Split (2)

train · 33.5k rows

patent_number stringlengths 0 9	section stringclasses 4 values	raw_text stringlengths 0 954k
	description	1. Field of the Invention Example embodiment(s) are related in general to systems for aligning and handling fuel rods and water rods within a nuclear fuel bundle. 2. Description of the Related Art A reactor core of a nuclear reactor plant such as boiling water reactor (BWR) or pressurized water reactor (PWR) has several hundred individual fuel bundles of fuel rods (BWR) or groups of fuel rods (PWR). During a planned plant outage for the BWR, selected irradiated fuel bundles are removed from the reactor core at the nuclear power plant and placed in a spent fuel pool for inspection and possible reconstitution of the bundle and/or maintenance. For example, there may be leaking fuel bundle which necessitates removing the irradiated fuel bundle from the core, as it is desirable to service these bundles in the event of a broken fuel rod and/or damaged fuel spacer grid which may be causing the leak. Additionally, when the fuel bundle is removed from the core and placed in the spent fuel pool, it is desirable to manipulate the fuel bundle for inspection purposes in order to search for additional possible sources of damage or leaks, and/or to rotate the bundle for general maintenance and measurement. A typical fuel bundle for a BWR includes a plurality of fuel rods and centrally located water rods attached between an upper tie plate and a lower tie plate. For example, in FIG. 24A, there is shown a fuel bundle 15 for a BWR which includes a plurality of fuel rods 25 and one or more water rods (water rods obscured and which may or may not be centrally located within bundle 15), connected between an upper tie plate 30 and a lower tie plate 40. FIG. 24B shows the same fuel bundle 15 as it would look upon removal from the core and prior to removal of the channel 20 for inspection and maintenance. The bundle 15 includes a generally rectangular channel 20 which extends the length of fuel bundle 15 and surrounds the fuel rods, water rods and upper and lower tie plates 30, 40. The channel 20 is an extruded alloy which encases the bundle 15. The fuel bundle 15 is typically delivered into the spent fuel pool via a fuel handling bridge (not shown) which is permanent machinery in reactor plants. The fuel handling bridge attaches to the upper tie plate bail (handle) 35 of the fuel bundle 15 to move the fuel bundle 15 from the core to the spent fuel pool. Typically the fuel bundle 15 shown in FIG. 24B is centered over a fuel prep machine (FPM-not shown), and a carriage of the FPM is raised to receive the fuel bundle 15. As is well known in the art, the FPM is attached to a wall of the spent fuel pool in a nuclear power plant. Once the channeled fueled bundle 15 is place within the FPM, the channel 20 and upper tie plate 30 are removed to expose the fuel rods 25 and the fuel bundle 15 upper end for inspection and/or maintenance purposes. Of note, with continued power operations of the reactor core with the irradiated fuel bundle 15, the fuel bundle 15 can be subjected to bow or twist. Twist/bow is caused by the amount of time the fuel bundle 15 has been in-service. In other words, the more the bundle 15 is used in an operating reactor core (i.e., the greater the exposure of the bundle in megawatt-days per short time (MWD/st), the greater the twist/bow potential. Accordingly, if the bundle 15 in the FPM exhibits twist or bow, it becomes substantially more difficult to remove selected fuel rods 25 in order to service/inspect the fuel bundle 15. A fuel bundle exhibits twist and bow due to the growth of individual fuel rods over time and exposure within the core. In an example, a fuel bundle for a BWR is typically held together with a plurality of tie rods. The lower end plugs of the fuel rod screw into the lower tie plate 40, and the upper tie plate 30 slides in place over the fuel rods 25, water rods and tie rods. The upper end plug of the tie rods are threaded and receive nuts which secures the fuel bundle 15 together. As the fuel rods 25 grow due to irradiation, the fuel rods 25 have little room to expand as they are sandwiched between the upper tie plate (UTP) 30 and lower tie plate (LTP) 40. The fuel rods do not all grow exactly the same amount, resulting in an uneven growth; this causes portions of the fuel bundle 15 to lengthen more than other areas within the bundle 15, producing what's known as bow and twist. Most fuel bundle designs in BWRs (such as the fuel bundle 15) and PWRs include a plurality of fuel spacers 80, also referred to as spacer grids, which are axially spaced along the length of the fuel bundle 15. A typical fuel spacer 80 or spacer grid includes a plurality of cells or openings which accommodate the fuel rods and water rods there through. These fuel spacers 80 are generally not robust in construction, and can be damaged during routine in-service fuel inspections while removing and installing full and part-length fuel rods and water rods in the bundle within the spent fuel pool. The damage caused to the fuel spacers 80 could go unnoticed, and could cause additional damage to individual fuel rods 25 if a reconstituted fuel bundle (such as fuel bundle 15) is returned to power operations within the core. Accordingly, during removal and installation of the fuel rods 25 in a given irradiated fuel bundle 15 within the spent fuel pool, there is a substantial probability for fuel bundle component damage, either to the fuel rod itself, the spacers, the water rods or end plugs of fuel rods, which can occur during the in-service maintenance of the fuel rods within the spent fuel pool. Further, as the removed fuel bundle 15 within the spent fuel pool is completely submerged, most inspections are done remotely and maintenance or repair is done by operators standing well above the fuel bundle 15, while utilizing a remote camera system and length handling poles with implements at ends thereon. The handling poles are inserted down through the fuel bundle 15 to remove/install selected fuel rods. With the upper tie plate 30, the channel clip (not shown) and the channel 20 removed, workers typically utilize up to a 30-foot handling pole to perform maintenance, installation and/or removal of fuel rods 25. Particularly in the case of part-length fuel rods, which in some case are substantially shorter than full-length fuel rods, only the skill and experience of the handler of the handling pole ensures that a part-length rod can be safely extracted (or installed) without causing damage to the fuel spacers 80 or adjacent fuel rods 25. This is true even with the use of remote cameras positioned down in the spent fuel pool for monitoring the maintenance procedure. Accordingly, conventional procedures for retrieving/installing a part-length fuel rod are time consuming if not impossible, cumbersome and must rely on the experience and skill of the operator manipulating the handling pole to avoid damaging a fuel spacer 80 or adjacent fuel rod 25. As fuel bundle designs are becoming even more complex, this inadvertent damage to the fuel spacers 80 and/or fuel rods 25 is even more likely without an adequate alignment and handling system. An example embodiment is directed to a system in a nuclear power plant for aligning a nuclear fuel bundle and handling selected fuel rods and/or water rods within the fuel bundle, where the fuel bundle resides in a spent fuel pool within the plant. The fuel bundle includes one or more water rods and a plurality of fuel rods including full-length fuel rods and part-length fuel rods extending vertically within the bundle through a plurality of axially spaced fuel spacers provided between a top end and bottom end of the fuel bundle, each fuel spacer including a plurality of individual cells accommodating corresponding fuel rods and water rods. The system includes a fuel prep machine (FPM) in the spent fuel pool for supporting the fuel bundle thereon, a bundle alignment assembly attached to the fuel prep machine for aligning fuel rods within the fuel bundle to remove any twist or bow within the fuel bundle, a rod grapple tool to extract selected part-length rods from the fuel bundle, and a fuel rod guide block slidable onto the top end of the fuel bundle for protecting an uppermost fuel spacer of the fuel bundle and aligning fuel rods within individual cells of all the fuel spacers in the fuel bundle. Another example embodiment is directed to a system of a reactor plant for removing bow and twist within a nuclear fuel bundle to permit inspection and replacement of one or more fuel rods or water rods within the fuel bundle, where the fuel bundle has been removed from a reactor core to a spent fuel pool within the plant. The system includes a fuel prep machine (FPM) in the spent fuel pool for supporting the fuel bundle thereon, and a bundle alignment system attached to the fuel prep machine for aligning fuel rods within the fuel bundle to remove any bow or twist within the fuel bundle. Another example embodiment is directed to a fuel rod alignment system for a fuel bundle residing in a spent fuel pool within the plant. The fuel bundle includes one or more water rods and a plurality of fuel rods including full-length rods and part-length rods extending vertically within the bundle through a plurality of axially spaced fuel spacers provided between a top end and a bottom end of the fuel bundle, each fuel spacer including a plurality of individual cells accommodating corresponding fuel rods and water rods. The system includes a fuel prep machine in the spent fuel pool for supporting the fuel bundle thereon, and a fuel rod guide block slidable onto the top end of the fuel bundle for protecting an uppermost fuel spacer of the fuel bundle and aligning fuel rods within individual cells of all the fuel spacers in the fuel bundle. Another example embodiment is directed to a system for removing a part-length fuel rod from a fuel bundle, where the fuel bundle resides in a spent fuel pool of a nuclear reactor plant. The system includes a fuel prep machine in the spent fuel pool for supporting the fuel bundle thereon, and a rod grapple tool having a first end handled by an operator above the fuel pool in the plant and a second end inserted at a top end of the fuel bundle on the fuel prep machine to retrieve the part-length fuel rod within the bundle. The second end has a protective, removable guide pin which prevents the rod grapple tool from damaging the fuel bundle as the rod grapple tool is inserted into the bundle. The system includes a guide pin retrieval tool for, when the rod grapple tool has been inserted into the fuel bundle so that the guide pin and gripper are in position over the part-length fuel rod to be extracted, removing the guide pin to permit the gripper of the rod grapple tool to be attached to an upper end plug of the part-length fuel rod to extract the part-length