such that each change in the functional (which is like a Galerkin-weighted integrated residual) is orthogonal with respect to all of the preceding changes. The particular Bi-CGStab procedure according to the second aspect of the invention is given below with solution vector x, solution residual r (with r=b−A x) and auxiliary vector r, s and p, and with initial solution estimate x0: 1. r 0 = b - A ⁢ ⁢ x 0 ; ⁢ r = r 0 2. p 0 = r 0 3. do ⁢ ⁢ i = 0 , 1 , … ⁢ , N 4. α i = ( r * , r i ) ( r * , A ⁢ ⁢ p i ) 5. s i = r i - α i ⁢ A ⁢ ⁢ p i 6. ω i = ( A ⁢ ⁢ s i , s i ) ( A ⁢ ⁢ s i , A ⁢ ⁢ s i ) 7. x i + 1 = x i + α i ⁢ p i + ω i ⁢ s i 8. r i + 1 = s i - ω i ⁢ A ⁢ ⁢ s i 9. β i = ( r * , r i + 1 ) ( r * , r i ) ⁢ α i ω i 10. p i + 1 = r i + 1 + β i + 1 ⁡ ( p i - ω i ⁢ A ⁢ ⁢ p i ) 11. end ⁢ ⁢ do ( 10 ) Typically, the Bi-CGStab method requires a preconditioner for it to offer good convergence behaviour. This means, for example, that both sides of the linear system are premultiplied by the so-called preconditioning matrix. This matrix can have an explicit form, like a diagonal preconditioner, or an implicit form, like an implicit approximated inverse of the system matrix A which offers a sufficiently adequate approximation for A−, which means sufficiently adequate for preconditioning purposes. Another way, which is adopted in the present embodiment and which constitutes the third aspect of the invention, is to rewrite or transform the original equation such that the matrix appearing on the left allows good preconditioning using only a simple inverted diagonal matrix, by making sure that the diagonal will be sufficiently dominant in the transformed form. Good preconditioners or good transformations typically manage to pre-include crucial information or the major part of that information, with regard to the physical interactions between nodes that determine the spatial couplings and hence the solution of the equation. The particular case under study here is no exception in that respect. With the specific form A=1+AND, applicable to the system to be solved iteratively, a direct red-black variant of the Bi-CGStab method, with Equation (7) applied, and no further preconditioning, converges rather slowly in comparison with the GS procedure optimized by a SOR post-measure. However, it is possible to use a first-order truncation of the expansion:(1+AND)−1=1−AND+AND2−AND3+AND4−AND5+ (11) which is a Krylov expansion that follows directly from a Taylor formula, and which is also pursued implicitly during the Jacobi process x(n+1)=b−ANDx(n), leading to: x _ ( ∞ ) = lim n → ∞ ⁢ ( [ ∑ m = 0 n ⁢ ( - 1 ) m ⁢ A ND m ] ︸ → ( 1 + A ND ) - 1 ⁢ b _ + A ND n ⁢ x _ ( n ) ︸ → 0 ) ( 12 ) and from the limit case of which the validity of Equation (11) is confirmed. Now, using the first-order truncation 1−AND of the matrix expansion expressed in Equation (12) as a preconditioner, it turns out that the convergence efficiency of the Bi-CGStab method can be improved substantially. Premultiplication of the left and right hand sides of Equation (7) with this first-order preconditioner 1−AND yields the transformed system A _ ⁢ x _ = b _ _ ⁢ ⁢ with ⁢ ⁢ { A _ = 1 - A ND 2 b _ _ = b _ - A ND ⁢ b _ ( 13 ) Use of this particular preconditioner means that the direct neutronic interaction between neighbouring (red vs. black) nodes/cubes is preincluded in the system to be solved, making the unity operator more dominant since∥AND2∥<∥AND∥. This leads to a substantial efficiency increase when applying the Bi-CGStab procedure. As will be discussed hereunder in more details, this form offers the additional crucial advantage that the iterative solution can be restricted to one colour only (either only red or only black). Then, the values of the opposite colour can be postcomputed directly, without any further need for iterations. This is because the operator AND2 couples nodes/cubes only if they have the same colour (so red with red, or black with black). In this sense, it can be compressed to a single-colour checkerboard equation, where the entire equation as well as the solution procedure can be defined and pursued at the level of only half of the nodes/cubes, after the choice of the colour to be solved. With a purely red-black form of the linear system, as indicated in Equation (9), Equation (13) is equivalent to a formulation of the equation for merely the red or merely the black part of the system. Expressing xblack in terms of the fixed black source part bblack and the red solution part xred, and substituting this in the equation for the red part, we get the form for the red solution part only: A _ red ⁢ x _ red = b _ _ red ⁢ ⁢ with ⁢ ⁢ { A _ red = 1 - A ND 2 b _ _ red = b _ red - A ND ⁢ b _ black ( 14 ) For the black part, a similar form applies. Hence, it is possible to solve only the red solution part on the basis of Equation (14) and, after convergence, solve the black part directly from the black equation part of Equation (9). For the efficient and, especially, robust solution of Equation (14), the specially-tailored checkerboard-preconditioned Bi-CGStab method, defined on merely half of the grid, is given by: 1. r red , 0 = b red - A _ red ⁢ x red , 0 ; ⁢ r * = r red , 0 2. p red , 0 = r red , 0 3. do ⁢ ⁢ i = 0 , 1 , … ⁢ , N 4. α i = ( r red * , r red , i ) ( r red * , A _ red ⁢ p red , i ) 5. s red , i = r red , i - α i ⁢ A _ red ⁢ p red , i 6. ω i = ( A _ red ⁢ s red , i , s red , i ) ( A _ red ⁢ s red , i , A _ red ⁢ s red , i ) 7. x red , i + 1 = x red , i + α i ⁢ p red , i + ω i ⁢ s red , i 8. r red , i + 1 = s red , i - ω i ⁢ A _ red ⁢ s red , i 9. β i = ( r red * , r red , i + 1 ) ( r red * , r red , i ) ⁢ α i ω i 10. p red , i + 1 = r red , i + 1 + β i + 1 ⁡ ( p red , i - ω i ⁢ A ⁢ ⁢ p red , i ) 11. end ⁢ ⁢ do ( 15 ) As previously indicated, procedure (15) can be referred to as a single-colour checkerboard equation, where the entire equation as well as the solution procedure can be defined and pursued at the level of only half of the nodes/cubes, after the choice of the colour to be solved. The nodes/cubes of opposite colour are then typically used for enabling the application of AND2 by two successive applications of AND which is a red-black operator. From this approach, the convenient red-black sparsity of the applied matrix is preserved, i.e. a precomputed and prestored explicit checkerboard-preconditioned offdiagonal matrix, which would allow ignorance of the nodes of opposite colour, would simply have a lot more offdiagonal nonzero elements. It is worth noting here that the main workload per iteration, i.e. the application of AND2 on half of the grid (red cubes only for example), gives a computational effort similar to the one involved in pursuing one GS iteration on a red-black ordered grid, with AND applied on the full grid (red cubes first, then black cubes). The workload for computing the scalar sums is low. In FIG. 3, the convergence behaviour of the checkerboard-preconditioned Bi-CGStab procedure (curve 9), up to solution accuracy ε=10−8 is plotted in comparison with GS/SOR procedure (curve 11) with the best SOR parameter value applied (ω=1.8), both of these procedures being applied on a red-black ordered grid. From FIG. 3, it is clear that the parameter-free checkerboard-preconditioned Bi-CGStab procedure offers at least the same convergence speed as the GS procedure with the highest possible degree of SOR acceleration. With the checkerboard-preconditioned Bi-CGStab procedure being parameter-free, it can be expected to offer a guaranteed competitive (or even better) performance also for cases where the optimum SOR parameter is different from the one that was applied here. The computational effort per Bi-CGStab step is slightly larger than twice a GS-step, but not much larger if the Bi-CGStab procedure is programmed efficiently. However, the Bi-CGStab procedure, if combined with a good preconditioner, requires dramatically fewer iterative steps for fulfilling a prespecified error criterium. Therefore, keeping in mind heavy performance sensitivity with regard to small variations in the SOR parameters, the checkerboard-preconditioned Bi-CGStab procedure thereby presents itself as a substantially more robust, reliable and parameter-free choice for pursuing iterations on the platform of a red-black ordered grid. Thus, the above-disclosed method can be efficiently used to obtain relevant core simulations in a shorter time period. Another convenient property, worth mentioning separately, is the fact that the node residuals appear explicitly in the Bi-CGStab equations, such that they do not have to be computed separately for purposes of convergence monitoring. In the convergence examples disclosed so far, the convergence criterium adopted was the one which is conventionally used for the ith iteration of traditional SOR-accelerated Jacobi or Gauss-Seidel iterations, ɛ max ⁡ ( i ) = max j = 1 , … ⁢ , N ⁢  x j ( i ) x j ( i - 1 ) - 1  ( 16 ) for the specific reason that this is the currently still default definition of the convergence criterium. However, instead of merely monitoring how much an iterant differs from its predecessor, one can also monitor directly the evolution in the actual residual b−Ax of the linear equation to be solved, which is to converge to 0 when exact fulfillment of the equation is established. This can, optionally, be done for merely the transformed unicolor part of the unicolor-transformed equation in this case:rred= bred−Āredxred (17) As mentioned previously, a convenient property of the Bi-CGStab procedure is the fact that the node residuals appear explicitly, such that they do not have to be computed separately for purposes of convergence monitoring. When using the maximum cube residual:rmax(i)=maxj=1, . . . , N\|rj(i)\| (18) s the convergence monitoring quantity, which constitutes a fourth aspect of the invention, it turns out that the Bi-CGStab procedure in fact offers a noticeable performance enhancement in comparison with the optimized GS procedure. This is connected to the property that the Bi-CGStab procedure is specifically tailored for optimally efficient and fast minimization of an integrated, Galerkin-weighted residual of the linear equation. Repeating the comparison between the checkerboard-preconditioned Bi-CGStab procedure (curve 13) and red-black SOR-accelerated GS procedure (curve 15), the latter with the empirically determined optimum choice (ω=1.8) for the SOR parameter, we get the picture shown in FIG. 4. This particular comparison confirms the expected performance enhancement connected to the use of checkerboard-preconditioned Bi-CGStab compared to red-black GS, in case of a use of rmax (i) as the convergence monitoring quantity for the ith iteration. Thus, in case of the red-black GS approach, the black part of the solution is always ahead of the red part since the black nodes always profit from the updated information in their red neighbours. Another way of formulating this is that the red part of the iterant is always “lagging behind”, which means that one will always have to expect an “unfair” difference in absolute residuals between red and black nodes. With the checkerboard-preconditioned Bi-CGStab approach, this “unfair” difference is eliminated totally, which serves to explain the convergence speed advantage of checkerboard-preconditioned Bi-CGStab compared to red-black GS that can be observed in FIG. 4. Further, it is recommended, according to the fourth aspect of the invention, to adopt rmax(i) as the convergence monitoring quantity for red-black Bi-CGStab applications, since this: is a fundamentally more meaningful convergence monitoring quantity, which indicates much more strictly whether the equation is satisfied, or not will avoid the storage of old iterants x(i) will spare the computation, for each step i, of the old convergence criterium εi as in Equation (16). Another point worth mentioning is that a solving procedure based on a red-black ordering can be parallelized straightforwardly so that the computational efficiency can be further improved. Indeed, with a red-black ordering, there is no degradation when the red and black node computations are subdivided subsequently between processors, i.e. with the red node computations being first subdivided between the processors and then the black node computations being subdivided between the processors. This holds true not only when a GS procedure is used but also with other procedures such as a CG procedure. For a GS procedure, this independence is connected to the property that, in the first half of a red-black GS iteration, the red updates depend on old neighbour information from the previous parallelized GS iteration, all the results of which have been communicated already to all the parallel processors. This feature is independent on how many parallel processors are used. During the second, black part of the iteration, all updates on all the red values will be known in all processors since these were uniformly communicated and distributed by the master processor at the end of the first half of the present GS iteration. Again, this is independent on how many parallel processors are used, meaning that the application of N parallel processors will result in a theoretical speed-up factor of N. In practice, due to interprocessor communications, this gain is reduced a bit but typically not much, meaning that very large speedups are possible in any case. Commonly, the very outer part of a red-black GS iteration is a loop over red and black cubes, usually represented by something in the nature of “do i_rb=1,2”, and it's typically the inner loops over the large numbers of cubes which are parallelly assigned to the different processors. In FIG. 5, different simulated waiting times scenarios are plotted as a function of the numbers of available parallel processor(s) 1 (curve 17), 2 (curve 19), 4 (curve 21) and 8 (curve 23), in case of red-black ordering. In case of lexicographic ordering, the algorithm efficiency degrades more and more as the number of processors increases, leading to very disappointing speedups when doing parallel computations. The above examples have been given with reference to the computation of thermohydraulics parameters. However, the invention also applies to the computation of neutron flux as disclosed hereunder. In this case, the sparse system to solve is an eigensystem. Such a system amounts to:{circumflex over (M)}d=λ{circumflex over (F)}d+Q (19) with {circumflex over (M)} and {circumflex over (F)} the loss-migration and production operators, respectively, and with Q=0 for steady-state cases and λdef=1 for transient cases. For specific numerical solution purposes, the loss and migration operator {circumflex over (M)} can be divided in its diagonal and non-diagonal parts:{circumflex over (M)}={circumflex over (M)}D+{circumflex over (M)}ND (20) with the non-diagonal part {circumflex over (M)}ND being a red-black operator, i.e. when applied to a red vector it yields a black vector and vice versa. The red-black ordering of the nodes is used in the setup of the iterations, using the property [{circumflex over (M)}NDd(n)]red={circumflex over (M)}NDdblack(n) and [{circumflex over (M)}NDd(n)]black={circumflex over (M)}NDdred(n), which are specific for the relationship between currents defined over the surface boundaries of red and black nodes in an interface current formulation of the neutronic balance equation (out-currents of red nodes are in-currents for black nodes). A classical GS iterative procedure (with iteration index n) can be set up such that each iterative sweep consist of a red part followed by a black part: first the red part of the iterant dred is updated, after which this updated part of the iterant dred is used to generate a further improved update of the black part dblack of the iterant: d _ red ( n + 1 ) = M ^ D - 1 ⁡ [ λ ( n ) ⁢ F ^ ⁢ d _ red ( n ) - M ^ ND ⁢ d _ black ( n ) + Q _ red ] ⁢ ⁢ d _ black ( n + 1 ) = M ^ D - 1 ⁡ [ λ ( n ) ⁢ F ^ ⁢ d _ black ( n ) - M ^ ND ⁢ d _ red ( n + 1 ) + Q _ black ] ( 21 ) or, with the restricted production operator {circumflex over (F)} being diagonal, through application of d _ red ( n + 1 ) = ( M ^ D - λ ( n ) ⁢ F ^ ) - 1 ⁡ [ - M ^ ND ⁢ d _ black ( n ) + Q _ red ] ⁢ ⁢ d _ black ( n + 1 ) = ( M ^ D - λ ( n ) ⁢ F ^ ) - 1 ⁡ [ - M ^ ND ⁢ d _ red ( n + 1 ) + Q _ black ] ( 22 ) and with the eigenvalue estimate λ(n) computed (for steady-state cases only) through use of a unity weighting function: λ ( n ) = 〈 1 _ ❘ M ^ ⁢ d _ ( n ) 〉 ( red ) 〈 1 _ ❘ F ^ ⁢ d _ ( n ) 〉 ( red ) ( 23 ) Now, as an alternative, one can also choose to solve only the red currents (or only the black currents), according todred(n+1)=[({circumflex over (M)}D−λ(n){circumflex over (F)})−1{circumflex over (M)}ND]2dred(n)+{tilde over (Q)}red (24) with the fixed transformed source{tilde over (Q)}red=({circumflex over (M)}D−λ(n){circumflex over (F)})−1[Qred−{circumflex over (M)}ND({circumflex over (M)}D−λ(n){circumflex over (F)})−1Qblack], (25) The attractive computational property of this approach is related to the lower norm of the operator [({circumflex over (M)}D−λ(n){circumflex over (F)})−1{circumflex over (M)}ND]2 compared to the norm of ({circumflex over (M)}D−λ(n){circumflex over (F)})−1{circumflex over (M)}ND, which is beneficial to the equation residual decay regardless of whether one uses a classical iteration procedure or an iteration procedure as disclosed hereunder. Furthermore, the computation of the eigenvalue updates and the convergence monitoring will involve loops which are twice as short, meaning that the improvement in error decay condition number can be obtained without computational penalty in this case. A matrix-vector product applied to the red or black vector involves only a sum over half of the nodes. After convergence of the iteration procedure, one can compute, directly, the black part of the solution:dblackexact=({circumflex over (M)}D−λ(exact){circumflex over (F)})−1[−{circumflex over (M)}NDdred(exact)+Qblack] (26) According to a fifth aspect of the invention, a specific solving procedure has proven to be particularly efficient when dealing with eigensystems. This solving procedure is known as Bi-CGSTAB (Bi-Conjugate Gradient Stabilized) and is disclosed in: H. A. van de; Vorst, “Bi-CGSTAB: a Fast and Smoothly Converging Variant of Bi-CG for the solution of nonsymmetric linear systems”, SIAM J. Sci. Stat. Comput. 13(2), pp. 631-644 (1992), and Y. Saad, “Iterative Methods for Sparse Linear Systems”, second edition, Society for Industrial and Applied Mathematics (SIAM) (2003). The Bi-CGSTAB procedure belongs to the general class of Krylov subspace methods which incorporates also the Bi-CGStab procedure and the Generalized Minimized Residual (GMRES) procedure. When considering a system of the form:{tilde over (Θ)}d(n)={tilde over (s)}(n)+q (27) with the source term {tilde over (s)}(n) determined by {tilde over (s)}(n)={tilde over (S)}d(n−1), the Bi-CGSTAB sequence, truncated after N steps (with usually N<5), can be written as 1. r 0 = s ~ - Θ ~ ⁢ d 0 2. p 0 = r 0 3. do ⁢ ⁢ i = 0 , 1 , … ⁢ , N 4. α i = ( r * , r i ) ( r * , Θ ~ ⁢ p i ) 5. s i = r i - α i ⁢ Θ ~ ⁢ p i 6. ω i = ( Θ ~ ⁢ s i , s i ) ( Θ ~ ⁢ s i , Θ ~ ⁢ s i ) 7. d i + 1 = d i + α i ⁢ p i + ω i ⁢ s i 8. r i + 1 = s i - ω i ⁢ Θ ~ ⁢ s i 9. β i = ( r * , r i + 1 ) ( r * , r i ) ⁢ α i ω i 10. p i + 1 = r i + 1 + β i + 1 ⁡ ( p i - ω i ⁢ Θ ~ ⁢ p i ) 11. end ⁢ ⁢ do ( 28 ) Whereas the Bi-CGSTAB procedure for solving a nonsymmetric linear system can be put into code very easily, the principal challenges are related to the requirement of having a well-preconditioned linear system in order to enable Bi-CGSTAB procedure to offer an optimum efficiency. Since a good preconditioning typically means an explicit or implicit strong diagonal dominance for the preconditioned operator, the art is to find a (usually implicit) preconditioned form that realizes an optimum trade-off between (i) an effected sufficient degree of diagonal dominance and (ii) a limited computational penalty associated with the systematic implicit preconditioning measure per step in the Bi-CGSTAB procedure. For the Bi-CGSTAB procedure, the preconditioning is based on the shift-inverted implicit form:[{circumflex over (M)}−μ(n){circumflex over (F)}]d(n+1)=(λ(n)−μ(n)){circumflex over (F)}d(n), μ(n)=αλ(n), (29) with typically 0.9<α<0.97. With this choice for the shift μ, the operator {circumflex over (M)}−μ{circumflex over (F)} is guaranteed to remain nonsingular since, during the solution process, μ=αλ will converge down to α times the smallest possible eigenvalue of the system. Solving Equation (29) is numerically equivalent to determining the flux distribution in a slightly subcritical system with a neutron source, which is a perfect scenario for deploying advanced preconditioned Krylov procedure. Typical inner/outer iterative procedure for solving Equation (29) adopt an implicit transformation, meaning that, between successive iterative steps, one solves linear source equations of the form[{circumflex over (M)}−μ(n){circumflex over (F)}]d(n+1)=s(n) with s(n)=(λ(n)−μ(n)){circumflex over (F)}d(n) (30) During the iterative procedure, λ(n) can be updated by application of λ−rebalancing of weighted volume integrals of the different terms in the equation as in Equation (23). Now, we can transform the combined red-black iterative system [ M ^ - μ ( n ) ⁢ F ^ ] ⁢ d _ red + M ^ ND ⁢ d _ black = s _ red ⁢ [ M ^ - μ ( n ) ⁢ F ^ ] ⁢ d _ black + M ^ ND ⁢ d _ red = s _ black ( 31 ) into the following equivalent iterative scheme for the red solution part only: Θ ~ red ⁢ d _ red = s _ ~ red ⁢ ⁢ with ⁢ ⁢ { Θ ~ red = 1 ^ - [ ( M ^ D - μ ⁢ F ^ ) - 1 ⁢ M ^ ND ] 2 s _ ~ red = s _ red - ( M ^ D - μ ⁢ F ^ ) - 1 ⁢ M ^ ND ⁡ ( M ^ D - μ ⁢ F ^ ) - 1 ⁢ s _ black , ( 32 ) This preconditioned system constitutes the sixth aspect of the invention. Once Equation (32) has been solved through the Bi-CGSTAB procedure the black solution part is to be computed from the black part of Equation (31). Use of this particular way of preconditioning, which means that the direct neutronic interaction between neighboring (red vs. black) nodes, as projected onto the rebalancing grid, is preincluded in the system to be solved, making the unity operator in Equation (32) more dominant since∥(({circumflex over (M)}D−μ{circumflex over (F)})−1{circumflex over (M)}ND)2∥<∥({circumflex over (M)}D−μ{circumflex over (F)})−1{circumflex over (M)}ND∥, (33)given that∥({circumflex over (M)}D−μ{circumflex over (F)})−1{circumflex over (M)}ND∥<1 (34) This way of preconditioning manages to pre-include, at low computational cost, crucial information (or the major part of that information) with regard to the physical interactions between nodes that determine the spatial couplings and hence the solution of the equation. As set forth in the previous description, the first to sixth aspects of the invention help to achieve robust and efficient modelizing methods. It should be kept in mind that the first aspect in itself helps in achieving this goal and can thus be used separately from the second to fifth aspects, for example by using a GS iterative procedure. Also, the third and fourth aspects are not necessarily implemented with the second aspect and the fifth aspect is not necessarily implemented with the sixth aspect. The results obtained through the modelizing method can be used to control an existing nuclear reactor core, e.g. for managing the nuclear fuel, or be used for building a new reactor core. The modelizing method can be used to compute both thermohydraulics parameters and neutron flux.
059404698	abstract	A radiation source for generating multi-chromatic, particularly di-chromatic, x-radiation has at least one cathode and an anode for generating x-ray bremsstrahlung and a target surrounded by the cathode for converting the x-ray bremsstrahlung incident on the target into fluorescence radiation. The target is composed of different materials in sections and the sections can be selectively irradiated with the x-ray bremsstrahlung.
041727606	description	DESCRIPTION While the invention is useful for a comparative testing of a variety of components, for example, the control rods, control curtains, fuel rods, upper core support grid, etc. of a nuclear reactor, the invention will be described herein by way of detailed example primarily in connection with the remote testing of irradiated (used) and therefore radioactive control rods. Shown in plan view in FIG. 1 is a four-assembly cell of a typical nuclear reactor core. Four fuel assemblies 11(1)-11(4) are laterally supported at their upper ends in an opening in an upper core support grid formed by intersecting and interlocking beams 12 and 13. Insertable in the water gaps W between the fuel assemblies in a cruciform shaped control rod 14. A perspective view of a control rod 14 is shown in FIG. 2A. The control rod 14 is formed of an upper casting 16, formed with a handle 17, connected to a lower casting 18 by a cruciform center post 19. The lower casting 18 is formed with a velocity limiter 21, guide rollers 22 and a coupling socket 23 for attachment to a suitable control rod drive mechanism as shown, for example, in the previously mentioned U.S. Pat. No. 3,020,888. The upper casting is also fitted with guide rollers 24 by which the control rod 14 is laterally supported between the fuel assemblies. Sheaths having a U-shape are attached to the center post 19 and to the upper and lower casting 16 and 18 to form the four wings 26(1)-26(4) of the control rod. Contained within each of the wings 26(1)-26(4) is a plurality of neutron absorber rods 27. A typical absorber rod 27, as shown in FIG. 2B, is formed of a sealed tube 28 containing neutron absorber material such as in the form of boron carbide (B.sub.4 C) powder 29. The column of powder 29 is segmented by a series of spaced balls 31 which are restricted in movement by spherical crimps 32 in the walls of tube 28. This arrangement aids in preventing voids in the column of powder 29 and prevents loss of all of the powder from the rod in the event of a crack in a portion thereof. FIG. 3 is an elevation and schematic view (not to scale) of a system according to the invention for testing irradiated radioactive control rods. Depicted in FIG. 3 is a water-filled refueling pool 33, surrounded by a railing 55, which is available in a nuclear reactor plant to receive, and provide radiation shielding from, component such as fuel assemblies, control rods and the like that are removed from the reactor. The control rod 14 to be tested may be supported at the bottom of the pool 33 by a suitable fixture 34 or it may be suspended in the pool by a cable 36 connected between the control rod handle 17 and an overhead crane 37. The test apparatus includes a carriage 38 for movement along the control rod 14, a boom 39, a variable speed winch arrangement 41 for moving carriage 38 by means of a cable 42, a travel indicator and encoder 43 and a strip chart recorder 44. The carriage 38 includes a base plate 46 fitted with spring loaded rollers or wheels (not shown on FIG. 3) for close movement along the control rod 14. The base plate 46 carries a source enclosure 47 along one side and a detector enclosure 48 along the other side of the wing 26(1) of the control rod 14. The source enclosure 47 is formed of neutron shielding material and it removably contains a strong source of neutrons. The enclosure 47 is open or apertured on the side adjacent the control rod wing 26(1) whereby neutrons are directed into this wing and into the absorber rods 27 contained therein. The detector enclosure 48 is likewise formed of neutron shielding material to reduce entrance of scattered neutrons from the source in enclosure 47 and stray neutrons from other sources (such as from irradiated fuel assemblies, not shown, that might be in the pool). The side of the enclosure 48 adjacent the control rod wing 26(1) is formed with neutron collimating apertures (slots or holes) and positioned behind these apertures are neutron detectors. Thus the neutron detectors detect the neutrons that pass from the source in source enclosure 47 through the control rod wing 26(1). The signals from the neutron detectors, which are transmitted through a cable 49 to the chart recorder 44 are proportional to the neutron transmission characteristics of the control rod wing 26(1). The carriage 38 is described in greater detail hereinafter. The winch arrangement 41 includes a reversible, speed controlled electric motor 51 and a gear box 52 driving a winch drum 53 upon which the cable 42 is let out or taken up to lower or raise the carriage 38 along the control rod 14. Connected to detect rotation of the shaft of the winch drum 53 is the travel indicator and encoder 43. The indicator-encoder 43 includes a mutiturn potentiometer connected in series with a voltage source and a panel meter 54 in well-known manner. Thus the panel meter 54 can be calibrated directly in units of distance traveled by the carriage 38 along the control rod 14. The indicator-encoder 43 also includes a well-known analog-to-digital convertor or digital encoder which converts rotation of the shaft of winch drum 53 to a digital position-indicating signal. This position signal is supplied over a lead 56 to chart recorder 44 to record the positions of the carriage 38 along the control rod 14 on a recording chart 57 of the chart recorder 44. As mentioned hereinbefore, the signals from the neutron detectors in the detector enclosure 48 of carriage are transmitted through a cable 49 to chart recorder 44 as the carriage 38 is moved along the control rod 14 to scan the neutron transmission characteristics of the wing 26(1) thereof. The well-known chart recorder 44 includes suitable signal processing circuitry and a recording channel for each of the neutron detectors as well as a channel for the position indicating signal from indicator-encoder 43. (Alternatively, the position signal may be superimposed on one or more of the neutron detector signal traces.) Thus as the carriage 38 is moved along the control rod 14, traces of the neutron detector signals and the position signal are recorded on the strip chart 57. This chart record then can be compared to a similarly prepared chart record of a standard control rod of known quality to thereby confirm the quality of or detect any anomalies in the control rod wing 26(1). The other wings 26(2)-26(4) of the control rod 14 are similarly tested and recorded by repositioning of the carriage 38 on the control rod 14. Also shown in FIG. 3 is a cable 58 and a shielded storage cask 59. The cable 58 is attached to the neutron source in the source enclosure 47. The cable 58 is used to remotely insert the neutron source into and to remove it from the enclosure 47 as is described in more detail hereinafter. When the test equipment is not in use, the neutron source is deposited for storage or transportation in the cask 59. Details of the carriage 38 are shown in FIGS. 4A, 4B and 4C. The source enclosure 47 and detector enclosure 48 are essentially rectangular boxes having downward extended side plates which fit into grooves in the base plate 46. For example, a side plate 61 of source enclosure 47 fits into a groove 62 in which it is secured by a screw 65. This provides adjustment of the enclosures toward and away from the control rod wing 26(1) which is received in a U-shaped slot 63 formed with an open end (hidden in FIG. 4A). The enclosures 47 and 48 are formed of relatively thick material having a high neutron capture cross section, such as boron containing aluminum or the like, to reduce neutron leakage from the source and to shield the neutron detectors from stray neutrons. The base plate 46 is fitted with a pair lifting eyes such as eye 64 (the similar eye at the opposite end being hidden in FIG. 4A), for attachment to the yoke ends 42(1) and 42(2), respectively, of the cable 42 (FIG. 3). The carriage 38 is fitted to and restrained for movement along the control rod 14 by a system of three spring loaded wheels. This includes a wheel arrangement 66 attached to the center of one side of the base 46, the arrangement 66 having a shaped wheel 67 which rides upon the outer edge of the wing 26(1) of the control rod under test, and a pair of wheel arrangements, which are indicated as 68, mounted at the opposite corners of the other side of the base 46. The arrangement 68 includes a wheel 69 adapted to ride against the "back" side of the control rod wing 26(2). The similar wheel at the opposite corner of base 46, which is hidden in FIG. 4A, similarly rides against the back side of control rod wing 26(4). Wheel 69 is secured to pivoted arm 71 which is actuatable by movement of a latching arm 72 and linkage attached thereto. Outward movement of arm 72 pivots the arm 71 and wheel 69 outwardly. After the carriage 38 is maneuvered into position on the control rod, the arm 72 is moved inward to bring the wheel 69 into contact with and latch it into position against the control rod arm. The arm 72 can be remotely actuated by a pole fitted with a suitable hook. Such tools are well-known and available at nuclear plants for remove actuation purposes. A suitable latch mechanism for the wheel arrangement 68 is, for example, a KNU-VISE available from Lapeer Manufacturing Company, Detroit, Mich. as catalog No. HLC-600. It is noted that rubbing pads or buttons, such as a pad 75, formed of a suitable material such as nylon, are removably secured to portions of the enclosures 47 and 48 and to base plate 46 at points where rubbing contact with the control rod may occur. Further details of the source enclosure 47 now will be discussed. A suitable neutron source 73 is removably contained in the enclosure 47 in a suitable receptode shown in the form of a slanted tube 74 formed of a material having a low neutron capture cross section. A suitable source is manufactured, for example, by the General Electric Company at its Vallecitos Nuclear Center, Pleasanton, Calif. as a sealed source capsule Model GEN-CF-100. This source contains 1-4 mg of Cf-252 and provides a neutron flux of about 2.4.times.10.sup.9 n/sec/mg of fast neutrons. The enclosure 47 is filled with water by virtue of slots 76 in a source face plate 77 and a shielded water passage 78. (For some applications the apertured face plate 77 can be omitted, the side of the enclosure 47 adjacent the component under test simply being left open.) Some of the neutrons from source 73 are therefore moderated by the water and pass through the slots 76 into the control rod wing under test. The amount of moderation, and hence the average energy (for a given source strength) of the neutrons passing through the component under test, can be adjusted by varying the distance of the source from the component or the amount of moderator between the source and component. The source 73 is retained in its proper position in tube 74 by a pair of slideable and lockable keeper members 79(1) and 79(2) the nose ends of which fit into the tube 74 through transverse slots therein on either side of the source 73. The keepers 79(1) and 79(2) are retained in inserted or withdrawn position by a keeper lock mechanism including a flattened shaft 81 actuatable by an arm 82. An elevation view of the keepers 79(1) and 79(2) with the shaft 81 in cross section is shown in FIG. 4B. The keeper members 79(1) and 79(2) are formed with two spaced holes 83(1) and 83(2) connected by a slot 84. The flattened shaft 81 is shown in hole 83(1), the inserted position of the keeper, and in its locking position. Rotation of the shaft 81, through ninety degrees, by actuation of the arm 82, allows withdrawal of the keeper (by lifting with a remote tool engaging an end hole 85) and movement of the shaft along slot 84 to hole 83(2). Rotating the arm 82 then returns shaft 81 to its sideways position in hole 83(2) to lock the keeper in its withdrawn position. The keeper 79(1) is also formed with an open-ended slot 86 to allow passage of the source cable 58 while blocking movement of the source. It was mentioned hereinbefore that the source 73 is insertable into and removable from the enclosure 47 by means of the cable 58 attached thereto. Insertion is accomplished by bringing the carriage 38 to the end of the pool and inserting the free end of cable 58 upward through the tube 74. Keeper 79(1) is inserted while keeper 79(2) is maintained in its withdrawn position. The carriage 38 is lowered into the pool to provide shielding and the source 73 is pulled by the cable 58 into position in the tube 74. The keeper 79(2) is then inserted, by remote actuation of it and of arm 82, to lock the source in position. The source 73 is removed simply by withdrawing keeper 79(1) and pulling the source from the tube. The discussion will now be directed to the detector enclosure 48. The detector enclosure includes a face plate 87 formed with a plurality of spaced neutron collimating apertures or slots 88(1)-88(4) in line with apertures 76 in source face plate 77 and best shown in the elevation view of face plate 87 in FIG. 4C. Behind the slots 88(1)-88(4) are secured respective neutron detectors 89(1)-89(4) for detection of the neutrons transmitted from the source 73 through the control rod wing 26(1). The slots 88(1)-88(4) are spaced vertically but with their ends in alignment so that scanning of the complete width of the control rod wing 26(1) is achieved with isolated individual neutron detectors. To further detector-to-detector independence, the detectors are isolated from one another in the enclosure 48 by neutron absorbing partitions 90. Individual signal cables from the detectors 89(1)-89(2) are passed through suitable holes in the partitions 90 and collectively exit the enclosure through a top hole to form the cable 49. Suitable neutron detectors are well-known. Neutron detectors and signal processing circuitry are discussed, for example, by W. J. Price in "Nuclear Radiation Detection," 2nd edition, McGraw-Hill, Inc. 1964. A suitable neutron detector for use in the described system is an in-core fission counter detector No. 112C 3107G5 manufactured by the Nuclear Energy Control and Instrumentation Department of the General Electric Company, Jan Jose, Calif. A modification of the system of the invention to provide neutron transmission scanning of individual rods, elements or the like, such as fuel rods or control rod absorber rods (such as rod 27 of FIG. 2B) is illustrated in FIG. 5. The modification comprises an additional or alternate apertured collimating face plate 101 for the detector enclosure 48. The face plate 101 is fitted with apertured upper and lower rod guiding brackets 102(1) and 102(2). Guide apertures 103 in the guide brackets 102(1) and 102(2) are sized to receive therethrough a rod 104 to be tested. The apertures 103 can be made of differing diameters to receive and guide rods of similarly differing diameter. The apertures 103 are positioned to guide the rods to be tested past neutron collimating apertures 106 in the face plate 101 and through the slot 63 in the base plate 46. The apertures 106 may be of a size and shape appropriate for the rod to be tested. The apertures 106 are positioned in alignment with the slots 88(1)-88(4) of the face plate 87 shown in FIG. 4C and hence in alignment with the neutron detectors 89(1)-89(4). The rod 104 to be tested is remotely held and maneuvered by a grapple 107 which is fitted with a remotely actuatable collet 108 or the like by which an extension 109 of the end plug of rod 104 can be gripped. Such a grapple is a common item of equipment in a nuclear plant. To perform the scanning operation the rod 104 may be suspended in the pool and the carriage 38 moved therepast similar to the scanning of the control rod 14 described in connection with FIG. 3. However, it may be more convenient to suspend the carriage 38 in the pool, for example, from crane 37, and move the rod 104 through the guide apertures 103 by attachment of the grapple 107 to cable 42 of boom 39 of FIG. 3. While scanning of cylindrical rods is illustrated in FIG. 5, scanning of components of other transverse cross section shape can be accomplished by suitable modification of the shapes of apertures 103 and 106. Another modification of the system of the invention is illustrated in elevation and schematic view of FIG. 6. The purpose of this modification is to provide scanning of control rod 14 without removing it from the nuclear reactor core. Referring again to FIG. 1 it will be recalled that a cell of the core is formed by a control rod 14 surrounded by four fuel assemblies 11(1)-11(4). In order to provide access of the wings of the control rod, two adjacent ones of the fuel assemblies must be removed in turn. It will be assumed for purposes of the present discussion that the fuel assemblies 11(3) and 11(4) of FIG. 1 are removed to allow access to wing 26(1) of the control rod 14. As mentioned hereinbefore each of the fuel assemblies comprises an array of fuel elements surrounded by an open ended flow channel 15. When the fuel assemblies 11(3) and 11(4) are removed, they are replaced with a pair of attached and empty or dummy flow channels 121(1) and 121(2) of FIG. 6 to retain the control rod 14 in its proper position. These dummy flow channels are fitted at their bottom ends with nose pieces 122 suitably shaped to fit into the fuel assembly nose piece sockets of the core support structure. At their upper ends the dummy channels 121(1) and 121(2) are secured to a spacer and support member 123 of thickness appropriate to the spacing of the channels from the control rod wing 26(1). The support member 123 extends upward and supports a cross member 124. Secured for rotation to cross member 124 are a plurality of cable directing pulleys 126(1)-126(4). For this version and application of the invention, the source enclosure 47 and the detector enclosure 48 are supported and moved on separate carriages within the channels 121(2) and 121(1), respectively. Otherwise construction and operation are similar to that described in connection with FIGS. 3 and 4A. The neutron source enclosure 47 is secured to a carriage base plate 127 of a carriage 128. Extending upward from source enclosure 47, and secured thereto at a point appropriate to the weight distribution thereof, is a lifting eye 129 connected to the yoke end 42(1) of cable 42 (FIG. 3), the cable end 42(1) being threaded under pulley 126(3) and over pulley 126(4). The carriage 128 is fitted at its four corners with suitable guide rollers or slides 129. The detector enclosure 48 is secured to a similar carriage 132 including a lifting eye 133 connected to yoke end 42(2) of cable 42, the cable end 42(2) being threaded under pulley 126(2) and over 126(1). Thus with this arrangement, actuation of the winch 41 moves the carriages 128 and 132 simultaneously along the opposite sides of the control rod wing 26(1) and provides neutron transmission scanning. It is noted that the dummy channels 121(1) and 121(2) are formed of a material such as zirconium alloy having a low neutron capture cross section and hence low attenuation of the neutrons directed by the source into the control rod wing. It is further noted that the distance between the cross member 124 and the tops of channels 121(1) and 121(2) is sufficient to allow insertion and removal of the carriages 128 and 132 into and from the channels. Thus what has been described is a method and portable apparatus for remotely performing on-site testing of radioactive components by determining their neutron transmission characteristics.
	summary
	summary
	abstract	A core of a light water reactor having a plurality of fuel assemblies, which are loaded in said core, having nuclear fuel material containing a plurality of isotopes of transuranium nuclides, an upper blanket zone, a lower blanket zone, and a fissile zone, in which the transuranium nuclides are contained, disposed between the upper blanket zone and the lower blanket zone; wherein a ratio of Pu-239 in all the transuranium nuclides contained in the loaded fuel assembly is in a range of 40 to 60% when burnup of the fuel assembly is 0; sum of a height of the lower blanket zone and a height of the upper blanket zone is in a range of 250 to 600 mm; and the height of said lower blanket zone is in a range of 1.6 to 12 times the height of the upper blanket zone.
	claims	1. An X-ray analyzer for irradiating a sample containing various components with X-rays to detect X-rays emitted from the sample, wherein an X-ray irradiation unit that irradiates the sample with X-rays includesa) an X-ray source configured to emit X-rays,b) a first multi-capillary which is composed of a large number of X-ray guiding capillaries parallel to each other, and has an incident end face arranged at a position where X-rays emitted from the X-ray source are introduced,c) a second multi-capillary which is composed of a large number of X-ray guiding capillaries, and is a parallel/point focus multi-capillary X-ray lens formed such that the capillaries are parallel on an incident end side and converged in a tapered shape mildly curved on an exit end side,d) a Fresnel zone plate, ande) a first moving section configured to move the second multi-capillary and the Fresnel zone plate such that one of the second multi-capillary and the Fresnel zone plate is selectively inserted on an X-ray optical path from the first multi-capillary to the sample. 2. The X-ray analyzer according to claim 1, further comprising a first X-ray detector configured to detect X-rays emitted from the sample in response to the X-rays irradiated to the sample through the second multi-capillary or the Fresnel zone plate. 3. The X-ray analyzer according to claim 2, wherein the X-ray irradiation unit further includes a first rotating section configured to integrally rotate the X-ray source and the first multi-capillary, a flat plate spectroscopic crystal, and a second moving section configured to move the flat plate spectroscopic crystal such that the flat plate spectroscopic crystal is located at a position where the X-ray emitted from an exit end face of the first multi-capillary reaches. 4. The X-ray analyzer according to claim 3, further comprising a second X-ray detector which is placed at a position where an X-ray diffracted from an X-ray diffraction analysis sample placed at a position where the sample is placed is able to detected, and a second rotating section configured to rotate the X-ray diffraction analysis sample and the second X-ray detector while maintaining a predetermined relationship,wherein the second multi-capillary and the Fresnel zone plate are both retracted from an optical path of an X-ray emitted from the first multi-capillary or of an X-ray emitted from the first multi-capillary and extracted from the flat plate spectroscopic crystal after hitting the flat plate spectroscopic crystal, and a diffracted X-ray corresponding to an X-ray irradiated to the X-ray diffraction analysis sample is detected by the second X-ray detector. 5. The X-ray analyzer according to claim 3, further comprising a third moving section configured to move the Fresnel zone plate on an optical axis,wherein the third moving section and the first rotating section are controlled such that a position on an optical axis of the Fresnel zone plate and an energy or wavelength of an X-ray extracted from the flat plate spectroscopic crystal are changed in conjunction with each other so as to constantly position the sample at a focal distance position of an X-ray having a predetermined energy or wavelength. 6. The X-ray analyzer according to claim 4, further comprising a third moving section configured to move the Fresnel zone plate on an optical axis,wherein the third moving section and the first rotating section are controlled such that a position on an optical axis of the Fresnel zone plate and an energy or wavelength of an X-ray extracted from the flat plate spectroscopic crystal are changed in conjunction with each other so as to constantly position the sample at a focal distance position of an X-ray having a predetermined energy or wavelength. 7. The X-ray analyzer according to claim 3, further comprising a photoelectron spectroscopic detector configured to detect photoelectrons emitted from the sample in response to irradiation of an X-ray extracted by the flat plate spectroscopic crystal. 8. The X-ray analyzer according to claim 3, wherein the X-ray source and the first multi-capillary are integrally rotated by the first rotating section, and an X-ray emitted from the sample in response to the irradiation of an X-ray extracted by the flat plate spectroscopic crystal is detected so as to acquire an absorption edge spectrum.
042773075	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to homogeneously doped Si crystals and somewhat more particularly to a method of restoring Si crystal lattice order after neutron irradiation. 2. Prior Art Homogeneously doped Si crystals may be produced via neutron irradiation so that the nuclear reaction: ##STR1## occurs within the irradiated Si crystal. The silicon crystal utilized as the stock or starting material for the irradiation generally is produced by thermal decomposition of silicon-containing compounds and generally contains carbon as an impurity. This is known, for example, from N. Schink, "Determination Of Carbon In Trichlorosilane", Semiconductor Silicon, (The Electrochemical Society, 1969) pages 85-88. However, such neutron irradiation causes lattice disorder or damage detrimental to the electrical properties of the doped crystal. Such neutron-induced lattice damage may be removed by annealing. For example, German Letters Patent No. 1,214,789 suggests a method of producing homogeneously n-doped Si crystals by irradiating such crystals with thermal neutrons and then heat-treating the so-irradiated crystals at an elevated temperature for a sufficient period of time to remove the lattice damage cause by the neutron irradiation. In accordance with the prior art, the time period of the heat treatment is dependent upon the intensity of the neutron flux in the nuclear reactor during the irradiation process. Accordingly, the respective temperature and time is determined by the degree of crystal lattice damage or distortion produced by the irradiation process. The above-referenced prior art patent suggests that neutron-induced crystal lattice damage may be removed by annealing an irradiated Si crystal for 24 hours in a furnace at 1000.degree. C. Other prior art, for example, German Offenlegungsschrift No. 25 16 514 (owned by the instant assignee and substantially corresponding to Burtscher et al U.S. Ser. No. 676,646, filed Apr. 14, 1976, now abandoned) suggests that such annealing be carried out for a time period at least equal to the time period of a subsequent diffusion process and at a temperature at least as high as that utilized during such subsequent diffusion process. However, it has been determined that when semiconductor components are produced from such prior art annealed crystals, the electrical properties, particularly the specific electrical resistance, sometimes vary during subsequent diffusion and the like processes. SUMMARY OF THE INVENTION The invention provides a method of restoring Si crystal lattice order in a Si monocrystal homogeneously doped via neutron irradiation comprised of an improved annealing process so that the semiconductor components produced from the so-annealed crystals exhibit reproducible electrical properties, which are congruent with at least the specific electrical resistance property of the annealed crystals. In accordance with the principles of the invention, neutron-irradiated carbon containing Si crystals are subjected to an annealing or heat-treatment process for at least 30 minutes at a minimum temperature adjusted in accordance with the make-up of the irradiation flux utilized during neutron irradiation (i.e., in accordance with the ratio of thermal neutrons to fast neutrons) and in accordance with the carbon concentration within the irradiated crystals. Of course, this carbon concentration is first determined in any known manner before the annealing process. In embodiments of the invention where the neutron flux utilized to irradiate Si crystals contains at least 99% thermal neutrons (i.e., the neutron flux contains a ratio of thermal neutrons to fast neutrons of 100:1), the annealing temperature is set at a value of at least 700.degree. C., independently of the carbon concentration in the irradiated crystals. In embodiments where the neutron flux utilized to irradiate Si crystals contains a ratio of thermal neutrons to fast neutrons in the range of 1:1 to less than 10:1, the annealing temperature is set at a value greater than 1100.degree. C. if the irradiated crystals have a carbon concentration greater than 3.multidot.10.sup.16 atoms/cm.sup.3 and the annealing temperature is set in the range of 750.degree. to 1000.degree. C. if the irradiated crystals have a carbon concentration less than 3.multidot.10.sup.16 atoms/cm.sup.3. In embodiments where the neutron flux utilized to irradiate Si crystals contains a ratio of thermal neutrons to fast neutrons in the range of 10:1 to less than 100:1, the annealing temperature is set at a value greater than 1000.degree. C. if the irradiated crystals have a carbon content greater than 3.multidot.10.sup.16 atoms/cm.sup.3 and the annealing temperature is set to be at least equal to 750.degree. C. if the irradiated crystals have a carbon concentration less than 3.multidot.10.sup.16 atoms/cm.sup.3.
	description	The present invention generally relates to an electric generator and specifically, to a method and a system for detecting collector flashover. Generators are an indispensible part of power systems and are extensively used for power generation. Generators work on the principle of electromagnetic induction. A rotating magnetic field is generated either by a set of permanent magnets or electromagnets. Magnetic flux of the rotating magnetic field is linked to stationary coils. Due to rotation of the magnetic field, the flux linked to stationary coils varies in a sinusoidal fashion, causing a sinusoidal variation of voltage across the terminals of the stationary coils. Typically, the stator of a generator is provided with slots for winding the stationary coils. The rotor is provided with magnets for generating a rotating magnetic field. The magnets disposed in the rotor may be permanent magnets or electromagnets. In most generators electromagnets are provided. To magnetize the electromagnets a current is applied on rotor coils wound over the said electromagnets. For continuous flow of current in the rotor coils one or more collector rings and brush arrangements are used. Under normal operation, the brushes maintain an optimum pressure on the collector rings so that the circuit is always closed. In due course of time, the pressure of the brushes on the collector rings is reduced. Also, the collector rings and the brushes undergo continuous wear and tear that sometimes results in gaps between the collector ring and the brush. Arcing may take place in the gap, which may further lead to a flashover, hereinafter referred to as collector flashover. This may lead to tripping of the generator, thereby causing a forced outage. According to currently existing techniques, periodic inspections of the generator are carried out for preventing collector flashovers. When damage to the collector rings or the brushes is detected, corrective action is taken to prevent collector flashovers. However, inspecting the generators frequently is inconvenient. Also, for every inspection, the generator needs to be shut down. The existing methods cannot predict a potential collector flashover while the generator is in operation. Thus, there is a need for a system and method for a more efficient detection of collector flashovers. A system, method and computer program product for predicting collector flashover is disclosed. The method includes receiving a frame of measured data from a data acquisition system, fitting a statistical model to the measured data wherein the measured data includes a plurality of measured variables measured at multiple time instances. The statistical model and the measured data are used for estimating one or more parameters for the frame wherein the one or more parameters include at least one of field circuit impedance and field current noise. A flashover is predicted based, at least in part, upon the one or more estimated parameter for the frame. The system for predicting flashover of an electrical generator collector includes a receiver module for receiving a frame of measured data corresponding to a plurality of measured variables, wherein the frame of measured data comprises the plurality of measured variables measured at multiple time instances. The system further includes a statistics module for fitting a statistical model to the measured data. Still further, the system includes an estimation module for estimating one or more parameters for the frame based upon the measured data and the statistical model, wherein the one or more parameters comprise at least one of field circuit impedance and field current noise. A flashover prediction module included in the system predicts a flashover condition of the electrical generator collector based, at least in part, upon the one or more estimated parameter for the frame. Embodiments of the present invention provide methods, systems and computer program products for predicting a flashover condition in the collector of a generator. FIG. 1 shows an environment 100 in which various embodiments of the present invention will operate. The environment 100 includes a generator 102 that converts mechanical energy of a prime mover into electrical energy. In various embodiments, the generator 102 is a slip-ring type generator. The slip-ring type generator includes field windings wound on the rotor. The field windings may be excited by an exciter and control unit 104. The exciter and control unit 104 includes an exciter such as, but not limited to, a DC generator, a battery, a rectified AC supply, or a static exciter. The static exciter feeds back a portion of the AC from each phase of generator output to the field windings, as DC excitations, through a system of transformers, rectifiers, and reactors. An external DC source may be used for initial excitation of the field windings. The exciter applies an excitation voltage, herein referred to as field voltage to the generator rotor, thereby causing a field current to flow through the field winding. Due to rotation of the field windings, the flux linked to stationary coils, disposed in a stator of the generator 102, varies in a sinusoidal fashion, causing a sinusoidal variation of voltage across the terminals of the stationary coils. The exciter and control unit 104 controls the operation of the generator 102. For example, the exciter and control unit 104 may control the field voltage, and field current supplied to the generator 102. Typically, a slip-ring type generator 102 is provided with one or more collector ring and brush assemblies for continuous flow of field current in the field windings disposed on the rotor. For reasons mentioned above, a flashover may occur between the collector ring and the brush causing power failure. An object of the present invention is to predict a flashover condition so that preventive measures may be taken. The environment 100 may further include a generator monitoring unit 106. The generator monitoring unit 106 may include a plurality of sensors for measuring one or more variables associated with the operation of the generator 102. The measured variables may include, without limitation, generated voltage, generated power, generated current, field voltage, field current, radio frequency (RF) signals, and the like. The generator monitoring unit 106 may communicate the measured variables to an exciter and control unit 104. Alternatively, the generator 102 may have sensors mounted thereon to measure variables such ozone concentration, visible and UV light emission, audible noise proximate to the collector ring and brush assemblies. The generator monitoring unit 106 may also measure these variables. Such variables may have a small magnitude under normal operating conditions, but may have prominent magnitudes in arcing and flashover events. In one embodiment, the generator monitoring unit 106, the exciter and control unit 104, and the exciter may be included in an integrated excitation, control and monitoring system. Such an integrated excitation, control and monitoring system may be implemented using hardware such as, but not limited to, microcontrollers, microprocessors, logic circuits, and memories; and software modules stored on the memories. According to embodiments of the present invention, the environment 100 also includes a flashover prediction system 108. The flashover prediction system 108 predicts an impending flashover condition so that an alarm may be flagged, a warning may be issued and/or a preventive action may be taken. Various embodiments of implementing the flashover prediction system 108 are described in detail in FIG. 2. In one embodiment, the flashover prediction system 108 may be deployed as a separate unit. In another embodiment, the flashover prediction system 108 may be part of the generator monitoring unit 106. In yet another embodiment, the flashover prediction system 108 may be part of the exciter and control unit 104. In one embodiment, the flashover prediction system 108 may be integrated within the integrated excitation, control and monitoring system described above. FIG. 2 shows a detailed block diagram of the flashover prediction system 108, in accordance with an embodiment of the present invention. The flashover prediction system 108 includes a receiver module 202, a statistics module 204, an estimation module 206 and a prediction module 208. The receiver module 202 may receive measured data from the exciter and control unit 104 and/or the generator monitoring unit 106. The measured data corresponds to a plurality of measured variables such as, but not limited to, the field current, the field voltage, the power consumed in the field of the generator 102, ozone concentration, visible and UV light emission, audible noise, and so forth. The receiver module 202 may receive the data through wired or wireless communication links. The receiver module 202 may obtain a frame of measured data corresponding to the plurality of measured variables. A frame of measured data may include a series of data points of the plurality of measured variables measured at predefined intervals. In an example implementation, the predefined intervals at which the variables are measured may be 1 second. In one embodiment, the receiver module 202 may receive the data points at the predefined intervals. The receiver module 202 may store the data points in a memory, to form a frame of measured data. In another embodiment, the receiver module 202 may receive a complete frame of measured data. The generator monitoring unit 106 or exciter and control unit 104 may buffer the data points at the predefined intervals and transfer the frame of measured data. The flashover prediction system 108 transfers the frame of measured data received by the receiver module 202 to the statistics module 204. The statistics module 204 fits a statistical model to the frame of measured data. In various embodiments, the statistics module 204 may divide the frame of measured data into a plurality of time windows, each of a fixed duration. The statistics module 204 may then fit a statistical model to the measured data of each time window. In other words, the statistics module 204 calculates the coefficients and intercepts of a curve that best fits the time series of data points of each time window. For example, the statistics module 204 may fit a straight line to the measured data of each time window, the straight line having the formula:V=RI+ε Equation 1 where, V is the field voltage, I is the field current, R is the field circuit resistance and ε is the noise. The statistics module 204 may perform rolling window fitting on the frame of measured data. In other words, the statistics module 204 may fit the statistical model to one time window, then advance the time window by a predefined number of data points, for example, 1 data point, and then repeat process of fitting the statistical model. In one embodiment, successive time windows may be non-overlapping time windows. In other words, no data points are repeated in successive time windows. In another embodiment, successive time windows may be overlapping time windows. In other words, a predefined number of initial data points of one time window may be the final data points from the previous time window. In one example implementation, the statistical model may be a linear regression model. The linear regression model may be obtained by any known linear regression method. In an embodiment, the linear regression method is a least squares regression method. In some other embodiments, the linear regression method may be one of least absolute deviation, maximum likelihood estimation, principal component regression, ridge regression, and so forth. The regression coefficients may also be obtained using Kalman filtering. In one embodiment, the statistics module 204 may convert the received frame of measured data into a centered moving average time series of measured data. The statistics module 204 may then fit the statistical model to the centered moving average time series of measured data. In some other embodiments, the statistics module 204 may convert the received frame of measured data into a simple moving average time series of measured data. The estimation module 206 then estimates one or more parameters based on the statistical model and the measured data. The parameters include, without limitation, field current noise and field impedance. In one embodiment, the estimation module 206 may substitute at least one measured variable for each time instance of the time window into the statistical model for that time window. For example, the estimation module 206 may substitute the measured field voltage (independent variable V in Equation 1) for each time instance of the time window into the statistical model for that time window. The estimation module 206 may then compute a predicted value for one of the measured variables based on the substitution of the at least one other measured variable into the statistical model. For example, the estimation module 206 may compute a predicted value of the field current (dependent variable I in Equation 1) based on the substitution of the measured field voltage in Equation 1. The estimation module 206 may then compute the difference (referred to as “residue” herein) between the predicted value and the measured value of the dependent variable for all time instances of the time window. For example, the estimation module 206 may compute the residue of the field current at every time instance of the time window. The residue of the field current represents the field current noise. In one embodiment, the estimation module 206 may convert the residue at a given time instance to a percentage of the actual measured value at the given time instance of the time window. In another embodiment, the estimation module 206 may record the coefficients of the statistical model, for example coefficient R in Equation 1. R represents the estimated value of field circuit resistance for a given time window. The variations in the estimated field circuit resistance may be used to predict a potential flashover condition. For example, drastic changes in the field circuit resistance from one time window to the next indicate that the brush contact pressure on the collector rings may not be optimal, and thus, a potential flashover condition may be impending. The prediction module 208 may predict a potential flashover condition based on one or more of the parameters estimated by the estimation module 206. In some embodiments, the prediction module 208 may predict a potential flashover condition based on the residue of the parameters estimated by the estimation module 206. In some other embodiments, the prediction module 208 may directly employ the parameters estimated by the estimation module 206 to predict a potential flashover condition. In one embodiment, the prediction module 208 compares the computed residues with a predefined threshold (for example, 1%). The prediction module 208 may then determine a density count denoting the number of occurrences of the residue exceeding the predefined threshold. The prediction module 208 may also determine an occurrence interval between successive occurrences of the residue exceeding the predefined threshold. The prediction module 208 may then compute the median value of the occurrence intervals. The prediction module 208 may then give an indication of the potential flashover condition based on the density count and/or the median value of occurrence interval. For example, the prediction module 208 may indicate a potential flashover condition if the density count exceeds 1% of the total number time instances for which the residue was computed and/or the median value of occurrence interval is less than 1 second. In another embodiment, the prediction module 208 uses the residue converted to a percentage of the actual measured value in the above comparisons to predict the potential flashover condition. In yet another embodiment, the prediction module 208 uses the estimated parameters in the above comparisons to predict the flashover condition. For example, the prediction module 208 may compare the estimated field circuit resistance with a predefined threshold, and determine the density count and the occurrence interval. The prediction module 208 may then indicate a potential flashover condition if the variation in the estimated field circuit resistance values exceeds the permissible amount of variation in the field circuit resistance. If the prediction module 208 indicates a potential flashover condition a warning may be flagged. The flagged warning may be conveyed to an operator through an output device 210. In an embodiment of the present invention, the output device 210 may be an alarm or a flashing light source. Alternately, the output device 210 may be a display device displaying a warning message. In one embodiment, the output device 210 may be an interface linked to the exciter and control unit 104, which automatically shuts down the generator 102 upon indication from the prediction module 208 that a potential flashover condition exists. FIG. 3 is a flowchart illustrating an exemplary process 300 of predicting a flashover condition in the generator 102, in accordance with one embodiment of the present invention. In step 302, the flashover prediction system 108 receives a frame of measured data corresponding to one or more measured variables. A frame of measured data may include a time series of data points corresponding to one or more variables measured at predefined time intervals over a time window. The duration of the time window may depend on the specific requirements of the system. In an embodiment of the present invention, the time window may be of 10 minutes duration. The predefined intervals at which the variables are measured may be one second. The frame of measured data includes measured variables associated with operation of the generator 102. The measured variables may be at least one of the field current, field voltage, power consumed in the field of the generator 102, ozone concentration, visible and UV light emission, audible noise, and so forth. In step 304, the flashover prediction system 108 fits a statistical model to the frame of measured data. In an embodiment, the model fitted to the measured data is a linear regression model. The frame of measured data may be divided into a plurality of time windows. The plurality of time windows may be overlapping or non-overlapping. The flashover prediction system 108 may fit a statistical model to each of the plurality of time windows. The flashover prediction system 108 may then record the coefficients and intercepts of the statistical model for each time window. In an embodiment of the present invention the statistical model may be used to establish a functional relationship between field voltage and field current (for example Equation 1). In this case the coefficient of the statistical model represents the field circuit resistance R, and the intercept represents the noise ε. In an embodiment of the present invention, a least squares method may be applied to determine the coefficients of the linear regression, though other techniques for determining the coefficients may also be used. In step 306, the flashover prediction system 108 may estimate one or more parameters for the frame of measured data. The flashover prediction system 108 may substitute the measured variables in the statistical model to estimate the parameters such as, but not limited to, field circuit resistance, field current noise, ozone concentration, visible and UV light emission, audible noise, and so forth. Further the residue between the measured value and the predicted value of the dependent variable may be computed for all data points of the measured data. In step 308, the flashover prediction system 108 may use the estimated parameters for predicting a flashover condition. One embodiment of implementing step 308 is explained in conjunction with FIG. 4. The steps of both FIG. 3 are repeated on a rolling window basis. Once the steps of process are executed on a specific time window of the current frame of measured data, the window is advanced forward by a predefined number of data points. In an embodiment the window may be advanced by one data point. Once all the data points of the current frame are analyzed, the next frame may be acquired and the steps of FIG. 3 may be repeated on the next frame. FIG. 4 shows a flow chart for implementing step 408 according to an embodiment of the present invention. In step 402, the one or more estimated parameters are compared with a predefined threshold. In an embodiment of the present invention, the predefined threshold may be 1 percent of the measured variable. In step 404, a density count denoting the number of occurrences of the one or more parameters exceeding the predefined threshold is determined. In one embodiment, the density count may be converted to percentage of the total number of data points in the frame of measured data. In step 406 an occurrence interval between successive occurrences when the one or more parameters exceed the predefined threshold are determined. In one embodiment, the median value of the occurrence intervals is calculated. In step 408 a flashover is indicated based on the outcomes of at least one of steps 404, and 406. A flashover condition may be indicated if the density count is higher than a certain limit. In an embodiment of the present invention a flashover is indicated if the density count is higher that 1 percent of the total data points in the frame of measured data. A flashover is indicated only if the median of occurrence intervals obtained in step 406 is less than an occurrence limit. For example, the prediction module 208 may indicate a potential flashover condition if the density count exceeds 1% of the total number time instances for which the residue was computed and/or the median value of occurrence interval is less than 1 second. In another embodiment, the prediction module 208 uses the residue converted to a percentage of the actual measured value in the above comparisons to predict the potential flashover condition. In yet another embodiment, the prediction module 208 uses the estimated parameters in the above comparisons to predict the flashover condition. For example, the prediction module 208 may compare the estimated field circuit resistance with a predefined threshold, and determine the density count and the occurrence interval. The prediction module 208 may then indicate a potential flashover condition if the estimated field circuit resistance exceeds the density count limit and/or the estimated field circuit resistance exceeds the threshold more often than the median value of the occurrence interval. Embodiments presented herein may also be implemented using a computer system such as, but not limited to, a microprocessor based system, a microcontroller based system, and so forth. Such a computer system may include a non-transitory computer readable medium including instructions which cause the computer system to perform the methods described in the figures above. The computer readable medium may be any one of a Random Access Memory (RAM), Read Only Memory (ROM), Programmable Read Only Memory (PROM), Erasable Programmable Read Only Memory (EPROM), optical discs, magnetic storage media, and the like. Although the various embodiments of the present invention are described in conjunction with the generator 102, the embodiments may be applied to any other machine comprising a brush and collector ring assembly, such as a motor. The embodiments presented herein may be applied to any machine susceptible to failure due to a flashover in the collector. The present invention has been described in terms of several embodiments solely for the purpose of illustration. Persons skilled in the art will recognize from this description that such embodiments may be practiced with modifications and alterations limited only by the spirit and scope of the appended claims.