fuel rod from the bundle. As will be described in more detail below, an example embodiment is directed to a system for aligning and handling selected fuel rods within a fuel bundle of a nuclear reactor which facilitates the ability of handlers to remove and install fuel rods without damaging the fuel spacers or adjacent fuel rods. The example system may provide a straight-line path to facilitate the extraction of fuel rods including part-length fuel rods without merely relying on the skill of the handler to insure that the fuel rod is removed without damaging adjacent fuel rods or fuel spacers. The example system may thus enable the fuel rods, spacers or spacer grids, water rods and end plugs to be protected during maintenance and/or inspection procedures within the spent fuel pool. FIG. 1 is a side view of a system 1000 for aligning and handling selected fuel rods within a fuel bundle in accordance with an example embodiment. In FIG. 1, the fuel bundle 150 is supported by a fuel prep machine (FPM) 110. The FPM 110 is attached to a wall 105 of a spent fuel pool 103 within a nuclear reactor. The fuel bundle 150 is shown with its upper tie plate 30 and channel 20 removed, as this procedure is done once the fuel bundle 150 is lowered into the fuel prep machine 110. In this example, the fuel bundle 150 is for a BWR and has a 10×10 fuel rod matrix (10 rows by 10 columns of full-length and partial-length full rods), with a pair of centrally located circular water rods 170. However, fuel bundle 150 can have a configuration other than a 10×10 fuel rod matrix (9×9, 12×12, etc.), and a different number of water rods of different shapes and sizes, that may or may not be centrally located within the fuel bundle. System 1000 includes a bundle alignment assembly 200 attachable to the fuel prep machine 110. The bundle alignment assembly 200 is provided for aligning fuel rods and water rods within the fuel bundle 150 to remove any twist or bow within the fuel bundle 150 and to provide a straight-line path for fuel rod installation and/or removal. As will be seen in more detail below, the bundle alignment assembly 200 includes a series of alignment stations 210. Each alignment station 210 includes a plurality of rotatable pre-formed stainless steel blades and rigid stainless steel blades. In general, the bundle alignment assembly 200 is lowered into position onto the fuel prep machine 110 and held in place by mechanical means. The fuel bundle 150 is then placed into the fuel prep machine (FPM) 110 for inspection. When manually actuating the bundle alignment assembly 200 by means of a handling pole, the rotatable pre-formed stainless steel blades and the rigid stainless steel blades are rotated together into the fuel bundle 150, creating a protective grid above each fuel spacer 180 while also capturing each individual fuel rod in the forward half of the nuclear fuel bundle 150. One possible result of using the bundle alignment assembly 200 is to ensure that an in-service (i.e., irradiated) nuclear fuel bundle such as fuel bundle 150 has any twist and/or bow removed there from, a condition normally caused by the harsh environment within reactor vessels. The assembly 200 thus may provide a straight path for the removal and installation of individual fuel rods or water rods, while protecting the fuel spacers 180 from damage. System 1000 further includes fuel rod guide block 300 slidable onto the top end of the fuel bundle 150 for protecting an uppermost spacer from damage, shown as spacer 180A in FIG. 1. The fuel rod guide block 300 protects the uppermost spacer 180A of the fuel bundle 150 from damage while inserting fuel rods by physically protecting the upper side of the spacer 180A. The fuel rod guide block 300 also enables aligning of fuel rods within individual cells of all the fuel spacers 180 in the fuel bundle 150. Additionally, the fuel rod guide block 300 provides a lead-in to initially start a fuel rod into the fuel bundle 150 with desired proper alignment. Further, the rod guide block 300 provides an obvious visual indication as to where a fuel rod needs to be inserted into the fuel bundle 150. This can enable less experienced handlers to perform fuel rod removal and insert procedures without requiring the skill of and experience of the seasoned handler, since the fuel rod guide block 300 helps to properly align each of the fuel rods of the fuel bundle 150 in the vertical direction. As will be shown in further detail hereafter in FIG. 10, the fuel rod guide block 300 includes two horizontally-oriented, spaced (upper and lower) stainless steel plates separated by a plurality of vertically-arranged stainless steel tubes. Each of the plates has a plurality of openings which align with the locations of the fuel rods and water rods within the bundle 150. The fuel rod guide block 300 is held together by two vertically-oriented side plates attached by suitable fasteners to each of the upper and lower plate. A bail (handle) with restricted movement is attached to the fuel rod guide block 300 for the purpose of lowering it onto the fuel bundle 150 that is supported on the FPM 110, prior to in-service fuel inspections. Thus, the fuel rod guide block 300 is designed to slide onto the top of the nuclear fuel bundle 150 positioned in the FPM 110. As will be described in further detail below (FIGS. 11A and 11B), once installed, the fuel rod guide block 300 is limited to its downward travel into bundle 150 by creating a restricted fit between the water rods and tapered central openings in the upper plate of the fuel rod guide block 300 which are aligned with the water rods. The fuel rod guide block 300 comes to rest onto tapered sections of a water rod transition area. Although system 1000 is shown with both the bundle alignment assembly 200 and rod guide block 300 included, each can be used independently without the other for inspection and/or maintenance of an irradiated fuel bundle 150. In an example, fuel bundle 150 can be an irradiated fuel bundle that has been removed from the BWR core, a previously used bundle 150 that is stored within the spent fuel pool of the plant, a new fuel bundle 150 that has been stored within the spent fuel pool of the plant while awaiting placement within the reactor's core as a reload, a fuel bundle having been removed from an on-site new fuel storage fault for placement in the fuel pool, and/or a fuel bundle from a fixed or movable dry storage cask for placement into the fuel pool). In another example embodiment, the FPM 110 and only bundle alignment assembly 200 are used together for supporting a fuel bundle 150 and aligning the fuel rods and water rods of the bundle for inspection and/or rod replacement purposes. For any irradiated bundle 150 exhibiting twist and or bow, the FPM 110 and bundle alignment assembly 200 may thus constitute a system for removing the twist/bow within a fuel bundle to permit inspection and possible replacement of one or more fuel rods or water rods therein within the spent fuel pool of the plant. In this alternative embodiment, the rod guide block 300 may not necessarily be installed. In the event that an irradiated fuel bundle 150 exhibits no twist or bow, the bundle alignment assembly 200 does not need to be installed, only the rod guide block 300 is installed on the top of the bundle 150 above the uppermost spacer 180A. In this alternative embodiment, the rod guide block 300 with FPM 110 can represent a separate fuel bundle handling system, in which the FPM 110 supports fuel bundle 150 thereon and the rod guide block 300, when installed on the top end of the bundle 150, aligns each of the fuel rods 155 and water rods 170 of the fuel bundle 150 in the vertical direction. Referring again to FIG. 1, the system 1000 also includes a rod grapple tool 400. In particular, rod grapple tool 400 is utilized by a handler for the removal of fuel rods, such as certain tie rods and/or the shorter part-length fuel rods which are deeper within the fuel bundle 150. A different, pre-existing rod grapple tool may be used for the removal and/or reinsertion of standard full length fuel rods and certain tie rods, as the upper end plugs of the standard full length fuel rods and tie rods may be designed differently than that of the upper end plug of the part-length fuel rod. The rod grapple tool 400 is designed so as to mimic the dimensions of individual fuel rods. This allows the rod grapple tool 400 to safely pass through the fuel spacers 180 without causing component damage. As will be seen in more detail below (FIG. 15B, for example), the rod grapple tool 400 includes a gripper (also referred to as a rod grapple) at the end of the tool 400 that is inserted into the fuel bundle 150 for extracting a part-length fuel rod. For insertion of the rod grapple tool 400 into the bundle 150, the rod grapple tool 400 includes a removable guide pin (shown in more detail in FIGS. 15A and 15B). The guide pin is inserted into the gripper and is generally tapered to a rounded pin end. Since the gripper has a blunt end, the guide pin is provided to prevent damage to the fuel spacers 180 as the rod grapple tool 400 is inserted into the fuel bundle 150. Once the rod grapple tool 400 has been fitted with the guide pin, inserted into the fuel bundle 150 and positioned at a given axial location within the fuel bundle 150 above a part-length fuel rod to be extracted, a pin retrieval tool 500 is utilized to remove the guide pin from the end of the grapple tool 400. The pin retrieval tool 500 is shown in more detail hereafter and is attached at the end of a separate handling pole 502 for insertion down into the fuel pool to retrieve the guide pin from the rod grapple tool 400 end. Accordingly, the rod grapple tool 400 and pin retrieval tool 500 may comprise a separate system for removing a part-length rod from a fuel bundle, independent of the bundle alignment assembly 200 and rod guide block 300 of the system shown in FIG. 1. Further, the rod guide block 300, rod grapple tool 400 and guide pin retrieval tool may comprise a separate system for removing part-length rods for the fuel bundle 150, independent of the bundle alignment assembly 200. In general to remove a part-length rod from fuel bundle 150, the tapered, rounded guide pin is inserted in the end of the gripper so that only the tapered end of the guide pin extends from a lower housing of the rod grapple tool 400. The gripper is designed to be attached to an upper end plug of a part-length fuel rod for rod extraction. Once attached, the gripper is retracted into the lower housing so that the lower housing of tool mates with a shoulder of the end plug at the top of the part-length rod, providing a smooth continuous surface between the part-length rod and the attached rod grapple tool 400. The guide pin thus creates a lead-in for the rod grapple tool 400 to pass through each fuel spacer 180. Once the rod grapple tool 400 is in position above a selected part-length fuel rod, the guide pin is removed using the pin retrieval tool 500 so that the gripper of tool 400 can be inserted over the partial length rod's end plug and engaged for fuel rod extraction. As to be described in more detail below (FIGS. 17A and 17B), the pin retrieval tool 500 includes a tongue with a mating bore that receives a mating portion of the guide pin. The pin retrieval tool 500 is fixed to the end of the handling pole 502 to allow for remote handling of the guide pin within the fuel bundle 150. The pin retrieval tool 500 thus provides a positive means of capturing the guide pin 435 for repetitive use. FIGS. 2A through 2C illustrate an example fuel prep machine 110 used in system 1000 in accordance with an example embodiment. Many nuclear power plants employ fuel prep machines 110 in the spent fuel pool of the plant to support an irradiated fuel bundle 150, thus a detailed explanation is omitted for purposes of clarity. As shown in FIGS. 2A to 2C, the fuel prep machine (FPM) 110 generally includes a stanchion 114 extending from an FPM platform 115 down into the spent fuel pool of the plant. The FPM 110 includes a carriage 120 which slides up and down as needed on rails 116 formed on the stanchion 114. The carriage 120 includes an upper rotating fixture 122 and a lower rotating fixture 124 which permit rotational movement of the fuel bundle 150 therein. The FPM 110 is a permanent fixture in the spent fuel pool 103 and is mounted on one of the walls 105 of the spent fuel pool 103, as is known. The FPM platform 115 is the only portion of the FPM 110 that is above water and includes a safety handrail 117. A fuel bundle (such as bundle 150) is delivered to the FPM 110 via a fuel handling bridge (not shown, this is a permanent fixture in a reactor plant). Once in place over the carriage 120, the carriage 120 is raised to receive the fuel bundle 150. The fuel bundle 150 may be rotated in either direction up to 360 degrees as desired for inspection and/or maintenance purposes via upper and lower rotating fixtures 122, 124. FIG. 3A is a front view of the bundle alignment assembly 200 and FIG. 3B is a side view of assembly 200. FIG. 3C is an enlargement of detail A in FIG. 3B. Referring to FIGS. 3A and 3B, assembly 200 includes a plurality of axially-spaced alignment stations 210 mounted to a mounting frame 205 which is attached to the upper and lower rotating fixtures 122, 124 of the fuel prep carriage 120 on the FPM 110 as will be shown hereafter. The assembly 200 includes a bail 202 which enables it to be lowered onto and removed from the FPM 110. Each alignment station 210 includes a support plate 206 with a plurality of alignment blade bundles 220 mounted thereon. As best shown in FIG. 3C, the support plate 206 is mounted to a cross member 204 affixed to the mounting frame 205 and also to the mounting frame 205 by mechanical fastening means 214 (such as nut-screw-washer assemblies). Each alignment station 210 includes a plurality of alignment blade bundles 220 mounted thereon. In FIG. 3A, these are shown as blade bundles 220A, 220B and 220C. As will be seen in further detail below, the alignment blades of these bundles are rotated to align fuel rods and water rods in the front half of the fuel bundle 150 (due to clearance constraints of the FPM 110, half the bundle 150 is aligned at a time for inspection and/or rod removal/installation in that half), then the bundle 150 is rotated to inspect and/or service the other half of the same bundle. FIG. 4 is a partial side view of system 1000 in the vicinity of the lower rotating fixture 124 in order to show the connection of the bundle alignment assembly 200 to the fuel prep machine 110; FIGS. 5 and 6 are partial perspective views of the system 1000 to show the attachment of the upper mount block 208 to the upper rotating fixture 122. Referring to FIGS. 4-6, in order to mount the bundle alignment assembly 200, an upper mounting bracket 218 and a lower mounting 216 are installed on the upper and lower rotating fixtures 122 and 124. These will capture the mating surfaces of the bundle alignment assembly 200. As shown best in FIG. 4, a lower mounting bracket 216 is attached to the lower rotating fixture 124. The lower mounting bracket 216 is configured to receive an alignment pin 212 which is connected to the bottom of the mounting frame 205 of the bundle alignment assembly 200. The upper mounting bracket 218 is attached to the upper rotating fixture 122. Each upper mounting bracket 218 includes a feature which has a threaded cavity 217 therein. The brackets 218 are adapted to receive spring loaded pins 219 which screw therein to connect the upper mount blocks 208 at the upper end of the bundle alignment assembly 200 to the upper mounting brackets 218 of the upper rotating fixture 122. As best shown in FIG. 6, this secures the bundle alignment assembly 200 to the carriage 120 of the fuel prep machine 110, with the spring loaded pins 219 inserted into the threaded cavities 217 of the upper mounting brackets 218. Of note, FIG. 5 provides a clearer view of the internal arrangement of fuel rods, comprising full-length fuel rods 155 and part-length fuel rods 160, and water rods 170 within fuel bundle 150. For purposes of clarity, a number of full and part-length rods 155, 160 have been removed so that the water rods 170 and other part-length rods 160 can be seen. Also illustrated are the upper end plugs 165 on the part-length fuel rods 160. Further, the fuel spacer 180 with its individual cells may be seen in clearer detail. Accordingly, the bundle alignment assembly 200 is lowered into position via its bail 202 so that the lower alignment pins 212 are guided into the lower mounting brackets 216. The upper mounting blocks 208 are then positioned onto the upper mounting brackets 218 and the spring loaded pins 219 are engaged in the upper mounting brackets 218 to secure the bundle alignment assembly 200 into place. FIG. 7A is a perspective view of an alignment station 210 showing alignment blade bundles 220 in a neutral or disengaged position. Each alignment station 210 includes a plurality of blade bundles 220. As shown in FIG. 7A (as well as in FIG. 3A), three (3) alignment blade bundles 220A, 220B and 220C are mounted on a generally C-shaped support plate 206. Each blade bundle 220 includes a plurality of stainless steel blades 222. However, blades 222 can be formed of other metals, metal alloys or materials having high thermal resistance properties and/or high coefficients of thermal conductivity, such as inconel, high temperature polymers (plastics) and ceramics. Some of the individual blades 222 are shorter (shown as 222′) than others in a given blade bundle 220 so as to create a grid 230 around a portion of the fuel bundle 220 (in this example, half of bundle 150) when the blade bundles 220 are rotated into an engaged position. In FIG. 7A, the individual blade bundles 220 are shown in a neutral or disengaged position. They are movable into an engaged position by corresponding activation handles 226. FIG. 7B is a perspective view of the alignment station 210 showing the blade bundles 220 in an engaged position. As shown in FIG. 7B, the blade bundles 220A, 220B and 220C can be rotated into the fuel bundle 150 by actuating the activation handle 226. A hook used on the standard handling pole is used to actuate the activation handles 226 sequentially so as to first rotate the blade bundle 220B, then bundles 220A and 220C into the fuel bundle 150. FIG. 7C is a top view of the alignment station 210 with the blade bundles 220 in an engaged position to illustrate the grid 230 that is created for alignment of fuel rods 155/160 and water rods 170 within the fuel bundle 150. FIG. 7C also better illustrates the use of shorter blades 222′ to form grid 230. Alignment blade bundle 220B is rotatable in a first plane, and the other two blade bundles 220A and 220 C are rotated in a second plane above blade bundle 220B so as to form the grid 230 around groups of fuel rods 155, 160 and water rods 170. The top view of FIG. 7C shows how the grid 230 is created with an interior center space to provide an opening for the water rods 170. This grid 230 in the example of FIG. 7C thus aligns approximately half the fuel rods 155/160 in fuel bundle 150, which for an example 10×10 fuel matrix are forty-six (46) fuel rods and one (1) water rod. Half of the fuel rods 155/160 with one water rod 170 in bundle 150 are aligned at a time due to tolerance constraints of the FPM 110. The bundle 150 can simply be rotated within carriage 120 to permit rods 155/160/170 in the other half of the fuel bundle 150 to be aligned. Of note, the bundle 150 is straightened once the blade bundles 220A-C are inserted from one side. Selected fuel rods 155, 160 on the other side of the bundle 150 may still have bow or twist, but the overall bundle 150 profile will be straight in the axial direction. For each alignment station 210, the protective grid 230 formed by the alignment blade bundles 220 vertically aligns the fuel rods 155/160 and water rods 170 above each of the fuel spacers 180 in the bundle 150, as shown in FIG. 1 for example. Of course, alignment stations 210 can be located below the spacers 180 so that the grid 230 formed by blade bundles 220 vertically aligns the fuel rods 155/160 and water rods 170 below each of the fuel spacers 180. If desired, alignment stations 210 can be attached just above and below spacers 180 to form the grids 230 that align the fuel rods 155/160 and water rods 170 above and below each of the fuel spacers 180 in the bundle 150. In an alternative construction, the blade bundles 220 can be rotated horizontally to an engaged position such that individual blades 222 rotate independent of one another. In this embodiment, selected blades 222 may be removed from selected blade bundles 220 to align a particular portion of fuel rods 155/160 in the bundle 150. Different combinations of blades 222 in each of the blade bundles 220 of an alignment station 210 can thus be rotatable to align one or more of a half-section of the bundle 150, a quarter-section of the bundle 150 and an eighth section of the bundle 150, for example. It would be evident to one skilled in the art to include additional blades 222 with varying or different lengths to accommodate different fuel rod matrix configurations other than 10×10, such as fuel bundles having 9×9 fuel rod matrices or larger fuel bundles such as the developing 17×17 fuel rod groups for pressurized water reactors (PWRs). FIG. 8A is a perspective view of an alignment blade bundle 220 and FIG. 8B is an exploded view of FIG. 8A illustrating the constituent parts of the alignment blade bundle 220. Referring to FIGS. 8A and 8B, an alignment blade bundle 220 (each of the three alignment blade bundles have similar parts) includes a base plate 228 which has two side plates 232 connected thereto via a plurality of fasteners 234 such as