053032748	summary	BACKGROUND OF THE INVENTION The present invention relates to passive cooling of a nuclear reactor containment. The invention is particularly directed to an isolation condenser type passive cooling system which can be installed externally of the nuclear reactor containment as well as building structure in which the containment is situated, the cooling system being such as minimizes need to penetrate the containment and building enclosure with cooling system components. U.S. Pat. Nos. 5,059,385, 5,082,619 and 5,106,571 disclose use of isolation condensers in connection with passive removal of initial and decay heat loads generated in a nuclear reactor system containment as a result of and upon occurrence of a LOCA, i.e., a loss-of-coolant accident in the system. The cooling systems disclosed in these pending applications also can dissipate initial heat by venting the reactor pressure vessel and/or the containment drywell space to a suppression pool of water confined in a chamber surrounding the reactor pressure vessel. Venting to the suppression pool also can be used with respect to condensate recovery of the isolation condensers, and non-condensable gasses such as nitrogen, which are cooled in an isolation condenser and separated from the condensate. Venting from the containment drywell of heated, pressurized fluid and venting of condensate and non-condensable gasses from the isolation condensers to the suppression pool, is possible because a pressure differential exists between these fluids and gasses on the one hand, and the airspace above the suppression pool water on the other hand. In other nuclear reactor systems, LOCA heat loads are dissipated in different manner. For example, a type of nuclear system that was built in some numbers in the 1960's and 1970's has a containment which includes an upper space in which the nuclear reactor is disposed, and a lower space defining a suppression pool chamber in which cooling water is present with there being an airspace above the water. The upper and lower spaces are separated by a horizontal structural element, e.g., a concrete floor. A concrete pedestal extends upwardly a distance from the concrete floor in the upper space and serves as a mounting on which the reactor pressure vessel is received and supported. A plurality of vertically disposed vent tubes are arranged in circle array in the floor and have entry ends communicating with the upper space, lower outlet ends of these vent tubes locating submerged in the suppression pool water. On happening of a LOCA, initial heat is dissipated by heated, pressurized fluid present in the upper space or drywell venting through the vent pipes into the suppression pool wherein steam condenses and non-condensable gasses such as nitrogen cool and vent from the pool water to the airspace above the water. Initial heat also can be dissipated by recirculating water from the reactor vessel to a cooling operation (unless a reactor vessel rupture is present), which cooling operation may for environmental safety reason, involve an intermediate heat exchange location and a final heat exchange location, the latter being one outside the containment. Recirculation of the suppression pool water in like manner can be practiced to take into account that the suppression pool will heat up quite quickly. Decay heat dissipation will be handled by the same suppression pool and reactor vessel water recirculation functions. It is to be noted though that these systems do not employ passive heat removal capacity. While the last-discussed systems are designed to handle any anticipated LOCA heat load, there is a drawback and potential risk that the cooling function of the suppression pool as it regards non-condensable gasses, can be rendered ineffective. Such happening can come about if a reactor core meltdown attends the LOCA. In that event, the meltdown may cause or contribute to a breaching of the concrete floor structure thereby communicating the drywell of the upper space directly with the airspace above the pool in the lower space rather than such communication being indirect through the suppression pool first. The result is that no lower pressure space exists in the containment to which the higher pressure non-condensable gasses can be vented and cooled by passage through the suppression pool. The systems with the above-recited shortcoming embody massive containment structures. This works against conveniently and simply making system modifications to counter the effects of meltdown as described above and provide for cooling, both as to initial heat removal and the longer term decay heat dissipation. OBJECTS AND SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide nuclear reactor system satellite heat removal means in the form of a passive containment cooling system specially intended to be retrofittable to an existing nuclear reactor system of a type wherein a drywell space containing the nuclear reactor is located above and over a suppression pool which overcomes the drawbacks of the prior art. It is a further object of the invention to provide a passive containment cooling system which includes a wetwell airspace that serves as a location to which LOCA produced non-condensable gasses present in the containment can be vented in the event a reactor meltdown causes breach in the floor separating the containment drywell from an underlying suppression pool wetwell airspace, such happening thereby destroying presence in the containment of a lower pressure space to which gasses at a higher pressure can be vented. It is a still further object of the invention to readily and conveniently provide passive containment cooling for nuclear reactor systems of types heretofore lacking such cooling capacity. Briefly stated, there is provided a satellite heat removal means which can be embodied in a system as part of an original design but more particularly is intended to be retrofitted to an existing nuclear reactor system to serve optionally to supplement heat removal from the system nuclear reactor containment upon happening of a LOCA, and to assume all system containment drywell venting in the event reactor core meltdown results in breach of the containment floor structure separating the containment drywell and wetwell spaces, which breach would deprive the containment of a space to which non-condensable fraction of LOCA generated heated fluid in the containment could be vented, cooled and stored. The satellite heat removal means includes a structure external of but preferably situated alongside the nuclear reactor containment, a heat exchanger is disposed in a pool of cooling water located in an upper chamber of that structure, while a pool of water also is present in a structure lower chamber. The heat exchanger is communicated with the containment drywell by inlet and outlet conduits so that heated fluid in the containment can enter and be cooled in the heat exchanger with a cooled condensate fraction being returned to the drywell, and a non-condensable gas fraction vented to the lower chamber pool of water. A gas space above the lower chamber pool of water substitutes as the wetwell gas space to which non-condensables vent in place of the containment wetwell gas space that was breached and thus merged with the containment drywell space as an incident of the LOCA. In accordance with these and other objects of the invention, there is provided a nuclear reactor system which includes a containment structure having an upper drywell space and a lower wetwell space, these spaces being separated one from another by an intervening floor member. A nuclear reactor pressure vessel is disposed in the drywell space and a reactor core is present within the pressure vessel. A suppression pool of water is confined in the wetwell space and a gas space is present above a normal level of water in this suppression pool. Means are provided for venting a heated and pressurized fluid present in the structure drywell space incident a pressure vessel loss-of-coolant accident to a submerged location in the suppression pool thereby to remove heat from and reduce pressure in the drywell space by condensing a water fraction of the heated fluid in the suppression pool water, a non-condensable fraction of said heated fluid venting to the wetwell gas space. Satellite heat removal means are operable for effecting additional drywell heat removal during the accident and all drywell venting in the event the floor member structure is breached by a core meltdown during the loss-of-coolant accident with consequent merger of the gas space and drywell so that the containment lacks a space to which the heated fluid non-condensable fraction can vent. The satellite heating removal means includes a satellite structure external of the containment structure and has upper and lower chambers. At least one heat exchanger is located in the upper chamber and a pool of cooling water in the upper chamber surrounds the heat exchanger. Vent means communicate the cooling water with ambient environment. An inlet conduit communicates an inlet end of the heat exchanger with the containment drywell whereby heated fluid present in the containment drywell can flow into the heat exchanger with the containment drywell. An outlet conduit communicates an outlet end of the heat exchanger with the containment drywell. A condensate/non-condensable gas collector is in said outlet conduit. Condensate collected in the collector passes therefrom to the containment drywell and a non-condensable gas fraction collected in the collector passes into a vent pipe which vent pipe outlets submerged below a level of water in a water pool present in the lower chamber, there being a gas space in that chamber above the water level. The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
	description	The present application is a continuation application of International Patent Application No. PCT/JP2016/066165 filed on Jun. 1, 2016, which claims priority to Japanese Patent Application No. 2015-118980 filed on Jun. 12, 2015, the entire contents of which are incorporated by reference. The present invention relates to a measuring device. Patent Document 1 discloses an impurity particles measuring device that includes a light emitting diode emitting light to a pipe through which oil (hydraulic oil) or the like flows, two light receiving elements arranged apart from each other in a direction of the flow path of a fluid and detecting light transmitted through a flow path by the light emission, and a detecting section detecting an amount of impurity particles flowing in the flow path from differences in respective outputs of the light receiving elements, and that measures impurity particles, such as oil dust contained in the hydraulic oil and the like. Patent Document 1: JP 2013-142626 A The invention described in Patent Document 1 uses, as the pipe, a glass tube made from an optically transparent material, such as glass. Unfortunately, even in a case where the glass tube is made from, for example, high-strength sapphire glass, an increased pressure of the hydraulic oil or the like flowing in the pipe may generate a crack or the like in the glass tube and may thus increase a measurement error. One or more aspects of the present invention are directed to a measuring device that can be used under high pressure and can measure impurity particles contained in a hydraulic oil with high accuracy. A measuring device according to an aspect of the present invention includes, for example: a housing having two surfaces facing each other, the housing being provided with a flow path hole, a first cavity, and a second cavity, the flow path hole opening on the two facing surfaces and having a first side surface and a second side surface facing each other, the first cavity having one end opening on the first side surface, the second cavity facing the first cavity across a center axis of the flow path hole and having one end opening on the second side surface; a first cell disposed in the first cavity, made from a transparent material, and having a substantially cylindrical shape, both ends surfaces of the first cell being flat surfaces; a second cell disposed in the second cavity, made from a transparent material, and having a substantially cylindrical shape, both ends surfaces of the second cell being flat surfaces; a light emitting section configured to irradiate a hydraulic oil flowing in the flow path hole with light via the first cell in a direction substantially orthogonal to the center axis; and a light receiving section disposed facing the light irradiating section across the first cell, the flow path hole, and the second cell. The first cavity and the second cavity have centers substantially coinciding with an optical axis being a center of light emitted from the light irradiating section. In the measuring device according to an aspect of the present invention, the flow path hole having the center axis orthogonal to the two facing surfaces and having the first side surface and the second side surface facing each other is formed in the housing. This configuration enables the measuring device to be used under high pressure. In the measuring device according to an aspect of the present invention, light emitted from the light emitting section irradiates the hydraulic oil flowing in the flow path hole, via the first cell disposed in the first cavity opening on the first side surface in the direction substantially orthogonal to the center axis of the flow path hole, and is received by the light receiving section disposed facing the light emitting section across the first cell, the flow path hole, and the second cell disposed in the second cavity opening on the second side surface. This configuration enables measurement of impurity particles contained in the hydraulic oil to be highly accurate. Here, the flow path hole may have both ends shaped into a round cavity; and the flow path hole may have such a tapered shape that a shape in a plane substantially orthogonal to the center axis changes from the round cavity to a long cavity having two sides substantially orthogonal to the optical axis. This configuration stabilizes the flow of the hydraulic oil flowing in the measurement hole, resulting in an increase in the measurement accuracy. Here, the first side surface and the second side surface may be flat surfaces; an end surface of the first cell disposed in the first cavity and the first side surface may be substantially in the same plane; and an end surface of the second cell disposed in the second cavity and the second side surface may be substantially in the same plane. This configuration can reduce generation of swirls. Here, the tapered shape may be formed such that an angle formed by two lines facing across the center axis is approximately 60 degrees. This configuration prevents swirls from being generated in the hydraulic oil flowing in the measurement hole, resulting in a stable flow. Here, a distance between the first side surface and the second side surface may be smaller than a length of the first side surface and the second side surface in the direction substantially orthogonal to the center axis. This configuration shortens the distance between the light emitting section and the light receiving section, resulting in an increase in the measurement accuracy. Here, the first cell and the second cell each may include a main portion having a substantially cylindrical shape and a flange portion formed at an end of the main portion and having a substantially thick circular plate shape with a diameter greater than a diameter of the main portion. Sealing members may be disposed between the first cavity and the main portion and the second cavity and the main portion. The housing may be provided with first and second pressing members. The first and second pressing members are configured to press the first and second cells, respectively. With the pressing members being disposed in the housing, end surfaces, on the main portion side, of the flange portions may be pressed against the housing. This configuration can improve the measurement accuracy even in cases where vibrations, variations in the flow rate and pressure, or the like occurs. According to one or more aspects of the present invention, the measuring device can be used under high pressure and can measure impurity particles contained in a hydraulic oil with high accuracy. Embodiments of the present invention will be described in detail below with reference to the drawings. A pollution level measurement device 1 is provided in an apparatus 100, such as construction machinery and a hydraulic device, that uses a hydraulic oil to perform a desired operation. FIG. 1 illustrates an overview of the apparatus 100. The apparatus 100 includes a housing 103 provided with a main flow path 101 and a bypass flow path 102 in which a hydraulic oil to be measured flows. The pollution level measurement device 1 is disposed in such a desired position in the apparatus 100 as to include the bypass flow path 102. The thick arrows in FIG. 1 indicate a flow of the hydraulic oil in the apparatus 100. The hydraulic oil flows from a −x direction toward a +x direction in the main flow path 101. The hydraulic oil flowing in the main flow path 101 partially flows into the bypass flow path 102 and is supplied to the pollution level measurement device 1. The hydraulic oil flowing out from the pollution level measurement device 1 passes through the bypass flow path 102 and returns to the main flow path 101. FIG. 2 is a cross-sectional view illustrating an overview of the pollution level measurement device 1. The pollution level measurement device 1 mainly includes a housing 10, glass cells 21, O-rings 22, a plug 23, packings 24, a light emitting section substrate 25, a plug 26, a light receiving section substrate 27, and a block 28. Note that, in FIG. 3, the hatching indicating a cross section is partially omitted. The housing 10 is a substantially rectangular member made from metal (such as iron and aluminum), for example. The housing 10 has a body 10A (see FIGS. 3 to 6) mainly provided with a measurement flow path 11 through which the hydraulic oil to be measured flows, holes 12, 13 serving as windows for guiding light into and out of the measurement flow path 11, a cavity 14 into which the plug 23 is attached, and a cavity 15 into which the plug 26 is attached. The measurement flow path 11 has openings in a side surface on a −x side and a side surface on a +x side of the body 10A. A center axis P of the measurement flow path 11 is orthogonal to the side surface on the −x side and the side surface on the +x side. The measurement flow path 11 has a side surface Ba and a side surface Bb that are flat surfaces parallel with the center axis P. The holes 12, 13 are formed facing each other across the center axis P. One end of each of the holes 12, 13 opens to the measurement flow path 11. The hole 12 communicates with the cavity 14, and the hole 13 communicates with the cavity 15. The centers of the holes 12, 13 and the cavities 14, 15 are substantially orthogonal to the center axis P. Note that the shape of the housing 10 is not limited to a substantially rectangular shape. The housing 10 may have any shape that has two facing surfaces on which the measurement flow path 11 opens. The housing 10 will be described in detail later. The glass cells 21 are substantially cylindrical members made from an optically transparent material (such as glass). The glass cells 21 each include a main portion 21A having a substantially cylindrical shape and a flange portion 21B having a substantially thick circular plate shape with a diameter greater than a diameter of the main portion 21A. The glass cells 21 are disposed in the holes 12, 13. Since the holes 12, 13 open to the measurement flow path 11, end surfaces 21a of the glass cells 21 disposed in the holes 12, 13 directly come into contact with the hydraulic oil flowing in the measurement flow path 11. The end surfaces 21a of the glass cells 21 disposed in the holes 12, 13 and the side surfaces 11Ba, 11Bb of the measurement flow path 11 are substantially in the same plane. Since the end surfaces 21a of the glass cells 21 and the side surfaces 11Ba, 11Bb are substantially in the same plane, swirls can be prevented from being generated in the hydraulic oil flowing in the measurement flow path 11 around the glass cells 21. The O-rings 22 are annular packings having a substantially circular cross section, for example. When the glass cells 21 are disposed in the holes 12, 13, the O-rings 22 are disposed between the holes 12, 13 and the glass cells 21. The O-rings 22 function as sealing members that elastically deform between the holes 12, 13 and the glass cells 21 to prevent the hydraulic oil from leaking from between the holes 12, 13 and the glass cells 21. The plug 23 is a substantially cylindrical member made from metal (such as aluminum). A screw 23A is formed on the outer periphery of the plug 23. By engaging the screw 23A with a screw 14A formed on the inner periphery of the cavity 14, the plug 23 is attached to the housing 10. The plug 23 has a recess 23B formed having substantially the same diameter as a diameter of the flange portion 21B. The flange portion 21B fits in the recess 23B. The packings 24 are substantially cylindrical plate shaped members made from metal (such as brass). A packing 24 is disposed between the recess 23B and the flange portion 21B. When the screw 23A is engaged with the screw 14A to attach the plug 23 to the housing 10, the plug 23 presses an end surface 21b of the flange portion 21B via the packing 24. As a result, an end surface 21c, on the main portion 21A side, of the flange portion 21B is pressed against the body 10A. The contact surface between the end surface 21c and the body 10A has a substantially circular plate shape, such that the glass cell 21 is supported on the surface. This configuration allows the glass cell 21 to be securely fixed to the hole 12. Note that, e.g., as an alternative embodiment, the plug 23 may be applied without the packing 24 to press the flange portion 21B directly. The light emitting section substrate 25 is provided with a light emitting section (for example, an LED) 25A emitting light. Light emitted from the light emitting section 25A passes through the glass cell 21 disposed in the hole 12 and irradiates the hydraulic oil flowing in the measurement flow path 11. The light emitting section substrate 25 is attached to the plug 23 with screws. The light emitting section 25A is inserted into a hole 23C formed in the plug 23, such that an optical axis O being the center of the light emitted from the light emitting section 25A is positioned substantially coinciding with the center axes of the holes 12, 13. The light emitting section 25A is disposed adjacent to the flange portion 21B. The light emitted from the light emitting section 25A enters the glass cell 21 from a direction orthogonal to the flat end surface 21a of the glass cell 21. Thus, the light emitted from the light emitting section 25A passes through the glass cell 21 along the center axis (substantially coinciding with the optical axis O) of the glass cell 21, without diffusing on the end surface 21a. The end surface 21b of the glass cell 21 is also flat, such that light passing through the glass cell 21 exits in a direction orthogonal to the end surface 21b. Thus, the light emitted from the light emitting section 25A irradiates the hydraulic oil in the measurement flow path 11 without diffusing. Similar to the plug 23, the plug 26 is a substantially cylindrical member made from metal (such as aluminum). A screw 26A is formed on the outer periphery of the plug 26. By engaging the screw 26A with a screw 15A formed on the inner periphery of the cavity 15, the plug 26 is attached to the housing 10. The plug 26 has a recess 26B formed having substantially the same diameter as the diameter of the flange portion 21B. The flange portion 21B fits in the recess 26B. When the screw 26A is engaged with the screw 15A to attach the plug 26 to the housing 10, the plug 26 presses the flange portion 21B via the packing 24. As a result, the end surface 21c of the flange portion 21B is pressed against the body 10A. This configuration allows the glass cell 21 to be fixed to the hole 13. Note that the positional relationship between the hole 13 and the glass cell 21 and the method of attaching the glass cell 21 to the hole 13 are the same as the positional relationship between the hole 12 and the glass cell 21 and the method of attaching the glass cell 21 to the hole 12. The light receiving section substrate 27 is provided with a light receiving element 27A detecting light transmitted resulting from the light emission. The light receiving element 27A is, for example, a photodiode (PD) and is disposed facing the light emitting section 25A across the measurement flow path 11 and the glass cells 21. The light receiving element 27A is disposed on the optical axis O. Light emitted from the light emitting section 25A and not reflected by impurity particles contained in the hydraulic oil in the measurement flow path 11 enters the glass cell 21 from a direction orthogonal to the end surface 21b. Light passing through the glass cell 21 exits in a direction orthogonal to the end surface 21a. Thus, most of the light emitted from the light emitting section 25A and not reflected by impurity particles contained in the hydraulic oil in the measurement flow path 11 (light that passed through the hydraulic oil) is received by the light receiving element 27A. The light receiving section substrate 27 is attached to the block 28 with screws. The block 28 is fixed to the housing 10 by screwing or the like. Note that no such limitation is intended for attaching the light receiving section substrate 27, and the light receiving section substrate 27 may be fixed to the plug 26 by screwing, for example. Next, the housing 10 will be described in detail. FIG. 3 is a perspective view of the housing 10. The measurement flow path 11 extending from the −x side surface to the +x side surface of the body 10A is formed in the body 10A. The cavity 14 is formed in a +y side surface of the body 10A, and the cavity 15 is formed on a −y side surface of the body 10A. The measurement flow path 11 will be described in detail below. FIG. 4 is a cross-sectional view of the housing 10 in plane A in FIG. 3. FIG. 5 is a cross-sectional view of the housing 10 in plane B in FIG. 3. FIG. 6 is a cross-sectional view taken along line C-C in FIG. 5. The measurement flow path 11 includes substantially cylindrical screw portions 11A formed on both sides of the measurement flow path 11, a long cavity portion 11B having a cross section shaped into a long cavity when cut in a plane substantially parallel with an yz plane, and linking portions 11C gradually linking the screw portions 11A with the long cavity portion 11B. The screw portions 11A are each coupled with another component, for example, a joint that includes a flow path having a substantially circular cross section. The screw portion 11A disposed on the −x side serves as an inflow section allowing the hydraulic oil to flow into the measurement flow path 11, and the screw portion 11A disposed on the +x side serves as an outflow section allowing the hydraulic oil to flow out from the measurement flow path 11. The long cavity portion 11B has the side surfaces 11Ba, 11Bb. The side surfaces 11Ba, 11Bb are flat surfaces with their longitudinal direction substantially parallel with the x direction (see FIG. 4) and face each other across the center axis P (see FIGS. 5 and 6). One end of the hole 12 opens on the side surface 11Ba, and one end of the hole 13 opens on the side surface 11Bb (the hole 13 is not illustrated in FIG. 4). As illustrated in FIG. 6, the shape of the cross section in a plane substantially orthogonal to the center axis P of the measurement flow path 11 (hereinafter referred to as “cross-sectional shape”) of the long cavity portion 11B is a long cavity. The long cavity portion 11B has two linear sides 11a, 11b extending in a direction (z direction) substantially orthogonal to the optical axis O and curved sides 11c connecting the sides 11a, 11b, in the plane substantially orthogonal to the center axis P. The side 11a composes part of the side surface 11Ba, and the side 11b composes part of the side surface 11Bb. In the present embodiment, the sides 11a, 11b have a length 11 of approximately 11 mm, and the long cavity portion 11B has a width 12 of approximately 14 mm and a thickness (distance between the side 11a and the side 11b) t of approximately 3 mm. In this way, the thickness t of the long cavity portion 11B is sufficiently smaller than the length 11 of the sides 11a, 11b (the length of the side surfaces 11Ba, 11Bb in a direction substantially orthogonal to the center axis P) and the width 12 of the long cavity portion 11B. The linking portions 11C have such a tapered shape that the cross-sectional shape of the flow path gradually changes from a round cavity being the cross-sectional shape of the screw portions 11A to the long cavity being the cross-sectional shape of the long cavity portion 11B. The linking portions 11C have a substantially truncated cone shape. As illustrated in FIG. 4, the holes connecting the linking portions 11C with the long cavity portion 11B in plane A have a substantially triangular shape protruding toward the center of the housing 10. The width 12 of the long cavity portion 11B is substantially the same as the diameter of the screw portion 11A. Note that the diameter of the screw portion 11A is only required to be greater than or equal to the width 12 of the long cavity portion 11B and is not limited to being substantially the same as the width 12 of the long cavity portion 11B. The linking portions 11C are each formed such that an angle θ formed by two lines facing across the center axis P is approximately 60 degrees in plane A and plane B that contain the center axis P. The angle θ will be described in detail later. The action of the pollution level measurement device 1 thus configured will be described with reference to FIG. 2. In FIG. 2, the solid arrows indicate the flow of the hydraulic oil, and the hollow arrows indicate a path of the light. The hydraulic oil flows into the pollution level measurement device 1 from the inflow section being the screw portion 11A formed on the −x side of the housing 10. The hydraulic oil introduced from the inflow section passes through the linking portion 11C and flows into the long cavity portion 11B. The hydraulic oil introduced into the long cavity portion 11B flows downstream in the long cavity portion 11B (in the direction from −x toward +x) and flows out of the pollution level measurement device 1 from the outflow section being the screw portion 11A formed on the +x side of the housing 10. The hydraulic oil flowing downstream in the long cavity portion 11B is irradiated with light from the light emitting section 25A. The light emitted from the light emitting section 25A enters the glass cell 21 from the end surface 21b, passes through the glass cell 21, and is incident on the hydraulic oil in the measurement flow path 11 from the end surface 21a. The light passing through the measurement flow path 11 enters the glass cell 21 from the end surface 21a, passes through the glass cell 21, and exits from the end surface 21b. The light receiving element 27A receives the light exiting from the end surface 21b. In the present embodiment, the light emitting section 25A continuously emits light. The light receiving element 27A continuously receives light. An output signal from the light receiving element 27A is amplified by an amplifier. The amount of impurity particles contained in the hydraulic oil flowing in the measurement flow path 11 is measured on the basis of the amplified signal. The description of a method of measuring the amount of impurity particles is omitted because various techniques are already known. The output signal from the light receiving element 27A may be processed by an electric circuit or a microcomputer (not illustrated) provided in the pollution level measurement device 1 or by a device other than the pollution level measurement device 1. The light receiving element 27A continuously receives light. Thus, in a case where the flow of the hydraulic oil flowing in the measurement flow path 11 is disturbed, the measurement accuracy decreases. Use of the linking portions 11C having the angle θ of approximately 60 degrees in the present embodiment stabilizes the flow of the hydraulic oil and can thus increase the measurement accuracy. This point will be described in detail below. FIG. 7 is a schematic view illustrating a flow of the hydraulic oil in a case of the linking portion 11C having the angle θ of approximately 60 degrees (in the present embodiment). FIG. 8 is a schematic view illustrating a flow of the hydraulic oil in a case of a linking portion 11C′ having the angle θ of approximately 120 degrees (in Comparative Example). FIG. 9 is a schematic view illustrating the flow of the hydraulic oil in a case of no linking portion is provided (in Comparative Example). Only the linking portion is different among FIGS. 7 to 9. The lines illustrated in FIGS. 7 to 9 indicate path lines in simulations of the flow of the hydraulic oil. Note that, although a pipe thinner than the screw portion 11A is provided on the left side of the measurement flow path 11 via the screw portion 11A in FIGS. 7 to 9, the pipe is not limited to having such a diameter. As illustrated in FIG. 7, in the case of the angle θ is approximately 60 degrees, swirls are generated around the linking portion 11C, whereas no swirl is generated in the vicinity of the optical axis O. On the other hand, as illustrated in FIG. 8, in the case of the angle θ is approximately 120 degrees, swirls are continuously generated around the linking portion 11C toward the downstream side in the vicinities of both ends of the long cavity portion 11B. In the case illustrated in FIG. 9, swirls are generated even at the center portion of the long cavity portion 11B (in the vicinity of the center axis P). A swirl disturbs movement of impurity particles contained in the hydraulic oil. This disturbance may cause multiple measurements of the same impurity particle. It is thus desirable to minimize generation of swirls to increase the measurement accuracy. In the case illustrated in FIG. 8, swirls are generated only in the vicinities of both ends of the long cavity portion 11B. Thus, by making an even longer flow path, swirls can be minimized to such an extent that a measurement error can be ignored. However, in the case where no linking portion is provided as illustrated in FIG. 9, swirls remain generated even with a longer flow path, and impurity particles cannot be measured. Thus, the linking portions 11C, 11C′ having such a tapered shape that the cross-sectional shape of the flow path gradually changes are required to be disposed between the screw portions 11A and the long cavity portion 11B. To prevent a swirl from being generated in a position other than the linking portions, the angle θ of the tapered shape is desirable to be approximately 60 degrees. According to the present embodiment, the measurement flow path 11 is formed directly in the housing 10, such that the pollution level measurement device 1 can be used under high pressure. In a case where the measurement flow path is formed with a glass tube, for example, an increase in pressure of a hydraulic oil or the like flowing in the pipe may generate a crack or the like in the measurement flow path. In contrast, by forming a hole serving as the measurement flow path 11 in the housing 10, generation of a crack or the like in the measurement flow path 11 can be prevented even under high pressure. In the present embodiment, the substantially cylindrical glass cells 21 are used as windows for guiding light into and out of the measurement flow path 11, such that the pollution level measurement device 1 can be used under high pressure. In the case where the measurement flow path is formed with a glass tube, for example, the glass tube exhibits low pressure resistance due to its curved surface. In contrast, the glass cells 21 have the flat end surfaces and are thick and rigid. Thus, generation of a crack or the like in the glass cells 21 can be prevented even under high pressure. In the present embodiment, no curved surface is present on an optical path from the light emitting section 25A to the light receiving element 27A, such that impurity particles contained in the hydraulic oil can be measured with high accuracy. In the case where the measurement flow path is formed with a glass tube, for example, light is refracted in varies directions by the surface of the glass tube because of the curved surface of the glass tube. In contrast, light emitted from the light emitting section 25A enters or exits in the direction orthogonal to the flat end surfaces of the glass cells 21. Thus, the light emitted from the light emitting section 25A irradiates the hydraulic oil in the measurement flow path 11 as it is without diffusing. Accordingly, the measurement accuracy can be increased. In the present embodiment, the long cavity portion 11B has a small thickness, such that the optical path, that is, the distance between the light emitting section 25A and the light receiving element 27A, is shortened, resulting in an increase in the measurement accuracy. According to the present embodiment, the linking portions 11C having such a tapered shape that the cross-sectional shape of the measurement flow path 11 changes from a round cavity to a long cavity stabilize the flow of the hydraulic oil, resulting in an increase in the measurement accuracy. According to the present embodiment, the end surfaces 21a of the glass cells 21 and the side surfaces 11Ba, 11Bb of the measurement flow path 11 are substantially in the same plane, such that swirls are prevented from being generated in the hydraulic oil flowing in the measurement flow path 11 around the glass cells 21, resulting in an increase in the measurement accuracy. In a case where the glass cells 21 protrude in the measurement flow path 11, for example, the hydraulic oil flowing in the measurement flow path 11 collides against the glass cells 21 and thus generating swirls. In contrast, in a case where the end surfaces 21a and the side surfaces 11Ba, 11Bb are substantially in the same plane, the glass cells 21 do not disturb the flow of the hydraulic oil, resulting in prevention of swirls from being generated around the glass cells 21, that is, in the vicinity of the optical axis O. Accordingly, the measurement accuracy can be increased. According to the present embodiment, when the glass cells 21 are attached to the housing 10, the end surfaces 21c of the flange portions 21B come into contact with the housing 10, resulting in an improvement in vibration resistance. In the case where the measurement flow path is formed with a glass tube, for example, vibration of the pollution level measurement device 1 may cause the glass tube to vibrate more vigorously than the pollution level measurement device 1 because periphery of the glass tube is fixed. In contrast, in a case where the glass cells 21 and the housing 10 come into surface contact with each other, the glass cells 21 can be pressed against the housing 10 with strong force. Thus, even in the case where the pollution level measurement device 1 vibrates, the glass cells 21 are less likely to vibrate with the pollution level measurement device 1 (improve in vibration resistance). Furthermore, since the glass cells 21 and the housing 10 come into surface contact with each other, variations in the flow rate or pressure of the hydraulic oil flowing in the measurement flow path 11 are less likely to cause vibration of the glass cells 21. Accordingly, the measurement accuracy can be improved. Note that in the present embodiment, the thickness t of the long cavity portion 11B (approximately 3 mm) is sufficiently smaller than the length 11 of the sides 11a, 11b (approximately 11 mm) and the width 12 of the long cavity portion 11B (approximately 14 mm) in the plane substantially orthogonal to the center axis P of the measurement flow path 11; however, the cross-sectional shape of the long cavity portion 11B is not limited to this configuration. For example, the long cavity portion 11B may have a thickness t of greater than approximately 3 mm. However, in order to increase the measurement accuracy, it is desirable to minimize the thickness t of the long cavity portion 11B to shorten the optical path. In the present embodiment, the cross-sectional shape of the long cavity portion 11B is a long cavity having the two linear sides 11a, 11b extending in the direction (z direction) substantially orthogonal to the optical axis O but the cross-sectional shape of the long cavity portion 11B is not limited to this configuration. For example, the cross-sectional shape of the long cavity portion may be substantially rectangular. However, in order to shorten the optical path, it is desirable that the length of the long cavity portion in the y direction (direction parallel with the optical axis O) is shorter than the length of the long cavity portion in the z direction. Alternatively, the cross-sectional shape of the long cavity portion may be substantially oval, for example. In this case, the minor axis of the substantially oval shape may be substantially parallel with the y direction, the major axis may be substantially parallel with the z direction, and a portion on the +y side and a portion on the −y side may be side surfaces of the long cavity portion. These side surfaces of the long cavity portion are curved, and the glass cells 21 thus partially protrude from the side surfaces of the long cavity portion. However, the amount of the protrusions of the glass cells 21 is small depending on the oval shape, such that even in a case where a swirl is generated, the swirl does not affect the measurement accuracy. In order to prevent generation of swirls, it is desirable that the cross-sectional shape of the long cavity portion is a long cavity. In the present embodiment, the measurement flow path 11 includes the screw portions 11A, the long cavity portion 11B, and the linking portions 11C; however, the measurement flow path 11 is not limited to having this shape. For example, in a case where the cross-sectional shape of the bypass flow path 102 is a long cavity, the measurement flow path may include only the long cavity portion 11B. However, in a case where the cross-sectional shape of the bypass flow path 102 is a round hole, it is desirable that the linking portions 11C are formed on both ends of the long cavity portion 11B. In the first embodiment of the present invention, the measurement flow path 11 includes the screw portions 11A, the long cavity portion 11B, and the linking portions 11C, and the diameter of the round cavities of the screw portions 11A (on both ends of the measurement flow path 11) is substantially equal to the width of the long cavity portion 11B. However, the measurement flow path 11 is not limited to having this shape. In the first embodiment of the present invention, the diameter of the round cavities on both ends of the measurement flow path 11 is smaller than the width of the long cavity portion 11B. A pollution level measurement device 2 according to a second embodiment will be described below. Note that the same components as those in the first embodiment are denoted using the same reference signs, and descriptions thereof will be omitted. The pollution level measurement device 2 mainly includes a housing 10-1, the glass cells 21, the O-rings 22, the plug 23, the packings 24, the light emitting section substrate 25, the plug 26, the light receiving section substrate 27, and the block 28. FIG. 10 is a cross-sectional view illustrating an overview of the housing 10-1. The housing 10-1 is a substantially rectangular member made from metal (such as aluminum). The housing 10-1 has a body 10A-1 mainly provided with a measurement flow path 11-1, the holes 12, 13, the cavity 14, and the cavity 15. The measurement flow path 11-1 mainly includes the long cavity portion 11B and guiding portions 11D disposed on both ends of the long cavity portion 11B. The guiding portions 11D each have one end communicating with the long cavity portion 11B and the other end opening on an end surface of the housing 10-1. The opening formed on the end surface of the housing 10-1 has a substantially circular shape. The guiding portions 11D have such a tapered shape that the cross-sectional shape of the flow path gradually changes from a round cavity to the long cavity being the cross-sectional shape of the long cavity portion 11B. The guiding portion 11D disposed on the −x side serves as an inflow section allowing the hydraulic oil to flow into the measurement flow path 11-1, and the guiding portion 11D disposed on the +x side serves as an outflow section allowing the hydraulic oil to flow out from the measurement flow path 11-1. FIGS. 11 and 12 illustrate a shape of the guiding portion 11D. FIG. 11 is a cross-sectional view, and FIG. 12 is a view taken a long line D in FIG. 11. The body 10A-1 is omitted in FIG. 12. The opening 11d formed on the end surface of the housing 10-1 is a round cavity having a diameter smaller than the width 12 of the long cavity portion 11B and greater than the thickness t of the long cavity portion 11B. Similar to the first embodiment, an angle θ formed by two lines facing across the center axis P of the guiding portion 11D is approximately 60 degrees. According to the present embodiment, the circular pipe is gradually changed to the long cavity, such that swirls are not being generated in the hydraulic oil flowing in the measurement flow path 11-1, resulting in a stable flow. Accordingly, impurity particles contained in the hydraulic oil can be measured with high accuracy. For example, in the first embodiment, the cross-sectional area of the measurement flow path 11 becomes smaller, such that swirls are generated in the vicinities of the linking portions 11C. In contrast, in the present embodiment, the cross-sectional shape is changed gradually from a circle to the long cavity without a significant change in the cross-sectional area of the measurement flow path 11-1. Thus, the flow of the hydraulic oil is further stabilized, resulting in prevention of generation of swirls. Embodiments of the invention have been described in detail with reference to the drawings; however, specific configurations are not limited to the embodiments, and changes in the design or the like are also included within a scope which does not depart from the gist of the invention. For example, the above examples have been explained in detail in order to facilitate understanding of the present invention and are not necessarily limited to examples provided with the entirety of the configuration described above. In addition, a part of the configuration of an embodiment may be replaced with the configuration of another embodiment and the configuration of another embodiment may be added to, deleted from, or replaced with the configuration of an embodiment. Further, in the present invention, “substantially/approximately” is a concept that includes variation or modification to the extent that sameness is not lost, and does not only mean strictly the same. For example, “substantially orthogonal” is not limited to being strictly orthogonal, and is a concept that includes an error of several degrees, for example. Further, simple expressions such as orthogonal, parallel, and matching are not to be understood as merely being strictly orthogonal, parallel, matching, and the like, and include being substantially parallel, substantially orthogonal, substantially matching, and the like. Furthermore, the meaning of the term “in the vicinity” in the present invention includes a region of a range (which can be determined as desired) near a position serving as a reference. For example, “in the vicinity of the end” refers to a region of a range near the end, and is a concept indicating that the end may or may not be included. 1, 2 Pollution level measurement device 10, 10-1 Housing 10A, 10A-1 Body 11, 11-1 Measurement flow path 11A Screw portion 11B Long cavity portion 11Ba, 11Bb Side surface 11C Linking portion 11C′ Linking portion 11D Guiding portion 11a, 11b Side 11c Side 11d Opening 12, 13 Hole 14 Cavity 14A Screw 15 Cavity 15A Screw 21 Glass cell 21A Main portion 21B Flange portion 21a, 21b End surface 22 O-ring 23 Plug 23A Screw 23B Recess 23C Hole 24 Packing 25 Light emitting section substrate 25A Light emitting section 26 Plug 26A Screw 26B Recess 27 Light receiving section substrate 27A Light receiving element 28 Block 100 Apparatus 101 Main flow path 102 Bypass flow path 103 Housing
	claims	1. A scanned ultraviolet-light emitting diode (UV-LED) exposure device, comprising:a set of upper exposure station and a lower exposure station having a distance therebetween, the upper exposure station having a lower surface and the lower exposure station having an upper surface, each of the lower and upper surfaces having a substrate coated with a resist layer composed of a photo-sensitive material thereon, and the respective substrate of the upper and lower exposure stations being taken as a linear object exposure area having a vertical direction;a UV-LED illumination unit, being a 2-D matrix composed of a plurality of LEDs lying on a plurality of stripes, each of the stripes having a designated number of LEDs, respectively, having a horizontal direction and a vertical direction and arranged in parallel, being separated from each other for each pair of adjacent ones thereamong, having one of the designated number of LEDs in the horizontal direction thereof and having the vertical direction in perpendicular with the vertical direction of the linear object exposure area; anda periodic moving ring assembly, arranged on a center position between the upper and lower exposure stations in the exposure unit, having a first end, a second end, an inner circumference and an outer circumference having the plurality of UV-LED stripes thereon,wherein the periodic moving ring assembly continuously moves in an exposure task in a fixed rate, so as to expose the linear object exposure area of the upper and lower exposure stations. 2. The device according to claim 1, wherein the periodic moving ring assembly comprises:an active wheel, arranged at the first end of the periodic moving ring assembly to drive the periodic moving ring assembly to rotate;a passive wheel group, arranged within the inner circumference of the periodic moving ring assembly and comprising a plurality of passive wheels to bear the periodic moving ring assembly, the plurality of stripes and the plurality of LEDs to assist in a smooth rotation of the periodic moving ring assembly;a guiding wheel, arranged on the second end opposed to the first end of the periodic moving ring assembly to assist in the smooth rotation of the periodic moving ring assembly; andan active heat sinking element, arranged within the periodic moving ring assembly to actively heat sink the periodic moving ring assembly. 3. The device according to claim 2, wherein the periodic moving ring assembly is a double-layered structure formed of the active wheel and the guiding wheel and moving in a horizontal direction. 4. The device according to claim 2, wherein adjacent ones of the plurality of passive wheels are arranged with a distance to each other and the passive wheel group has a distance from the active wheel and the guiding wheel in the periodic moving ring assembly. 5. The device according to claim 2, wherein the active heat sinking element includes a water-cooled element and an air-cooled element. 6. The device according to claim 1, wherein the LED has a secondary optical element and an LED light source. 7. The device according to claim 6, wherein the secondary optical element includes a lens and a reflector. 8. The device according to claim 1, wherein each of the plurality of stripes includes a lens stripe and a reflector stripe. 9. The device according to claim 1, wherein the LED matrix further has a diffusing plate thereabove totally covering the plurality of LEDs. 10. The device according to claim 9, wherein the diffusing plate is an entire sheet structure. 11. The device according to claim 9, wherein the diffusing plate is a rib structure. 12. The device according to claim 9, wherein the diffusing plate is a structure having a plurality of stripes. 13. The device according to claim 9, wherein the diffusing plate is made of a UV-transparent material and includes quartz and glass. 14. The device according to claim 1, wherein when the periodic moving ring assembly rotates upward and downward at the first and second ends, respectively, the ones of the plurality of LEDs at the first and second ends are further each controlled as being turned off, respectively. 15. The device according to claim 1, wherein each of the plurality of stripes is arranged in the vertical direction thereof in parallel with the vertical direction of the linear object exposure area. 16. The device according to claim 1, wherein the designated number of LEDs in the adjacent ones of the plurality of stripes are alternatively arranged to each other, respectively.
	summary
	summary
	description	This application is a continuation-in-part and claims priority under 35 U.S.C. §120 to United States Non-Provisional application Ser. No. 12/476,646 filed Jun. 2, 2009, in the name of the present inventor and entitled “X-Ray Cassette Cover” which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/058,013 filed Jun. 2, 2008, in the name of the present inventor and entitled “X-Ray Cassette Cover”, both applications being incorporated herein by reference. Not Applicable. The present invention relates to a disposable, sterile or non sterile cover for enclosing a non-sterile article and a method for enclosing the non-sterile article. More specifically, the present disclosure relates to a cover for an X-ray cassette. The cover is disposable to prevent the spread of germs, aiding in infection control, cassette protection and more convenient handling of patients by healthcare professionals. In conventional radiography (also known as “X-ray photography” or “X-ray procedure), a plate is made by forming one or more emulsion layers on a flexible film base which is supported within a light-tight, non-sterile cassette. The interior of the cassette is coated with one or more X-ray sensitive luminescent layers. In use, the non-sterile cassette must be isolated from the sterile site or field of operation. During use, the health care professional loads the cassette containing an unexposed X-ray plate into an X-ray machine or positions the cassette in patient contact whichever is appropriate for an ordered exam. After exposure, the health care professional removes the exposed cassette and X-ray plate for development and subsequent fixing of the latent image produced. It will be appreciated by those skilled in the art that X-ray cassettes are one of the few medical devices which are reused. In particular, X-ray cassettes are reused from one patient after another in X-ray departments all around the world. The cassettes are reused since the cassettes are expensive, limiting cassette access to X-ray departments due to budget restrictions. It will further be appreciated by those skilled in the art that X-ray cassettes can be very impersonal and very uncomfortable to the patient. For example, X-ray cassettes used in portable radiography and tabletop radiography are cold and hard. Often times, patients must be placed on the X-ray cassette, thereby making the patient less comfortable and less cooperative. X-ray cassettes, during their repeated use, may directly contact the patient's skin or patient's fluids leading to unsanitary conditions as germs of one patient pass onto another patient and/or the health care personnel handling the X-ray cassette. Germs such as Staph can unknowingly pass from patient to patient, therefore leading to a large contribution to the loss of life. Hospital acquired infection is a leading cause of death in the United States. According to the Center for Disease Control, 2 million hospital-acquired infections occur each year. In some instances where X-rays are required to be taken during trauma cases, the cassette is often contaminated with the blood of a patient and these contaminants may be potential health hazards to the health care professional who must handle the X-ray cassette for development. Further, dangers from bacteria exist to personnel handling the X-ray cassette. Accordingly, protecting cassettes from contamination is highly desirable for safety reasons. Cleaning cassettes, however, results in disadvantages such as: inconvenience and time committed by the personnel; cleaning agents may contain carcinogens; chemical hazards of repeated use; and, long term exposure effects to personal, patients and equipment. Cassettes are also very expensive; and once blood and other fluids seep into the cassettes, the cassettes have to be repaired or replaced. Health care professionals can use cassette covers to enclose the cassette during an X-ray procedure. Current cassette covers, however, are made of plastic. These plastic covers, however, adhere to the patient's skin via the patient's sweat, blood or other fluids leading to uncomfortable conditions for the patient and to unwieldy handling by the health care professional. Existing plastic covers do not cushion the patient or absorb the patient's fluids. Health care professionals require cassette covers that aid in patient protection, patient comfort, increased ease of procedure and environmental concerns. The present disclosure relates to a sterile cover configured to enclose an X-ray cassette during a radiography procedure. The cover comprises a body having a first sheet and a second sheet comprised of a radiolucent material. The first sheet and the second sheet have pairs of opposing ends with one pair of opposing ends being closed and the other pair of opposing end being open to form a sleeve between the first sheet and the second sheet. The sleeve is sized and shaped to accept the X-ray cassette during the radiography procedure. The cover further comprises a movable band that forms a barrier with respect to the sleeve to isolate the X-ray cassette during the radiography procedure. Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. The following detailed description illustrates the disclosure by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the disclosure. The present disclosure relates to a cover for a medical device. The cover can be used in any appropriate medical device. However, for purposes of illustration only, the cover will be described as incorporated into a cover for an X-ray cassette. Referring to the drawings, an X-ray cassette 10 comprises a body 12 which supports and protects a photoreceptive medium such as an X-ray film/image 14. The body 12 comprises a top 16, a bottom 18 and sides 20 connecting the top 16 and the bottom 18, wherein the top 16, bottom 18 and sides 20 have predetermined wall thicknesses. The top 16, bottom 18 and sides 20 form an enclosure therein for accepting and enclosing the X-ray film/image 14. The top 16 or one of the sides 20 includes a hinge 22 and an openable lid 24 to allow access to the enclosure. This openable lid 24 is connected to and movable relative to the enclosure to allow the lid to swing open for insertion and extraction of the X-ray film/image 14. Generally, cassettes 10 are available in length and height dimensions such as, but not limited to, 8″×10″, 10″×12″, 11″×14″ and 14″×17″. Some cassettes 10 incorporate an exterior grid (not shown) which enhances the quality of the resultant image of the X-ray film 14. Thus, the grid increases the overall dimension of the cassette 10. For example, for a 10″×12″ cassette having the grid, the external dimensions of the cassette 10 are 10 15/16″×13¼″ and for a 14″×17″ cassette having the grid, the external dimensions of the cassette are 15½″×18½″. The body 12, in which the photoreceptive medium sets, can be constructed of lightweight materials such as a thermoplastic material. Further, the body 12 can have a variety of shapes such as elliptical, oval, circular, triangular, square, rectangular or any other appropriate configuration. As shown, the body 12 has a square shape. A cover 26 of the present disclosure is sized and shaped to enclose the cassette 10 for handling and processing the cassette 10 by the health care professional. The cover 26 comprises a first sheet 28, a second sheet 30 and seals 32 connecting the first sheet 28 and the second sheet 30. In the embodiment shown, second sheet 30 is slightly longer than the first sheet 28 such that the second sheet 30 extends beyond the first sheet 28 to form flap 34. A fastener (not shown) can be utilized to fasten the flap 34 to the first sheet 28. In an embodiment (FIG. 2), the first sheet 28 and the second sheet 30 are suitably joined together along edges thereof by the radiolucent seal 32. The seal 32 binds the first sheet 28 and the second sheet 30 in a variety of ways. In one embodiment, heat sealing is used. However, any means of sealing can be used is intended to be within the scope of the present disclosure. In another embodiment, the seal 32 is not radiolucent; however, this seal 32 does not interfere with the radiography. The seal 32 can be formed such that first sheet 28 and second sheet 30 have no discernable seams. Returning to FIG. 1, cover 26 can have a variety of shapes such as elliptical, oval, circular, triangular, square, rectangular or any other appropriate configuration. The cover 26 can be sized to enclose any cassette size. Accordingly, the cover 26 of the present disclosure includes dimensions ranging from about six to about sixteen inches for the length and to about eight inches to about twenty inches for the height and to about 1/16 inch to about six inches for the width. The dimensions are representative of an embodiment and not intended to limit the scope of the disclosure. Sheets 28, 30 include tops 38, 40, bottoms 42, 44, outer surfaces 46, 48 and inner surfaces 50, 52. The tops 38, 40 are separated from each other to form an opposing and open end of the cover 26. The bottoms 42, 44 are connected to each other to form an opposing and closed end of the cover 26. The inner surfaces 50, 52 form a sleeve 54 therein (FIG. 3). The sleeve 54 allows access space between the first sheet 28 and the second sheet 30 so as to insert the cassette 10 between the first sheet 28 and the second sheet 30. Thus, the cassette 10 fits into and resides between the first sheet 28 and the second sheet 30. The cover further comprises a band 56 operatively connected to the first sheet 28. The band 56 may be integratably attached to the first sheet 28. Alternatively (not shown), the band 56 may be removably attached to the first sheet 28. The band 56 includes an inner layer 58 and an outer layer 60. The band 56 may be in the form of a fold or a cuff. In an embodiment, the band 56 extends from the top 38 of sheet 28 and toward the bottom 42 of sheet 28. As will be discussed, the band 56 is movable around the top 38 of sheet 28 and toward other sheet 30. In a first position 62, the inner layer 58 of the band 56 is positioned adjacent to the outer surface 46 of sheet 28. In the first position 62, the band 56 is open to expose the sleeve 54. In a second position 64, the outer layer 60 of the band 56 is positioned adjacent to outer surface 50 of sheet 30. In the second position 62, the band 56 is closed to seal the sleeve 54 as will be discussed. In another embodiment (not shown), the band 56 is removably attachable to sheet 28. The cover 26 including sheets 28, 30, seals 32 and band 56 can be constructed of a variety of materials, such as, but not limited to, impermeable, radiolucent, hospital grade, sterile and non sterile materials. Hospital grade materials include materials namely low in generation of static electricity and substantially free of particulate matter, which could enter an incision. The material of the cover 26 is hospital grade for uses such as but not limited to: Intensive Care Unit and Critical Care Unit uses where the cassette 10 has to be placed properly; emergency room traumas, where excess fluids may contact the cassette 10; surgery in the sterile field of an operating room or for post-reduction X-ray of fractures where wet, messy plaster can be used. In one embodiment, the cover 26 comprises a fluid resistant, radiolucent material such that the cover 26 does not interfere with the radiograph procedure. In an embodiment, the cover 26 is constructed of a non-plastic material. The non-plastic material reduces adhesion of the patient's skin to the cover 26 during patient contact with the cover 26. In one embodiment, the cover 26 comprises a flame-resistant, polyester fabric. The sheets 28, 30 may include anti-microbiological materials dispersed throughout the sheets 28, 30. Further, the sheets 28, 30 may include ecological sensitive materials such as post-consumer, recycled polyester or low chemical emission materials. In another embodiment, the cover comprises another environmentally friendly material. In this embodiment, the cover may include a spunbond fabric which is bio-degradable to decompose within a short time frame such as a few months. Spunbond fabrics are patient friendly, easily slidable, pleasing to touch and easy to use. The spunbond fabric may comprise a spunbond or non woven polypropylene. The non woven fabric has properties such as: softness, anti-bacteria, fluid resistant, air permeability, fire resistant, high tensile strength, high elongation rate, no allergies to human bodies and economical to produce. In an embodiment (not shown), the sheets 28, 30 include an integrated cushion element dispersed throughout the sheets 28, 30. The cushion element is comprised of radiolucent material. In one embodiment, cushion element comprises a plurality of cushion elements. Any number of cushioned elements easily used for the intended purpose is acceptable. The cushioned element provides uniform padding for the entire cover 26. The cushion element is sized and shaped to accept and to cushion the patient's body part during the X-ray procedure. Since the sheets 28, 30 include the uniformly dispersed cushion elements, the hospital personnel can conveniently use any sheet 28, 30 of the cover 26 to support the patient's body part while placing the other sheet 28, 30 of the cover 26 on the appropriate support such as a gurney or operating table (FIG. 4). The uniformly dispersed cushion element maintains a symmetric configuration for the cover 26 to eliminate one side of the cover 26 being more bulky or thicker than the other side of the cover. The symmetric configuration of the cover 26 assists in storage, handling and disposal of the cover 26. In an embodiment (not shown), the cover 26 includes absorbent material to absorb fluid or blood of the patient. In this embodiment, the cover 26 absorbs the patient's fluid to assist in hygienic disposal of the cover 26 when the cover 26 becomes contaminated. During use, the health care professional conveniently grasps the cover 26 (which may be positioned within protective packaging) from storage and carries the cover 26 to a sterile field such as an operating room or sterile table. At the sterile field, the user removes the cover 26 from any protective packaging and opens the first sheet 28 and the second sheet 30 to expose the sleeve 54. Next the user inserts the X-ray cassette 10 into the sleeve 54 and between the first sheet 28 and the second sheet 30. The health care professional folds the flap 34 over the cassette 10 and into the sleeve 54. The flap 34 inserts within the sleeve 54 adjacent to the inner surface 50 of sheet 28. The inserted flap 34 may contact the top and front side of the cassette 10 and the inner surface 50 of sheet 28. In this position, the band 56 is in the first position 62 with the inner layer 58 of the band 56 positioned adjacent the outer surface 46 of sheet 28. The user then folds the band 56 over the inserted flap 34 and toward sheet 30. In folding the band 56 to the second position 64, the user rotates the band 56 so that the outer layer 60 of the band 56 is positioned adjacent and in contact with the outer surface 48 of sheet 30. The band 56 also folds around the seals 32 joining the sheets 28, 30. As shown in the second position 64, the cover 26 and its associated flap 34 and band 56 provide a convenient barrier between the patient, X-ray equipment and possible hospital acquired infections. The cover 26 isolates the X-ray cassette 10 for ever increasing requirements for infection control. The patient's body part is placed on the cover 26 to begin the X-ray procedure wherein the cover 26 and the enclosed X-ray cassette 10 support the patient's body part. The material of the cover 26 prevents adhesion of the patient's skin to the cover 26. After removal of the cassette 10 from the sleeve 54, the health care professional easily disposes of the cover 26 into the appropriate bio-hazard disposal or waste disposal. As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Moreover, the use of the terms “inner” and “outer” or “top” or “bottom” or “first or “second”” and variations of these terms is made for convenience, but does not require any particular orientation of the components.
	abstract	Disclosed is a decay heat removal system for cooling the decay heat of a reactor core and the spent fuel. The decay heat removal system including: a first heat pipe which is placed in an upper plenum of the reactor vessel and arranged in upward and downward directions corresponding to a position of an insertion hole formed on a top of the nuclear fuel assemblies; a control rod drive mechanism which is connected to an upper portion of the first heat pipe and drives the first heat pipe to move up and down so that the first heat pipe can be selectively inserted in a control rod insertion hole of the reactor core arranged in the nuclear reactor vessel; and a second heat pipe which is coupled to and in close contact with a bottom surface of the reactor vessel and removes the decay heat generated in the reactor core.
	description	The present description of the method of the invention is made in its application to the measurement of the lowering of a control cluster into a pressurized water nuclear reactor. The lowering channel is made up of guide tubes, a cluster guide, the heat sleeve, an adapter, the mechanism casing and the rod sheath. Step no 1 of the method of the invention is a measuring and recording step. It takes place at the time of start-up of the reactor, that is to say before use of the control rods. The equipment is assumed to be perfectly new and unused, with no opposing force that is not provided by the mechanism disturbing the functioning of the control cluster. This measurement is therefore a reference measurement. In this case a rod position indicator (RPI) is used. More exactly, it is used here to measure the instantaneous lowering velocity of the assembly in relation to time, that is to say V1=f1(t). Step no 2 is a calculation step on the basis of the measurement previously made under step 1. It consists of calculating distance of travel with integrated change in velocity of the object before the onset of friction, V1(t), for the purpose of obtaining the change in this velocity in relation to the distance of travel d of the mobile assembly: d 1 ⁢ ( t ) = ∫ u = 0 t ⁢ V ⁢ ( u ) ⁢ xe2x80x83 ⁢ ⅆ u From this equation the formula giving the velocity in relation to travel can be deduced: V1=g1(d). The two following steps consist of conducting steps no 1 and no 2 but after a certain operating time of the nuclear reactor, when undesired opposing friction forces occur which influence the time and lowering velocity of the mobile control rod assembly. Therefore, step no 3, using the rod position indicator RPI, consists of measuring and recording the deteriorated instantaneous velocity V2 in relation to time of the lowering of the mobile assembly. Step 4 then consists of calculating distance of travel with integrated velocity change of the mobile assembly using the measurement made of instantaneous velocity V2(t). The distance of travel can then be obtained, by integration: d 2 ⁢ ( t ) = ∫ u = 0 t ⁢ V 2 ⁢ u ⁢ ( xe2x80x83 ⁢ ⅆ u ) From this, the velocity of the mobile assembly can be deduced in relation to distance of travel after the onset of friction forces, that is to say: V2=g2(d) With step 5 it is possible to obtain the difference in lowering velocity of the mobile assembly before and after the onset of additional friction forces. All that is needed is to calculate the velocity difference V3=(V1xe2x88x92V2)=(g1xe2x88x92g2)(d)=g3(d) in relation to distance of travel d. To make this calculation, the reactor must be under the same operating conditions. Having regard to the fact that the behaviour of the measuring instrument is not fully controlled, in this case the rod position indicator RPI, since it is installed in a non-accessible containment where no human operation is possible, it was decided only to use this indicator after calculating the difference at step 5. It can indeed be considered that this measuring instrument may behave abnormally and give deformed measurement signals. Particular allusion is made here to data transmission problems which are relatively constant when the rod position indicator is installed. These problems are due in particular to pressure and temperature. On the other hand, it is considered that this deformation peculiar to this measuring instrument is always of the same order. Therefore, by only using the difference in measurements made before and after the onset of friction forces, any operating default of the RPI is overcome and only the variation in measurements made with this instrument is taken into account. Consequently, in accordance with step 6, the basic magnitude of the lowering velocity of the mobile assembly is calculated using a predetermined calculation code which takes into account known thermohydraulic, mechanical and dimensional conditions before the start-up of the nuclear reactor. Evidently this calculation code does not take into consideration friction forces occurring after start-up of the reactor, which cannot be predicted. This calculation code therefore gives the theoretical lowering velocity of the mobile assembly under non-deteriorated conditions. With the code it is therefore possible to obtain the change in theoretical velocity of the mobile assembly V4=g4(d). From this, the sum of normal forces is deduced: xe2x80x83Mxcex31=xcexa3normal forces Step 7 consists of taking into account the variations in velocity measured during the first steps and incorporating these in the result calculated during the previous step. This amounts to subtracting from the theoretical velocity, in relation to travel, the difference calculated using the measurements: V5=(g4xe2x88x92g3)(d)=g5(d). From this is deduced the sum of outside forces: Mxcex35=xcexa3normal forces+xcexa3additional friction forces Step 8, the last step, consists of deducing from the above the outside forces Foutside in relation to distance of travel f(d). For this purpose the fundamental equation of dynamics is used. Using the equation of the balance of forces: Mxcex34=xcexa3normal forces xcexa3normal forces=assembly-related forces, sheath related forces, guide related forces, other forces. Each force F is a function dependent upon velocity V, upon distance of travel d, upon system geometry, upon temperature xcex8 and other parameters, in which: M(xcex35xe2x88x92xcex34)=xcexa3additional friction forces The curves shown in FIGS. 2, 3 and 4 help to better understand the approach of the method according to the invention. In FIG. 2, time is shown along the X-axis while velocity and distance of travel are both on the Y-coordinate. If only a slight variation is observed between the two curves representing the reference distance of travel denoted d1 and deteriorated distance of travel d2, the variations in velocity are more significant. In respect of the latter, it is observed that the two measured velocities V1 and V2 are greater than the calculated velocity V4 and the velocity V5 obtained at the end of the method. Evidently, it is ascertained that the deteriorated velocity V2 is slower than the reference velocity V1. In addition, it is found that this difference between V1 and V2 is transferred to V4 and V5. Moreover, this velocity difference V3 between V1 and V2 appears in the graph in FIG. 3 in which the same remarks apply. In FIG. 4, which shows the change in friction forces (Y-axis) in relation to distance of travel (X-axis), only the two curves having the greatest variations are to be taken into consideration. This figure shows the results of the method of the invention, that is to say the additional friction forces calculated during the last step of the method of the invention, step 8, and these same additional friction forces when filtered. The two other curves concern measured forces.
046997598	summary	CROSS REFERENCE TO RELATED APPLICATIONS Reference is hereby made to the following copending applications dealing with related subject matter and assigned to the assignee of the present invention: 1. "Reconstituting A Nuclear Reactor Fuel Assembly" by Robert K. Gjersten et al, assigned U.S. Ser. No. 564,056 and filed Dec. 31, 1983 (W.E. 49,189). 2. "Nuclear Reactor Fuel Assembly With A Removable Top Nozzle" by John M. Shallenberger et al, assigned U.S. Ser. No. 644,758 and filed Aug. 27, 1984 (W.E. 51,311I) which is a continuation-in-part of U.S. Ser. No. 537,775, filed Sept. 30, 1983, now abandoned. 3. "Reusable Locking Tube In A Reconstitutable Fuel Assembly" by John M. Shallenberger et al, assigned U.S. Ser. No. 719,108 and filed Apr. 2, 1985 (W.E. 52,507). 4. "Guide Thimble Captured Locking Tube In A Reconstitutable Fuel Assembly" by Gary E. Paul, assigned U.S. Ser. No. 717,991 and filed Mar. 29, 1985 (W.E. 52,508). BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fuel assemblies for nuclear reactors and, more particularly, is concerned with a double lock joint for attaching the top nozzle of a fuel assembly to its guide thimbles in a manner which allows easy removal and replacement of the top nozzle. 2. Description of the Prior Art In most nuclear reactors, the reactor core is comprised of a large number of elongated fuel assemblies. Conventional designs of these fuel assemblies include a plurality of fuel rods and control rod guide thimbles held in an organized array by grids spaced along the fuel assembly length and attached to the control rod guide thimbles. Top and bottom nozzles on opposite ends of the fuel assembly are secured to the guide thimbles which extend slightly above and below the ends of the fuel rods. At the top end of the fuel assembly, the guide thimbles are attached in passageways provided in the adapter plate of the top nozzle. The guide thimbles may each include an upper sleeve for attachment to the top nozzle. During operation of such fuel assembly in a nuclear reactor, a few of the fuel rods may occasionally develop cracks along their lengths resulting primarily from internal stresses, thus establishing the possibility that fission products having radioactive characteristics may seep or otherwise pass into the primary coolant of the reactor. Such products may also be released into a flooded reactor cavity during refueling operations or into the coolant circulated through pools where the spent fuel assemblies are stored. Since the fuel rods are part of the integral assembly of guide thimbles welded to the top and bottom nozzle, it is difficult to detect and remove the failed rods. Until recently, to gain access to these rods it was necessary to remove the affected assembly from the nuclear reactor core and then break the welds which secure the nozzles to the guide thimbles. In so doing, the destructive action often renders the fuel assembly unfit for further use in the reactor because of the damage done to both guide thimbles and the nozzle which prohibits rewelding. In view of the high costs associated with replacing fuel assemblies, considerable interest has arisen in reconstitutable fuel assemblies in order to minimize operating and maintenance expenses. The general approach to making a fuel assembly reconstitutable is to provide it with a removable top nozzle. One early method of reconstituting the fuel assembly by removing and replacing its top nozzle is illustrated and described in the first patent application cross-referenced above. The top nozzle is removed by severing the guide thimbles just below where they are welded to the adapter plate of the top nozzle. Then, before the top nozzle is replaced just below where they are welded to the adapter plate of the top nozzle. Then, before the top nozzle is replaced back on the guide thimbles, annular grooves are formed in the passageways of the adapter plate. After the top nozzle is placed back on the guide thimbles with the latter inserted into the adapter plate passageways, circumferential portions of the upper ends of the guide thimbles are bulged into the passageway grooves so as to secure the top nozzles to the guide thimbles. An alternative approach to the above reconstitution method is illustrated and described in the second patent application cross-referenced above. An attaching structure for removably mounting the top nozzle on the upper ends of the guide thimbles is disclosed. The attaching structure includes a plurality of outer sockets defined in the adapter plate of the top nozzle, a plurality of inner sockets with each formed on the upper end of one of the guide thimbles, and a plurality of removable locking tubes inserted in the inner sockets to maintain them in locking engagement with the outer sockets. Each outer socket is in the form of a passageway through the adapter plate which has an annular groove formed therein. Each inner socket is in the form of a hollow upper end portion of the guide thimble having an annular bulge which seats in the annular groove when the guide thimble end portion is inserted in the adapter plate passageway. A plurality of elongated axial slots are provided in the guide thimble upper end portion to permit inward elastic collapse of the slotted portion so as to allow the larger bulge diameter to be inserted within and removed from the annular circumferential groove in the passageway of the adapter plate. In such manner, the inner socket of the guide thimble is inserted into and withdrawn from locking engagement with the outer socket. The locking tube is inserted from above the top nozzle into a locking position in the hollow upper end portion of the guide thimble forming the inner socket. When inserted in its locking position, the locking tube retains the bulge of the inner socket in its expanded locking engagement with the annular groove and prevents the inner socket from being moved to a compressed releasing position in which it could be withdrawn from the outer socket. In such manner, the locking tubes maintain the inner sockets in locking engagement with the outer sockets, and thereby the attachment of the top nozzle on the upper ends of the guide thimbles. Furthermore, to prevent inadvertent escape due to vibration forces and the like, heretofore the locking tubes have been secured in their locking positions. After insertion of the locking tubes into their locking positions within the inner sockets of the hollow upper end portions of the guide thimbles, a pair of bulges are formed in the upper portion of each locking tube. These bulges fit into the circumferential bulge in the upper end portion of the guide thimble and provide an interference fit therewith. Notwithstanding the overall acceptability of the above-described approaches, one disadvantage is that each requires the machining of annular grooves in the passageways of the top nozzle adapter plate. Consequently, a need remains for still another alternative approach to fuel assembly reconstitution which may further enhance commercial acceptance thereof. SUMMARY OF THE INVENTION The present invention provides a reconstitutable fuel assembly with improved features for locking the top nozzle upon and unlocking it from the guide thimbles which are designed to satisfy the aforementioned need. The present invention introduces a double lock joint concept which provides a tighter and stronger connection between the top nozzle and guide thimbles than heretofore. In particular, positive locking is provided at two elevations by axially spaced bulges on the guide thimbles which capture the top nozzle adapter plate therebetween. Excellent axial strength and resistance to transverse loading are built into the double lock joint. Furthermore, the design provides easy insertion and removal of the guide thimbles and locking tubes, eliminates the need for machining of internal annular grooves in the adapter plate passageways, and exhibits superior joint alignment and protection against joint slippage. Accordingly, the present invention sets forth in a reconstitutable fuel assembly including at least one guide thimble with an upper end portion having a central axis and a top nozzle with an adapter plate having top and bottom spaced apart surfaces and at least one passageway extending between the surfaces, a double lock joint structure for attaching the top nozzle adapter plate in releasable locking engagement upon the guide thimble upper end portion. The double lock joint structure comprises: (a) means defined in the upper end portion of the guide thimble to permit inward elastic collapse thereof to a compressed position upon application of forces directed radially inward toward the axis of the upper end portion and outward elastic return thereof to an expanded position upon removal of the radially inward directed forces; (b) upper means formed in the upper end portion of the guide thimble so as to provide the upper end portion at the location of the upper means with a diametric size greater than that of the adapter plate passageway when the guide thimble upper end portion is at its expanded position and a diametric size less than that of the adapter plate passageway when the upper end portion is collapsed to its compressed position upon application of the radially inward directed forces during insertion and withdrawal of the upper end portion into and from the adapter plate passageway; and (c) lower means formed in the upper end portion of the guide thimble so as to provide the upper end portion at the location of the lower means with a diametric size greater than that of the adapter plate passageway when the guide thimble upper end portion is at either one of its expanded and collapsed positions. The upper means is axially displaced from the lower means through a distance approximately equal to that between the top and bottom surfaces of the adapter plate such that after insertion of the upper end portion of the guide thimble through the adapter plate passageway the adapter plate is placed in a captured position between the upper and lower means. Also, the double lock joint structure includes a locking tube insertable into and removable from the upper end portion of the guide thimble between a locking position which maintains the upper end portion in the expanded position and the adapter plate in the captured position between the upper and lower means and an unlocking position which permits the upper end portion to inwardly collapse to the compressed position upon insertion and removal of the adapter plate onto and from the upper end portion. More particularly, the means defined in the upper end portion of the guide thimble to permit inward elastic collapse thereof to the compressed position is at least one axially extending slot formed in the upper end portion. Further, the upper and lower means each takes the form of bulges, preferably circumferentially, formed in the upper end portion of the guide thimble. Additionally, the locking tube includes upper and lower axially, and preferably circumferentially, displaced protuberances adapted to mate with the upper and lower annular bulges of the guide thimble upper end portion when the locking tube is inserted at its locking position therein and unmate from the upper and lower bulges when the locking tube is removed from the guide thimble upper end portion. Also, the locking tube includes a top annular flange located above the upper protuberance for facilitating insertion and removal of the tube into and from the guide thimble upper end portion. These and other advantages and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
	abstract	The invention comprises an apparatus and method of use thereof for using a single patient position during, optionally simultaneous, X-ray imaging and positively charged particle imaging, where imaging a tumor of a patient using X-rays and positively charged particles comprises the steps of: (1) generating an X-ray image using the X-rays directed from an X-ray source, through the patient, and to an X-ray detector, (2) generating a positively charged particle image: (a) using the positively charged particles directed from an exit nozzle, through the patient, through the X-ray detector, and to a scintillator, the scintillator emitting photons when struck by the positively charged particles and (b) generating the positively charged particle image of the tumor using a photon detector configured to detect the emitted photons, where the X-ray detector maintains a position between said the nozzle and the scintillator during the step of generating a positively charged particle image.
051006103	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) In a nuclear steam generator, it is important for safety reasons that the radioactive primary fluid remains separated from the non-radioactive secondary fluid so that the secondary fluid is not radioactively contaminated by the primary fluid. Therefore, it is important that the heat transfer tubes disposed in the steam generator remain leak-tight so that the radioactive primary fluid will not commingle with and contaminate the non-radioactive secondary fluid. Occasionally, such tubes become degraded and develop cracks. When a heat transfer tube is suspected of being degraded or of having throughwall cracks, a tube plug may be installed into the tube to prevent the primary fluid from commingling with the secondary fluid. However, the tube plug itself may become degraded and may develop cracks, especially in the upper interior region thereof. Therefore, it is desirable to inspect any tube plugs suspected of being degraded or cracked to determine whether they have in fact become degraded or cracked. Disclosed herein is a system for inspecting a tube plug to determine if the tube plug is degraded or has developed cracks, especially in the upper interior region thereof. Before describing the preferred embodiment of the present invention, it is instructive to first describe the structure and operation of a typical nuclear steam generator. Therefore, referring to FIG. 1, there is shown a nuclear steam generator, generally referred to as 10, for generating steam. Steam generator 10 comprises a vertically-oriented shell 20 defining a cavity 30 therein. Shell 20 has a dome-shaped upper shell portion 40, a frusto-conical transition portion 50 integrally attached to upper shell portion 40, a cylindrical hull portion 60 integrally attached to transition portion 50, and a bowl-shaped lower shell portion 70 integrally attached to hull portion 60. Formed through lower shell portion 70 are a plurality of manway openings 75 (only one of which is shown) for reasons provided hereinbelow. Of course, manway openings 75 are capable of being sealingly covered by suitable manway covers (not shown). Still referring to FIG. 1, disposed in cavity 30 are a plurality of vertically-oriented U-shaped steam generator tubes 80 for conducting radioactive primary fluid (e.g., water) therethrough, the plurality of tubes 80 defining a tube bundle 90. Each tube 80 has an inner wall 95 (see FIG. 2). Moreover, as shown in FIG. 1, each U-shaped tube 80 has a pair of vertical tube leg portions 100 interconnected by a U-bend tube portion 110 integrally formed therewith. In addition, each tube leg portion 100 has an open tube end 120 for passage of the primary fluid therethrough. Disposed in cavity 30 near lower shell portion 70 is a horizontal tube sheet 130 having a plurality of apertures 140 therethrough for receiving and for vertically supporting each tube end 120. Referring again to FIG. 1, disposed in lower shell portion 70 is a vertical divider plate 150 for dividing lower shell portion 70 into an inlet plenum chamber 160 and an outlet plenum chamber 170. Manway opening 75 allows for access to inlet plenum chamber 160 and outlet plenum chamber 170. Integrally attached to lower shell portion 70 is an inlet nozzle 180 and an outlet nozzle 190 in communication with inlet plenum chamber 160 and outlet plenum chamber 170, respectively. Disposed in cavity 30 above tube sheet 130 and interposed between shell 20 and tube bundle 90 is a cylindrical wrapper sheet 200 defining an annular downcomer region 210 between shell 20 and wrapper sheet 200. Wrapper sheet 200 is open at its bottom end and partially closed at its top end. That is, formed through the top end of wrapper sheet 200 are a plurality of holes (not shown) in its top end for passage of a steam-water mixture therethrough. Mounted atop wrapper sheet 200 is a moisture separator assembly, generally referred to as 220, for separating the steam-water mixture into liquid water and relatively dry saturated steam. Moisture separator assembly 220 also has holes (not shown) in the bottom portion thereof for receipt of the steam-water mixture from the interior of wrapper sheet 200 and holes (not shown) in the top portion thereof for passage of the dry saturated steam flowing upwardly from moisture separator assembly 220. In addition, integrally attached to the top of upper shell portion 40 is a main steam line nozzle 225 for passage of the dry saturated steam therethrough after the dry saturated steam passes upwardly from moisture separator assembly 220. As shown in FIG. 1, integrally attached to upper shell portion 40 is a feedwater nozzle 230 for passage of feedwater into a torodial feedring 240 which is in fluid communication with feedwater nozzle 230. Feedring 240 surrounds wrapper sheet 200 at the upper portion of wrapper sheet 200 and has a plurality of nozzles 250 attached thereto for passage of the feedwater from feedring 240, through nozzles 250 and downwardly into downcomer region 210. Disposed inwardly of wrapper sheet 200 are a plurality of horizontal spaced-apart tube support plates 260 (only four of which are shown) having holes 270 therethrough for receiving each tube 80 so that each tube 80 is laterally supported thereby. Each support plate 260 also has a plurality of orifices (not shown) therethrough for upward passage of the secondary fluid. During operation of steam generator 10, the primary fluid, which is heated by a nuclear reactor core (not shown), flows from the reactor core through inlet nozzle 180 and into inlet plenum chamber 160. The primary fluid then travels through one of the open tube ends 120, through tubes 80, out the other open tube end 120 and into outlet plenum chamber 170, whereupon the primary fluid exits steam generator 10 through outlet nozzle 190. As the primary fluid flows through tubes 80, feedwater simultaneously enters steam generator 10 through feedwater nozzle 230. The feedwater then enters feedring 240, flows through nozzles 250 and flows downwardly through downcomer region 210 until the feedwater impinges tube sheet 130. The feedwater then turns upwardly to surround tube bundle 90. As the primary fluid flows through tubes 80 it gives up its heat to the secondary feedwater fluid surrounding tube bundle 90. A portion of the secondary feedwater fluid surrounding tube bundle 90 is converted into a steam-water mixture that flows upwardly to moisture separator assembly 220 which separates the steam-water mixture into liquid water and relatively dry saturated steam. The liquid water returns downwardly to bundle 90 as the dry saturated steam travels upwardly to exit steam generator 10. The dry saturated steam exits steam generator 10 through main steam line nozzle 280 and is transported to a turbine-generator (not shown) for producing electricity in a manner well known in the art of nuclear-powered electricity production. Such a steam generator is disclosed in U.S. Pat. No. 4,079,701 entitled "Steam Generator Sludge Removal System" issued Mar. 21, 1978 to Robert A. Hickman et al., the disclosure of which is hereby incorporated by reference. Referring again to FIG. 1, there is illustrated the subject matter of the present invention, generally referred to as 290, which is a system for inspecting a tubularly-shaped member or tube plug for degradation or cracks. As described in more detail hereinbelow, inspection system 290 generally comprises probe means (e.g., a probe assembly 300) for extending an inspection probe sensor into the tube plug, hose means 310 connected to probe assembly 300 for transversely rotating and longitudinally translating the sensor probe, and drive means 320 connected to hose means 310 for operating hose means 310. Of course, it will be understood that before inspection system 290 is positioned to inspect the tube plug, the primary and secondary fluids are drained from steam generator 10 and a manway cover (not shown) is removed from manway opening 75 to allow access to inlet plenum chamber 160 and/or outlet plenum chamber 170. Turning now to FIGS. 2 and 3, the probe means, (e.g., probe assembly 300) is there shown in operative condition to inspect a tube plug 330 which is disposed in open end 120 of tube 80. Tube plug 330 may be made of "INCONEL" or the like for resisting stress corrosion cracking. Tube plug 330, which forms no part of the present invention, comprises a cylindrical shell 340 having a plurality of lands 345 extending therearound and integrally attached thereto for sealingly engaging inner wall 95 of tube 80. Shell 340 has a closed distal top end 350 and an open proximal bottom end 360. Moreover, shell 340 defines a chamber 370 therein that has a wall 375 gently tapering from closed distal top end 350 to near open proximal bottom end 360. Disposed in chamber 360 is a generally cylindrical externally tapered expander element 380 for expanding shell 340 into sealing engagement with inner wall 95 so that tube 80 is plugged thereby. Expander element 380 has a narrow threaded bore 385 longitudinally therethrough for reasons provided hereinbelow. Prior to expanding shell 340 into sealing engagement with inner wall 95, expander element 380 is disposed nearer to closed distal top end 350 than to open proximal bottom end 360. Therefore, in order to expand shell 340 into sealing engagement with inner wall 95, a threaded pull-rod tool (not shown) is caused to engage threaded bore 385 of expander element 380 to pull expander element 380 from near distal top end 350 to near proximal bottom end 360. As expander element 380 is drawn toward proximal bottom end 360 it engages tapering wall 375, thereby causing shell 340 to radially outwardly expand into sealing engagement with inner wall 95. Such a tube plug 330 is fully disclosed in U.S. Pat. No. 4,390,042 issued June 23, 1983 in the name of Harvey D. Kucherer et al. and entitled "Tube Plug", the disclosure of which is hereby incorporated by reference. Referring to FIGS. 2, 3, 4 and 5, probe assembly 300 comprises an elongated generally cylindrical probe carrier housing 390 having external threads 400 therearound and a longitudinal slot 405 therethrough near the distal end thereof. As described more fully hereinbelow, probe carrier housing 390 is sized to be inserted through the open proximal end 360 of tube plug 330 and through narrow bore 385 defined by expander element 380. It is important that probe carrier housing 390 be capable of extending through narrow bore 385. Probe carrier housing 390 should be capable of extending through narrow bore 385 so that the upper interior region of tube plug 330 between expander element 380 and distal top end 350 of tube plug 330 can be inspected. Probe carrier housing 390 has a sensor probe 410, such as a pancake-type eddy current coil, disposed therein for inspecting the portion of tube plug 330 between closed distal end 350 and expander element 380. A pancake-type eddy current coil suitable for use with the present invention is disclosed in U.S. patent application Ser. No. 079,860 filed July 30, 1987 in the name of Michael J. Metala and entitled "Apparatus and Method For Providing A Combined Ultrasonic And Eddy Current Inspection Of A Metallic Body", the disclosure of which is hereby incorporated by reference. Extending from sensor probe 410 is an electrically conductive wire 415 connected to sensor probe 410 at one end thereof and to a signal analyzer (not shown) at the other end thereof. The inspection signal is conducted through wire 415 to the analyzer where the inspection signal is analyzed to determine if tube plug 330 is degraded or cracked. Probe carrier housing 390 houses sensor probe 410 to protect probe 410 from damage in the manner disclosed hereinbelow and to assist in carrying sensor probe 410 into tube plug 330. As illustrated in FIGS. 2 and 3, probe assembly 300 further comprises limit means 420 connected to probe carrier housing 390 for delimiting the length of the interior of tube plug 330 to be inspected. Limit means 420 comprises a generally cylindrical extension member 430 surrounding probe carrier housing 390. Extension member 430 defines a passage 440 therethrough having internal threads (not shown) for threadably engaging external threads 400 of probe carrier housing 390. Moreover, passage 440 has an open end for passage of probe carrier housing 390 therethrough. As best seen in FIGS. 3, 4, and 5, a first collar 450 surrounds extension member 430 and has a bore 460 centrally therethrough for slidably receiving extension member 430. First collar 450 has a circular depending shoulder 465 extending around extension member 430, shoulder 465 being sized to abut against open proximal bottom end 360 of tube plug 330. A second collar 470 is spaced apart from first collar 450 and also surrounds extension member 430. Second collar 470 has a step bore 472 therethrough sized to seat the proximal end of extension member 372 in the larger diameter of step bore 472. Moreover, second collar 470 defines a first opening 480 and a second opening 490 for reasons to be described presently. A first guide 500 has a distal end portion 510 thereof anchored in first collar 450 and also has a proximal end portion 520 thereof slidably received in first opening 480 which is formed through second collar 470. A second guide 530 has a distal end portion 540 thereof anchored in first collar 450 and also has a proximal end portion 550 thereof slidably received in second opening 490 which is formed through second collar 470. Second guide 530 has a bore 535 therethrough and an elongated indicator pin 537 extending slidably through bore 535 for reasons disclosed hereinbelow. Moreover, surrounding extension member 430 and adjustably connected thereto is a plate assembly generally referred to as 560. Plate assembly 560 is spaced-apart by a predetermined distance from second collar 470. Plate assembly 560 may comprise a pair of horizontally disposed spaced apart disk-shaped plates 562 and 564. Interposed between plates 562 and 564 is a thrust bearing 566. Surrounding extension member 430 and mounted atop plate 562 is an 0-shaped ring member 568 for maintaining plate 562 pressed against thrust bearing 566. Moreover, interposed between first collar 450 and second collar 470 is a resilient spring member 569 for biasing first collar 450 upwardly so that first collar 450 and second collar 470 are maintained in a variable spacedapart relationship and so that shoulder 465 is biased into abutment against open end 360 of tube plug 330. Still referring to FIGS. 3, 4 and 5, connected to second collar 470 by a plurality of screws 570 is a generally cylindrical casing 580 extending around plate assembly 560 for housing plate assembly 560. Casing 580 has an open distal end which is covered by second collar 470 and an open proximal end which is covered by a closure member 590. Closure member 590 is attached to casing 580 such as by one or more screws 600. Moreover, closure member 590 has a bore 610 therethrough which may be a step bore. Closure member 590 also has an extended portion 620 (which includes bore 610) integrally formed therewith for receiving a connection member 630 which is removably attached to extended portion 620. Connection member 630 is capable of being connected to a positioning device (not shown) for suitably coaxially aligning probe assembly 300 beneath tube plug 330 and for maintaining probe assembly 300 in abutment with tube plug 330 as tube plug 330 is inspected by inspection system 290. The positioning device may be a remotely operated robotic device such as an SM-10W robot available from Westinghouse Electric Corporation located in Pittsburgh, Pa. Second collar 470, casing 390, and closure member 590 together define a cavity 635 within probe assembly 300, in which cavity 635 plate assembly 560 is slidably disposed and housed. Referring yet again to FIGS. 3, 4 and 5, a generally cylindrical rotator 640, slidably disposed in bore 610, is attached to extension member 430 such as by a set screw 650 and extends from bore 610 to abut against plate 564. Rotator 640 has a step bore 660 therethrough defining a ledge 665 in step bore 660 for reasons provided hereinbelow. For reasons disclosed hereinbelow, disposed in bore 660 is a generally cylindrical actuator 670 having a central bore 675 therethrough. Also disposed in bore 660 and interposed between ledge 665 and actuator 670 is a compression spring 680 for upwardly biasing actuator 670. Rotator 640 also has an elongated portion 642 for reasons disclosed hereinbelow. As best seen in FIG. 5, a resilient elongated leaf spring 690 is attached, such as by a screw 695, to actuator 670. Leaf spring 690 extends from actuator 670 to adjacent slot 405 formed through probe carrier housing 390. A top end portion 697 of leaf spring 690 is formed into a bent or angled leg 700 having a cam surface 710 thereon. Transversely extending through the upper portion of probe carrier housing 390 is a generally cylindrical or rod-like cam 730 for slidably engaging cam surface 710. It will be understood that as leaf spring 690 is caused to retreat downwardly in the manner described hereinbelow, cam surface 710 will slidably engage cam 730 for radially extending sensor probe 410 through slot 405 to inspect wall 375 of tube plug 330. Similarly, as leaf spring 690 is caused to advance upwardly in the manner described hereinbelow, cam surface 710 will slidably disengage cam 730 for radially retracting sensor probe 410 through slot 405 and into probe carrier housing 390 to protect sensor probe 410 from damage. Turning now to FIGS. 4, 6, 7 and 8, hose means 310 is connected to the probe means 300. Hose means 310 comprises a flexible conduit 740 connected to extended portion 620 by a removable clamp 745. Hose means 310 further comprises a hollow, segmented and flexible hose 750 connected to rotator 640 and disposed through conduit 740 for rotating rotator 640 which in turn rotates probe carrier housing 390. Hose 750 comprises a plurality of segments 760 for flexibility. Interposed between adjacent segments 760 of hose 750 is a connector 770 for maintaining tension in hose 750 so that hose 750 remains tangle-free as hose 750 is rotated in the manner described hereinbelow. Each connector 770 comprises an elongated generally cylindrical body 780 for receiving the opposing ends of adjacent segments 760 thereon. Each connector 770 further comprises an enlarged portion 790 near the middle portion of body 780. Enlarged portion 790 has a recess 800 formed therein for matingly receiving a spherical bearing 810 which slides or rolls on the inner surface of conduit 740 as hose 750 is rotated and translated in conduit 740. As best seen in FIG. 9, there is shown adaptor means, generally referred to as adaptor assembly 815, for connecting hose means 310 to drive means 320. Adaptor assembly 815 comprises a generally cylindrical barrel 820 having a bore 825 therethrough for receiving conduit 740. Conduit 740 is attached to adaptor assembly 815 in bore 825, such as by a press fit. Barrel 820 also has a flange 830 extending around its proximal end 835 for reasons disclosed hereinbelow. Extending into bore 825 and attached to hose 750 is an elongated generally cylindrical tube nozzle 840 which has a bore 850 therethrough. Tube nozzle 840 terminates in a flange 845 for reasons provided hereinbelow. Attached to tube nozzle 840 is an elongated generally cylindrical slide tube 860 having a circular flange 865 surrounding the distal end thereof, a longitudinal groove 867 therein, and a bore 868 longitudinally therethrough. Flange 865 has a pair of holes 866 transversely therethrough for reasons disclosed hereinbelow. Moreover, slide tube 860 defines a stop 870 at the bottom of qrove 867 for stopping the longitudinal travel of a dowel pin 869. Extending through flange 845 and flange 865 are a plurality of screws 872 for attaching slide tube 860 to tube nozzle 840. Slidably disposed in bore 868 is an elongated cylindrical slide 880 having a bore 885 therethrough, which bore 885 defines a ledge 890 in slide 880. Slide 880 also has a dowel pin 869 attached transversely thereto and sized to slide longitudinally in groove 867. Still referring to FIG. 9, an elongated flexible cable 900 extends from near ledge 890 through bore 850, through hose 760 to actuator 670. An end of cable 900 is suitably connected to actuator 670, such as by a bolt 902 (see FIG. 5). As shown in FIG. 9, the other end of cable 900 is anchored in a cable holder 910 by a plurality of set screws 920. Formed in the bottom portion of slide 880 is a recessed slot 930 for reasons disclosed hereinbelow. FIGS. 10, 11, 12, 13 and 14 illustrate drive means 320, such as a probe driver assembly 940, which is capable of receiving adaptor assembly 815. Probe driver assembly 940 comprises a frame 950 having a hole 960 therethrough sized to receive a suitable hoisting tool (not shown) for transporting or carrying probe driver assembly 940. Attached to frame 950 is a flat rectangularly-shaped guide rail 970 having a groove 980 extending along the vertical marginal edges thereof. In the preferred embodiment of the invention, frame 950 has two guide rails 970. Each guide rail 970 is attached to frame 950, such as by a plurality of screws 985. Probe driver assembly 940 further comprises a platform 990 that has a flange 1000 (see FIG. 13) for slidably engaging groove 980 formed in each guide rail 970. As shown in FIGS. 10, 11, 12 and 13, attached to platform 990 is a top shelf 1010 having an aperture 1015 for receiving slide 880 therethrough. Moreover, attached to platform 990 is a bottom shelf 1020 also having an aperture for receiving slide 880 therethrough. Also formed through bottom shelf 1020 is a bore 1025 for reasons described hereinbelow. Connected to top shelf 1010 is a pneumatic cylinder 1012 for raising and lowering (i.e., vertically translating) top shelf 1010 and bottom shelf 1020. Bottom shelf 1020 is spaced-apart from top shelf 1010 for receiving a first pulley 1030 and a hollow second pulley 1040 therebetween. Top shelf 1010 and bottom shelf 1020 are connected by a bolt 1035 attached to shelves 1010 and 1020 so that bottom shelf 1020 moves as top shelf 1010 moves. Second pulley 1040 has an uppermost circumferential flange 1042 integrally attached thereto for reasons provided hereinbelow. The upper portion of second pulley 1040 is received through aperture 1015 and the bottom portion of second pulley is received in a step bore 1041 formed through bottom shelf 1020 (see FIG. 15). As seen in FIGS. 10, 11, 12 and 13, first pulley 1030 and second pulley 1040 are each rotatably connected to top shelf 1010 and to bottom shelf 1020. Extending through bore 1025 is a motor shaft 1050 for rotating first pulley 1030. Motor shaft 1050 is attached to first pulley 1030 at one end of motor shaft 1050 and rotatably connected to a variable speed reversible electric motor 1055 at the other end of motor shaft 1050. It will be appreciated that motor 1055 may alternatively be an air operated motor. Extending around first pulley 1030 and second pulley 1040 is a pulley belt 1060 for rotating second pulley 1040 as first pulley 1030 is rotated by motor 1055. Still referring to FIGS. 10, 11, 12, 13 and 14, attached to bottom shelf 1020 is a pneumatic cylinder assembly, generally referred to as 1070, having pistons 1080 actuable by a plurality of pneumatic cylinders 1090. A brace 1100 is attached to pistons 1080 so that brace 1100 can be raised and lowered by pistons 1080. Brace 1100 has a slot 1110 therethrough for receiving a slide holder 1120 that has an arch-shaped opening 1122 (see FIG. 16) defining a pair of tines 1124 (see FIG. 16) for matingly slidably engaging slot 930 formed in slide 880. Thus, slide holder 1120 is capable of being slidably outwardly moved to disengage slot 930 and slidably inwardly moved to engage slot 930, as shown by the straight arrows in FIGS. 11, 12, 13 and 16. Referring yet again to FIGS. 10, 11, 12, 13 and 14, spaced above first shelf 1010 and attached to fame 950 is an uppermost shelf 1170 having a step bore 1180 therethrough. Step bore 1180 is sized to matingly receive flange 830 of adaptor assembly 815 in the larger portion thereof and also sized to receive tube nozzle 840 therethrough. Moreover, attached to the top of top shelf 1010 is a pivotable first locking member 1190 for locking slide tube 860 rotatably in place. First locking member 1190 pivots about bolt 1200 and has a semi-circular hole therethrough for matingly receiving flange 865 of slide tube 860. In addition attached to the top of uppermost shelf 1170 is a pivotable second locking member 1210 for locking barrel 820 (of adaptor assembly 815) in place so that barrel 820 will not vertically move during operation of probe driver assembly 940. Second locking member 1210 pivots about bolt 1215 and has a semi-circular hole 1220 therethrough for matingly receiving barrel 820. Second locking member 1210 is pivotable about bolt 1215 in the direction shown by the curved arrow in FIG. 13. Referring to FIGS. 10, 11, 12, 13 and 14, a plurality of flexible air tubes 1230 are connected to an air nozzle 1240 at one end thereof and connected to pneumatic cylinders 1012 and 1090 at the other end thereof. Air nozzle 1240 is in turn connected to an air supply source (not shown) for supplying compressed air to air nozzle 1240 and thus to air tubes 1230. Attached to frame 950 and to air tubes 1230 is a solenoid valve assembly 1250 for selectively controlling the flow of air through air tubes 1230. As best seen in FIGS. 14 and 15, adaptor assembly 815 is connected to drive means 320. When adaptor assembly 815 is connected to drive means 320, flange 830 is received in step bore 1180 of uppermost shelf 1170. Slide tube 860, which also belongs to adaptor assembly 815, is received through hollow second pulley 1040 such that flange 865 of slide tube 860 is mounted on the top surface of second pulley 1040. When flange 865 is mounted on second pulley 1040, ridges 1160, which are integrally attached to second pulley 1040, are matingly received through holes 866 formed in flange 865, which belongs to slide tube 860. Thus, it will be understood that as second pulley 1040 rotates, slide tube 860 will also rotate because ridges 1160 connect slide tube 860 to second pulley 1040. FIG. 16 illustrates brace 1100 having slot 1110 for receiving slide holder 1120. Slide holder 1120 may be selectively moved in the direction of the straight arrow shown in FIG. 16 such that tines 1124 engage or disengage slot 930 formed in slide 880, as disclosed hereinabove. METHOD OF OPERATION During operation of inspection system 290, steam generator 10 is taken out of service and the primary and secondary fluids are drained in the customary manner well known in the art. Next, the manway covers (not shown) covering manway opening 75 are removed. One end of hose means 310 is connected to probe assembly 300 by pushing one end of hose 750 onto elongated portion 642 of rotator 640. The other end of hose 750 is attached to tube nozzle 840 which belongs to adaptor assembly 815. A remotely operated robotic device (not shown), such as an SM-10W robotic arm, is connected to probe assembly 300 by connecting the robotic device to connection member 630. The operator of the robotic device causes the robotic device to be inserted through manway opening 75 and operates the robotic device to align probe assembly 300 coaxially beneath the tube plug 330 which is to be inspected. Frame 950 is transported to near steam generator 10 by engaging a suitable hoisting tool (not shown) into hole 960 belonging to frame 950 and carrying or transporting probe driver 940 to a low-radiation area in the vicinity of steam generator 10. The hoisting tool may then be disengaged from hole 960. Adaptor assembly 815 is connected to probe driver 940 in the manner disclosed immediately hereinbelow. Adaptor assembly 815 is removably connected to probe driver 940 such that flange 830 belonging to end 835 of barrel 820 is matingly received in step bore 1180 (see FIG. 15). As flange 830 is received in step bore 1180, slide 880 will be received through hollow second pulley 1040 and ridges 1160 will be matingly received through holes 866 of slide 880. Adaptor assembly 815 is then locked to probe driver 320 in the manner described immediately hereinbelow to secure adaptor assembly 300 to probe driver 940. In this regard, first locking member 1190 is pivoted about bolt 1200 such that flange 865 of slide tube 860 is matingly received in the semi-circular hole formed through first locking member 1190. Second locking member 1210 is pivoted about bolt 1215 (in the direction shown by the curved arrow in FIG. 14) such that end 835 of barrel 820 is matingly received through the semi-circular hole formed through second locking member 1190. Slide holder 1120 is slidably horizontally translated in slot 1110 (in the direction of the straight arrows shown in FIGS. 11, 12, 13 and 16), which slot 1110 is formed in brace 1100. Slide holder 1120 is horizontally translated such that tines 1124 belonging to slide holder 1120 slidably engage slot 930 formed in slide 880. An end of conduit 740, which houses hose 750, is pushed over extended portion 620 of closure member 590, which belongs to probe assembly 300. Conduit 740 is then removably connected to extended portion 620 by clamp 745. Thus, it will be understood that probe assembly 300 is connected to hose means 310, which is in turn connected to adaptor assembly 815. Adaptor assembly 815 itself is connected to drive means 320. Thus, it will be appreciated that inspection system 290 generally comprises probe assembly 300, hose means 310, adaptor assembly 815 and drive means 320. The robotic device is operated to translate probe assembly 300 upwardly such that shoulder 465 of first collar 450 abuts proximal bottom end 360 of tube plug 330. Spring member 569, which extends around the lower portion of extension member 430, compresses and allows first collar 450 to move controllably axially downwardly as a downward reactive force is exerted by proximal bottom end 360 of tube plug 330. As the robotic device continues to upwardly translate probe assembly 300, the proximal bottom end 360 of tube plug 330 exerts a reactive force against shoulder 465, which belongs to first collar 450. This reactive force against first collar 450 causes first guide 500 and second guide 530 to slide downwardly through first opening 480 and second opening 490, respectively. The robotic device will continue to translate probe assembly 300 upwardly until the top end of extension member 430 abuts the bottom of expander element 380, which is disposed in tube plug 330. In this regard, as first guide 500 and second guide 530 slide downwardly, the distance between the proximal end of indicator pin 537 and plate 562 decreases until extension member 430 abuts expander element 380. The remaining distance between plate 562 and the proximal end of indicator pin 537 equals the length of the interior of tube plug 330 to be inspected. Drive means 320 is then operated in the manner disclosed hereinbelow to upwardly advance plate assembly 560 to close this remaining distance between plate 562 and the proximal end of indicator pin 537. As plate assembly 560 advances upwardly, plate 562, which belongs to plate assembly 560, will abut the proximal end of indicator pin 537 which is slidably disposed through bore 535 of second guide 530. As plate 562 abuts the proximal end of indicator pin 537 and continues to translate vertically upwardly, the distal end of indicator pin 537 will also vertically upwardly translate. Vertical movement of the distal end of indicator pin 537 indicates that the inspection process is complete because, as disclosed hereinabove, the distance between the proximal end of indicator pin 537 and plate 562 equals the length of the interior of tube plug 330 to be inspected. As more fully described hereinbelow, operation of motor 1055 upwardly advances plate assembly 560. In this regard, motor 1055 is operated to rotate motor shaft 1050 which in turn rotates first pulley 1030 because motor shaft 1050 is attached to first pulley 1030. As first pulley 1030 rotates, pulley belt 1060 rotates. As pulley belt 1060 rotates, second pulley 1040 also rotates because pulley belt 1060 wraps around both first pulley 1030 and second pulley 1040. Slide 880 rotates as second pulley 1040 rotates because ridges 1160, belonging to second pulley 1040, connect second pulley 1040 to flange 865 which is integrally attached to slide 880. Moreover, as slide 880 rotates, tube nozzle 840 also rotates because tube nozzle 840 is attached to flange 865 by screws 872. As tube nozzle 840 rotates, segmented hose 750 also rotates because an end of hose 750 is attached to tube nozzle 840 (see FIG. 15). As disclosed hereinbelow, rotation of segmented hose 750 causes segmented hose 750 to travel along the interior of conduit 740. Connector 770, which is interposed between adjacent segments 760 of segmented hose 750, has a plurality of bearings 810 for allowing hose 750 to rotatably slidably travel along the interior of conduit 740. As hose 750 rotates, rotator 640 rotates because hose 750 is connected to elongated portion 642 of rotator 640. Rotation of rotator 640 will cause probe carrier housing 390 to rotate because rotator 640 is attached to probe carrier housing 390 by set screw 650. As described hereinabove, the external threads 400 of probe carrier housing 390 threadably engage the internal threads (not shown) of extension member 430. Therefore, as probe carrier housing 390 is rotated by rotator 640, probe carrier housing 390 will vertically threadably advance in extension member 430 as external threads 400 threadably engage the internal threads of extension member 430. Thus, it will be appreciated that the advancement of hose 750 through conduit 740 also advances probe carrier housing 390 through extension member 430. Air nozzle 1240 supplies compressed air to pneumatic cylinder 1012 for raising and lowering bottom shelf 1020. Of course, it will be understood that, as bottom shelf 1020 is raised and lowered (i.e., vertically translated), top shelf 1010 is similarly raised and lowered a like distance because bottom shelf 1020 is attached to top shelf 1010 by bolt 1035. As top shelf 1010 and bottom shelf 1020 are thusly translated, platforms 990 are similarly translated because top shelf 1010 and bottom shelf 1020 are attached to platforms 990. As platforms 990 are translated, flange 100, belonging to each platform 990, will matingly slide in grooves 980 formed in each platform 990 so that shelves 1010 and 1020 smoothly slidably move in the vertical direction (i.e., either upwardly or downwardly). The air flow to pneumatic cylinder assembly 1070 and to pneumatic cylinder 1012 is selectively controlled by solenoid valve assembly 1250 in a manner well known in the art. Hence, top shelf 1010, bottom shelf 1020 and brace 1100 are vertically adjustable to receive adaptor assembly 815 and to actuate leaf spring 690. As probe carrier housing 390 continues to advance in the manner disclosed hereinabove, slot 405 in probe carrier housing 390 will eventually clear extension member 330 and then also clear expander element 380 so that sensor probe 410 can be extended through slot 405 to inspect the upper interior region of tube plug 330. Of course, as probe carrier housing 390 threadably longitudinally translates into tube plug 330, it also transversely rotates in the manner described hereinabove allowing sensor probe 410 to provide a helical inspection scan of tube plug 330 between distal top end 350 and expander element 380. In the manner described hereinbelow, sensor probe 410 is capable of being extended through slot 405 to inspect tube plug 330. Compressed gas, such as compressed air or the like, is supplied to air nozzle 1240. Air nozzle 1240 supplies the compressed air to air tubes 1230 which conduct the air to pneumatic cylinders 1090 that belong to pneumatic cylinder assembly 1070 which raises and lowers brace 1100. Moving brace 1100 downwardly causes slide 880 to move downwardly a like extent because tines 1124 belonging to brace 1100 engage slot 930 belonging to slide 880. Moving slide 880 downwardly causes cable 900 to move downwardly a like extent because cable 900 is attached to slide 880 at cable holder 910. Moving cable 900 downwardly causes actuator 670 to move slidably downwardly a like extent because cable 900 is attached to actuator 670 by bolt 902. Moving actuator 670 downwardly causes leaf spring 690 to move downwardly because leaf spring 690 is attached to actuator 670 by screw 695. Moving leaf spring 690 downwardly causes cam surface 710, Which belongs to leaf spring 690, to slidably engage cam 730. As cam surface 710 slidably engages cam 730, bent leg portion 700 flexes or deflects causing top end portion 697, which has sensor probe 410 attached thereto, to extend radially outwardly toward wall 375 of tube plug 330 for inspecting tube plug 330. After tube plug 330 is inspected, inspection system 290 is withdrawn from tube plug 330 in a manner substantially the reverse of its insertion into tube plug 330. After tube plug 330 is inspected, inspection system 290 is relocated to inspect another tube plug 330, if desired. After the desired number of tube plugs are inspected, inspection system 290 is removed from steam generator 10 substantially in reverse order of its insertion into steam generator 10. The manway covers (not shown) are replaced over manway openings 75 and steam generator 10 may then be returned to service. Although the invention is fully illustrated and described herein, it is not intended that the invention as illustrated and described be limited to the details shown, because various modifications may be obtained with respect to the invention without departing from the spirit of the invention or the scope of equivalents thereof. For example, a modification of the present invention would be to eliminate the extension member for suitably inspecting tube plugs not having expander members therein. A further modification of the present invention would be to connect a suitable video camera assembly to probe assembly 300 for viewing the tube plug inspection process. Although the invention was conceived during an investigation directed towards improving techniques used for examining the interiors of tube plugs and was therefore described in connection with such use, it will be appreciated that the invention may have other uses, such as for examining the interiors of any tubular member or other type of conduit. Therefore, what is provided is a system for inspecting a tube plug having an expander member disposed therein, wherein the system is capable of inspecting the upper region of the tube plug between the top of the tube plug and the top of the expander member to determine if the upper region of the tube plug is degraded or cracked.
	abstract	Disclosed is a radiation protection screen for protecting an operator from ionizing radiation, which screen includes a front partition structure that is made of one or more radiation protection materials and a side partition structure that is made of one or more radiation protection materials, the partitions being joined together at a vertical or substantially vertical corner border, and which screen includes feet that are equipped with wheels that rest on the ground. Furthermore, according to the invention, this screen is arranged such that the front partition structure includes a lower portion and an upper portion that may be moved with respect to each other, the upper portion of the front partition structure being mounted so as to be able to pivot in the region of the corner border, about a vertical or substantially vertical pivoting axis.
042736161	claims	1. In a nuclear fuel rod having a column of vertically aligned, hollow fuel pellets contained within an encapsulating cladding such that a central passage is formed along the length of the column, the improvement comprising: a spacer plug having a solid cross section at least as large as the passage, the plug being interposed between proximate fuel pellets at selected locations along the column, whereby any fuel pellet debris falling through the passage is trapped by the next lower spacer rather than accumulating at the bottom of the column. 2. The improved fuel rod recited in claim 1 wherein the plug has a horizontal thickness substantially equal to that of the fuel pellets. 3. The improved fuel rod recited in claim 1 wherein the spacer plug consists of a block of graphite. 4. The improved fuel rod recited in claim 1 wherein the spacer plug consists of a solid block of nuclear fuel material. 5. The improved fuel rod recited in claim 3 wherein the plug has a lower effective fissile enrichment than the fuel pellets.
	description	This application claims the benefit of U.S. Provisional Application No. 61/624,693 filed Apr. 16, 2012 and titled “REACTOR COOLANT PUMP SYSTEM INCLUDING TURBO PUMPS POWERED BY A MANIFOLD PLENUM CHAMBER”. U.S. Provisional Application No. 61/624,693 filed Apr. 16, 2012 and titled “REACTOR COOLANT PUMP SYSTEM INCLUDING TURBO PUMPS POWERED BY A MANIFOLD PLENUM CHAMBER” is hereby incorporated by reference in its entirety into the specification of this application. This application claims the benefit of U.S. Provisional Application No. 61/624,966 filed Apr. 16, 2012 and titled “COOLANT PUMP APPARATUSES AND METHODS OF USE FOR SMRS”. U.S. Provisional Application No. 61/624,966 filed Apr. 16, 2012 and titled “COOLANT PUMP APPARATUSES AND METHODS OF USE FOR SMRS” is hereby incorporated by reference in its entirety into the specification of this application. The following relates to the nuclear reactor arts, nuclear power generation arts, nuclear reactor hydrodynamic design arts, and related arts. In nuclear reactor designs of the pressurized water reactor (PWR) type, a radioactive nuclear reactor core is immersed in primary coolant water at or near the bottom of a pressure vessel. The primary coolant is maintained in a compressed or subcooled liquid phase. In applications in which steam generation is desired, the primary coolant water is flowed out of the pressure vessel, into an external steam generator where it heats secondary coolant water flowing in a separate secondary coolant path, and back into the pressure vessel. Alternatively an internal steam generator is located inside the pressure vessel (sometimes called an “integral PWR” design), and the secondary coolant is flowed into the pressure vessel within a separate secondary coolant path in the internal steam generator. In either design, heated primary coolant water heats secondary coolant water in the steam generator to convert the secondary coolant water into steam. An advantage of the PWR design is that the steam comprises secondary coolant water that is not exposed to the radioactive reactor core. In a typical PWR design configuration, the primary coolant flow circuit is defined by a cylindrical pressure vessel that is mounted generally upright (that is, with its cylinder axis oriented vertically). A hollow cylindrical central riser is disposed concentrically inside the pressure vessel. Primary coolant flows upward through the reactor core where it is heated and rises through the central riser, discharges from the top of the central riser and reverses direction to flow downward back toward the reactor core through a downcomer annulus defined between the pressure vessel and the central riser. This is a natural convection flow circuit that can, in principle, be driven by heat injection from the reactor core and cooling of the primary coolant as it flows upward and away from the reactor core. However, for higher power reactors it is advantageous or even necessary to supplement or supplant the natural convection with motive force provided by electromechanical reactor coolant pumps. Most commercial PWR systems employ external steam generators. In such systems, the primary coolant water is pumped by an external pump connected with external piping running between the PWR pressure vessel and the external steam generator. This also provides motive force for circulating the primary coolant water within the pressure vessel, since the pumps drive the entire primary coolant flow circuit including the portion within the pressure vessel. Fewer commercial “integral” PWR systems employing an internal steam generator have been produced. One contemplated approach is to adapt a reactor coolant pump of the type used in a boiling water reactor (BWR) for use in the integral PWR. Such arrangements have the advantages of good heat management (because the pump motor is located externally) and maintenance convenience (because the externally located pump is readily removed for repair or replacement). However, the coupling of the external reactor coolant pump with the interior of the pressure vessel introduces vessel penetrations that, at least potentially, can be the location of a loss of coolant accident (LOCA). Another disadvantage of existing reactor coolant pumps is that the pump operates in an inefficient fashion. Effective primary coolant circulation in a PWR calls for a pump providing high flow volume with a relatively low pressure head (i.e., pressure difference between pump inlet and outlet). In contrast, most reactor coolant pumps operate most efficiently at a substantially higher pressure head than that existing in the primary coolant flow circuit, and provide an undesirably low pumped flow volume. Yet another disadvantage of existing reactor coolant pumps is that natural primary coolant circulation is disrupted as the primary coolant path is diverted to the external reactor coolant pumps. This can be problematic for emergency core cooling systems (ECCS) that rely upon natural circulation of the primary coolant to provide passive core cooling in the event of a failure of the reactor coolant pumps. Another contemplated approach is to employ self-contained internal reactor coolant pumps in which the pump motor is located with the impeller inside the pressure vessel. However, in this arrangement the pump motors must be designed to operate inside the pressure vessel, which is a difficult high temperature and possibly caustic environment (e.g., the primary coolant may include dissolved boric acid). Electrical penetrations into the pressure vessel are introduced in order to operate the internal pumps. Pump maintenance is complicated by the internal placement of the pumps, and maintenance concerns are amplified by an anticipated increase in pump motor failure rates due to the difficult environment inside the pressure vessel. Still further, the internal pumps occupy valuable space inside the pressure vessel. Disclosed herein are improvements that provide various benefits that will become apparent to the skilled artisan upon reading the following. In one aspect of the disclosure, a nuclear reactor includes a nuclear core comprising a fissile material, and a pressure vessel containing the nuclear core immersed in primary coolant water. Turbo pumps disposed in the pressure vessel provide active circulation of primary coolant water in the pressure vessel. Each turbo pump includes a turbine driving an impeller. A manifold plenum chamber is disposed in the pressure vessel, and is in fluid communication with inlets of the turbines of the turbo pumps. An electrically driven pump operatively connected with the manifold plenum chamber to pressurize the manifold plenum chamber with primary coolant water. The turbo pumps may be disposed in openings passing through the manifold plenum chamber. The pressure vessel may be vertically oriented and cylindrical, with a cylindrical riser oriented coaxially inside, and the manifold plenum chamber may be annular and disposed in a downcomer annulus defined between the cylindrical riser and the cylindrical pressure vessel. In another aspect of the disclosure, an apparatus comprises: a nuclear core comprising a fissile material; a pressure vessel containing the nuclear core immersed in primary coolant water; and a reactor coolant pump (RCP) assembly including a manifold plenum chamber disposed in the pressure vessel and containing pressurized primary coolant water at a pressure higher than the pressure of primary coolant water in the pressure vessel, and a plurality of turbo pumps disposed in the pressure vessel. Each turbo pump includes an impeller arranged to pump primary coolant water in the pressure vessel and a turbine in operative fluid communication with the manifold plenum chamber so as to be driven by pressurized primary coolant water in the manifold plenum chamber. In another aspect of the disclosure, a method comprises: pressurizing a manifold plenum chamber disposed in a pressure vessel of a nuclear reactor using primary coolant water drawn from the pressure vessel such that the manifold plenum chamber contains pressurized primary coolant water at a pressure that is higher than the pressure of primary coolant water in the pressure vessel; and pumping primary coolant water in the pressure vessel through a primary coolant flow circuit using turbo pumps whose turbines are driven by the pressurized primary coolant water contained in the manifold plenum chamber. In another aspect of the disclosure, an apparatus comprises: a nuclear core comprising a fissile material; a pressure vessel containing the nuclear core immersed in primary coolant water; a primary coolant water processing component located outside of the pressure vessel; and a coaxial pipe including an inner passage surrounded by an outer annulus. The coaxial pipe operatively connects the primary coolant water processing component with the pressure vessel, wherein one of the inner passage and the outer annulus conveys primary coolant water from the pressure vessel to the primary coolant water processing component, and wherein the other of the inner passage and the outer annulus conveys primary coolant water processed by the primary coolant water processing component from the primary coolant water processing component to the pressure vessel. In some embodiments the primary coolant water processing component comprises a pump that pumps primary coolant water. With reference to FIG. 1, an illustrative nuclear reactor of the pressurized water reactor (PWR) type 10 includes a pressure vessel 12, which in the illustrative embodiment is a cylindrical vertically mounted vessel. As used herein, the phrase “cylindrical pressure vessel” or similar phraseology indicates that the pressure vessel has a generally cylindrical shape, but may in some embodiments deviate from a mathematically perfect cylinder. For example, the illustrative cylindrical pressure vessel 12 has a circular cross-section of varying diameter along the length of the cylinder, and has rounded ends, and includes various vessel penetrations, vessel section flange connections, and so forth. Similarly, although the pressure vessel 12 is upright, it is contemplated for this upright position to deviate from exact vertical orientation of the cylinder axis. For example, if the PWR is disposed in a maritime vessel then it may be upright but with some tilt, which may vary with time, due to movement of the maritime vessel on or beneath the water. Selected components of the PWR that are internal to the pressure vessel 12 are shown diagrammatically in phantom (that is, by dotted lines). A nuclear reactor core 14 is disposed in a lower portion of the pressure vessel 12. The reactor core 14 includes a mass of fissile material, such as a material containing uranium oxide (UO2) that is enriched in the fissile 235U isotope, in a suitable matrix material. In a typical configuration, the fissile material is arranged as “fuel rods” arranged in a core basket. The pressure vessel 12 contains primary coolant water (typically light water, that is, H2O, although heavy water, that is, D2O, is also contemplated) in a subcooled state. A control rods system 16 is mounted above the reactor core 14 and includes control rod drive mechanism (CRDM) units and control rod guide structures configured to precisely and controllably insert or withdraw control rods into or out of the reactor core 14. The illustrative control rods system 16 employs internal CRDM units that are disposed inside the pressure vessel 12. Some illustrative examples of suitable internal CRDM designs include: Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety; and Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, Int'l Pub. WO 2010/144563 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety. In general, the control rods contain neutron absorbing material, and reactivity is increased by withdrawing the control rods or decreased by inserting the control rods. So-called “gray” control rods are continuously adjustable to provide incremental adjustments of the reactivity. So-called “shutdown” control rods are designed to be inserted as quickly as feasible into the reactor core to shut down the nuclear reaction in the event of an emergency. Various hybrid control rod designs are also known. For example, a gray rod may include a mechanism for releasing the control rod in an emergency so that it falls into the reactor core 14 thus implementing a shutdown rod functionality. Internal CRDM designs have advantages in terms of compactness and reduction in mechanical penetrations of the pressure vessel 12; however, it is also contemplated to employ a control rods system including external CRDM located outside of (e.g., above) the pressure vessel and operatively connected with the control rods by connecting rods that pass through suitable mechanical penetrations into the pressure vessel. The illustrative PWR 10 is an integral PWR, and includes an internal steam generator 18 disposed inside the pressure vessel 12. In the illustrative configuration, a central riser 20 is a cylindrical element disposed coaxially inside the cylindrical pressure vessel 12. (Again, the term “cylindrical” is intended to encompass generally cylindrical risers that deviate from a perfect cylinder by variations in diameter along the cylinder axis, inclusion of selected openings, or so forth). The riser 20 surrounds the control rods system 16 and extends upward, such that primary coolant water heated by the operating nuclear reactor core 14 rises upward through the central riser 20 toward the top of the pressure vessel, where it discharges, reverses flow direction and flows downward through an outer annulus defined between the central riser 20 and the cylindrical wall of the pressure vessel 12. The illustrative steam generator 18 is an annular steam generator disposed in a downcomer annulus 22 defined between the central riser 20 and the wall of the pressure vessel 12. The steam generator 18 provides independent but proximate flow paths for downwardly flowing primary coolant and upwardly flowing secondary coolant. The secondary coolant enters at a feedwater inlet 24, flows upward through the steam generator 18 where it is heated by the proximate downwardly flowing primary coolant to be converted to steam, and the steam discharges at a steam outlet 26. FIG. 1 does not illustrate the detailed structure of the steam generator 18 or the secondary coolant flow path. For example, feedwater inlet tubes and/or a feedwater plenum convey feedwater from the inlet 24 to the bottom of the steam generator 18, and steam outlet tubes and/or a steam plenum convey steam from the top of the steam generator 18 to the steam outlet 26. Typically, the steam generator comprises steam generator tubes and a surrounding volume (or “shell”) containing the tubes, thus providing two proximate flow paths that are in fluid isolation from each other. In some embodiments, the primary coolant flows downward through the steam generator tubes (that is, “tube-side”) while the secondary coolant flows upward through the surrounding volume (that is, “shell-side”). In other embodiments, the primary coolant flows downward through the surrounding volume (shell-side) while the secondary coolant flows upward through the steam generator tubes (tube-side). In either configuration, the steam generator tubes can have various geometries, such as vertical straight tubes (sometimes referred to as a straight-tube once-through steam generator or “OTSG”), helical tubes encircling the central riser 20 (some embodiments of which are described, by way of illustrative example, in Thome et al., “Integral Helical Coil Pressurized Water Nuclear Reactor”, U.S. Pub. No. 2010/0316181 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety), or so forth. The pressure vessel 12 defines a sealed volume that, when the PWR is operational, contains primary coolant water in a subcooled state. Toward this end, the PWR includes an internal pressurizer volume 30 disposed at the top of the pressure vessel 12 containing a steam bubble whose pressure controls the pressure of the primary coolant water in the pressure vessel 12. The pressure is controlled by suitable devices such as a heater 32 (e.g., one or more resistive heaters) that heats the steam to increase pressure, and/or a sparger 34 that injects cool water or steam into the steam bubble to reduce pressure. A baffle plate 36 separates the internal pressurizer volume 30 from the remainder of the sealed volume of the pressure vessel 10. By way of illustrative example, in some embodiments the primary coolant pressure in the sealed volume of the pressure vessel 12 is at a pressure of about 2000 psia and at a temperature of about 300° C. (cold leg just prior to flowing into the reactor core 14) to 320° C. (hot leg just after discharge from the reactor core 14). These are merely illustrative subcooled conditions, and a diverse range of other operating pressures and temperatures are also contemplated. Moreover, the illustrative internal pressurizer can be replaced by an external pressurizer connected with the pressure vessel by suitable piping or other fluid connections. A reactor coolant pump (RCP) 40 is configured to drive circulation of primary coolant water in the pressure vessel 12. The reactor coolant pump comprises a hydraulically driven turbo pump 41 disposed in the pressure vessel. In a suitable embodiment, the turbo pump 41 includes an impeller 42 performing pumping of primary coolant water in the pressure vessel 12, and a hydraulically driven turbine 44 mechanically coupled with the impeller 42 to drive the impeller 42. A hydraulic pump 46 pumps primary coolant water to generate hydraulic working fluid that drives the turbine 42. With reference to FIG. 2, operation of the reactor coolant pump 40 is described. In an operation S1, the hydraulic pump 46 is electrically driven. The pump motor of the hydraulic pump 46 is located outside the primary coolant flow loop, which has an advantage in that it is not exposed to the high temperature (e.g., 300-320° C. in some embodiments, although higher or lower coolant temperature is also contemplated) of the primary coolant. The hydraulic pump 46 operates to pump the primary coolant. However, it directly pumps only a relatively small portion of the total volumetric primary coolant flow passing downward through the downcomer annulus 22. The pumping S1 performed by the hydraulic pump 46 produces a high pressure flow FHP which however is a relatively low volume flow. In an operation S1, the turbo pump including the turbine 44 and impeller 42 acts as a flow transformer to convert the high pressure flow FHP to a higher volume (but lower pressure) flow FHV. That is, in the operation S2 the high pressure flow FHP drives the turbine 44 which in turn drives the mechanically coupled impeller 42 to generate the high volume flow FHV which flows in the primary coolant flow loop (e.g., down the downcomer annulus 22). With reference to FIGS. 3-6, an illustrative embodiment of the turbo pump is shown. Hydraulic working fluid W (diagrammatically indicated in FIG. 6) flows through an inlet 50 to a turbine chamber defined by a turbine housing 52. The flow of working fluid W into the turbine chamber causes a turbine rotor 54 to rotate in a rotational direction R indicated in FIG. 6. In the illustrative example of FIG. 6 (where the turbine housing 52 is shown in phantom to reveal internal components), the hydraulic working fluid W is injected into the turbine chamber on the side in a tangential direction to the turbine rotor 54. The hydraulic working fluid W imparts momentum to turbine blades of the turbine rotor 54. The turbine blades are shaped to convert the momentum of the working fluid W into the rotation R, and also to redirect the flow of the working fluid W generally toward an outlet 56 of the turbine 44. (Note that the outlet 56 is visible in FIGS. 3 and 6 but not in FIGS. 4 and 5.) The turbine blades may, for example, be of the axial or tangential or centrifugal type, or a combination thereof, with gaps or so forth in order to produce the desired combination of imparting the rotational force on the rotor 54 and redirecting flow of the working fluid W toward the outlet 56. The working fluid W discharges out of the turbine 44 via the outlet 56, which is on the opposite end of the turbine 44 from the flow impellor 42. The turbine rotor 54 is mounted on a shaft 60, and the impellor 42 mounted on the same shaft 60 as the turbine rotor 54—therefore, the impeller 42 rotates in same the rotational direction R as the turbine rotor 54. More generally, the hydraulically driven turbine 44 is mechanically coupled with the impeller 42 to drive the impeller 42. In the illustrative approach this mechanical coupling is via the common shaft 60; however, it is also contemplated to include a more complex coupling with gearing or so forth. The illustrative shaft 60 is supported in the turbine housing 52 by suitable bearings B1, B2. The blades of the impeller 42 are immersed in the primary coolant, and are shaped such that they drive a primary coolant flow P as shown in FIG. 6. In the illustrative example, the impeller 42 directs the primary coolant flow P across the turbine housing 52 in the same general direction as the turbine exhaust WE discharged from the outlet 56 by the turbine 44 (see FIG. 6). The illustrative impellor 42 is of the axial flow type, although other impellor types with radial (centrifugal) flow characteristics, mixed radial/axial flow characteristics, or so forth may be employed. The impeller 42 is enclosed within a tubular housing or impellor duct 62 (omitted in FIG. 6, and shown in partial phantom in FIGS. 3 and 4, to reveal internal components). In the embodiment of FIGS. 2-6 the impeller duct 62 is secured to the turbine housing 52 by four connecting plate members 64 radially spaced apart by 90° intervals; alternatively, in other embodiments the impeller duct may be secured elsewhere, or may be omitted entirely. The impeller 42 directs the primary coolant flow P across the turbine housing 52 in the same general direction as the turbine exhaust WE discharged from the outlet 56 by the turbine 44. Thus, the turbine exhaust flow WE additively combines with the primary coolant flow P to form the total discharge from the turbo pump. This is advantageous assuming that the electrically driven hydraulic pump 46 supplies the hydraulic working fluid W as primary coolant and/or as make-up water for making up lost primary coolant. In this arrangement, there is a single fluid connection, namely the inlet 50, connecting (via a connecting apparatus 50a in some embodiments) the electrically driven hydraulic pump 46 and the turbo pump 41 (or, more specifically, a single fluid connection 50 connecting the hydraulic pump 46 and the turbine 44). In particular, the outlet 56 is not connected with the hydraulic pump 46. With reference to FIG. 7-9, a suitable arrangement of the pumps shown in FIGS. 3-6 in the PWR of FIG. 1 is shown in further detail. An annular plate 70 is disposed in the downcomer annulus 22. Each turbo pump is mounted at an opening 72 of the annular plate 70. In the illustrative arrangement, each electrically driven hydraulic pump 46 drives the turbines 44 of two turbo pumps 41. The annular plate 70 includes twelve openings 72 for supporting twelve turbo pumps; however, other numbers of turbo pumps (including as few as a single turbo pump) may be employed, and the turbo pump-to-hydraulic pump ratio may be 1:1, 2:1 (as shown in FIG. 7), 3:1, or so forth, depending upon the load capacity of the hydraulic pumps. In addition to providing a mounting structure for the turbo pumps, the annular plate 70 separates the high pressure side (above the plate 70) and low pressure side (below the plate 70) of the turbo pumps 41. Toward this end, in some embodiments the impeller ducts 62 are sized to mate with the openings 72 so that primary coolant flow is limited to going through the impeller ducts 62 or through the inlet 90 to form the hydraulic working fluid W. The illustrative electrically driven hydraulic pumps 46 are external canned motor pumps that feed the inlets 50 of two turbines 44 with relatively short hydraulic lines that are internal to the pressure vessel 12. The canned motor pumps are suitably mounted on respective flanged openings in the pressure vessel 12. In these embodiments a canned motor pump housing 76 of the pump 46 is part of the primary pressure boundary also including the pressure vessel 12. In these canned pump designs, there is no seal between the shaft 78 of the working fluid pump 80 and the motor (comprising a stator 82 and a rotor 84). The internals of the electrically driven hydraulic pump 46 are wet at the primary pressure. This type of pump is known for use as boiler circulation pumps. The canned motor pump external housing 76 is effectively an extension of the reactor vessel primary boundary defined by the pressure vessel 12. In operation, a portion of the primary coolant flow P flowing downward in the downcomer annulus 22 is captured by an inlet 90 and flows into the electrically driven hydraulic pump 46. This captured primary coolant forms the hydraulic working fluid W, and is pressurized by operation of the hydraulic pump 46 (and more particularly by the operation of the working fluid pump 80 driven by the motor 82, 84). The pump 80 discharges the working fluid W into the inlet 50 of the turbine 44 where it drives the turbine rotor 54 (see FIG. 6) and the impeller 42 via the common driveshaft 60. In some embodiments, about ⅛th (i.e., about 10-15%) of the primary coolant flow P is captured by the inlet 90 and forms the working fluid W. An off-the-shelf boiler circulation pump typically has a head of around 200 psi, whereas some contemplated small modular reactor (SMR) designs of the integral PWR type are expected to have a head of about 21 psi. Thus, an off-the-shelf canned motor pump of the type commonly used for boiler circulation is expected to be well-suited for use as the electrically driven hydraulic pump 46. With particular reference to FIG. 8, in some embodiments the pressure vessel 12 is constructed in two sections, i.e. an upper section 12U and a lower section 12L, that are joined at a vessel flange 12F. In such embodiments the turbo pump 41 is readily accessible when the upper pressure vessel section 12U is lifted off by a crane or other lifting device during maintenance operations. Alternatively, access may be provided by manways, or the RCPs 40 may be located closer to the top of the pressure vessel and be accessible when a vessel head is lifted off for maintenance. In the illustrative embodiment in which the electrically driven hydraulic pumps 46 are canned pumps, the pumps 46 are expected to receive a substantial amount of heat from the reactor. Accordingly, in some embodiments provision is made for cooling the electrically driven hydraulic pumps 46. In the illustrative embodiment, a heat exchanger 92 is employed for this purpose. The “hot” side of the heat exchanger 92 flows fluid from inside the pump 46, while the “cold” side of the heat exchanger 92 is cooled by active flow of coolant delivered via coolant lines 94. The RCP embodiments described with reference to FIGS. 1-9 provide numerous advantages. The design enables the electrically driven hydraulic pump 46 to operate at or near its point of optimal efficiency, while still providing high volume (but lower pressure) flow via the transformative action of the turbo pumps 41. In effect, the turbo pumps transform the excess pressure head of the pump 46 into volumetric flow. The external pump in the illustrative embodiment comprises a canned pump mounted on a flanged opening, which reduces vessel penetrations. Indeed, if the canned pump is treated as part of the pressure vessel boundary, then there are only the electrical penetrations for powering the canned pump 46. The turbo pumps located inside the pressure vessel 12 can have as few as a single moving part, if the impeller 42 and the turbine rotor 54 of the turbine 44 define a unitary rotating element. The RCPs are located in the reactor downcomer annulus 22, and so the RCPs can remain in place during refueling, and do not need to be removed to access the reactor core 14. On the other hand, the electrically driven hydraulic pumps 46 are mounted on an exterior flange and can be removed for repair or replacement without disassembling the reactor. The embodiments of FIGS. 1-9 are merely illustrative, and numerous variations are contemplated. For example, the illustrated canned pump embodiment of the electrically driven hydraulic pumps 46 can be replaced by dry pump, an external pump that is not mounted to the pressure vessel 12, or so forth. FIGS. 10-12 illustrate some variant embodiments. With reference to FIG. 10, in one variant embodiment the canned electrically driven hydraulic pump 46 flange-mounted onto the pressure vessel 12 is replaced by an external source of hydraulic working fluid Wext. Toward this end the inlet 50 is connected with a vessel penetration 100. At the exterior of the pressure vessel 12, an inlet pipe 50ext supplying the working fluid Wext feeds into the vessel penetration 100. The outlet 56 of the turbine 44 in this embodiment is coupled by a short pipe 102 with a second vessel penetration 104. At the exterior of the pressure vessel 12, an outlet pipe 102ext carries away the hydraulic working fluid Wext exiting from the turbine 44. Because in this embodiment the discharge from the outlet 56 of the turbine 44 does not add to the pumped primary coolant flow P, the embodiment of FIG. 10 optionally “flips” the turbo pump so that the impeller 42 discharges the primary coolant flow P away from the turbine 44. This also entails redesign of the impeller blades to optimize them for the orientation shown in FIG. 10. The design of FIG. 10 has the disadvantage of introducing vessel penetrations 100, 104. However, these penetrations can be of small diameter so as to reduce the likelihood of and/or likely severity of a LOCA at these penetrations. An advantage of the design of FIG. 10 is that the external pipes 50ext, 102ext provide flexibility as to the source of the working fluid Wext. In some embodiments the working fluid may be primary coolant taken from a reactor coolant inventory and purification system (RCIPS). In other embodiments the working fluid Wext may be something other than reactor coolant, e.g. a separate water supply. With reference to FIGS. 11 and 12, in another variant embodiment the turbo pumps are located inside the central riser 20, rather than being located in the annular downcomer annulus 22 as in the embodiments of FIGS. 1-10. The embodiment of FIGS. 11 and 12 is like the embodiment of FIGS. 1-19 in that a fraction of the primary coolant flow is captured and used as the hydraulic working fluid for driving the turbines 44. However, in the central riser, the pumped primary coolant flow P is upward. Accordingly, the inlet 90 (see, e.g. FIG. 9) is replaced by an inlet 90c embodied as an open lower end of a pipe centrally located inside the central riser 20. The turbo pumps 41 are also inverted as compared with the embodiment of FIGS. 1-9, so that the turbines 44 discharge upward in order to additively combine with the primary coolant flow P. Because the turbo pumps 41 located inside the central riser 20 are not proximate to the outer wall of the pressure vessel 12, a piping assembly 120 is provided to convey the captured primary coolant out to the electrically driven hydraulic pumps and to convey the resulting hydraulic working fluid back to the turbo pumps 41 inside the central riser 20. In the alternative embodiment of FIGS. 11 and 12, the turbo-pumps 41 are mounted in the hot leg of the primary coolant flow circuit, that is, inside the central riser 20 in the illustrative embodiment. A configuration of eight turbo-pumps in two groups of four is shown in FIGS. 11 and 12. The open loop feed lines are routed through a modified pressurizer 30c at the top of the pressure vessel 12. The inlet 90c for the electrically driven hydraulic pump or pumps is embodied as the larger pipe in the center of the piping assembly 120. In the illustrative piping assembly 120, the inlet 90c branches to external hydraulic pumps 46. Four return lines each feed the turbines 44 of two turbo-pumps 41 so as to drive all eight turbo pumps 41. In this configuration, the turbo-pumps 41 are mounted inverted (as compared with the embodiment of FIGS. 1-9) so that the impeller drives the primary coolant flow P upward and the turbines 44 discharge upward. The electrically driven hydraulic pumps are not shown in FIGS. 11 and 12, but are suitably mounted on the pressurizer 30c in either a vertical or horizontal orientation. These pumps could remain mounted on the pressurizer when the latter is lifted off and moved aside during refueling. (The electrical feeds and any heat exchanger cooling lines would likely be disconnected during this operation). Likewise, the connections to the turbo-pumps 41 optionally would remain intact during refueling. In the embodiments of FIGS. 3-9, the electrically driven hydraulic pump 46 is connected with the turbo pump 41 by the inlet 50 to the turbine chamber defined by the turbine housing 52. In the embodiments of FIGS. 7-9, each hydraulic pump 46 drives two turbo pumps 41—more generally, the number of turbo pumps driven by a single hydraulic pump may be one, two (as per FIGS. 7-9), three, or more. Installation of the primary coolant pumping system of FIGS. 3-9 entails installing the annular plate 70 in the downcomer annulus 22, mounting the turbo pumps 41 in the openings 72 in the plate 70, mounting the hydraulic pumps 46 onto the pressure vessel 12, and installing the inlet piping 50 connecting the hydraulic pumps 46 with the turbo pumps 41. Such installation is complex, and additionally radial balance of the active primary coolant pumping is contingent upon balanced operation of the hydraulic pumps 46 that are spaced apart around the downcomer annulus 22. For example, as best seen in FIG. 7, the loss of a single one of the hydraulic pumps 46 would result in loss of primary coolant pumping in one-sixth of the circumference of the downcomer annulus 22. Loss of one of the turbo pumps 41 would also adversely affect operational balance, but less so because (1) the opening 72 in which the non-operating turbo pump is installed would continue to pass primary coolant and (2) there are twice as many turbo pumps as hydraulic pumps in this embodiment. With reference to FIGS. 13-20, one approach for reducing these potential disadvantages is to employ a manifold plenum chamber 140 to drive the turbines. With particular reference to FIGS. 15-18, each illustrative turbo pump 141 includes an impeller 142 driven by a turbine 144. The turbo pump 141 includes a turbine inlet 150 passing into in a housing or casing 152 that defines both a turbine plenum and the flow path for the fluid pumped by the impeller 142. As best seen in FIGS. 17 and 18, the impeller 142 and a turbine rotor 154 are constructed as a unitary rotating element that is housed in the unitary housing or casing 152. Working fluid flowing into the turbine inlet 150 pushes against the blades of the turbine rotor 154 to cause it to rotate. The working fluid discharges from the turbine plenum defined by the housing or casing 152 via turbine outlets 156. The rotation also carries the impeller 142 which is part of the unitary rotataing element including the impeller 142 and turbine rotor 154. The rotation of the impeller 142 draws primary coolant water generally “downward” in the views shown in FIGS. 13-18, that is, pumps the primary coolant water from a suction side 158 to a discharge side 160. The illustrative turbine rotor 154 has a hybrid Francis-Pelton design that combines the features of both a Francis and Pelton turbine. The curved shape of the blade portion 154P coincident with the inlet 150 captures the impulse similar to the cuplike shape of a Pelton turbine blade. The angled vane of the turbine blade portion 154F takes the downward annular flow and converts it to angular momentum similar to a Francis turbine. A space between the top of the turbine blade and a blocker disk 162 at the top of the turbine annulus provides relief of the flow from the Pelton turbine to distribute circumferentially for the Francis turbine stage. A disk 164 at the bottom of the rotating element connected via a shaft accommodates a main thrust bearing 166. The thrust bearing 166 and a radial bearing 168 are shown only in FIG. 16. On the bottom of the turbine annulus, the rotating barrel slopes outward to direct the turbine exhaust to the external housing outlet ports 156. Curved fixed vanes 170 span the annular space of the turbo pump outlet to transfer the load of the main thrust bearings 166 to the external housing 152. The turbines 144 of the turbo pumps 141 are in operative fluid communication with the manifold plenum chamber 140 so as to be driven by pressurized primary coolant water in the manifold plenum chamber 140. The manifold plenum chamber 140 is a “plenum chamber” in that it is a pressurized housing or chamber containing pressurized primary coolant water at a pressure higher than the pressure of primary coolant water in the pressure vessel 12. The manifold plenum chamber 140 is a “manifold” plenum chamber in that it distributes the pressurized primary coolant water to the turbines 144 of the plurality of turbo pumps 141. The illustrative manifold plenum chamber 140 has an annular shape and fits into the downcomer annulus 22. The illustrative annular manifold plenum chamber 140 can comprise a single connected annular plenum, or alternatively one or more (or, more generally, N) “vertical” isolation plates may be disposed at selected positions around the annular manifold plenum chamber 140 to divide the plenum into N+1 mutually isolated pressurized volumes. The turbo pumps 141 are disposed in openings 174 (see FIG. 19) of the manifold plenum chamber 140 so that the combination of the manifold plenum chamber 140 and the turbo pumps 141 form a reactor coolant pump (RCP) assembly having the suction side 158 and the discharge side 160 on the opposite side of the RCP assembly from the suction side 158. The manifold plenum chamber 140 serves the same purpose in the embodiment of FIGS. 13-20 as the inlet pipe 50 of embodiments of FIGS. 3-9, that is, the manifold plenum chamber 140 delivers pressurized primary coolant water to the turbine inlet 150 of the turbo pump 141. Toward this end, the turbo pumps 141 are disposed in openings 174 of the manifold plenum chamber 140 such that the manifold plenum chamber 140 encloses the inlets 150. In the illustrative embodiment, a flow distribution header 180 is disposed in the manifold plenum chamber 140 at each opening 174 in which a turbo pump 141 is installed. Each flow distribution header 180 includes an area-reducing nozzle 182 aligned with the inlet 150 of the turbine 144 of the respective turbo pump 141 to inject primary coolant water from the manifold plenum chamber 140 into the turbine 144 in a direction optimized to engage with the curved shape of the Pelton blade portion 154P. With continuing reference to FIGS. 13-20 and with further reference to FIGS. 21-23, the manifold plenum chamber 140 can be pressurized using any suitable pumping configuration. In general, the operational process comprises: (1) pressurize the manifold plenum chamber 140 disposed in the pressure vessel 12 using primary coolant water drawn from the pressure vessel 12 (and more particularly from the suction side 158) such that the manifold plenum chamber 140 contains pressurized primary coolant water at a pressure that is higher than the pressure of primary coolant water in the pressure vessel 12; and (2) pump primary coolant water in the pressure vessel 12 through the primary coolant flow circuit (e.g., flowing upward from the reactor core 14 through the central cylindrical riser 20 and back down through the downcomer annulus 22 back to the reactor core 14) using the turbo pumps 141 whose turbines 144 are driven by the pressurized primary coolant water contained in the manifold plenum chamber 140. In the illustrative example, electrically driven hydraulic pumps 190 draw primary coolant from the pressure vessel and pump the primary coolant into the manifold plenum chamber 140 in order to pressurize the manifold plenum chamber 140. As shown in FIG. 23, in the illustrative example of FIGS. 13-20 the pumps 190 are external pumps. With particular reference to FIGS. 21 and 22, each external pump 190 is operatively connected via a coaxial pipe 192 and a coaxial header 194. Primary coolant water is drawn into the pump 190 via an inlet 196 of the coaxial header 194 and flows through the inner passage of the coaxial pipe 192 to the pump 190. The pumped primary coolant water flows back through the outer annulus of the coaxial pipe 192 and down an outlet 198 into the manifold plenum chamber 140. Alternatively, it is contemplated to employ the inner passage of the coaxial pipe as the outlet (flowing from the pump to the reactor pressure vessel) and the outer annulus of the coaxial pipe as the inlet (flowing from the pressure vessel to the pump). The coaxial pipe 192 and coaxial header 194 advantageously requires only one circular opening in the reactor vessel 12 for both inlet and outlet. This arrangement reduces the likelihood of a loss of coolant accident (LOCA) at this vessel penetration, and reduces the volumetric throughput in the event that a LOCA does occur there. It will be appreciated that more generally the coaxial pipe 192 including an inner passage surrounded by an outer annulus can be used to connect a primary coolant water processing component (such as the illustrative pump 190, or a component that adds a selected constituent to the primary coolant water, or a primary coolant water filtering component, or so forth) with the pressure vessel such that (i) one of the inner passage and the outer annulus conveys primary coolant water from the pressure vessel to the primary coolant water processing component, and (ii) the other of the inner passage and the outer annulus conveys primary coolant water processed by the primary coolant water processing component from the primary coolant water processing component to the pressure vessel. The illustrative coaxial header 194 can be used for such applications, optionally with suitable modifications to direct or control (i) flow of primary coolant water into the coaxial pipe from the pressure vessel or a component therein and (ii) flow of processed primary coolant water from the coaxial pipe into the pressure vessel or a component therein (such as from the coaxial pipe 192 into the manifold plenum chamber 140 in the illustrative embodiment). The manifold plenum chamber 140 is pressurized by the external hydraulic pumps 190 using a portion of the primary coolant water taken from the primary coolant water loop or circuit flowing in the pressure vessel 12. The internal turbo pumps 141 convert the excess head (that is, pressure) generated by the external hydraulic pump 190 into a larger volumetric flow suitable for providing active pumping of the primary coolant water in the reactor pressure vessel 12. (See FIG. 2 and related text). In this way, the external hydraulic pump 190, the manifold plenum chamber 140, and the turbo pumps 141 transforms pressure head into volumetric flow. This is analogous to an electrical circuit in which a transformer converts voltage to current. The manifold plenum chamber 140 is analogous to an electrical capacitor in that it accumulates and stores fluid pressure (analogous to an electrical capacitor storing voltage or charge) for use by the turbo pumps 141. The electrical pumps 190 are referred to as external pumps because they are located outside of the pressure vessel 12. However, it is to be understood that some or even most of the components of the pump 190 may be within the pressure boundary of the pressure vessel 12. In some embodiments, only the impeller is within the pressure boundary of the pressure vessel 12, and that impeller connects with a “dry” rotor via a driveshaft passing through a graphalloy-based vessel penetration. In other embodiments, the impeller and a “wet” rotor may be inside the pressure boundary and in contact with primary coolant, and a “canned’ structure separates the wet rotor from a dry stator. In yet other embodiments, the entire motor including both the stator and the rotor are “wet”, and are disposed in a “canned” housing into which electrical power is delivered via suitable electrical vessel penetrations. In each case, the external pump 190 is located outside the pressure vessel 12 and hence is readily accessible during reactor shutdown in order to perform maintenance or replacement. Note that details of the electrical pumps 190 (e.g., rotor, stator, impeller components) are not shown in the drawings. The conversion of hydraulic pump pressure head to volumetric flow enables a decoupling of the hydraulic pump head from the optimal head specifications for the reactor coolant system (RCS). For example, in some contemplated embodiments the external hydraulic pump 190 is expected to operate at a pump head of 170 psi which is typical of a boiler circulation pump. This is many times greater than the pressure drop of the reactor primary loop for a typical compact pressurized water reactor (PWR). The external hydraulic pump 190 can be operated at its best efficiency point (BEP) on the pump head curve as a function of volumetric flow rate. Likewise, the turbine 144 and impellor 142 of the turbo pump 141 can be designed for the optimal RCS pressure head and the turbo-pump portion of the total RCS flow. This decoupling of head specifications allows both pumps systems to be optimized for best efficiency. In some embodiments, the flow rate delivered to the outlet 198 by the external pump 190 is approximately one-eighth (⅛) of the flow rate for the primary coolant flow circuit inside the pressure vessel 12. As a consequence, only a small portion (e.g., about 10%-15%) of the primary coolant flow in the pressure vessel 12 is drawn off by the electrical pump 190 in order to pressurize the manifold plenum chamber 140. Operation of the turbo pumps 141 by the pressurized primary coolant water in the manifold plenum chamber 140 provides active pumping of the primary coolant in the pressure vessel 12. The discharge from turbines 144 at the turbine outlets 156 contributes to the pumping, but the impellers 142 provide most of the flow. In the illustrative example of FIGS. 13-23, twelve turbo-pumps 141 are spaced apart circumferentially inside the reactor downcomer annulus 22. In this example, there are six external hydraulic pumps 190 feeding the twelve turbo-pumps 141, providing a 2:1 ratio of two turbo pumps 141 per external hydraulic pump 190. This is the same ratio as in the example of FIGS. 3-9; however, the manifold plenum chamber 140 provides even distribution of the pressurized primary coolant water to the turbo pumps 141 which is robust against the failure of one or two or even a few more of the electrical pumps 190. For example, loss of one of the pumps 190 may reduce the overall pressure inside the manifold plenum chamber 140, but the manifold plenum chamber 140 will continue to distribute pressure to the turbo pumps 141 and so all twelve of the turbo pumps 141 are expected to continue to operate. Moreover, if the pumps 190 are not operated at their maximum output level, then loss of one (or even perhaps two or more) of these pumps 190 can be compensated by running the remaining pumps at higher output level. In contrast, in the embodiment of FIGS. 3-9 loss of a single one of the electrical pumps 46 results in loss of active pumping over a 90° arc of the downcomer annulus 22. In the illustrative example of FIGS. 13-23, the circumferential manifold plenum chamber 140 is 4 mounted on the reactor upper shroud. Advantageously, the turbo pumps 141 are removable from the top individually, or the entire assembly (shroud and manifold plenum chamber 140) can be removed. (The entire assembly would usually only be removed for inspection of the reactor vessel at intervals longer than the refueling cycle). In the illustrative embodiment, the manifold plenum chamber 140 is sandwiched in between the gussets 200 of the reactor upper shroud. (Best seen in FIG. 13). In this way, the assembly can be inserted without damage to the manifold plenum chamber 140. The tapered ends of the gussets 200 guide the assembly into the reactor vessel. Other mounting structures and/or retaining elements can additionally or alternatively be employed in mounting the manifold plenum chamber 140 inside the pressure vessel 12, and specifically in the downcomer annulus 22 in this embodiment. Securing the manifold plenum chamber 140 inside the pressure vessel 12 using bolts or other removable fasteners advantageously enables the manifold plenum chamber 140 to be easily removed for maintenance; however, it is also contemplated for the manifold plenum chamber 140 to be welded into place. The turbo-pumps 141 are bolted to the manifold plenum chamber 140 at the respective openings 174 from the top (suction side) only, without any fasteners at the lower (discharge) side. In this way, a turbo pump 141 can be removed from above by disengaging the fasteners (e.g., bolts) and lifting the turbo pump 141 upward away from the manifold plenum chamber 140. The bolts or other fasteners secure a flange to the top (suction side) of the manifold plenum chamber 140 and, optionally along with a sealing gasket, provides a seal on the top (suction side) of the manifold plenum chamber 140 for the turbo-pumps 141. A compression seal ring 202 (best seen in FIG. 15) forms the seal on the bottom (discharge side) of the manifold plenum chamber 140. The coaxial inlet/outlet header 198 connects to the manifold box via a male/female fitting with O-ring seals, or by another suitable sealed connection configuration. It is to be understood that the embodiment of FIGS. 13-23 is illustrative, and various components can be replaced by other components providing similar functionality. With reference to FIGS. 24-30, another illustrative embodiment employing the manifold plenum chamber 140 is described. Each illustrative turbo pump 241 includes an impeller 242 driven by a turbine 244 having a turbine inlet 250 passing into in a turbine housing or casing 252. In this embodiment the impeller 242 is located “above” the turbine 244. A turbine rotor 254 is disposed inside the turbine housing or casing 252, and working fluid (that is, pressurized primary coolant water flowing into the inlet 250 from the manifold plenum chamber 140) rotates the turbine rotor 254 as the working fluid transitions toward a generally downward flow that exits at a turbine outlet 256 at the “bottom” of the turbine housing or casing 252. As best seen in FIG. 30, the impeller 242 and a turbine rotor 254 are mounted on a common shaft 260 so as to rotate as a unitary rotating element. The impeller 242 is disposed in a tubular housing or duct 262, and primary coolant water pumped by the impeller 242 flows downward on the outside of the turbine 244. The discharge from the turbine outlet 256 also flows downward so as to add to the pumping of the impeller 242. Analogous to the embodiment of FIGS. 13-23, the turbo pumps 241 and the manifold plenum chamber 240 of the embodiment of FIGS. 24-30 form a reactor coolant pump (RCP) assembly having the suction side 158 above the RCP assembly and the discharge side 160 below the RCP assembly. The impeller 242 has an axial flow design, and the turbine rotor 254 has tangential/axial turbine blades. Tangential flow from the inlet 250 impacts tangential blades 254T then engages axial blades 254A that turn the working fluid toward an axial flow that discharges at the turbine outlet 256. As best seen in FIG. 30, there are three banks of axial blades 254A in the illustrative example. Each successive stage of axial blades 254A has increasing blade angle so that the tangential component of the flow velocity is reduced to zero (or close to zero) at the turbine outlet 256. The manifold plenum chamber 140 delivers pressurized primary coolant water to the turbine inlets 250 of the turbo pumps 241. With reference to FIGS. 27 and 28, the turbo pumps 241 are disposed in openings 274 of the manifold plenum chamber 140 (see FIG. 28) such that the manifold plenum chamber 140 encloses the inlets 250 of the turbines 244. In the illustrative embodiment, a flow distribution header 280 (best seen in FIG. 27) is sandwiched between the top and bottom plates of the manifold plenum chamber 140 (see FIG. 28) at each opening 174 in which a turbo pump 241 is installed. Each flow distribution header 280 includes a nozzle gate 282 aligned with the inlet 250 of the turbine 244 of the respective turbo pump 241 to inject primary coolant water from the manifold plenum chamber 140 into the turbine 244 in a tangential direction so as to engage with the tangential blades 254T. In the illustrative example, the flow distributor header 280 defines three sides of the nozzle gate 282 while the top of the manifold plenum chamber 140 defines the fourth side of the nozzle gate 282. The flow distributor 280 includes a bottom conical flange for the lower seal. The illustrative flow distributor 280 includes five openings through which the impellor 242 pumps primary coolant water through the RCP assembly. With continuing reference to FIGS. 24-30, the manifold plenum chamber 140 can be pressurized using any suitable pumping configuration, such as using the external electrically driven hydraulic pumps 190 of the embodiment of FIGS. 13-23. Note that the pumps 190 are not shown in the embodiment of FIGS. 24-30; however, the embodiment of FIGS. 24-30 shows an alternative operative connection configuration for drawing primary coolant water from the pressure vessel 12 into the pump and pumping the pressurized primary coolant water into the manifold plenum chamber 140 to pressurize the chamber 140. As best seen in FIG. 28, the operative connection includes an upwardly curved inlet elbow pipe 192 disposed inside the pressure vessel 12 that collects and flows primary coolant water from the pressure vessel 12 through a vessel penetration and into an external inlet pipe 193 to supply primary coolant water to the external pump. The pressurized primary coolant water is delivered back into the pressure vessel (and more particularly into the manifold plenum chamber 140) through an external outlet pipe 194 and a vessel penetration immediately below that which passes the inlet flow. An external hydraulic pump nozzle header 195 (see FIG. 25) encloses the separate inlet/outlet lines so that external piping is not present, which reduces the likelihood of a LOCA at this penetration. The number of pumps (or, equivalently for this illustrative example, the number of external pump nozzle headers 195) can be as few as one (i.e., a single pump pressurizing the manifold plenum chamber 140) or can be two, three, four, or more. If the manifold plenum chamber 140 is divided into multiple isolated volumes by isolation plates, then each volume include at least one pump/header 195 to provide pressurization of that isolated volume. In general, two or more pumps/headers 195 per plenum volume ensures advantageous redundancy. In the illustrative example, there are 12 turbo pumps 141 and six external hydraulic pump nozzle headers 195, providing a 2:1 turbo pump/external pump ratio. In the embodiment of FIGS. 24-30, the manifold plenum chamber 140 is mounted via the split gussets 200 (see FIG. 24) as in the embodiment of FIGS. 13-23. The turbo pumps 141 can again be mounted via fasteners from the suction side 158 only, with a lower compression seal ring to seal the discharge side 160. In the embodiments of FIGS. 13-23 and 24-30, the RCP assembly including the manifold plenum chamber 140 and the turbo pumps 141 (FIGS. 13-23) or turbo pumps 241 (FIGS. 24-30) is disposed in the downcomer annulus 22. This arrangement has substantial advantages: this is the “cold” leg of the primary coolant flow loop or circuit so that the temperature is slightly lower; arrangement in the downcomer annulus frees up space inside the central riser 20 for other components such as internal control rod drive mechanisms (CDRM's), instrumentation, and so forth; and the downcomer annulus 22 is generally accessible during maintenance. However, it is also contemplated to dispose the RCP assembly elsewhere, such as inside the central riser 20 (analogous to the embodiment of FIG. 12, but including a manifold plenum chamber inside the central riser). With reference to FIG. 31, an embodiment includes two RCP assemblies. The first RCP assembly, i.e. a “downcomer” RCP assembly, is disposed in the downcomer annulus 22 and comprises the annular manifold plenum chamber 140 and turbo pumps 141 (FIGS. 13-23) or turbo pumps 241 (FIGS. 13-23). A second RCP assembly, i.e. a “riser” RCP assembly, is disposed inside the central riser 20, and comprises a riser manifold plenum chamber 340 and turbo pumps 341. As already described, the RCP assembly in the downcomer annulus 22 has its suction side 158 above the RCP assembly and its discharge side 160 below the RCP assembly, so that the RCP assembly generates or assists the downward flow of primary coolant water in the downcomer annulus 22. In contrast, inside the cylindrical riser 20 the primary coolant flows upward, away from the nuclear reactor core. Accordingly, the RCP assembly disposed inside the central riser 20 has a suction side 358 disposed below the RCP assembly and a discharge side 360 disposed above the RCP assembly. In FIG. 31, large open arrows passing through the turbo pumps 141, 241, 341 show the pumped flow of primary coolant water produced by these pumps. The turbo pumps 341 can be variously embodied, for example as the turbo pumps 141 of the embodiment of FIGS. 13-23 or as the turbo pumps 241 of the embodiment of FIGS. 24-30. In either illustrative case, however, the turbo pumps 341 should be operatively “upside-down” as compared with the turbo pumps 141 or turbo pumps 241, so as to produce the desired orientation of the suction and discharge sides 358, 360. In some embodiments the fasteners for securing the turbo pumps 341 to the riser manifold plenum chamber 340 are at the discharge side 360 so that the turbo pumps 341 can be removed from above same as the turbo pumps 141, 241. Differences in temperature and pressure between the volume inside the riser 20 and the downcomer annulus 22 tend toward constructing the downcomer manifold plenum chamber 140 and the riser manifold plenum chamber 340 as separate plenums in fluid isolation from each other. The primary coolant water for charging the riser manifold plenum chamber 340 is preferably drawn from inside the central riser 20, and more particularly from the suction side 358 of the riser RCP assembly (that is, from below the riser RCP assembly), for example by an illustrated inlet pipe 370. The drawn primary coolant water is pressurized by a suitable pump and the pressurized primary coolant water is injected into the riser manifold plenum chamber 340 via illustrative outlet pipes 372. Diagrammatic FIG. 31 shows only the ends of the piping 370, 372 terminating at or near the riser manifold plenum chamber 340; the distal connections to the pump (e.g., one of the pumps 390) is not shown. As already mentioned, the riser manifold plenum chamber 340 and the downcomer manifold plenum chamber 140 should be in fluid isolation from each other. However, in some embodiments the riser manifold plenum chamber 340 and the downcomer manifold plenum chamber 140 are arranged in the same plane (e.g., at the same height, as shown in FIG. 31) and may optionally serve as a structural element for assisting in supporting the central riser 20 or other components. The preferred embodiments have been illustrated and described. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
046541853	abstract	A deep beam head for a nuclear reactor and an improved reactor containing such a head where the upper horizontal support plate of a calandria in the reactor forms a sealing plate for the reactor vessel. The sealing plate has a ring member about the upper periphery thereof that is secured to the top of the pressure vessel cylindrical wall and reinforcing members extend across the sealing plate and are welded to the ring, while transverse cross-members extend across the sealing plate and are welded to the reinforcing members. The calandria may be removed from the reactor while attached to the ring member to provide ready access to the reactor internals.
	abstract	A method of extending a life expectancy of a high-temperature piping, includes removing a heat insulation material which covers the piping having a high creep rupture risk, and lowering an outer surface temperature of piping, wherein a width of an exposed portion obtained is twice or more a distance from a peeled-off end portion of the exposed portion to a portion where a compressive stress is asymptotical to 0 after a change in stress between a tensile stress and the compressive stress occurring in the piping due to the removal of the heat insulation material is made from the tensile stress to the compressive stress, and the distance is calculated based on the following formulae, βx=5,
	abstract	A reflector assembly for a molten chloride fast reactor (MCFR) includes a support structure with a substantially cylindrical base plate, a substantially cylindrical top plate, and a plurality of circumferentially spaced ribs extending between the base plate and the top plate. The support structure is configured to encapsulate a reactor core for containing nuclear fuel. The MCFR also includes a plurality of tube members disposed within the support structure and extending axially between the top plate and the bottom plate. The plurality of tube members are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core.
048511846	abstract	A building, especially a nuclear plant, includes concrete walls enclosing components such as plant components as a protection against external action. The concrete walls have exposed locations, and the concrete walls have double-layered regions at the exposed locations with double layers defining hollow spaces therebetween. A damping material may fill the hollow space.
	summary
045267448	abstract	A fuel assembly for a boiling water reactor comprises a plurality of fuel rods (2, 2'), which constitute four partial bundles and are surrounded by a fuel channel system (1) comprising one partial tube for each partial bundle. Each of the four partial bundles rests on a bottom tie plate (19) and is positioned with respect to the others by means of a common top tie plate (31), which is provided with a lifting loop (33) which is sufficiently strong to be able to lift the four partial bundles simultaneously, a major part of the lifting force being transmitted to said bottom tie plates via a plurality of supporting fuel rods (2').
	claims	1. A reactor bottom repairing method of sealing a crack occurring on a surface of a cylindrical body penetrating through a lower end portion of a reactor bottom portion and fixed to the reactor bottom portion by using a welding torch, the reactor bottom portion including an inclined surface inclined relative to the cylindrical body, the method comprising:providing an apparatus for driving a welding torch, the apparatus including six control shafts including a pivot shaft for entirely pivoting the apparatus, an advance shaft for driving the welding torch in a radial direction, a vertical shaft for driving the welding torch in a vertical direction, an inclined drive shaft for driving the welding torch along an inclined angle between an inclined surface of a bottom head and the cylindrical body, a torch rotating shaft for continuously changing a torch direction from the cylindrical body side surface up to a bottom head, and a head rotating shaft for correcting a torch position shifted due to rotation of the inclined drive shaft;emitting a first heating laser beam to a cracked portion to remove moisture from the cracked portion;driving the welding torch by the apparatus including the six control shafts along the inclined surface of the lower end portion of the reactor bottom portion and the cylindrical body, and while driving the welding torch changing a direction of the welding torch from a side surface of the cylindrical body to the lower end portion of the reactor bottom surface;emitting from the welding torch a first welding laser beam following a portion to be welded to the lower end portion of the reactor bottom portion to form a welded portion, aposition of the welding laser beam changing to follow the portion to be welded by a welding machine correcting a position of the welding torch shifted by rotation of a drive shaft of the welding torch; andemitting a second heating laser beam and a second welding laser beam to an entire surface of the cylindrical body inside the reactor and the welded portion between the cylindrical body and the lower end portion of the reactor bottom portion thereby preventing a new crack from occurring. 2. The reactor bottom repairing method of preventing leakage of reactor water according to claim 1, further comprising:covering a control rod drive (CRD) housing with a cap-shaped member to cover the CRD housing from an upper end thereof up to an upper end surface of the cylindrical body, the cap-shaped member being made of a material having a shape not interfering with an overlay welded portion at a corner between the CRD housing and the cylindrical body thereinside, having an outside diameter substantially matching with that of the cylindrical body, and having a low stress corrosion cracking sensitivity;applying first laser seal welding to the cylindrical body in a lower end portion of the member;andapplying second laser seal welding to a side surface of the CRD housing in an upper portion thereof to thereby prevent reactor water from leaking from a welded portion between the CRD housing and the cylindrical body and a heat affected portion of the CRD housing. 3. The reactor bottom repairing method, according to claim 2, further comprising applying third laser seal welding between a lower end portion of the cap-shaped member and the cylindrical body, wherein preceding emitting the welding beam, an inert gas issprayed to remove moisture from the melt portion to thereby prevent a moisture emitting at a welding period. 4. The reactor bottom repairing method, according to claim 2, further comprising applying third laser seal welding between an upper end portion of the cap-shaped member and the CRD housing, wherein preceding the welding beam radiation, an inert gas is sprayed to lower a water level of an inner portion of the cap-shaped member and to remove moisture from the melt portion to thereby prevent a moisture emitting event. 5. A reactor bottom repairing method of sealing a crack occurring on a surface of a stub tube of a penetrating portion of a control rod drive (CRD) housing of a lower end portion of a reactor bottom portion by using a welding torch, the reactor bottom portion including an inclined surface inclined relative to the stub tube, the method comprising:providing an apparatus for driving a welding torch, the apparatus including six control shafts including a pivot shaft for entirely pivoting the apparatus, an advance shaft for driving the welding torch in a radial direction, a vertical shaft for driving the welding torch in a vertical direction, an inclined drive shaft for driving the welding torch along an inclined angle between an inclined surface of a bottom head and a stub tube, a torch rotating shaft for continuously changing a torch direction from a stub tube side surface up to a bottom head, and a head rotating shaft for correcting the torch position shifted due to rotation of the inclined drive shaft;emitting a first heating laser beam to a cracked portion to remove moisture from the cracked portion;driving the welding torch by the apparatus including the six control shafts along the inclined surface of the lower end portion of the reactor bottom portion and the stub tube, and while driving the welding torch changing a direction of the welding torch from a side surface of the stub tube to the lower end portion of the reactor bottom surface;emitting from the welding torch a first welding laser beam following a portion to be welded to the lower end portion of the reactor bottom portion to form a welded portion, a position of the welding laser beam changing to follow the portion to be welded by a welding machine correcting a position of the welding torch shifted by rotation of a drive shaft of the welding torch; andemitting a second heating laser beam and a second welding laser beam to an entire surface of the stub tube and the welded portion between the stub tube and a bottom head to weld the surface of the stub tube to repair the crack on the stub tube surface and the crack on the surface between the lower end portion of the bottom head and the welded portion thereby preventing a new crack from occurring. 6. The reactor bottom repairing method of preventing leakage of reactor water according to claim 5, further comprising:covering the CRD housing with a cap-shaped member to cover the CRD housing from an upper end thereof up to an upper end surface of the stub tube, the cap-shaped member being made of a material having a shape not interfering with an overlay welded portion at a corner between the CRD housing and the stub tube thereinside, having an outside diameter substantially matching with that of the stub tube, and having a low stress corrosion cracking sensitivity;applying first laser seal welding to the stub tube in a lower end portion of the member; andapplying second laser seal welding to a side surface of the CRD housing in an upper portion thereof to thereby prevent reactor water from leaking from a welded portion between the CRD housing and the stub tube and a heat affected portion of the CRD housing. 7. The reactor bottom repairing method, according to claim 6, further comprising applying third laser seal welding between a lower end portion of the cap-shaped member and the stub tube, wherein preceding emitting the welding beam, an inert gas is sprayed to remove moisture from the melt portion to thereby prevent a moisture emitting at a welding period. 8. The reactor bottom repairing method, according to claim 6, further comprising applying third laser seal welding between an upper end portion of the cap-shaped member and the CRD housing, wherein preceding the welding beam radiation, an inert gas is sprayed to lower a water level of an inner portion of the cap-shaped member and to remove moisture from the melt portion to thereby prevent a moisture emitting event. 9. A reactor bottom repairing method of repairing a crack in a penetrating portion of a control rod drive (CRD) housing and a stub tube portion and preventing reactor water from leaking by a combination of an overlay welding of an entire surface of the stub tube and a surface of the welded portion of a lower end portion of a reactor bottom surface and a welding of a cap-shaped member to cover a welded portion between the CRD housing and the stub tube by using a welding torch, the reactor bottom portion including an inclined surface inclined relative to the stub tube:the overlay welding comprising:providing an apparatus for driving a welding torch, the apparatus including six control shafts including a pivot shaft for entirely pivoting the apparatus, an advance shaft for driving the welding torch in a radial direction, a vertical shaft for driving the welding torch in a vertical direction, an inclined drive shaft for driving the welding torch along an inclined angle between an inclined surface of a bottom head and a stub tube, a torch rotating shaft for continuously changing a torch direction from a stub tube side surface up to a bottom head, and a head rotating shaft for correcting the torch position shifted due to rotation of the inclined drive shaft;emitting a first heating laser beam to a cracked portion to remove moisture from the cracked portion;driving the welding torch by the apparatus including the six control shafts along the inclined surface of the lower end portion of the reactor bottom portion and the CRD housing, and while driving the welding torch changing a direction of the welding torch from a side surface of the CRD housing to the lower end portion of the reactor bottom surface;emitting from the welding torch a first welding laser beam following a portion to be welded to the lower end portion of the reactor bottom portion to form a welded portion, a position of the welding laser beam changing to follow the portion to be welded by a welding machine correcting a position of the welding torch shifted by rotation of a drive shaft of the welding torch; andemitting a second heating laser beam and a second welding laser beam to an entire surface of the cylindrical body inside the reactor and the welded portion between the cylindrical body and the lower end portion of the reactor bottom portion thereby preventing a new crack from occurring;the welding for the cap-shaped member comprising:covering the CRD housing with a cap-shaped member to cover the CRD housing from an upper end thereof up to an upper end surface of the stub tube, the cap-shaped member being made of a material having a shape not interfering with an overlay welded portion at a corner between the CRD housing and the stub tube thereinside, having an outside diameter substantially matching with that of the stub tube, and having a low stress corrosion cracking sensitivity;applying first laser seal welding to the stub tube in a lower end portion of the member; andapplying second laser seal welding to a side surface of the CRD housing in an upper portion thereof to thereby prevent reactor water from leaking from a welded portion between the CRD housing and the stub tube and a heat affected portion of the CRD housing.