the screws which are secured within threaded bores 235. The activation handle 226 is connected to one side of shaft 238 so as to be in rotational engagement with a shaft 238. The shaft 238 extends through a bearing/washer assembly shown generally at 239 and through a pair of pivot blocks 240. The blades 222 are attached to a blade holder 236 which is affixed to the top of the pivot blocks 240 via a series of fasteners 241 received in corresponding threaded bores 242 in the pivot blocks 240. Each blade bundle 220 also includes a fixed stainless steel blade 237 attached to blade holder 236. The purpose of fixed blade 237 is to provide a rigid point to begin fuel rod alignment. A limit stop 243 is provided beneath the blade holder 236 so as to limit rotational travel of the blades 222 to no more than 90 degrees from vertical. The blade bundle 220 is fixedly secured to the support plate 206 with a spring stop bolt 244 which compresses a spring 246 as it is tightened into a threaded bore 248 of the base plate 228. This allows a blade bundle 220 to be quickly removed from and/or reattached to support plate 206. An inspection tooling lug 250 is also attached to the base plate 228 via suitable fasteners 252 to permit an inspection tooling pole (not shown) to be attached thereon. FIG. 9 is a partial perspective view of the system 1000 illustrating the rod guide block 300 placed over the fuel bundle 150. Referring to FIG. 9, the fuel rod guide block 300 has a bail 302 which is attached to a standard handling pole 304 to be lowered down into the spent fuel pool and place just below the upper end plugs of the full length fuel rods 155 and the tops of the water rods 170 at the top end of bundle 150. As previously indicated, in the event that the irradiated fuel bundle 150 exhibits no twist or bow, only the rod guide block 300 need to be installed on top of the bundle 150 above the uppermost spacer 180A. The fuel rod guide block 300 when in place protects the uppermost spacer 180A from damage as fuel rods are inserted therein and also provides an aligned lead-in to initially start a replacement fuel rod (full-length fuel rod 155 or part-length rod 160) into the fuel bundle 150 with the desired proper alignment. Thus, the rod guide block 300 acts as both a shield (physically protecting spacer 180A) and a visual aid to show a handler where a fuel rod needs to be inserted into the fuel bundle 150 by providing a clear visual indication due to the structure and arrangement of an upper plate 305 of fuel rod guide block 300. Accordingly, less experienced handlers can perform fuel rod removal and insertion procedures without requiring the skill and experience of the seasoned handler, since the structure of the fuel rod guide block 300 helps to properly and perfectly align each of the fuel rods 155/160 of the fuel bundle 150 in the vertical direction. FIG. 10 is an exploded view of the fuel rod guide block 300 to illustrate constituent parts in more detail. As previously described, the fuel rod guide block 300 is lowered onto the fuel bundle 150 via a standard handling pole 304. In an example, this can be a handling pole with a ½″-13 threaded stud that located on the lowest end of the pole 304, that's used to lower the guide block 300 over the fuel bundle 150. The threaded stud is received in the threaded bore 303 in bail 302 of the fuel rod guide block 300. The fuel rod guide block 300 further includes an upper plate 305, a lower plate 306, and a plurality of stainless steel vertical tubes 308 dimensioned so as to be able to receive a replacement fuel rod 155, 160 or a rod grapple tool 400 there through. A pair of side plates 310 attach to the upper plate 305 and lower plate 306 so as to secure the tubes 308, upper plate 305 and lower plate 306 together. The side plates 310 include a plurality of holes 319 to facilitate decontamination and cleaning of tubes 308 within the guide block 300. As shown in FIG. 10, each of the upper plate 305 and the lower plate 306 have a plurality of threaded bores 313 which are configured to receive a plurality of fasteners 314 to attach the side plates 310 to the side surfaces of the upper and lower plates 305, 306. As the example fuel bundle 150 has a 10×10 fuel rod matrix, 92 tubes 308 are employed (a space is provided in the center for the water rods 170), and each of the top and bottom plates 305 and 306 have 92 fuel rod openings 316 for fuel rods 155/160 or grapple tool 400 passage. Openings 316 align with the tubes 308 as shown. The upper plate 305 and lower plate 306 also include a pair of central openings 318 that align with the water rods 170 in the fuel bundle 150. Accordingly, openings 316 and 318 mirror the locations of fuel rods 155/160 and water rods 170 in fuel bundle 150 and align with the tubes 308. Thus, as the fuel rod guide block 300 is positioned onto and/or over the fuel rods 155/160 and water rods 170 of the fuel bundle 150, the fuel rods 155/160 and water rods 170 are properly realigned, eliminating any bow and/or twist that might be present within the bundle 150 (such as in a case where the fuel rod guide block 300 is not used with bundle alignment assembly 200). A bail attachment plate 320 is provided on either side of the tubes 308, between its corresponding side plate 310 and the tubes 308. Each bail attachment plate includes a projection 322 which extends through an opening 324 in its corresponding side plate 310. Each projection 322 has a centrally threaded bore 326 which is to receive a fastener 328 which secures each arm 329 of the bail 302 to its corresponding bail attachment plate 320, i.e., the fasteners 328 are captured by the threaded bores 326 to secure the bail 302 to the bail attachment plates 320. A bail stop 330 is provided on each outside surface of each side plate 310, providing a restricted movement mechanism so as to prevent the bail 302 from traveling too far. As shown in FIG. 10, the bail stop 330 is secured to the side plate 310 and bail attachment plate 320 with a plurality of fasteners 332 which are captured in threaded bores 333 within the bail attachment plate 320. FIGS. 11A and 11B are partial cutaway views of the fuel rod guide block to illustrate the placement of the fuel rod guide block 300 over the fuel bundle 150 and on top of the uppermost space 180A. The fuel rod guide block 300 in FIGS. 11A and 11B is shown with an area where the tubes 308 have been removed to illustrate how the water rods 170 interact with the guide block 300. As the fuel rod guide block 300 is lowered by the handling pole 304, the fuel rods (full-length fuel rods 155 since this is the top of bundle 150) and water rods 170 extend through the apertures 316, 318 as the fuel rod guide block 300 is lowered down into the bundle 150. Downward travel of the fuel rod guide block 300 is terminated due to tapers 172 (neck-down features) of the water rods 170. The openings 318 in the upper plate 305 for the water rods are also tapered as best shown at 307 in FIG. 11B. Thus, when the tapered openings 318 meet the tapers 172 of the water rods 170, the fuel rod guide block 300 downward travel is halted. Accordingly the tapered surfaces 172, 307 prevent the fuel rod guide block 300 from traveling any further in the downward direction. FIG. 12 illustrates a partial perspective view of the system 1000 with the fuel rod guide block 300 in place on fuel bundle 150. Once the fuel rod guide block 300 is in position, the handling pole 304 is removed by rotating it counter clockwise to remove its stud from the threaded opening 303 in the bail 302. After the handling pole 304 is released from the fuel rod guide block 300, the handling pole 304 is used to tap the bail 302 either backwards or forwards. The handling pole 304 is then stored in its normal ready position hanging from the safety handrail 117 of the FPM platform 115, for example. FIG. 12 thus illustrates the system with the fuel rod guide block 300 in place. FIGS. 13-16B describe the rod grapple tool 400 in further detail; reference should be made to these figures for the following discussion. The rod grapple tool 400 is shown generally in FIG. 13 from the vantage point of the FPM platform 115 looking down into the spent fuel pool below towards the fuel bundle 150, which is secured within the carriage 120 attached to the FPM 110. As previously noted, the fuel bundle 150 includes a plurality of part-length rods 160. The part-length fuel rods 160 may be different heights, known as upper part-length rods and lower part-length fuel rods. The rod grapple tool 400 is used to retrieve (or install) either the upper part-length fuel rods or the lower part-length rods 160 from the fuel bundle 150. A handler grabs the rod grapple tool 400 by a handle 402 to lower the rod grapple tool 400 into the fuel bundle 150, such as through one of the tubes 308 in the fuel rod guide block 300. The rod grapple tool 400 includes a push-pull handle 404. In an optional variation, the push-pull handle 404 can include indicator markings (shown generally at 403) that indicates when the rod grapple tooling is in the fully extended position and/or when it is in the fully closed position, this part of the operation will be explained in further detail hereafter. FIGS. 14A through 14D illustrate constituent parts of the part-length rod grapple tool 400 in more detail. As shown in FIGS. 14A and 14B, the part-length rod grapple tool 400 includes a push-pull handle 404 which is connected to an activation rod 408 via a plurality of fasteners 409 that are received in holes 411 in the push-pull handle 404 to be captured by threaded bores 410 in the activation rod 408. A top end of activation rod 408 is inserted up through a threaded sleeve 405 on which a threaded acme nut 407 rides, into the push-pull handle 404, where it is secured to the push-pull handle by fasteners 409 such as screws. As shown in FIGS. 14A and 14B, the activation rod 408 is assembled with Delrin bushings 412, spiral retaining ring 414 and spaced retaining rings 416 which secure the Delrin bushings 412 along the activation rod 408. The Delrin bushings 412 keep the activation rod 408 centered in an upper housing 418. The upper housing 418 has the handle 402 at one end and a connector 422 at another end for attaching to a connector 424 of a lower housing 430 of the grapple rod tool 400. As the fasteners 409 are not strong enough to counter the potential rotational torque due to unscrewing the part-length rod 160 from its lower tie plate 40, a key stock 413 is provided in a slot 406 of activation rod 408 to absorb this torque. As will be seen in further detail, the lower housing 430 contains an extendable gripper rod 431 (see dotted line to denote within the interior of lower housing 430 in FIG. 14A) which has a gripper 432 attached at a distal end thereon. The gripper rod 431 is attachable to the activation rod 408 within the connectors 422, 424 of upper and lower housings 418, 430, and can be extended via push-pull handle 404 to extend the attached gripper 432 outside of the lower housing 430 so as to retrieve a part-length rod 160. Referring to FIGS. 14C and 14D, the activation rod 408 has a machined flat end connector 426 which mates with a corresponding machine flat end connector 428 of the gripper rod 431 within the connector 424 of the lower housing 430. The machine flats on end connectors 426 and 428 keep the activation rod 408 and gripper rod 431 from rotating so as to allow the gripper 432 at the end of the gripper rod 431 to be pulled. The upper and lower housings 418 and 430 are joined at flat facing surfaces 423 and 425 by the use of suitable mechanical fasteners 427. Prior to connecting these housings 418 and 430 together, the activation rod 408 is connected to the gripper rod 431 via the end connectors 426 and 428, as best shown in FIG. 14D. In particular, a threaded screw 429 is captured through aligned bores in both end connectors 426 and 428 of their respective rods 408, 431. The connection between activation rod 408 and gripper rod 431 allows the gripper 432 which is attached at the distal end of gripper rod to be extendable from the end of the lower housing 430, and hence retracted within lower housing 430. Accordingly, the rod grapple tool 400 has an extended position and a retractable or closed position. FIGS. 15A and 15B illustrate the extended position of the rod grapple tool 400. The extended position is only used when loading or removing the guide pin 435 from gripper 432, as well as locking the gripper 432 of rod grapple tool 400 onto a partial-length rod 160 so as to extract it from the fuel bundle 150. To extend gripper 432, while a handler holds the handle 402, the handler rotates the acme threaded nut 407 counter-clockwise until it comes into contact with the push-pull handle 404. This causes the gripper 432 at the end of gripper rod 431 to be extended out from the end of lower housing 430. As shown best in FIG. 15B, the protective guide pin 435 is inserted into the gripper 432. The guide pin 435 has a tapered, generally rounded end 437 and includes a mating portion 436 thereon to be captured by the guide pin retrieval tool 500 for removing the guide pin 435 from the gripper 432. Once the rod grapple tool 400 is returned to its retracted position, the protective guide pin 435 remains in place and abuts the edge of lower housing 430 so as to create a flush, smooth surface 450. The rod grapple tool 400 is then inserted down through the fuel bundle 150 and spacers 180 to a position above a part-length rod 160 to be extracted. FIGS. 16A and 16B illustrate the closed position of the rod grapple tool 400. Here the guide pin 435 is shown installed as having a flush surface 450 with the end of the lower housing 430, with the gripper rod 431 and its gripper 432 retracted therein. This is the position for insertion of the rod grapple tube 400 down through the fuel rod guide block 300 into the bundle 150. The blunt end 433 of the gripper 432 is thus not exposed. While holding the handle 402, the threaded nut 407 is rotated clockwise. This will draw the gripper 432 up into the lower housing 430 such that the guide pin 435 mates flush with the lower housing 430 at surface 450. FIGS. 17A-22 illustrate the structure and function of the guide pin retrieval tool 500 in further detail. Once the rod grapple tool 400 is in position within the bundle 150 between a spacer 180 and a part-length rod 160, which is to be extracted, the guide pin 435 needs to be removed from the rod grapple tool 400. This is accomplished with the pin retrieval tool 500. FIG. 17A is a perspective view of guide pin retrieval tool 500, and FIG. 17B is an enlarged view of detail A in FIG. 17A. The pin retrieval tool 500 is positioned between the top of the part-length rod to be extracted and the fuel spacer 180 above the part-length rod 160. The pin retrieval tool 500 is attached to a handling pole 502, only a portion of which is shown in FIG. 17A. The lower portion of the handling tool 502 may be bent as shown to account for limitations in the access of open space of fuel prep machine 110. The pin retrieval tool 500 is attached at the end of the handling pole 502 and includes a horizontal extension 504 to which is attached a tongue 506. As shown in the enlarged view of detail A in FIG. 17B, the tongue 506 includes a mating aperture 508 for capturing the mating portion 436 of the guide pin 435, as best shown in FIGS. 20, 21 or 22. Accordingly, the tongue 506 is placed under the tapered end 437 of the guide pin 435 so that the mating aperture 508 engages with the mating portion 436 on guide pin 435. In an alternate example each of the mating aperture 508 and mating portion 436 can include threads thereon for engagement. The pin retrieval tool 500 also includes a pair of semicircular, serrated edges 510 and 512 which form a plurality of adjacent semicircular ridges that mate flush against the sides of adjacent full-length fuel rods 155 and/or part-length fuel rods 160 as the tongue 506 is inserted into the side of a fuel bundle 150. These serrated edges 510 and 512 help to maintain the pin retrieval tool 500 parallel with the side of the fuel bundle 150 being serviced. The serrated edges 510 and 512 thus help to maintain a proper alignment of the tongue 506 against the fuel bundle 150 so that the mating aperture 508 properly engages with the mating portion 436 on guide pin 435 and the tongue 506 without difficulty. FIG. 18 illustrates different tongue 506 length configurations. The tongue 506 can be reconfigured for varying lengths to reach part-length fuel rods 160 which may require tunneling several rows into the fuel bundle 150, in order to reach the interior part-length rod 160 to be extracted. Three different examples lengths of tongue 506A, 506B and 506C are shown in FIG. 18, for example. The pin retrieval tool 500 may be configured with tongue 506A for removing part-length rod 160 from the outside row of fuel rods 155/160, with tongue 506B for part-length rods that are a few rows into the bundle 150 interior, and with tongue 506C to reach part-length fuel rods 160 at the very center of the fuel bundle 150, around the water rods 170, if found to be located within this area of the fuel bundle 150. FIGS. 19-22 illustrate a process for removing the guide pin 435 from the rod grapple tool 400 within fuel bundle 150. Initially, the handling pole 502 lowers the pin retrieval tool 500 in the desired location within the bundle (FIG. 19), located just below the rod grapple tool 400 so that the tongue 506 is directly under the guide pin 435. The serrated edges 510 and 512 of the pin removal tool 500 abut flush to the sides of the fuel rods 155 and/or 160 of the fuel bundle 150 to ensure that the tongue 506 is properly oriented (level) so as to mate with the mating portion of the tongue's mating aperture 508 and mating portion 436 of the guide pin 435. The rod grapple tool 400 is then lowered as shown in FIG. 20 so that the guide pin 435 is received into the mating aperture 508 of tongue 506, and then manipulated to engage the mating portion 436 of the guide pin 435 with the mating aperture 508 of the pin removal tool 500 so as to capture the guide pin 435. FIG. 21 illustrates the guide pin 435 fully captured by the pin retrieval tool 500. As shown in FIG. 22, the handling pole 502 is then moved away from the fuel bundle 150 and stored suspended from FPM platform 115 with the guide pin 435 thereon. Of note, if the guide pin 435 is needed again, it is retrieved from the pin retrieval tool 500 underwater by the rod grapple tool 400. FIGS. 23A and 23B illustrate the procedure for attaching the gripper 432 of rod grapple tool 400 to an upper end plug 165 of a part-length rod 160. As previously described, the part-length rod grapple tool 400 must be placed in an extended position in order to remove the guide pin 435. This was shown previously in FIGS. 15A and 15B, in which the handler while holding the handle 402 rotates the threaded nut 407 counterclockwise until it comes into contact with the push-pull handle 404. This extends the gripper 432 with attached guide pin 435 from the end of the lower housing 430. Accordingly, once the guide pin 435 has been removed by the pin retrieval tool 500, the gripper 432 in its extended position is placed over the upper end plug 165 of the part-length rod 160. This attaches the part-length rod 160 to the rod grapple tool 400. As shown in FIG. 23A, the part-length rod upper end plug shoulder 167 can damage the spacer 180 when removing the part-length rod 160. However, and as previously described with reference to FIG. 16A and 16B, rod grapple tool 400 is manipulated to its retracted position, which locks the part-length rod 160 and the rod grapple tool 400 together, making one long smooth tube for safe part-length rod 160 extraction. This flush connection is shown generally by surface 450 in FIG. 23B. Accordingly, potential damage due to exposed upper end plug shoulder 167 has been eliminated by the rod grapple tool 400. The part-length rod 160 can be removed without causing damage to any of the spacers 180. The example embodiments of the present invention being thus described, it will be obvious that the same may be varied in many ways. For example, the rod grapple tool 400 has been described a being designed for a part-length rod 160, with another grapple tool used for the full-length rods 155 and/or tie rods due to a different upper end plug configuration. A different version (shorter in length) of this rod grapple tool 400 may be used for the removal and/or the replacement of tie rods and full length fuel rods 155 within the fuel bundle 150 For example, the full-length rods and tie rods can be configured to have the same upper end plug design as that of the part-length rods 160; thus a rod grapple tool having the same gripper 432 could be used for attachment to the upper end plugs of the full length fuel rods 155 and tie rods for removal from the fuel bundle 150. Such variations are not to be regarded as departure from the spirit and scope of the exemplary embodiments of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
048329053	abstract	A fuel assembly (10) has a lower end fitting debris collector (40) assembled in the form of a welded assembly of an "eggcrate" grid (21) and cast base (40) with hollow legs (42). Fastener seats (46) in hollow legs (42) permit guide tubes (14) with internally threaded ends to be joined to the upper surface of the lower end fitting debris collector (40) by means of slotted fasteners (50). Bevels (62) and notches (64) in the grid bars (26 and 24a, respectively), provide an embodiment with contoured seats for fuel rod end caps (22). Otherwise, end caps (22) rest on grid (21) at the intersection of slottedly interlocked bars (24 and 26). Thin strips (30) mounted in slots between bars (24) and bars (26) provide small debris catching openings in grid (21).