053848136	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-5 show a storage rack 10 of the invention, which forms a close packed array 10, 3 rows by 5 columns of elongated cells C1-C15 in this embodiment, the odd numbered or primary cells C1, C3, C5, C7, C9, C11, C13, C15 are formed from rectangular cell housings 3 which extend along housing axes 3'. The even numbered or secondary cells C2, C4, C6, C8, C10, C12, C14 are formed by the walls of the surrounding cells. It is noted that the secondary cells along the perimeter of the array C2, C4, C6, C10, C12, C14 are not completely surrounded by primary cells. If it is necessary that one of these secondary cells is to be utilized, a stiffener wall 3A is inserted substantially flush with exterior walls of the adjacent primary cell housings to completely enclose the secondary cell as shown in FIG. 3. The individual cell housings 3 and the stiffener walls 3A are held in parallel alignment by upper and lower support bars 1, 7, and 8 which extend transverse to the longitudinal axis of the cell housings 3. The support bars 1, 7 and 8 are located between each of the rows of cells and along the perimeter of the array as shown in FIG. 5. Support bars 1, 7 and 8 are provided at both the top and bottom end portions of the rack. The cell housings are held in parallel alignment by welding the individual cell housings 3 to the upper and lower support bars 1, 7 and 8. The support bars also add strength to the upper and lower ends of the cell housings to resist damage during inserting and removal of the nuclear fuel rod assemblies. As shown in FIG. 2, a base plate 2 is welded to the bottom of the rack to close the bottom of the cells and support the nuclear fuel assemblies. The base plate 2 may also be provided with holes 12 at locations within each cell and pedestal feet 9 to facilitate the flow of water for enhanced cooling. Each cell housing 3 is an elongated tube having a rectangular cross section. The housing is constructed from suitable material, for example, .050 inch thick stainless steel tubing. Typically the tubes are square, approximately 81/2 inches along each side and 14 feet long. Each outer surface of the housing is planar, to which is applied, with a preload force, an elongated slab 4 constructed of a damping material. The damping material may also be a neutron absorbing material, such as borated stainless steel, borated aluminum, boral (such as manufactured by Brooks & Perkins, Minneapolis, Minnesota), or other neutron absorbing materials may be used. The damping material is preloaded against the outer surface by retainer clips 5, 5A, 5B which are welded to the outside of the housings along the perimeter of each surface. The retainer clips 5, 5A, 5B are composed from a flat plate of steel by forming an S-shaped bend which causes the plane of the raised edge portion 5C to be offset relative to the fixed edge portion 5D of the same surface. Preferably, the offset is the same size as the thickness of the slab 4. When retainer clips 5, 5A, 5B are plug or spot welded the housing 3, the weld shrinks and the clips are pulled tight against the housing thus preloading the elongated slab against the housing. The fixed edge portion 5D may be provided with holes to facilitate plug welding. Alternatively, the offset 5E may be less than the thickness of the damping material and therefore, when the fixed edge portion 5D is fixed to the housing 3, the raised edge portion 5C forces the damping material 4 against the outer surface of the housing. In this embodiment, the retainer clips may be fixed by welding as well as by rivets or threaded fasteners. As shown in FIG. 2, there are upper and lower horizontal retainer clips 5B attached at the upper and lower ends of each lateral surface of the cell housings. Also shown are vertical retainer clips 5 which are attached to the housings 3 along the vertical edges of the outer surfaces. As shown in FIG. 4, the vertical retainer clip 5 has a right angle bend 5' along its center and raised edge portions 5C on each side of the bend. This permits the vertical retainer clip 5 to preload the damping material on two adjacent surfaces of the housings 3. As shown in FIG. 4, the slabs 4 may be provided with recesses 4A along each edge. The depth of the recess 4A is preferably equal to the thickness of the retainer clip 5. The recess 4A permits the retainer clips 5 to be flush with the outer surface of the slab 4. This avoids damaging the retainer clips 5 during insertion and removal of the fuel assemblies. As shown in FIGS. 3 and 4, a stiffener wall 3A may be utilized to enclose the secondary cells (e.g., cell C4) along the perimeter of the array 10. The stiffener wall 3A is a U-shaped channel of the same material, length and thickness as the cell housing. It is of sufficient width to fill the space between two primary cells (e.g., cells C3 and C5). The outer surface of the stiffener wall 3A may have a damping slab 4 preloaded against it made of a material of a similar size and type of material preloaded against the walls of the cell housings 3. The slab 4 of damping material is preferably preloaded against the outer surface of the stiffener wall by horizontal retainer clips 5A along the upper and lower ends of the stiffener wall 3A and by vertical retainer clips 5B along the longitudinal edges of the stiffener wall 3A. In an alternate embodiment as shown in FIGS. 6 and 7, the retaining device is a cover plate 15 which extends over the entire housing surface. The cover plate 15 has a flange extending from each edge which is fixed to the housing 4. Each flange has a S-shaped bend which includes a sloped portion 15A and fixed portion 15B. After the fixed portion 15B is welded to the housing, the resulting weld shrinkage causes the sloped portion 15A to pull the cover plate 15 against the housing thus preloading the poison slab 4 against the outer surface. As shown in FIGS. 8-11, the invention may be embodied utilizing cells having different geometric cross-sections. By utilizing different cell geometries, the packing or spacing of nuclear fuel assemblies can be controlled to accommodate different system requirements. FIG. 8 shows an embodiment of the present invention utilizing cells of pentagonal cross-section. While the cells are shown in a circular array configuration, the cells may be arranged in other geometric or non-geometric configurations. FIGS. 9-11 show exemplary close packed arrays. FIG. 9 shows an embodiment of the present invention utilizing cells of triangular cross-section. In this embodiment, stiffener walls to enclose the outer cells 3A may also be provided. FIG. 10 shows an embodiment of the present invention utilizing cells of hexagonal cross-section. This configuration provides increased packing of the nuclear fuel assemblies and increased cell strength over rectangular configurations. FIG. 11 shows a modification of the embodiment of FIG. 10 wherein central cells A are formed by the walls of the adjacent surrounding cells B. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of the equivalency of the claims are therefore intended to be embraced therein.
	claims	1. A method of sample formation and imaging comprising:a) placing an object into a vacuum chamber;b) forming a sample from said object; andc) imaging said sample, wherein at least a portion of an electron beam traverses at least a portion of said sample, wherein said forming and imaging are carried out in said vacuum chamber. 2. The method of claim 1 wherein said object is penetrated to a depth of at most 10% of a thickness of said object during said stage of forming. 3. The method of claim 1 wherein said stage of forming includes a beam milling selected from the group consisting of ion beam milling and electron beam milling. 4. The method of claim 1 wherein said electron beam is incident substantially normally to an object cross section surface of said sample. 5. The method of claim 1 wherein said imaging includes imaging said object cross section surface. 6. The method of claim 1 wherein said sample is situated on a surface of said sample support such that an object cross section surface of said sample is substantially parallel to said surface of said sample support. 7. A method of sample formation and imaging comprising:a) providing an object in a vacuum chamber;b) forming a sample from the object inside said vacuum chamber;c) thinning at least a portion of the sample with an ion beam; andd) imaging the thinned sample, wherein at least a portion of said sample is subjected to a electron beam, wherein said thinning and imaging are repeated at least once while said sample is inside said vacuum chamber, thereby providing a plurality of images. 8. The method of claim 7 wherein said stage of forming includes a beam milling selected from the group consisting of ion beam milling and electron beam milling. 9. The method of claim 7 wherein said imaging includes imaging an object cross section surface of the sample. 10. The method of claim 7 wherein at least one said stage of imaging includes detecting photons. 11. The method of claim 7 wherein said thinning and imaging are repeated at least once until said at least a portion of said sample is eliminated by said thinning. 12. The method of claim 7 wherein said stage of thinning includes subjecting said sample to at least one ion beam selected from the group consisting of a focused ion beam and a beam of argon ions. 13. The method of claim 7 wherein said thinning includes selective removal of material. 14. The method of claim 7 wherein said thinning includes subjecting said sample to a particle beam incident substantially normally to said object cross section surface, said particle beam selected from the group consisting of an ion beam and electron beam.
	description	Referring to FIG. 1 is a schematic sectional view of one embodiment of an electron beam irradiating apparatus according to the present invention. The apparatus of the invention includes a chamber Cbin which a predetermined process takes place. The chamber CB has an opening at its top surface. A cathode plate CP, which in one embodiment is electrically insulated from the chamber CB, is installed over the opening. An insulating ring I is interposed between the cathode plate CP and the top of the chamber CB. The cathode plate CP may be a single cathode plate formed of a non-metal conductive material such as silicon, or a dual cathode plate having an upper cathode plate CP1 formed of a metal such as aluminum (Al) or an Al alloy, and a lower cathode plate CP2 formed of a non-metal conductive material such as silicon. The chamber CB is grounded. A grid plate GP is disposed beneath the cathode plate CP, and a gas injection ring GR is disposed below the grid plate GP. The gas injection ring GR has a doughnut shape as shown in FIG. 2. As shown in FIG. 2, the gas injection ring GR has a plurality of holes H along the inner circumference thereof, which allow a process gas, for example, an inert gas, to spray downwards and toward the center of the gas injection ring GR. In one embodiment, the grid plate GP is installed such that it is electrically insulated from the cathode plate CP and the chamber CB. The cathode plate CP is connected to a high voltage power source HVP while the grid plate GP is connected to a low voltage power source LVP. In particular, the positive terminal of the high voltage power source HVP is grounded and the negative terminal thereof is connected to the cathode plate CP. Thus, a high negative voltage, for example, a voltage of xe2x88x92500 to xe2x88x9230,000 volts, is applied to the cathode plate CP. Similarly, the positive terminal of the low voltage power source LVP is grounded while the negative terminal thereof is connected to the grid plate GP. Accordingly, a negative low voltage, for example, a voltage of 0 to xe2x88x92500 volts, is applied to the grid plate GP. A susceptor S is disposed on the bottom of the chamber CB, and a predetermined region of the bottom of the chamber CB is openeded to be connected to a vacuum pump P through a valve V interposed between the chamber CB and the vacuum pump P. The vacuum pump P maintains the pressure of the chamber CB at a lower pressure than the atmospheric pressure. In operation of the electron beam irradiating apparatus having the above structure, a wafer, on which a material layer such as a photoresist layer or an SOG layer has been deposited, is loaded onto the susceptor S. The inner pressure of the chamber CB is maintained at a predetermined pressure, for example, a low pressure of 1 to 200 mTorr, by the vacuum pump P and the valve V. Subsequently, a process gas, for example, an argon (Ar) or nitrogen (N2) gas, is injected into the chamber CB through the gas injection ring GR. At this time, a high negative voltage of about xe2x88x92500 to xe2x88x9230,000 volts is applied to the cathode plate CP by the high voltage power source HVP, while a low negative voltage of about 0 to xe2x88x92150 volts is applied to the grid plate CP by the low voltage power source LVP. Accordingly, the process gas injected into the chamber CB is ionized, so that positive and negative ions are produced, wherein the positive ions move toward the grid plate GP due to the electric field created by the low negative voltage applied to the grid plate GP. The positive ions that reach the grid plate GP are accelerated toward the cathode plate CP through the holes of the grid plate GP by the high negative voltage applied to the cathode plate CP. The accelerated positive ions hit the bottom surface of the cathode plate CP. As a consequence, secondary electrons are emitted from the cathode plate CP. Since the bottom surface of the cathode plate CP is formed of a non-metal conductive material, unlike a conventional case, emission of metal atoms from the cathode plate CP does not occur. The electrons emitted from the cathode plate CP are accelerated toward the wafer loaded onto the susceptor S by the electric field produced by the high and low negative voltages applied to the cathode plate CP and the grid plate GP, respectively. At this time, some electrons further ionize the process gas molecules which are present between the grid plate GP and the wafer, to thereby produce positive and negative ions. This allows continuous emission of the electrons from the cathode plate CP. With variations of the level of voltage applied to the grid and cathode plates, the number of electrons and the level of energy irradiated onto the wafer change. Thus, the wafer surface may be irradiated with an electron beam having a desired current density and energy by appropriate control of the grid voltage and cathode voltage. In the case where a photoresist layer is irradiated with the electron beam, the photoresist layer is cured by baking. When an SOG layer is irradiated with the electron beam, the SOG layer is also cured, wherein the cured SOG layer exhibits similar properties to those of a silicon oxide layer. For example, the dielectric constant and etch rate of the resulting cured SOG layer are similar to those of the silicon oxide layer. Also, by appropriately controlling an energy level of the electron beam irradiated onto the SOG layer, the thickness of the resulting cured SOG layer can be adjusted. For example, by appropriately controlling the electron beam irradiation conditions, a double-layered material film may be obtained. Each layer of the double-layered material film can be individually controlled and have different properties. For example, the double-layered film can include a non-cured SOG layer and a cured SOG layer. Since the electron beam irradiation is carried out at a low temperature of 200xc2x0 C. or less, diffusion of impurities that are implanted into the semiconductor wafer does not occur. Accordingly, a change in electrical properties of MOS transistors can be avoided. Also, when the wafer surface is irradiated with an electron beam by using the electron beam irradiating apparatus according to the present invention, the wafer can be prevented from contamination by metals, thus markedly improving the reliability of semiconductor devices. Thus, the electron beam irradiating apparatus according to the present invention is suitable for manufacturing highly integrated semiconductor devices with an increased requirement for low-temperature processing. FIGS. 3 through 6 are schematic sectional views illustrating a method of forming inter-metal dielectric (IMD) films of semiconductor devices by using the electron beam irradiating apparatus according to the present invention. For reference, the electron beam irradiating apparatus according to the present invention can be applied to forming general ILD films and baking photoresist layers, as well as to forming IMD films. By irradiating the wafer surface with an electron beam using the electron beam irradiating apparatus according to the present invention, the wafer surface can be protected from contamination by metal atoms. In addition, the electron beam irradiating apparatus according to the present invention permits low-temperature processes at a temperature of 200xc2x0 C. or less. In particular, referring to FIG. 3, an ILD film 3 is formed on a semiconductor substrate 1. Lower metal interconnections 5 are formed in predetermined regions of the ILD film 3. Then, a first capping insulation layer 7, for example, a plasma oxide layer, is formed on the metal interconnections 5 and the ILD films between the metal interconnections 5. A planarized SOG layer 9 is formed on the entire surface of the resultant structure having the first capping insulation layer 7. The planarized SOG layer 9 is formed by spinning a layer of liquid SOG on the first capping insulation layer 7. The planarized SOG layer 9 completely fills spaces between adjacent lower metal interconnections 5 and is in the form of a thin film on the top of each lower metal interconnection 5. Referring to FIG. 4, the surface of the planarized SOG layer 9 is irradiated with an electron beam E by using the electron beam irradiating apparatus of FIG. 1. At this time, the energy level is appropriately controlled to the extent that the thin SOG layer 9 on the top of the lower metal interconnections 5 is cured while the SOG layer 9 filling the spaces between the lower metal interconnections 5 is not cured. As a result, a cured SOG layer 9xe2x80x2 is formed to a predetermined thickness on the surface of the planarized SOG layer 9. The properties of the SOG layer 9 vary with a curing process. Thus, the cured SOG layer 9xe2x80x2 exhibits similar properties to those of silicon oxide layers. In particular, the initial SOG layer 9, which is not cured yet, has a low dielectric constant and a high etch rate, compared to those of the silicon oxide layers. Meanwhile, the dielectric constant and the etch rate of the cured SOG layer 9xe2x80x2 are nearly the same as those of the silicon oxide layers. In other words, it can be noted that as the SOG layer 9 is cured, the dielectric constant increases while the etch rate decreases. Referring to FIG. 5, a second capping insulation layer 11, for example, a plasma oxide layer, is formed on the cured SOG layer 9xe2x80x2. The second capping insulation layer 11, the cured SOG layer 9xe2x80x2 and the first capping insulation layer 7 are sequentially etched, to thereby form via holes 13 which expose a predetermined region of the lower metal interconnections 5. The etch rate of the cured SOG layer 9xe2x80x2 is nearly the same as that of the first and second capping insulation layers 7 and 11 formed of silicon oxide, such as plasma oxide, so that the vias 13 exhibit a normal sidewall profile. Also, since the uncured SOG layer 9 remains between the lower metal interconnections 5, parasitic capacitance between the lower metal interconnections 5 can be minimized. Referring to FIG. 6, a metal layer is deposited on the resultant structure having the vias 13, filling the vias 13. Then, the metal layer is patterned to form upper metal interconnections 15 which fill the vias 13. As described above, the electron beam irradiating apparatus according to the present invention can effectively suppress emission of metal atoms from the cathode plate. Thus, during electron beam irradiation onto the SOG layer or the photoresist layer, the semiconductor wafer can be protected from contamination by the metal atoms, thus producing semiconductor devices with stabilized electrical properties and reliability. While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
046684646	description	EXAMPLE The above has been applied to a three-period, helical axis stellarator. This stellarator has a relatively large rotational transform which implies a relative small finite .beta. magnetic axis shift. The value of .chi. increases from slightly above 1.5 at the magnetic axis to about 1.7 at the edge. The axis shifts halfway to the outer flux surface at a .beta. of about 15%. The .delta..sub.nm.sup.v for a general vacuum field should decrease rapidly in amplitude as n or m increases. This is borne out for this heliac by a numerical Fourier decomposition of the vacuum field. The largest components correspond to (n,m)=(3,0), (0,1), and (3,1). Of course, n must be a multiple of 3 because of the periodicity. The .delta..sub.30 component corresponds to the field ripple on the magnetic axis. It is very nearly equal to 2r.sub.o /R=0.5, where r.sub.o is the radius of the helix formed by the magnetic axis and R is the major radius. The .delta..sub.01 term, which is due to the toroidal curvature, is about 2.5.rho./R, where .rho. is taken to be the circularized flux surface radius. The helical curvature gives the .sub.31 term, which has a value of about .delta..sub.31 =1.3.rho./r.sub.ch, where r.sub.ch is the helical radius of curvature of the magnetic axis, r.sub.ch =(1+k.sup.2 r.sub.o.sup.2)/(k.sup.2 r.sub.o 0), (2.pi./k is the periodicity length). The decrease of .delta..sub.nm.sup.v with increasing (n,m) implies that the most dangerous direct resonances are those with low n and m. Higher order resonances are due to coupling of the .delta..sub.nm.sup.v. The coupling is strongest for resonance with low n and m. So here again the low order resonances are the most dangerous. For this heliac, the most serious problem is posed by the n=3, m=2 resonance, which lies at the magnetic axis. (The transform at the axis is actually very slightly above 1.5. It is convenient for the following discussion to take .chi. there as 1.5 exactly, which has only a small effect on the results.) The radial m=2 component of the plasma field goes to zero at the axis; but d.chi./d.sub..rho. also vanishes there, so that the island width can nonetheless be finite. It is necessary to modify Eqs. (7) and (8) to take into account the vanishing d.chi./d.sub..rho.. Specializing to n=3, m=2, we estimate ##EQU5## where .DELTA..chi. is the change in .chi. across the minor radius, a. We obtain ##EQU6## This is the required modification of Eq. (8). The .delta..sub.31.sup.v and .delta..sub.01.sup.v components couple directly to give a nonlinear .delta..sub.32 component. The corresponding island width is equal to half the minor radius at .beta..sub.o .perspectiveto.0.017. The .delta..sub.31.sup.v and .delta..sub.01.sup.v Fourier components are intrinsic to the heliac vacuum field, and can be eliminated by the use of a helical equilibrium coil whose current is adjusted as a function of .beta. to suppress the resonant n=3, m=2 part of the equilibrium field. A few helical equilibrium coils would suffice to suppress the islands at the low order rational surfaces. In the general design of stellarator vacuum fields, we might have expected the requirement of good vacuum flux surfaces to suppress the resonant field amplitudes. Our calculation for the heliac reference design shows that the amplitudes of the direct resonances may nonetheless be unacceptably large. We conclude that it is necessary to incorporate the constraints on the resonant .delta..sub.nm.sup.v directly in the design procedures. Our application also shows that coupling of nonresonant components can give large islands, even for values of .beta. at which the axis shift is small relative to the minor radius. In summary, we have proposed the use of resonant coil systems, such as helical coils, carrying relatively small currents. The required current in the coils is determined by the plasma pressure, as given by equations (8) and (10). Initially the current is zero, to avoid the deleterious effect on the vacuum field. As the plasma pressure is raised, the current in the resonant coils must also be raised. The final current in these coils is typically 1% of that in the stellarator primary coils.
	claims	1. An electron beam device for directing a beam of energetic electrons onto a substrate for forming an integrated circuit pattern on the substrate, said electron beam device comprising: a source of energetic electrons for directing a beam of electrons along an axis; multi-stage beam limiting means disposed in a spaced manner along said axis adjacent said source of energetic electrons for intercepting a peripheral portion of the electron beam and reducing the cross section of the electron beam, wherein each stage of said beam limiting means incrementally reduces the cross section of the electron beam in proceeding toward the substrate; focusing means disposed along said axis intermediate said beam limiting means and the substrate for forming a beam electrostatic focus region in the electron beam device for focusing the electron beam to a spot on the substrate; and multi-stage electrostatic deflection means disposed in a spaced manner along said axis intermediate said beam limiting means and the substrate and generally co-located with said focusing means for forming a beam electrostatic deflection region for deflecting the electron beam over the substrate in forming a circuit pattern on the substrate, wherein said beam electrostatic focus region and said beam electrostatic deflection region overlap and are coincident along said axis, and wherein each stage of said electrostatic deflection means has a different incremental deflection sensitivity for exerting increasing incremental deflection sensitivity on the electron beam in proceeding toward the substrate. 2. The electron beam device of claim 1 wherein said source of energetic electrons comprises an electron gun. claim 1 3. The electron beam device of claim 1 wherein said multi-stage beam limiting means includes plural, apertured plates disposed in a spaced manner along said axis, and wherein the apertures in said plates are aligned along said axis and said beam of electrons is directed through the aligned apertures. claim 1 4. The electron beam device of claim 3 wherein each of said apertures is circular and said apertures decrease in size in proceeding along said axis in the direction of travel of the beam. claim 3 5. The electron beam device of claim 4 wherein each of said plates has a respective thickness, with the thickness of said plates decreasing along said axis in the direction of travel of the beam. claim 4 6. The electron beam device of claim 5 wherein said multi-stage beam limiting means comprises first, second and third generally flat apertured plates having thicknesses t 1 , t 2 , and t 3 , respectively, and apertures having diameters d 1 , d 2 , and d 3 , respectively, and wherein said first plate is in facing relation to said source of energetic electrons and said second plate is disposed intermediate said first and third plates, and wherein t 1 greater than t 2 greater than t 3 and d 1 greater than d 2 greater than d 3 . claim 5 7. The electron beam device of claim 3 further comprising electrostatic beam positioning means disposed adjacent said plates for centering the electron beam in the apertures of said plates. claim 3 8. The electron beam device of claim 7 wherein said electrostatic beam positioning means included plural electrostatically charged electrodes each aligned along said axis and disposed intermediate adjacent apertured plates. claim 7 9. The electron beam device of claim 8 wherein each of said electrostatically charged electrodes includes plural charged members disposed in a spaced manner concentrically about said axis, and wherein each of said charged members is equidistant from said axis. claim 8 10. The electron beam device of claim 9 wherein each of said plural members of an electrostatically charged electrode is connected to a respective voltage source. claim 9 11. The electron beam device of claim 10 wherein each voltage source is adjustable for providing selected voltages to the plural members of an electrostatically charged electrode. claim 10 12. The electron beam device of claim 10 wherein each electrode includes four members, and wherein a first pair of charged members diametrically disposed with respect to said axis center the electron beam in a first direction and a second pair of charged members diametrically disposed with respect to said axis center the electron beam in a second direction, and wherein said first and second directions are transverse. claim 10 13. The electron beam device of claim 1 wherein said beam limiting means includes an apertured plate disposed in a spaced manner along said axis, said plate including a tapered aperture through which said beam of electrons is directed, said tapered aperture defined by a larger opening on a first side of said plate in facing relation to said source of energetic electrons and a smaller opening on a second, opposed side of said plate in facing relation to said focusing means. claim 1 14. The electron beam device of claim 13 wherein said plate is comprised of platinum. claim 13 15. The electron beam device of claim 1 wherein said multi-stage electrostatic deflection means includes plural sets of deflection plates disposed in a spaced manner about said axis, and wherein said sets of deflection plates are disposed in a spaced manner along said axis. claim 1 16. The electron beam device of claim 15 wherein each of said deflection plates is generally flat and is disposed lengthwise along said axis. claim 15 17. The electron beam device of claim 16 wherein each deflection plate has first and second opposed ends respectively disposed in facing relation to said beam limiting means and to said substrate, and wherein the first end of each of said plates is disposed closer to said axis than the second opposed end of the plate. claim 16 18. The electron beam device of claim 17 wherein each of said deflection plates is generally trapezoidal in shape and said first end is parallel to and shorter than said second opposed end. claim 17 19. The electron beam device of claim 15 wherein each set of deflection plates includes four deflection plates, and wherein a first pair of deflection plates diametrically disposed with respect to said axis deflect the electron beam in a first direction and a second pair of deflection plates diametrically disposed with respect to said axis deflect the electron beam in a second direction, and wherein said first and second directions are transverse. claim 15 20. The electron beam device of claim 15 wherein each of said deflection plates is connected to a respective dynamic voltage source. claim 15 21. The electron beam device of claim 15 including a first set of deflection plates disposed in facing relation to said beam limiting means for coarse deflection of the electron beam and a second set of deflection plates disposed between said first set of deflection plates and said substrate for fine deflection of the electron beam. claim 15 22. The electron beam device of claim 21 wherein said first set of deflection plates are connected to a first dynamic voltage source and said second set of deflection plates are connected to a second dynamic voltage source. claim 21 23. The electron beam device of claim 1 wherein said focusing means includes first and second focusing electrodes disposed along said axis on respective sides of said electrostatic deflection means, and wherein said first focusing electrode is in facing relation to said beam limiting means and said second focusing electrode is in facing relation to the substrate. claim 1 24. The electron beam device of claim 23 wherein said first and second focusing electrodes are generally cylindrical in shape and are concentrically disposed about said axis. claim 23 25. The electron beam device of claim 23 wherein said second focusing electrode includes plural charged lens elements disposed in a spaced manner about said axis. claim 23 26. The electron beam device of claim 25 wherein each of said lens elements is a generally flat plate connected to a respective voltage source, and wherein each of said flat plates is aligned generally parallel to said axis. claim 25 27. The electron beam device of claim 26 wherein said second focusing electrode includes four generally flat charged lens elements, and wherein a first pair of lens elements are diametrically disposed relative to one another with respect to said axis and a second pair of lens elements are diametrically disposed relative to one another with respect to said axis. claim 26 28. The electron beam device of claim 27 wherein said first focusing electrode is generally cylindrical in shape and is concentrically disposed about said axis. claim 27 29. The electron beam device of claim 1 further comprising an envelope substantially disposed about said source of energetic electrons, said beam limiting means, said focusing means, and said electrostatic deflection means. claim 1 30. The electron beam device of claim 29 wherein said envelope is comprised of glass. claim 29 31. The electron beam device of claim 29 wherein said envelope is conductive. claim 29 32. An arrangement for simultaneously forming plural electronic circuit patterns of an integrated circuit, said arrangement comprising: first plural electron beam devices arranged in a generally planar, matrix array, wherein each electron beam device has a respective longitudinal axis along which a respective electron beam emitted by the electron beam device is directed, and wherein the longitudinal axes of said electron beam devices are in parallel alignment; one or more first substrate members disposed in spaced relation from said electron beam devices along the longitudinal axes of said electron beam devices, wherein each electron beam is directed onto a single substrate member or wherein each electron beam is directed onto a respective substrate member; and means for supporting and displacing said electron beam devices, wherein each of said electron beams forms an electronic circuit pattern on said single substrate member or on a respective one of said plural substrate members. 33. The arrangement of claim 32 further comprising second plural electron beam devices arranged in generally planar, matrix array for directing their respective electron beams onto one or more second substrates, and means for supporting and displacing said second plural electron beam devices for forming second electronic circuit patterns on said one or more second substrates, wherein said first and second plural electron beam arrays are arranged in a stacked manner. claim 32 34. The arrangement of claim 32 wherein each of said electron beam devices is connected to a common control circuit for energizing and controlling said electron beam devices. claim 32
	claims	1. A diagnostic resonant cavity for use in determining characteristics of a charged particle beam traveling along a beam line of a charged particle accelerator, comprising two electrically conductive opposing end walls spaced apart from one another by an electrically conductive tubular wall, said end walls having openings centered therein for interposition of the cavity in the beam line by connection of said end walls to a beam tube having a central longitudinal axis defining the nominal path of travel of the charged particle beam, and an even plurality of at least four pairs of electrically conductive rods extending into said cavity from said end walls, each of said pairs of rods consisting of two rods extending inwardly and coaxially toward one another from said two opposing end walls and extending parallel to said central longitudinal axis said of said beam tube, said two rods of each pair of opposing rods being spaced from one another so as to form a capacitative gap between one another, and wherein said pairs of rods are equally spaced azimuthally in a symmetrical array around said central longitudinal axis of said beam tube. 2. The diagnostic resonant cavity defined in claim 1 wherein said end walls are each substantially planar and extend parallel to one another. 3. The diagnostic resonant cavity defined in claim 2 wherein said end walls are each orthogonal to said central longitudinal axis of said beam tube. 4. The diagnostic resonant cavity defined in claim 3 wherein said tubular wall of said diagnostic resonant cavity is cylindrical. 5. The diagnostic resonant cavity defined in claim 4 wherein said rods extend from said end walls from points contiguous to said openings in said end walls. 6. The diagnostic resonant cavity defined in claim 5 wherein said rods extend tangentially to said openings in said end walls. 7. The diagnostic resonant cavity defined in claim 6 comprising four pairs of rods to enhance the shunt impedance of the quadrupole resonant mode of the cavity. 8. The diagnostic resonant cavity defined in claim 6 comprising, six pairs of rods to enhance the shunt impedance of the sextupole resonant mode of the cavity. 9. The diagnostic resonant cavity defined in claim 1 comprising four pairs of rods to enhance the shunt impedance of the quadrupole resonant mode of the cavity. 10. The diagnostic resonant cavity defined in claim 1 comprising six pairs of rods to enhance the shunt impedance of the sextupole resonant mode of the cavity. 11. A diagnostic resonant cavity for use in determining characteristics of a charged particle beam traveling along a beam line of a charged particle accelerator, comprising first and second electrically conductive opposing end walls spaced apart from one another by an electrically conductive tubular wall, said end walls having openings centered therein for interposition of the cavity in the beam line by connection of said end walls to a beam tube having a central longitudinal axis defining the nominal path of travel of the charged particle beam, and an even plurality of at least four electrically conductive rods extending into said cavity from said first end wall, each of said rods extending inwardly in a direction parallel to said central longitudinal axis said of said beam tube, and each of said rods having an end distal from said first end wall, said distal end of each rod being spaced from said second end wall so as to form a capacitative gap between the rod and said second end wall, and wherein said rods are equally spaced azimuthally in a symmetrical array around said central longitudinal axis of said beam tube. 12. The diagnostic resonant cavity defined in claim 11 wherein each of said rods extends a distance greater than the major length of said cavity along said axis of said beam tube. 13. The diagnostic resonant cavity defined in claim 12 wherein said tubular wall of said cavity is cylindrical in cross section. 14. The diagnostic resonant cavity defined in claim 13 comprising four rods to enhance the shunt impedance of the quadrupole resonant mode of the cavity. 15. The diagnostic resonant cavity defined in claim 13 comprising six rods to enhance the shunt impedance of the sextupole resonant mode of the cavity. 16. The diagnostic resonant cavity defined in claim 11 wherein said rods extend tangentially to said openings in said end walls.
047132124	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 represents a schematic of a nuclear installation. An enclosure 1 protects a reactor 2 and a reactor pool 3. The reactor 2 comprises a core 4 situated at the interior of a vat 5. A loading canal 6 connects the reactor 2 to the reactor pool 3. The reactor pool 3 and the reactor 2 are supplied by a reactor pool loading machine 7 movable on rails 8. The loading machine 7 comprises a bridge 9 upon which is displaced a carriage 10. The carriage 10 comprises a telescopic mast 11 provided with sensors on the extremity serving to hook onto the core assemblies 4 of the reactor 2. In the reactor pool 3 is found a stockpile or storage rack 12 which is used to temporarily position the groups to be exchanged in the core of the reactor. A transfer tube 13 assures the connection between the reactor pool 3 and the deactivation pool 14 in which is found a storage rack 15. The deactivation pool 14 is served by a deactivation pool handling machine 16 which is movable on the rail 17. In the example represented in FIG. 1, the handling machine 16 comprises a bridge 18 upon which is moved a carriage 19. The carriage 19 also includes a telescopic mast 20 provided with sensors at the end for manipulating the groups. The transfer tube 13 is served by a transfer machine 21 comprising a transfer basket 22 and an apparatus which swings horizontally for placing the load on a carriage 23 for movement along the rails 24. The function of this transfer machine 21 is to proceed with a transport of the individual group between the reactor pool 13 and the deactivation pool 14. FIGS. 1 and 2 allow us to schematically follow a first example of manipulations. Assume that in the course of a charging sequence for a group A35, having coordinates 6D situated in the core 4 of the reactor, is to be transferred to the deactivation pool 14 for being replaced by another group C12 of coordinates 7P. The site of the coordinates 7P being itself occupied afterwards by a fresh group D41. For carrying out these manipulations, the unloading machine 7 first of all extracts the group A35 for placing it in the basket 22 of the transfer machine 21. After dumping the basket 22 the carriage 23 transfers the basket charged with the assembly A35 from the reactor pool 3 to the spent fuel pit 14. The handling machine 16 takes the group A35 out of the transfer basket 22 for placing it into a free space in the storage rack 15, for example in NL22. The loading machine 7 then extracts the group C12 from its location, at coordinates 7P, and places it at the location which has become free at coordinates 6D. Thereafter, the handling machine 16 takes the fresh group D41 from the storage rack 15 and places it in the transfer basket 22. Next, the transfer machine 21 brings the group D41 into the reactor pool 3. The loading machine 7 extracts then the group D41 from the transfer basket 22 and places it in the core 4 at the site of coordinates 7P. Upon the manipulation of the sets may be superposed a manipulation of components such as control rods or sets of plugs effectuated with the aid of a movable deposit station situated in the reactor pool 3. In the control process generally utilized in nuclear power plants, each manipulation constitutes one step in a loading sequence recorded in a loading listing which starts up, one by one, a sequence of pre-established administrative orders upon which an officer notes the beginning and ending times of the manipulation and validates the operation by his signature. This control only bears upon recorded administrative orders in the loading listing. Good execution of the manipulations rests upon the scrupulous execution of the administrative orders. At this level, therefore, can creep in manipulation errors owing either to a poorly worded administrative order, or an order poorly executed by the operator, or a faulty execution by the machine in spite of a well executed command by the operator. All of these errors are radically eliminated in the process according to the claimed invention. As represented in FIG. 4, assuming the reactor enclosure has a system of axes x.sub.1i, y.sub.1i permitting the placement with precision of the groups in the reactor 2, in the buffer rack 12, in the transfer basket 22 and in all other auxiliary apparatus equipping the reactor pool 3, such as a movable settling station 25 used for making exchanges of components in the midst of certain groups, or a fixed settling station 26 used for eliquation tests for detecting unexpected damage in a group on the rods forming the group. Assuming that the spent fuel pit 14 has another system of axes x.sub.2i, y.sub.2i, permitting placement with precision of the groups in the storage rack 15 and in the transfer basket 22, when the latter is located effectively in the spent fuel pit 14. The coordinates x.sub.1i, y.sub.1i, and x.sub.2i, y.sub.2i, which permit establishment of localization in the plan, are completed by the coordinates z which are situated on the depth of the groups, the handling heads of the loading machine 7 and the handling machine 16 and a camera perch, not shown, utilized for identifying the groups. These position coordinates x, y, z are provided by the codes given to the absolute position, independently of any interruption of current occurring at the installation. The codes are for example optical codes carried along without slippage by an appropriate mechanical apparatus. We have thus in x.sub.1i, y.sub.1i, z.sub.1i, the coordinates of placement of the groups in the core 2, the buffer rack 12, and the fixed resting station 26 which are the fixed coordinates, whereas the coordinates of the mobile resting station 25, the transfer basket 22, and the dams positioned, for example, in the recharging canal 6 are the variable parameters. In the same way as x.sub.2i, y.sub.2i, z.sub.2i, the coordinates of the storage rack 15 are fixed while the coordinates of the transfer basket 22 are variable parameters. We can designate by x.sub.1, y.sub.1, z.sub.1, the position of the gripping head of the loading machine 7, and by x.sub.2, y.sub.2, z.sub.2 the position of the gripping head of the handling machine 16. The signals corresponding to the coordinates x, y, z are sent to an information processor 30 charged with their management. Moreover, the information processor 30 receives information on the speed of displacement dx/dt, dy/dt, dz/dt, and the orientation .theta. of the gripping heads of the loading machine 7 and the handling machine 16, on the charge P and degree of opening F of the tongs of these machines. Also communicated to the information processor 30 are the identification marks of the groups, the loading plans, and the loading sequence. All of this information is not treated in the same manner. For that, it is necessary to distinguish in the information processor 30 a unit of treatment 31 charged with recognizing and treating the signals x.sub.1, y.sub.1, z.sub.1, dx/dt.sub.1, dy/dt.sub.1, dz/dt.sub.1, .theta..sub.1, P.sub.1, F.sub.1 characterizing the handling head of the loading machine 7 and the signals x.sub.2i, y.sub.2i, z.sub.2i, dx/dt.sub.2, dy/dt.sub.2, dz/dt.sub.2 .theta..sub.2, P.sub.2, F.sub.2 characterizing the gripping head of the handling machine 16. The fixed coordinates x.sub.1i, y.sub.1i, z.sub.1i of the locations for these groups in the core 2, the buffer rack 12, and the fixed resting station 26 of the reactor pool 3 are permanently registered in a permanent memory unit 32. The permanent memory unit 32 also receives fixed coordinates x.sub.2i, y.sub.2i, z.sub.2i of the storage rack 15 of the spent fuel pit 14. By contrast, the coordinates of the movable resting station 25, the transfer basket 22, the dams of the reactor pool 3, as well as the identification marks of the groups and their position occupied in the core 2 and in the storage racks 15 are registered in a temporary manner in a temporary memory unit 33. At the time of the first loading, there takes place for the first initiation the recordation of the coordinates of all of the sites provided for these groups, as well as the initial position and the identification of each group and the introduction of these values into the memory units 32 and 33. As for the loading sequence, there is furnished a programmable unit 34. The signals treated in the different units 31, 32, 33 and 34, which constitute the information processor 30, are then transmitted to a central calculating unit 35 which is connected with a conversational system 36. Upon unfolding of the loading sequence, each executed step is registered in a control box 37 which serves as a reference as well as a specialized organism charged with the surveillance of the fuel in the power plant, as well as for the personnel of the power plant for proceeding with verifications or controls of manipulation. At each instant the central calculating unit 35 compares the values furnished by the permanent memory unit 32, by the temporary memory unit 33, and by the programmable unit 34 with the values issuing from the treatment unit 31 for determining the ways of displacement of the handling heads of the machines 7 and 16 while taking into consideration permanent and temporary obstacles. In addition, while comparing the values furnished by the temporary memory unit 33 and by the permanent memory unit 32 to those values furnished by the programmable unit 34, the central calculating unit 35 may, according to the result of the comparison, authorize or refuse the step of the sequence engaged, and place into memory all valid calculations at the time in the temporary memory unit 33, and in the conversational system 36, for taking into consideration the evolution of the loading sequence. The central calculating unit 35 establishes at each instant a comparison between the researched position and the actual position of the manipulated group. If for example, the central calculating unit 35 verifies that the handling machine 16 is at the point of lowering a group into an erroneous site, the central calculating unit 35 sends a negative signal which annuls the requested order. That is translated by an alarm and eventually by a blockage of the lowering movement in such a manner as to avoid serious consequences resulting, for example, from the resting of a second group on a first already in place swinging the second group and risking destruction of the groups. This new process offers the advantage of recording the actual movements of the loading machine 7 and of the handling machine 16. It stores the actual successive positions occupied by the groups in their pools and the reactor, and not the desired positions in a sequence of administrative orders. In other words, the preestablished sequence furnishes to the programmable unit 34 and transmitted to the central calculating unit 35 permits making a blank test, that is, a simulation of the preestablished loading sequence, in order to verify if it will effectively lead to the specified charging plan. This characteristic clearly represents a significant advantage for operators of nuclear power plants. The orders admitted by the central calculating unit 35 are memorized in two different manners. A first memory called a control box 37 faithfully registers all of the movements executed in order to permit, in the event it is needed, the making of a detailed analysis of the different operations. A second memory installed in the temporary memory unit 33 is conceived for remembering the last position achieved by each group while erasing the previously occupied positions. In this manner, at the end of a loading sequence, it gives the new loading plan effectively achieved while reproducing exactly the placement and identification of each group in the core and in the storage rack 15. Obtained on the basis of control of operations which have been effectively executed, the new loading plan gives a total guarantee of the exactitude of the configuration. A summary of this aforementioned process in flowchart form is shown in FIG. 5. In the conversational system 36, there is at one's disposal video screens and keyboards for the introduction of given information in order to permit: dialogue between operating personnel and the information processor 30; PA1 visualization of orders for execution of movement; evolution, at any moment, of the loading plan giving the place and the identification of all of the groups, in order to know in the example being negotiated, in the core 2, in the buffer rack 12, in the mobile resting station 25, in the basket 22, in the fixed resting station 26, in the stockpile rack 15; PA1 the visualization of the schematic of each pool giving the position of obstacles, of handling heads, and even the way of displacing the gripping heads; the introduction in the loading sequence, furnished previously to the programmable unit 34, of a modification of the sequence in order to respond to a new need. In a more advanced system, one can achieve an entirely automatic loading operation. It is sufficient to bring under control the motorizing of machines in the preestablished sequence. The automatic operation can involve the choice and the execution of the most appropriate routes for movement of the gripping heads of the machines 7 and 16.
	description	The present invention is a process applied to graphite materials previously used as the moderator in the core of a thermal nuclear reactor and which are no longer required for this purpose. It also applies to any other graphite materials (fuel element sleeves, braces etc.) irradiated in the neutron flux of a nuclear reactor core. In a preferred embodiment, the present invention provides a process including the following steps: (i) reacting the radioactive graphite with superheated steam or gases containing water vapor to form hydrogen and carbon monoxide; (ii) reacting the hydrogen and carbon monoxide from step (i) to form water and carbon dioxide; (iii) reacting the carbon dioxide from step (ii) with a magnesium or calcium oxide to form magnesium or calcium carbonate; and (iv) processing of radioactive contaminants. In step (i) of the process of the present invention, the reaction of superheated steam or gases containing water vapor with graphite is carried out at a temperature within the range of 250xc2x0 to 900xc2x0 C., preferably between 600xc2x0 to 700xc2x0 C., to form hydrogen and carbon monoxide. This type of process is generally referred to in the art as xe2x80x9csteam reformingxe2x80x9d. The reaction in step (i) may be carried out with the addition of oxygen to the steam or gases containing water vapor to provide exothermic reaction energy for the process. The addition of oxygen also enables the temperature of the steam reforming reaction to be controlled. The gases from step (i) are then further oxidized in step (ii) with oxygen to form carbon dioxide and water. During the process, the gases are retained in an enclosed vessel under an inert atmosphere. In the preferred embodiment, the carbon dioxide and water are disposed of in a third step including the chemical processing of the carbon dioxide to create a suitable solid waste form for disposal. Preferably, the carbon dioxide is reacted with magnesium or calcium oxides to produce insoluble magnesium or calcium carbonate salts. Alternatively, the carbon dioxide and water which are produced in the process may be disposed of subsequently by a number of procedures including the following: (1) controlled discharge of the carbon dioxide to the atmosphere, after further processing necessary to minimize its radioactive content; (2) compression and liquification of the carbon dioxide for temporary storage, processing transportation or disposal; (3) condensation of steam to provide water for treatment, disposal or release. Finally, in the fourth step of the process of the present invention, the remaining radioactive contaminants contained in the radioactive graphite are processed. The process of the present invention may be carried out either within the containment a decommissioned nuclear reactor or may be applied (in externally provided equipment) off site. Radioactive secondary waste from the process of the invention or from further processing of the carbon dioxide produced in the process prior to discharge, can be dealt with in any conventional manner appropriate to normal procedures of the nuclear plant concerned. In-situ processing of graphite requires that the graphite in the nuclear reactor containment be subjected to conditions suitable for the gasification of graphite. The in-situ reactions can be performed by various methods, as discussed below. In a first method, carbon dioxide, nitrogen or other inert gas maybe recirculated through the reactor containment using normal in-plant equipment with the addition of small, controlled amounts of steam and/or oxygen, when required. A side stream is continuously extracted from the loop for the removal of carbon monoxide, hydrogen, and carbon dioxide. To mitigate the potential of a hydrogen explosion a catalytic hydrogen converter is preferably inserted in the treatment loop to convert any hydrogen to water. This option requires the injection of a small amount of oxygen into the catalytic converter. For the addition of trace amounts of oxygen, the reactor circuit is maintained above 250xc2x0 C. for oxidation reactions to proceed in sufficient time to allow the use of less than 5% oxygen concentration in the recirculating gases. The use of restricted oxygen levels is recommended to eliminate potential explosion reactions. For the addition of steam, the reactor circuit is maintained above 350xc2x0 C. for the reformation reactions to proceed at reasonable rates. In a second method, gases are injected into and removed from the nuclear reactor containment without the use of other in-plant equipment. This method involves the isolation of the graphite moderator from the balance of plant systems. An external gas recirculation loop can be utilized to inject gases into the nuclear reactor containment and provide removal of gaseous reaction products. Selected areas of the reactor containment can be maintained at high temperature by the injection of superheated gases at 400xc2x0 to 900xc2x0 C., or by the generation of the needed heat inside the reactor containment. Heat generation inside the reactor containment can be achieved by the insertion of electrical or combustion tube heaters placed in one or more of the fuel channels. The in-situ reaction utilizing this method allows the preferential removal of the graphite in selected areas of the nuclear reactor in order to remove graphite in a planned sequence. This feature is an extremely valuable safety mechanism, because it allows the graphite to be removed in a structurally secure manner, avoiding the possibility of collapse of a weakened moderator structure during the later stages of removal. The feasibility of local removal of graphite by this method is further aided by the decreased thermal conductivity of graphite in end-of-life moderators, which occurs as a result of neutron irradiation. It is estimated that over 75% of the graphite could be removed this way. The injected gases may consist of an inert gas and steam, together with oxygen, as required. Final removal of the last traces of graphite could, for example, be achieved by reverting to the previous method discussed above. When the process of the present invention is carried out on pieces or particles of the graphite which have been removed from the reactor core, the process may be carried out as a continuous, semi-continuous or batch process. The process may be carried out using a stationary bed formed from the graphite particles or pieces or, alternatively in a fluidized bed reactor. Preferably, the bed will be fluidized using the steam reactant as the fluidization aid, but it will be appreciated that the reactant bed may be fluidized using an inert gas, such as nitrogen or carbon dioxide, with the appropriate injection of steam and/or oxygen, to enable the reaction to proceed. Inert bed material can be utilized in the fluid bed to stabilize the temperature where steam and/or oxygen is injected into the vessel. The steam reforming reaction proceeds according to the equation: C+H2Oxe2x86x92CO+H2 In the second stage of the process of the present invention the carbon monoxide and the hydrogen are oxidized to carbon dioxide and water. This is generally carried out using oxygen gas as the oxidizing agent. The oxidation reaction may be carried out in the same vessel as, or a different vessel from, that in which the steam reforming reaction is carried out. For example, when the steam reforming reaction is carried out in a fluidized bed reactor, the oxygen may be introduced into the upper portion of the fluidized bed reactor, so that both steps of the process are carried out in a single reactor vessel. The advantage of the process of the present invention, as compared to the combustion of radioactive graphite, is that it can be carried out under appropriately controlled containment conditions. The loss of hazardous or radioactive materials in the off-gas is therefore reduced or even eliminated. Another significant benefit is the low volume of off-gas that simplifies handling including the possibility of achieving substantially zero gaseous emissions. Further, the process enables the Wigner energy stored in the radioactive graphite to be released in a controlled manner. The present invention will be further described with reference to FIG. 1 of the accompanying drawings which is an overview flow diagram of one means of carrying out the process of the present invention. Referring to the drawing, radioactive graphite is remotely removed from a nuclear reactor core by means of water jet or mechanical cutters. Graphite pieces and water are introduced into a size reduction wet grinder 1 where the graphite is reduced to less than 1.0 cm size. The size-reduced graphite is then mixed with water in vessel 2 and the slurry is fed directly into the fluidized bed reformer 4 by means of a slurry injector pump 3, without any other pre-treatment or handling required. Alternatively, graphite can be size reduced to less than 12.0 cm, preferably less than 4.0 cm for direct injection into the reformer 4 by means of a mechanical screw conveyor 5. The fluidized bed reformer 4 serves to evaporate all water from the graphite slurry and other liquid waste feeds and to pyrolyze any organic components through destructive distillation (pyrolysis). Energy needed to evaporate the feed water and drive the endothermic reformation process is provided by operating the fluid bed in an autothermal steam reforming mode. The off-gas from the reformer 4, which leaves the reformer along line 7, contains fine particulates, including most radionuclides and non-volatile inorganic materials, such as silica and calcium and gaseous components such as steam, carbon dioxide and gaseous radionuclides, particularly tritium, carbon-14 and iodine. The solid residue is elutriated from the reformer 4 by the fluidizing steam and gases. The particulates in the off-gas from the reformer are removed from the off-gas stream by a high temperature filter or wet scrubber 8. If only graphite is to be processed by the process, a high temperature particulate filter is all that is needed to clean all non-volatile radionuclides from the off-gas. If other streams are being processed, the wet scrubber is utilized as shown in FIG. 1. Table 1 provides a list of typical radionuclides found in moderator graphite and how the radionuclides found in moderator graphite and how the radionuclides are partitioned in the process of the present invention Utilization of the wet scrubber 8 cleans the off-gas by removing particles elutriated from the reformer 4 and neutralizes any potential acid gases. The scrubber solution is concentrated by the hot off-gas from the reformer 4 to 1% to 20% by weight solids. The pH in the scrubber solution is controlled between 5.0 and 7.0 to minimize carbon dioxide absorption and to ensure removal of acid gases. The salt solution can be directed along line 9 for treatment by conventional means, such as direct discharge (if radioactivity levels permit), discharge after selective removal of radioactive species, or encapsulation to form solid waste. Insoluble constituents in the scrubber solution can be removed by filtration if a discharge route is chosen. The warm, water-saturated off-gas stream leaves the scrubber 8 along line 10 and can be further processed to remove essentially all the water vapor by means of a refrigerated condenser 11. The condensed water leaving the condenser 11 along line 12 will include essentially all the tritium from the graphite. The condenser water, with trace levels of tritium, can be handled by one or more of the following methods. It can be recycled to provide for water cutting duty, or to supply superheated steam to the reformer. Alternatively it can be discharged as water vapor or liquid water, or used to mix with cement for solidification of other radioactive waste. Some of the iodine in the off-gas will also tend to be carried with the water leaving the condenser 11 along line 13. The cool, dry off-gas consists almost exclusively of carbon-dioxide and small amounts of oxygen and nitrogen. If allowed by regulation, the carbon-dioxide rich off-gas can be HEPA filtered in vessel 14, monitored at 15, and then discharged to the facility stack at 16. If required by regulation, carbon dioxide can be removed from the off-gas by a refrigerated CO2 condenser 18. The concentrated carbon dioxide can be transferred along line 20 for conversion into a solid carbonate salt. The remaining non-condensable gases can then be circulated along line 19 to the HEPA filter 14, monitored and then discharged to the facility stack 16. The final small off-gas flow represents less than 5% of the off-gas flow from the outlet of the reformer. The concentrated carbon dioxide stream 20 issuing from the condenser is next converted to a solid, inert carbonate compound. Preferably, the carbon dioxide is reacted with calcium or magnesium oxides or metals in reaction vessel 21 to produce insoluble magnesium or calcium carbonate salts. Alternatively, carbon dioxide may be reacted with MAGNOX fuel element debris waste is described in several publications (e.g., xe2x80x9cCEGB dissolves Magnox fuel element debris at Dungenessxe2x80x9d by FH Passant, CP Haigh and ASD Willis Nuclear Engineering International, Feb. 1988 pp 44-51). Once the carbonate salt is formed, in can then be conveniently used to fill void spaces in existing radioactive waste disposal containers. It will be apparent to those skilled in the art that many substitutions and modifications can be made to the foregoing preferred embodiments without departing from the spirit and scope of the present invention, defined by the appended claims.
	abstract	A travel system (20) for a canister storage, transfer, or transport system generally includes a support structure (22), at least one traveling device (24) for preparing, inspecting, and/or repairing the canister, and a base ring (26) for supporting the traveling device and providing for rotational movement of the traveling device relative to the support structure.
	description	This invention was made with Government support under contract number DE-AC02-06CH11357, awarded by the U.S. Department of Energy. The Government has certain rights in the invention. Single and multiple-step electrochemical processes are useable to reduce metal-oxides to their corresponding metallic (unoxidized) state. Such processes are conventionally used to recover high purity metal, metals from an impure feed, and/or extract metals from their metal-oxide ores. Multiple-step processes conventionally dissolve metal or ore into an electrolyte followed by an electrolytic decomposition or selective electro-transport step to recover unoxidized metal. For example, in the extraction of uranium from spent nuclear oxide fuels, a chemical reduction of the uranium oxide is performed at 650° C., using a reductant such as Li dissolved in molten LiCl, so as to produce uranium and Li2O. The solution is then subjected to electro-winning, where dissolved Li2O in the molten LiCl is electrolytically decomposed to regenerate Li. The uranium metal is prepared for further use, such as nuclear fuel in commercial nuclear reactors. Single-step processes generally immerse a metal oxide in molten electrolyte, chosen to be compatible with the metal oxide, together with a cathode and anode. The cathode electrically contacts the metal oxide and, by charging the anode and cathode (and the metal oxide via the cathode), the metal oxide is reduced through electrolytic conversion and ion exchange through the molten electrolyte. Single-step processes generally use fewer components and/or steps in handling and transfer of molten salts and metals, limit amounts of free-floating or excess reductant metal, have improved process control, and are compatible with a variety of metal oxides in various starting states/mixtures with higher-purity results compared to multi-step processes. Example embodiments include modular cathode assemblies useable in electrolytic reduction systems. Example embodiment cathode assemblies include a basket that allows a fluid electrolyte to enter and exit the basket, while the basket is electrically conductive and may transfer electrons to or from an electrolyte in the basket. The basket extends down into an electrolyte from an assembly support having a basket electrical connector to provide electric power to the basket. The basket may be divided into an upper and lower section so as to provide a space where the material to be reduced may be inserted into the lower section and so as to prevent electrolyte or other material or thermal migration up the basket. Example embodiment cathode assemblies are disclosed with a rectangular shape that maximizes electrolyte surface area for reduction, while also permitting easy and modular placement of the assemblies at a variety of positions in reduction systems. Example embodiment modular cathode assemblies also include a cathode plate running down the middle of the basket. The cathode plate is electrically insulated from the basket but is also electrically conductive and provides a primary or reducing current to the material to be reduced in the basket. Thermal and electrical insulating bands or pads may also be placed along a length of the cathode plate to align and seal the basket upper portion with the cathode plate. Example embodiment modular cathode assemblies may have one or more standardized electrical connectors through which unique electrical power may be provided to the basket and plate. For example, the electrical connectors may have a same knife-edge shape that can electrically and mechanically connect modular cathode assemblies at several positions of electrical contacts having corresponding shapes. Example embodiment modular cathode assemblies are useable in electrolytic oxide reduction systems where they may be placed at a variety of desired positions. Example embodiment modular cathode assembly may be supported by a top plate above an opening into the electrolyte container. Electrolytic oxide reduction systems may provide a series of standardized electrical contacts that may provide power to both baskets and cathode plates at several desired positions in the system. Example methods include operating an electrolytic oxide reduction system by positioning modular cathode and anode assemblies at desired positions, placing a material to be reduced in the basket, and charging the modular cathode and anode assemblies through the electrical connectors so as to reduce the metal oxide and free oxygen gas. The electrolyte may be fluidized in example methods so that the anodes, basket, and material to be reduced in the basket extend into the electrolyte. Additionally, unique levels and polarities of electrical power may be supplied to each of the modular cathode assembly baskets and cathode plates and modular anode assembly, in order to achieve a desired operational characteristic, such as reduction speed, material volume, off-gas rate, oxidizing or reducing potential, etc. Hereinafter, example embodiments will be described in detail with reference to the attached drawings. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the language explicitly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures or described in the specification. For example, two figures or steps shown in succession may in fact be executed in series and concurrently or may sometimes be executed in the reverse order or repetitively, depending upon the functionality/acts involved. The inventors have recognized a problem in existing single-step electrolytic reduction processes that the known processes cannot generate large amounts of reduced, metallic products on a commercial or flexible scale, at least in part because of limited, static cathode size and configuration. Single step electrolytic reduction processes may further lack flexibility in configuration, such as part regularity and replaceability, and in operating parameters, such as power level, operating temperature, working electrolyte, etc. Example systems and methods described below uniquely address these and other problems, discussed below or not. Example Embodiment Electrolytic Oxide Reduction Systems FIG. 1 is an illustration of an example embodiment electrolytic oxide reduction system (EORS) 1000. Although aspects of example embodiment EORS 1000 are described below and useable with related example embodiment components, EORS 1000 is further described in the following co-pending applications: Serial No.Filing DateAttorney Docket No.XX/XXX,XXXHerewith24AR246135 (8564-000224)XX/XXX,XXXHerewith24AR246136 (8564-000225)XX/XXX,XXXHerewith24AR246138 (8564-000226)XX/XXX,XXXHerewith24AR246140 (8564-000228)The disclosures of the above-listed co-pending applications are incorporated by reference herein in their entirety. As shown in FIG. 1, example embodiment EORS 1000 includes several modular components that permit electrolytic reduction of several different types of metal-oxides on a flexible or commercial scale basis. Example embodiment EORS 1000 includes an electrolyte container 1050 in contact with or otherwise heated by a heater 1051, if required to melt and/or dissolve an electrolyte in container 1050. Electrolyte container 1050 is filled with an appropriate electrolyte, such as a halide salt or salt containing a soluble oxide that provides mobile oxide ions, chosen based on the type of material to be reduced. For example, CaCl2 and CaO, or CaF2 and CaO, or some other Ca-based electrolyte, or a lithium-based electrolyte mixture such as LiCl and Li2O, may be used in reducing rare-earth oxides, or actinide oxides such as uranium or plutonium oxides, or complex oxides such as spent nuclear fuel. The electrolyte may further be chosen based on its melting point. For example, an electrolyte salt mixture of LiCl and Li2O may become molten at around 610° C. at standard pressure, whereas a CaCl2 and CaO mixture may require an operating temperature of approximately 850° C. Concentrations of the dissolved oxide species may be controlled during reduction by additions of soluble oxides or chlorides by electrochemical or other means. EORS 1000 may include several supporting and structural members to contain, frame, and otherwise support and structure other components. For example, one or more lateral supports 1104 may extend up to and support a top plate 1108, which may include an opening (not shown) above electrolyte container 1050 so as to permit access to the same. Top plate 1108 may be further supported and/or isolated by a glove box (not shown) connecting to and around top plate 1108. Several standardized electrical contacts 1480 (FIG. 2) and cooling sources/gas exhausts may be provided on or near top plate 1108 to permit anode and cathode components to be supported by and operable through EORS 1000 at modular positions. A lift basket system, including a lift bar 1105 and/or guide rods 1106 may connect to and/or suspend cathode assemblies 1300 that extend down into the molten electrolyte in electrolyte container 1050. Such a lift basket system may permit selective lifting or other manipulation of cathode assemblies 1300 without moving the remainder of EORS 1000 and related components. In FIG. 1, EORS 1000 is shown with several cathode assemblies 1300 alternating with several anode assemblies 1200 supported by various support elements and extending into electrolyte container 1050. The assemblies may further be powered or cooled through standardized connections to corresponding sources in EORS 1000. Although ten cathode assemblies 1300 and eleven anode assemblies 1200 are shown in FIG. 1, any number of anode assemblies 1200 and cathode assemblies 1300 may be used in EORS 1000, depending on energy resources, amount of material to be reduced, desired amount of metal to be produced, etc. That is, individual cathode assemblies 1300 and/or anode assemblies 1200 may be added or removed so as to provide a flexible, and potentially large, commercial-scale, electrolytic reduction system. In this way, through the modular design of example embodiment EORS 1000, anode assemblies 1200 and cathode assemblies 1300, example embodiments may better satisfy material production requirements and energy consumption limits in a fast, simplified single-stage reduction operation. The modular design may further enable quick repair and standardized fabrication of example embodiments, lower manufacturing and refurbishing costs and time consumption. FIG. 2 is an illustration of EORS 1000 in an alternate configuration, with basket lifting system including lift bar 1105 and guide rods 1106 raised so as to selectively lift only modular cathode assemblies 1300 out of electrolyte container 1050 for access, permitting loading or unloading of reactant metals oxides or produced reduced metals from cathode assemblies 1300. In the configuration of FIG. 2, several modular electrical contacts 1480 are shown aligned at modular positions about the opening in top plate 1108. For example, electrical contacts 1480 may be knife-edge contacts that permit several different alignments and positions of modular cathode assemblies 1300 and/or anode assemblies 1200 within EORS 1000. As shown in FIG. 1, a power delivery system including a bus bar 1400, anode power cable 1410, and/or cathode power cable 1420 may provide independent electric charge to anode assemblies 1200 and/or cathode assemblies 1300, through electrical contacts (not shown). During operation, electrolyte in electrolyte container 1050 may be liquefied by heating and/or dissolving or otherwise providing a liquid electrolyte material compatible with the oxide to be reduced. Operational temperatures of the liquefied electrolyte material may range from approximately 400-1200° C., based on the materials used. Oxide material, including, for example, Nd2O3, PuO2, UO2, complex oxides such as spent oxide nuclear fuel or rare earth ores, etc., is loaded into cathode assemblies 1300, which extend into the liquid electrolyte, such that the oxide material is in contact with the electrolyte and cathode assembly 1300. The cathode assembly 1300 and anode assembly 1200 are connected to power sources so as to provide opposite charges or polarities, and a current-controlled electrochemical process occurs such that a desired electrochemically-generated reducing potential is established at the cathode by reductant electrons flowing into the metal oxide at the cathode. Because of the generated reducing potential, oxygen in the oxide material within the cathode assemblies 1300 is released and dissolves into the liquid electrolyte as an oxide ion. The reduced metal in the oxide material remains in the cathode assembly 1300. The electrolytic reaction at the cathode assemblies may be represented by equation (1):(Metal Oxide)+2e−→(reduced Metal)+O2− (1)where the 2e− is the current supplied by the cathode assembly 1300. At the anode assembly 1200, negative oxygen ions dissolved in the electrolyte may transfer their negative charge to the anode assembly 1200 and convert to oxygen gas. The electrolysis reaction at the anode assemblies may be represented by equation (2):2O2−→O2+4e− (2)where the 4e− is the current passing into the anode assembly 1200. If, for example, a molten Li-based salt is used as the electrolyte, cathode reactions above may be restated by equation (3):(Metal Oxide)+2e−+2Li+→(Metal Oxide)+2Li→(reduced Metal)+2Li++O2− (3)However, this specific reaction sequence may not occur, and intermediate electrode reactions are possible, such as if cathode assembly 1300 is maintained at a less negative potential than the one at which lithium deposition will occur. Potential intermediate electrode reactions include those represented by equations (4) and (5):(Metal Oxide)+xe−+2Li+→Lix(Metal Oxide) (4)Lix(Metal Oxide)+(2−x)e−+(2−x)Li+→(reduced Metal)+2Li++O2− (5)Incorporation of lithium into the metal oxide crystal structure in the intermediate reactions shown in (4) and (5) may improve conductivity of the metal oxide, favoring reduction. Reference electrodes and other chemical and electrical monitors may be used to control the electrode potentials and rate of reduction, and thus risk of anode or cathode damage/corrosion/overheating/etc. For example, reference electrodes may be placed near a cathode surface to monitor electrode potential and adjust voltage to anode assemblies 1200 and cathode assemblies 1300. Providing a steady potential sufficient only for reduction may avoid anode reactions such as chlorine evolution and cathode reactions such as free-floating droplets of electrolyte metal such as lithium or calcium. Efficient transport of dissolved oxide-ion species in a liquid electrolyte, e.g. Li2O in molten LiCl used as an electrolyte, may improve reduction rate and unoxidized metal production in example embodiment EORS 1000. Alternating anode assemblies 1200 and cathode assemblies 1300 may improve dissolved oxide-ion saturation and evenness throughout the electrolyte, while increasing anode and cathode surface area for larger-scale production. Example embodiment EORS 1000 may further include a stirrer, mixer, vibrator, or the like to enhance diffusional transport of the dissolved oxide-ion species. Chemical and/or electrical monitoring may indicate that the above-described reducing process has run to completion, such as when a voltage potential between anode assemblies 1200 and cathode assemblies 1300 increases or an amount of dissolved oxide ion decreases. Upon a desired degree of completion, the reduced metal created in the above-discussed reducing process may be harvested from cathode assemblies 1300, by lifting cathode assemblies 1300 containing the retained, reduced metal out of the electrolyte in container 1050. Oxygen gas collected at the anode assemblies 1200 during the process may be periodically or continually swept away by the assemblies and discharged or collected for further use. Although the structure and operation of example embodiment EORS 1000 has been shown and described above, it is understood that several different components described in the incorporated documents and elsewhere are useable with example embodiments and may describe, in further detail, specific operations and features of EORS 1000. Similarly, components and functionality of example embodiment EORS 1000 is not limited to the specific details given above or in the incorporated documents, but may be varied according to the needs and limitations of those skilled in the art. Example Embodiment Cathode Assemblies FIG. 3 is an illustration of an example embodiment modular cathode assembly 300. Modular cathode assembly 300 may be useable as cathode assemblies 1300 described above in connection with FIG. 1. Although example embodiment assembly 300 is illustrated with components from and useable with EORS 1000 (FIGS. 1-2), it is understood that example embodiments are useable in other electrolytic reduction systems. Similarly, while one example assembly 300 is shown in FIGS. 3 & 4, it is understood that multiple example assemblies 300 are useable with electrolytic reduction devices. In EORS 1000 (FIGS. 1-2), for example, multiple cathode assemblies may be used in a single EORS 1000 to provide balanced modular anode and/or cathode assemblies. As shown in FIG. 3, example embodiment modular cathode assembly 300 includes a basket 310, into which oxides or other materials for reduction may be placed. Basket 310 may include an upper portion 311 and a lower portion 312, and these portions may have differing structures to accommodate use in reduction systems. For example, lower portion 312 may be structured to interact with/enter into a liquid electrolyte, such as those molten salt electrolytes discussed above. Lower portion 312 may be vertically displaced from upper portion 311 to ensure immersion in/extension into any electrolyte, while upper portion 311 may reside above an electrolyte level. Lower portion 312 may form a basket or other enclosure that holds or otherwise retains the material to be reduced. As shown in FIG. 3, lower portion 312 may be divided into three or more sections to separate and/or evenly distribute material to be reduced in lower portion 312. The separation in lower portion 312 may also provide additional surface area for direct contact and electrical flow between target material and basket 310 during a reducing operation. Lower portion 312 and upper portion 311 may be sufficiently divided to define a gap or other opening through which material may be placed into lower portion 312. For example, as shown in FIG. 3, upper portion 311 and lower portion 312 may be joined at a rivet point 316 along shared sheet metal side 315 so as to define a gap for oxide entry along a planar face of example embodiment modular cathode assembly 300. While upper portion 311 and lower portion 312 may include some discontinuity, it is understood that electrical current may still flow through both portions, and the two portions are flexibly mechanically connected, through rivet point 316 or any other suitable electromechanical connection. Permeable material 330 is placed along planar faces of lower portion 312 in the example embodiment of FIG. 3. The permeable material 330 permits liquid electrolyte to pass into lower portion 312 while retaining a material to be reduced, such as uranium oxide, so that the material does not physically disperse into the electrolyte or outside basket 310. Permeable material 330 may include any number of materials that are resilient to, and allow passage of, ionized electrolyte therethrough, including inert membranes and finely porous metallic plates, for example. The permeable material 330 may be joined to a sheet metal edge 315 and bottom to form an enclosure that does not permit oxide or reduced metal to escape from the lower portion 312. In this way, lower portion 312 may provide space for holding several kilograms of material for reduction, permitting reduction on a flexible and commercial scale, while reducing areas where molten electrolyte may solidify or clog. Upper portion 311 may be hollow and enclosed, or any other desired shape and length to permit use in reduction systems. Upper portion 311 joins to an assembly support 340, such that upper portion 311 and lower portion 312 of basket 310 extend from and are supported by assembly support 340. Assembly support 340 may support example embodiment modular cathode assembly 300 above an electrolyte. For example, assembly support 340 may extend to overlap top plate 1108 in EORS 1000 so as to support modular cathode assembly extending into electrolyte container 1050 from above. Although lower portion 312 may extend into ionized, high-temperature electrolyte, the separation from upper portion 311 may reduce heat and/or caustic material transfer to upper portion 311 and the remaining portions of modular cathode assembly 300, reducing damage and wear. Although basket 310 is shown with a planar shape extending along assembly support 340 to provide a large surface area for permeable material 330 and electrolyte interaction therethrough, basket 310 may be shaped, positioned, and sized in any manner based on desired functionality and contents. As shown in FIGS. 3 and 4, example embodiment modular cathode assembly 300 further includes a cathode plate 350. Cathode plate 350 may extend through and/or be supported by assembly support 340 and extend into basket 310. Cathode plate 350 may extend a substantial distance into basket 310, into lower section 312 so as to be submerged in electrolyte with lower section 312 and directly contact oxide material to be reduced that is held in lower section 312. As shown in FIG. 4, cathode plate may include a shape or structure to compatibly fit or match with basket 310, dividing into three sections at a lower portion to match the three individual lower baskets of lower section 312, as an example. Cathode plate 350 is electrically insulated from basket 310, except for indirect current flow from/into cathode plate 350 into/from an electrolyte or oxide material in basket 310 which plate 350 may contact. Such insulation may be achieved in several ways, including physically separating cathode plate 350 from basket 310. As shown in FIG. 3, cathode plate 350 may extend into a central portion of basket 310 without directly touching basket 310. As shown in FIG. 4, one or more insulating pads or bands 355 may be placed on cathode plate 350 for proper alignment within basket 310 while still electrically insulating cathode plate 350 and basket 310. If insulating bands 355 seat against an inner surface of upper portion 311 and/or are fabricated from a material that is also a thermal insulator, such as a ceramic material, bands 355 may additionally impede heat transfer up cathode plate 350 or into upper portion 311 of basket 310. Further, where a support 380 of cathode plate 350 rests on assembly support 340, an insulating pad or buffer 370 may be interposed between support 380 of cathode plate 350 and assembly support 340 to electrically insulate the two structures from one another. Basket 310, including upper portion 311, sheet metal edge 315, and lower portion 312 dividers and bottom, and cathode plate 350 are fabricated from an electrically conductive material that is resilient against corrosive or thermal damage that may be caused by the operating electrolyte and will not substantially react with the material being reduced. For example, stainless steel or another nonreactive metallic alloy or material, including tungsten, molybdenum, tantalum, etc., may be used for basket 310 and cathode plate 350. Other components of example embodiment modular cathode assembly 300 may be equally conductive, with the exception of insulator 370, bands 355, and handling structures (discussed below). Materials in cathode plate 350 and basket 310 may further be fabricated and shaped to increase strength and rigidity. For example, stiffening hems or ribs 351 may be formed in cathode plate 350 or in sheet metal edge 315 to decrease the risk of bowing or other distortion and/or misalignment between cathode plate 350 and basket 310. As shown in FIG. 3, a lift handle 381 may be connected to support 380 to permit removal, movement, or other handling of cathode plate 350 individually. For example, cathode plate 350 may be removed from cathode assembly 300 by a user through handle 381, leaving only basket 310. This may be advantageous in selectively cleaning, repairing, or replacing cathode plate 350 and/or harvesting or inserting material into/from basket 310. Lift handle 381 is electrically insulated from cathode plate 350 and support 380, so as to prevent user electrocution and other unwanted current flow through example electrolytic reducing systems. Cathode assembly support 340 may further include a lift basket post 390 for removing/inserting or otherwise handling or moving cathode assembly 300, including basket 310 and potentially cathode plate 350. Lift basket posts 390 may be placed at either end of cathode assembly support 340 and/or be insulated from the remainder of example embodiment modular cathode assembly 300. When used in a larger reduction system, such as EORS 1000, individual modular cathode assemblies 300, and all subcomponents thereof including basket 310 and cathode plate 350, may be moved and handled, automatically or manually, at various positions through the lift basket post 390. As shown in FIG. 3, example embodiment modular cathode assembly 300 includes one or more cathode assembly connectors 385 where modular cathode assembly 300 may mechanically and electrically connect to receive electrical power. Cathode assembly connectors 385 may be a variety of shapes and sizes, including standard plugs and/or cables, or, in example modular cathode assembly 300, knife-edge contacts that are shaped to seat into receiving fork-type connectors (FIG. 5) from example power distribution systems. Equivalent pairs of cathode assembly connectors 385 may be placed on one or both sides of modular cathode assembly 300, to provide even power to the assembly. Cathode assembly connectors 385 may electrically connect to, and provide appropriate reducing potential to, various components within example embodiment modular cathode assembly 300. For example, two separate pairs of cathode assembly connectors, 385a and 385b, may connect to different power sources and provide different electrical power, current, voltage, polarity, etc. to different parts of assembly 300. As shown in FIG. 4, inner connectors 385a may connect to cathode plate 350 through support 380. Inner connectors 385a may extend through insulator 370 and assembly support 340 without electrical contact so as to insulate cathode plate 350 from each other component. Outer connectors 385b may connect directly to assembly support 340 and basket 310. In this way, different electrical currents, voltages, polarities, etc. may be provided to cathode plate 350 and basket 310 without electrical shorting between the two. FIG. 5 is an illustration of example cathode assembly contacts 485a and 485b that may include a fork-type conductive contacts surrounded by an insulator, capable of receiving and providing power to modular cathode assembly connectors 385a and 385b. Of course, contacts 485a and 485b may be in any configuration or structure, and modular cathode connectors 385a and 385b may provide equivalent opposite configurations for mating. Anode assembly contacts 480 are also shown near cathode assembly contact 485a and 485b. Each cathode assembly contact 485a and 485b may be seated in top plate 1108 at any position(s) desired to be available to modular cathode assemblies. Each cathode assembly contact 485a and 485b may be parallel and aligned with other contacts on an opposite side of reduction systems, so as to provide a planar, thin-profile electrical contact area for modular cathode assemblies 300 connecting thereto through connectors 385a and 385b. Cathode assembly contacts 485b and 485a may provide different levels of electrical power, voltage, and/or current to connectors 385b and 385a and thus to basket 310 and cathode plate 350, respectively. For example, contact 485a may provide higher power to connectors 385a and cathode plate 350, near levels of opposite polarity provided through anode contacts 480. This may cause electrons to flow from cathode plate 350 into the electrolyte or material to be reduced and ultimately to anode assemblies and reduce oxides or other materials held in basket 310, in accordance with the reducing schemes discussed above. Contact 485b may provide lower and/or opposite polarity secondary power to contact 385b and basket 310, compared to contact 485b. As an example, lower secondary power may be 2.3 V and 225 A, while primary level power may be 2.4 V and 950 A, or primary and secondary power levels may be of opposite polarity between cathode plate 350 and basket 310, for example. In this way, opposite and variable electrical power may be provided to example embodiment modular cathode assembly 300 contacting cathode assembly contacts 485a and 485b through connectors 385a and 385b. Additionally, both primary and secondary levels of power may be provided through contact 485a to connector 385a, or any other desired or variable level of power for operating example reduction systems. Table 1 below shows examples of power supplies for each contact and power line thereto. TABLE 1Power Level (Polarity)ConnectorContactFor ElectrodePrimary (+)Anode480Anode AssemblyPrimary (−) or Secondary (−)385a485aCathode Plate (−)Secondary (+)386b485bBasket (+) Because basket 310 may act as a secondary anode when charged with opposite polarity from cathode plate 350, current may flow through the electrolyte or material to be reduced between cathode plate 350 and basket 310. This secondary internal current in example embodiment cathode assembly 300 may prevent metallic lithium or dissolved metallic alkali or alkaline earth atoms from exiting basket lower section 312 where it may not contact material to be reduced, such as a metal oxide feed. Operators may selectively charge basket 310 based on measured electrical characteristics of reduction systems, such as when operators determine electrolyte within basket contains dissolved metallic alkali or alkaline earth atoms. As shown in FIG. 1, example embodiment modular cathode assemblies 300 are useable as cathode assemblies 1300 and may be standardized and used in interchangeable combination, in numbers based on reducing need. For example, if each modular cathode assembly 300 includes similarly-configured contacts 385, any modular cathode assembly 300 may be replaced with another or moved to other correspondingly-configured locations in a reducing system, such as EORS 1000. Each anode assembly may be powered and placed in a proximity, such as alternately, with a cathode assembly to provide a desired and efficient reducing action to metal oxides in the cathode assemblies. Such flexibility may permit large amounts of reduced metal to be formed in predictable, even amounts with controlled resource consumption and reduced system complexity and/or damage risk in example embodiment systems using example embodiment modular cathode assemblies 300. Example embodiments discussed above may be used in unique reduction processes and methods in connection with example systems and anode assembly embodiments. Example methods include determining a position or configuration of one or more modular cathode assemblies within a reduction system. Such determination may be based on an amount of material to be reduced, desired operating power levels or temperatures, anode assembly positions, and/or any other set or desired operating parameter of the system. Example methods may further connect cathode assemblies to a power source. Because example assemblies are modular, external connections may be made uniform as well, and a single type of connection may work with all example embodiment cathode assemblies. An electrolyte used in reduction systems may be made molten or fluid in order to position anode and/or cathode assemblies at the determined positions in contact with the electrolyte. A desired power level or levels, measured in current or voltage or polarity, is applied to cathode assemblies through an electrical system so as to charge baskets and/or plates therein in example methods. This charging, while the basket and plate are contacted with a metal oxide and electrolyte in contact with nearby anodes, reduces the metal oxide in the baskets or in contact with the same in the electrolyte, while de-ionizing some oxygen dissolved into the electrolyte in the cathode assembly. Example methods may further swap modular parts of assemblies or entire assemblies within reduction systems based on repair or system configuration needs, providing a flexible system than can produce variable amounts of reduced metal and/or be operated at desired power levels, electrolyte temperatures, and/or any other system parameter based on modular configuration. Following reduction, the reduced metal may be removed and used in a variety of chemical processes based on the identity of the reduced metal. For example, reduced uranium metal may be reprocessed into nuclear fuel. Example embodiments thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied through routine experimentation and without further inventive activity. For example, although baskets in cathode assemblies containing three rectangular compartments are shown, it is of course understood that other numbers and shapes of compartments and overall configurations of baskets may be used based on expected cathode assembly placement, power lever, necessary oxidizing potential, etc. Variations are not to be regarded as departure from the spirit and scope of the example embodiments, 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 system, comprising:a first chamber including an inlet and an outlet for a first material, the first chamber being configured to receive the first material from a source of the first material through the inlet and to produce light using the first material; anda recycling device coupled to the inlet and the outlet of the first chamber, the recycling device being configured to receive the first material from the outlet of the first chamber and to recycle the first material, so that the first material is re-input through the inlet of the first chamber for further production of light. 2. The system of claim 1, further comprising:a controller that routes the first material to the recycling device and routes the recycled material from the recycling device back to the source of the first material. 3. The system of claim 1, wherein said first material is one of xenon, lithium vapor, tin, krypton, and water vapor. 4. The system of claim 1, wherein the recycling device is positioned outside the first chamber. 5. The system of claim 1, wherein the light comprises extreme ultra violet light. 6. The system of claim 1, wherein the first chamber houses a plasma light source that produces extreme ultra violet light. 7. The system of claim 1, further comprising:a second chamber that includes a second material and that is coupled to the first chamber, the second chamber receiving the produced light; anda lock formed with a third material that flows between the first material and the second material in an area in which they converge. 8. The system of claim 7, wherein said third material is one of helium, neon, and nitrogen. 9. The system of claim 7, wherein:the recycling device separates the first material from the third material, such that the first material is reused to form the produced light. 10. A method, comprising:(a) using a first material to produce extreme ultraviolet radiation within a first chamber of a light source; and(b) reusing the first material in the first chamber to produce extreme ultraviolet radiation. 11. The method of claim 10, wherein said first material is one of xenon, lithium vapor, tin, krypton, and water vapor. 12. The method of claim 10, further comprising:using a second material in a second chamber that receives the radiation produced by the first material; andseparating the first chamber from the second chamber with a third material that flows between them. 13. The method of claim 12, wherein said third material is one of helium, neon, and nitrogen. 14. The method of claim 12, further comprising separating the first material from the third material and reusing the first material. 15. The method of claim 12, wherein said second material reduces contamination on optical elements within a second chamber. 16. The method of claim 12, wherein said second material protects optical elements. 17. The method of claim 10, wherein said steps (a) and (b) happen at a same time. 18. A discharge plasma light source for producing extreme ultraviolet radiation, said source being provided with a first chamber wherein radiation is produced from a first material that is recycled after producing the radiation to be reused for the further production of extreme ultraviolet radiation in the first chamber. 19. The discharge plasma light source of claim 18, wherein the first material is a metal target. 20. The discharge plasma light source of claim 18, wherein the first material is tin.