042954010	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 10 designates a spent highly radioactive fuel channel 10, typically made of zircalloy which has become highly radioactive, and reference numeral 12 designates a radioactive crust or crud which is formed on the channel during its use in a nuclear reactor. The illustrated channel is an approximately five inch square tube which is approximately fourteen feet long with open ends. The thickness of the walls of the channel is typically in the range of 0.080 to 0.12 inch. FIG. 1 illustrates the method of the invention. The spent radioactive fuel channel is stored in a pool 14 of water. In order to ship such fuel channels to the federal burial grounds within the country, the channels must be stored in a radioactive-shielded shipping cask 16. In accordance with this invention, in order to reduce the volume of the fuel channel for shipping, the channel is cut along its four longitudinal corners 18, 20, 22 and 24 to sever the channel into four rectangular side plates 26, 28, 30 and 32 which may then be nested to form a stack having a volume approximately ten times less than that of the fuel channel 10. In practice, after the fuel channel is severed into the side plates, the side plates are removed from the cutting apparatus 34 by suitable mechanical manipulator means controlled by an operator above the pool and stacked in a suitable disposal basket 36. Several side plates are stacked in each disposal basket, and then several disposal baskets are placed in the shipping cask 16. Since available shipping casks are of various heights, the fuel channel 10 may be cut into shorter lengths to accommodate the dimensions of the cask. Since the upper end of the fuel channel may have some projecting members which prevents tight nesting, this upper end may also be transversely severed and handled as a separate radioactive element. As will be explained in more detail in connection with the description of the preferred apparatus of the invention, the severing operation is accomplished by roller cutter blades, thereby reducing to a minimum the production of metal chips and any radioactive debris caused by flaking off of the radioactive crust during the cutting operation. Any chips or radioactive debris is collected by suitable filtering means for subsequent disposal. FIG. 2 schematically illustrates the preferred apparatus of the invention as applied to the disposal of spent fuel channels which are stored under water in a pool. A fuel channel 10 is shown already inserted in the corner cutter apparatus 34 which is supported by cables 38 and 40 from a bracket 42 attached to the edge 44 of the pool 14. A hydraulic cylinder and piston actuator 46 is fixed to the lower end of the outside of the apparatus 34 and actuates the fuel channel cutter assembly via a pulley and cable arrangement 48 which will be described in more detail below. The actuator 46 is connected via a pair of hydraulic lines 50 and 52 to a hydraulic power supply 54 whose operation is controlled by a cutter control console 56. Of course both the power supply and the cutter control console are located at the top of the pool. The support cables 38 and 40 maintain the cutter apparatus 34 in a vertical orientation. In order to prevent the pool water from being contaminated by metal chips or radioactive debris which may be flaked off of the fuel channel 10 during the cutting operation, a filtering system is provided to remove this debris from the apparatus 34. To achieve filtering, the water is pumped from the lower end of the apparatus 34 via a conduit or hose 60, and intermediate filter assembly 62, a suction pump 64 and a final filter 66 from which the filtered water is discharged back into the pool. As shown in FIG. 3, note that both the hydraulic lines 50, 52 and the filter hose 60 are strapped to the support cables 38 and 40. Any radioactive debris is trapped in the filters 62 and 66 for subsequent disposal. FIGS. 4-7 illustrate the cutter apparatus 34 used in this invention. The apparatus consists of an outer cylindrical tubular housing 70 which is suspended by cables 38 and 40 fixed to the support bar and bracket 42 which in turn is hooked to the pool's top edge. Mounted on the outside of the housing 70 at the lower end thereof are the piston and cylinder actuator 46 and the cable and pulley assembly 48. Mounted for longitudinal movement within the outer housing 70 is a cutter assembly 72 having four roller cutter blades 74 in engagement with the four longitudinal corners or seams, respectively, of the fuel channel 10. The cutter assembly 72 is mounted on a carrier assembly 78 which is supported within the inside walls of the outer housing 70 by four guide assemblies 80 which are driven in a reciprocating manner along the length of the fuel channel 10. In FIGS. 4-7, the cutter assembly 72 is shown in its upwardmost position generally opposite an upper mandrel assembly 82 which is disposed within the inside corners of the fuel channel 10 to act as a backing member for the cutter blades 74. Mandrel assembly 82 is fixed to cylindrical support member 86 extending the length of the fuel channel. As indicated, a duplicate mandrel assembly 82 is affixed to the lower end of support member 86. FIGS. 8-12 are sectional views showing the details of the cutter assembly 72. As shown in FIG. 8, the channel 10 may be supported on top of the mandrel assembly 82 by means of one or more inwardly extending straps 84 which are an integral part of a particular fuel channel to which this invention is addressed. (In such fuel channels, the upper end thereof may be transversely severed from the remainder of the channel in order to permit tighter nesting of the severed side plates.) It is seen that the cutter assembly 72 consists of four sets of three rollers which engage respective corners of the fuel channels. Two of the rollers 90 and 92 in each set are guide rollers, whereas the third roller 94 is a cutter roller having a cutter blade 96. These rollers are all mounted for rotation on stainless steel ball bearings, such as ball bearing 98. Each of the rollers 90, 92 and 94 has a concave recess 100 which mates with the corresponding slightly rounded corner 102 of the fuel channel 10. Thereby, all three rollers, including the cutting roller 94, act as guide rollers to keep the cutter assembly positioned relative to the fuel channel 10 so that the cutter blades 96 bisect the corner angles of the fuel channel 10, thereby assuring maximum nesting and compaction of the four side plates after they are severed. The cutter roller 94 is mounted for rotation on a shaft 104 which is journaled in a member 106. The upper guide roller 90 is mounted for rotation on a shaft 108 which is journaled in the member 110 such that the member 106 carrying the cutter roller 94 is pivotable about the shaft 108. The member 106 is welded to a cam 112 which is spring-biased outwardly by a spring 114. The lower end of a cutter adjusting screw 116 engages the inclined surface of the cam 112, and an adjusting knob 118 is fixed to the upper end of the adjusting screw 116. By moving the adjusting screw downwardly, the cutter blade 94 is moved inwardly to increase the depth of cut in the walls of the fuel channel 10. In operation, the cutter assembly starts in its upwardmost position, and the cutter rollers 94 are adjusted for the desired depth for the first downward cutting stroke. Upon return of the cutter assembly to its upper position and before it begins its next downward stroke, the adjusting knob 118 is turned to move the cutter blade inwardly to increase the depth of cut for the next downward stroke. All four cutter blades 94 may be simultaneously so adjusted at the top of each stroke until the four side plates are completely severed. It is noted that the mandrel assembly 82 is slightly rounded at the extremities thereof to mate with the curved corners of the fuel channel, and that each projection of the mandrel assembly has a small notch therein to accommodate the cutting blade 96 on the cutter roller 94. The cutter assembly 72 and carrier assembly 78 are supported within the outer housing 70 by means of the four guide assemblies 80, each of which has an upper double guide roller 120 and a lower double guide roller 122 which engage the inner wall of the housing 70. Referring to FIGS. 7 and 8, two of the guide assemblies 80 are affixed to and driven by the cable and pulley assembly 48. More specifically, one of the guide assemblies 80 is fixed at its upper end to a cable 126 which passes over an idler pulley 128, and is fixed at its lower end to another cable 130. In like manner, the diametrically opposite guide assembly 80 of FIG. 3 is fixed at its upper end to a cable 132 passing over a second idler pulley 134, and the lower end thereof is fixed to another cable 136 corresponding to the cable 130. The cable and pulley assembly 48 consists of a series of pulleys located at fixed points on the housing and on a horizontal bar attached to the end of the piston rod 47. This arrangement of pulleys results in a four-to-one mechanical advantage between the travel of the cutter head 72 and the travel of the piston rod 47. In other words for every inch of extension of the piston rod 47 the cutter head 72 will travel four inches. There are four groupings of cable and pulley assemblies but it will be necessary to describe only one as all four operate essentially the same. Reference is made to the right-hand power pulley assembly of FIGS. 3, 4, 5 and 6. Cable 130 is fixedly attached at 138 to the middle portion of casing 70 (FIG. 3). From there the cable runs down to pulley 140 mounted on the end of piston rod 47. The cable then runs up to pulley 142 and back down again to pulley 144 lying adjacent to pulley 140. From there the cable 130 runs up to pulley 146 then down to 148 and into the interior of casing 70. The cable 130 then runs up the inside of the casing to the lower portion of guide assembly 80 and is fixed at this point. The operation of the illustrated preferred apparatus of the invention may be summarized as follows. A plurality of spent, highly radioactive fuel channels 10 are stored under water in a pool. The corner cutter apparatus 34 is suspended in a vertical orientation under water from the edge of the pool. A human operator, using suitable mechanical manipulators, places a fuel channel 10 in the apparatus 34 so that the mandrel assembly 82 is inside of the channel. A channel hold down plate 83 is affixed to the upper mandrel assembly 82 by suitable bolts 85. The four roller blades 94 are adjusted by the adjusting screw 116 to the desired depth of cut for the first stroke of the cutting mechanism 72. The hydraulic power supply 54 is operative via the cutter controls console 56 to activate the piston and cylinder arrangement 46 to initiate a downward stroke of the cutter assembly. The pulley and cable arrangement 48, having a four-to-one mechanical advantage relative to the piston stroke, pulls the cutter assembly down to its lowermost position, thereby making a first cut through the longitudinal corners or seams of the fuel channel. The hydraulic power supply then returns the cutter assembly to its upwardmost position, where the adjusting screws are rotated wither individually or simultaneously to move the roller cutters inwardly for the next downward cutting stroke. This operation is continued until the four side plates are severed from the fuel channel. (The fuel channel may also be cut transversely into varying lengths to remove projections thereof which would prevent nesting and to accommodate the height of the ultimate storage casks.) The side plates are then removed by a mechanical manipulator, and several of the plates are then stacked or nested in a disposal basket 36, several of which are then stacked in the shipping cask 16. All of the above operations take place under water. Furthermore, there is provided a filtering system (62, 64 and 66) which removes from the housing assembly 34 and possible metal cutter slivers or radioactive debris produced during the cutting operation by the flaking off of radioactive crust on the exterior surface of the fuel channel. The filtered, uncontaminated water is then returned to the pool. The operation of the preferred apparatus of the invention thereby provides the means by which highly radioactive BWR fuel channels can be safely and economically shipped from the owner's storage pool for ultimate disposal with minimum infringement on pool space and without degradation of storage pool water.