041349415	description	Referring more specifically to FIG. 1 of the drawings there is shown schematically an exemplary illustrative form of the spherically shaped fuel element of the invention. A graphite nucleus 1 which only contains fertile material particles 4 is surrounded on all sides by a graphite zone 2 which contains only fuel particles 5 and a further outer shell 3 of pure graphite. As pointed out above the three layers are concentric. For example the nucleus 1 had a diameter of 40 mm and both shells 2 and 3 have thickness of 5 mm so that the diameter of the spherical fuel element in this case is 60 mm. The diameter of the three layers and of the overall sphere can be varied, e.g., the nucleus 1 can have a diameter of 25 to 60 mm, the graphite zone 2 a thickness of 3 to 15 mm and the outer shell 3 a thickness of 2 to 10 mm and the diameter of the overall sphere can be 50 to 75 mm. The same graphite material is always employed in the three zones (1, 2 and 3). Essentially the fuel material zone is separately arranged from the fertile material zone in the nucleus of the sphere, the fuel material zone surrounding this nucleus as a shell. All three zones are joined together without transition. This spatially separated arrangement of the fuel material zone from the fertile material zone of the invention permits in the so-called Head-End process, the first process step for reworking the fuel element, a simple separation of the uranium containing particles from the thorium containing coated particle after the irradiation in the reactor. A good irradiation behavior of the fuel element, especially the possibility of retaining gaseous and solid fission products takes for granted the lowest possible fuel temperature in the center of the sphere. This temperature is fixed at a fixed surface temperature by the temperature gradient in the shpere. The temperature gradient depends on the fuel element output, the heat conductivity of the graphite matrix and the geometric arrangement of the heat producing zone. While the fuel element output is fixed by the criteria of construction chosen for the reactor core and the heat conductivity of a material is constant a reduction of the fuel temperature in the nucleus of the sphere in general can only be produced through suitable arrangement of the fuel or fertile material zone. In order to shorten the heat path to the outside therefore, the uranium containing fuel zone is arranged outside the center of the sphere. In the first half of the insertion time of a fuel element sphere nearly the entire heat production takes place by the fission of Uranium 235; therewith the fuel element output is chiefly carried by the fuel material zone. In the same measure as the Uranium 235 burns down and the Uranium 233 is bred from the Thorium 232, the heat production is displaced inside the sphere to the fertile material zone. This displacement of the heat production from the fuel material zone into the fertile material zone is accompanied by a strong reduction in the total fuel element output, so that only a relatively low temperature gradient is maintained in the sphere. The fuel element construction of the invention with separated arrangement of fuel and fertile zones in the nucleus and a surrounding shell makes possible, in contrast to the known fuel elements, a considerable lowering of the temperature gradient in the shpere, whereby both the ability to retain fission products is improved and also the thermal and connected therewith the irradiation induced mechanical stresses in the fuel element are reduced. Thereby the mechanical stability of the sphere is further increased during the entire residence time in the reaction. It has proven favorable, if the common interval between the coated fuel particles 5 embedded in the graphite matrix of the zone 2 is greater by a factor of 1.2 to 2.5 than the interval between the coated fertile material particles 4 embedded in the graphite matrix of the nucleus 1 of the sphere, which latter interval should be at least 100-200 .mu. m. This is true for both the average interval of the coated fuel or fertile material particles in zone 2 or in the nucleus 1 and for the thickness of the encasing layers through which in the pressing of the sphere the interval is limited this minimal interval occuring for two encased coated particles. In order to increase the retention of gaseous and solid fission products the fuel particles besides being coated with pyrolytic carbon preferably additionally are coated with an intermediate layer of SiC. In pressing the spheres there is the danger that at too thin an encasing a spot loading of coated particles occurs as the result of a local graphite matrix formation which leads to damage to the brittle SiC coating layers while the pyrolytic carbon coating layer on the fertile particles without SiC are considerably more elastic and still not damaging. The greater distance between the fuel particles compared to the fertile particles has the advantage that the relatively thick encasing layer of graphite matrix powder guarantees that the brittle silicon carbide layers of the fuel particle are not damaged in the pressing. An especial advantage of the separate arrangement of fuel and fertile material according to the invention is that a simple separation of the uranium containing particles from the thorium containing particles is offered in the Head-End stage of the reprocessing of the fuel elements after the irradiation in the reactor. In the Head-End stage the burned down fuel elements are subjected to a burning process in oxygen at about 1000 to 1200.degree. C. In this process the graphite structural material is burned off, whereby the fertile and fuel particles become exposed. In order to make possible a uniform burning off of the surface of the sphere it is advantageous to burn the spheres in a rotating cylindrical furnace as shown in FIG. 2. According to the invention the burning of the spherically shaped fuel elements takes place in two steps. In the first step the spheres of for example 60 mm diameter to 40 mm diameter are burned off and thereby only the uranium containing fuel particles are exposed. In the second step there takes place the burning of the nucleus of the sphere and the recovery of the thorium containing fertile material particles. In a given case between the fuel zone 2 and fertile material zone 1 there can be arranged a thin intermediate layer, for example 1-2 mm thick of pure graphite matrix, as for example the layer 20 in FIG. 3, so that in the burning off of the spheres a complete separation of fuel and fertile particles is guaranteed. In a rotating cylindrical furnace 11 both outer graphite layers of the spherical fuel elements 12 having a diameter of 60 mm are burned off with air oxygen whereby the fuel particles 13 can fall through the perforated furnace wall 14 (perforations 40 mm in diameter) and a grate 15 found thereunder and provided with holes 5 mm in diameter. They are caught in a container 16. If both outer graphite layers of the fuel elements 12 are burned off and the spheres therewith shrunk to a diameter of 40 mm, the spheres fall through the furnace wall 14 on the downwardly sloping grate 15 and into a second rotating cylindrical furnace 17 where the residual graphite matrix is burned off. From here the fertile material particles 18 fall into a container 19. It has been found especially advantageous to make a varient of the three zone elements of the invention in which the fuel containing graphite zone 2 has a smaller strength than the shell 3 and the fertile material containing nucleus 1. This can be attained in the production of the fuel elements by not using as pressing material for the pressing of the fuel zone onto the nucleus a mixture of encased coated fuel particles and graphite molding powder but instead using a charge of thickly encased coated fuel particles without addition of molding powder as prepared according to Hrovat German Pat. No. 1,909,871, the entire disclosure of which is incorporated herein and relied upon. When a three zoned fuel element which has mechanically weaker zone is crushed, the outer shell and fuel zone spall off smoothly from the fertile material containing nucleus without damaging the nucleus. The strength of such a three zoned fuel element, however, is still sufficient for use in a spherical pile reactor in which according to more modern construction the fuel elements are only passed through once during their time of insertion and through constructive precautions the mechanical load by the reactor-control rods inserted directly into the bed of spheres in the reactor core is sufficiently limited. The purpose of the production of three zoned fuel elements with lower mechanical strength of the fuel zone is to make the reworking according to the process of the invention still simpler and safer The fuel elements after insertion in the reactor become crushed and the spalled off parts, which arise from the shell and the fuel zone can be burned separately from the fertile material containing nucleus. Through this a still more certain separation between fertile material and fuel material is produced. The distribution after the crushing for example can take place either through taking out the nucleus of the sphere or through sieve separation. The crushing of the radioactive fuel elements after their insertion in the reactor and the separation of the spalled off parts from the nucleus of the sphere as well as the separate burning is undertaken in a so-called hot cell in remote operation. In the production of three zoned elements according to the invention with a mechanically weaker fuel zone the strength of the fuel zone and therewith of the fuel element can be influenced by various modes of action and thereby be adapted according to the different requirements which are set by the reactor or the reprocessing. On the one hand by changing the individual molding pressures in the preliminary pressing steps for the nucleus and zone there can be influenced the adhesion between nucleus and zone and the strength of these regions, on the other hand in a given case the strength of the zone and of the fuel element can be increased if only a small amount of molding powder is added in the pressing of the zone. The invention will be further illustrated by the following examples showing the production of spherically shaped fuel elements. Unless otherwise indicated all parts and percentages are by weight. EXAMPLE 1 As fuel particles there were employed spherically shaped kernels of UO.sub.2 having a diameter of 210.mu.m. These particles were twice provided with pyrolytically deposited carbon layers having a total thickness of 160.mu.m. The coated particles with a diameter of 560.mu.m and a density of 2.2 g/cm.sup.3 contained 23 weight % uranium. The fertile material particles (ThO.sub.2) having a kernel diameter of 617.mu.m were likewise double coated with pyrolytically deposited carbon layers having a total thickness of 160.mu.m. The coated particles having a diameter of 905.mu.m and a density of 3.99 g/cm.sup.3 contained 63 weight % thorium. As graphite molding powder there was employed a mixture consisting of 64 weight % natural graphite, 16% of graphitized petroleum coke and 20% novolak (phenolformaldehyde) resin binder. The fuel and fertile material particles were encased with the graphite molding powder in separate operations with addition of methanol in a rotating drum. The amounts set were so chosen that there was formed on the fertile material particles an encasing layer of 160.mu.m and on the fuel material particles an encasing layer having a thickness of 240.mu.m. For the production of the spherical nuclei 48 grams of the encased coated fertile material particles together with 30 grams of graphite molding powder of the type set forth above were transferred into a rubber mold, mixed thoroughly and preliminarily pressed into a spherical nucleus at a pressure of 50 kg/cm.sup.2. In a second operation this nucleus was arranged in a second rubber mold with the help of three interval spacers in the center of the mold and the rest of the volume of the rubber mold filled with a mixture consisting of 41 grams of encased coated fuel particles and 20 grams of graphite molding powder. After that thecompression took place at a pressure of 80 kg/cm.sup.2. Subsequently these preliminarily pressed spheres were provided according to a process known itself and described in Hrovat German Offenlegungsschrift No. 1,646,783 (the entire disclosure of which is hereby incorporated by reference and relied upon), with a shell of the same graphite molding powder and finally molded under high pressure (3 metric tons/cm.sup.2). The spheres were heated to 800.degree. C. for 18 hours to carbonize the binder resin and after the cooling roasted in a further operation at 1800.degree. C. After the final temperature treatment the spheres were turned to the predetermined diameter (6 cm). The finished element contained 18 grams of thorium in the 40 mm diameter nucleus of the shpere and 2 grams of uranium in the 5mm thick fuel zone. The measured breaking load through crushing between two parallel steel plates amounted to 2300 kp. EXAMPLE 2 The production of fertile material containing nucleus and total graphite molding powder took place in the same way as in Example 1. As fuel particles there were used UO.sub.2 kernels having a diameter of 210.mu.m which were provided with pyrolytically deposited multiple carbon layers and with an intermediate silicon carbide layer. The coated particles having an average diameter of 560.mu.m and a density of 2.33 g/cm.sup.3 contained 20.9 weight 7 of uranium. These fuel particles were encased with graphite molding powder as in Example 1 and has an encasing layer having a thickness of 310.mu.m. In pressing the fuel zone on the preliminarily pressed fertile material containing nucleus of the sphere two rubber molds prepared as in Example 1 were filled with 60 grams of encased coated fuel particles without the addition of molding powder, after which compression was carried out at a pressure of 80 kp/cm.sup.2. The subsequent process steps and the sphere dimensions obtained and uranium/thorium content were the sme as in Example 1. The breaking load of the fuel elements produced amounted to 1800 kp. In crushing the outer shell and the fuel zone spalled off from the unchanged nucleus in many pieces. When a thin pure graphite layer is provided between the fertile material zone and the fuel zone it is generally 0.5 to 3 mm thick. The process of making the fuel elements can comprise, consist of or consist essentially of the aforementioned steps as can the method of reworking the spheres after use. Likewise the fuel elements can comprise, consist of or consist essentially of the stated layers.
	abstract	A collimator comprises a pair of first plate members having X-ray absorbability and a pair of second plate members having X-ray absorbability. The pair of first plate members are movable in a direction parallel to surfaces thereof, and have respective end faces opposed to each other with an X-ray passing aperture being defined by a spacing between the opposed end faces of the first plate members. The pair of second plate members are capable of being folded in a zigzag fashion through hinges, and in order to intercept other X-rays than the X-ray passing through the aperture, each of the second plate members is connected at one end thereof to each end of the first plate members on the side opposite to the opposed end faces of the first plate members and is connected at the other end thereof to each of fixing portions.
	abstract	There is provided an illumination system for microlithography with wavelengths≦193 nm. The illumination system includes a primary light source, a first optical component, a second optical component, an image plane, and an exit pupil. The first optical component transforms the primary light source into a plurality of secondary light sources that are imaged by the second optical component in the exit pupil. The first optical component includes a first optical element having a plurality of first raster elements that are imaged into the image plane producing a plurality of images being superimposed at least partially on a field in the image plane. The first raster elements that are imaged into the image plane are illuminated almost completely.
063209233	description	DESCRIPTION OF THE PREFERRED EMBODIMENT A locking device 10 according to the present invention is shown in FIG. 1. In one embodiment, the locking device 10 assists a restraining ring 34 and a wedge 18 in supporting a jet pump downcomer 11 in a desired position. Typically, the restraining ring 34 supports the downcomer 11. In the embodiment shown, the downcomer 11 is located inside the restraining ring 34 at the ring's inner peripheral surface 33, FIG. 1. Two adjustable screws 36 and the wedge 18 position the downcomer 11 within the restraining ring 34. The adjustable screws 36 extend through the restraining ring 34, and each screw is located on an opposing side of the restraining ring 34. The wedge 18 is located between the restraining ring 34 and the downcomer 11, and is largely held in place by gravity. The wedge 18 includes a vertically extending surface 32 that contacts the downcomer 11. The wedge 18 is carried by a guide bolt 20. Two guide blocks 22, 24 carried by the exterior surface of the downcomer 11 support the guide bolt 20 in an axial direction relative to the downcomer 11. In the preferred embodiment, each guide block 22, 24 is welded to the downcomer 11. The locking device 10 is fabricated of stainless steel, and includes an upper jaw 12, a lower jaw 14, and a tightening screw 16. The locking device 10 is lightweight, and may be easily installed and maintained by those of ordinary skill in the art. When installed on the downcomer 11, the upper jaw 12 and the lower jaw 14 are vertically disposed such that the upper jaw 12 rests against the top surface 31 of the wedge 18 and the lower jaw 14 is located below the wedge 18. The upper jaw 12 and the lower jaw 14 are rectangularly-shaped members. Both the upper jaw 12 and the lower jaw 14 include a distal end 28, 30, respectively, and a proximate end 25, 15, respectively. The distal ends 28, 30 are each moveably supported by the guide bolt 20. In one embodiment, the distal ends 28, 30, respectively, define a hook 26(a), 26(b). Each hook 26(a), 26(b) is movably positioned around the guide bolt 20. As shown in FIGS. 1, 2 and 3, the tightening screw 16 extends between the upper jaw 12 and the lower jaw 14. Specifically, the tightening screw 16 supports the proximate ends 15 and 25, respectively, of the upper jaw 12 and the lower jaw 14. As illustrated in FIGS. 1 and 2, a housing 38 retains the tightening screw 16. The housing 38 defines a recess 40 that receives the restraining ring 34. As the tightening screw 16 is tightened, the upper jaw 12 and the lower jaw 14 move toward one another. When the tightening screw 16, is turned in the opposite direction, the upper jaw 12 moves away from the lower jaw 14. The tightening screw 16 is actuated remotely using techniques known in the field, as the locking device is located inside a nuclear reactor. The tightening screw 16, once the desired torque has been applied, is prevented from turning by a reusable locking crimp (not shown) carried by the tightening screw 16. The locking crimp is of the type commonly known and used by those of ordinary skill in the art. The locking action of the crimp may be easily overcome if readjustment is required at a later time in the field. It will be appreciated that a force inducing member such as a spring loaded member may replace the tightening screw 16. One spring loaded member may be placed on both the upper jaw 12 and another on the lower jaw 14 such that compressive forces are generated at each of the upper jaw 12 and the lower jaw 14. As discussed below, the squeezing action of the compressive forces firmly holds the restraining ring 34 against the wedge 18, thus retaining the downcomer 11 in the desired position. OPERATION In order to secure the downcomer in position, the wedge 18 and restraining ring 34 are subjected to compressive forces induced on the upper jaw 12 and the lower jaw 14 by tightening the tightening screw 16. As the tightening screw 16 is turned to move the upper jaw 12 and the lower jaw 14 toward one another, the upper jaw 12 induces a downward force on the top surface 31 of the wedge 18. In turn, the compressive force on the lower jaw 14 induces an upward force on the bottom surface of the restraining ring 34. The compressive forces generated against the top of the wedge 18 and the bottom of the restraining ring 34 firmly hold the wedge 18 and restraining ring 34 in contact, forcing the wedge 18 against the downcomer 11 so as to lock the downcomer 11 in a desired position. In the embodiment shown, the compressive force on the lower jaw 14 creates an upward force on the bottom surface of the wedge 18, causing the wedge to move slightly upward. As the wedge 18 moves upward, the bottom surface 42 of the recess 40 contacts the restraining ring 34, forcing the restraining ring 34 against the wedge 18. Simultaneously, the tightening screw 16 causes a downward force on the upper jaw 12 that is transferred to the surface 31 of the wedge 18. Consequently, the wedge 18 moves slightly downward against the restraining ring 34. As a result, the upward motion of the restraining ring 34 is impeded by the downward motion of the wedge 18, resulting in the wedge 18 being pressed tight against the restraining ring 34. This arrangement creates a clamping action that frictionally engages the restraining ring 34, the wedge 18 and the downcomer 11, resulting in the downcomer 11 being secured in the desired position. There are a variety of configurations that may be employed to fabricate apparatus 10. Thus, the disclosed embodiment is given to illustrate the invention. However, it is not intended to limit the scope and spirit of the invention. Therefore, the invention should be limited only by the appended claims.
	description	FIG. 1 shows a fuel assembly according to the invention. The fuel assembly comprises an upper handle 1, a lower end portion 2, and a plurality of fuel units 3 stacked one above the other. Each fuel unit comprises a plurality of fuel rods 4 arranged in parallel and in a definite space relationship to each other in a given lattice, and a top tie plate 5 and a bottom tie plate 6 for attachment of the fuel rods in their respective positions in the lattice. The fuel units 3 are stacked on top of each other in the longitudinal direction of the fuel assembly and they are stacked in such a way that the top tie plate 5 in one fuel unit is facing the bottom tie plate 6 in the next fuel unit in the stack, and such that the fuel rods in all the fuel elements are parallel to each other. A fuel rod 4 comprises fuel in the form of a stack of pellets 7 of uranium arranged in a cladding tube 19. FIG. 2 shows a section II-IIxe2x80x2 through the fuel assembly in FIG. 1. The fuel assembly is enclosed in a fuel channel 8 with a substantially square cross section. The fuel channel is provided with a hollow support member 9 of cruciform cross section which is secured to the four walls of the fuel channel. In the central channel 14 formed by the support member 9, moderator water flows. The fuel channel with the support member surrounds four vertical channel-formed parts 10, so-called sub-channels, with an at least substantially square cross section. The four sub-channels each contain a stack of fuel units. Each fuel unit comprises 24 fuel rods 4 arranged in a symmetrical 5xc3x975 lattice. The fuel assembly in FIG. 2 comprises 10xc3x9710 fuel rod positions. By a fuel rod position is meant a position in the lattice. All the fuel rod positions in the lattice need not be occupied by fuel rods. In certain fuel assemblies, a number of fuel rods have been replaced by one or more water channels. The introduction of a water channel changes the number of fuel rods but not the number of fuel rod positions. FIG. 2a shows another embodiment of a fuel assembly according to the invention. The figure shows a horizontal section through the fuel assembly which is provided with an internally arranged vertical channel 14a through which water is conducted in a vertical direction from below and upwards through the assembly. The channel 14a is surrounded by a tube 9a with a substantially square cross section. The fuel units are kept in position by being fitted onto the tube which surrounds the vertical channel. FIG. 2b shows an additional embodiment of a fuel assembly according to the invention. The figure shows a horizontal section through the fuel assembly which is provided with two centrally arranged vertical water rods 9a and 9c through which water is conducted from below and upwards through the assembly. The water rods have a diameter which is somewhat larger than the diameter of the fuel rods and are designed with a substantially circular cross section. The fuel units are kept in position by being fitted onto the water rods. FIGS. 3a-3c show examples of what is meant by a substantially square cross section. The fuel assembly in FIG. 3a has a reduced corner portion 11. The fuel assembly in FIG. 3b has two reduced corner portions. The fuel assembly in FIG. 3c has four reduced corner portions. The reduction of a corner portion reduces the number of fuel rods in the fuel unit by one fuel rod compared with a fuel unit without a reduced corner portion. In a boiling water reactor, cooling water flows upwards through the fuel, whereby part of the water is transformed into steam. This results in a greater pressure drop in the upper part of the fuel assembly than in the lower part thereof. This difference gives rise to a force which tends to raise the fuel upwards. In conventional fuel assemblies, the fuel bundles are kept in position because of their weight. In a fuel assembly with short fuel units there is a risk of the upper fuel units being raised upwards by these forces. To prevent certain fuel units from being pressed upwards, a spring means 12 is arranged in the upper part of the fuel assembly. FIG. 4a shows a section IVA-IVAxe2x80x2 through the fuel assembly in FIG. 1. FIG. 4b shows in more detail the appearance of a spring means 12 in FIG. 1. The spring means 12 comprises a spiral spring 13 arranged in a slit in the support means 9 around the central channel 14. The spring 13 is provided with four radially extending arms 15, each of which presses down a stack of fuel units. This arrangement gives each stack of fuel units a freedom to grow in relation to the fuel channel independently of how the other stacks grow. Two types of growth occur in the fuel units, namely, thermal growth and irradiation growth. FIG. 5a shows another embodiment where the fuel units 3 are kept in position by being fitted onto a common supporting member. The common supporting member may, for example, be a tube 50a which conducts non-boiling water. The advantage of using one or more water-filled tubes as a common supporting element is that non-boiling water may be moved into the central parts of the fuel assembly and hence attain an improved moderation. The common supporting member may, for example, comprise a plurality of joined-together short fuel rods (50b) as shown in FIG. 5b. The advantage of allowing the supporting member to comprise a plurality of short fuel rods instead of one long fuel rod is that the previously mentioned risks in case of fuel damage are reduced. FIGS. 6a and 6b show another arrangement for keeping the fuel units in place. Two fuel units are connected to each other by four connecting springs 51 arranged between the top tie plate of the lower fuel unit and the bottom tie plate of the upper fuel unit. The connecting spring comprises an attachment loop 52, which may, for example, be of Inconel or some other nickel-base alloy. The connecting springs are easy to open such that the fuel units may change be rearranged or replaced during refuelling. The springs cannot be unintentionally opened when the bundle stands in the fuel channel or is being raised. FIG. 7 is a section VII-VIIxe2x80x2 through the fuel assembly in FIG. 1 and shows an example of a bottom tie plate 6. FIG. 8 shows the bottom tie plate in a section Dxe2x80x94D in FIG. 7. The bottom tie plate comprises an orthogonal latticework composed of tubular sleeves 16, 17 and surrounded by a frame 18. The function of the frame 18 is to guide the fuel units when charging the fuel, keep the fuel rods at a certain distance from the fuel channel 8, and to scrape off water from the walls of the fuel channel, especially in the upper part of the channel. The frame is provided with guiding vanes l9a, the function of which is two-fold, namely, to facilitate the introduction of the fuel unit into the cladding tube, and to increase the mixing of cooling flow. The sleeves are of two different types, namely, fixing sleeves 16 in which the fuel rods 4 are fixed, and supporting sleeves 17 which support and fix the fixing sleeves. The fixing sleeves have the same or almost the same diameter as the cladding tube of the fuel rods. The fixing sleeves are arranged in a symmetrical 5xc3x975 lattice which corresponds to the lattice of the fuel rods, and the supporting sleeves are arranged between the fixing sleeves to support these. The supporting sleeves 17 may be provided with mixing vanes 19b to increase the mixing of the coolant flow. The mixing should primarily be performed in the upper part of the fuel assembly, where the risk of dryout is greatest. The fuel assembly preferably comprises two types of fuel units, of which one type has bottom tie plates with mixing vanes and the other type has bottom tie plates with no mixing vanes. The fuel units whose bottom tie plates have mixing vanes are arranged in the upper part of the fuel assembly and those without mixing vanes are arranged in the lower part of the fuel assembly. The top tie plate 5 may be designed as the bottom tie plate described above. The frame of the top tie plate is suitably provided with a marking for identification of the respective fuel unit. The top tie plate shall also be capable of being gripped by a lifting tool. FIG. 8 shows how the fuel rods 4 are attached to the top tie plate 5 and to the bottom tie plate 6. In the lower part of the fuel rod 4, a bottom plug 20 is arranged, the free end of which is inserted into the fixing sleeve 16 in the bottom tie plate 6. In the uppermost part of the fuel rod, a top plug 21 is arranged, the free end of which is inserted into a fixing sleeve 22 in the top tie plate 5. During the burnup of the nuclear fuel, fission gases contained in the fuel rod are released. To prevent the pressure on the cladding from becoming too great, an expansion space for the fission gases is needed. The bottom plug 20 is provided with a cavity 23 to receive fissile gases, and that part of the bottom plug which faces the uranium pellets has an opening between the cavity and the remainder of the fuel rod. In the upper part of the fuel rod, the stack of uranium pellets ends somewhat below the top plug 21 which is provided with a cylindrical recess 25, the opening of which faces the uranium pellets. The space between the top plug and the uranium pellets and the space in the top plug may be utilized for expansion of the fissile gases. The uranium-free parts of the fuel rods give a reduced neutron absorption, which leads to an increase of the effect in the uranium pellets nearest the top and bottom plugs. To reduce the effect and to further increase the space for the fission gases, uranium pellets with holes may preferably be used nearest the top and bottom plugs. It may also be suitable to give these pellets a lower enrichment. It is important that the emission of fission gases be kept at a low level, such that the required fission space becomes as small as possible. This is achieved by a low linear rod load (kW/m) which is made possible by a large number of fuel rods (96 in the embodiment) in the highly loaded cross section of the assembly. An additionally larger number of rods may also be advantageous. The number of fuel rod positions should at least be 80, preferably more than 90, for the fission gas emission to be sufficiently low to be taken care of in the short fuel units. The fission gas emission may be further reduced by additions to the fuel pellets. A fuel unit comprises a small number of, for example two, retaining fuel rods which are fixed to the top tie plate and the bottom tie plate. The retaining fuel rods retain the fuel unit such that the other fuel rods are kept in position. FIG. 9a shows how a retaining fuel rod 4a may be fixed to the fixing sleeve 16 of the bottom tie plate with a cleaving rivet 26. FIG. 9b shows a section IXB-IXBxe2x80x2 in FIG. 9a. FIG. 10 shows how a retaining fuel rod 4b may be fixed to the fixing sleeve 16 with a screw joint 27. In a conventional fuel assembly, with full-length fuel rods, which are retained by a plurality of spacers along their axial length, abrasion damage normally arises on a level with the spacers because debris adhering thereto remain and wear holes in the cladding. Because no spacers are needed in a fuel assembly according to the invention, the risk of abrasion damage to the fuel is reduced. However, a risk of abrasion damage remains in the region below the top tie plate. FIGS. 11a-11c show different alternatives for reducing the risk of cladding damage caused by abrasion in this region. Because the rods need not be drawn through spacers during mounting, a larger outer diameter may be allowed in this region, for example by a wear-resistant coating. FIG. 11a shows a top plug 33 which has an upper solid part 34, for connection to the fixing sleeve 22 in the top tie plate, and a lower solid 35. The lower part 35 is longer than the upper part 34. The lower part is arranged in the region with the greatest risk of abrasion damage. FIG. 11b shows a top plug 28 which has an upper solid part 29 and a lower hollow part 30. The lower part 30 is longer than the upper part 29 and is provided with a coating 31 which protects against abrasion damage, for example zirconium oxide or aluminium oxide. FIG. 11c shows a fuel rod, the cladding tube 19 of which in its upper part, where the risk of abrasion damage is greatest, is provided with a coating 32 protecting against abrasion damage. For several different reasons, it is desirable to reduce the amount of uranium in the upper part of the fuel assembly in a fuel assembly intended for a boiling water reactor. One reason is that the high percentage of steam in the upper part of the fuel assembly leads to deteriorated neutron moderation, which results in the fuel not being burnt up as quickly in the upper part of the fuel assembly as in the lower part thereof. Another reason is that a reduction of the quantity of uranium in the upper part of the fuel assembly gives an improved shut-down margin. A consequence of the reduction of the quantity of uranium is that the free flow area increases, which leads to a reduction of the pressure drop in the upper part of the fuel assembly, and, therefore, the risk of thermohydraulic instability in the fuel assembly decreases. In a fuel assembly according to the invention, the quantity of uranium in different parts of the assembly may be varied in a simple manner. A fuel assembly may comprise fuel units with different numbers of fuel rods, different lattice configurations, and different fuel rod diameters. FIG. 12 shows a fuel assembly 39 which comprises fuel units (40, 41) of two different types, of which the first type contains fuel rods with a first diameter and the other type contains fuel rods with a second diameter. The first type of fuel units 40 is arranged in the lower part of the fuel assembly, and the second type of fuel units 41 is arranged in the upper part of the fuel assembly. The fuel rods in the lower fuel units 40 have a diameter which is larger than that of the fuel rods in the upper fuel units 41. FIG. 13 shows a fuel assembly 42 where the number of fuel rods in the fuel units 43 in the lower part of the fuel assembly is larger than the number of fuel rods in the fuel units 44 in the upper part of the fuel assembly. The number of axial zones with different rod diameters or different number of rods may, of course, be greater than the two shown in the examples. It is also possible to have different rod diameters within the fuel units to attain optimum properties in the cross section. A fuel assembly according to the invention may comprise fuel units with different height. FIG. 14a shows a fuel assembly which comprises eight equally long fuel units 60. FIG. 14b shows a fuel assembly which comprises eight fuel units with two different heights. The uppermost four fuel units 61 are shorter than the lowermost four fuel units 62. Since the top tie and bottom tie plates give rise to turbulence of the cooling water, it is advantageous, from the point of view of dryout, to have more top tie and bottom tie plates in the upper part of the fuel assembly than in the lower part thereof, which is achieved in this embodiment. FIG. 14c shows ten equally high fuel units 63. FIG. 14d shows five equally long fuel units 64, each one comprising a spacer 65 which keeps the fuel rods spaced-apart from each other and prevents them from bending or vibrating when the reactor is in operation. FIG. 15a shows an example of a fuel assembly where the fuel units 69 in the upper part and the fuel units 68 in the lower part of the fuel assembly have different lattices. FIG. 15b shows a cross section through the fuel unit 69, and FIG. 15c shows a cross section through the fuel unit 68. The number of fuel rods is larger in the fuel units in the lower part of the fuel assembly than in the fuel units in the upper part thereof. It is also possible to omit rods in occasional lattice positions, preferably in the uppermost fuel units. A fuel assembly according to the invention may also be optimized by the enrichment of uranium in the fuel rods varying between the different fuel units. Fuel units in the upper part of the fuel assembly may, for example, have a lower enrichment than fuel units in the lower part of the fuel assembly. The occurrence of burnable absorbers, for example gadolinium, may also vary between the fuel units. Recently, the development has gone towards fuel assemblies with narrower fuel rods which are more in number. However, there is a limit to how narrow the rods may be if they are to have a length of about four meters. If the rod is too narrow, mechanical difficulties arise which may become very difficult to solve. A solution to these problems is to manufacture short fuel units. FIG. 16 shows a cross section of a fuel assembly with 12xc3x9712 fuel rod positions. The rod diameter is about 8 mm. With a plurality of rods, the linear load and hence the fission gas emission are reduced. The need of space for fission gas in the short rods is thus reduced, which facilitates such a design. A fuel assembly with short fuel units has several advantages compared with a traditional fuel assembly with full-length fuel rods. One considerable advantage is the flexibility provided in designing the fuel assembly. This means that the fuel assembly in a simple manner may be optimized both in the axial direction and in the radial direction, for example with respect to lattices and fuel distribution. In connection with refuelling, certain fuel units may be replaced and certain may be allowed to remain in the fuel assembly. The fuel units which are allowed to remain in the fuel assembly may be given a new position. In this way, the service life of the fuel assembly increases. If the height of the fuel units is sufficiently low, no spacers are needed, which is an advantage since the spacers increase the risk of abrasion damage. It is also easy to design the upper end of the rods with special abrasion protection in the sensitive region below the top tie plates. The consequence of abrasion damage or other cladding damage is reduced as the length of the fuel rods is reduced, since the quantity of uranium and fission products which may leak out is smaller. The risk of secondary damage is also reduced for short rods. To achieve the above-mentioned advantages, the number of fuel units on top of each other may be at least three, preferably even more. To avoid using spacers, the number of fuel units should be more than six.
	abstract	A reflective mirror is provided with a base and a multilayer film including a first layer and a second layer laminated alternately on the base and capable of reflecting at least a portion of incident light. The multilayer film is provided with a first portion having a first thickness, and with a second portion having a second thickness that is different from the first thickness, and which is provided at a position rotationally symmetric to that of the first portion about an optical axis of the reflective mirror.
042749760	description	The present invention is further illustrated, by way of example only, in the following Examples. EXAMPLE 1 A mixture of oxides as set out in Column A of Table 4 above is selected to correspond to a desired mineral assemblage: perovskite CaTiO.sub.3, Ba felspar BaAl.sub.2 Si.sub.2 O.sub.8, hollandite BaAl.sub.2 Ti.sub.6 O.sub.16, kalsilite KAlSiO.sub.4, and zirconolite CaZrTi.sub.2 O.sub.7. Ninety percent by weight of this mixture is intimately mixed with 10 percent of HLW calcine (Table 1.) The combined mixture is then melted in a suitable furnace at about 1330.degree. C. under mildly reducing conditions and allowed to cool over a period of 2 hours to a temperature of 1100.degree. C., at which stage essentially complete solidification is achieved. The resultant product is found to be well-crystallized and composed mainly of the 5-phase mineral assemblage: perovskite-hollandite-Ba felsparzirconolite-kalsilite. However, because of the partial substitution of potassium for barium in the hollandite lattice, and the non-stoichiometry of the hollandite phase, crystallization occurs during cooling in such a direction that the residual liquids are enriched in potassium, barium and silica. From this residual liquid, a K-Ba-aluminosilicate possessing the leucite structure is observed to crystallize. Compositions of these phases as determined by electronprobe microanalyses are given in Table 5. The distribution of HLW elements among the major phases of the mineral assemblage of Example I has been determined by electronprobe microanalyses of coexisting phases. It is found that the rare earths and actinide elements dominantly enter the perovskite and zirconolite phases to form stable solid solutions, whilst molybdenum and ruthenium likewise enter the perovskite and hollandite phases replacing titanium providing that the synthetic rock composition is melted under appropriate redox conditions. Strontium is found to become preferentially incorporated in the perovskite phase, whilst barium enters the Ba felspar, and to a lesser degree, the hollandite phase. Rubidium mainly substitutes for potassium in the leucite phase, in the KAlSiO.sub.4 phase and also in the Ba felspar phase. Zirconium enters the zirconolite phase whilst palladium becomes reduced to the metallic state. During crystallization of the mineral assemblage, caesium tends to become enriched in the residual liquid, and finally becomes incorporated mainly in the leucite phase and/or in a (K,Cs)AlSiO.sub.4 solid solution which possesses the RbAlSiO.sub.4 structure. Some caesium is also found to occur in solid solution in Ba felspar. EXAMPLE 2 A mixture of oxides is selected so that when the mixture is heated, the oxides combine together to form a mineral assemblage consisting of BaAl.sub.2 Ti.sub.6 O.sub.16 hollandite (25%), CaZrTi.sub.2 O.sub.7 zirconolite (20%), BaAl.sub.2 Si.sub.2 O.sub.8 barium felspar (20%, CaTiO.sub.3 perovskite (15%) and KAlSi.sub.2 O.sub.6 leucite (20%). Ninety percent of this mixture is intimately mixed with 10 percent of HLW calcine (Table 1), and the combined mixture is then heat-treated under reducing conditions as described in Example 1. The resultant product is found to be well-crystallized and composed mainly of the 5-phase mineral assemblage: perovskite-hollandite-Ba felspar-zirconolite-leucite. The distribution of the HLW elements among coexisting phases is similar to Example 1 except that nearly all of the caesium is found in solid solution in the leucite-type phase as a KAlSi.sub.2 O.sub.6 -CsAlSi.sub.2 O.sub.6 solid solution. EXAMPLE 3 A mixture of oxides is selected so that when the mixture is heated, the oxides combine together to form a mineral assemblage consisting of BaAl.sub.2 Ti.sub.6 O.sub.16 hollandite (25%), CaZrTi.sub.2 O.sub.7 zirconolite (20%), BaAl.sub.2 Si.sub.2 O.sub.8 barium felspar (20%), CaTiO.sub.3 perovskite (15%) and NaAlSiO.sub.4 nepheline (20%). Ninety percent of this mixture is intimately mixed with 10 percent of HLW calcine (Table 1) and the mixture is then heat treated under reducing conditions as described in Example 1. The resultant product is found to be well-crystallized and composed mainly of the 5-phase mineral assemblage: perovskite-hollandite-Ba felspar-zirconolite-nepheline. The distribution of HLW elements among coexisting phases is similar to Example 1 except that nearly all of the caesium is found in the nepheline phase. EXAMPLES 4,5 and 6 Mixtures of oxides are selected as described in Examples 1, 2 and 3, respectively and 95 percent of each oxide mixture is intimately mixed with 5 percent of HLW calcine (Table 1). Each mixture is then heat treated under reducing conditions as described in Example 1. The products are found to correspond essentially to the mineral assemblage described in Examples 1, 2 and 3 respectively. EXAMPLES 7, 8 and 9 Mixtures of oxides are selected as described in Examples 1, 2 and 3, respectively, and 80 percent of each oxide mixture is intimately mixed with 20 percent of HLW calcine (Table 1). Each mixture is then heat treated under reducing conditions as described in Example 1. The products are found to correspond essentially to the mineral assemblages described in Examples 1, 2 and 3 respectively. EXAMPLE 10 A mixture of oxides as set out in Column B of Table 4 hereinbefore is selected so that when the mixture is heated, the oxides combine together to form a mineral assemblage consisting of BaAl.sub.2 Ti.sub.6 O.sub.16 hollandite, CaZrTi.sub.2 O.sub.7 zirconolite and CaTiO.sub.3 perovskite. Ninety percent of this mixture is intimately mixed with 10 percent of HLW calcine (Table 1). The combined mixture is then heated to about 1300.degree. C. for about half an hour in the presence of metallic nickel and simultaneously subjected to a confining pressure (e.g. 1000 atmospheres) using the conventional technique known as "hot-pressing". The resultant product is found to be a fine grained, mechanically strong assemblage of hollandite, zirconolite and perovskite possessing the above compositions. The distribution of HLW elements among the major phases of the mineral assemblage of Example 10 has been determined by electronprobe microanalyses of coexisting phases and is summarised in Table 6 hereinafter. It is found that caesium enters the hollandite phase as Cs.sub.2 Al.sub.2 Ti.sub.6 O.sub.16, strontium dominantly enters perovskite as SrTiO.sub.3 and the actinide elements dominantly enter the zirconolite phase, in each case, forming dilute solid solutions. Samples of the product of Example 10 have been subjected to leaching tests by pure water and by water--10% NaCl solution at high temperatures and pressures. It has been found that the mineral assemblage remains stable and caesium remains incorporated in hollandite when subjected to leaching at temperatures up to 900.degree. C., combined with pressure up to 5 kilobars over a period of 24 hours. For comparison, a representative selection of borosilicate glasses devitrified and disintegrated at temperatures above 350.degree. C. Moreover, the alternative crystalline waste form "Supercalcine" was found to exchange its caesium for sodium at temperatures above 400.degree. C. These experiments demonstrate the remarkable stability of the product of the present invention and its superiority over other immobilisation forms. TABLE 6 ______________________________________ "Hollandite" Zirconolite Perovskite ______________________________________ Cs.sup.+ Mo.sup.4+ U.sup.4+ Sr.sup.2+ Rb.sup.+ Ru.sup.4+ Th.sup.4+ REE.sup.3+ K.sup.+ Rh.sup.3+ Pu.sup.4+ Y.sup.3+ Na.sup.+ Fe.sup.3+ Cm.sup.4+ Am.sup.3+ Ba.sup.++ Cr.sup.3+ Am.sup.3+ U.sup.4+ Pb.sup.++ Ni.sup.2+ Y.sup.3+ Th.sup.4+ Fe.sup.2+ REE.sup.3+ Cm.sup.4+ Na.sup.+ Pu.sup.4+ ______________________________________ Table 6 is a summary of observed preferential distributions of HLW elements in solid solution in phases of the mineral assemblage of the composition given in Column B, Table 4, produced in accordance with Example 10. The quadrivalent actinides are more strongly partitioned into the zirconolite phase than into perovskite. Trivalent actinides preferentially enter zirconolite; however, in the presence of somewhat higher Al.sub.2 O.sub.3 concentrations than shown in Table 4, Column B, the trivalent actinides may instead preferentially enter the perovskite phase. EXAMPLE 11 The procedure of Example 10 is repeated except that the proportion of mixed oxide additives to HLW calcine is 80 to 20 by weight. The product is a mineral assemblage essentially similar to the product of Example 10. EXAMPLE 12 The procedure of Example 10 is repeated except that the proportion of mixed oxide additives to HLW calcine is 95 to 5 by weight. Again, the product is a mineral assemblage essentially similar to the product of Example 10. EXAMPLE 13 A mixture of oxides is selected so that when the mixture is heated, the oxides combine together to form a mineral assemblage consisting of BaAl.sub.2 Ti.sub.6 O.sub.16 hollandite (50%) and CaZrTi.sub.2 O.sub.7 zirconolite (50%), the actual composition of the minerals resembling those in Table 5, Columns G and I. From 5 to 20 percent of HLW calcine is then intimately mixed with 95 to 80 percent of the above oxide mixture and the combined mixture heat-treated as in Example 10. It is found that nearly all actinide elements in the HLW enter the zirconolite whilst strontium becomes partitioned between hollandite and zirconolite, mostly entering zirconolite. Other HLW elements including caesium enter the hollandite as in Example 10. EXAMPLE 14 A mixture of oxides is selected so that when the mixture is heated, the oxides combine together to form a mineral assemblage consisting of BaAl.sub.2 Ti.sub.6 O.sub.16 hollandite (50%) and CaTiO.sub.3 perovskite (50%), the actual compositions of these minerals resembling those in Table 5, Columns G and H. From 5 to 20 percent of HLW calcine is then intimately mixed with 95 to 80 percent of the above oxide mixture and the combined mixture heat-treated as in Example 10. It is found that the actinide elements and strontium in the HLW enter the perovskite, whilst caesium and the other elements of the HLW continue to enter the hollandite as in Example 10. EXAMPLE 15 The procedures of Examples 10-12 and 14 are repeated except that CaTiO.sub.3 perovskite is replaced by SrTiO.sub.3 perovskite. EXAMPLE 16 The procedures of Examples 10-14 are repeated except that CaTiO.sub.3 perovskite is replaced where present by SrTiO.sub.3 perovskite, and BaAl.sub.2 Ti.sub.6 O.sub.16 holandite is replaced by SrAl.sub.2 Ti.sub.6 O.sub.16 hollandite. The above Examples 1 to 16 demonstrate how the HLW elements in HLW calcine can be firmly incorporated in stable solid solutions within the minerals of an appropriately selected assemblage. The product of each Example containing the immobilized HLW elements can be safely buried in an appropriate geological-geochemical environment. The results obtained from investigation of mineral assemblages produced in accordance with this invention demonstrate that when HLW products are treated by the processes described herein, they can safely be confined for periods of millions of years. By such means, the biosphere can be protected from the radiologic hazards posed by high level wastes from nuclear reactors. The compositions of two other crystalline ceramic waste forms proposed for nuclear waste immobilisation have been given above in Table 4, Columns C and D. It is seen that the compositions and mineralogies of these ceramic waste forms differ drastically from those of the mineral assemblages comprising the synthetic rock described in this invention. It should also be noted that in the waste forms designated in columns C and D, caesium is present as the mineral pollucite. This mineral readily loses its caesium when subjected to the action of aqueous solutions containing sodium at temperatures above 300.degree. C. In comparison, caesium remains firmly incorporated in hollandite-type mineral phases at temperatures up to 900.degree. C. under otherwise similar conditions. It will be appreciated by persons skilled in this art that many modifications and variations may be made to the specific embodiments described herein without departing from the spirit and scope of the present invention as broadly described herein.
	abstract	A radiation image acquisition system of an aspect of the present invention includes a radiation source emitting radiation toward an object, a holding unit holding the object, a wavelength conversion member generating scintillation light in response to incidence of the radiation emitted from the radiation source and transmitted through the object, a first imaging means condensing and imaging scintillation light emitted from an incidence surface of the radiation of the wavelength conversion member, a second imaging means condensing and imaging scintillation light emitted from a surface opposite to the incidence surface of the wavelength conversion member, a holding unit position adjusting means adjusting the position of the holding unit between the radiation source and the wavelength conversion member, and an imaging position adjusting means adjusting the position of the first imaging means.
	summary
	abstract	A method of inspecting an operation of sealed closure by welding an end opening of a filling channel axially traversing an upper plug for closing the cladding of a fuel rod for a nuclear reactor, the cladding of the rod containing a plurality of pellets of nuclear fuel stacked in the axial direction of the cladding and two closure plugs, one of the plugs or the upper plug being traversed axially by the channel for filling the cladding of the rod with an inert gas and the sealed closure by welding of the filling channel of the upper plug being carried out after filling the cladding with inert gas, in a filling apparatus, by melting central part of the end of the upper plug adjacent to the opening of the filling channel, this method allowing for inspection of the conditions for implementing and carrying out the sealed closure of the upper plug by welding, efficiently and without extending the time needed for the manufacture of the fuel rod.
041707540	description	DESCRIPTION OF THE PREFERRED EMBODIMENT While numerous applications of the invention exist, including the monitoring of liquid levels, the preferred embodiment chosen for illustrating the flexible position probe assembly and associated electronics is that of a nuclear reactor application as illustrated in FIG. 1, wherein the flexible position probe assembly 10 responds to the movement of lead screw L to develop an output signal indicative of the position of control rod R. The position probe assembly 10 is installed in a non-magnetic thimble T, typically stainless steel, within the control rod drive mechanism (CRDM) D of the nuclear reactor assembly N. The lead screw L, to which the actual control rod R is attached, is constructed of a magnetically permeable material such as steel. The lead screw L is hollow and moves upwards and downwards over the thimble T as the control rod R is raised and lowered relative to the reactor core C. As discussed above, the flexible position probe assembly 10 consists of a plurality of differential transformer core sections S, each including primary and secondary windings. The primary windings of the sections S respond to excitation current from an AC source 39 by generating a magnetic flux field which is engaged by that portion of the lead screw L adjacent to core sections. With the control rod R fully inserted in the reactor core C as illustrated, the lead screw L couples only the lower sections S of the probe assembly 10. By design, with the control rod R fully raised, all differential transformer core sections S of the probe assembly 10 would be coupled by the lead screw L. Thus, the output signal supplied from the flexible probe assembly 10 to the signal processing circuitry 40 is in direct relation to the change in transformer coupling produced by the movement of lead screw L and is thus an actual indication of the position of control rod R. The signal processing circuitry responds to the output signals from the flexible position probe assembly 10 by transmitting digital signals to digital indicator 60 which provides a direct numerical indication of the position of control rod R. The flexible probe assembly as described above is pictorially represented in FIG. 2 wherein the flex capability of the probe is clearly apparent. A flat flexible band or strip 12, typically constructed from spring steel, is inserted through a plurality of tubular differential transformer core sections S with the electrical leads associated with the respective primary and secondary windings exiting through the internal passages defined in the core sections S by the flexible band 12 for termination at electrical terminal 36. The combination of cable 37 and electrical connection 38 provides electrical connection between the probe assembly 10 and the signal processing circuitry 40. Spring member 14 positioned between electrical terminal assembly 36 and the uppermost core section S1 permits displacement of the relative core section S along the flexible band 12 during flexing of the probe assembly 10. Referring to FIGS. 3-9, there is illustrated the components comprising the core sections S and the combination of the core sections S with the flexible band 12 to form the flexible position probe assembly 10. The core sections S consist of a tubular spool 20, typically constructed of annealed stainless steel having uniform permeability, having end flanges 21 and 22 and a tubular member 23 extending therebetween. The outside surfaces of the end flanges 21 and 22 are beveled, as shown, such that adjacent core sections S, as illustrated in FIG. 3, are free to move with respect to one another in response to the flexing action of the probe assembly 10. The primary winding 25 and the secondary winding 26 of each core section are wound on appropriate coil retainers 24 for positioning on the spool member 23, as shown in FIG. 3. The spool member 23 further includes longitudinal grooves 27 which are broached into the interior surface of the tubular spool member 23 in order to accommodate the flexible strip 12. The insertion of the flexible strip 12 through the core sections S as illustrated in FIGS. 3, 4 and 9 defines the internal probe passages P1 and P2. Apertures 27 and 28 in the tubular member 23 of each spool 20 provide communication with internal passages P1 and P2, respectively. The electrical leads associated with each of the primary windings 25 of the core sections S extend through interior passage P1 to the electrical connector 36 of FIG. 2, while the electrical leads associated with the secondary windings 26 of the core sections S extend through internal passage P2 to the electrical terminal 36. In an application where it is desired to measure the position or displacement of an object such as the control rod R in 1/2 inch increments, the length dimension of the core sections S which corresponds to the length dimensions of the spools 20 would be 1/2 inch, as indicated in FIG. 3. Needless to say, this dimension can be varied as dictated by a particular application. The design of the spool 20 is illustrated in detail in FIGS. 5 and 6. The assembly of a core section S, comprising a pair of coil retainers 24, as illustrated in FIG. 7, accommodating the primary and secondary windings 25 and 26, is accomplished as illustrated in the exploded view of FIG. 8. End flange 21 is force-fitted onto tubular element 23, as illustrated in FIGS. 5 and 8 and the coil retainers 24 for primary and secondary windings 25 and 26 are slid onto the tubular member 23 and the end flange 22 is then secured in a force-fitting relationship with the tubular member 23 to produce a core section S. The ends of the primary winding 25 and the secondary winding 26 extend through a wall of the respective retainers 24 to terminals 31. The primary lead wires LP and the secondary lead wires LS, as illustrated in FIG. 3, are then fed through apertures 28 and 29 in the tubular element 23 for termination at the appropriate coil terminals 31. The use of the coil retainers 24 is a matter of convenience. They can be fabricated from any suitable material such that the primary and secondary coil windings of appropriate number of turns can be assembled as a separate component, as illustrated in FIGS. 7 and 8, for ease of assembly to form core sections S. The interconnection of the primary and secondary windings of the respective core sections S can be such as to satisfy desired electrical operation. In the embodiment illustrated, the primary windings of adjacent core sections S are connected in a series arrangement, while the secondary windings 26 are interconnected in sets of parallel combinations, as will be discussed hereinafter. The design of the independent core sections S and the mechanical combination of the core sections S with the flexible strip 12 provide a flexible position probe assembly 10 capable of developing digital output position indication substantially independent of ambient magnetic fields, temperature variations and changes in line voltage and frequency. The degree and radius of the flex capabilities of the position probe assembly is a function of the characteristics of the flexible strip 12, the length of the respective core sections S and the overall length of the position probe assembly 10. The beveled design of the adjacent contacting surfaces of the spools 20 support flexing of about 10.degree. between any two adjacent core sections S. A position probe assembly of 24 inches in length will typically permit flexing of the probe assembly into an arc defining a radius of less than 15 inches. This flex characteristic of the position probe assembly 10 permits installation of the position probe assembly 10 in applications, i.e., such as the nuclear reactor application of FIG. 1, wherein the overhead clearance is less than the required length of the position probe assembly. The mode of operation of the position probe assembly 10 is illustrated in FIGS. 10 and 11 wherein the individual core sections S which comprise differential transformers, develop an output signal at the secondary winding which varies in response to magnetic coupling and decoupling occurring between the core sections S and the lead screw L, as the lead screw L moves in combination with the control rod R. The output signal resulting from the predetermined electrical combination of the secondary windings of the core sections S is supplied through signal processing circuitry 40 to digital indicator 60 to manifest the position of control rod R. In the embodiment illustrated in FIGS. 10 and 11 the primary windings 25 are connected in series with alternative reversed polarity so as to generate a number of individual magnetic fields with alternate polarization along the length of the probe assembly 10. Assuming that the core sections S are each approximately 1/2 inch in length, then the alternating polarized fields will be approximately 1/2 inch in length. The secondary coils 26 are connected in a series-parallel pattern to generate four independent outputs, which together form a phase encoded digital signal in Gray code. The number of series group and thus the number of independent outputs forming the signal is merely a design choice. Each series-connected group G of secondary windings 26, as schematically illustrated in FIG. 11, consists of an even number of alternately opposite polarized coils, forming a large differential transformer. While the number of turns for the primary and secondary windings of each group is a function of design choice and the permeability of the control rod drive mechanism D, the number of turns per primary winding is identical, i.e., 40, while the number of turns per secondary winding, with the exception of either the bottommost or uppermost secondary winding in each series group of secondary windings, is also of an equal number of turns, i.e., 80 turns. If the secondary winding of the lowermost core section S" in a group G is selected to have a different number of turns than the remaining secondary windings of the group G, the fact that the secondary winding or lowermost core section S" will be the first in the respective group to be coupled by the lead screw L and the last to be decoupled, a number of turns less than 80, such as 65 turns, will provide the appropriate phase change in the output signal developed by the group G in response to movement of the lead screw L. In the event the secondary winding associated with the uppermost core section S' of the group G of FIG. 10 is selected to consist of a different number of turns from the remaining secondary windings of the group G, the number of turns associated with the secondary winding of the core section S' is typically greater than 80 turns, i.e., 100 turns, inasmuch as core section S' is the last to be coupled by the lead screw L as it advances upward and the first to be decoupled by the lead screw L as the lead screw retracts. The phase and magnitude of the respective voltages developed by the secondary winding of the core section S' with respect to secondary windings of the remaining core sections is such as to develop an output signal from the group G which serves as a phase encoded output which combines with the output voltages developed by the remaining three groups to form a Gray code output from the probe assembly 10. This latter arrangement, wherein the uppermost core section S' of the respective groups of series connected secondary windings is chosen for the purposes of illustrating and describing the disclosed embodiment of the invention. The Gray code is a unit-increment code, sometimes also referred to as the cyclic code or the reflected-binary code. Gray codes, which have the characteristic of changing the state of only one bit from one numeral to the next, are used extensively in position encoders because the maximum reading error during the transition from one incremental position to the next is the adjacent numeral. If a coventional binary 8 4 2 1 code were used for position and coding, all bits to be changed must change at precisely the same position to avoid large error outputs during such transitions as 3 to 4 and 7 to 8. This precision usually imposes unreasonable mechanical tolerances in the fabrication and assembly of position monitoring devices such as the probe assembly 10. Detail discussion of Gray codes and techniques for converting Gray codes to binary code are presented in the following published texts: "Electronic Analog/Digital Conversions", by Hermann Schmid; Van Nostrand Reinhold Company (1970); "Analog-to-Digital/Digital-to-Analog Conversion Techniques", by David F. Hoeschele, Jr.; John Wiley and Sons, Inc. (1968); "Digital Electronics for Scientists", by H. V. Malmstadt and C. G. Enke; W. A. Benjamin, Inc. (1969). A comparison of a conventional Gray code with a conventional pure binary code as presented on page 305 in the above-described text "Electronic Analog/Digital Conversions" is given in the following table: ______________________________________ +7 1 0 0 0 0 1 1 1 +6 1 0 0 1 0 1 1 0 +5 1 0 1 1 0 1 0 1 +4 1 0 1 0 0 1 0 0 +3 1 1 1 0 0 0 1 1 +2 1 1 1 1 0 0 1 0 +1 1 1 0 1 0 0 0 1 0 1 1 0 0 0 0 0 0 -1 0 1 0 0 1 1 1 1 -2 0 1 0 1 1 1 1 0 -3 0 1 1 1 1 1 0 1 -4 0 1 1 0 1 1 0 0 -5 0 0 1 0 1 0 1 1 -6 0 0 1 1 1 0 1 0 -7 0 0 0 1 1 0 0 1 -8 0 0 0 0 1 0 0 0 ______________________________________ Decimal Gray Code Pure-Binary Code (two's complement) ______________________________________ The individual core sections S of the probe assembly illustrated in FIGS. 10 and 11 represent individual transducers which can be considered as transformers with relatively poor coupling to the secondary windings. In the absence of coupling by the lead screw L, each of the transducers represented by the core sections S exhibits a minimum coupling coefficient K.sub.min, i.e., 0.06 whereas coupling of the core sections S by the lead screw L increases the coupling coefficient to K.sub.max, i.e., 0.09. The K.sub.min and K.sub.max coupling coefficients are actually analog equivalent coupling coefficients derived from a number of adjacent core sections. Since the end core sections of the group G do not have adjacent core sections on both sides, their coupling coefficient differs slightly from that of a core section in the middle of the group G. In the embodiments of FIGS. 10 and 11, N.sub.1 represents the turns of the secondary windings of the group G with the exception of the uppermost core section S' wherein the turns of the secondary winding shall be identified as N.sub.2. The turns N.sub.pri of the series connected primary windings 25 of the group G are excited with a constant AC current supplied by AC source 39. Referring to FIG. 11, the even number of secondary windings comprises the group G are schematically illustrated in a series-opposition arrangement wherein the turns N.sub.2 of the secondary winding of the uppermost core section can be expressed in terms of the turns N.sub.1 of the other secondary windings in the group G as follows: EQU N.sub.2 =N.sub.1 /2 (K.sub.max /K.sub.min +1) When the lead screw L is totally retracted and thus provides no coupling of the lowermost core section S" of the group G, a minimum coupling condition exists for the group G wherein the resultant phase voltage V.sub.R, which is depicted in the phasor diagram of FIG. 12A, can be represented as: EQU V.sub.R =N.sub.1 /2 (K.sub.max -K.sub.min) For the purposes of discussion it will be assumed that this resultant phase voltage is positive and corresponds to a logic 0. When the lead screw L advances to couple the lowermost core section S" of the group G, the resultant phase voltage V.sub.R, which is illustrated in the phasor diagram of FIG. 12B, can be represented as: EQU V.sub.R =-N.sub.1 /2 (K.sub.max -K.sub.min) This negative resultant phase voltage V.sub.R occurring when the lowermost core section S" is coupled by the lead screw L corresponds to a logic 1. As the lead screw L continues to advance and sequentially couples adjacent core sections, the resultant output voltage alternates between a logic 0 and a logic 1 as described above. With the selection of an even number of core sections and corresponding secondary windings in the group G, when the lead screw L couples the uppermost core section S', the resultant voltage V.sub.R, which is developed in accordance with the phasor diagram of FIG. 12C, is positive, thus corresponding to a logic 0, and can be represented as follows: EQU V.sub.R =N.sub.1 /2 (K.sub.max /K.sub.min) (K.sub.max -K.sub.min) A simplified schematic illustration of the interconnection of primary and secondary windings of core sections S comprising a probe assembly in accordance with the teachings of this invention is illustrated in FIG. 13A, while the corresponding four bit Gray code is presented in the truth table of FIG. 13B. Inasmuch as the output signal developed by the position of assembly 10 is a phase related signal, and not a parameter of any analog signal strength, the operation of the position probe assembly 10 is substantially independent of line voltage and frequency variations and, in a nuclear reactor application, such a probe is substantially independent of reactor operating temperature fluxations. There are numerous techniques known in the art for implementing the operation of signal processor circuit 40 to convert the Gray code output of the probe assembly 10 to a binary coded decimal suitable for digital display of the position of lead screw L in the digital indicator circuit 60. Typical techniques for converting Gray code information into binary code information are disclosed on page 313 of the above-referenced text "Electronic Analog/Digital Conversions" and page 335 of the above-referenced text "Analog-to-Digital/Digital-to-Analog Conversion Techniques". An implementation of typical circuitry to satisfy the operation of the signal processor circuit 40 is schematically illustrated in FIG. 14. The signal processing circuitry 40 consists of a drive circuit 42, four identical signal processing channels 52 connected to produce a binary output corresponding to the output of the respective secondary winding groups for conversion by the binary code converter circuit 59 to provide a control rod position indication on the digital indicator 60. The AC source 39, which can be implemented typically through the use of a Wein bridge oscillator, produces a one kilohertz excitation signal which is applied both to the primary windings 25 and the adjustable phase shift network 44 which consists of the resistive and capacitive components as illustrated in FIG. 14. The adjustable phase shift network 44 functions to compensate for unavoidable phase shifts introduced by the AC source 39 and the position probe assembly 10. After appropriate phase shift compensation has been provided by the positioning of adjustable resistor R1, the output signal developed at resistor R1 is supplied to the operational amplifier A of the squaring circuit 46. The operational amplifier A, in combination with the diodes D, the transistor Q, and the resistive components as indicated, functions to amplify and clip the output signal developed by the adjustable phase shift netword 44 and produce reference square wave outputs X and the complement of X, square wave X, which reference waveforms are illustrated in FIGS. 15C and 15D. Inasmuch as each of the signal processing channels 52 associated with respective groups G of secondary winding, is identical, the circuitry associated with the signal processing channel 52 connected to the first group G of secondary windings 26 is illustrated in detail. It is apparent that the circuitry and operation of the signal processing channel 52 illustrated in detail, will apply identically to the signal processing channels 52 associated with the second, third and fourth group G of secondary windings. The output signals developed by the first group G of secondary windings are amplified by the AC preamplifier circuit 53, which consists of operational amplifier A, diodes D and the resistive and capacitive components as illustrated. The amplified output of the AC preamplifier circuit 53 is supplied as an input signal to the phase splitter circuit 54. The phase splitter circuit 54, which includes transistor Q, Zener diode Z, and the resistive and capacitive components as illustrated, functions to split the input signal into the opposite polarity AC signals e.sub.S and -e.sub.S as illustrated in FIGS. 15A and 15B respectively. The AC signals e.sub.S and -e.sub.S which correspond to the output signals of the first group G of secondary windings are supplied as input signals to the phase detector circuit 55 herein illustrated as consisting of a four arm bridge arrangement including four bilateral switches S1, S2, S3, and S4. The drive signals applied to the bilateral switches correspond to the phase adjusted square wave reference signals X and X developed by the drive circuit 42. Each of the bilateral switches of phase detectors circuit 55 operates similarly to a relay contact in that when the control signals corresponding to the square wave reference signals X and X applied to the respective bilateral switches are positive, the bilateral switch exhibits a low impedance, i.e., 300 ohms, whereas when the applied drive signal is negative, the bilateral switch exhibits a high impedance between its input and output terminals. The phase detector circuit 55 can be implemented through the use of commercially available circuits such as the RCA type CD 4066A. The operation of the phase detector circuit 55 to develop the output signal e.sub.Det, which is supplied as an input to the clamped integrator circuit 58, is developed in accordance with the operation of phase detector circuit 55 as depicted in the waveforms of FIGS. 15A-15F. The e.sub.Det output signal corresponds to the phase relationship between the reference signals X and X and the signals e.sub.S and -e.sub.S. When, for the purpose of discussion, square wave reference signal X is positive and square wave reference signal X is negative, the output signal e.sub.Det of phase detector 55 corresponds to the rectified representation of signal -e.sub.S illustrated in FIG. 15E. In the situation where the square wave reference signal X is negative and the square wave reference signal X is positive, the rectified representation of signal e.sub.S as illustrated in FIG. 15F forms the output signal e.sub.Det. The clamped integrator circuit 58, which consists of operational amplifier A, Zener diode Z, DC offset adjustable resistor R2 and the remaining resistors and capacitors as shown, functions to average the output signal e.sub.Det of phase detector circuit 55 and provide a logic level "1" or "0" as determined by the polarity of the output signal e.sub.Det. The logic level output of the clamped integrator circuit 58 is supplied as the input to the binary code converter circuit 59, which responds to similar inputs from the signal processing channels 52 associated with remaining groups G of secondary windings to develop a binary coded output signal which when applied to the digital indicator circuit 60 results in the digital display of the position of control rod R of FIG. 1.
	description	This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/690,281, entitled “MOVING SOURCE AND DETECTOR COLLIMATION AND TARGETING INSPECTION SYSTEM FOR MATERIAL IDENTIFICATION BY ENERGY-DISPERSIVE COHERENT X-RAY SCATTERING OR FLUORESCENT EMMISSIONS,” filed on Jun. 14, 2005, which is herein incorporated by reference in its entirety. This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/690,440, entitled “COHERENT X-RAY SCATTERING SYSTEM WITH EXTERNAL POWER SUPPLY,” filed on Jun. 14, 2005, which is herein incorporated by reference in its entirety. 1. Field of Invention This application relates generally to material identification and more specifically to inspection systems that perform material identification. 2. Discussion of Related Art Inspection systems are widely used to obtain information on objects that cannot be readily seen in an external examination of items under inspection. Inspection systems are used as part of security systems, such as explosive detection systems, used at airports or other settings to preclude people from smuggling explosives into a secure area by concealing them in packages. Though, inspection systems may also be used during mail processing to obtain information on objects in packages, during mail processing on bones or other structures inside a human body during medical testing, on objects in food products as part of health inspections, on minerals in ore as part of a mining operation and in many other settings. Frequently, inspection systems use penetrating radiation, such as x-rays. The inspection system captures the radiation after it has interacted with an item under inspection. Analysis of the radiation reveals properties of objects inside the item under inspection. Based on this analysis, a security system can “clear” an item by determining that it contains only innocuous objects or can “alarm” an object by determining that it likely contains one or more objects that pose a threat. Other inspection systems may cause other actions based on the properties of the objects identified in the inspection. In capturing radiation, some inspection systems discriminate between radiation emanating from an object at different angles. Angular discrimination may be used in conjunction with a focusing system that passes only radiation from a specific region on which data is to be collected. In some instances, controlling the measurement angle reveals information useful for analyzing an object. For example, the angle at which radiation scatters from an object is an indication of the type of material that makes up the object. As one example, x-ray diffraction analysis may be used to analyze the spectrum of radiation scattered from a region of an item under inspection to determine whether that region contains innocuous material or a threat material. In one aspect, the invention relates to an inspection system that has a conveyor adapted to move items in a first direction. The system has a source assembly with an x-ray source adapted to irradiate an item on the conveyor and a source collimator positioned between the x-ray source and the conveyor. A first positioning mechanism is adapted and arranged to move the source assembly in a second direction, transverse to the first direction. The system also has a detector assembly with a detector and a detector collimator positioned between the detector and the conveyor. A second positioning mechanism is adapted and arranged to move the detector assembly in the second direction. The second positioning mechanism can be controlled in at least one direction independently of the first positioning mechanism. In another aspect, the invention relates to a method of operating an inspection system having a source, a detector and an inspection region adapted and arranged to position an item under inspection in a plane. According to the method, the source and the detector move parallel to the plane to create a focus region in an item under inspection. The source radiates the focus region and the detector measures radiation emanating at an angle from the focus region. The measured radiation is then analyzed. In another aspect, the invention relates to a method of operating an inspection system. The method includes moving an item through an inspection area; and gathering data on a focus region of the item using a source and a detector while moving the source and the detector synchronously with the item. The inventors have appreciated that an improved inspection system may be formed with improved material identification capabilities. The improvements may be in the size, speed, cost or accuracy of the system. In some embodiments, the improved inspection system uses an angular analysis system that selectively measures radiation at a specified angle. In one aspect, an improved angular analysis system may result from independently positionable source and detector assemblies that allow the angular analysis system to be focused on a region of an item under inspection by relative motion of the source and detector assemblies parallel to a plane holding an item under inspection. This configuration allows the angular analysis system to have a relatively small size and enables it to be practically used in environments where space is constrained. For example, such a system may be used in a baggage inspection system at an airport. It may be installed in an existing inspection bag room or as part of an in-line conveyor system without removing walls, raising ceilings or otherwise making extensive physical modifications to airport buildings. In another aspect, speed of inspection may be improved by synchronizing motion of the source and detector assembly with motion of an item under inspection while a measurement is made. Because a conveyor carrying the items does not need to stop and restart for each item to be inspected, the inspection system may have a higher throughput. Items to be inspected can be continuously inspected at a rate matching the rate at which suspicious objects are identified by a first level inspection system. In another aspect, the speed of the angular analysis system may be increased by providing a collimator configuration that increases the amount of radiation reaching the detector without unreasonably decreasing the angular resolution of the system. Such a system reduces the time required to acquire data with a signal to noise ratio adequate for an accurate determination of material properties. These aspects may also reduce system cost. For example, providing a simple mechanism to an angular analysis system on suspicious regions of an item under inspection may reduce the overall cost of the system. Costs may also be reduced in other ways. In another aspect, the angular analysis system can be simply reconfigured to selectively measure radiation emanating at different angles from a region of an item under inspection. The same detector can be used to measure radiation at multiple angles, reducing the overall cost of the system. Aspects of the angular analysis system may also increase the accuracy of the system. Facilitating measurements of radiation emanating at different angles may increase the accuracy of the system by allowing a material to be analyzed based on radiation emanated at an angle that reveals the most useful information for analysis. In addition, the small size of such a system allows it to be readily used in conjunction with systems employing other inspection technologies. Using such systems together may significantly improve the accuracy with which the overall inspection system operates. These and other aspects of an inspection system are described below using an explosive detection system as an example. Such a system, for example, may be used at an airport to inspect checked luggage, carryon baggage or other similar items. However, the invention is not limited to this example embodiment. FIG. 1 illustrates an explosive detection system 110 according to an embodiment of the invention. Explosive detection system 110 includes a mechanism to move items under inspection through the system. In this example, conveyor 112 moves item under inspection 180. Conveyor 112 runs through a tunnel 114. Tunnel 114 is formed from a housing or other suitable structure. As will be described in more detail below, explosive detection system 110 includes equipment within tunnel 114 that irradiates an item under inspection with x-rays and measures radiation that has interacted with the item under inspection. These measurements are used to aide a determination of whether the item under inspection contains an explosive. Though a single housing is shown in FIG. 1, in some embodiments, the equipment may be positioned in multiple housings. Those housings may be coupled in any suitable way, such as by a conveyor system. Moreover, the housing may be in any desired form and may be omitted in some embodiments. Explosives are one example of the types of objects that an inspection system may detect and the invention is not limited to use in conjunction with systems that detect explosives. More generally, an inspection system used as part of a security system may screen items under inspection and indicate whether each item may contain detect drugs, illicit currency, weapons or other contraband items. Though, the invention is not limited to use in conjunction with such security systems. It may be used in conjunction with any type of system that determines material properties, such as systems that detect valuable materials in mining or recycling operations. In the example of FIG. 1, item under inspection 180 is illustrated as a suitcase with an object inside of it forming a suspicious region 182. Explosive detection system 110 operates to determine, with a high degree of accuracy, whether suspicious region 182 is formed by an explosive material inside item under inspection 180. The overall output of explosive detection system 110 is an indication that item under inspection 180 either contains no explosives and is “clear” or possibly contains an explosive and requires an “alarm.” As shown, the output of explosive detection system 110 is provided at an operator review station 170. A human operator monitoring operator review station 170 may make a determination of the appropriate processing required for an item under inspection based on the output of explosive detection system 110. That output instead or additionally may be processed by one or more computers as part of making a determination of whether an item under inspection is clear or is alarmed. In the described embodiment, explosive detection system 110 includes two stages. A different inspection technology is used at each stage to make an overall determination that item under inspection 180 either is “clear” or requires an “alarm.” One stage performs a first level inspection, which, for each item under inspection, indicates that the item is clear or that it contains a suspicious region. Those items containing suspicious regions are then transferred to the second level of inspection for a more accurate determination of whether the item is clear or requires an alarm. FIG. 2 illustrates, in block diagram form, the construction of explosive detection system 110. Explosive detection system 110 includes a three-dimensional imaging system 210 and an angular analysis system 220. In this embodiment, three-dimensional imaging system 210 acts as a level 1 scanner to make an initial determination whether an item under inspection contains any suspicious regions. Angular analysis system 220 serves as a second level inspection system and determines properties of materials in each suspicious region. Information on the materials in the suspicious regions allows a more accurate indication of whether each suspicious region is either an explosive or an innocuous item. In the embodiment shown, three-dimensional imaging system 210 and angular analysis system 220 are interconnected by a conveyor system. Here the conveyor system is shown to contain conveyors 242, 244, 246, and 248. If, upon initial inspection, three-dimensional imaging system 210 detects no suspicious regions within an item under inspection, the item under inspection is diverted to conveyor 242, causing the item under inspection to be “cleared.” In the example of an explosive detection system used for an airport security system, cleared items may be loaded onto airplanes, returned to passengers for carry-on to an airplane or otherwise allowed to enter a secured area. Alternatively, if three-dimensional imaging system 210 identifies one or more suspicious regions in an item under inspection, the item under inspection is diverted to conveyor 244. Conveyor 244 carries the item under inspection to angular analysis system 220 for a level 2 inspection. As shown, three-dimensional imaging system 210 and angular analysis system 220 are both coupled to controller 230. Controller 230 provides a mechanism for information concerning an item under inspection to be passed from three-dimensional imaging system 210 to angular analysis system 220. Information passed from three-dimensional imaging system 210 to angular analysis system 220 may include the number and locations of suspicious regions identified by three-dimensional imaging system 210. Further, the information may include a preliminary indication of the type of threat object suspected or other information indicating why a region was indicated as a suspicious region by three-dimensional imaging system 210. Angular analysis system 220 uses the information generated by three-dimensional imaging system 210 to identify locations within an item under inspection at which material properties should be measured. In the pictured embodiment, angular analysis system 220 makes measurements that reveal information on the properties of materials within the suspicious regions of the item under inspection. Explosive detection system 110 may then use this information to determine whether each suspicious region contains an explosive or other threat item or whether it contains an innocuous item. Such a determination may be made by a processor or other computer hardware within angular analysis system 220 that is suitably programmed. However, such processing may be performed in any suitable processor. In the example described herein, angular analysis system 220 uses x-ray diffraction analysis to measure properties of the material in each suspicious region. Briefly, x-ray diffraction systems operate on the principal that x-rays are diffracted, or scattered, from a material at an angle that is related to the properties of that material. More specifically, x-rays are diffracted at an angle related to the energy of the x-ray and the spacing between the molecules in the material from which they are diffracted. Accordingly, the spectrum of x-rays diffracted at a particular angle from an object provides information about the type of material in that object. By matching the spectrum of scattered x-rays to a spectrum of a known explosive material or to a spectrum of a know innocuous material, angular analysis system 220 may provide information allowing a suspicious region identified by three-dimensional imaging system to be classified with higher confidence as a threat or as an innocuous item. X-ray diffraction is described in the literature, including U.S. Pat. No. 6,118,850 to Mayo et al. entitled “Analysis Methods for Energy Dispersive X-ray Diffraction Patterns,” issued Sep. 12, 2000, which is hereby incorporated by reference in its entirety. Angular analysis system 220 may perform analysis as described in that patent or in any other suitable way. However, X-ray diffraction is not the only possible type of angular analysis. Some materials fluoresce when irradiated, which generates radiation with a spectrum characteristic of the material. By capturing radiation emitted at a particular angle, it may be possible to selectively receive radiation emitted from a suspicious region of an item under inspection. Analysis of the spectrum of the captured radiation may indicate the nature of the material in that suspicious region. Regardless of the exact principle of operation of angular analysis system 220, the system includes a focusing system that allows radiation from a region of an item under inspection to be captured and analyzed. In operation, angular analysis system 220 is focused on one or more locations within each suspicious region identified by three-dimensional imaging system 210. Radiation emanating from these regions is captured and analyzed. Information obtained by this analysis is used to determine whether each suspicious region contains only innocuous material or contains material characteristic of a threat. An item under inspection for which all suspicious regions are determined to contain only innocuous material is diverted onto conveyor 246. Items diverted onto conveyor 246 are thereafter process as cleared items. Conversely, if information generated by angular analysis system 220 indicates that one or more of the suspicious regions contains an explosive or other threat item, the item under inspection is alarmed. The alarmed item may be diverted onto conveyor 248, where the item under inspection is processed in the manner appropriate for an item containing an explosive or other contraband item. For example, alarmed items may be further inspected, including by a manual search, or may be destroyed or otherwise precluded from entering a secured area. In the example of FIG. 2, three-dimensional imaging system 210 and angular analysis system 220 are shown as independent systems with controller 230 passing information between them to allow the overall system to make a determination about each item under inspection. Such an architecture is just one example of an architecture for explosive detection system 110. Acquisition of data and analysis of that data may be performed in any suitable hardware. For example, all data analysis could be performed in controller 230. In such embodiments, three-dimensional imaging system 210 may acquire data on an item under inspection and provide that data to controller 230. Controller 230 may analyze the data acquired by three-dimensional imaging system 210 to detect suspicious regions. Similarly, angular analysis system 220 may measure the spectrum of scattered radiation from an item under inspection and provide data describing the measured spectrum to controller 230. Controller 230 may thereafter analyze the measurements to determine whether an item under inspection should be processed as an alarmed item or processed as a cleared item. Though, this is only an example of one partitioning of the data analysis and processing functions and other embodiments are possible. For example, three-dimensional imaging system 210 and angular analysis system 220 may be housed within the same physical unit or may be housed in separate physical units. They may be located relatively close together or maybe located in different physical locations and interconnected through a computer network or other communication medium. In embodiments in which three-dimensional imaging system 210 and angular analysis system 220 are separate units linked by a conveyor system, it may be necessary to relate the coordinate system in which angular analysis system 220 measures properties of suspicious region to the coordinate system in which three-dimensional imaging system reports suspicious regions. In the pictured embodiment, because three-dimensional imaging system 210 and angular analysis system 220 are in separate locations, it is possible for an item under inspection to shift its position on the conveyor system as the item is moved from three-dimensional imaging system 210 to angular analysis system 220. Accordingly, angular analysis system 220 may be adapted to contain a system to register its coordinate system to that used by three-dimensional imaging system 210. An example of a suitable system is described in co-pending patent application Ser. No. 11/400,489, entitled “REGISTRATION SCHEME IN EXPLOSIVES DETECTION SYSTEM,” and filed on Apr. 7, 2006, which is hereby incorporated in its entirety. However, any suitable mechanism to relate the coordinate systems may be used. In operation, explosive detection system 110 may inspect a series of items. These items may be moved through three-dimensional imaging system 210 at a constant rate. Some portion of the items inspected at three-dimensional imaging system 210 may be cleared during first level inspection and then diverted on conveyor 242. However, the remainder of the series of items under inspection may be diverted on conveyor 244 for further analysis by angular analysis system 220. To provide high throughput for explosive detection system 110, angular analysis system 220 may process the items diverted on conveyor 244 at the same rate at which those items are processed by three-dimensional imaging system 210. Further, in some embodiments, angular analysis system 220 will perform measurements on items under inspection without stopping them as they move on conveyor 244. By avoiding the need to stop items within angular analysis system 220, the overall throughput of explosive detection system 110 may be increased. Accordingly, as described in more detail below, some embodiments of the invention provide an angular analysis system 220 that may perform measurements on items under inspection as they are moving on conveyor 244 through the angular analysis system 220. In the embodiment of FIG. 2, three-dimensional imaging system 210 acts as a level 1 scanner. Explosive detection systems with level 1 scanners are known. Any suitable level 1 scanner may be used in explosive detection system 110. However, in this example, three-dimensional imaging system 210 is a helical scan CT system. FIG. 3 illustrates a helical scan CT system that may be used as a level 1 scanner in explosive detection system 110. As shown in FIG. 3, items under inspection, such as item 382, move continuously along a conveyor 112. As item under inspection 382 passes through three-dimensional imaging system 210, an x-ray source 314 and x-ray detector array 316 rotate around conveyor 112. Though the source 314 and detector array 316 rotate in a stationary plane perpendicular to conveyor 112, because item under inspection 382 is moving along conveyor 112, the source and detector array trace out a helical path 330 relative to item under inspection 382. In the illustrated embodiment, x-ray source 314 and detector array 316 combine to measure the x-ray power passing through item under inspection 382. Such a measurement indicates the amounts various portions of the item under inspection 382 attenuated the x-rays. These attenuation measurements may be used as an indication of the density of regions of the item under inspection. In the system as shown, attenuation is determined for x-rays at a single energy level and suspicious regions are identified based on the shape and density of the region. However, materials of different atomic number attenuate x-rays of different energies differently. Some x-ray imaging systems make multi-energy x-ray measurements to obtain information about the atomic number of the materials in the item under inspection. Thus, in some embodiments, three-dimensional imaging system 210 may identify suspicious regions in part based on their atomic number. Regardless of whether single or multi-energy measurements are made, as in a conventional helical scan system, source 314 may have a beam angle α designed to intersect the entire width W of detector array 316. The speed of rotation of the source 314 and detector array 316 may be controlled relative to the speed of conveyor 112 such that the spacing D between loops of helical path 330 is sufficiently small that adequate data is collected on item under inspection 382 to allow computed tomographic reconstruction techniques to be used to form a three-dimensional image of item under inspection 382. With this configuration, an image of each item under inspection may be generated within three-dimensional imaging system 210 as items under inspection pass in a continuous stream along conveyor 112. In the embodiment of FIG. 3, an image formed by three-dimensional imaging system 210 is illustrated graphically as image 370. Image 370 appears as it may be presented on a computer screen to an operator of three-dimensional imaging system 210. In some embodiments, the image formed by three-dimensional imaging system 210 may be presented graphically to a human operator who may then select suspicious regions for further analysis. However, in other embodiments, the image may be processed by a computer system without intervention of a human operator. Data analysis techniques to automatically recognize suspicious regions from measurements made with a three-dimensional imaging system are known. Such techniques, or any other suitable technique, may be used to identify suspicious regions within item under inspection 382. Those items under inspection containing suspicious regions are diverted to angular analysis system 220 (FIG. 2). Angular analysis system may be operated to focus on the suspicious regions to better identify whether they contain threat items or innocuous items. FIG. 4 illustrates details of a focusing system of angular analysis system 220 according to an embodiment of the invention. In this embodiment, conveyor 244 moves an item under inspection 180 into an inspection region 400. Angular analysis system 220 is focused on one or more points within each suspicious region 182 identified as a result of level 1 scanning. As used herein, “focusing” means that the system is configured to receive radiation emanating from a selected region. In the configuration shown in FIG. 4, angular analysis system 220 is focused on focus region 454. To gather information on suspicious region 182, item under inspection is moved on conveyor 244 into inspection region 400. Angular analysis system 220 is then adjusted to focus on a location within suspicious region 182 and radiation emanating from that location is gathered and analyzed. If information on other locations within suspicious region 182 is desired, the system is refocused and more data is collected. In some embodiments, two measurements are taken on each suspicious region, but any number of measurements may be taken. Once data is collected for one suspicious region, the system may be refocused on other suspicious regions. In the pictured embodiment, angular analysis system 220 is an x-ray diffraction system. For an x-ray diffraction system, data is collected by radiating an item under inspection with x-rays. In the embodiment of FIG. 4, item under inspection 180 is radiated with pencil beam 450 of x-ray radiation. Pencil beam 450 is generated by an x-ray source. As can be seen in FIG. 4, pencil beam 450 passes through focus region 454. In the illustrated embodiment, angular analysis system 220 includes a source assembly 410 that generates pencil beam 450. Source assembly 410 includes an x-ray tube 412. X-ray tube 412 is powered by high voltage power supply 460. In some embodiments, high voltage power supply 460 is selected to power x-ray source 412 to emit radiation at a range of energies. The upper limit of that range is set by the voltage of high voltage power supply 460. In some embodiments, high voltage power supply 460 has an upper range of about 130 keV. In one embodiment, high voltage power supply 460 has a voltage of approximately 100 keV. A maximum supply of voltage of about 100 keV or less has been found to provide adequate energy that detector 432 may make a measurement without introducing an unreasonable amount of noise that interferes with measurements. In the illustrated embodiment, power supply 460 is not mounted to source assembly 410. It supplies power to x-ray tube 412 through flexible cable 462 that allows source assembly 410 to move relative to power supply 460. Such a configuration allows power supply to be mounted in any suitable location and may be separated from the remainder of the system by distance, shielding or in any other suitable way. Radiation leaving x-ray tube 412 is collimated into a pencil beam by collimator 414. Collimator 414 may be a material opaque to x-rays, such as titanium, having a small aperture, such as a pinhole. Collimator 414 is held by support member 418, which may be coupled to x-ray tube 412. In this embodiment, collimator 414 has a fixed position relative to x-ray tube 412 such that source assembly 410 emits pencil beam 450 perpendicular to conveyor 244. As shown, source assembly 410 may move in the directions labeled X or Z to position the source assembly 410 so that pencil beam 450 passes through any desired focus region. To position beam 450, source assembly 410 is coupled to drive mechanism 420. In operation, drive mechanism 420 is controlled, such as by commands sent from controller 230, to position pencil beam 450 such that it passes through a suspicious region 182 within item under inspection 180. Drive mechanism 420 may be any suitable drive mechanism, including an electric linear motor, an electric rotating motor or a hydraulic actuator. In this embodiment, drive mechanism 420 is shown coupled to track 422 that guides drive mechanism 420 in the Z direction. A similar track (not shown) may be included to guide drive mechanism 420 as it moves in the X direction. However, any suitable mechanical support structure may be used to movably retain source assembly 410. In the illustrated embodiment, drive mechanism 420 may position source assembly 410 at any desired position in the X-Z plane below inspection area 400. In the example of FIG. 4 in which angular analysis system 220 is an x-ray diffraction system, measurements are made by collecting radiation diffracted at a specific angle relative to pencil beam 450. In the configuration illustrated in FIG. 4, diffracted radiation 452 emanating from focus region 454 is measured and analyzed. Information is gathered on the material within focus region 454 using detector assembly 430. Detector assembly 430 includes a detector 432. In this embodiment, detector 432 may be a high performance germanium detector. Detector 432 may be chilled to increase its sensitivity. In some embodiments, a range of measurements may be made using a single detector. However, any suitable detector or detectors may be used. The output of detector 432 may be coupled to controller 230 (FIG. 2) or other suitable data processing device. This output may be processed using x-ray diffraction techniques as described above and as described in more detail below to identify the type of material within suspicious region 182. As shown in FIG. 4, detector 432 is positioned to receive radiation 452 emanating from focus region 454. Radiation 454 reaches detector 432 because it is emanating from focus region 454 at an angle that allows it to pass through both aperture plates 434 and 436. As shown, aperture plates 434 and 436 have relatively narrow apertures and are held apart by support member 438 at a sufficient distance that only radiation traveling in a relatively small range of angles can pass through aperture plates 434 and 436. Detector assembly 430 contains shielding 439 that blocks radiation from reaching detector 432 other than through aperture plates 434 and 436. The size, shape and relative position of aperture plates 434 and 436 define a field of view for detector 432. The intersection of this field of view for detector 432 with pencil beam 450 defines a focus region 454 on which a measurement is taken. By controlling the position of detector assembly 430 relative to source assembly 410, the point at which this field of view intersects pencil beam 450 can be controlled, thereby controlling the location of focus region 454. Accordingly, detector assembly 430 is coupled to a drive mechanism 440, which allows it to be positioned to achieve the desired focus. Drive mechanism 440 may be mounted on track 442 or mounted in any other suitable way that allows detector assembly 430 to be positioned so that angular analysis system 220 images the desired focus region. In the pictured embodiment, controller 230 (FIG. 2) provides commands to drive mechanism 420 and drive mechanism 440 to position source assembly 410 and detector assembly 430 such that focus region 454 coincides with a suspicious region 182. If multiple measurements are desired within one suspicious region, information may be acquired from detector 432 with the source assembly 410 and detector assembly 430 positioned to focus at the desired location within suspicious region 182. Thereafter, either or both of source assembly 410 and detector assembly 430 may be repositioned to focus angular analysis system 220 on a different location within suspicious region 182. In some embodiments, a single measurement may be made for each suspicious region 182. In other embodiments, controller 230 may control angular analysis system 220 to take a second measurement within suspicious region 182. Any number of measurements may be taken within a suspicious region. Regardless of the number of measurements taken on each suspicious region, if an item under inspection 180 contains multiple suspicious regions, controller 230 (FIG. 2) may control drive mechanisms 420 and 440 to sequentially position source assembly 410 and detector assembly 430 to focus on each suspicious region. In some embodiments, diffracted x-rays will have sufficiently low flux that data must be captured over a finite data capture period in order to capture enough x-ray photons for reliable analysis. If conveyor 244 is moving an item under inspection relative to source assembly 410 and detector assembly 430 during this data capture period, the system will be focused on different regions of the item under inspection at the start and end of the data capture period. Capturing data in this fashion may not be sufficiently accurate for some applications. Therefore, in some embodiments, controller 230 may generate commands to the conveyor system to stop conveyor 244 while data is being captured on one region of an item under inspection. Even if conveyor 244 is stopped for a measurement, it is not necessary in all embodiments that source assembly 410 and detector assembly 430 be held stationary. For example, while detector 432 is capturing data, in some embodiments source assembly 410 and detector assembly 430 may move slightly relative to item under inspection 180. Such slight motion, sometimes called “dither,” may average out measurement noise and increase the accuracy with which measurements are made. Further, whether or not dither is employed in a measurement, it is not necessary that item under inspection be held stationary while data is being acquired. In some embodiments, conveyor 244 may move item under inspection 180 through inspection region 400 while measurements are being made on item under inspection 180. Because both source assembly 410 and detector assembly 430 may move in the Z direction, source assembly 410 and detector assembly 430 may move in synchronization with item under inspection 180. In this way, the relative position of item under inspection 180 to source assembly 410 and detector assembly 430 may be maintained while a measurement is being made even though item under inspection 180 moves. If the speed of conveyor 244 is such that an item under inspection does not pass through inspection area 400 faster than the time required to take measurements on the suspicious regions in the item under inspection, conveyor 244 does not have to be stopped. By taking measurements without stopping conveyor 244, no time is lost starting and stopping conveyor 244. Furthermore, by continuously inspecting items in angular analysis system 220 at the rate at which they are processed in three-dimensional inspection system 210, items under inspection may flow continuously from the level 1 scanner, which increases the overall throughput of explosive detection system 110. With the embodiment of FIG. 4, the full range of measurements that can be made on item under inspection 180 while stopped can also be made as it moves through inspection region 400. For example, to reposition source assembly 410 and detector assembly 430 for measurements on a second suspicious region, one or both of the source assembly 410 and detector assembly 430 may be moved at a rate different than the item under inspection to focus angular analysis system 220 on the desired location within item under inspection 180. Likewise, to collect data while dithering the source and detector, the source and detector can be synchronized to, on average, move at the same speed as conveyor 244, but to have an instantaneous speed at any given time that is slightly above or slightly below the speed of conveyor 244. FIG. 5 shows in greater detail how the relative positioning of source assembly 410 and detector assembly 430 may be used to focus angular inspection system 220 on the specific focus region 454 and to selectively process radiation emanating at a defined angle. In the pictured embodiment, angular analysis system 220 may be focused in three dimensions and select an examination angle with only movement in two dimensions. Those two dimensions are parallel to conveyor 244, which allows for a compact system. FIG. 5 shows the system in cross section as seen in the Y-Z plane. As described above in connection with FIG. 4, the source and the detector can be positioned independently within the X-Z plane. Focus region 454 may be positioned at any point in the X-Z plane by positioning source 412 below the desired location. In the illustrated embodiment, detector 432 is positioned at the same X location as source 412. Then, detector 432 is positioned in the Z direction so that radiation 452, diffracted at a desired angle, Θ, from focus region 454 passes through the aperture plates 434 and 436. Once this relationship between source 412 and detector 432 is set, focus region 454 can be translated to any location in the X-Z plane by translation of source 412 and the detector 432 in unison. As the source and the detector move together, focus region 454 will move a corresponding amount. In the embodiment illustrated, the relative Y position of focus region 454 may be controlled by differential movement of source 412 and the detector 432. As shown in FIG. 5, focus region 454 is at a distance H in the Y direction below detector 432. The magnitude of H is related to the relative displacement in the Z direction of detector 432 from source 412. This relative displacement is indicated as S1. By increasing S1, the magnitude of H will increase, lowering focus region 454. Conversely, decreasing S1 will raise focus region 454. Drive mechanisms 420 and 440 can be controlled to position source 412 and detector 432 to increase or decrease S1 and position focus region 454 as desired. Furthermore, the focusing system of angular inspection system 220 also may be constructed to allow the angle E to be simply controlled. As shown in FIG. 5, the angle Θ is controlled by the distance S2 separating apertures 530 and 532. Increasing S2 causes an increase in the angle Θ. Conversely, decreasing S2 causes a decrease in the angle Θ. By coupling aperture plate 434 to a drive mechanism 520, the angle Θ may be varied automatically, such as under control of a software program on controller 230. As will be described below in conjunction with FIGS. 7A and 7B, it may be desirable to make measurements on the same region of an item under inspection at different angles or to set the angle dynamically based on information about an item under inspection. Drive mechanism 520 may be used to alter the spacing S2 in any suitable way. Aperture plate could be moved in the Z direction to directly vary the distance S2. However, in some embodiments, drive mechanism 520 may move aperture plate 434 in the X direction. In such embodiments, aperture plate 434 may contain multiple apertures, located at different Z distances from the edge of the plate. Moving aperture plate 434 in the X direction may expose a different aperture through opening 550 in support member 438, thereby changing S2. Translation in the X direction to vary the properties of the aperture in this fashion may also allow properties of the aperture other than its Z position to be easily controlled, as described below in conjunction with FIGS. 6A and 6B. In the illustrated embodiment, the source and detector have independent positioning systems, allowing both the relative X and Z position of the source and detector to be controlled. However, in some embodiments, source 412 and detector 432 are controlled so that they have the same X position. In such embodiments, it is not necessary for the source and detector to have completely independent positioning systems. Simplified operation or construction may be possible by having the X positioning systems of the source and detector electrically or mechanically coupled so that the source and detector move together in the X direction. Regardless of whether a simplified positioning system is used, angular analysis system 220 has a compact focusing system, allowing the overall system to be small and relatively low cost. The focusing system can control the coordinates of the focus region in X, Y, Z and Θ using only motion in the X-Z plane. Further, the focusing system does not require components that extend significantly further in the X-direction or Y-direction than inspection region 400 (FIG. 4). Moreover, it does not require space above or below inspection region 400. Such a focusing system compares favorably to systems using a C-arm to couple the source assembly and detector assembly. Systems with C-arms need to provide additional clearance above, below and on the side of the inspection region to accommodate the C-arm in any focus position. Turning to FIGS. 6A and 6B, additional details of aperture plate 434 may be seen. Aperture plate 434 may be constructed from a material that blocks radiation from reaching detector 432 (FIG. 4) except that radiation passing through an aperture in aperture plate 434. In the embodiment of FIGS. 6A and 6B, aperture plate 434 contains multiple apertures. Here, apertures 530 and 630 are shown for use in acquiring radiation from specified angles. As described above, motion of aperture plate 434 in the X direction positions one of the apertures in the aperture plate 434 within opening 550. The aperture on aperture plate 434 positioned within opening 550 (FIG. 5) dictates characteristics of radiation reaching the detector 432. For example, apertures 530 and 630 have different positions in the Z direction, but otherwise have similar characteristics. In this embodiment, aperture 630 is positioned in the Z direction to allow radiation at an angle of 3.2° to reach detector 432. Conversely, aperture 530 is positioned in the Z direction to allow radiation at an angle of 5° to reach detector 432. In some embodiments, apertures with different shapes or other characteristics may be included on aperture plate 434. However, in this embodiment, apertures 530 and 630 are both shown as slits elongated in the X direction. The slits are narrow in the Z direction. In an embodiment such as is shown in FIG. 5 in which the detector 432 is offset from source 412 in the Z direction, an aperture that is narrow in the Z direction provides good angular resolution. Good angular resolution, in this context, indicates that radiation diffracted at a relatively narrow range of angles is allowed to reach detector 432. Good angular resolution is desirable in some embodiments because the spectrum of diffracted radiation is dependent on the angle at which the radiation is measured. If radiation diffracted at multiple angles simultaneously reaches detector 432, multiple spectra may be superimposed in the measured radiation and it may become difficult to detect a single spectrum associated with a specific type of material within focus region 454. However, providing a narrow aperture restricts the X-ray photon flux at detector 432. For detector 432 to make an accurate measurement, it must capture a sufficient number of X-ray photons. By reducing the X-ray photon flux, the data capture time may need to be increased, which may also be undesirable in some embodiments. However, to offset a decrease in X-ray photon flux by making aperture 530 and 630 narrow in the Z direction, apertures 530 and 630 may be elongated in the X-direction. Though elongating apertures 530 and 630 in the X direction decreases the spatial resolution with which focus region 454 may be specified, the inventors have appreciated that an explosive detection system 110 is less sensitive to a decrease in spatial resolution than to a decrease in angular resolution. Accordingly, in some embodiments, a slit-shaped aperture provides a desirable compromise between resolution and data acquisition time. Nonetheless, it should be appreciated that the slit-shaped apertures as shown for apertures 530 and 630 are representative of the shapes that may be used to form apertures in plates 434. For example, apertures 530 and 630 may be shaped as ovals, circles or in any other suitable shapes. Aperture plate 434 may also include apertures with characteristics that affect operating parameters of angular analysis system 220 other than the angle of radiation allowed to reach detector 432. For example, aperture plate 434 may be constructed with an aperture to hold a calibration disk 634. Calibration disk 634 may be a printed circuit board or other substrate coated with materials that emit radiation at specific energies when radiated by X-ray energy of the type emitted by source 412. Materials having these properties are known in the art, and any suitable materials may be used to construct calibration disk 634. When calibration disk 634 is incorporated into aperture plate 434, it provides an easy mechanism for calibration of detector 432. Aperture plate 434 may be moved to position calibration disk 634 in opening 550 (FIG. 5). Calibration disk 634 may then be irradiated by beam 450. Because radiation emitted by calibration disk 634 has a known energy spectrum, the output of detector 432 in response to energy of this known spectrum may be used to calibrate detector 432. As another example of the type of aperture that may be included on aperture plate 434, pin hole 632 is shown. Aperture plate 434 may be moved to position pin hole 632 within opening 550. Pin hole 632 may have a Z position in aperture plate 434 such that when it is positioned in opening 550, it will be aligned with aperture 532 (FIG. 5). With this alignment, radiation of X-ray source 412 will reach detector 432 only if source 412 and detector 432 are aligned in the X-Z plane. Accordingly, pin hole aperture 632 may be used to align source 412 and detector 432. Alternatively, pin hole aperture 632 may be used to measure the strength of radiation passing through an item under inspection without being scattered. Being able to measure the strength of radiation passing through an item under inspection in this way may provide additional information for analyzing a suspicious region. To avoid saturating detector 432 for straight-through measurements, pin hole 632 may be laser drilled or otherwise made very small. If the material from which aperture plate 434 is constructed is to brittle to allow a sufficiently small pin hole to be formed, pin hole 632 may be provided with a small diameter by inserting a plug of a softer material, such as gold or lead, in which a small pin hole may be formed. Turning to FIGS. 7A and 7B, an example of the benefit of being able to automatically alter the properties of the aperture controlling radiation reaching detector 432 is provided. FIGS. 7A and 7B illustrate energy spectra from the same object but taken at different angles. The energy spectra of FIG. 7A was measured at an angle of 3.2° and, for example, may correspond to measurements made using aperture 630. FIG. 7B is representative of an energy spectrum taken at an angle of 5° and, for example, may represent a measurement taken with aperture 530. In FIG. 7B, four readily identifiable peaks in the spectrum are visible. The peaks are labeled A, B, C and W. In this example, the peak labeled W represents energy from X-ray source 410 that is not diffracted. Accordingly, the peak labeled W appears at approximately 60 keV in both of the spectra of FIGS. 7A and of 7B. The other peaks, labeled A, B and C appear at energies that are dependent on the measurement angle because they have been diffracted. These peaks may provide a signature characteristic of a specific material of interest. As shown in FIG. 7A, when the measurement is made at 3.2°, it is difficult to recognize the signature of that material. The peak identified as A is indistinguishable from the peak identified as W. Also, the peak identified as C is small and largely indistinguishable from noise associated with the measurement. Though the peak identified as B is readily observable, identifying a single peak in the spectrum may not provide accurate recognition of the material. In contrast, FIG. 7B shows that when X-rays scattered at an angle of 5° are measured for this material, three readily recognizable peaks identified as A, B and C appear in the spectrum. The peak A is separated in energy form the peak W in the spectrum of FIG. 7B and is therefore more readily recognizable than in FIG. 7A. Also, the peak identified as C is larger in comparison to the noise and also more readily identified. Comparison of FIGS. 7A and 7B demonstrates that in some scenarios some measurement angles will be more suited for identifying a specific material than others. Appreciation of the phenomenon that different materials will be easier to recognize for measurements taken at different angles in combination with the ease of automatically altering the measurement angles provides by the system of FIGS. 4 and 5 gives rise to a novel process for operating an explosive detection system, such as explosive detection system 110 (FIG. 1). The process is illustrated by FIG. 8. The process of FIG. 8 begins at block 810 where coordinates of suspicious regions are generated. In explosive detection system 110, coordinates of suspicious regions may be generated by three-dimensional imaging system 210. However, the suspicious regions may be identified in any suitable way. The coordinates generated at block 810 are used in sub-process 811 during which an angular analysis system is focused to measure a property of the material within a suspicious region. In the example in which the process of FIG. 8 is performed in explosive detection system 110, sub-process 811 is performed by providing coordinates of regions within the suspicious regions at which X-ray diffraction measurements are made. At block 812 an X-ray source is positioned below the specific region in which material properties are to be measured. The process continues to block 814 where a measurement angle is selected. Any suitable approach may be used to select a measurement angle. In situations where level one scanning provides information indicating the nature of the material in the suspicious region, such as for example if dual energy measurements indicate an atomic number, information may be available indicating the measurement angle most likely to produce a readily recognizable spectrum if the suspected material is present. In other embodiments, or when material information is not available, a measurement angle may initially be selected by default. In setting the measurement angle at block 814, it is not necessary that the measurement be intended to identify a threat material. For example, when level 1 scanning indicates a suspicious region because the level 1 system can not reliably determine whether the region contains an innocuous plastic case or a plastic explosive, the measurement angle may be set to capture a spectrum in which the explosive may be readily recognized or, the measurement angle may be set to capture a spectrum in which the innocuous plastic case may be readily identified. Determining that either the suspicious region contains a threat material or an innocuous material may allow a more accurate determination of whether the item under inspection should be alarmed. Once the measurement angle is selected, the process continues to block 816. At block 816, the components of the focusing system of angular analysis system 220 are positioned to provide the desired focus in height and angle. As shown in FIG. 5, drive mechanism 520 may position aperture 530 to control the measurement angle. Drive mechanism 440 may position the detector assembly to focus angular analysis system 220 on a focus region 454 at the desired height. The process then proceeds to block 818 where radiation scattered from the focus region is captured. The processing at block 818 may last until a sufficient number of scattered X-ray photons are captured to provide a reliable measurement. As described above, the processing at block 818 may be performed while conveyor 244 is stationary or may be performed while the source and detector assembly are moving with the motion synchronized to the motion of conveyor 244. Once sufficient radiation is captured, the process continues to block 820 where the spectrum of the captured radiation is analyzed. As shown in connection with FIGS. 7A and 7B, spectrum analysis performed at block 820 may involve matching peaks in the radiation spectrum to patterns of peaks associated with previously-identified material. If a sufficiently high correlation between the peaks of the captured radiation spectrum and the radiation spectrum of a known material is achieved, the material in the focus region is identified. If the material in the focus region is identified, when processing reaches decision block 822, the alarm may be resolved. The alarm may be resolved by identifying either that all suspicious regions in the item under inspection contain only innocuous materials or that at least one of the suspicious regions contains a threat material. If either of these resolutions is achieved, processing continues to block 824 where the result is reported. The processing at block 824 may include notifying a human operator that a threat has been detected, diverting the item under inspection for further processing as a cleared or alarmed item, as appropriate, or taking any other suitable action. Conversely, if processing at block 820 does not result in information that allows the alarm to be resolved, processing continues to block 826. For example, the radiation captured at block 818 may not have a spectrum with distinctive peaks that could be matched to stored spectra. At block 826, different values of S1 and S2 may be set. By setting different values of S1 and S2, radiation may be captured at a different angle, but in the pictured embodiment radiation is captured from the same focus region as at block 818. With these new settings for S1 and S2, processing proceeds to block 828. At block 282, radiation is again captured. The spectrum of this radiation is analyzed at block 830. The processing at blocks 828 and 830 may be similar to that performed at blocks 818 and 820. However, the spectra of known material compared to the radiation captured at block 830 are spectra of radiation captured at the same measurement angle that was set at block 826. Even if analysis at block 820 did not resolve the alarm, processing at block 830 may resolve the alarm if the measurement angle set at block 826 results in a radiation spectrum with a more recognizable pattern of peaks or other features. The results of the analysis performed at block 830 are reported at block 832. The processing of block 832 may be similar to the processing performed at block 824. However, if no resolution of the alarm was possible based on the analysis performed at block 830, the item under inspection may be passed on to a higher level inspection with an indication that the alarm was not resolved. The processing pictured in FIG. 8 is one example of a process that may be performed with an explosive detection system such as explosive detection system 110. Though processing is illustrated as occurring in sequential process blocks, any suitable ordering of the process blocks may be used, including concurrent execution of one or more process blocks. Also, FIG. 8 presents a greatly simplified illustration of possible processing. For example, various process steps illustrated in FIG. 8 may be repeated to take multiple measurements on each suspicious region or to take measurements on multiple suspicious regions on an item under inspection. Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. The above-described embodiments of the present invention can be implemented in any of numerous ways. For example, in the described embodiment, the detector collimator included slits elongated in the X-direction and the source and detector were controlled to maintain the same X position. The same results could be achieved by forming apertures elongated in the Y direction and controlling the source and detector to have the same Y position. Thus, specific directions of motion are not a limitation on the invention. Also, the embodiments may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers. Also, the various methods or processes outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and/or conventional programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine. In this respect, the invention may be embodied as a computer readable medium (or multiple computer readable media) (e.g., a computer memory, one or more floppy discs, compact discs, optical discs, magnetic tapes, etc.) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments of the invention discussed above. The computer readable medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present invention as discussed above. The terms “program” or “software” are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of the present invention as discussed above. Additionally, it should be appreciated that according to one aspect of this embodiment, one or more computer programs that when executed perform methods of the present invention need not reside on a single computer or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present invention. Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments. Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
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044926499	summary	FIELD OF THE INVENTION This invention relates to a method of removing carbon dioxide from a gas stream. The invention is especially applicable to the immobilization of radioactive carbon dioxide present in industrial off-gas streams, for example waste gas generated in nuclear power plants and the like. However the invention is not limited to such application but is suited to the removal of carbon dioxide from gas streams generally. BACKGROUND OF THE INVENTION The known methods of removing carbon dioxide from gases include (a) contacting the gas with a lime slurry, PA1 (b) contacting the gas with solid calcium hydroxide at elevated temperatures, typically 350.degree. C.-450.degree. C., and PA1 (c) contacting the gas with solid barium hydroxide hydrate at ambient temperatures. PA1 C is the carbon dioxide concentration upstream of the bed, PA1 T is the time required for the downstream concentration of carbon dioxide to reach 5% of the upstream concentration, and PA1 W is the weight of calcium hydroxide in the bed. The reaction product calcium carbonate, or barium carbonate, resulting from these methods is highly stable and well suited for long term storage. This offers a very attractive chemical form for the fixation and disposal of radioactive carbon isotopes. However, each of the three methods has disadvantages. The lime slurry method has a contaminated liquid effluent; the solid calcium hydroxide system requires operation at elevated temperatures; while the barium hydroxide hydrate system has the serious disadvantage that barium hydroxide is both toxic and expensive. Applicants have tested a solid calcium hydroxide system at ambient temperatures (20.degree. C.-250.degree. C.), but this was found to be quite unsatisfactory as the conversion of Ca(OH).sub.2 to CaCO.sub.3 was found to be only about 3%. However, the applicants have found, quite unexpectedly, that the solid calcium hydroxide system is most effective even at ambient temperatures if the humidity of the gas is raised to a value corresponding to a relative humidity of about 80% or higher measured at the bed temperature. Below 80% relative humidity there is absorption of the carbon dioxide, with consequent conversion of Ca(OH).sub.2 to CaCO.sub.3 as one would expect, and the conversion increases with relative humidity, but it is only when the relative humidity reaches about 80% that the conversion becomes high enough to be commercially useful. In fact, the conversion continues to increase rapidly throughout the 80%-100% relative humidity range. If the moisture content exceeds the upper limit of this range, however, the utilization of the Ca(OH).sub.2 is diminished. Further investigation showed that the bed temperature may be as low as 10.degree. C. provided that the moisture content of the gas is suitably increased. In this case the relative humidity at the bed temperature should be between about 90%-100% for there to be useful conversion, i.e. utilization, of the calcium hydroxide. On the other hand, at higher bed temperatures the relative humidity of the gas may be considerably lower, and may be as low as about 40% if the temperature of the bed is 50.degree. C. The moisture content of the gas may be further reduced for higher bed temperatures, a useful conversion of the calcium hydroxide being obtained, but at bed temperatures above about 50.degree. C. one sacrifices the main advantage of the invention, namely the effective utilization of a calcium hydroxide bed operated at a coveniently low temperature. For the benefit of the invention to be fully realized the bed should be operated in the temperature range 10.degree. C.-50.degree. C., and preferably in the temperature range 20.degree. C.-30.degree. C., the moisture content of the gas stream being controlled accordingly. U.S. Pat. No. 4,162,298 issued to David W. Holladay and Gary L. Haag, dated July 24, 1979, discloses a method for removing carbon dioxide from industrial off-gas using a particulate bed of barium hydroxide monohydrate wherein the gas is treated so that its relative humidity is in the range 10%-100%. However, no attempt was made to apply this method to a solid calcium hydroxide system, which was believed to be unsuitable. Moreover, subsequent work by Holladay and Haag, as reported in a presentation of the 16th DOE Nuclear Air Cleaning Conference, San Diego, Calif., Oct. 19-24, 1980, indicated that even the barium hydroxide system would be of little practical use if the relative humidity of the gas were too high, owing to degradation of the Ba(OH).sub.2 particles with resultant capillary condensation of water vapour and a consequent high pressure drop across the packed bed. The present applicants have discovered that the calcium hydroxide system does not have this drawback and will be most effective at very high relative humidities at which the barium hydroxide would be of little use. SUMMARY OF THE INVENTION According to the present invention, therefore, there is provided a method of removing carbon dioxide from a gas stream by passing the gas stream through a packed bed of calcium hydroxide, wherein the bed is maintained at a temperature in the range 10.degree. C.-50.degree. C., and wherein the moisture content of the gas is controlled to a value corresponding to a relative humidity in the range 40%-100% a the bed temperature. To be commercially useful the conversion of the calcium hydroxide should be at least 0.15 (i.e. 15%) calculated according to the formula ##EQU1## where R is the gas flow rate, The numbers 22.4 and 74 are respectively the molar volume of the carbon dioxide and the molecular weight of the calcium hydroxide. The calcium hydroxide should be in a form which permits a substantial flow of the gas through it without excessive pressure drop, and for this it is preferred that the calcium hydroxide be prepared by hydrating CaO, followed by drying and crushing to the required particle size, 0.25 mm-3 mm. In order to improve the gas flow it has been found advantageous to provide a plurality of packed beds in the form of relatively flat, spaced apart layers of the crushed calcium hydroxide arranged in series with respect to the gas flow.
	description	This application is the Continuation of U.S. application Ser. No. 12/485,796 filed on Jun. 11, 2009, which in turn claims priority from Japanese Patent Application No. 2008-154012 filed on Jun. 12, 2008, the contents of which are incorporated herein by reference in their entirety. 1. Field of the Invention The present invention relates to an extreme ultraviolet (EUV) light source apparatus for generating extreme ultraviolet light by applying a laser beam to a target material to turn the target material into plasma, and specifically, to an EUV light source apparatus for supplying high-quality extreme ultraviolet light with spectrum purity improved by eliminating the influence of the laser beam applied to the target material. 2. Description of a Related Art Recent years, as semiconductor processes become finer, photolithography has been making rapid progress to finer fabrication. In the next generation, microfabrication at 70 nm through 45 nm, further, microfabrication at 32 nm and beyond will be required. Accordingly, in order to fulfill the requirement for microfabrication at 32 nm and beyond, for example, exposure equipment is expected to be developed by combining an EUV light source generating EUV light having a wavelength of about 13 nm and reduced projection reflective optics. As the EUV light source, there is an LPP (laser produced plasma) light source using plasma generated by applying a laser beam to a target (hereinafter, also referred to as “LPP type EUV light source apparatus”). In the LPP type EUV light source apparatus, a target material is injected from a nozzle and a laser beam is applied toward the target material, and thereby, the target material is excited and turned into plasma. Various wavelength components including extreme ultraviolet (EUV) light are radiated from the plasma. Accordingly, a desired EUV light is selected using a collector mirror (EUV collector mirror) for selectively reflecting and collecting a desired wavelength, and the desired EUV light is output to external equipment such as an exposure unit. For example, when EUV light having a wavelength near 13.5 nm is collected, an EUV collector mirror having a reflecting surface is used on which a multilayer film with alternately stacked molybdenum and silicon (Mo/Si multilayer film) is formed. However, also the light directly radiated from the target plasma and excitation laser beam reflected from the target and so on are mixed in the desired EUV light. A resist for exposure to be used in the EUV exposure unit is exposed to light having a wavelength from 130 nm to 400 nm in the spectrum of light generated from the target plasma, and it may reduce the exposure contrast. Further, infrared light contained in the excitation laser beam may be absorbed by optical parts, masks, wafers, and so on, to cause thermal expansion, and it may reduce the accuracy of patterning. Therefore, it is necessary to suppress those light components. Conventionally, in the LPP type EUV light source apparatus, a spectrum purity filter (SPF) has been used for removing components unnecessary for EUV exposure from the spectrum of light radiated from plasma. In a technology disclosed in U.S. Pat. No. 6,809,327 B2, as shown in FIG. 17, a laser beam emitted from a carbon dioxide (CO2) laser is introduced into a vacuum chamber and focused, the laser beam is applied to a target of tin (Sn) droplets or the like supplied by a target supply unit to turn the target into plasma, light radiated from the plasma is collected by an EUV collector mirror, and the collected light is spectrum-separated by a grating type SPF, and thereby, only the EUV light having a wavelength around 13.5 nm (negative first-order light in the drawing) is guided to an exposure unit. Further, by providing a thin film filter between the exposure unit and the vacuum chamber, Sn debris flying from the target material (Sn) introduced into the vacuum chamber and the target plasma is prevented from flowing to the exposure unit side and contaminating optical parts within the exposure unit. When a material such as zirconium (Zr) or silicon (Si) with higher transmittance for EUV light having a wavelength around 13.5 nm than for other wavelengths is selected, the thin film filter also serves as a thin film filter type SPF. In the conventional LPP type EUV light source apparatus as shown in FIG. 17, the light spectrum-separated and eliminated by the grating type SPF is absorbed by a dumper and turns into thermal energy. Further, Japanese Patent Application Publication JP-P2006-191090A discloses another SPF using apertures or an aperture array for reflecting light having a longer wavelength than twice the width of the aperture to suppress transmission of the light. Furthermore, Japanese Patent Application Publication JP-P2007-129209A discloses using, as an SPF, a gas curtain formed by combining necessary kinds of gases that do not have absorption capability for EUV light but have absorption capability for wavelengths to be eliminated. Especially, in the LPP type EUV light source apparatus using a CO2 laser beam (infrared light having a wavelength of 10.6 μm) for excitation of the Sn target, the CO2 laser beam having high-power is also reflected or scattered by the target or the like, and it is necessary to remove the CO2 laser beam by the SPF. For example, assuming that the intensity of the EUV light with the center wavelength of 13.5 nm is “1”, the intensity of the CO2 laser beam is required to be suppressed to about “0.1” or less. Accordingly, in view of removal of the CO2 laser beam, there have been the following problems in the above-mentioned conventional technologies. (1) Since the transmittance of the thin film filter type SPF that isolates the exposure unit from the EUV light source apparatus is as low as about 40%, the output efficiency of EUV light is very poor. Further, the thin film is easily broken by the incidence of debris. Furthermore, when debris adheres to the thin film, the debris absorbs EUV light and the temperature rises, and the filter itself may be melted, and therefore, it is difficult to maintain the function as the SPF.(2) In the SPF using an aperture array, there are issues of improving the efficiency of EUV light to be outputted to the exposure unit by improving the aperture ratio while maintaining the structural strength of the SPF, improving the reflectance of the CO2 laser beam to be blocked, and reducing the risk of deformation and breakage due to temperature rise caused by light absorption. Further, the fine intensity distribution of EUV light generated in the aperture array may disturb the exposure uniformity of the semiconductor and cause exposure variations.(3) In the SPF utilizing the selective absorption of gases, no kinds of gases suitable for absorption of CO2 laser beam is disclosed. The present invention has been achieved in view of the above-mentioned problems. The purpose of the present invention is to provide an EUV light source apparatus using a spectrum purity filter (SPF) capable of obtaining EUV light with high spectrum purity. In order to accomplish the above-mentioned purpose, an extreme ultraviolet light source apparatus according to one aspect of the present invention is a laser produced plasma type extreme ultraviolet light source apparatus for generating extreme ultraviolet light by applying a laser beam to a target material, and the apparatus includes: a chamber in which extreme ultraviolet light is generated; target supply means for supplying a target material to a predetermined position within the chamber; a driver laser using a laser gas containing a carbon dioxide gas as a laser medium, for applying a laser beam to the target material supplied by the target supply means to generate plasma; a collector mirror for collecting the extreme ultraviolet light radiated from the plasma to output the extreme ultraviolet light; and a spectrum purity filter provided in an optical path of the extreme ultraviolet light outputted from the collector mirror, for transmitting the extreme ultraviolet light and reflecting the laser beam, the spectrum purity filter including a mesh having electrical conductivity and formed with an arrangement of apertures having a pitch not larger than a half of a shortest wavelength of the laser beam applied by the driver laser. The mesh may be formed of a material having electrical conductivity, or may be formed by coating a material having electrical conductivity on at least a light incident surface or a back or a sidewall thereof. According to the one aspect of the present invention, by using the spectrum purity filter (SPF) including the mesh formed with an arrangement of apertures having a pitch not larger than a half of a shortest wavelength of the laser beam applied by the driver laser, the EUV light having a short wavelength is transmitted and the CO2 laser beam having a long wavelength is reflected, and thereby, EUV light having high spectrum purity can be obtained. Further, in the case of providing a metal coating of gold, molybdenum, or the like to the light incident surface of the mesh, the CO2 laser beam becomes hard to be absorbed by the light incident surface of the mesh of the SPF, and the risk of deformation and breakage caused by temperature rise of the SPF is reduced. Since an oscillation wavelength of a general CO2 gas laser is 10.6 μm, an SPF formed with an arrangement of apertures having a pitch not larger than a half of a wavelength of the laser beam, that is, a pitch not larger than 5.3 μm may be used. Further, in the case where a CO2 gas laser oscillates in a band of transition 00° 1-02° 0, an oscillation wavelength of the CO2 gas laser becomes nearly 9.56 μm. In this case, an SPF formed with an arrangement of apertures having a pitch not larger than a half of a wavelength of the laser beam, that is, a pitch not larger than 4.78 μm may be used. As mentioned above, in order to reflect the CO2 laser beam, an SPF formed with an arrangement of apertures having a pitch not larger than a half of a shortest wavelength of the laser beam applied by the driver laser is necessary. Hereinafter, preferred embodiments of the present invention will be explained in detail by referring to the drawings. The same reference numerals are assigned to the same component elements and the description thereof will be omitted. FIG. 1 shows a configuration of an extreme ultraviolet (EUV) light source apparatus according to the first embodiment of the present invention. The EUV light source apparatus employs a laser produced plasma (LPP) type of generating EUV light by applying a laser beam to a target material for excitation. As shown in FIG. 1, the EUV light source apparatus according to the embodiment includes a first vacuum chamber 1 in which EUV light is generated and a second vacuum chamber 2 for guiding the generated EUV light to an external exposure unit, and improves the quality of the generated EUV light 10 with a mesh-type spectrum purity filter (SPF) 22. Further, the EUV light source apparatus includes a target supply unit 5 for supplying a target 4 to a predetermined position (beam focusing point 9) within the first vacuum chamber 1, a driver laser 6 provided outside of the first vacuum chamber 1, a laser beam focusing optics 8 including at least one lens and/or at least one mirror arranged outside and/or inside of the first vacuum chamber 1, for guiding and focusing an excitation laser beam 7 applied by the driver laser 6, an incident window 34 for introducing the excitation laser beam 7 into the first vacuum chamber 1, an EUV collector mirror 11 for reflecting and collecting the EUV light 10 radiated from plasma generated when the excitation laser beam 7 is applied to the target 4 at the beam focusing point 9, a first vacuum pump 12 for evacuating the first vacuum chamber 1, and a second vacuum pump 25 for evacuating the second vacuum chamber 2. Furthermore, the EUV light source apparatus includes a first pinhole aperture (aperture part) 14 provided on a partition wall between the first vacuum chamber 1 and the second vacuum chamber 2, for connecting the first vacuum chamber 1 to the second vacuum chamber 2, and a second pinhole aperture (aperture part) 23 for guiding EUV light entering from the first pinhole aperture 14 to an exposure unit. Furthermore, the EUV light source apparatus may include a mitigation unit 16 for protecting the EUV collector mirror 11 and so on from debris. The mitigation unit 16 may include a superconducting coil electromagnet 19 for generating lines of magnetic force 20 surrounding the plasma, for example. Moreover, the EUV light source apparatus may include a valve for introducing an etchant gas for cleaning, and a gate valve 28 provided at the downstream of the second pinhole aperture 23, for preventing the etchant gas from flowing out into the exposure unit at cleaning. The target supply unit 5 heats and dissolves solid tin (Sn) and supplies it in a solid state or liquid droplets as the target 4 into the first vacuum chamber 1. The target 4 passes through the beam focusing point 9 at which it intersects with the excitation laser beam 7. The driver laser 6 is a high-power CO2 pulse laser using a laser gas containing a carbon dioxide gas (CO2) as a laser medium (e.g., the output: 20 kW, the pulse repetition frequency: 100 kHz, the pulse width: 20 ns). The excitation laser beam (CO2 laser beam) 7 applied by the driver laser 6 is focused on the target 4 via the laser beam focusing optics 8 and the incident window 34 of the first vacuum chamber 1, excites the target 4 to turn it into plasma, and generates EUV light 10 (the center wavelength: 13.5 nm). The generated EUV light 10 is collected and outputted to an intermediate focus (IF) by the EUV collector mirror 11 having an ellipsoidal reflecting surface, and guided to the exposure unit. When the target 4 is excited, the CO2 laser beam 7 applied by the driver laser 6 is reflected by the target 4 and scattered or reflected by the plasma generated at the beam focusing point 9, and reflected and collected by the EUV collector mirror 11 toward the IF. The SPF 22 for blocking the CO2 laser beam 7 is arranged between the IF and the EUV collector mirror 11, and transmits the EUV Light 10 having the center wavelength of 13.5 nm necessary for EUV exposure from among the light reflected by the EUV collector mirror 11. On the other hand, the SPF 22 reflects the CO2 laser beam 7 and the reflected CO2 laser beam 7 enters a water-cooling dumper 24 arranged on a reflection optical axis of the EUV collector mirror 11, and is absorbed and converted into heat. Alternatively, the SPF 22 may be slightly tilted such that light having a long wavelength such as a CO2 laser beam is reflected in a direction at an angle relative to the reflection optical axis of the EUV collector mirror 11, and the water-cooling dumper 24 may be arranged in a position not to block the EUV light 10 reflected by the EUV collector mirror 11. The two pinhole apertures 14 and 23 are arranged at the upstream and downstream of the IF, and the degree of vacuum is made higher in the second vacuum chamber 2 between the two pinhole apertures 14 and 23 by the vacuum pump than that in the first vacuum chamber and in the space connecting to the exposure unit. The diameters of the apertures 14 and 23 are about several millimeters. The IF is provided in the second vacuum chamber 2 other than the first vacuum chamber 1. By this configuration, the target and debris within the first vacuum chamber 1 are prevented from flowing into the exposure unit according to the principle of differential evacuation. In the embodiment, the superconducting coil electromagnet 19 for generating a magnetic field is used as the mitigation unit 16 for protecting the optical elements (the SPF 22, the EUV collector mirror 11, the laser beam focusing optics 8, the incident window 34, incident windows of an EUV light sensor and other optical sensors, and so on) within the first vacuum chamber 1 from the debris flying from the plasma at the beam focusing point 9. Since Sn ions generated from the target plasma have charge, the ions are subjected to Lorentz force in the magnetic field, restrained by the lines of magnetic force, and ejected to the outside of the first vacuum chamber 1 by the vacuum pump 12. On the other hand, neutral Sn particles other than the ions generated from the target plasma are not restrained by the magnetic field, and fly to the outside of the lines of magnetic force as Sn debris and gradually contaminate the optical elements. In the embodiment, the probability that the debris passes through the pinhole aperture 14 is lowered by imposing a spatial restriction by the pinhole aperture 14, and the debris that has passed the pinhole aperture 14 is collected by a vacuum pump 25. Thus, the debris hardly flows into the exposure unit through the other pinhole aperture 23. However, due to diffusion of neutral debris within the first vacuum chamber 1, the surface of the SPF 22 may be gradually contaminated by the debris and overheated. In this case, the SPF 22 may be cleaned by using the etchant gas under the condition that the operation of the EUV light source apparatus is temporarily stopped and the exposure unit is completely isolated from the first vacuum chamber 1 and the second vacuum chamber 2 by closing a gate valve 28 provided near the IF. As the etchant gas, a hydrogen gas, halogen gas, hydrogen halide, argon gas, or mixed gas of them is used, and the cleaning may be promoted by heating the SPF 22 with a heating unit (not shown). Further, the cleaning may be promoted by exciting the etchant gas with RF (radio frequency) waves or microwaves. When the cleaning is finished, the supply of the etchant gas is stopped. After confirming that the degree of vacuum in the second vacuum chamber 2 is made lower enough by the vacuum pump 25, the gate valve 28 is opened and the operation of the EUV light source apparatus is restarted. By the above-mentioned mitigation unit 16 using the magnetic field, the surface of the SPF 22 can be effectively prevented from being sputtered by the Sn ions. However, the neutral Sn debris is deposited on the SPF 22, and thereby, the reflectance of the CO2 laser beam in the SPF 22 is gradually reduced with the operation, and the SPF 22 absorbs light and the temperature rises. In the embodiment, by observation of the temperature distribution of the SPF 22 with a thermoviewer, and when sensing that the temperature rise is greater than a threshold level due to adherence of the neutral Sn debris, the apparatus may be stopped for replacement or the above-mentioned cleaning of the SPF 22. FIG. 2 is a perspective view showing a first example of the SPF used in the extreme ultraviolet light source apparatus according to the first embodiment. The SPF includes a mesh 22a in which an arrangement of apertures having a predetermined pitch is formed. In the first example, the mesh 22a has a square-lattice form. The mesh 22a may be manufactured by arranging plural wires laterally and longitudinally, or manufactured by forming plural apertures on a substrate to remain frames, for example. Here, assuming that each wire or frame has a diameter D and each aperture has a lateral width Wx and a vertical width Wy, each of the lateral pitch (Wx+D) and the vertical pitch (Wy+D) is made equal to or less than a half of a wavelength of an incident electromagnetic wave, that is, a CO2 laser beam in the embodiment. For example, by making each of the lateral pitch and the vertical pitch equal to or less than 5 μm, the CO2 laser beam having a wavelength of 10.6 μm is blocked, and transmittance becomes about 1/1000, and thus, the CO2 laser beam is prevented from passing therethough. On the other hand, the EUV light having a center wavelength of 13.5 nm is transmitted through the SPE 22 according to the aperture ratio of the mesh. The aperture ratio E (%) is calculated by the following equation.E=100×(Wx×Wy)/((Wx+D)×(Wy+D)) For example, given that each of the lateral width Wx and the vertical width Wy of the aperture is 4.5 μm and the diameter D of the wire or frame is 0.5 μm, the aperture ratio E is 81%. In practice, the mesh acts on the EUV light as a diffraction grating, and the transmittance is further reduced in consideration of diffraction loss. FIGS. 3 and 4 are diagrams for explanation of relationships between the aperture of the mesh shown in FIG. 2 and the transmittance of the EUV light. FIG. 3 shows changes of diffraction loss and transmittance relative to the aperture ratio of the mesh, and FIG. 4 is a diagram for explanation of the diffracted light generated on the surface of the SPF. When the first or higher order of diffracted light as shown in FIG. 4 is calculated as loss, there is a relationship between the aperture ratio and the transmittance as shown in FIG. 3. FIG. 3 also shows the transmittance without diffraction loss. In consideration of diffraction loss in the mesh having an aperture ratio of 81%, the transmittance is about 66%. Further, from FIG. 3, it is known that the mesh having a high aperture ratio, for example, equal to or larger than 80% is desirable for reducing the diffraction loss. Referring to FIG. 1 again, in order to minimize the loss of the EUV light toward the exposure unit, it is required that the position of the SPF 22 is made closer to the position of the IF such that the diffracted light is also used in the exposure unit. When the position of the SPF 22 is made closer to the IF, energy density of the EUV light entering the SPF 22 becomes greater, and it is required that no structural deformation or breakage occurs even when the SPF 22 absorbs light having great energy density and its temperature rises. FIG. 5 is a plan view showing a second example of the SPF used in the extreme ultraviolet light source apparatus according to the first embodiment. Further, FIG. 6 is a sectional view along A-A in FIG. 5. The SPF includes a mesh 22b in which an arrangement of apertures having a predetermined pitch is formed. In the second example, the mesh 22b has a honeycomb form. The mesh 22b may be manufactured by consecutively arranging plural frames each having a regular hexagon shape, or forming plural apertures on a substrate, for example. In the second example, an arrangement of apertures has a pitch (W+D) at maximum, and the pitch is made equal to or less than 5 μm. The SPF shown in FIG. 5 includes the honeycomb mesh 22b more adapted to the above-mentioned requirements, and realizes a high aperture ratio and high EUV light transmittance while maintaining the mechanical strength of the mesh. There are advantages that the honeycomb structure is a strong and hardly deformed structure obtained by arranging regular hexagons without gaps, an amount of a material necessary for manufacture can be made small, the diameter D of the frames forming the hexagons can be made small, and the aperture ration can be taken larger, and so on. In the embodiment, the material of the mesh is a material having a high coefficient of thermal conductivity and high rigidity such as silicon (Si), silicon carbide (SiC), diamond-like carbon (DLC), diamond, or the like, andmaintains the mechanical strength of the SPF. A metal coating of gold (Au), molybdenum (Mo), or the like is provided to at least the light incident surface of the mesh, improves the reflectance of the CO2 laser beam, reduces the absorption of the CO2 laser beam in the SPF, and reduces the thermal deformation and breakage of the SPF. Further, since the mesh is manufactured by using a material having a high coefficient of thermal conductivity, the heat can be efficiently removed via a holder for holding the periphery of the mesh, and the thermal deformation and breakage of the SPF can be further reduced. FIG. 7 is a sectional view showing a third example of the SPF used in the extreme ultraviolet light source apparatus according to the first embodiment. In the SPF, a substrate made of the same material as that of the mesh is arranged on a light exit surface of the mesh. In order to fabricate such a structure, for example, a silicon (Si) substrate is etched by using an etching device to be used in the semiconductor manufacturing process, and thereby, the substrate and the mesh are integrally fabricated. A metal coating of gold (Au), molybdenum (Mo), or the like is applied on at least the light incident surface of the mesh, and thereby, improves the reflectance of the CO2 laser beam, reduces the absorption of the CO2 laser beam in the SPF, and reduces the thermal deformation and breakage of the SPF. Although examples are shown in FIGS. 6 and 7, in which a metal coating of gold (Au), molybdenum (Mo), or the like is provided on the light incident surface of the mesh so as to efficiently reflect the CO2 laser beam, the present invention is not limited to these examples. As far as the mesh has electrical conductivity, it is possible to reflect an electromagnetic wave or light having a wavelength equal to or larger than twice a pitch of the mesh. Specifically, the mesh itself may be formed of a material having electrical conductivity, or a material having electrical conductivity may be coated on the light incident surface, a back, or a sidewall of the mesh. Further, the thickness of the silicon substrate is made as thin as about 150 nm and the rear surface of the silicon substrate is coated with zirconium (Zr), and thereby, the substrate part also has the optical characteristic of the conventional thin film filter type SPF and can suppress transmission of not only the CO2 laser beam but also other unwanted spectra. Furthermore, the mesh reinforces the substrate in strength, and has greater mechanical strength than the conventional thin film filter type SPF, and hard to be broken. As the material of the substrate and the mesh, a material having high transmittance for EUV light and great mechanical strength such as silicon carbide (SiC), diamond-like carbon (DLC), diamond, or the like may be employed as well as silicon. When the material of the substrate and the mesh has high hardness and a high coefficient of thermal conductivity like diamond or the like, the substrate and mesh can be made thinner while the mechanical strength is held, and thereby, the aperture ratio is greater and the transmittance for EUV light is higher, and the efficiency of the light source can be improved. Furthermore, since the coefficient of thermal conductivity is great, the light energy absorbed by the substrate and the mesh can be efficiently removed and the risk of the deformation and breakage can be reduced. FIG. 8 is a perspective view showing an SPF including a holder. In FIG. 8, the case of using the mesh 22a is shown, however, the mesh 22b may be also used. The mesh 22a of the SPF 22 is thin and flexible, and therefore, unable to autonomously hold its position. Accordingly, by holding the periphery of the mesh 22a with the holder 31 such that the surface of the mesh 22a is flat, adequate surface tension is obtained, and the mesh 22a is provided within the first vacuum chamber 1 as a film-like element under tension. The holder 31 of the SPF 22 is made of a metal having a high coefficient of thermal conductivity such as copper, and has a structure in which a channel for passing a medium (water or the like) for cooling or heating the mesh is formed. FIG. 8 shows an inlet 31a and an outlet 31c of the channel. Since the mesh 22a of the SPF 22 is formed of a material having a high coefficient of thermal conductivity, the heat generated in the mesh 22a can be efficiently removed via the holder 31 for holding the periphery of the mesh 22a. Therefore, by using the holder 31, the thermal deformation and breakage of the SPF 22 can be prevented. Further, when the SPF 22 is cleaned with an etchant gas or the like, the mesh 22a may be heated via the holder 31 for promotion of chemical reaction for cleaning. FIGS. 9 and 10 are conceptual diagrams for explanation of a mechanism of rotating or vibrating the holder of the SPF. FIG. 9 shows a mechanism for rotating the holder 31 with a motor or the like. By rotating the SPF 22, the variations in the part of the SPF 22, to which EUV light is applied, are averaged, and the fine intensity distribution of transmitted EUV light caused by transmittance variations of the SPF 22 is solved by time integration, and thereby, exposure variations can be improved. The holder 31 may be rotated by an ultrasonic motor as disclosed in Japanese Patent Application Publication JP-A-7-184382, which is incorporated herein by reference. According to the technique of rotating the SPF, the location, where the CO2 laser beam reflected or diffused by the target is applied, changes with the rotation, and thereby, the heat generated in the SPF 22 can be efficiently diffused and the life of the SPF 22 can be extended. Further, FIG. 10 shows a direct-driving actuator including a piezoelectric element or the like. By providing vibration to the SPF 22, the fine intensity distribution of transmitted EUV light generated by the SPF 22 is solved by time integration, and thereby, exposure variations can be improved. FIG. 11 shows a configuration of an extreme ultraviolet light source apparatus according to the second embodiment of the present invention. In the second embodiment, a driver laser 32 uses a laser gas containing a carbon dioxide (CO2) gas as a laser medium and radiates an excitation laser beam (CO2 laser beam) having linear polarization, and a wire grid polarizer is used in place of the mesh in a spectrum purity filter (SPF) 33. The rest of the configuration is the same as that in the first embodiment. FIG. 12 is a principle diagram for explanation of the polarization direction of the CO2 laser beam and the wire grid polarizer. The wire grid polarizer 41 has periodically arranged wires of a metal or the like, and the wire spacing is made equal to or less than a half of a wavelength of an incident electromagnetic waves, that is, the CO2 laser beam in the embodiment. As shown in FIG. 12, the wire grid polarizer 41 has transmittance that changes according to the polarization direction of the incident electromagnetic waves. In the case where the pitch of the wires is equal to or less than 5 μm, the wire grid polarizer 41 reflects and blocks the CO2 laser beam at high reflectance when the electric field vibration direction in the CO2 laser beam having the linear polarization and the extending direction of the wires are substantially the same. Accordingly, in FIG. 11, by determining the polarization direction of the excitation laser beam 7 applied by the driver laser 32 and the direction of the wire grid in the SPF 33 as described above, the SPF 33 can reflect the CO2 laser beam reflected by the target and suppress the CO2 laser beam from entering the exposure unit. On the other hand, the EUV light has transmittance and diffraction loss according to the aperture ratio similarly to the mesh in the first embodiment. The difference from the mesh is that the wires are only in one direction in the wire grid polarizer. The substantial aperture ratio E (%) is expressed by the following equation.E=100×W/(W+D)Therefore, when the diameter D and the aperture width W of the wires are made the same as those in the mesh type, the higher aperture ratio, i.e., the higher EUV transmittance than that of the mesh type can be expected. The light component of the reflected CO2 laser beam and so on enters the dumper 24 and is absorbed. In FIG. 11, the dumper 24 is arranged off the optical axis, however, it may be arranged on the optical axis as shown in FIG. 1. When it is difficult to obtain the linear polarized CO2 laser beam, by arranging two wire grid polarizers overlapping such that the extending directions of the respective wires are orthogonal to each other, the CO2 laser beam can be blocked as is the case of the mesh. The CO2 laser beam becomes linear polarized light having a polarization plane in a direction orthogonal to the direction of the extending direction of the wires after transmitted through the first wire grid polarizer, and thus, the CO2 laser beam is unable to pass through the second wire grid polarizer provided orthogonally to the first wire grid polarizer. In this way, the CO2 laser beam applied by the driver laser 6 can be efficiently blocked regardless of its polarization state. In this case, the difference from the case of one wire grid polarizer is that the heat load per one polarizer due to light absorption is reduced to half and thermal deformation and breakage becomes less because the light is reflected and absorbed by the two wire grid polarizers. These wire grid polarizers are fabricated of a material having a high coefficient of thermal conductivity and high rigidity such as silicon (Si), silicon carbide (SiC), diamond-like carbon (DLC), diamond, or the like similarly to the mesh in the first embodiment such that the mechanical strength of the SPF 33 is maintained. Further, a metal coating of gold (Au), molybdenum (Mo), or the like is provided to at least the light incident surface of the wire grid polarizer such that the reflectance of the CO2 laser beam is improved, the absorption of the CO2 laser beam by the SPF 33 is reduced, and the thermal deformation and breakage of the SPF 33 are reduced. Further, since the wires of the wire grid polarizer are made of a material having a high coefficient of thermal conductivity, as is the case of the SPF 22 in the first embodiment as shown in FIG. 8, by providing the holder 31 (FIG. 8) for holding the periphery of the wire grid polarizer such that the surface of the wire grid polarizer is flat, the heat can be efficiently removed via the holder, and the thermal deformation and breakage of the SPE 33 can be further reduced. In the first and second embodiments, the SPF 22 or SPF 33 is provided between the EUV collector mirror 11 and the IF, however, the same effect can be obtained even when the SPF is provided in an arbitrary location in an optical path of the EUV light 10 such as a space of the exposure unit side at the downstream of the IF in the passage of the EUV light 10. FIG. 13 shows a configuration of an extreme ultraviolet light source apparatus according to the third embodiment of the present invention. In the embodiment, an SPF of gas absorption type specialized for blocking the CO2 laser beam is used and sulfur hexafluoride (SF6) gas is used as a gas for absorption. The rest of the configuration is the same as that in the first embodiment. In the embodiment, a gas introducing nozzle 43 and a gas discharging nozzle 47 are provided to face each other near the IF within the first vacuum chamber 1. The SF6 gas is introduced near the IF within the first vacuum chamber 1 via the gas introducing nozzle 43 and the SF6 gas is collected into the gas discharging nozzle 47 by using a vacuum evacuation pump, and thereby, a gas curtain 45 of SF6 is generated. The sulfur hexafluoride (SF6) gas has a property of specifically absorbing the CO2 laser beam having a wavelength of 10.6 μm, and absorbs and blocks the CO2 laser beam of the light focused toward the IF. The technology of the gas curtain is disclosed in JP-P2007-129209A. However, nothing about the use of SF6 gas in the apparatus using the CO2 laser beam is described. The SF6 gas has nonlinear absorption rate for the CO2 laser beam, and the absorption rate is high when the light energy density intensity is low and the absorption rate becomes lower as the light energy density intensity becomes higher. When the SF6 gas is used as the SPF of gas absorption type, absorption is less in the focused part of the CO2 laser beam in which the energy density intensity is very high for excitation of the plasma for generating the EUV light, however, it is possible to effectively absorb the CO2 laser beam reflected or scattered by the target or the like and having low energy density intensity. Therefore, the CO2 laser beam reflected or scattered by the target or the like can be efficiently absorbed and blocked while the energy for excitation of the plasma for generating the EUV light is maintained. Further, the region, where the CO2 laser beam for excitation of the plasma for generating the EUV light is focused, is partially covered by a hood 49 and the space within the hood is purged with argon (Ar) gas introduced from a purge nozzle 51, and thereby, the concentration of the SF6 gas in the region, where the CO2 laser beam is focused, is reduced, and the absorption of the CO2 laser beam can be further reduced. Although argon (Ar) gas is used as a purge gas in this example, the present invention is not limited to this example, and a buffer gas such as hydrogen (H2) gas or helium (He) gas can be used as the purge gas. The above-mentioned SF6 gas and Ar gas are ejected by three vacuum evacuation pumps. Here, it is necessary to maintain the concentration of the gas within the first vacuum chamber 1 equal to or less than 1 Torr, for example, such that the gas within the first vacuum chamber 1 can sufficiently transmit the EUV light. In the third embodiment, as is the cases of the first and second embodiments, the two pinhole apertures 14 and 23 are arranged at the upstream and downstream of the IF and the space between the apertures is used as the second vacuum chamber 2, and the respective parts are formed such that the IF is located within the second vacuum chamber 2. The degree of vacuum is made higher in the second vacuum chamber 2 by the vacuum pump 25, and thereby, the debris generated in the first vacuum chamber 1 and the SF6 gas can be ejected from the second vacuum chamber 2 and prevented from entering the exposure unit. In the fourth embodiment, a CO2 laser system for performing multiline amplification is used as the driver laser of the EUV light source apparatus. Other configuration is the same as that in the first to third embodiments. FIGS. 14A and 14B show amplitude lines of a CO2 laser. In each of a band of transition 00° 1-10° 0 as shown in FIG. 14A and a band of transition 00° 1-02° 0 as shown in FIG. 14B, there exist plural amplification lines (see C. K. N. Patel, “Continuous-Wave Laser Action on Vibrational Transition of CO2”, American Physical Society, Vol. 135 (5A), A1187-A1193, November 1964). A general CO2 gas laser performs laser oscillation at only an amplification line P(20) with a wavelength of 10.6 μm. The reason is that a gain at the amplification line P(20) in the band of transition 00° 1-10° 0 is the most significant even when compared with those at other amplification lines, and energy is concentrated to the amplification line P(20). However, in order to generate plasma for radiating ELM light, a laser beam having a short pulse width of about 20 ns to 50 ns is necessary. In order to efficiently amplitude the laser beam having such a short pulse width, it is known that the multiline amplification type of amplifying the laser beam at plural amplification lines is suitable. In the case of performing the multiline amplification, seed light having wavelengths at amplification lines P(20), P(18), P(16) in the band of transition 00° 1-10° 0 and an amplification line P(22) in the band of transition 00° 1-02° 0 can be amplified by being passed through a CO2 laser gas as a laser medium. Here, a wavelength at the amplification line P(22) in the band of transition 00° 1-02° 0 is about 9.56 μm. Therefore, in the case of using the amplification line in the band of transition 00° 1-02° 0, even if an arrangement of apertures having a pitch of, for example, 5.3 μm, which is equal to or less than a half of a wavelength of the general CO2 laser beam (10.6 μm), is formed in the SPF, a CO2 laser beam having a wavelength of 9.56 μm is transmitted without being reflected. In order to reflect the CO2 laser beam having a wavelength of 9.56 μm, the SPF formed with an arrangement of apertures having a pitch equal to or less than a half of the shortest wavelength among wavelengths of a laser beam applied by the driver laser is necessary. FIG. 15 shows a configuration of a CO2 laser system for performing multiline amplification at desired amplification lines. Plural semiconductor lasers for performing pulse oscillation in a single longitudinal mode in correspondence with wavelengths at plural amplification lines in a CO2 gas laser are used as master oscillators, and thereby, the multiline amplification can be realized. The CO2 laser system 60 includes plural semiconductor lasers 61, an optical multiplexer 62 for combining seed pulse light outputted from the plural semiconductor lasers 61, a preamplifier 63 for pre-amplifying the combined seed pulse light, and a main amplifier 64 for further amplifying the laser light pre-amplified by the preamplifier 63. Here, the preamplifier 63 and the main amplifier 64 use a laser gas containing a carbon dioxide gas (CO2) as a laser medium. By passing the seed pulse light at multi-lines through the laser medium, pulse amplification at multi-lines can be realized. The concrete example will be explained as follows. FIGS. 16A and 16B show intensity distribution in the case where intensity of wavelength components included in a laser beam outputted from a main amplifier is made uniform by adjusting light intensity in a longitudinal mode in oscillation of plural semiconductor lasers in correspondence with amplification ranges having different amplification gains. FIG. 16A shows a relationship between the amplification gains of a CO2 gas laser and light intensity of each semiconductor laser in the single longitudinal mode. For example, laser beams having five kinds of wavelengths outputted from five semiconductor lasers 1-5 are assigned to an amplification line P(22) in the band of transition 00° 1-02° 0 and amplification lines P(18), P(24), P(26), P(28) in the band of transition 00° 1-10° 0, respectively. Since gains are different among those amplification lines, intensity and wavelength of each semiconductor laser is adjusted in agree with the gain at respective one of the amplification lines. Specifically, intensity of the semiconductor laser beam, which is assigned to an amplification line with a large gain, is set small, while intensity of the semiconductor laser beam, which is assigned to an amplification line with a small gain, is set large. Thereby, as shown in FIG. 16B, it becomes possible that light intensity of plural lines is made substantially uniform. As a result, the amplification efficiency is improved in comparison with that in a single-line amplification. Although the multiline amplification in a CO2 laser is simply explained in a schematic manner in this embodiment, a regenerative amplifier may be used according to need, in order to efficiently amplify seed pulse light having small light intensity after semiconductor laser beams are combined. Further, plural preamplifiers or plural main amplifiers may be arranged in serial for amplification, in order to obtain high output. In the case where the above-mentioned CO2 laser system for performing multiline amplification is used as the driver laser of the EUV light source apparatus, in the SPF as shown in FIG. 2 or 5, a pitch of the arrangement of apertures is set equal to or less than a half of the shortest wavelength among wavelengths of a CO2 laser beam applied by the driver laser. Further, in the SPF as shown in FIG. 12, a pitch of the wires is set equal to or less than a half of the shortest wavelength among wavelengths of a CO2 laser beam applied by the driver laser. For example, in the case where the shortest wavelength among wavelengths of a CO2 laser beam applied by the driver laser is 9.56 μm, the pitch of the apertures or the pitch of the wires is set equal to or less than 4.78 μm.
	summary
	abstract	A device is for identifying glove-port positions to be mounted on a panel supported by a glovebox structure which defines a closed chamber enabling an operator to perform handling operations while being isolated from the chamber. The device includes a base, structure for attaching this base to the glovebox structure, and at least one template supported by this base while being movable with respect to this base, in order to be able to occupy different positions with respect to this base. Each template includes an opening which can receive a glove port. The device also includes structure for locking each template in position with respect to the base.