046802436	description	DETAILED DESCRIPTION OF THE INVENTION In accordance with the process of the present invention, both surfaces of a wafer (which in one embodiment is silicon) are coated with a layer of an x-ray transparent material such as boron nitride. The boron nitride layer on a first side of the wafer is subsequently used to support a patterned layer of x-ray opaque material, as will hereinafter become apparent. The boron nitride on the first side of the wafer is covered with a layer of etch stop, which in one embodiment is a Dynagrip disk. The boron nitride on the second side of the wafer is then removed, thus exposing the silicon on the second side of the wafer. The layer of etch stop is then removed, and the exposed silicon is bonded to a support structure (in one embodiment, a pyrex ring) by a field assisted thermal (FAT) bonding process. This is done by placing the exposed silicon against the pyrex ring, heating the wafer and pyrex ring, and applying a voltage across the silicon-pyrex interface. Thereafter, the to-be-formed mask is coated with a second layer of etch stop (typically zirconium). A circular portion of the second layer of etch stop on the second side of the wafer is removed, thus exposing a portion of the underlying silicon. The exposed silicon is then removed. In one embodiment, a semianisotropic etchant is used to remove the exposed silicon. (A semianisotropic etchant is an etchant which etches along certain directions in a crystal lattice more rapidly than in others, but this difference in etch rates is less pronounced than that exhibited by anisotropic etchants.) The second layer of etch stop is then removed. At this point, the to-be-formed mask consists of a pyrex ring bonded to a silicon ring covered with a boron nitride membrane. The mask is then coated with a layer of material (typically polyimide) to provide extra mechanical support to the boron nitride membrane. The polyimide layer is then coated with a layer of material (typically tantalum) which bonds to gold and polyimide. The tantalum layer is then coated with a gold layer (which is opaque to x-rays). The gold and tantalum layers are then patterned using conventional techniques. The process in accordance with one embodiment of the present invention is illustrated by the flow chart of FIG. 1. The process begins with the step of polishing both sides of a silicon wafer 10 (FIG. 2). In one embodiment, wafer 10 has a diameter of 125 millimeters, a thickness of 625 plus or minus 25 microns, and a [100] crystal orientation. Wafer 10 is either undoped or lightly doped. After a QA inspection (step A in FIG. 1), both surfaces of the wafer are coated with a layer of boron nitride 12 (step B), typically five microns thick. (Hereinafter, the term wafer will be used to mean the silicon wafer and all substances deposited directly or indirectly thereon and the term substrate means just the underlying silicon 11.) In one embodiment of the invention, boron nitride layer 12 is deposited at 340.degree. C. from the flow of diborane and ammonia in a low pressure chemical vapor deposition (LPCVD) process. It is desirable to remove the boron nitride on one side of wafer 10 without etching any of the boron nitride on the other side of wafer 10. It is known in the art to cover the boron nitride 12 on one side of wafer 10 with a layer of etch stop so that the uncovered boron nitride on the other side of wafer 10 may then be removed without damaging the boron nitride covered by the etch stop. In the prior art, this is typically done by spinning a film of etch stop onto the wafer. If the etch stop does not completely coat the layer of boron nitride, a pin hole can develop in the coated boron nitride during the etching process. This pin hole could be a fatal defect, making the mask useless. Accordingly, it has been found that a Dynagrip disk 14 (FIG. 3) having a 5 inch diameter placed on one side of wafer 10 (step C of FIG. 1), will act as an etch stop that prevents pin holes from developing. This disk is part No. 714525, manufactured by Dynatek of Redwood City, Calif. The Dynagrip disk includes a layer of approximately 0.005 inch thick polyethylene coated with a wax. Dynagrip disk 14 is applied to boron nitride 12 on one side of wafer 10 after wafer 10 is heated to approximately 120.degree. C. A wax such as Dynatek Soft Blue Overlay Adhesive is applied to seal the edge 15 between Dynagrip disk 14 and boron nitride 12. Next, the exposed portion of boron nitride 12 is etched away (step D of FIG. 1) by soaking wafer 10 in a solution having a temperature between 20.degree. and 40.degree. C. that is 12.5 to 14.5% sodium hypochlorite and the remainder water. Wafer 10 remains in this solution until the exposed portion of boron nitride 12 is removed. Dynagrip disk 14 serves as an etch stop during this process. After the exposed boron nitride 12 has been removed from one side of wafer 10, Dynagrip disk 14 is removed by heating the wafer to about 120.degree. C. and lifting the disk off (step E of FIG. 1). The residual wax is dissolved, for example, in a solution of trichloroethylene or xylene at room temperature. Next, wafer 10 is affixed to a pyrex ring 16 using FAT bonding (step F of FIG. 1). FIG. 4 illustrates wafer 10 bonded to pyrex ring 16. Pyrex ring 16 has a coefficient of thermal expansion which approximately matches that of silicon substrate 11. Accordingly, pyrex ring 16 is made from a type of pyrex such as type number 7740 pyrex available from Corning Glass Co. of Corning, N.Y. The bond between substrate 11 and pyrex ring 16 requires no adhesive and is created by placing silicon substrate 11 and pyrex ring 16 so that they push against each other, heating wafer 10 and pyrex ring 16 to a temperature between 190.degree. and 500.degree. C., and applying several hundred volts across the silicon-pyrex interface in a manner to be described below. In one embodiment, a voltage of 1300 volts is applied during this process and a furnace temperature of 340.degree. to 350.degree. C. is used. Pyrex ring 16 and wafer 10 remain in the furnace with the voltage applied for approximately 80 minutes and then are removed. Prior to the FAT bonding process, it is important that the pyrex ring being bonded to substrate 11 is polished and clean. FIG. 5 illustrates the apparatus used to produce the FAT bond. Referring to FIG. 5 it is seen that while in the furnace, pyrex ring 16 is connected to a metal spider 18 at a corner region 20. A negative voltage is applied to pyrex ring 16 via metal spider 18, while a positive voltage is applied to substrate 11 via a terminal 19. A 600K ohm resistor is placed in series with metal spider 18. The point at which spider 18 contacts pyrex ring 16 is usually pitted during the FAT bonding process. Accordingly, it is desirable to have this contact area as small as possible without affecting the bonding to minimize any cosmetic problems. Also, with reference to FIG. 5, a second pyrex ring 22 is placed against boron nitride layer 12. Ring 22 protects boron nitride layer 12 from mechanical or electrical damage during the FAT bonding process from contact with the bottom of the furnace. FAT bonding provides several benefits that are not available from the more conventional epoxy bonds. For example, the FAT bond is resistant to alkali and acid etches. In addition, the FAT bond does not exhibit any of the aging problems which afflict epoxy bonds, nor do FAT bonds exhibit problems in high temperature environments. Once wafer 10 is bonded to pyrex ring 16, the resulting structure, although not yet completed, comprises mask 100 (FIG. 4). Referring to FIG. 6, after the FAT bond process, a zirconium layer 24 is sputtered onto all surfaces of mask 100 (step G in FIG. 1). In one embodiment, zirconium layer 24 is 800 to 1000 .ANG. thick, and is used as an etch stop during a subsequent KOH silicon etch. The KOH etch is used to remove a portion of silicon substrate 11 as described below. After forming zirconium layer 24, a mask layer 26 is deposited over zirconium layer 24 as illustrated in FIG. 6 (step H of FIG. 1). In one embodiment, mask layer 26 is a Dynagrip ring, which is merely a ring made from the same material as Dynagrip disk 14 (FIG. 3). After Dynagrip ring 26 is applied to mask 100, a 1% HF solution is applied to cavity 28 of mask 100 for about 15 seconds (Step I of FIG. 1) to remove a portion 24a of zirconium layer 24 as illustrated in FIG. 6. After portion 24a of zirconium layer 24 is removed, the remaining HF solution in cavity 28 is neutralized with a diluted KOH solution so that it will not damage the unprotected portions of zirconium layer 24 if it is spilled (step J of FIG. 1). After that, any neutralized HF solution is removed from cavity 28, and Dynagrip ring 26 is also removed by heating mask 100 to about 130.degree. C. Cavity 28 is then rinsed with xylene. Referring to FIG. 7, the region in cavity 28 near where the silicon substrate 11 is bonded to pyrex ring 16 is then covered by a mask material 30, such as Astrawax 23 which is a bistearamide wax available from the Durachem Corporation (step K of FIG. 1). Astrawax 23 is used to effectively mask the corner of the FAT bond. When sputtering zirconium 24 onto mask 100, it is difficult to cover the crevice 32 where the silicon meets the pyrex. Accordingly, the wax is used to cover crevice 32. This is done because during a subsequent silicon etch process described below, it is desirable to avoid etching the silicon near the FAT bond since the silicon near the FAT bond is under a mechanical stress. Astrawax 23 layer 30 thus serves as an additional mask during silicon etching. After the appropriate masking substances are applied to mask 100, the a portion 11a of substrate 11 is etched away. In a preferred embodiment of the invention, this is done by soaking to-be-formed mask 100 in a semianisotropic etchant (step L of FIG. 1). As is known in the art, there are isotropic etchants and anisotropic etchants that can be used to etch silicon. An example of an anisotropic etchant is KOH. Anisotropic etchants etch at one rate along preferred direction in a crystal lattice while etching at a much slower rate along other directions in the crystal lattice. The etch rate along the preferred direction can be as much as 100 times the etch rate along an unpreferred direction. This can cause several problems, e.g., the formation of pyramids when etching silicon (see U.S. Pat. No. 3,738,881, issued to Erdman, et al.), and the formation of pyramid-shaped etch pits. In addition, it is desirable etch a circular hole having a diameter of about 100 mm in substrate 11. Because of the directional preference of anisotropic etchants, when using an anisotropic etchant to etch circular holes, a step pattern, such as step pattern 29 illustrated in FIG. 8, is produced. Obviously, if a circular hole is desired, step pattern 29 is undesirable. (Although there are isotropic etchants which do not etch along preferred axes, as is known in the art, these isotropic etchants are difficult to control). To overcome these problems an oxidizing agent is used in the KOH etchant which increases the etch rate in the direction (direction [110] in the crystal lattice) that anisotropic KOH etchant normally etches at a slower rate. This prevents the formation of the step pattern illustrated in the plan view of FIG. 8. Because of this, a smooth contour is etched into the silicon. In a preferred embodiment, potassium chromate is used as the oxidizing agent. Potassium chromate is mixed in the KOH etchant in a 0.01 molar concentration. Although the KOH-potassium chromate solution etches more slowly in the direction indicated by arrow 27b than in the direction indicated by arrow 27a, this effect is less pronounced than the step pattern effect. In one embodiment of the invention, layer of zirconium 24 can be etched in a distorted circular shape to compensate for the slower etching of silicon along the direction of arrow 27b (FIG. 8). In such an embodiment, removed portion 24a of zirconium layer 24 has a shape such as that illustrated in FIG. 10. In another embodiment of the invention, an anisotropic etchant is used including a KOH solution mixed with a compound such as model number FC129 manufactured by 3M Corporation. FC129 is a surfactant which removes bubbles of hydrogen that form during the etching process away from the surface of the silicon so that fresh etchant can come into contact with the silicon. During the previous silicon etch step, mask 100 is removed from the KOH etchant before the desired hole is completely