052563383	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidifying material and a waste container suitable for the final disposal of radioactive wastes generated from a nuclear power plant and the like, a structure for disposal, a back-filling material, and a process for solidifying radioactive wastes. 2. Description of the Related Art Hitherto, hydraulic inorganic solidifying materials such as cement and water-glass (sodium silicate) have been used for waste containers, solidifying materials, back-filling materials and structures for disposal site of so-called a low level radioactive waste such as a concentrated liquid waste, a spent ion exchange resin and various solids generated from nuclear power plants and nuclear fuel reprocessing facilities. The above-mentioned hydraulic inorganic solidifying materials have the merits of (1) an easy operation, (2) an inexpensiveness and (3) an excellent radiation resistance and are suitable for disposal of low level radioactive wastes. Furthermore, for a disposal of low level radioactive wastes, it is necessary that the solidifying materials can maintain safety even under such a condition that solidifying materials or disposal facilities sink under the water and besides can greatly retard leakage of internal radioactive nuclides out of the waste forms or disposition facilities. A conventional method for assuring long-term endurance of waste forms is to add glass fibers to hydraulic solidifying materials as described in Japanese Patent Kokai (Laid-Open) No. 60-202398. Since fibrous materials have tensile strength several times that of the base hydraulic solidifying materials, they have a reinforcing effect to remarkably improve tensile strength and flexural strength of the whole waste form. Therefore, even if the waste form undergoes a change in volume of the filler or is applied with an external force, cracks or breakage of the waste form do not occur and even in the case of the waste form being disposed into the land, it is considered that the waste form can never deteriorate during from several ten years to several hundred years in which radioactivity decays to sufficiently low level. Furthermore, for retardation of leakage of radioactive nuclides, Japanese Patent Kokai (Laid-Open) No. 58-40000 has proposed to provide a protective layer for a waste container for radioactive wastes and to embed a filler having ion exchangeability and adsorbability in this protective layer. Among the above-mentioned conventional methods, the method described in Japanese Patent Kokai (Laid-Open) No. 60-202398 does not consider reduction of leaching rate of radioactivity from wastes and has the problem that a countermeasure to reduce leaching rate of radioactivity is required when wastes higher in level of radioactivity than the present level are disposed of or when wastes containing carbon-14 or technetium-99 longer in half-life are disposed of. On the other hand, since the invention disclosed in Japanese Patent Kokai No. 58-40000 has not the property to improve the strength of the waste container, the invention has a problem that cracks occur in the waste container due to the cycles of dry/wet and hot/cold of the disposal site, and hence the maintenance of soundness thereof is impossible. SUMMARY OF THE INVENTION The object of the present invention is to provide solidifying materials, for disposal of radioactive waste (solidifying materials for making waste form, back-filling materials used in disposal site and so on) and structures for radioactive waste disposal (waste containers, structures of disposal site and so on) which can simultaneously attain improvement of long-term endurance of waste form and the like and reduction of leaching rate of radioactivity from waste form and the like. The above object has been attained by adding fibrous materials having property to adsorb onto the surface the radioactive nuclides in the form of ion or molecule to cement type hydraulic solidifying materials which are used for solidifying materials for disposal of radioactive wastes (solidifying materials for making waste forms and back-filling materials used in disposal site), waste containers and structures of disposal site. The fibrous materials which have the property to adsorb on the surface thereof the radioactive nuclides in the form of ion or molecule and are added to cement type hydraulic solidifying materials as a base material have the following actions. Since the fibrous materials have a tensile strength several times the strength of said base material, they have an action to enhance tensile strength of final hardened bodies depending on the addition amount thereof. Besides, from the point of fracture mechanics, the above fibrous materials have an action to stop the development of cracks which have occurred in the hardened bodies and hence can markedly increase brittle fracture value of set bodies which are inherently brittle materials and can inhibit deterioration of the waste forms. Especially, when solidifying materials, waste containers, structures of disposal site and back-filling materials which concern with disposal of radioactive wastes undergo wet-and-dry cycle or temperature cycle, cracks may occur in hardened bodies. Leakage of radioactivity from waste forms of wastes when they sink under the water is accelerated owing to these fine cracks. When the above-mentioned fibrous materials are added, not only the final tensile strength of the waste forms is improved, but also generation of fine cracks and development thereof can be prevented not so as to affect mechanical strength. Therefore, increase of leaching rate of radioactivity from waste forms can be prevented even under such severe environmental conditions as dry-and-wet cycle or temperature cycle. Furthermore, since the fibrous materials have the property to adsorb radioactive nuclides in the form of ion and molecule, distribution coefficient of the solidifying materials as base materials for radioactive nuclides can be improved by the addition of the fibrous materials and leaching rate of radioactivity from waste form can be diminished.
	summary
046631097	description	DETAILED DESCRIPTION OF THE INVENTION The present invention generates stellarator fields having favorable properties (magnetic well and large rotational transform) by a simple coil system consisting only of unlinked planar non-circular coils. At large rotational transform toroidal effects on magnetic well and rotational transform are small and can be ignored. We do so herein, specializing in straight helical systems. FIG. 1 shows a typical coil configuration for a modular stellarator of the present invention. Note that only a segment of the helix is shown and that no vacuum vessel is shown. The vacuum vessel would lie within the toroidal field coils 10 and the vessel axis should be substantially parallel (and usually coaxial) to the axis traced by the centers of the coils, X(s). In an actual stellarator, X(s) is a closed curve, the vacuum vessel a torus, and the coils equally spaced along the helical axis. Coils 10 in FIG. 1 are somewhat "bean" shaped, with the cusp portion of the bean being positioned towards the center of the stellarator. For "D" shaped coils, the flat portion of the coil would be positioned towards the center of the stellarator as shown in FIG. 4. Referring to FIG. 1, the centers of the coils trace out a helix, the location of which is given in x, y, z coordinate system by: EQU X(z)=z z+r.sub.o cos kz x+r.sub.o sin kz y (1) where r.sub.o is the coil displacement from the z axis, 2/k the periodicity length, m the period, and kr.sub.o the pitch. If s defines the distance along the coil axis, X(s) defines the coil axis. Our method of solving for the magnetic field generated by these coils is an analytical expansion about the coil axis. The expansion parameter is: ##EQU2## where a.sub.c is the coil radius and r.sub.h the helical radius of curvature. The smaller this quantity is, the easier it is to get a magnetic well. Note that if this expansion parameter approaches one, coils perpendicular to the axis collide. Requiring the expansion parameter to be small is reasonable since any stellarator that would be built would satisfy the condition: coil diameter small compared to the length of a stellarator period. In a helical coordinate system .rho., .theta., s, a general vector is given by: EQU r=X(s)+n(s).rho. cos .theta.+b(s).rho. sin .theta., (3) where the relationship between .rho. and .theta. is shown in FIG. 1A. In helical symmetry the magnetic field depends only on .rho. and .theta.. Hence, the curve of each coil is given by: EQU .rho.=a.sub.c +.delta..sub.2 cos 2.theta.+.delta..sub.3 cos 3.theta.(4) where a.sub.c, .delta..sub.2, and .delta..sub.3 are constants, and at least one of .delta..sub.2 and .delta..sub.3 is nonzero. In equation 4, .delta..sub.2 determines the ellipticity of the coil and .delta..sub.3 determines the triangularity. As .delta..sub.3 increases from 0, the coils first become increasingly "D" shaped, then somewhat "bean" shaped. Equation 4 reduces to the equation for a circular coil when .delta..sub.2 =.delta.3=0. Note that the coils are perpendicular to the coil axis, which is equivalent to having the s component of the coil current vanish. From the above, rotational transform is given by: ##EQU3## where m is the number of periods. When there is a magnetic well, a.sub.c, .delta..sub.2, and .delta..sub.3 are determined by: ##EQU4## Equation 6 gives the coil triangularity required to produce a magnetic well for a given coil ellypticity, .delta..sub.2, and a given pitch, kr.sub.o, of the coil axis. Preferably, a nonzero ellipticity and triangularity are both required to get a good magnetic well from a planar coil (both .delta..sub.2 and .delta..sub.3 .noteq.0). FIG. 2 is a contour plot of the required value of (r.sub.o /a.sub.c) (.delta..sub.3 /a.sub.c) as given by equation 6. EXAMPLE Taking kr.sub.o .perspectiveto.1, we obtain from FIG. 2 a magnetic well and large transform with a reasonable coil deformation. FIG. 3 shows a coil cross-section and corresponding magnetic flux surfaces for kr.sub.o =1, .delta..sub.2 /a.sub.c =-0.3, and .delta..sub.3 /a.sub.c =-0.1. Note that the cusp portion of this "bean" shaped coil is positioned towards the center of the stellarator (center of curvature). For this configuration, calculating rotatinal transform from equation 5, .chi./m.perspectiveto.0.43. Assuming a stellarator having m=4, and aspect ratio of 4, we obtain a beta of 37% ##EQU5## For a larger stellarator having m=10 and aspect ratio of 10, we obtain a beta of 92%. Smaller helical aspect ratios require an increasingly "bean" shaped coil (i.e. increasing triangularity) to maintain a well, whereas a "D" shaped coil is sufficient at larger helical aspect ratio.
	summary
	description	The present invention relates to a grid for spacing nuclear fuel rods in a nuclear fuel assembly, the grid being of the type defining a substantially regular array of cells and including a peripheral belt, the peripheral belt having guide fins on at least one of its edges. The invention applies in particular to fuel assemblies for pressurized water nuclear reactors. Document FR—2 736 190 describes a spacer grid of the above-specified type. The peripheral belt is made up of plane outer plates that are assembled to one another. The guide fins are folded relative to the planes of their respective plates towards the inside of the grid. Such a grid makes it possible to reduce the lateral deformation of the assembly that includes it. Inclining the fins inwards serves in particular to limit any risk of the spacer grids of two adjacent assemblies catching while the assemblies are being handled. Nevertheless, a risk still exists of grids catching in certain configurations that are particularly penalizing. This applies in particular when two adjacent assemblies are offset by half the pitch of the array of fuel rods. During a handling operation, the free ends of the guide fins of one grid in a first one of the adjacent assemblies can then become engaged between two adjacent fins of a grid in the second of the two adjacent assemblies, thus catching the edge of the grid of the second assembly. If in addition, one of the two assemblies bears laterally against the other of the two adjacent assemblies to such an extent as to cause the peripheral rods of at least one of the two assemblies to bend and/or be displaced laterally, the risk of the grids of the two adjacent assemblies catching is increased. Such catching can lead to adjacent assemblies being deformed and ought therefore to be avoided. An object of the invention is to solve this problem by limiting the risk of the grids of two adjacent assemblies catching. To this end, the invention provides a grid of the above-specified type, characterized in that said edge of the peripheral belt presents setbacks towards the inside of the grid between adjacent guide fins. In particular embodiments, the grid may include one or more of the following characteristics, taken in isolation or in any technically feasible combination: the setbacks are formed by bosses in the peripheral belt; through orifices are formed through the peripheral belt to allow cooling fluid to pass laterally; the through orifices are positioned substantially in the centers of the outside faces of the peripheral cells defined by the peripheral belt; the peripheral belt does not have springs for laterally holding nuclear fuel rods received in the peripheral cells; the grid includes crossed inner plates, which inner plates are surrounded by the peripheral belt; the inner plates present notches for mutually engaging the plates at their cross-points, and the notches have respective regions of reduced width; the guide fins bear against regions of the inner plates that constitute stiffeners; the inner plates adjacent to the peripheral belt include abutments for laterally retaining the nuclear fuel rods, which abutments project into the peripheral cells from their inside faces facing the peripheral belt; the lateral retaining abutments are formed in the bottom edges and the top edges of the inner plates adjacent to the peripheral belt; the peripheral belt presents cups set back towards the inside of the grid and in which the inner plates are welded to the peripheral belt; and the bottom edges of the inner plates are substantially rectilinear in register with the faces of cells that are to receive guide tubes of the nuclear fuel assembly. The invention also provides a nuclear fuel assembly comprising nuclear fuel rods, a skeleton for supporting the rods, the support skeleton comprising guide tubes, nozzles disposed on the longitudinal ends of the guide tubes, and grids for spacing the rods, the assembly being characterized in that at least one grid is a grid as defined above. In order to illustrate the context of the invention, FIG. 1 is a diagram showing a nuclear fuel assembly 1 for a pressurized water reactor. Water thus performs therein both a cooling function and a moderation function, i.e. it slows down neutrons produced by the nuclear fuel. The assembly 1 extends vertically in rectilinear manner along a longitudinal direction A. This direction is the flow direction of the cooling fluid, i.e. water, when the assembly 1 is placed in a core. More precisely, the water flows upwards therethrough. In conventional manner, the assembly 1 mainly comprises nuclear fuel rods 3 and a structure or skeleton 5 for supporting the rods 3. The support skeleton conventionally comprises: a bottom nozzle 7 and a top nozzle 9 disposed at the longitudinal ends of the assembly 1; guide tubes 11 for receiving the rods of a control and stop cluster (not shown) for the nuclear reactor; and grids 13 for spacing the rods 3 apart. The nozzles 7 and 9 are secured to the longitudinal ends of the guide tubes 11. The rods 3 extend vertically between the nozzles 7 and 9. The rods 3 are disposed at the nodes of a substantially regular square-based array where they are spaced apart laterally by the grids 13. Some of the nodes of the array are occupied by the guide tubes 11, and possibly also by a central instrumentation tube. Generally, the top grid 13 and possibly the bottom grid 13 serve not only to hold the rods spaced apart laterally as mentioned above, but also to support the rods 3 longitudinally. The other grids 13 serve solely to space the rods apart laterally. Below, the invention is described with reference to an intermediate grid 13, i.e. a grid that serves only to provide lateral spacing. Nevertheless, it can also be applied to grids 13 that also perform a function of supporting rods 3. As shown in FIGS. 2 to 5, the grid 13 comprises: crossed inner plates 15; and a peripheral belt 17 surrounding the inner plates 15 and made up of outer plates 19. FIGS. 6 and 7 show two of the sixteen different inner plates 15 used for making the grid 13. Between them, the inner and outer plates 15 and 19 define a square array of cells 21 and 23. In the example shown, this array comprises 17×17 cells, however in other variants the grid 13 could comprise some other number of cells, e.g. 15×15, 16×16, . . . . Numerical reference 21 designates the inner cells, i.e. those that are defined solely by inner plates 15. Numerical reference 23 designates the peripheral cells that are bordered by the peripheral belt 17 and that are therefore defined both by the belt and by inner plates 15. The cells 21 and 23 are centered on the nodes of the array of fuel rods 3, and for the most part they receive the fuel rods 3. Some of the cells 21 receive guide tubes 11, and the central cell 21 can receive a central instrumentation tube. Each cell 21, 23 in plan view is substantially square in shape and thus presents four side walls that are opposite in pairs. The peripheral belt 17 in plan view is substantially square in shape with four corners 25. Each outer plate 19 forms one of the corners 25; and the plates 19 are assembled together in regions 27 that are distinct from the corners 25, e.g. by being welded together. The outer plates 19 present cups 29 for assembly with the inner plates 15. These cups 29, e.g. made by stamping, are set back towards the inside of the grid 13 and they extend longitudinally across the plates 19. They are pierced to receive the lateral ends of the inner plates 15 which are welded in the bottoms of the cups 29. The lateral ends of the plates 15 situated in register with assembly regions 27 are held captive by the lateral edges of the adjacent outer plates 19. In the example described, the peripheral belt 17 does not present any cups 29 in the assembly regions 27. The plates 19 of the peripheral belt 17 also present orifices 31 for allowing the cooling fluid to pass laterally. In the example shown, these orifices 31 are circular and they are positioned halfway up the belt 17. Each orifice 31 opens out into a peripheral cell 23 and is substantially centered relative to said peripheral cell 23. In other words, the orifice 31 is substantially in register with the longitudinal axis of the rod 3 received in the peripheral cell 23 in question. In register with the junctions with the plates 15, the peripheral belt 17 has fins 33 for guiding an assembly 1 adjacent to the assembly in question, and for guiding the cooling fluid. These guide fins 33 project upwards and downwards and they are folded towards the inside of the grid 13. Between the guide fins 33, the bottom and top edges 35 and 37 of the belt 17 present setbacks 39 towards the inside of the grid 13. The setbacks 39 formed in the bottom edge 35 extend upwards and the setbacks 39 formed in the top edge 37 extend downwards such that in face view the setbacks 39 are oblong in shape. The setbacks 39 are made by stamping the outer plates 19 towards the inside of the grid 13 so as to form bosses 40 projecting towards the insides of the peripheral cells 23. As shown more particularly by FIGS. 4, 6, and 7, the inner plates 15 have stiffeners 41 at their lateral ends projecting upwards and downwards and against which the fins 33 bear. The fins 33 may be welded to the stiffeners 41. Inside an inner cell 21 receiving a rod 3, the rod 3 is held laterally by dimples 43 made by cutting and embossing the metal of the inner plates 15, and also by springs 45, e.g. fitted on the inner plates 15. More precisely (FIG. 5), for each inner cell 21, each of the faces of the cell 21 is provided either with a pair of dimples 43 projecting towards the inside of the cell, or with a spring 45, each spring 45 facing a pair of dimples 43. Concerning those cells 21 that are to receive guide tubes 11, it can be seen that the inner plates 15 are also provided with welding tabs 46 that project upwards from the lateral faces of each cell 21 in question, and that are for welding to the guide tubes 11. These tabs 46 are shorter than in the prior art, for example they have a height of 8 mm. Concerning the peripheral cells 23, and as shown in FIG. 5, the rods 3 that are received therein are held laterally in each cell 23 by two springs 45, a pair of dimples 43, and a pair of bosses 40. The bosses 40 formed in the peripheral belt 17 face one of the springs 45, and the pair of dimples 43 likewise face one of the springs 45. For the peripheral cells 23 situated in the corners 25, the rods are held by two springs 45 and by two pairs of circular dimples 48 formed in the peripheral belt 17 and facing the springs 45. For each of the peripheral cells 23, including the corner cells 23, the inner face(s) opposite the peripheral belt 17 is/are provided with a pair of abutments 47 for laterally retaining the rod 3 received in the cell 23 in question. These abutments 47 are formed in the inner plates 15 lying beside the peripheral belt 17. One such inner plate 15 is shown in FIG. 6 where it can be seen that for each cell 23 one of the abutments 47 is situated at the bottom edge 49 of the plate 15, and the other at the top edge 51 of the plate 15. These abutments 47 are formed by cutting and embossing the material of the plate 15 towards the insides of the cells 23 in question. In the example described, each pair of abutments 47 lies on either side of a spring 45 facing the peripheral belt 17. Also in this example, the peripheral belt 17 is not provided with a spring for holding the peripheral rods 3 laterally. It should be observed that the bottom edges 49 of the bottom plates 15 are rectilinear in the faces 53 of the cells 21 that receive the guide tubes 11 (FIGS. 3 and 7). In particular, these faces 53 do not present any bottom cutout as in the prior art, thereby improving the ability of the grid 13 to withstand buckling. In order to assemble the plates 15 at their cross-points, notches 55 are formed in the plates 15. For half of the plates, the notches 55 open out into their bottom edges 49, for the other half, the notches 55 open out into their edges 51, thus enabling all of the inner plates 15 to be mutually engaged via their notches 55. As shown very diagrammatically in FIG. 8, each notch 55 presents at its open end a constriction 57 leading to the corresponding edge 49 or 51 via chamfers 59. These chamfers 59 make it easier to engage the inner plates 15 mutually via the notches 55 at their cross-points. The constrictions 57, which correspond to a reduction in width of the order of 100 micrometers (μm) to 200 μm, for example, serve to provide satisfactory mechanical retention between the inner plates 15 at their cross-points. This makes it possible locally to reduce clearance between the mutually engaged inner plates 15 and thus to improve the quality of the welding performed subsequently at the cross-points. FIGS. 9 and 10 show the configuration mentioned in the introduction of the present description, constituting one of the situations in which the risk of catching between two adjacent assemblies 1 used to be the greatest. In FIG. 9, there can be seen the peripheral belts 17 of two grids 13 of two adjacent assemblies 1. These two grids 13 are offset laterally by half the pitch of the arrays of nuclear fuel rods. The bottom grid 13 belongs to a first assembly 1 and the top grid 13 belongs to a second assembly 1 that is being handled, which explains why one is situated above the other. Because of the lateral offset, the top fins 33 of the bottom grid 13 lie between the bottom guide fins 33 of the top grid 13 and are engaged in the bottom setbacks 39 of the top grid 13. Similarly, the bottom fins 33 of the top grid 13 are engaged in the top setbacks 39 of the bottom grid 13. Thus, the risk that the free ends of the guide fins 33 of a grid 13 might catch a longitudinal edge of the adjacent grid 13 is small. This risk is made smaller still in that in the event of one of the assemblies 1 pushing the peripheral rods 3 of the other assembly laterally towards the inside, these peripheral rods 3 will come to bear against the abutments 47, thereby limiting both the bending and the displacement of the rods 3 towards the inside of the assembly 1. This is shown in FIG. 10 where the rods 3 directly adjacent to the peripheral rods 3 are omitted. The abutments 47 limit any displacement or bending of the rods 3 to a greater extent by being placed at the bottom and top edges 49 and 51 of the plates 15 adjacent to the peripheral belt 17. The bosses 40 formed by the setbacks 39 in the peripheral belt 17 are disposed at the longitudinal ends of the grid 13 and thus provide good lateral holding and increased restriction on lateral displacement and bending of the rods 3. The use of setback cups 29 for the purpose of welding the peripheral belt 17 to the inner plates 15 likewise makes it possible to limit any risk of adjacent assemblies 1 catching. Thus, the risks of the grids 13 of adjacent assemblies 1 catching are limited, particularly during handling. The presence of the stiffeners 41 for the guide fins 33 serves to increase the stiffness of the guide fins 33 and limits any risk of them deforming, and also any risk of catching that might result from deformation of the outlet plates 19. The orifices 31 serve to increase the transverse hydraulic transparency of the grid 13 and thus to increase the ability of the assembly 1 to withstand buckling, and thus reduce the risk of two adjacent assemblies 1 catching. The characteristics described above, and in particular the setbacks 39, the abutments 47, the constrictions 57, the orifices 31, the stiffeners 41, the cups 29, and the rectilinear bottom edges of the faces 53 of the cells that receive guide tubes 11, can be used independently of one another for achieving the overall object of limiting deformation of nuclear fuel assemblies in a reactor. In certain configurations, the setbacks 39 may be present only at one longitudinal edge of the grid 13.
054830648	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The present invention consists of two main concepts that differentiate it from the prior art. The first one relates to a mode of operation that is based on the permanent alignment of the probe of the instrument with the main axis of the piezoelectric element providing the scanning motion (the instrument may be any type of scanning microscope having the sample stage mounted on the scanning device). The second concept relates to a sample positioning mechanism that allows the precise placement of the target areas of interest in the sample under the tip of the probe between scanning operations without interfering with the sample during scanning. Both concepts are necessarily related because the permanent alignment of the probe and scanning element by definition prevents the use of translational mechanisms to direct the probe to a particular target area on the sample or the target area on the sample to a particular position under the probe, as done heretofore for coarse targeting. Therefore, the sample itself must be moved to place the target area under the probe and a suitable mechanism to effect that movement in efficient fashion between scanning operations must be provided. As is detailed below, a problem of implementation for any such mechanism is its potential interference with the sample as a result of the sample motion during scanning. This problem is solved by providing a stand-off approach for placing the sample stage to the proper position relative to the probe and by incorporating a known amount of take-up gap between the stand-off and the positioning mechanism. It is noted that the embodiments of the present invention are described with reference to x, y and z orthogonal coordinates wherein x and y define a horizontal plane and z defines a vertical direction, but it is obvious that the structure and operation of the features detailed herein could be rotated in any direction with equivalent results. Similarly, reference to translational motion is at times described as coarse in contrast to the very fine movement (in the order of several microns, with control within 0.1.ANG.) provided by the scanning piezoelectric means. In fact, though, as those skilled in the art understand, the positioning of the target area on the surface of a sample directly under the tip of the probe is a very exact operation that requires precision instrumentation and mechanisms. Finally, it is understood that the sizes of the various components shown in the drawings are not drawn to relative scale because of the microscopic dimensions of some features (such as the probe 10 and the x-y motion of the piezoelectric tube 18) in comparison to others illustrated in the FIGURES. Rather, they are represented only schematically for illustration. Referring to the drawings, wherein like parts are designated throughout with like numerals and symbols, FIG. 4 illustrates in schematic view the basic mode of operation and structure of a scanning microscope 30 according to this invention. It comprises a probe 10 having its main axis permanently disposed coaxially with the vertical piezoelectric tube 18 utilized for providing scanning to the system (note that the vertical motion required for making measurements during scanning may be provided by other means). A flat stand-off 32 is slidably mounted on the flat top 34 of the piezoelectric tube 18, thereby being positioned on a horizontal plane substantially subject to x-y movements (and tilt) as a result of voltage gradients applied to the tube 18. A sample 16 is mounted on the stand-off 32 (either directly or through a sample stage, as illustrated below) and positioned with the target area for investigation directly under the tip 36 of the probe 10. Such precise placement is accomplished by a sample-positioning mechanism 40 that is capable of pushing the stand-off 32 in the x-y directions and cause it to slide over the top of the piezoelectric tube 18, thereby also moving the sample 16 to the desired location. It is important to stress the fact that the structural members described schematically in FIG. 4 consist of high-precision, small components that cannot be properly handled or adjusted without the use of precision instrumentation, such as a focused light source and an optical viewfinder, that is also housed within the support structure of the scanning microscope. In addition, depending on the type of scanning microscope with which the present invention is combined, other hardware essential to the functioning of the microscope is also housed within the same support structure, such as means for sensing the movement of the probe and for controlling the vertical distance between the probe and the sample. Therefore, any mechanism 40 used to translate the stand-off and place the target area of the sample under the probe must be operable within minute tolerances in the crowded environment surrounding the probe/sample area. Manual translation would not be acceptable because it is not sufficiently precise to place the sample in the desired spot, even with the aid of a viewfinder, because of the relatively very coarse spatial control of human motion. On the other hand, the use of mechanical devices, either manually or electronically operated, allows fine adjustments to the position of the sample by pushing the stand-off precisely to the point of interest, but then must be removed to avoid continued contact with the standoff which would interfere with its motion during scanning. Accordingly, a sample positioner is needed that is compatible with the overall general configuration of scanning microscopes and is implemented with hardware capable of slidably moving the sample on a horizontal plane and retracting away from any structure connected to the sample to eliminate the possibility of contact during the scanning procedure. FIGS. 5 and 6 illustrate the basic components of the preferred embodiment of a sample positioner according to the invention. FIG. 5 shows an isolated top view of the positioner 40, which consists of a horizontal plate 42 anchored to portions of a support structure 44 that is integral with or rigidly connected to the horizontal base 46 (FIG. 6) that supports the bottom end 48 of the vertically-disposed piezoelectric tube 18. The plate 42 is adapted for horizontal movement in any direction. As illustrated in the FIGURES, this feature may be accomplished by means of orthogonal, horizontally disposed plungers 50 slidably engaged by conforming guides 52 in the support structure 44 together with cooperatively-aligned push-pull mechanisms for sliding the plungers 50 in and out of the guides 52, as necessary in order to effect the desired translation of the plate 42 to target x-y coordinates. The plungers 50 or the plate 42 may be spring-loaded by means of springs 51 pushing against the plungers in the guides 52 (as illustrated in the-drawings) or against the plate 42 to enhance the plate's rapid response in the pull mode. The push-pull mechanisms may consist, for example, of screw gears 54 attached to the plate 42 (or simply pushing against a springloaded plate) and engaged by drive-gear devices 56 mounted on the support structure 44. As is clearly understood in the mechanical arts, each screw gear 54 so disposed is capable of bidirectional linear motion, thus providing, in combination, the push-pull function required to effect translation of the plate 42 to any x-y coordinates within the range of the screw gears 54. Obviously, a simple screw or set of screws rotatably mounted on the structure 44 and adapted for pushing on the plate 42 would provide equivalent function, but such an arrangement would not be suitable for automatic control. The drive-gear devices 56 may be actuated manually, such as by means of a rotating knob, or mechanically, such as by high-precision stepper motors, possibly through a system of reducing gears that ensure microscopic motion of the plate 42 for each turn of a drive gear. Any alternative mechanism that would permit the precise motion of the plate 42 in the x-y plane would be equivalently suitable to practice the invention. The plate 42 contains an opening 58 sufficiently large to surround a coplanarly-disposed stand-off 32 adapted for slidable coupling with the top end 60 of the piezoelectric tube 18, preferably through an intermediate scanning stage 62 made of low-friction material that is fixedly attached to the piezoelectric tube (FIG. 6). The relative sizes of the opening 58 and the stand-off 32 are chosen so that a sufficient horizontal take-up gap h is present in all directions when the two are coaxially aligned to ensure the unobstructed horizontal movement of the stand-off 32 as the top end 60 of the piezoelectric tube moves in the x-y plane as a result of scanning voltages applied to it. (The gap h is seen in FIG. 5 in the partially cut-away portion of the lip 64, which is described in detail below.) Although any shapes for the opening 58 and stand-off 32 that allow this condition to be met are acceptable to practice the invention, a circular stand-off and a substantially square opening are preferred. To the extent that the stand-off would never come into contact with the corners of the square (it can only come to within a distance equal to its radius), the precise shape of the opening 58 in the vicinity of the corners (illustrated by rounded corners in the FIGURES) is irrelevant to the functioning of the apparatus. If applicable for the particular type of scanning microscope combined with the invention, a vertical gap v must also be left between the top surface of the scanning stage 62 (or of the piezoelectric tube 18, if a scanning stage is not used) and the bottom surface of the plate 42 in order to ensure the unobstructed vertical movement of the scanning stage (and correspondingly of the stand-off and sample) as the top end 60 of the piezoelectric tube 18 moves in the z direction as a result of vertical positioning voltages applied to it. Inasmuch as the horizontal range of typical piezoelectric elements is about 100 microns, a horizontal gap h larger than about 50 microns is sufficient for these purposes. Similarly, since the vertical measurements, and therefore the vertical range required for the piezoelectric element, are in the order of about 15 microns, a vertical gap v of a fraction of a millimeter is suitable to practice the invention. Thus, a sample 16 mounted on top of a sample stage 38 may be moved in the x-y plane as needed to place the specific target area to be scanned directly under the tip of the probe 10. This is accomplished by pushing or pulling, as necessary, the stand-off 32 in the x and y directions by the amount required to meet the target position. The plate 42 is then retracted by an amount sufficient to disengage the stand-off 32 and ensure a horizontal gap h around the entire edge of the stand-off. Since the take-up gap h is predetermined by the dimensions and geometry of the assembly and corresponds to a fixed motion of the devices 56 (such as, for example, a certain number of turns of the screw gears 54) this step may be easily implemented automatically so as to avoid reliance on a user for fine adjustments of the positioner plate 42. Obviously, during the translational movement of the stand-off, the horizontal motion of the plate 42 must also be unobstructed in all directions by any of the components constituting the hardware of the invention and a sufficient range must be provided to reach each end of the sample 16 being analyzed. Typically, sample dimensions have been limited to several millimeters because of the tilt-distortion problems that this invention is addressing, but a sample of any size could be analy in equivalent fashion by the arrangement illustrated in FIGS. 5 and 6. Therefore, the range of horizontal movement of the plate 42 need only be commensurate with the expected size of the samples analy by the scanning microscope. FIG. 7 illustrates in more detail the stand-off portion of the preferred embodiment shown schematically in FIGS. 5 and 6. Since a very small horizontal take-up gap h (in the order of 150.mu.) is sufficient to ensure the free scanning motion of currently available piezoelectric elements 18, the stand-off can be incorporated as a free-moving but coupled component of the positioner 40 by providing lips 64 along the outer edge of the stand-off extending over a conforming inner edge 66 of the opening 58. By carefully sizing the inner diameter of the stand-off 32 (at the side edge 65) in relation to the dimensions of the opening 58, the desired gap h may be maintained around the stand-off 32 even though the outer diameter of the stand-off (at the lips) is larger than the opening 58, thus ensuring that the stand-off is loosely engaged by the plate 42, as illustrated in the plan view of FIG. 8. In practice, a gap h of about 500.mu. is preferred because of standard machining tolerances that would render prohibitively expensive the manufacture of components with a smaller, more precise gap. Thus, a gap of approximately 500.mu. is suitable for manufacturing purposes and is well outside the scanning range on conventional piezoelectric scanners. Obviously, the precise width of the lips 64 is not critical so long as sufficient to overlap the opening 58 and provide interlocking connection with the plate 42. In operation, the plate 42 is actuated to position the portion of the sample to be scanned directly under the tip of the probe 10, which is aligned with the axis A of the scanning element 18. Then the plate is moved back from the stand-off by an amount sufficient to leave at least a gap h in all directions. Since this distance is predetermined, this step is easily accomplished either manually or automatically, such as by knowing the corresponding turns of the actuating gears or screws necessary to effect a desired translation both in the x and y directions after the sample has reached its intended position. In FIG. 7, for example, the sample is shown as being positioned for scanning of its left edge after a corresponding translation of the stand-off 32 and sample stage 38 toward the right side of the FIGURE. As understood from the FIGURE, scanning may now occur according to conventional processes with the probe 10 coaxially aligned with the scanning tube 18 within the tolerances of the gap h in all directions, so that minimal distortions are produced by the tilt of the top surface 34 of the tube. Note that the concepts of the invention may be easily integrated by those skilled in the art with automated systems normally used to operate scanning microscopes. For example, as illustrated schematically in FIG. 9, the operation of the sample positioner 40 may be controlled manually by a directional lever 72, such as a joy stick, in response to visual input received through a viewfinder 74 focused on the tip of the probe 10 or through a video screen 76 connected to such viewfinder. A microprocessor 78 would normally be utilized to actuate the mechanisms effecting the motion of the sample positioner 40 in response to movements of the lever 72 and the system would preferably be programmed to cause the plate 42 to retract a predetermined, fixed distance h in response to a signal that the sample had reached a desired target location. In this mode of operation, the take-up gap h is set automatically and independently of any control action by the user, which enables rapid response and uniformity of results. In the best mode of the invention, a scanning stage 62 made of low-friction ferromagnetic material is fixedly mounted on the top 34 of the scanning element: 18 and a magnet 68 is embedded in the lower portion of the stand-off 32, which is also made with low-friction material, to provide firmer coupling between the two. Thus, the stand-off is readily slidable over the scanning stage during the placement operation but is securely connected to it during the scanning stage. Similarly, the sample stage 38 may also be made of ferromagnetic material and a magnet 70 (which may be combined with magnet 6 in a single magnetic unit) may be provided to improve mounting of the sample stage over the stand-off 32. Obviously, in both cases the stand-off may equivalently be made of ferromagnetic material and the magnets incorporated into the top of the scanning element or of the sample stage, as applicable. Various changes in the details, steps and materials that have been described may be made by those skilled in the art within the principles and scope of the invention herein illustrated and defined in the appended claims. For example, it is clear that the usefulness of the concept of coaxial alignment between the probe and the scanning means is not limited to piezoelectric tubes; rather it may be used advantageously with any scanning means that produces a tilt of the sample as a result of the scanning motion. Therefore, while the present invention has been shown and described herein in what is believed to be the most practical and preferred embodiments, it is recognized that departures can be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent processes and products.
052522580	claims	1. A method for recovering radioactive iodine from an off-gas generated when spend nuclear fuel is being reprocessed, which comprises passing the off-gas through a scrubbing solution capable of dissolving the radioactive iodine to separate the radioactive iodine from the off-gas, adding a compound to the scrubbing solution which forms a precipitate with the radioactive iodine dissolved in the scrubbing solution, and freeze drying the scrubbing solution containing the precipitated radioactive iodine. 2. A method according to claim 1 wherein the scrubbing solution contains sodium hydroxide. 3. A method according to claim 2, wherein the compound contains cooper ion or silver ion. 4. A method according to claim 1, wherein the product obtained on freeze drying is mixed with a naturally occurring iodine-containing compound and the mixture is mineralized by the application of high pressure in a high pressure press.
	abstract	A navigation system for easily determining defective positions is provided. In the case of CAD navigation to defective positions, logical information for indicating defective positions is created in a CAD format, instead of CAD data of physical information indicating circuit design. Specifically, by attaching marks such as rectangles, characters, or lines, to an electron microscope image with software, quick navigation is performed with required minimum information. By using created CAD data, re-navigation with the same equipment and CAD navigation to heterogeneous equipment are performed.
	claims	1. A boiling water reactor, comprising:a reactor pressure vessel;a core disposed in said reactor pressure vessel and loaded with a plurality of fuel assemblies including transuranic nuclides; anda coolant supplying apparatus which supplies a coolant to said core,wherein a ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly, which is loaded in said core, with a burnup of 0 is 3% or more but 45% or less; andin said fuel assembly having a channel box and a plurality of fuel rods disposed in said channel box, a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 2. The boiling water reactor according to claim 1,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 3. The boiling water reactor according to claim 1,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 4. The boiling water reactor according to claim 1,wherein said core is a parfait core being disposed axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 5. The boiling water reactor according to claim 1,wherein said core is a one fissile zone core being disposed axially an upper blanket zone, a fissile zone, and a lower blanket zone in turn from a top thereof. 6. The boiling water reactor according to claim 1, wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with said burnup of 0 is 3% or more but 15% or less. 7. The boiling water reactor according to claim 1, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 8. The boiling water reactor according to claim 7, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 9. A boiling water reactor, comprising:a reactor pressure vessel;a core disposed in said reactor pressure vessel and loaded with a plurality of fuel assemblies including transuranic nuclides; anda coolant supplying apparatus which supplies a coolant to said core,wherein a ratio of Pu-239 in all Pu elements included in said fuel assembly, which is loaded in said core, with a burnup of 0 is 3% or more but 50% or less, and a ratio of Pu-240 in said all Pu elements is 35% or more but 45% or less; andin said fuel assembly having a channel box and a plurality of fuel rods disposed in said channel box, a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 10. The boiling water reactor according to claim 9,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 11. The boiling water reactor according to claim 9,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 12. The boiling water reactor according to claim 9,wherein said core is a parfait core being disposed axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 13. The boiling water reactor according to claim 9,wherein said core is a one fissile zone core being disposed axially an upper blanket zone, a fissile zone, and a lower blanket zone in turn from a top thereof. 14. The boiling water reactor according to claim 9, wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with said burnup of 0 is 3% or more but 15% or less. 15. The boiling water reactor according to claim 9, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 16. The boiling water reactor according to claim 15, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 17. A boiling water reactor comprising:a reactor pressure vessel;a core disposed in said reactor pressure vessel and loaded with a plurality of fuel assemblies including transuranic nuclides;a coolant supplying apparatus which supplies a coolant within said reactor pressure vessel to said core by pressurizing said coolant; anda coolant flow rate control apparatus which adjusts a flow rate of the coolant supplied to said core by controlling said coolant supplying apparatus, and said coolant flow rate control apparatus setting a coolant flow rate in an operation cycle to a set coolant flow rate which is determined based on a ratio of Pu-239 in transuranic nuclides included in said fuel assembly with a burnup of 0, which is loaded in said core before an operation starts in said operation cycle, so that ratios of a plurality of isotopes of transuranic nuclides present in said core upon the completion of said operation in said operation cycle are substantially the same as ratios of said plurality of isotopes in a state in which said operation in said operation cycle can be started;wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with a burnup of 0 is 3% or more but 45% or less; andwherein in said fuel assembly having a channel box and a plurality of fuel rods disposed in said channel box, a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 18. The boiling water reactor according to claim 17,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 19. The boiling water reactor according to claim 17,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 20. The boiling water reactor according to claim 17,wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with said burnup of 0 is 3% or more but 15% or less. 21. The boiling water reactor according to claim 20,wherein said core is a parfait core being disposed axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 22. The boiling water reactor according to claim 20,wherein the state in which said ratios of said plurality of isotopes of transuranic nuclides present in said core upon the completion of said operation in said operation cycle are substantially the same as ratios of said plurality of isotopes in a state in which said operation in said operation cycle can be started, is a state in which ratios of a plurality of isotopes of transuranic nuclides present in said fuel assembly taken out of said core are substantially the same as ratios of said plurality of isotopes present in said fuel assembly with a burnup of 0, which is to be loaded in said core. 23. The boiling water reactor according to claim 17,wherein said core is a parfait core being disposed axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 24. The boiling water reactor according to claim 17,wherein said core is a one fissile zone core being disposed axially an upper blanket zone, a fissile zone, and a lower blanket zone in turn from a top thereof. 25. The boiling water reactor according to claim 17, further comprising:a plurality of control rods; anda control rod drive control apparatus which controls an operation of said control rods based on a measured reactor power. 26. The boiling water reactor according to claim 17, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 27. The boiling water reactor according to claim 26, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 28. A core of a boiling water reactor, having a plurality of fuel assemblies including a plurality of isotopes of transuranic nuclides,wherein a ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly loaded in said core with a burnup of 0, is 3% or more but 45% or less;wherein said fuel assembly has a channel box and a plurality of fuel rods disposed in said channel box; andwherein a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 29. The core of a boiling water reactor according to claim 28,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 30. The core of a boiling water reactor according to claim 28,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 31. The core of a boiling water reactor according to claims 28,wherein an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone are axially disposed in turn from a top thereof. 32. The core of a boiling water reactor according to claim 28,wherein an upper blanket zone, a fissile zone, and a lower blanket zone are axially disposed in turn from a top thereof. 33. The core of a boiling water reactor according to claim 28,wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with a burnup of 0 is 3% or more but 15% or less. 34. The core of a boiling water reactor according to claim 33,wherein said core is a parfait core disposing axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 35. The core of a boiling water reactor according to claim 28, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 36. The core of a boiling water reactor according to claim 35, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 37. A core of a boiling water reactor having a plurality of fuel assemblies including a plurality of isotopes of transuranic nuclides,wherein a ratio of Pu-239 in all Pu elements included in said fuel assembly loaded in said core with a burnup of 0 is 3% or more but 50% or less, and a ratio of Pu-240 in said all Pu elements is 35% or more but 45% or less;wherein said fuel assembly has a channel box and a plurality of fuel rods disposed in said channel box; andwherein a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 38. The core of a boiling water reactor according to claim 37,wherein an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone are axially disposed in turn from a top thereof. 39. The core of a boiling water reactor according to claim 38,wherein an upper blanket zone, a fissile zone, and a lower blanket zone are axially disposed in turn from a top thereof. 40. The core of a boiling water reactor according to claim 38,wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with a burnup of 0 is 3% or more but 15% or less. 41. The core of a boiling water reactor according to claim 40,wherein said core is a parfait core disposing axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 42. The boiling water reactor according to claim 37, wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 43. The core of a boiling water reactor according to claim 37, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 44. The core of a boiling water reactor according to claim 43, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 45. A fuel assembly for a boiling water reactor, comprising:a channel box; anda plurality of fuel rods disposed in the channel box, and having nuclear fuel material including a plurality of isotopes of transuranic nuclides,wherein a ratio of Pu-239 in all of said transuranic nuclides included in said nuclear fuel material is 3% or more but 45% or less when a burnup is 0; andwherein a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 46. The fuel assembly according to claim 45,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less when said burnup is 0. 47. The fuel assembly according to claim 45,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40% when said burnup is 0. 48. The fuel assembly according to claim 47,wherein when said burnup is 0, said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but 15% or less. 49. The fuel assembly according to claim 45,wherein an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone are axially disposed in an active fuel length in turn from a top thereof. 50. The fuel assembly according to claim 49,wherein when the burnup is 0, each of said blanket zones includes depleted uranium and does not include said transuranic nuclides, and each of said fissile zones includes said nuclear fuel material including said isotopes. 51. The fuel assembly according to claim 45,wherein an upper blanket zone, a fissile zone, and a lower blanket zone are axially disposed in an active fuel length in turn from a top thereof. 52. The fuel assembly according to claim 51,wherein when the burnup is 0, each of said blanket zones includes depleted uranium and does not include said transuranic nuclides, and each of said fissile zones includes said nuclear fuel material including said isotopes. 53. The fuel assembly according to claim 45,wherein ratios of said plurality of isotopes of said transuranic nuclides included in said nuclear fuel material when said fuel assembly is taken out of a core are substantially the same as ratios of said plurality of isotopes included in said nuclear fuel material when said fuel assembly is loaded in said core and has a burnup of 0. 54. The fuel assembly according to claim 45, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 55. The fuel assembly according to claim 54, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of the moderator surrounding said fuel rod in a hexagonal shape in cross section. 56. A fuel assembly for a boiling water reactor, comprising:a channel box; anda plurality of fuel rods disposed in the channel box, and having nuclear fuel material including a plurality of isotopes of transuranic nuclides;wherein a ratio of Pu-239 in all Pu elements included in said nuclear fuel material is 3% or more but 50% or less when a burnup is 0;wherein a ratio of Pu-240 in said all Pu elements is 35% or more but 45% or less when said burnup is 0; andwherein a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 57. The fuel assembly according to claim 56,wherein an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone are axially disposed in an active fuel length in turn from a top thereof. 58. The fuel assembly according to claim 57,wherein when the burnup is 0, each of said blanket zones includes depleted uranium and does not include said transuranic nuclides, and each of said fissile zones includes said nuclear fuel material including said isotopes. 59. The fuel assembly according to claim 56,wherein an upper blanket zone, a fissile zone, and a lower blanket zone are axially disposed in an active fuel length in turn from a top thereof. 60. The fuel assembly according to claim 59,wherein when the burnup is 0, each of said blanket zones includes depleted uranium and does not include said transuranic nuclides, and each of said fissile zones includes said nuclear fuel material including said isotopes. 61. The fuel assembly according to claim 59,wherein ratios of said plurality of isotopes of said transuranic nuclides being included in said nuclear fuel material when said fuel assembly is taken out of a core are substantially the same as ratios of said plurality of isotopes being included in said nuclear fuel material when said fuel assembly is loaded in said core and has a burnup of 0. 62. The fuel assembly according to claim 56, wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 63. The fuel assembly according to claim 56, wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 64. The fuel assembly according to claim 56, wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with said burnup of 0 is 3% or more but 15% or less. 65. The fuel assembly according to claim 56, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 66. The fuel assembly according to claim 65, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of a moderator surrounding said fuel rod in a hexagonal shape in cross section. 67. A boiling water reactor comprising:a reactor pressure vessel;a core disposed in said reactor pressure vessel and loaded with a plurality of fuel assemblies including transuranic nuclides; anda coolant supplying apparatus which supplies a coolant to said core by pressurizing said coolant; anda coolant flow rate control apparatus which adjusts a flow rate of the coolant supplied to said core by controlling said coolant supplying apparatus, and said coolant flow rate control apparatus sets a coolant flow rate in an operation cycle to a set coolant flow rate which is determined based on a ratio of Pu-239 in transuranic nuclides included in said fuel assembly with a burnup of 0, which is loaded in said core before an operation starts in said operation cycle, so that ratios of a plurality of isotopes of transuranic nuclides present in said core upon the completion of said operation in said operation cycle are substantially the same as ratios of said plurality of isotopes in a state in which said operation in said operation cycle can be started;wherein a ratio of Pu-239 in all Pu elements included in said fuel assembly, which is loaded in said core, with a burnup of 0 is 3% or more but 50% or less;wherein a ratio of Pu-240 in said all Pu elements is 35% or more but 45% or less;wherein said fuel assembly has a channel box and a plurality of fuel rods disposed in said channel box; andwherein a transverse cross section of a fuel pellet in said fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in said channel box, the transverse cross section of the unit fuel rod lattice in said channel box including a transverse cross section of said fuel rod and a transverse cross section of a portion of a moderator surrounding said fuel rod in said channel box. 68. The boiling water reactor according to claim 67,wherein said ratio of Pu-239 in all of said transuranic nuclides is 40% or more but 45% or less. 69. The boiling water reactor according to claim 67,wherein said ratio of Pu-239 in all of said transuranic nuclides is 3% or more but less than 40%. 70. The boiling water reactor according to claim 67, wherein said core is a parfait core being disposed axially an upper blanket zone, an upper fissile zone, an internal blanket zone, a lower fissile zone, and a lower blanket zone in turn from a top thereof. 71. The boiling water reactor according to claim 67, wherein said core is a one fissile zone core being disposed axially an upper blanket zone, a fissile zone, and a lower blanket zone in turn from a top thereof. 72. The boiling water reactor according to claim 67,wherein said ratio of Pu-239 in all of said transuranic nuclides included in said fuel assembly with said burnup of 0 is 3% or more but 15% or less. 73. The boiling water reactor according to claim 67, wherein said channel box is a hexagonal channel box and the transverse cross section of the unit fuel rod lattice which includes the portion of the moderator surrounding said fuel rod in said hexagonal channel box is a hexagonal transverse cross section. 74. The boiling water reactor according to claim 73, wherein the hexagonal transverse cross section of the unit fuel rod lattice includes the transverse cross section of a substantially circular cross section of said fuel rod and a surrounding region of a moderator surrounding said fuel rod in a hexagonal shape in cross section.
053002580	claims	1. A method of separating a mixture of contaminated resin particles from soil particles comprising; a) fluidizing said mixture at a fluid velocity sufficient to entrain substantially all of said resin particles and a first portion of said soil particles, said entrained first portion of said soil particles being of an average particle size smaller than the average particle size of said contaminated resin particles; b) separating and collecting a second portion of said soil particles from said entrained contaminated resin particles and said entrained first portion of said soil particles, said second portion not being entrained in said fluidized mixture; and c) separating said entrained first portion of said soil particles from said entrained contaminated resin particles with particle separation means adapted to collect particles corresponding to the average particle size of said contaminated resin particles. a) fluidizing a mixture of soil particles, and contaminated resin particles having a specific gravity lower than the soil particles, in a fluid and at a fluid velocity sufficient to entrain substantially all of said contaminated resin particles and a first, fines portion of said soil particles, said entrained first portion of said soil particles being of an average particle size smaller than the average particle size of said contaminated resin particles, where, after fluidization said resin particles remain contaminated; and then b) separating and collecting a second portion of said soil particles, comprising a majority of said soil, from said entrained contaminated resin particles and said entrained first, fines portion of said soil particles, said second portion not being entrained in said fluidized mixture; and then c) separating said entrained first, fine portion of said soil particles from said entrained contaminated resin particles with particle separation means adapted to collect particles corresponding to the average particle size of said contaminated resin particles. 2. The method of claim 1 wherein said second portion of said soil particles are separated and collected by settling. 3. The method of claim 1 wherein said first portion of said soil comprises fines, said second portion of said soil comprises the majority of said soil, said particle separation means comprises a screen adapted to collect said contaminated resin particles and allow said fines to pass therethrough, and said fluidizing is achieved with a mineral jig adapted to collect said second portion of said soil in the bottom of said jig and said jig is further adapted to allow said entrained contaminated resin particles and fines to pass in an overflow stream from said mineral jig to said screen. 4. The method of claim 1 wherein said fluidized mixture is passed through a bed of oversized soil particles in order to assist said separation of said contaminated resin particles and said first portion of said soil from said second portion of said soil, said oversized soil particles having an average particle size tending to provide a tortuous path which inhibits settlement of said contaminated resin particles, said oversized soil particles further tending to inhibit channeling of said contaminated resin particles in said fluidized mixture. 5. The method of claim 3 wherein said mineral jig operates at an upflow rate of less than about 5 GPM/ft.sup.2. 6. The method of claim 5 wherein said mineral jig operates at an upflow rate of greater than about 1.6 GPM/ft.sup.2. 7. The method of claim 1 wherein said contaminated resin particles comprise an ion exchange resin. 8. The method of claim 7 wherein said contaminated resin particles are contaminated with heavy metals or organics. 9. The method of claim 8 wherein said contaminated resin particles are contaminated with uranium. 10. The method of claim 1 wherein said mixture of contaminated resin and soil particles is prepared by first mixing uncontaminated resin with contaminated soil to remove contaminants adherent to said resin from said contaminated soil. 11. The method of claim 10 wherein said contaminants are selected from the group heavy metals, radioactive contaminants and organic contaminants. 12. The method of claim 11 wherein said uncontaminated resin is a cation exchange resins. 13. The method of claim 11 wherein said uncontaminated resin is an anion exchange resin. 14. The method of claim 1, wherein the contaminated resin particles have a specific gravity lower than that of the soil, the fluid velocity in step a) exceeds the terminal velocity of the resin and the soil fines particles, the fluidizing is in a fluid in a mineral jig having long pulse strokes, giving the particle more time to settle before the next pulse and having a minimum bed depth, water is the fluid, and after fluidization said resin particles remain contaminated. 15. A method of separating a mixture of contaminated resin particles from soil particles comprising: 16. The method of claim 15 wherein said fluidized mixture is passed through a bed of oversized soil particles in order to assist said separation of said contaminated resin particles and said first portion of said soil from said second portion of said soil, said oversized soil particles having an average particle size tending to provide a tortuous path which inhibits settlement of said contaminated resin particles, said oversized soil particles further tending to inhibit channeling of said contaminated resin particles in said fluidized mixture. 17. The method of claim 15 wherein said mixture of contaminated resin and soil particles is prepared by first mixing uncontaminated resin with contaminated soil to remove contaminants adherent to said resin from said contaminated soil. 18. The method of claim 15 wherein the fluid velocity in step a) exceeds the terminal velocity of the resin and soil fines particles, the fluidizing is in a mineral jig having long pulse strokes, giving the particles more time to settle before the next pulse and containing a minimum bed depth, and water is the fluid.
	summary
	claims	1. A radioisotope elution system, comprising:an auxiliary shield having a top plane, wherein the auxiliary shield comprises at least one radiation shielding material selected from depleted uranium, tungsten, tungsten impregnated plastic, or lead;a shield lid that includes a handle extending from at least two separate locations on a top surface of the shield lid, the shield lid comprising at least one radiation shielding material selected from depleted uranium, tungsten, tungsten impregnated plastic, or lead, wherein the shield lid is disposed in the auxiliary shield, wherein the handle crosses the top plane, and wherein at least one aperture is defined in the top surface and extends through the shield lid; anda radioisotope generator disposed in the auxiliary shield and biased by the weight of the shield lid, wherein the auxiliary shield includes a first complementary alignment structure that is keyed to an alignment structure disposed on the shield lid and a second complementary alignment structure that is keyed to another alignment structure on the radioisotope generator. 2. The radioisotope elution system of claim 1 wherein an elevation of the shield lid within the auxiliary shield is adjustable. 3. The radioisotope elution system of claim 1 wherein the shield lid is in direct contact with the radioisotope generator. 4. The radioisotope elution system of claim 1 wherein the auxiliary shield includes a receptacle defined therein, and wherein the shield lid is shaped to be received in the receptacle. 5. The radioisotope elution system of claim 1 wherein sidewalls of the shield lid are substantially parallel to sidewalls of the alignment structure on the shield lid. 6. The radioisotope elution system of claim 5 wherein the alignment structure on the shield lid is disposed on a bottom portion of the shield lid. 7. The radioisotope elution system of claim 1, wherein the alignment structure on the shield lid extends from a bottom surface of the shield lid. 8. The radioisotope elution system of claim 1, wherein the handle comprises a pair of parallel u-shaped handles. 9. The radioisotope elution system of claim 8, wherein the top surface of the shield lid is recessed below the top plane of the auxiliary shield. 10. The radioisotope elution system of claim 1, wherein the at least one aperture comprises an eluent aperture and an elution tool aperture defined through the shield lid.
	abstract	A device is provided that can capture and store electrically neutral excited species of antimatter or exotic matter (a mixture of antimatter and ordinary matter), in particular, excited positronium (Ps). The antimatter trap comprises a three-dimensional or two-dimensional photonic bandgap (PBG) structure containing at least one cavity therein. The species are stored in the cavity or in an array of cavities. The PBG structure blocks premature annihilation of the excited species by preventing decays to the ground state and by blocking the pickoff process. A Bose-Einstein Condensate form of Ps can be used to increase the storage density. The long lifetime and high storage density achievable in this device offer utility in several fields, including medicine, materials testing, rocket motors, high power/high energy density storage, gamma-ray lasers, and as an ignition device for initiating nuclear fusion reactions in power plant reactors or hybrid rocket propulsion systems.
052375951	abstract	An improved guide plate of the type used in the guide tubes of a nuclear reactor and having a central orifice for conducting coolant, and circular guide holes interconnected by slots for guidingly conducting the movement of control rodlets and control rod vanes through the guide tube is disclosed. The improvement comprises a plurality of vent openings in the form of vent holes uniformly disposed between the slots of the plate and vent gaps disposed between the outer periphery of the guide plate and the inner wall of the guide tube for reducing turbulence in the flow of coolant through the central orifice, thereby advantageously reducing both fretting and frictional engagement between the control rodlets and the guide holes. The resulting turbulence reduction further advantageously reduces the rodlet drop time through the guide tube, thereby enhancing reactor safety. Additionally, the guide holes of the improved guide plate are chrome plated to further reduce frictional engagement between the control rodlets and the plate.
06084938&	abstract	An X-ray projection exposure apparatus includes a mask chuck, a wafer chuck, an X-ray illuminating system, and an X-ray projection system. The masks chuck holds a reflection X-ray mask having a mask pattern thereon. The wafer chuck holds a wafer onto which the mask pattern is transferred. The X-ray illuminating system illuminates the reflection X-ray mask, held by the mask chuck, with X-rays. The X-ray projection optical system projects the mask pattern of the reflection X-ray mask onto the wafer held by the wafer chuck with a predetermined magnification. The mask chuck includes a mechanism for generating static electricity for attracting and holding the reflection X-ray mask by an electrostatic force. The invention also includes a device manufacturing method using such an X-ray projection exposure apparatus to transfer a mask pattern onto the wafer using the X-ray projection exposure apparatus.
	claims	1. A system for forming x-ray images, comprising:a source of x-rays;a mount for holding an object;a scintillator that absorbs x-rays and emits visible photons;an optical system that forms a magnified image of the scintillator; anda means of converting the magnified image of the emitted photons into electronic signals; in whichthe emission of x-rays occurs from a spot with a diameter greater than 10 micrometers formed by the collision of an electron beam with an anode; andthe ratio of the spot size of the x-ray source and the resolution of the optical system is greater than 20. 2. The imaging system of claim 1, in whichthe ratio of the spot size of the x-ray source and the resolution of the optical system is greater than 100. 3. The imaging system of claim 1, additionally comprisinga means of recording of the electronic signals. 4. The imaging system of claim 1, in whichthe scintillator is mounted on a substrate. 5. The imaging system of claim 1, in whichthe scintillator is mounted on a prism. 6. The imaging system of claim 1, in whichthe scintillator comprises LuAG. 7. The imaging system of claim 1, in whichthe means of converting the magnified image of the emitted photons into electronic signals comprises a charge-coupled device (CCD). 8. The imaging system of claim 3, additionally comprisinga system controller that controlsthe motion of the mount for holding an object andthe means of recording of the electronic signals corresponding to the magnified image of the emitted photons. 9. The imaging system of claim 8, in whichthe system controller also controlsthe properties of the x-ray source andthe properties of the optical system. 10. The imaging system of claim 1, in whichan object is placed in the mount for holding an object. 11. The imaging system of claim 1, in whichthe thickness of the scintillator is less than 50 micrometers. 12. The imaging system of claim 10, in whichthe object is selected from the group consisting of:a silicon interposer, a silicon dioxide interposer, an integrated circuit,a printed circuit board, a 3D IC package, a 2.5D IC package, anda multi-chip-module. 13. The imaging system of claim 10, in whichthe object comprises through-silicon vias. 14. The imaging system of claim 10, in whichthe object comprises solder bumps. 15. The imaging system of claim 10, in whichthe angle of the x-rays relative to the object can be adjusted. 16. The imaging system of claim 1, in whichthe energy spectrum of the x-rays can be adjusted. 17. The imaging system of claim 1, in whichthe optical system comprises a microscope objective. 18. A system for forming x-ray images, comprising:a source of x-rays;a mount for holding an object;a scintillator that absorbs x-rays and emits visible photons;an optical system that forms a magnified image of the scintillator; anda means of converting the magnified image of the emitted photons into electronic signals; and in whichan object is placed in the mount for holding an object; and in whichthe distance between the scintillator and the object is less than 1 mm. 19. The imaging system of claim 18, in whichthe scintillator assembly and the object are in contact. 20. The imaging system of claim 18, in whichthe distance between the scintillator and the object is less than 100 micrometers. 21. The imaging system of claim 18, in whichthe emission of x-rays occurs from a spotformed by the collision of an electron beam with an anode; andthe ratio of the spot size of the x-ray source and the resolution of the optical system is greater than 20. 22. The imaging system of claim 18, in whichthe scintillator is mounted on a substrate. 23. The imaging system of claim 18, in whichthe scintillator is mounted on a prism. 24. The imaging system of claim 18, in whichthe scintillator comprises LuAG. 25. The imaging system of claim 18, in whichthe means of converting the magnified image of the emitted photons into electronic signals comprises a charge-coupled device (CCD). 26. The imaging system of claim 18, additionally comprising:a means of recording of the electronic signals; anda system controller that controlsthe motion of the mount for holding an object andthe means of recording of the electronic signals corresponding to the magnified image of the emitted photons. 27. The imaging system of claim 26, in whichthe system controller also controlsthe properties of the x-ray source andthe properties of the optical system. 28. The imaging system of claim 18, in whichthe thickness of the scintillator is less than 50 micrometers. 29. The imaging system of claim 18, in whichthe object is selected from the group consisting ofa silicon interposer, a silicon dioxide interposer, an integrated circuit,a printed circuit board, a 3D IC package, a 2.5D IC package, and a multi-chip-module. 30. The imaging system of claim 18, in whichthe object comprises through-silicon vias. 31. The imaging system of claim 18, in whichthe object comprises solder bumps. 32. The imaging system of claim 18, in whichthe angle of the x-rays relative to the object can be adjusted. 33. The imaging system of claim 18, in whichthe energy spectrum of the x-rays can be adjusted. 34. The imaging system of claim 18, in whichthe optical system comprises a microscope objective. 35. The imaging system of claim 18, in whichthe optical system has an optical axis; and additionally comprisinga means for adjusting the position of the source of x-rayssuch that the source spot of the x-ray emitter within the source of x-rays is not on the optical axis. 36. A method for conducting metrology of an object, comprising:selecting an object for measurement;forming at least one image of the object using the system comprising:a source of x-rays;a mount for holding an object;a scintillator that absorbs x-rays and emits visible photons;an optical system that forms a magnified image of the scintillator;a means of converting the magnified image of the emitted photons into electronic signals; anda means of storing the electronic signals corresponding to the image;analyzing the electronic signals corresponding to the image with a predetermined recipe;determining at least one physical dimension for the object; anddisplaying the at least one physical dimension. 37. A method for conducting inspection of an object, comprising:selecting an object for inspection;forming at least one image of the object using the system comprising:a source of x-rays;a mount for holding an object;a scintillator that absorbs x-rays and emits visible photons;an optical system that forms a magnified image of the scintillator;a means of converting the magnified image of the emitted photons into electronic signals; anda means of storing the electronic signals corresponding to the image;analyzing the electronic signals corresponding to the image with a predetermined recipe for identification of defects; anddisplaying the results of the defect analysis. 38. A system for forming x-ray images, comprising:a source of x-rays;a means for positioning an object to be illuminated by x-rays from the x-ray source;a scintillator that absorbs x-rays and emits visible photons;an optical system that forms a magnified image of the scintillator; anda means of converting the magnified image of the emitted photons into electronic signals; and in whichthe optical system has an optical axis; and additionally comprisinga means for adjusting the position of the source of x-rayssuch that the source spot of the x-ray emitter within the source of x-rays is not on the optical axis of the optical system. 39. The imaging system of claim 38, in whichthe emission of x-rays occurs from a spotformed by the collision of an electron beam with an anode; andthe ratio of the spot size of the x-ray source and the resolution of the optical system is greater than 20. 40. The imaging system of claim 38, in whichthe scintillator is mounted on a substrate. 41. The imaging system of claim 38, in whichthe thickness of the scintillator is less than 50 micrometers. 42. The imaging system of claim 38, in whichthe angle of the x-rays relative to the object can be adjusted. 43. The imaging system of claim 38, in whichthe optical system comprises a microscope objective.
	abstract	A radiation attenuation system is provided. The radiation attenuation system includes a first shield panel formed of a first radiation attenuating material, a second shield panel formed of a second radiation attenuating material, and a frame disposed below the first shield panel and the second shield panel. The frame includes a first end portion defining a first array of slots and a second end portion defining a second array of slots. The first array of slots and the second array of slots are configured to receive the first shield panel and the second shield panel such that the second shield panel is spaced apart from the first shield panel to form a first trough sized to fit a limb of a patient.
050769715	summary	The present invention relates generally to the processing of radioactive materials and, more particularly, to the decontamination of such materials. BACKGROUND OF THE INVENTION One of the most important aspects relating to the use of radioactive materials involves the disposal of waste products and by-products of radioactive material processing and use. Some of these waste and by-products can present continuing health hazards if not properly contained. The length of time necessary for the decay of radioactive materials is typically measured in terms of the "half-life" of the particular decay mechanism. The half-life is a term used to designate the period of time during which one half of the number of original atoms in a given sample will have decayed. Although radioactive decay is a random spontaneous process, its macroscopic properties are mathematically predictable and may be experimentally determined. Thus, the half-life values are relatively well known for most common decay process steps. The most common radioactive atoms found in waste materials and by-products are two isotopes of uranium, uranium 235 (.sub.92 U.sup.235) and uranium 238 (.sub.92 U.sup.238), and one of plutonium namely plutonium 239 (.sub.92 U.sup.238). These three materials all have, as their primary natural radioactive decay mechanism, the emission of alpha particles. Each of these isotopes will eventually decay to a stable material. The first step in the radioactive decay of plutonium 239 is the emission of an alpha particle to produce uranium 235. Thus both plutonium 239 and uranium 235 will follow the same decay pattern. The eventual resulting stable particle obtained from the decay of uranium 238 is lead 206 (.sub.82 Pb.sup.206 ), while that resulting from the decay of uranium 235 and plutonium 239 is lead 207 (82Pb.sup.207). The plutonium 239 decay chain embodies 12 steps, the uranium 238 chain as 14 steps, and the uranium 235 has 11 steps. The decay chain mechanisms for these isotopes are shown in Appendix A. The two principle steps in the decay of the common radioactive isotopes of uranium 235, uranium 238 and plutonium 239 are emission of alpha particles and beta particles from the nucleus. Alpha particle emission occurs when an alpha particle escapes intact from the nucleus of an atom of the unstable material. An alpha particle is comprised of two protons and two neutrons. This particle is a particularly stable configuration in terms of nuclear binding forces. The emission of an alpha particle from a radioactive atom results in the lowering of the atomic number of the atom by two and a lowering of the mass number by four. Beta particle emission results from the spontaneous decay of a neutron to a proton which remains in the nucleus and an electron which is emitted therefrom and an anti-neutrino. The result of a beta emission from a nucleus is a unit increase in the atomic number of the atom with no change in the atomic mass. For example, one step in the decay of uranium 235 to lead involves the emission of a beta particle from thorium 231 (.sub.90 Th.sup.231) to yield protactinium 231 (.sub.91 Pa.sup.231). Typically, a given nucleus will decay by either alpha emission, or by beta emission, although some nuclei may decay by other methods, including gamma emission and spontaneous fission. The half-life of beta decay is ordinarily significantly shorter than that for typical alpha decay (see Appendix A). In the case of the three primary isotopes found in radioactive waste material and by-products, the primary limiting step in the decay is the initial alpha particle emission from the material. The half-lives for these initial decays are extremely long. The initial alpha emission for plutonium 239 has a measured half-life of 24,360 years. Uranium 235 has a half-life of 713 million years, while uranium 238 is the most stable of all, having a half-life or 4.5 billion years. The radioactive content of the waste and by-products of these materials thus remains high over a long period of time. It is highly desirable to eliminate the radioactivity of waste materials by decontaminating such materials as quickly as possible. Although most alpha decay steps and beta decay steps present no direct hazard, some of these released particles have sufficient energy to cause harm to living things such as animals, persons, and plants. Furthermore, the element plutonium is extremely poisonous. Although relatively harmless when outside of the body, if it is taken into the body by ingestion or through the respiratory track, even a small amount can cause almost immediate death. Plutonium is selectively delivered by the body to the bone marrow, where the alpha emissions can cause significant damage. It has been determined that a dose of 0.6 micrograms of plutonium taken internally is a lethal dose. Thus, plutonium contamination particularly creates a health hazard. Generally speaking, the scientific community believes that the decay rate of a radioactive nucleus is immutable. However, it is possible to change the decay rate by changing the environment of the emitter. This prior art shows that the decay rate of beta decay and of internal conversion can be changed slightly by varying the chemical composition of an emitter. The present invention is concerned primarily with alpha decay, not investigated by the work of Segre and Wiegand et al, a copy of which was previously made of record. Further the environment change is due to an electrostatic generator. It is not a change in the ambient environment. According to the accepted theory of beta decay, the decay rate is proportional to .rho.(o)=e.psi..psi.(o), the electron charge density at the nucleus. The decay rate may, therefore, be expected to vary with local changes in the electronic environment. It has been found, for instance, that pressure affects the decay rate. Experiments on beta and gamma decay demonstrate that any rearrangement of the electron charge distribution inside the atom may produce a measurable change in decay rate. In all cases investigated, the effect is extremely small. That is, the increase in decay rate is about 0.1%. The conventional theory of alpha decay is very well known. The decay is described as the tunneling of an alpha particle through the Coulomb potential barrier of the daughter nucleus. The decay constant is determined by the energy of the alpha particle and by the height and width of the barrier. The theory leads to a relationship between decay rate and the change of the daughter nucleus which fits the data extremely well. The atomic electrons in an alpha emitter also influence the decay rate. In Th.sup.230, for example, these electrons generate a constant potential which extends to the nuclear surface, decreasing the height and width of the Coulomb barrier. Although the corresponding potential energy is relatively small, it has a non-trivial effect on the decay constant. In fact, if all of the atomic electrons were stripped off the thorium atom, the half life would be increased from 80,000 to 146,000 years. Because of the drawbacks of conventional techniques for reducing the hazards of radioactive waste materials, a need exists to accelerate the decontamination of such materials. The present invention satisfies this need. SUMMARY OF THE INVENTION The present invention is directed to apparatus and a method for decontaminating radioactive materials. The stimulus is kept applied to the radioactive materials for a predetermined time. In this way, the rate of decay of the radioactivity of the materials is greatly accelerated and the materials are thereby decontaminated at a rate much faster than normal. The stimulus can be applied to the radioactive materials by placing such materials within the sphere or terminal of a Van de Graaff generator where they are subjected to the electrical potential of the generator, such as in the range of 50 kilovolts to 500 kilovolts, for at least a period of 30 minutes or more. The present invention is based upon the fact that the decay rate of radioactive materials can be accelerated or enhanced and thereby be controlled by a stimulus, such as an applied electrostatic potential. This potential, for instance, is incorporated into the quantum mechanical tunneling equation for the transmission coefficient TT by including an additional potential energy EQU V.sub.a 2e.phi.. (1) where 2e is the charge of the alpha particle. Hence EQU T*T=exp (-G) (2) where ##EQU1## With V.sub.a =0, this expression is well known. Clearly V.sub.a modifies the height and width of the Coulomb barrier. The turning point EQU b=2Z.sub.1 e.sup.2 /(E-V.sub.a) (4) is greater or less than b.sub.o =2Z.sub.1 e.sup.2 /E for V.sub.a positive or negative. Assuming that b is large compared to the nuclear radius, it follows that EQU ln.lambda./.lambda..sub.o =3.71Z.sub.1 (E.sup.-1/2 -(E-V.sub.a).sup.-1/2).(5) where 3.71 is a fit parameter used by Taagepera and Nurmia. It is clear that V.sub.a controls .lambda.. For negative (positive )applied voltages the enhancement EQU .epsilon.=.DELTA..epsilon./.epsilon..sub.o ( 6) will be positive (negative. An approximate form for equation (5) is useful when .vertline.V.sub.a .vertline.<<E. EQU ln.lambda./.lambda..sub.o =-3.71Z.sub.1 e.phi./E.sup.3/2 ( 7) In Th.sup.230 measurements, .vertline.V.sub.a .vertline..ltoreq.90KeV.about.2E.times.10.sup.-2. For this isotope, theory predicts a linear relationship between e.phi. and ln.lambda./.lambda..sub.o with a slope of -31.13/MeV. The primary object of the present invention is to provide an improved apparatus and method for decontaminating radioactive waste materials by providing a stimulus to the materials so that the alpha, beta and gamma particles associated with the materials will decay at an accelerated rate. Other objects of this invention will become apparent as the following specification progresses, reference being had to the accompanying drawings for an illustration of an apparatus for carrying out the teachings of the invention.
047956062	summary	BACKGROUND OF THE INVENTION This invention relates to inspection systems, particularly for nuclear reactor installations. FEATURES AND ASPECTS OF THE INVENTION According to this invention, there is provided apparatus for inspecting the surface of a structure comprising a track extending around an upper region of the structure, an elongated flexible carrier engageable along its length with the track and movable lengthwise along the track, means for leading the flexible carrier insertably into engagement with the track, and retractably out of engagement with the track, at at least one position along the length of the track, and inspection means carried by the carrier for selective downward extension and upward retraction relative to the carrier and relative to the track. The structure may for example be a tube or vessel. The vessel may be closed or open topped. Also in accordance with the invention, the aforesaid apparatus is provided in combination as part of a nuclear reactor installation including a primary vessel surrounded externally by a guard vessel and defining an annular space therebetween, the track extending around the top of the primary and guard vessels, and the inspection means being extendable into and retractable from the annular space. The flexible carrier may comprise a series of tubular members, adjacent members being connected for relative movement. The adjacent members may for example be connected by flexible bellows. The inspection means may comprise a camera carried at an end of a cable extending through the flexible device. The track may comprise spaced elements defining a slot, said flexible carrier having guide means engaging the spaced elements. The guide means may comprise rotatable means. The inspection means may extend between the spaced elements when being moved up and down.
051026155	abstract	A container for storing and transporting radioactive material is provided comprising: a vessel, having an upwardly open cavity for accommodating radioactive material; and a cap covering the top surface of the vessel to seal the cavity. The vessel and cap walls have a core of radioactive shielding material such as cementatious, concrete enveloped and isolated within a continuous metal lining. The metal lining allows the container to be held under water, improves the impact resistance of the container and forms a barrier in a geological disposal facility. The lower edge of the cap and upper edge of the vessel are welded together to seal the cavity. The vessel includes lifting lugs for lifting the vessel and container.
	abstract	An apparatus and method for inter-unit transfer of spent nuclear fuel. In one aspect, the invention is a method of transferring high level radioactive waste comprising: a) loading high level radioactive waste into a water-filled cavity of a canister body having an open top end at a first location; b) coupling a lid to the canister body to enclose the open top end; c) removing a volume of water from the cavity so that a water level of the water within the cavity is above a top end of the high level radioactive waste and a space exists between the water level and a bottom surface of the lid; d) hermetically sealing the cavity; and e) transferring the canister to a second location, the water level remaining above the top end of the high level radioactive waste during the transfer.
	abstract	A method and apparatus for constructing a 3-dimensional image of the internal organs invisible by the conventional method is provided. The apparatus comprises: generating means for generating a monochromatic and parallel X-ray beam from an X-ray beam; a reflection-type angle analyzer for reflecting the monochromatic and parallel X-ray beam at reflecting points on both slopes of a reflection curve of the reflection-type analyzer, angle information being extracted to a maximum extent at the reflecting points, the monochromatic and parallel X-ray beam including an X-ray beam which passed through the object when the object is positioned on a rotatable goniometer in the monochromatic and parallel X-ray beam and an X-ray beam from the generating means when the object is not positioned in the monochromatic and parallel X-ray beam; an imaging device for generating a refraction angle data by receiving the monochromic and parallel X-ray beam reflected on the reflection-type angle analyzer to detect the intensity thereof, and output a refraction angle data; and
	summary
	description	Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block configuration diagram of an X-ray CT system in one embodiment. As shown, the system is comprised of a gantry apparatus for irradiating a subject with X-rays and detecting X-rays having passed through the subject, and an operating console 200 for performing several kinds of operating settings for the gantry apparatus 100, and reconstructing an X-ray tomographic image based on data output from the gantry apparatus 100 for display. The gantry apparatus 100 comprises a main controller 1 for controlling the entire apparatus 100, and the following components. Reference numeral 2 designates an interface for communicating with the operating console 200, and 3 designates a planar annular gantry having a cavity portion for carrying a subject (human subject) laid on a table 14 (in a direction perpendicular to the drawing""s plane, which will be referred to as a Z-axis or a body axis hereinbelow). Reference numeral 4 designates an X-ray tube which is an X-ray generating source, and the X-ray tube 4 is driven and controlled by an X-ray tube controller 5. Reference numeral 6 designates a filter unit, which characterizes the present invention, and the filter unit 6 supports at least two types of filters which can be switched as desired in this embodiment. The particulars of the structure of the filter unit 6 and the filters supported thereon will be described in detail later. Reference numeral 7 designates a motor for switching between the filters of the filter unit 6, and 8 designates a filter controller for driving and controlling the motor 7. Reference numeral 9 designates a filter (made of a material such as Teflon) in a shape having a thin central portion and thick end portions in order to reduce the X-ray attenuation at the central portion and enhance the X-ray attenuation at the end portions, which is generally known and referred to as a bow-tie filter. Reference numeral 10 designates a collimator having a slit for defining a range of X-ray irradiation. Reference numeral 12 designates a rotary motor for rotating the gantry 3, and 13 designates a motor controller for driving the rotary motor 12. Reference numeral 14 designates a table for resting the subject, 15 a table motor for carrying the table 14 in the Z-axis direction, and 16 a table motor controller for driving and controlling the table motor 15. Reference numeral 17 designates an X-ray detecting section for detecting X-rays having passed through the subject, comprised of a detecting array in which about 1,000 X-ray detecting elements are arranged in a row. Some X-ray CT systems have a plurality of such detecting arrays. Such systems are called multi-slice X-ray CT systems. For brevity of description, the present invention will be described with reference to a single-slice X-ray CT system having only one detecting array, but it will be easily recognized that the present invention also applies to multi-slice X-ray CT systems. Reference numeral 18 designates a data collecting section for collecting data obtained by the X-ray detecting section 17 and converting the data into digital data. The operating console 200 is constituted by a xe2x80x9cworkstation,xe2x80x9d which comprises a CPU 51 for controlling the entire apparatus, a ROM 52 storing a boot program and BIOS, and a RAM 53 that serves as a main storage device, as shown, and the following components. An HDD 54 is a hard disk device, which stores an OS, and a diagnosis program for supplying several kinds of instructions to the gantry apparatus 100 and reconstructing an X-ray tomographic image based on data received from the gantry apparatus 100. In addition, it stores correction data 54a-54c as shown (which will be described in detail later). A VRAM 55 is a memory for developing image data to be displayed, and the image data can be displayed on a CRT 56 by developing the image data and the like there. Reference numerals 57 and 58 designate a keyboard and a mouse, respectively, for performing several kinds of settings. Reference numeral 59 designates an interface for communicating with the gantry apparatus 100. In performing a scan, and in the aforementioned configuration, an operator (technician or physician) operates the operating console to specify a region to be scanned in the subject, and thereafter prescribes a scan schedule in detail. Then, the operator gives a scan start instruction. A program running on the operating console in turn issues several control commands to the gantry apparatus 100 (main controller 1) according to the prescribed scan schedule. The main controller 1 on the gantry apparatus 100 supplies control signals to the X-ray tube controller 5, filter controller 8, collimator controller 11, motor controller 13 and table motor controller 16 according to the control instruction commands. Consequently, X-rays generated at the X-ray tube 4 and having passed through the subject can be detected by the X-ray detecting section 17, and the digital data of the X-rays can be obtained from the data collecting section 18. The main controller 1 transfers the data to the operating console 200 via the interface 2. Since the gantry 3 is rotated by the rotary motor 12 and the table 14 is also carried along the Z-axis, digital data of transmitted X-rays at different rotation angles and different Z-axis positions are sequentially transferred to the operating console 200. One scanning technique which involves stopping the table 14 and fixing the table 14 at a certain Z-axis position, rotating the gantry 3 one time in this condition, and then carrying the table 14 to a next scan position and rotating the gantry 3 again, is called an axial scan; and another scanning technique which involves simultaneously rotating the gantry 3 and carrying the table 14 is called a helical scan. Either of the scanning techniques may be employed. The program running on the operating console 200 then performs processing to reconstruct an X-ray tomographic image by a known processing method based on the received data, and sequentially displays the results on the CRT 56. less than less than Description of the Filter Unit greater than greater than X-rays generated from the X-ray tube 4 have a continuous spectral distribution, rather than a specific wavelength of X-rays (line spectrum). The lower-energy (longer-wavelength) X-rays in those X-rays tend to be absorbed by the subject, while the higher-energy (shorter-wavelength) X-rays tend to be transmitted. That is, when X-rays having a continuous spectrum are applied to the subject, there is a tendency for only the high-energy X-rays to be transmitted through the subject. This phenomenon is generally referred to as the beam-hardening effect of X-rays. Since the X-rays transmitted through the subject are high-energy X-rays, it is desired that no low-energy X-rays be applied to the subject from the beginning. Therefore, it has been made mandatory to provide a filter having a thickness of at least 2.5 mm in aluminum equivalent between the X-ray tube and the subject, rather than directly applying the X-rays generated from the X-ray tube 4. By passing the X-rays through a filter having such a property, lower-energy X-rays can be attenuated by the filter, thereby preventing the subject from being exposed to unnecessary radiation. However, there is room for further improvement on this technique in which a scan is performed using only one filter having a thickness of 2.5 mm in aluminum equivalent. The reason of this is as follows. As described earlier when X-rays having a continuous spectrum are applied to the subject, lower-energy X-rays are absorbed by the subject in a larger proportion. Since the abdomen of the subject is the region having the largest cross section, X-rays that reach the X-ray detecting section 17 mostly have a high energy in scanning such a region. Thus, when a scan is performed on the abdomen, the beam-hardening effect is most prominent. Therefore, a filter having a thickness of more than 2.5 mm in aluminum equivalent may safely be used in scanning the abdomen. On the other hand, the head of the subject has a smaller cross section than the abdomen, resulting in a smaller beam-hardening effect. Moreover, since the brain is largely composed of white matter and gray matter and, in addition, the difference in CT value between them is small, it is difficult to reconstruct an X-ray tomographic image having a sufficient contrast. To enhance the contrast of an X-ray tomographic image, it is necessary to make more X-rays reach the X-ray detecting section 17, and to increase the S/N ratio. Therefore, in scanning the head of the subject, it is desired that a thinner filter (but not less than 2.5 mm in aluminum equivalent) than that used in scanning the abdomen be used. In scanning the thorax, since the lungs are hollow and the contrast that depends upon the existence of the subject""s tissue is high from the start, an X-ray tomographic image can be reconstructed with a sufficiently high quality using only high-energy X-rays. Therefore, for a filter employed in scanning the thorax, a thicker filter (a filter having a higher attenuation factor) than for the abdomen can be used, thereby cutting low-energy X-rays applied to the subject to prevent unnecessary radiation exposure. In summary, when the thicknesses of filters used in scanning the head. abdomen and thorax are represented as Ta, Tb and Tc, in aluminum equivalent, the following relationship holds: 2.5 mmxe2x89xa6Ta less than Tb less than Tc. Consequently, a scan for obtaining signals having a sufficient S/N ratio can be performed according to the scan region, and yet the exposure to the subject can be decreased to the minimum required amount. The filter thicknesses for particular regions are desirably as follows: the filter thickness Ta for the head: 2.5-3.5 mm in aluminum equivalent, the filter thickness Tb for the abdomen: 6.0-8.0 mm in aluminum equivalent, and the filter thickness Tc for the thorax: 10.0-12.0 mm in aluminum equivalent. Although aluminum is taken as a standard here, if copper is to be used, the thickness may be 0.2 mm for the abdomen and 0.25 mm for the thorax, for example. FIG. 2 illustrates an X-ray transmission spectrum distribution in using these filters. It will be recognized that the spectrum of transmitted X-rays is shifted toward higher energy with the increasing filter thickness, although the amount of transmitted X-rays tends to decrease. FIG. 3 is a perspective view of the configuration around the filter unit 6 in the present embodiment. As shown, the filter unit 6 supports three filters 6a, 6b and 6c (having respective thicknesses of Ta, Tb and Tc) provided slidably in the subject-carrying direction (Z-axis). The filter unit 6 is provided on its side with teeth 30, with which a gear 31 secured to a driving spindle of the motor 7 engages, as shown. The gear 31 is rotated by driving the motor 7, so that the position of the filter unit 6 can be changed freely along arrow A (Z-axis) in the drawing. Reference numeral 32 designates a sensor comprising a light-emitting element 33 and a light-receiving element 34 at the illustrated positions. When the gantry apparatus 100 is activated, the main controller 1 supplies a drive control signal for the motor 7 to the filter unit controller 8 to move the filter unit 6, and determines a home position of the filter unit 6 as the point where the light-receiving element 34 changes from a state incapable of detecting a light from the light-emitting element 33 into a state capable of detecting the light (or vice versa). By counting the number of pulses supplied to the motor 7 starting with the home position, the position of the filter unit 6 is identified. Thus, a desired one of the filters 6a-6c can be positioned just below the X-ray tube 4. After the initialization processing for the activation as described above, the main controller 1 selects the most suitable filter by issuing a control command to the filter controller 8 according to an instruction command from the operating console 200. For example, when a selection command that means the filter 6c is to be employed is received from the operating console 200, a shift amount with respect to the current position is calculated, and a control signal corresponding to the amount is supplied to the motor controller 8 to enable a scan employing the filter 6c. less than less than Control of a Scan greater than greater than FIG. 4 illustrates a start menu for scan scheduling displayed on the CRT 56 of the operating console 200. As shown, a model image is displayed on the left of the screen, and logical buttons 40-42 are displayed on the right for determining the region to be scanned. The selection of one of the buttons is achieved by moving a cursor 43 linked to the mouse 58 to a desired button and clicking a button on the mouse 58. Upon clicking any one of the buttons 42-44, the CPU 51 outputs a filter selection command corresponding to the selected region to the gantry apparatus 100 via the interface 59. Thereafter, the main controller 1 in the gantry apparatus 100 interprets the received command, and issues a control command to the filter controller 8 based on the received command, as described earlier. Then, a detailed scan schedule for the selected region will be specified on the operating console 200. However, since this process has no direct relation with the present invention and is a known procedure, a detailed description will be omitted. Since the filters 6a-6c have different transmission properties (or attenuation properties), as shown in FIG. 2, the electric signal output from the X-ray detecting section 17 is naturally one affected by filter employed. Specifically, even if the same region of the subject is scanned, the signal obtained employing the filter 6a is different from the signal obtained employing the filter 6b. Therefore, the operating console 200 is required to perform reconstruction processing for an X-ray tomographic image suited to the filter employed during the scan by the gantry apparatus 100. Therefore, respective correction data corresponding to the filters 6a-6c to be employed are stored in the HDD 54 of the operating console 200. When the region to be measured has been determined, the appropriate correction data selected from among the correction data 54a-54c is used to correct data transferred from the gantry apparatus 100, and thereafter, the reconstruction processing for an X-ray tomographic image is performed. It should be noted that the correction data 54a-54c also take the properties of the bow-tie filter 9 into account. In summary, the CPU 51 of the operating console 200 is operated according to the flow chart shown in FIG. 5. This program is previously stored in the HDD 54, and is loaded into the RAM 53 for execution. First, at Step S1, the scan region selection screen is displayed as shown in FIG. 4, and the operator (technician or physician) is prompted to select which region is to be scanned. After the selection, a decision is made on which region was selected at Step S2. If the head was selected as the scanned object, the process goes to Step S3 and an instruction command for the filter 6a selection is issued to the gantry apparatus 100 to employ the filter 6a. Then, the gantry apparatus 100 controls the movement of the filter unit 6 as described earlier, positions the specified filter just below the X-ray tube 4 and fixes the filter at that position. Then, the process goes to Step S4 to select the correction data 54a for the filter 6a and reads the data 54a out to a predefined region in the RAM 53. If the thorax was selected as the scanned object, an instruction command for the filter 6c selection is issued at Step S5, the correction data 54c for the filter 6c is selected at Step S6, and the data 54c is read out to a predefined region in the RAM 53. If the abdomen was selected as the scanned object, an instruction command for the filter 6b selection is issued at Step S7, the correction data 54b for the filter 6b is selected at Step S8, and the data 54b is read out to a predefined region in the RAM 53. In any case, the process goes to Step S9, and a detailed scan schedule is prescribed for the selected scan region. The prescription includes, for example, items about the range of the carrying direction to be scanned (from which position to which position), about which interval is to be selected for reconstructed X-ray tomographic images, and the like. These items are known and a description thereof will be omitted. Then, at Step S10, when the operator orders a scan to be started, processing are carried out to transfer several kinds of control commands to the gantry apparatus 100 according to the scan schedule, and to cause the gantry apparatus 100 to control the driving operations of the motor controller 13, table motor controller 16 and X-ray tube controller 5 according to the supplied commands, and to transfer X-ray transmission data collected by the data collecting section 18 (data from all the channels in the X-ray detecting section 17) to the operating console. The operating console 200 receives the data transferred from the gantry apparatus 100 at Step S11. The process then goes to Step S12, and the correction data previously read out to the RAM 53 is used to perform correction processing on the received data. Then, at Step S13, known processing for reconstruction of an X-ray tomographic image is executed, and processing for outputting the image (display processing etc.) is executed at Step S14. According to the present embodiment as described above, by employing the most suitable filter corresponding to the region to be measured in a subject, the subject is only exposed to the minimum required radiation and the quality of the reconstructed X-ray tomographic image can be improved. less than less than Second Embodiment greater than greater than Although the filter to be employed is determined according to the region to be measured in the former embodiment, the size of subjects widely varies. Especially, the cross-sectional area of the abdomen is different among individuals. For example, a scan of the abdomen of a large person exhibits a more prominent hardening effect than that of a thin person. The same is true for an adult and a child. Therefore, in this second embodiment, the parameters for determining the filter to be employed additionally include the size of the subject, as well as the region to be measured. It should be noted that the number of types of filters should be increased as compared with the first embodiment because the size of the subject is additionally considered. FIG. 6 shows a measured region selection screen in accordance with the second embodiment. As shown, fields 60 and 61 are provided for inputting the height and weight as the size of a subject. If the size of a subject is assumed to be classified into, for example, three grades: large, medium and small, since the number of the measured region is also three, nine filters at maximum may be needed. Assume that the filters are represented as f1, f2, . . . , f9. The operator first inputs the height and weight of a subject to be scanned, and then performs the operation to select the region to be measured. Consequently, an appropriate filter is determined from among the filters f1, f2, . . . , f9, and an instruction command for the filter selection is sent to the gantry apparatus 100. It will be easily recognized that the HDD 54 on the operating console 200 is provided with the same number of correction data sets as the number of filters. In determining the filter to be employed, a table as exemplarily shown in FIG. 7 may be stored in the HDD 54 to select the filter with reference thereto. As a result, since the filter to be employed can be determined additionally considering the size of the subject, the exposed dose to the subject is further reduced, and an X-ray tomographic image can be reconstructed with high accuracy. It should be noted that although only one example is described of the switching structure of the filter unit of the gantry apparatus 100 for the first and second embodiments, other structures may be contemplated. The point is that it should be possible to perform a scan employing a desired filter from among filters having different transmission properties. Moreover, although the regions to be scanned have been described as three regions: the head, thorax and abdomen in the above embodiments, the minimum requirement is two regions: the head and abdomen. Moreover, the regions to be measured may include four regions or more for fine definition. Moreover, although the filter in the embodiments is described as being made of aluminum, there is no limitation on the material. The point is that filters having transmission properties like those shown in FIG. 2 should be used, and other materials such as copper or the like may be employed. Furthermore, the present invention is not limited to the apparatuses and methods for implementing the aforementioned embodiments, but the scope of the present invention includes the case in which the aforementioned embodiments are achieved by a software program code supplied to a computer (CPU or MPU) in the aforementioned system or apparatus, and the computer of the system or apparatus operates the several devices according to the program code. In this case, the software program code per se is regarded as achieving the functions of the embodiments. Therefore, the program code per se, and means, particularly, a storage medium storing the program code, for supplying the program code to the computer are contained within the scope of the present invention. For the storage medium for storing such a program code, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, non-volatile memory card, ROM or the like may be employed, for example. Furthermore, the program code may be downloaded via a medium that is a network (e.g., the Internet). Many widely different embodiments of the invention may be configured without departing from the spirit and the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.
051529572	abstract	A foreign matter recovering apparatus includes 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 relative to the body, a recovering working unit adapted to be moved by the moving mechanism section to gain access to clearance of the fuel assembly to allow foreign matter to be recovered thereby, and a remote control section for remotely controlling the working unit on the basis of an image representing a working state of the working unit to operate it properly.
	claims	1. A proton beam modulator comprising:a first modulating portion comprising a first material portion and a second material portion, the first and second materials provided having characteristics such that in response to a proton beam incident thereon, at least portions of the proton beam pass therethrough; anda second modulating portion comprising a third material portion and a fourth material portion provided having characteristics such that in response to the proton beam incident thereon, at least portions of the proton beam pass therethrough;wherein the first and second modulating portions are symmetrically disposed about an axis of rotation of the proton beam modulator,wherein the combination of the first, second, third, and fourth material portions modulate an energy level of the proton beam and a scattering of the proton beam, wherein the scattering remains substantially constant as the modulator rotates. 2. The proton beam modulator of claim 1 wherein the first modulating portion and the second modulating portion are positioned to create an open channel through the modulator so that, when the channel is parallel to the proton beam, the proton beam can pass through the open channel without passing through the first and second modulating portion. 3. The proton beam modulator of claim 1 wherein the first modulating portion has a wedge shape. 4. The proton beam modulator of claim 3 wherein the first material portion and the second material portion are arranged radially from the axis of rotation so that the second material portion is inside the first material portion. 5. The proton beam modulator of claim 3 wherein a thickness of the wedge shape decreases along an angular coordinate of the wedge shape. 6. The proton beam modulator of claim 5 wherein a thickness of the first material portion decreases along the angular coordinate of the wedge shape and a thickness of the second material portion increases along the angular coordinate of the wedge shape. 7. The proton beam modulator of claim 1 wherein the combination of the first, second, third, and fourth material portions modulate the energy level of the proton beam such that the energy level of the proton beam changes as the modulator rotates. 8. The proton beam modulator of claim 1 wherein the first and second modulating portions produce an energy modulation in the range of about 12 cm WET to about 32 cm WET. 9. The proton beam modulator of claim 1 wherein the first and third material portions comprise stainless-steel. 10. The proton beam modulator of claim 1 wherein the second and fourth material portions comprise lead. 11. The proton beam modulator of claim 1 wherein:the first and third material portions comprise a first type of material;the second and fourth material portions comprise a second type of material; andthe second material portion is positioned between the first material portion and an axis of rotation of the proton beam modulator, and the fourth material portion is positioned between the third material portion and the axis of rotation of the proton beam modulator. 12. The proton beam modulator of claim 1 further comprising a rotating wheel whereupon the first and second modulating portions are positioned opposite each other. 13. The proton beam modulator of claim 12 wherein the rotating wheel is positioned so that the proton beam passes through a center of rotation of the rotating wheel. 14. The proton beam modulator of claim 12 wherein the rotating wheel is positioned so that an axis of rotation of the rotating wheel is perpendicular to the proton beam. 15. The proton beam modulator of claim 12 further comprising a circular plate positioned so that the first modulating portion and the second modulating portion are sandwiched between the rotating wheel and the circular plate. 16. The proton beam modulator of claim 15 wherein the first and second modulating portions are removable from the rotating wheel and the circular plate. 17. The proton beam modulator of claim 12 wherein the rotating wheel has a diameter of 10 cm or less. 18. A proton beam imaging system comprising:a proton beam generator to generate a proton beam;a proton beam modulator through which the proton beam passes positioned between the proton beam generator and an image target; anda proton beam detector positioned to detect the proton beam exiting the image target;wherein the proton beam modulator comprises:a rotating wheel having an axis of rotation positioned so that the proton beam passes through the axis of rotation and the axis of rotation is perpendicular to the proton beam;a first modulating portion comprising a first material portion and a second material portion through which a proton beam passes; anda second modulating portion comprising a third material portion and a fourth material portion through with the proton beam passes;wherein the first and second modulation portions are positioned opposite each other on the rotating wheel,wherein the first, second, third, and fourth material portions comprise a wedge shape having a varying thickness to modulate an energy level of the proton beam as the proton beam modulator rotates, wherein the proton beam is modulated to have a substantially constant degree of scattering as the proton beam modulator rotates. 19. The proton beam imaging system of claim 18 wherein the first and third material portions comprise stainless-steel, and the second and fourth material portions comprise lead. 20. The proton beam imaging system of claim 18 further comprising a gantry portion, wherein the proton beam modulator is situated within the gantry portion. 21. A proton beam modulator comprising:a plurality of wedge-shaped modulating portions, each of the plurality of wedge-shaped modulating portions comprising a first material portion and a second material portion disposed on a surface of the wedge-shaped modulating portions such that in response to a proton beam incident thereon, at least portions of the proton beam are capable of passing therethrough and wherein the plurality of wedge-shaped modulating portions are disposed in spatial relation such that the plurality of wedge-shaped modulating portions define an axis of rotation positioned such that an axis along which a proton beam is aligned perpendicular to the axis of rotation defined by the plurality of wedge-shaped modulating portions,wherein the first material portion and the second material portion are arranged radially from the axis of rotation so that the second material portion is inside the first material portion. 22. The proton beam modulator of claim 21 wherein the plurality of wedge-shaped modulating portions are provided as a pair of modulating portions positioned opposite each other to define an axis of rotation positioned such that an axis along which a proton beam is aligned is perpendicular to the axis of rotation defined by the pair of wedge-shaped modulating portions.
	description	This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-214642, filed Jul. 22, 2004, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates to a crystallization apparatus which irradiates laser light to a thin film such as a semiconductor film and to a crystallization method, particularly to a laser crystallization apparatus comprising means for correcting positional shift of a semiconductor film with respect to an imaging position of laser light, and a laser crystallization method. 2. Description of the Related Art A laser crystallization technique for melting and crystallizing a non-single crystal semiconductor thin film using, for example, short pulse laser light having large energy is used to crystallize a semiconductor thin film used for manufacturing a thin film transistor for a liquid crystal display device, an organic electro luminescence display device or the like. Among such laser crystallization technologies, attention is focused on a Phase Modulated Excimer Laser Annealing (PMELA) which uses an irradiation of a phase-modulated excimer laser light for crystallization. In the PMELA technique, excimer laser light having predetermined light intensity distribution whose phase has been modulated by a phase modulating element, for example, a phase shifter, is used. The excimer laser light is irradiated, for example, to a non-single crystal semiconductor thin film, for example, an amorphous silicon or polycrystal silicon thin film, formed on a glass substrate. The semiconductor film is molten at the irradiated portion then crystallized. In the presently developed PMELA technique, a region having a size of approximately several millimeter square is molten and crystallized by one irradiation, and a crystallized silicon thin film having comparatively uniform crystal grains of about several micrometers to 10 μm in size and having a superior quality has been formed (see, e.g., Kohki Inoue, Mitsuru Nakata, Masakiyo Matsumura, “Amplitude and Phase Modulated Excimer-Laser Melt-Regrowth Method of Silicon Thin-Films—A New Growth Method of 2-D Position-Controlled Large-Grains—”, Journal of the Society of Electron Information Communication, Vol. J85-C, No. 8, pp. 624 to 629, 2002). In the PMELA technique, in order to obtain a crystallized semiconductor film having a stabilized quality, it is one of important technical problems to constantly align a position of the non-single crystal semiconductor thin film being crystallized to an imaging position of the excimer laser light in every laser light irradiation for crystallization. Since a substrate to be crystallized has a large area, for example, 550 mm×650 mm, the substrate has its own warp, thickness variation, deflection in installing to the PMELA apparatus and the like. Therefore, substantial flatness of the substrate is generally worse than a focal depth of a laser optical system, for example, ±5 μm to 10 μm. To solve the problem, some conventional laser crystallization apparatus comprises a fixed substrate height measurement sensor. Examples of typical fixed substrate height measurement sensor include an optical system, electrostatic capacitance system, or gas pressure system. Substrate height correction using such fixed sensor is suitable for correcting a shift caused by the above-described flatness of the substrate. However, in the laser crystallization apparatus, as described later in detail, since crystallization laser light having high energy is used, lens temperature of an excimer imaging optical system rises during use, and it causes a shift in the imaging position of the excimer imaging optical system. In a correction method using the conventional fixed substrate height measurement sensor, the shift of the imaging position caused by the laser crystallization apparatus itself due to the temperature change in the excimer imaging optical system cannot be corrected in principle. As described above, in the laser crystallization apparatus, the imaging position of the crystallization laser light is preferably constantly aligned to the non-single crystal semiconductor thin film to be molten and crystallized in order to improve and stabilize the quality of the crystallized semiconductor film. If a shift is generated between the imaging position of the crystallization laser light and the position (height) of the non-single crystal semiconductor thin film disposed on the substrate, then desired crystallization is not performed in a crystallization step after melting the semiconductor thin film. Especially in the PMELA apparatus, the crystallization laser light to be irradiated to the non-single crystal semiconductor thin film is modulated by an optical system in such a manner as to have a predetermined light intensity distribution on the non-single crystal semiconductor thin film being crystallized. However, if the shift is caused between the imaging position of the laser light and the position of the non-single crystal semiconductor thin film, then a predetermined light intensity distribution cannot be obtained on the non-single crystal semiconductor thin film. Therefore, a micro temperature distribution in the laser light irradiation region changes from a predetermined distribution. As a result, a desired melting or crystallization of semiconductor film is not performed. Specifically, a size of crystal grain grown is reduced. Additionally, the sizes of the crystal grains become nonuniform, thus the quality of the crystallized silicon film is degraded. As the excimer laser light used in the PMELA apparatus, for example, krypton fluoride (KrF) or xenon chloride (XeCl) is preferred, and they have wavelengths of 248 nm and 308 nm, respectively. In the PMELA apparatus, the excimer laser light having a predetermined light intensity distribution formed by an optical phase modulating element such as a phase shifter is irradiated onto the non-single crystal semiconductor thin film. The excimer laser light should be imaged on the non-single crystal semiconductor thin film with a high resolution of about several μm. As to the excimer laser light, the PMELA apparatus uses the laser light at a high light intensity, at high duty, and in a large area for production efficiency. The light preferably has a high intensity of about 1 J/cm2 on the semiconductor thin film to be crystallized. This is much larger than an intensity of an excimer laser light used in an aligner for semiconductor integrated circuit production. In order to obtain the high light intensity, in the PMELA apparatus, the excimer laser light is used with a wide spectral bandwidth (0.5 nm) without narrowing the bandwidth, unlike in an aligner used for large-scale integrated circuit production. Moreover, there are limited lens materials capable of dealing with the excimer laser light which is ultraviolet light used in the PMELA apparatus, thus fused silica or synthetic quartz (referred as fused silica hereinafter) for ultraviolet or calcium fluoride (CaF2) is preferable from absorption characteristic and the like of the light. As described above, in the PMELA apparatus using the phase shifter, chromatic aberration correction of a lens is important since the excimer laser light having a large spectrum width is imaged in a high resolution on the non-single crystal semiconductor thin film. However, a constitution of an optical system including a laminated lens like a microscope lens for visible light is not applicable from the respect of heat resistance. Therefore, since the chromatic aberration has to be corrected with the above-described limited lens material, the number of the lenses increases. If the excimer laser light having the high intensity is used in such lens system, although the excimer laser light is absorbed a little in each lens constituting the optical system, then total laser light absorption in the optical system is large. As a result, a so-called thermal lens effect is caused, for example, lens temperature rises, or the lens is strained. That is, a problem occurs that the imaging position shifts by the thermal lens effect. In one PMELA apparatus, the imaging position shifts, for example, by 10 μm, when the lens temperature changes by 1° C. in the excimer laser imaging optical system. Considering that the focal depth of the imaging optical system of the PMELA apparatus is about ±10 μm, the shift of the imaging position caused by the temperature change is not negligible. The imaging position shift causes a variation in the quality of the crystallized semiconductor film such as a substrate for a liquid crystal display device having a large area, if the pulse laser light is repeatedly irradiated. As a result, there occur problems such as variation in image switching characteristic of the element formed therein, or a strained image. In the conventional fixed substrate height correction system, a height shift of the substrate to be crystallized due to the flatness of the substrate itself can be corrected, as described above. However, correction for, for example, the shift of the imaging position caused by above-described thermal lens effect in optical system for excimer laser crystallization has not been considered. Therefore, there is a need for a laser crystallization apparatus and a laser crystallization method in which a quality of a crystallized semiconductor thin film is prevented from being degraded and in which sizes of crystal grains are uniformed. The above-described problems can be solved by a laser crystallization apparatus and a laser crystallization method set forth below. According to an aspect of the invention, a laser crystallization apparatus comprises an crystallization optical system which irradiates laser light to a thin film disposed on a substrate to be crystallized to melt and crystallize an irradiated region of the thin film, the apparatus comprises: a measurement light source which is disposed outside a light path of the laser light, and which emits measurement light being illuminated the irradiated region of the thin film; and a substrate height correction system which illuminates the thin film with the measurement light through an imaging optical system in the crystallization optical system, and which detects the reflected measurement light from the thin film. According to another aspect of the invention, a laser crystallization apparatus comprises an crystallization optical system which irradiates laser light provided with a light intensity distribution by a phase modulating element to a thin film disposed on a substrate to be crystallized to melt and crystallize an irradiated region of the thin film, the apparatus comprises: a measurement light source which is disposed outside a light path of the laser light, and which emits measurement light being illuminated the irradiated region of the thin film; and a substrate height correction system which illuminates the thin film with the measurement light through an imaging optical system of the crystallization optical system, and which detects the reflected measurement light from the thin film. According to still another aspect of the invention, a laser crystallization method comprises: emitting laser light from a laser light source; irradiating the laser light to a thin film disposed on a substrate to be crystallized through an imaging optical system disposed in a light path of the laser light, and melting and crystallizing the thin film; emitting measurement light from a light source disposed outside the light path of the laser light; illuminating the thin film with the measurement light along the light path of the laser light through the imaging optical system; and detecting the reflected measurement light from the thin film through the imaging optical system. According to still another aspect of the invention, a laser crystallization method comprises: emitting laser light from a laser light source; modulating the laser light into laser light having a predetermined light intensity distribution by a phase modulating element; irradiating the modulated laser light to a thin film disposed on a substrate to be crystallized through an imaging optical system disposed in a light path of the laser light, and melting and crystallizing the thin film; emitting measurement light from a light source disposed outside the light path of the laser light; illuminating the thin film with the measurement light along the light path of the laser light through the imaging optical system; and detecting the reflected measurement light from the thin film through the imaging optical system. Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. The embodiments of the present invention will be described with reference to the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain principles of the invention. Throughout the drawings, corresponding portions are denoted by corresponding reference numerals. The embodiments are only examples, and various changes and modifications can be made without departing from the scope and spirit. Embodiments of a laser crystallization apparatus of a semiconductor film comprising a substrate height correction system according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a laser crystallization apparatus 1 according to a first embodiment of the present invention. The apparatus is a laser crystallization apparatus 1 comprising a crystallization optical system 2 projecting an image of a phase modulating element 24 in a reduced size, and a substrate height correction system 3. The apparatus has a function for correcting a shift in a height direction of a substrate 27 to be crystallized based on measurement of the substrate height correction system 3. The crystallization optical system 2 comprises an excimer illumination optical system 20 and an excimer imaging optical system 26. The excimer illumination optical system 20 emits and conditions crystallization laser light which illuminates the phase modulating element 24, for example, a phase shifter. The excimer imaging optical system 26 irradiates crystallization laser light whose phase has been modulated by the phase shifter 24 onto a non-single crystal semiconductor thin film 28 disposed on the substrate 27 to be crystallized. FIG. 2 is a diagram showing one example of the crystallization optical system 2 using the phase shifter 24 used in the laser crystallization apparatus 1 shown in FIG. 1. The excimer illumination optical system 20 further comprises a laser light source 21, a beam expander 22, and a homogenizer 23 which are disposed on the same optical axis. The laser light source 21 preferably has high energy, for example, of 1 J/cm2 for melting and crystallizing the semiconductor thin film 28 formed on the substrate 27. Therefore, for example, excimer laser light such as krypton fluoride (KrF) excimer laser (wavelength of 248 nm) or xenon chloride (XeCl) excimer laser (wavelength of 308 nm) is preferably used. The excimer laser light source 21 generally used in the PMELA apparatus is a pulse oscillation type, an oscillation frequency is, for example, 100 Hz to 300 Hz, and a pulse width is of, for example, 20 nsec to 100 nsec in a half value width. In the present embodiment, the KrF excimer laser light having a half value width of 25 nsec is used. The KrF excimer laser light irradiated onto the substrate 27 to be crystallized has light energy, for example, of about 1 J/cm2. Assuming that oscillation frequency is, for example, 100 Hz, and an irradiation area of the excimer laser light is, for example, 2 mm×2 mm. The excimer laser light is irradiated step by step, while the substrate 27 to be crystallized is moved by a substrate holding stage 29, for example, by a step of 2 mm. In this case, a moving speed of the substrate 27 becomes 200 mm/sec. The beam expander 22 expands an incident laser light beam, and is constituted of a concave lens 22a for expanding light and a convex lens 22b for forming parallel light. The homogenizer 23 has a function of determining a dimension of a cross section in an XY direction of the incident laser light beam, and homogenizing a light beam intensity distribution within a determined shape. For example, a plurality of X-direction cylindrical lenses are arranged in a Y-direction to form a plurality of light fluxes arranged in the Y-direction, then each light flux is re-distributed in the Y-direction by an X-direction condenser lens. Similarly, a plurality of Y-direction cylindrical lenses are arranged in the X-direction to form a plurality of light fluxes arranged in the X-direction, then each light flux is re-distributed in the X-direction by a Y-direction condenser lens. That is, as shown in FIG. 2, the homogenizer comprises a first homogenizer constituted of a first fly eye lens 23a and a first condenser lens 23b, and a second homogenizer constituted of a second fly eye lens 23c and a second condenser lens 23d. The first homogenizer homogenizes incident angles of the laser light on the phase shifter 24, and the second homogenizer homogenizes an in-plane laser light intensity on the phase shifter 24. Therefore, the KrF excimer laser light is conditioned to illumination light having a predetermined angle spread and a homogenized light intensity in a cross section by the homogenizer 23 to thereby illuminate the phase shifter 24. The phase shifter 24 is one example of a phase modulating element, and constituted, for example, by stepping a quartz glass substrate. Diffraction and interference of the laser light are caused in step boundaries, thus periodic distribution is given to the laser light intensity, for example, a phase difference of 180° is made in right and left side of the boundary. The phase shifter 24 for making the right/left phase difference of 180° modulates the phase of incident light, and constitutes an inverse peaked light intensity distribution symmetric with respect to the step boundary. A step height (thickness difference) d required for forming the light intensity distribution is obtained by d=λ/2(n−1), where λ denotes a wavelength of the laser light, and n denotes a refractive index of a transparent substrate of the phase shifter 24. From this equation, the phase shifter 24 can be manufactured, for example, by forming a step height corresponding to a predetermined phase difference on a quartz glass substrate. For example, assuming that the refractive index of the quartz substrate is 1.46, the XeCl excimer laser light has a wavelength of 308 nm, and therefore the step height for making a phase difference of 180° becomes 334.8 nm. The step of the quartz glass substrate can be formed by selective etching or focused ion beam (FIB) processing, for example. In the phase shifter 24, the step is formed in such a manner that the phase of the excimer laser light is shifted by a half wavelength at the boundary to modulate the incident light to form the inversed peaked light intensity distribution. As a result, the laser light, which irradiates the semiconductor film, has a light intensity distribution patterned in such a manner as to have an inverse peak. As for the light intensity distribution, light intensity at a portion corresponding to the phase shift portion has a minimum. According to this method, a predetermined laser light intensity distribution can be realized without blocking the excimer laser light by a metal pattern used in another method. As to the excimer laser light passed through the phase shifter 24, a direction of the laser light is changed in a direction to the substrate 27 to be crystallized by a reflecting mirror 25. The laser light is imaged in a predetermined light intensity distribution on the non-single crystal semiconductor thin film 28 on the substrate 27, which is positioned at a conjugate position with the phase shifter 24, by the excimer imaging optical system 26 whose aberration has been corrected. The reflecting mirror 25 is designed in such a manner as to reflect ultraviolet light while pass visible light. The imaging optical system 26 comprises a lens group constituted, for example, of a plurality of calcium fluoride (CaF2) lenses and fused silica lenses. The imaging optical system 26 is a long focal distance lens having performances such as a reduction ratio: 1/5, N.A.: 0.13, resolution: 2 μm, depth of focus: ±10 μm, and focal distance: 50 mm to 70 mm. The imaging optical system 26 arranges the phase shifter 24 and the non-single crystal semiconductor thin film 28 on the substrate 27 in an optically conjugate position with respect to the excimer laser light. In other words, the non-single crystal semiconductor thin film 28 is positioned on a plane optically conjugate with the phase shifter 24 (e.g., imaging plane of the imaging optical system). The imaging optical system 26 comprises an aperture disposed between the lenses. With regard to the substrate 27 to be crystallized, in general, the non-single crystal semiconductor thin film 28 is formed on the substrate via an insulating film, and another insulating film is provided on the semiconductor film as a cap film. The substrate is, for example, a transparent glass substrate, plastic substrate, or a semiconductor substrate (wafer) such as silicon. The non-single crystal semiconductor thin film 28 to be crystallized is an amorphous silicon film, a polycrystal silicon film, a sputtered silicon film, a silicon germanium film, or a dehydrogenated amorphous silicon film. The substrate 27 to be crystallized used in the present embodiment, the dehydrogenerated amorphous silicon film 28 is formed in a desired thickness, for example, of 50 nm on the glass substrate. The substrate 27 is detachably mounted on the substrate holding stage 29 which places the substrate in a predetermined position and which is movable in X, Y, and Z-directions. As described above, the laser crystallization apparatus 1 is a projecting type crystallization apparatus. The homogenized laser light is modulated in phase by the phase shifter 24 to thereby form crystallization laser light having an inverse peaked light intensity distribution, and the laser light is irradiated onto the non-single crystal semiconductor thin film 28 formed on the substrate 27. In the non-single crystal semiconductor thin film 28 molten by the laser light irradiation, the crystallization proceeds in a horizontal direction in accordance with the light intensity distribution, and the crystallized semiconductor film 28 having large single-crystal grains, for example, of about 10 μm can be formed. As described above, in the laser crystallization apparatus 1, an image of the phase shifter 24 is formed on the non-single crystal semiconductor thin film 28 formed on the substrate 27 using the excimer laser light having high energy of about 1 J/cm2. As a result, the irradiated region of the non-single crystal semiconductor thin film 28, on which the image has been formed, is molten, then solidified and crystallized. In this process, the shift in the imaging position of the laser light caused by the thermal lens effect of the excimer imaging optical system 26 installed between the phase shifter 24 and the substrate 27 directly adversely affects the quality of the crystallized semiconductor film. Though calcium fluoride and fused silica are preferred lens materials for the excimer imaging optical system 26, transmittance of the calcium fluoride and fused silica for ultraviolet rays in a wavelength region of 200 nm to 300 nm is about 90%, therefore rest of about 10% is absorbed by the lens or a lens holder even if the lens without anti-reflection coating is used. Moreover, since thermal conductivities of calcium fluoride and fused silica are 9.71 (W/m·° C.) and 1.35 (W/m·° C.), respectively, it can be expected that the temperature change of fused silica is larger than that of calcium fluoride. For example, when 200 Hz pulse excimer laser light irradiation is performed for about five minutes with the above-described excimer laser light intensity, it is estimated that a temperature rise of about 5° C. is generated in the calcium fluoride lens, while a temperature rise of about 10° C. to 15° C. is generated in the fused silica lens. In addition, a thermal expansion coefficient and a temperature coefficient of refractive index are about 2×10−5/° C., −1×10−5/° C. in calcium fluoride, respectively, and 4×10−6/° C., 1×10−5/° C. in fused silica, respectively. Therefore, considering the temperature characteristics of the lens materials in the excimer imaging optical system 26 using the lens group of a plurality of lenses, for example, the imaging position shifts by 10 μm when the lens temperature changes by 1° C. in an excimer imaging optical system. For example, the temperature change in the excimer imaging optical system 26 is estimated about 10° C., as described above, the shift in the imaging position due to the thermal lens effect becomes several tens μm to 100 μm, and it is supposed that the shift is much larger than focal depth ±10 μm of the excimer imaging optical system 26. If the imaging position of the laser light for the crystallization shifts from the non-single crystal semiconductor film 28 on the substrate 27, then a predetermined light intensity distribution is not obtained on the non-single crystal semiconductor film 28, and it causes the laser light intensity at the phase reversed portion not to be sufficiently low. Therefore, the melt temperature at that portion is higher than that when the non-single crystal semiconductor film 28 is in the imaging position, thus a crystal nucleus formation delays. As a result, a timing to start the crystallization is delayed. Additionally, the crystal nuclei are easily generated at random places even in portions other than the reversed portion of the laser light. As a consequence, an opportunity to meet growing crystal grains with one another increases, thus the size of the crystal grain grown is reduced. That is, the quality of the crystallized silicon film is degraded. Therefore, the imaging position of the excimer imaging optical system 26 by the thermal lens effect is preferably corrected. Next, the substrate height correction system 3 will be described. The substrate height correction system 3 is to correct the shift of the imaging position caused by the thermal lens effect of the excimer imaging optical system 26 in addition to correct a shift attributed to flatness of the substrate 27. One example of a constitution of the substrate height correction system 3 of the present embodiment is shown in FIG. 1. In the substrate height correction system 3, a light source 31 for measurement, for example, visible laser light source, emits visible laser light, for example, helium neon (He—Ne) laser light, to measure imaging position. The visible laser light is converged by a converging lens 32, and directed to the substrate 27 to be crystallized by a half mirror 33. The visible laser light for the measurement illuminates the non-single crystal semiconductor film 28 on the substrate 27 through the excimer imaging optical system 26. However, the excimer imaging optical system 26 is designed for the excimer laser which is ultraviolet light. Therefore, when the visible laser light for the measurement is applied into the excimer imaging optical system 26, aberration is generated. An visible light correction optical system, for example, a visible light correction lens 34, is disposed between the reflecting mirror 25 and the half mirror 33, and out of a light path of the excimer laser light. The visible light correction optical system corrects the aberration of the visible light by the excimer imaging optical system 26. Thus, the visible light correction optical system is designed in such a manner that an imaging plane of the visible laser light for the measurement coincides with that of the excimer laser light for the crystallization. The reflecting mirror 25 for excimer laser light is designed to transmit the visible light as described above. The non-single crystal semiconductor film 28 on the substrate 27 is disposed in a position conjugated with the focal position of the converging lens 32 with respect to the visible light. The measurement laser light reflected on the non-single crystal semiconductor film 28 passes through the excimer imaging optical system 26 and the visible light correction lens 34 again, and passes through the half mirror 33 and a pinhole 35 to reach a photodetector 36. The pinhole 35 is disposed in a position conjugated with the imaging position on the substrate 27 side with respect to the laser light for the measurement through the visible light correction lens 34 and the excimer imaging optical system 26. A size of the pinhole 35 is preferably equal to that of the image of the measurement laser light on the imaging position on the substrate 27. By measuring intensity of the measurement laser light passed through the pinhole, or distortion of a visible light image on the non-single crystal semiconductor film 28 by the photodetector 36, a shift in the position of the non-single crystal semiconductor film 28 on the substrate 27 from the imaging position of the crystallization laser light can be detected. As the photodetector 36, for example, a two-dimensional CCD imaging device, a photodiode, a phototransistor, or a photo-multiplier tube can be used. An electric signal corresponding to the shift is detected and converted by the photodetector 36, and then is processed by a signal processing unit 37. A correction amount output from the signal processing unit 37 is send to a stage driving unit 50. The substrate holding stage 29 can be moved under a control of the stage driving unit 50 to correct the shift of the semiconductor film 28 from the imaging position. A flowchart of a method for correcting the height of the non-single crystal semiconductor film 28 by measuring an incident light intensity from the non-single crystal semiconductor film 28 using the photodetector 36 is shown in FIG. 3. First, in step 102, the non-single crystal semiconductor film 28 is illuminated with the visible laser light for the measurement. The laser light for the measurement is reflected on the non-single crystal semiconductor film 28, and reaches the photodetector 36 through the pinhole 35 disposed in the position conjugated with the imaging position on the semiconductor film 28 side with respect to the measurement laser light. In step 104, the intensity of the measurement light passed through the pinhole 35 is measured by the photodetector 36. As an arrangement described above, the size of the image of the measurement laser light on the pinhole 35 plane is equal to that on the non-single crystal semiconductor film 28. If the non-single crystal semiconductor film 28 is in the imaging position, then the size of the image of the measurement laser light on the non-single crystal semiconductor film 28 becomes smallest. As compared with in the imaging position, if the non-single crystal semiconductor film 28 is shifted from the imaging position, then an image of the laser light on the semiconductor film 28 defocuses and enlarges. As a result, the size of the image of the measurement laser light on the pinhole 35 plane is larger than that of the pinhole. Since the size of the pinhole 35 is equal to that of the image of the measurement laser light in the imaging position on the semiconductor film 28 side, the intensity of the measurement laser light reaching the photodetector 36 through the pinhole 35 is reduced as compared with the case where the non-single crystal semiconductor film 28 is in the imaging position. In step 106, the signal processing unit 37 decides whether the intensity of the reflected light is maximum. If the intensity is not maximum, then the substrate holding stage 29 is moved upward or downward in the height (Z-axis) direction through the stage driving unit 50, in step 108. Then, the process returns to the step 104 to repeat the measurement of the reflected light intensity from the semiconductor film 28. When the light intensity detected in the step 106 becomes maximum in this manner, substrate position correction ends, and the excimer laser light for the crystallization is irradiated. In the measurement, the light path of the visible laser light for measurement includes the same excimer imaging optical system 26 as for the crystallization laser light. Therefore, even if the temperature of the excimer imaging optical system 26 changes, thus the imaging position of the excimer laser light for the crystallization shifts by the thermal lens effect, the imaging position of the visible laser light for the measurement similarly shifts. Therefore, if the position of the non-single crystal semiconductor film 28 is corrected in an optical axis direction (Z-axis direction) and coincided with the imaging position of the visible laser light for the measurement, then the non-single crystal semiconductor film 28 can also be coincided with the imaging position of the excimer laser light for the crystallization. The position of the non-single crystal semiconductor film 28 in the Z-axis direction is corrected immediately before pulse irradiation of the excimer laser light for the crystallization in such a manner that the reflected measurement light intensity from the non-single crystal semiconductor film 28 detected by the photodetector 36 is constantly maximized. Accordingly, the imaging position of the non-single crystal semiconductor film 28 on the substrate 27 can be corrected, so that both the imaging position shift caused by the thermal lens effect of the excimer imaging optical system 26 and the imaging position shift attributed to flatness of the substrate 27 can be corrected simultaneously. A second embodiment relates to a correction system 3 and method in which a specific mask pattern is imaged on a non-single crystal semiconductor film 28 on a substrate 27, a reflected image from the non-single crystal semiconductor film 28 is detected by a two-dimensional photodetector 36A, and then an imaging position is corrected using a two-dimensional image detected. One example of the present embodiment is shown in FIG. 4. In FIG. 4, an optical system 2 for crystallization is the same as that in FIG. 1, and therefore a crystallization optical system 2 other than an excimer imaging optical system 26 is omitted. In the present embodiment, visible laser light from a light source 31 for measurement illuminates an image mask 42 having a predetermined pattern for measurement through an illuminating lens 41. The image of the mask pattern for the measurement is reflected on a half mirror 33, directed toward the substrate 27 to be crystallized, and imaged on the non-single crystal semiconductor film 28 on the substrate 27 through a visible light correction lens 34, and the excimer imaging optical system 26. An visible light optical system is designed in such a manner that the imaging position of the visible laser light coincides with that of the excimer laser light for crystallization. The mask pattern reflected from the non-single crystal semiconductor film 28 returns along a reverse path including the excimer imaging optical system 26 and visible light correction lens 34, and passes through the half mirror 33 to reach a light receiving face of the two-dimensional photodetector 36A. In the present embodiment, a pinhole 35 used in the first embodiment is removed from the light path, and the two-dimensional photodetector 36A is disposed in a position where the pinhole 35 has been disposed. That is, a photo-detecting surface of the two-dimensional photodetector 36A is disposed in a position conjugated with the imaging position of the measurement laser light on the non-single crystal semiconductor film 28 side. By this arrangement, if the non-single crystal semiconductor film 28 shifts from the imaging position of the laser light for the crystallization, that is, the imaging position of the visible laser light for the measurement, then the reflected image detected by the two-dimensional photodetector 36A blurs. As the two-dimensional photodetector 36A, for example, a two-dimensional CCD imaging device can be used. The image obtained by the two-dimensional CCD imaging device 36A is processed by a signal processing unit 37. The imaging position shift of the non-single crystal semiconductor film 28 is corrected by adjusting a position of a substrate holding stage 29 via a stage driving unit 50. A flowchart of a method for correcting a shift of the non-single crystal semiconductor film 28 on the substrate 27 with respect to the imaging position using the two-dimensional image is shown in FIG. 5. For example, a line and space pattern disposed at a predetermined interval can be used as the mask pattern for the measurement. In step 122, the mask pattern for the measurement is projected on the non-single crystal semiconductor film 28 through the visible light correction lens 34 and the excimer imaging optical system 26. The mask pattern reflected on the non-single crystal semiconductor film 28 returns along a reverse path, and passes through the converging lens 32, and then an image of the mask pattern is photographed by the two-dimensional photodetector 36A in step 124. In step 126, a reflected image of the mask pattern for the measurement photographed by the two-dimensional photodetector 36A is processed by the signal processing unit 37, and clearness of the image is evaluated. Specifically, while the height of the substrate 27 to be crystallized is changed little by little, the clearness of the image of the mask pattern is evaluated, and then a position where the image becomes clearest is decided. At this position, the imaging position of the excimer imaging optical system 26 coincides with the non-single crystal semiconductor film 28. To evaluate the clearness of the image, for example, clearness of an outer shape of the mask pattern, and/or contrast between line and space portions can be used. If it is decided that the image of the mask pattern for the measurement is not clearest, at step 128, then the substrate holding stage 29 is moved in a height (Z-axis) direction via the stage driving unit 50 to change the height of the non-single crystal semiconductor film 28. Then the process returns to step 122, and the measurement is repeated. If it is decided that the image of the mask pattern is clearest, then the non-single crystal semiconductor film 28 is coincide with the imaging position of the laser light for the crystallization. Then the process proceeds to the irradiation with the laser light for the crystallization. In the present embodiment, since the excimer imaging optical system 26 is incorporated in the light path of the laser light for the measurement, the imaging position shift generated by the thermal lens effect of the excimer imaging optical system 26 is also corrected as the shift of the imaging position of the laser light for the measurement. Therefore, according to the present embodiment, it can be corrected both the imaging position shift of the excimer imaging optical system 26 caused by the thermal lens effect and the imaging position shift attributed to the flatness of the substrate 27 to be crystallized simultaneously. A third embodiment relates to one example of a correction system capable of more precisely correcting a substrate position even if a change of lens temperature of an excimer imaging optical system 26 is large. Exactly speaking, a temperature coefficient of refractive index of a lens differs by wavelength of lights, i.e., temperature change in the refractive index of the lens differs for excimer laser light and visible laser light. In the present embodiment, the difference of the temperature change in refractive index of the lens caused by difference of wavelength of the light is further corrected. The refractive index of the lens varies with the wavelength of light passed. For example, in calcium fluoride (CaF2), the refractive index for ultraviolet light having a wavelength of 0.2 μm is 1.4951, whereas the refractive index for visible light having a wavelength of 0.5 μm is 1.4365. The difference is about 4%. In fused silica for ultraviolet rays (UV-SiO2), the refractive index for ultraviolet light having a wavelength of 0.2144 μm is 1.5337, whereas the refractive index for visible light having a wavelength of 0.6438 μm is 1.4567. The difference is more than 5%. Temperature coefficient of the refractive index and a thermal expansion coefficient are −0.95 to −1.17×10−5/° C. and 1.65 to 1.94×10−5/° C. in CaF2, respectively, and 1.00×10−5/° C. and 4.0×10−6/° C. in fused silica, respectively. Though influences to these values by temperature changes are not large in each lens, if the temperature change becomes large in the excimer imaging optical system 26 using a plurality of lenses, then resulting difference in imaging position shifts due to lights having different wavelengths caused by the effect cannot be negligibly small. Therefore, to precisely correct the substrate position, the difference between imaging position shifts due to different wavelengths has to be corrected considering wavelength dependence of the refractive indexes, temperature coefficients of the refractive index, and thermal expansion coefficient of the lens as described above. However, since the lens constitution of the excimer imaging optical system 26 differs with the apparatus, it is not easy to universally correct the difference in the imaging positions due to the different light wavelengths caused by the temperature change of the optical system. To execute it practically, for the excimer imaging optical system 26 to be used, the temperature of the excimer imaging optical system 26 is changed by predetermined amounts in advance, then the shift in the imaging position at each temperature is measured both for the excimer laser light and the visible laser light. These measurement results are stored in the signal processing unit 37 as, for example, a correlation table for the optical system temperature-imaging position shift for that excimer imaging optical system. In addition, as shown in FIG. 6, a temperature sensor 45 is attached to the excimer imaging optical system 26 to monitor the temperature of the excimer imaging optical system 26. As the temperature sensor 45, for example, a semiconductor temperature detection element, such as a thermistor, or a thermocouple, such as a copper-constantan, can be used. The difference of the imaging position shift between the excimer laser light and the visible laser light caused by the different temperature coefficients of the refractive index of the excimer imaging optical system 26 can further be corrected based on the monitored lens temperature of the excimer imaging optical system 26, and correlation table for the optical system temperature-imaging position shift stored beforehand in addition to the correction of the imaging position provided in the first or second embodiment FIG. 7 is a flowchart showing correction of a substrate position by the present embodiment considering the difference of the shift in the imaging position between the excimer laser light and the visible laser light caused by the difference of temperature coefficient of the refractive index of the excimer imaging optical system 26. The correlation table for the optical system temperature-imaging position shift amount is prepared and stored in the signal processing unit 37 in advance. Furthermore, a critical temperature Tc of the excimer imaging optical system 26 requiring additional substrate position correction is set. That is, the temperature of the excimer imaging optical system 26, at which the difference of above-described shift in the imaging positions reaches to an allowable predetermined value, is set as the critical temperature Tc consulting the correlation table. The allowable shift in the imaging positions can be set, for example, to a position where a focal distance of the excimer imaging optical system 26 is shifted by 7λ/100 in wave aberration. On one hand, the shift of the position of the substrate 27 due to the thermal lens effect by the temperature change of the excimer imaging optical system 26 is corrected using, for example, the method according to the first or second embodiment, in step 142. Accordingly, the non-single crystal semiconductor film 28 on the substrate 27 is coincided with the imaging position of the excimer laser light for the crystallization without considering the difference in imaging positions due to the difference of the temperature coefficient of the refractive index of the lens between the excimer laser light and the visible laser light. On the other hand, in step 144, a temperature T of the excimer imaging optical system 26 is measured by the temperature sensor 45 in parallel with step 142. It is decided in step 146 whether the measured temperature T is higher than the critical temperature Tc. If the temperature T is higher than the critical temperature Tc, then it is decided that an additional substrate position correction is required, and then the process proceeds to step 148. If the temperature T is lower than the critical temperature Tc, then an additional substrate position correction is not required, and the process proceeds to the irradiation of the laser light for the crystallization. In step 148, an additional position correction amount Δz of the substrate 27 corresponding to the measured temperature T is obtained from the correlation table for the optical system temperature-imaging position shift stored in the signal processing unit 37. Then, in step 150, the substrate holding stage 29 is additionally corrected by the position correction amount Δz via the stage driving unit 50, and the process proceeds to the irradiation of the laser light for crystallization. Thus, it can be more precisely corrected not only the imaging position shift caused by the flatness of the substrate 27 and the imaging position shift due to the thermal lens effect of the excimer imaging optical system 26, but also the shift in the imaging positions caused by the difference in the temperature coefficient of the refractive index of the imaging optical system 26 by the wavelength between laser light for crystallization and that for measurement. As described above, according to the present invention, it can be simultaneously corrected both the shift of the imaging position by the thermal effects of the optical system for the crystallization and the shift of the imaging position due to the flatness of the substrate to be crystallized. As a result, there can be provided the laser crystallization apparatus and crystallization method, capable of stabilizing the crystallization process, and efficiently crystallizing the high-quality semiconductor thin film. The present invention is not limited to the above-described embodiments, and various modifications and implementations can be executed without departing from the scope in its implementation stage. Furthermore, the above-described embodiments include various stages, and various inventions can be extracted by an appropriate combination of a plurality of described constituting elements. For example, several constituting elements can be deleted from all constituting elements described in the embodiment. The above description of the embodiments has been given in such a manner that any person skilled in the art can prepare or make use the present invention. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
	summary
	claims	1. A system for producing a radiopharmaceutical, said system comprising:a particle accelerator for generating a beam of charged particles having a maximum beam power of less than, or equal to, approximately 200 W, the beam consisting essentially of particles having a minimum energy greater than, or equal to, 5 MeV, and for directing the beam of charged particles along a path;a target positioned in the path of the beam of charged particles, said target serving to receive a target substance having a composition selected for producing a radioactive substance during interaction with the beam of charged particles; anda radiopharmaceutical micro-synthesis system having at least one microreactor and/or microfluidic chip, said radiopharmaceutical micro-synthesis system for receiving the radioactive substance, receiving at least one reagent, and synthesizing the radiopharmaceutical. 2. A biomarker generator for producing radiopharmaceuticals, said biomarker generator comprising:a target for holding a target substance that produces a selected radioisotope when bombarded by charged particles accelerated to energies greater than or equal to the nuclear binding energy of the target substance;a particle accelerator for generating a particle beam having a maximum beam power of 200 W, said particle beam comprising charged particles with an average energy at least equal to the nuclear binding energy of said target substance, said particle accelerator configured to bombard said target substance with said charged particles and produce said selected radioisotope; anda radiopharmaceutical micro-synthesis system comprising at least one microreactor or microfluidic chip, said radiopharmaceutical micro-synthesis system synthesizing a radiopharmaceutical from the selected radioisotope. 3. The biomarker generator of claim 2 wherein said average energy of said charged particles is within a range selected from the group consisting of 5 MeV to 18 MeV, 5 MeV to 10 MeV, 7 MeV to 10 MeV, 8 MeV to 10 MeV, and 7 MeV to 18 MeV. 4. The biomarker generator of claim 3 wherein said average energy of said charged particles is in the range of 5 MeV to 10 MeV. 5. The biomarker generator of claim 2 wherein said particle accelerator is a cyclotron and said charged particles are selected from the group consisting of protons and deuterons. 6. The biomarker generator of claim 5 wherein the target is located within a magnetic field generated by said cyclotron, said particle beam bombarding said target substance without exiting said magnetic field. 7. The biomarker generator of claim 2 wherein said charged particles are selected from the group consisting of protons and deuterons and wherein said average energy of said charged particles is in the range of 5 MeV to 10 MeV and said maximum beam power is 200 W. 8. The biomarker generator of claim 2 wherein said maximum beam power is selected from the group consisting of 50 W, 75 W, 100 W, 125 W, 150 W, and 175 W. 9. The biomarker generator of claim 8 wherein said maximum beam power is 50 W. 10. The biomarker generator of claim 2 producing said selected radioisotope per production run in a maximum quantity of approximately 2.59 GBq (70 mCi). 11. The biomarker generator of claim 2 wherein said selected radioisotope is 18F and said radiopharmaceutical is [18F]2-fluoro-2-deoxy-D-glucose, said particle accelerator producing a run of fluorine-18 with a maximum radioactivity selected from the group of approximately 0.666 GBq (18 mCi) and approximately 0.185 GBq (5 mCi). 12. A biomarker generator for producing on the order of one unit dose of a radiopharmaceutical, comprising:a target for holding a target substance that produces a selected radioisotope when bombarded by charged particles accelerated to energies greater than or equal to the nuclear binding energy of the target substance;a cyclotron for generating a particle beam having a maximum beam power in the range of 200 W, said particle beam comprising charged particles selected from the group consisting of protons and deuterons with an average energy in the range of 5 MeV to 10 MeV, said particle accelerator configured to bombard said target substance with said charged particles and produce said selected radioisotope; anda micro-reaction device for synthesizing a radiopharmaceutical from the selected radioisotope, said micro-reaction device comprising components selected from the group consisting of microfluidic reactors and microfluidic chips. 13. The biomarker generator of claim 12 wherein the target is located within a magnetic field generated by said cyclotron, said particle beam bombarding said target substance without exiting said magnetic field. 14. The biomarker generator of claim 12 producing said selected radioisotope per production run in a maximum quantity of approximately 2.59 GBq (70 mCi). 15. The biomarker generator of claim 12 wherein said selected radioisotope is 18F and said radiopharmaceutical is [18F]2-fluoro-2-deoxy-D-glucose, said particle accelerator producing a run of fluorine-18 with a maximum radioactivity selected from the group of approximately 0.666 GBq (18 mCi) and approximately 0.185 GBq (5 mCi). 16. The biomarker generator of claim 12 wherein said maximum beam power is selected from the group consisting of 50 W, 75 W, 100 W, 125 W, 150 W, and 175 W. 17. The biomarker generator of claim 16 wherein said maximum beam power is 50 W. 18. A method of producing on the order of one unit dose of a radiopharmaceutical, said method comprising the steps of:providing a target substance that produces a selected radioisotope when bombarded by charged particles accelerated to energies greater than or equal to the nuclear binding energy of the target substance;generating a particle beam of charged particles with a maximum beam power of 200 W, said charged particles selected from the group consisting of protons and deuterons, said charged particles accelerated to an average energy at least equal to the nuclear binding energy of said target substance;producing said radioisotope in a maximum quantity per production run on the order of one precursory unit dose from said target substance by bombarding said target substance with said charged particles;synthesizing said radioisotope into a maximum quantity of a radiopharmaceutical on the order of one unit dose using a micro-reaction device selected from the group consisting of microfluidic reactors and microfluidic chips. 19. The method of claim 18 wherein said step of generating a particle beam further comprising the step of providing a cyclotron to generate a particle beam, said method further comprising the steps of:locating the target substance in a magnetic field generated by said cyclotron; andbombarding said target substance with said particle beam without said particle beam exiting said magnetic field. 20. The method of claim 18 wherein said maximum quantity of said selected radioisotope produced per production run is approximately 2.59 GBq (70 mCi). 21. The method of claim 18 wherein said selected radioisotope is 18F and said radiopharmaceutical is [18F]2-fluoro-2-deoxy-D-glucose, said maximum quantity of said selected radiopharmaceutical produced per production run selected from the group of approximately 0.666 GBq (18 mCi) and approximately 0.185 GBq (5 mCi). 22. The method of claim 18 wherein said maximum beam power is selected from the group consisting of 50 W, 75 W, 100 W, 125 W, 150 W, and 175 W. 23. The method of claim 22 wherein said maximum beam power is 50 W. 24. The method of claim 18 wherein said average energy of said charged particles is within a range selected from the group consisting of 5 MeV to 18 MeV, 5 MeV to 10 MeV, 7 MeV to 10 MeV, 8 MeV to 10 MeV, and 7 MeV to 18 MeV. 25. The method of claim 24 wherein said average energy of said charged particles is in the range of 5 MeV to 10 MeV. 26. The method of claim 18 wherein said charged particles are selected from the group consisting of protons and deuterons and wherein said average energy of said charged particles is in the range of 5 MeV to 10 MeV and said maximum beam power is 200 W.
	abstract	The invention comprises a beam adjustment method and apparatus used to perform energy adjustments on circulating charged particles in a synchrotron previously accelerated to a starting energy with a traditional accelerator of the synchrotron. The beam adjustment system uses a radio-frequency modulated potential difference applied along a longitudinal path of the circulating charged particles to accelerate or decelerate the circulating charged particles. Optionally, the beam adjustment system phase shifts the applied radio-frequency field to accelerate or decelerate the circulating charged particles while tightening spatial distribution of a grouped bunch of the circulating charged particles. Optionally, the beam adjustment system simultaneously radially focuses the circulating charged particles using two or more gaps with focusing and/or defocusing edges. The beam adjustment system facilitates treating multiple layers or depths of the tumor without hysteresis and/or between the repeating slow steps of reloading the synchrotron.
	abstract	A charged particle beam apparatus capable of automatically measuring an image magnification error of an apparatus and capable of automatically calibrating the image magnification in high precision is provided. To this end, while an image processing operation of either an auto-correlation function or an FFT transformation is employed with respect to a scanning image of a reference material having a periodic structure, the averaged pitch dimension of which is known, averaged periodic information owned by the scanning image is detected so as to measure an image magnification error of the apparatus. Also, the information as to the acquired image magnification error is fed back to an image magnification control means of the apparatus so as to automatically execute a calibration as to the image magnification in high precision.
055315453	summary	FIELD OF INVENTION The present invention relates to cable bolt structures, related components and method for use in underground mines, such being useful in achieving ground control as to mine roof strata disposed above a particular mine opening. DESCRIPTION OF PRIOR ART AND BRIEF HISTORY OF CABLE BOLT SUPPORTS Incorporated by way of reference herein is the inventors' prior filed patent application entitled: CABLE BOLT STRUCTURE AND RELATED COMPONENTS, application Ser. No. 08/332,266 filed 31 Oct. 1994. This application is presently on pending status. Also fully incorporated by way of reference are Seegmiller U.S. Pat. Nos. 5,015,125 and 5,215,411. Other patent literature which is tangentially related include Gillespie U.S. Pat. Nos. 5,230,589 and 5,259,703. All of the above patent literature, including additional literature recited in the inventors' pending patent application above referenced, include other references and teach in rather substantial detail the prior art, and problem situations addressed thereby. The patents of the co-inventor herein, Seegmiller U.S. Pat. Nos. 5,015,125 and 5,215,411, teach what the co-inventor describes as a pressure bubble technique. This is to say, a tubular member is positioned in a selected borehole of mine roof strata and is provided with a reaction plate or bearing plate that abuts the mine roof surface about the borehole. In both the prior and the present applications of the co-inventors herein, a take-up torquing nut is threaded upon the tubular member and directly abuts the bearing plate utilized. Cable bolt structure is disposed in the borehole and is anchored at its remote end within the upper reaches of the hole. In the present invention the cable bolt structure includes a cable length having a friction-bubble-producing enlargement at or near the proximate end thereof. The cable bolt of course is disposed through the tubular member and the enlargement is initially seated, preferably in a friction fit, for preinstallation purposes, in a counterbore area supplied the bore of the tubular member at its proximate end. In dynamic operation, such enlargement coacts in an interference fit with the primary bore of the tubular member so as to radially expand in its elastic range the tubular member at the section thereof directly contacting and/or proximate the enlargement. The takeup torquing nut is turned so as to provide an initial preload of perhaps one to two tons tension relative to the cable bolt. In active mode, as the mine strata settles and the mine roof surfaces dilates, the cross-sectional enlargement of the cable bolt, relatively speaking, progresses upwardly relative to the tubular member; or, looking at it from a reverse point of view, and what actually occurs, the descending tubular member experiences a relative movement, i. e. relative to the enlargement, so that a controlled resistance feature is present as between the cable bolt at its enlargement and the radially elastically expanded tubular member supplied. Particular attention is called to a primary feature in the present invention wherein the enlarged portion of the cable bolt finds its genesis in the provision of either a cylindrical gripping member disposed about and secured to the cable length of the cable bolt or, alternatively, one or more elongated cylindrical members such as roll pins which are situated on the king wire of the cable length interior of the cable strands. Whether roll pins or their equivalent are employed, or whether simply a circular gripping member is used, it is requisite that the surface hardness of these elements be at least of the order of the surface hardness of the cable strands. Thus, what is not wanted is any appreciable plastic deformation of the cylindrical members or roll pins. Any possible scarring by the cable strands of the roll pins or cylindrical member should be held to a minimum. Therefore, the surface hardness of the roll pins or their equivalence, or the cylindrical member, should be held to to a point not less than minus 15 percent of the surface hardness of the cable strands of the cable bolt. When such a condition exists, then the roll pins are fully functional in holding outwardly the cable strands so that these will frictionally engage and indeed radially elastically expand the tubular member proximate that portion thereof which the enlargement engages. It is this elastic expansion of the tubular member that produces the radial, elastic, contractive or compressive forces needed to generate heightened force normals for producing the resistance loading desired. Thus, in such an arrangement, a dynamic resistances offered by the invention achieves tensile loading of from perhaps 23 to even 40 tons. This is a substantial resistance, and one which is needed for appropriate mine roof ground control. Further, this resistance loading is dynamic in operation in that further dilation of the mine roof will maintain or perhaps even increase the resistance loading of the cable bolt. None of the prior art as known to the applicants teach the concept of producing a circumferential, essentially cylindrical sectional enlargement of a cable bolt wherein there is essentially no plastic deformation experienced as to elements of the cable bolt wherein the requisite radial elastic expansion of the tubular member is nullified. BRIEF DESCRIPTION OF THE PRESENT INVENTION In the present invention, a cable bolt installation is provided a selected mine roof borehole produced in mine roof strata. A cable bolt structure is provided a cable length having a proximate end and also a remote end constructed for anchoring within the essentially upper reaches of the borehole. Epoxy anchoring, point anchors, etc., provide the essential end-anchoring of the cable length. Proximate the proximate end of the cable length is structure providing a circumferential enlargement as contributed by one or more cylindrical elements. Such elements are disposed either over the king wire and interior of the cable strands, or over the cable length proper. An elongated tubular member is disposed over the cable and is provided with a reaction plate, either secured to or slipped over the end of the cable bolt. The tubular member is preferably exteriorly threaded, and a torquing nut is threaded thereon and abuts the reaction plate, the latter being designed to thrust against the mine roof surface surrounding the applicable borehole. A tension pre-load, of the cable bolt, of perhaps 1-2 tons is produced by torquing the nut against the reaction plate. The interior bore of the tubular member receives the cable bolt and reacts with its circumferential enlargement, operating in essentially the elastic range of the tubular member, in offering a controlled resistance to tubular member travel relative to said cable bolt. To facilitate assembly, it is desire that there be a proximate counterbore or bore enlargement, relative to the proximate end of the tubular member, and that its junction with the bore proper be a conically tapered portion. It is preferred that, initially, the enlarged portion of the cable bolt be in friction-fit relationship relative to the enlarged bore portion; subsequently, the nut is tightened for an initial desired preload. As the mine roof strata tends to settle, the mine roof surface dilates so as to urge the tubular member downwardly. The latter's coaction with the enlargement of the cable bolt produces a circumferential, at least partially elastic enlargement of the tubular member at that portion thereof which is transversely proximate such enlargement. This creates a moving pressure bubble, as between the tubular member and the enlargement, for increasing travel constraint of the enlargement area, thereby offering resistance to mine roof strata settling. As to the circumferential enlargement of the cable bolt, this is produced either through the inclusion of one or more cylindrical members, disposed on the king wire of the cable length, or an internally serrated cylindrical member position upon the cable length and constructed to grip the cable length in an increasing manner as the pressure bubble is produced. The method inherent in the invention, broadly stated, is to supply cable bolt anchoring structure in a mine roof, wherein dilation of the roof, as produced through settling of roof strata, is constrained through controlled descent as is regulated through the generation of a pressure bubble, i.e. by the radial elastic pressure, exerted circumferentially about a cylindrically enlarged portion of the cable bolt of the structure, by a tubular member expanded elastically thereabout and secured relative to a mine roof reaction plate, as by torquing nut structure or otherwise. OBJECTS Accordingly, the principal object of the present invention is to provide new and improved cable bolt structure and related components. A further object of the invention is to provide a cable bolt installation having a cable bolt constructed in such manner that the same has an enlargement capable of producing an elastic radial expansion within a tubular member employed, whereby to rely upon the radial compression of such tubular member against the periphery of the cable bolt enlargement to produce a dynamic-control resistance relative to relative motion between the cable bolt and the tubular member employed. A further object is to provide an improved cable bolt structure wherein the cable length constituting a principal portion of the structure includes a king wire, multiple strands wrapped about said king wire, and one or more hardened cylindrical elements disposed along said king wire for expanding outwardly the strands immediately adjacent the cylinders, thereby permitting said strands to coact in interference fit relationship with a tubular member so as to radially expand the tubular member in its elastic range, this for producing the compressive forces needed to supply the dynamic frictional resistance characteristic desired relative to the cable bolt and its tubular member. An additional object is to provide a cable bolt member having an enlargement taking the form of a cylindrical member that grips the peripheral strands of the bolt length, a side wall of the cylindrical member being slit to provide for structural circumferential compression without chancing plastic deformation of such cylindrical member. A further object is to provide a method for achieving ground control in mine roof strata, this by supplying a dynamic resistance characteristic which in effect is spring-loaded by virtue of the elastic expansion of a supplied tubular member relative to the enlargement of the cable bolt with which the later cooperates.
	abstract	This invention generally concerns robotic systems and is specifically concerned with an improved apparatus and method for inspecting nuclear reactor components in limited access areas, such as, the core annulus, core spray and feedwater sparger regions of a nuclear reactor. This invention includes an apparatus for remotely operating and positioning at least one inspection device for inspecting at least one component in an annulus region of a reactor pressure vessel of a nuclear power plant. The apparatus includes a track, a braking system and a frame assembly which has a frame movably connected to the track, at least one mast assembly and at least one mast positioning assembly. The at least one inspection device is attached to the at least one mast assembly. In certain embodiments, the at least one mast assembly includes a mast that is capable of becoming rigidly stable in both an extended tube form and a retracted rolled form.
	summary
	abstract	Disclosed are methods and apparatus for classifying defects based on X-ray spectrum obtained from the defects. In general terms, the present invention provides pattern recognition techniques for accurately and efficiently classifying a defect based on an X-ray spectrum obtained from such defect and its surrounding substrate and structures, no matter the complexity of such substrate and structures. A pattern recognition technique generally includes training a pattern recognition process to recognize particular types of X-ray spectrum obtained from specimens as belonging to a particular defect type or other specific characteristic of a specimen. Once a pattern recognition process is set up to recognize or classify particular X-ray spectrum, the pattern recognition process can then be utilized to automatically classify specimens as having a specific characteristic or defect type.
051065720	claims	1. A device for the centering and fixation of a cluster guide flange of a core plate of a nuclear reactor, extending parallel to one another in horizontal planes with a predetermined spacing, including at least two axial spindles for guiding said flange with respect to said core plate, said spindles being diametrically opposite and rigidly connected to said core plate or to said flange in order to engage in a housing in alignment formed in said flange or in said core plate respectively, and an assembly of generally cylindrical self-locking shoes having a first, planar face applied against said core plate and a second, opposite face which is inclined to the horizontal, said shoes being adapted for sliding with a clearance within bores formed in said flange in order to be pressed against a surface of said core plate, said shoes being each associated with a position control mechanism, carried by said flange and exerting on the shoes a force having a transverse component which is predetermined so as to oppose lateral displacement of said flange with respect to said core plate and to eliminate lateral play between said shoe and said flange. 2. A device according to claim 1, wherein said control mechanism associated with each shoe is constituted by a push-piece engaged in a bore of said shoe and having a convex face bearing on said inclined face of the shoe, said push-piece being extended beyond a bore in said flange on the side opposite said core plate by an elongated stem extending along an axis of a sleeve and having an inner screw thread at an end of said sleeve for screwing on a hollow calibration bushing through which said stem extends freely and exerts a vertical force on said stem via a spring cartridge having a first end bearing against said bushing and a second end bearing on a washer through which said stem extends and which is in abutment against a shoulder of said stem. 3. A device according to claim 2, wherein said spring cartridge comprise a stack of conical washers mounted between said washer and a complementary washer freely sliding inside the sleeve, parallel to the stem axis, under the effect of screwing of said bushing on said inner screw thread of said sleeve. 4. A device according to claim 2 or 3, wherein said threaded sleeve includes at its lower end a hollow end-piece through which extends said stem and an end of which engages in part in said bore of said flange and is then secured against movement in position with respect to said flange by securing means. 5. A device according to claim 2, wherein said elongated steam is provided at an upper end of said stem which extends beyond said calibration bushing with a transverse slit for identifying an axial orientation of said stem and therefore an axial orientation of said convex face of said push-piece with respect to the axis of said flange, and enabling by reaction on said inclined face of said shoe, relative adjustment of said push-piece and therefore of said flange connected therewith with respect to said core plate. 6. A device according to claim 1, wherein each shoe has a configuration of a clevis having two parallel arms disposed on either side of a central plane rib extending said push-piece downwardly, said clevis and said rib being connected by a transverse peg carried by said arms of said clevis and engaging with clearance in a hole of said rib so as to permit axial and radial displacement of said push-piece with respect to said shoe when there is a blockage of said flange with respect to said core plate. 7. A device according to claim 1, wherein each shoe includes a retracted stepped collar cooperating with a bearing surface of a same profile formed in a bottom of said bore of said flange. 8. A device according to claim 1, wherein said shoe has a first surface coating providing a face of said shoe which is in contact with said core plate with a coefficient of friction higher than a coefficient of friction provided by a second surface coating carried by said push-piece, the inner surface of said bore of said flange receiving said shoe, as well as said inclined face and said convex face of said shoe and of said push-piece. 9. A device according to claim 8, wherein said first coating is of "Stellite" and said second coating is chromium.
	claims	1. A process for manufacturing (U,Pu)O 2 mixed oxide nuclear fuel pellets, comprising the steps of: dosing and first blending (1) PuO 2 with a first portion of UO 2 powders and/or fuel manufacturing scrap, to form a first blend; micronizing (2) and forced sieving (3) the first blend, to form a conditioned first blend; selecting non-free-flowing UO 2 as a second portion of UO 2 ; mechanically granulating ( 29 ) the second portion of UO 2 so as to form granulated free-flowing UO 2 , additionally dosing and second blending (4) the conditioned first blend, the granulated free-flowing UO 2 and possibly scrap; adding and blending lubricants and/or poreformers (5), separately or in combination with the second blending step (4); pelletizing (6) the second blend; and sintering (7) the pellets thus formed, wherein said granulating step further comprises the steps of: compressing ( 30 ) non free-flowing UO 2 to form tablets; crushing ( 31 ) the tablets, until a free-flowing crushed material has been formed; and using at least one portion of this free-flowing crushed material for said second blending operation (4). 2. The process as claimed in claim 1 , further comprising the step of carrying out the compressing step at a pressure of between 40 and 200 MPa. claim 1 3. The process as claimed in claim 1 , characterized in that a jaw crusher or a roll mill is used for the crushing step ( 31 ). claim 1 4. The process as claimed in claim 1 , characterized in that it furthermore comprises particle size selection by sieving ( 32 ) of the granulated UO 2 before it is used. claim 1 5. The process as claimed in claim 4 , characterized in that the granulated UO 2 is separated, by the sieving ( 32 ), into at least two fractions of different particle sizes, the finest fraction possibly being introduced into the aforementioned first blending operation (1) whereas the other fraction is incorporated into the second blending operation (4). claim 4 6. The process as claimed in claim 1 , characterized in that it comprises, in order to carry out said granulation of the non-free-flowing UO 2 , an operation to force the latter through a screen or sieve, the amount of additive(s), the mesh size of the screen or sieve and the pressure exerted on the powder all being adjusted so as to form granules having the appropriate properties. claim 1 7. The process as claimed in claim 1 , characterized in that, for said granulation of the non-free-flowing UO 2 , a lubricant is added to it. claim 1 8. The process as claimed in claim 1 , characterized in that, for said granulation of the non-free-flowing UO 2 , a binder is added to it. claim 1 9. The process as claimed in claim 1 , characterized in that the sintering (7) of the fuel pellets in an atmosphere of argon and hydrogen is carried out at a temperature between 1600 and 1760xc2x0 C., the argon possibly being replaced with nitrogen. claim 1 10. The process as claimed in claim 1 , characterized in that, during the sintering (7), the oxygen partial pressure is adjusted, preferably by adjusting the H 2 /H 2 O ratio in the flushing gas, in order to improve the interdiffusion of the PuO 2 and UO 2 oxides. claim 1

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