etched in silicon substrate 11. Accordingly, mask 100 is then subjected to a slow silicon etch to remove the remaining undesired part of silicon substrate 11. Specifically, during the start of the etching process, silicon substrate 11 is approximatey 24.6 mils thick. During the first KOH etching process, 22 of the 24.6 mils of silicon substrate 11 are removed. Mask 100 is then subjected to a slow KOH etch which removes the remaining 2.6 mils. This is done because during the fast etch process, bubbles are formed on the surface of the silicon and gas accumulates in cavity 28. When etching the remaining 2.6 mils of silicon, it is desired to etch at a slower rate so that bubbles and gas pressure do not push against boron nitride layer 12. This is typically done by lowering the temperature of the KOH solution. (During the fast silicon etch, the KOH solution is at 95.degree. C., and during the slow etch, it is at about 80.degree. C.) After portion 11a of silicon substrate 11 is removed, Astrawax 23 layer 30 is stripped off with a solvent such as xylene. Then, remaining zirconium layer 24 is removed with an HF etch. This etch is accomplished by immersing mask 100 in an HF solution for 10 to 15 seconds, which is sufficient time to remove zirconium layer 24 without damaging pyrex ring 16. After the slow silicon etch, the tension in boron nitride membrane 12 is measured in a manner described below. Because boron nitride membrane 12 is subsequently used to support a patterned layer of x-ray opaque material which must be aligned within submicron tolerances, it is necessary that membrane 12 be under tension so it cannot move with respect to the rest of mask 100. If the tensile stress in membrane 12 is inadequate, it is annealed (a process which increases the tension) by heating mask 100. Accordingly, after the slow silicon etch, the tension in boron nitride membrane 12 is measured to determine the amount of annealing required. This is done by using the apparatus illustrated in FIG. 11. Referring to FIG. 11, to-be-formed mask 100 is placed on a platform 102. The pyrex-platform interface forms an air-tight seal. In the center of platform 102 is a sintered bronze plug 104 which is coupled to a pipe 106. Affixed to pipe 106 is a pressure meter, e.g., a differential capacitance manometer 108 which measures the air pressure in pipe 106. Air is forced into pipe 106 which enters the cavity between platform 102 and boron nitride membrane 12. Because of the difference in air pressure on each side of boron nitride membrane 12, the membrane height changes. This change in height can be measured by any of a number of techniques. For example, laser interferometry can be used to measure the change in height at the center of the boron nitride membrane 12. In another embodiment, a microscope can be used to measure the difference in height in boron nitride membrane 12. This can be done, for example, by (1) focusing a microscope on boron nitride membrane 12 without the increased air pressure in pipe 106, (2) increasing the pressure in pipe 106 and (3) refocusing the microscope. By calibrating the microscope to provide a measurement of the height of membrane 12 versus the position the eyepiece must be in to focus the microscope on membrane 12, the height displacement is measured. Other techniques can be used to measure the displacement of membrane 12 as well. Once the height displacement in membrane 12 is measured, the tension can be calculated by the following formula: ##EQU1## where .DELTA.P=pressure difference r=radius of the membrane 12 PA1 h=height differential PA1 t=film thickness PA1 .sigma.=tensile stress PA1 E=Young's Modulus PA1 v=Poisson's ratio. It is desirable to have a tensile stress between 6.times.10.sup.8 dynes per centimeter and 10.times.10.sup.8 dynes per centimeter in membrane 12. After the above-described tension measurement, layer of boron nitride 12 is annealed (step P, FIG. 1). This is typically done by heating mask 100 to a temperature approximately 40.degree. C. above the temperature at which boron nitride layer 12 was deposited (in one embodiment, 380.degree. C.) until the boron nitride has a tension in the desired range. After annealing, a polyimide layer 32 (FIG. 9) is formed on boron nitride membrane 12 to provide added mechanical strength to the membrane and to facilitate bonding to tantalum layer 33. Tantalum layer 33 (which bonds to both polyimide and gold) and a gold layer 34 (which is x-ray opaque) are then deposited on polyimide layer 32. Gold and tantalum layers 33, 34 are then patterned in a known manner, e.g., as described in "Advances in X-ray Mask Technology," by Alex R. Shimkunas, published in Solid State Technology, pages 192 to 199, in September 1984, incorporated herein by reference. In this way mask 100 is formed which includes a pyrex support 16 bonded to a silicon ring 11. Silicon ring 11 is covered with x-ray transparent boron nitride membrane 12 and polyimide layer 32. Polyimide 32 is covered by patterned gold layer 34. Similarly patterned adhesive tantalum layer 33 is provided between gold layer 34 and polyimide layer 32. Mask 100 can then be used in the manufacturing of integrated circuits. Referring to FIGS. 12 through 15, a process in accordance with a second embodiment of the invention is illustrated. Referring FIG. 12, a silicon substrate 110 is bonded to a pyrex ring 116 before any boron nitride is deposited thereon. Substrate 110 and pyrex ring 116 are of the same type as in the previous embodiment and are bonded using the FAT bonding technique described above. Thereafter, the structure of FIG. 12 is completely coated with a layer of boron nitride 112 as illustrated in FIG. 13. Boron nitride 112 is between 3 and 5 microns thick and is deposited in the same manner as boron nitride layer 12 discussed above. As in the previous embodiment, boron nitride layer 112 supports a subsequently deposited patterned layer of x-ray opaque material. Thereafter, a portion 112a of boron nitride layer 112 is removed through any of a number of techniques, e.g., the above-described chemical etch or a plasma etch. In addition, in one embodiment of the invention, a sodium bicarbonate bead blast etch process is used. In accordance with this embodiment, a mechanical fixture 118 (FIG. 14) is placed over part of the mask as illustrated and sodium bicarbonate beads are propelled towards portion 112a of boron nitride layer 112. This is done, for example, using apparatus such as model number 6500 available from S. S. White Industrial Products of Piscataway, N.J. The sodium bicarbonate beads are model number 354-1620Y, also available from S. S. White Industrial Products. (Of importance, sodium bicarbonate is water soluble so that residual sodium bicarbonate can be removed from the mask with water.) Thereafter, a portion 110a of silicon substrate 110 (exposed by the removal of portion 112a of boron nitride layer 112) is removed by soaking the to-be-formed mask in either an HNA or a KOH solution. Boron nitride layer 112 acts as a mask to protect the pyrex ring during the silicon etch. The resulting structure is illustrated in FIG. 15. Thereafter, the process proceeds as in the previous embodiment of the invention, i.e., boron nitride 112 is annealed, and coated with polyimide, tantalum and gold (not shown). The tantalum and gold layers are then patterned. In accordance with another embodiment of the invention, instead of starting with a silicon substrate 110, one starts with a glass wafer such as borosilicate substrate 150 (FIG. 16). Borosilicate substrate 150 typically has a diameter of about 125 millimeters and a thickness of about 625 microns plus or minus 25 microns but other diameters and thicknesses can be used as well. In accordance with the process of this embodiment, a FAT bond is created between borosilicate substrate 150 and a metal ring 152 and simultaneously a FAT bond is created between metal ring 152 and pyrex ring 154. In one embodiment, metal ring 152 is titanium, but other metals, e.g., aluminum, zirconium, tantalum or niobium can be used. The FAT bond is created by placing borosilicate substrate 150, titanium ring 152 and pyrex ring 154 so they push against ech other, providing a voltage of about 1300 volts across the titanium-borosilicate interface and the titanium-pyrex interface and heating borosilicate substrate 150, titanium ring 152 and pyrex ring 154 to a temperature between 340.degree. to 350.degree. C. The resulting structure is then coated with a boron nitride layer 156 via an LPCVD process (FIG. 17). Boron nitride layer 156 is typically 3 to 5 microns thick. Thereafter, a portion 156a of boron nitride layer 156 is removed as in the previous embodiments to expose a circular portion 150a of borosilicate substrate 150 (FIG. 18). Exposed portion 150a of borosilicate substrate 150 is then removed by soaking to-be-formed mask 158 in an HF solution having a concentration of 100% and a temperature of 70.degree. C. (A 100% HF solution is defined as a solution that is 49% HF by weight, i.e., the standard HF reagent concentration.) During this process, remaining portion of boron nitride layer 156 protects pyrex ring 154. The resulting structure is illustrated in FIG. 19. Thereafter, boron nitride membrane 156 is annealed, coated with layers of polyimide, tantalum and gold, and the gold and tantalum layers are patterned as described above. In accordance with yet another embodiment of the invention, a silicon wafer 200 (FIG. 20) is coated on both sides with a layer of boron nitride 202 using the LPCVD process described above. A layer of metal 204, such as titanium, is then formed on one side of wafer 200, e.g., by sputtering or evaporation, to a thickness of 1000 .ANG.. Metal layer 204 is then covered with a photoresist layer (not shown) which is patterned in a conventional manner, thereby exposing a centrally located circular portion of metal layer 204. The exposed portion of metal layer 204 is then removed, leaving a metal ring 204 on the surface of boron nitride layer 202. The photoresist layer is then removed. Metal ring 204 is then bonded to a pyrex ring 208 using the FAT bonding process described above. Referring to FIG. 21, the boron nitride on top of substrate 201 is etched, e.g., using either a plasma, a bead blast etching technique, or a chemical etchant. During this process, the boron nitride on the bottom of wafer 200 (i.e., the side facing pyrex ring 208) is protected by a mechanical masking fixture. Thereafter, the entire silicon substrate 201 is removed by soaking the structure of FIG. 21 in a KOH solution of HNA (hydroflouric-nitric-acetic acid solution), while protecting pyrex ring 208 with photoresist or a mechanical masking fixture. The resulting structure includes boron nitride membrane 202 affixed to metal 204 which in turn is affixed to pyrex ring 208 as illustrated in FIG. 22. Then the boron nitride is annealed and covered with polyimide, tantalum and gold as described above. Of importance, the surface of membrane 202 which is covered with polyimide, tantalum and gold is free of hillocks, since it replicates the shape of removed substrate 201. Therefore, the surface of membrane 202 is smoother than in prior art masks. In yet another embodiment of the invention, instead of covering one side of boron nitride coated substrate 201 with titanium layer 206, an indium tin oxide layer (ITO) 212 is deposited on one side of the wafer to a thickness of 500 .orgate. (FIG. 23). ITO layer 212 is either sputtered or evaporated onto boron nitride layer 202. Because ITO layer 212 is conductive, a FAT bond can be provided between ITO layer 212 and pyrex ring 208 using the same temperature, time, and voltage used in the previous embodiments. Thereafter, the boron nitride 202 on top of silicon substrate 201 is removed as described above leaving the structure illustrated in FIG. 24 (to-be-formed mask 214). Thereafter, mask 214 is soaked in a KOH or HNA solution to remove silicon substrate 201, leaving the structure of FIG. 25. Of importance, because ITO layer 212 is thin, and is therefore transparent to x-rays and visible light, it need never be etched or removed. Accordingly, boron nitride layer 202 is then annealed and coated with polyimide, tantalum and gold. The tantalum and gold are then patterned as described above. In an alternative embodiment, the part of ITO layer 212 not bonded to pyrex ring 208 is removed using standard masking and etching tecniques. In accordance with yet another embodiment of the invention, both sides of a silicon substrate 250 are coated with a layer of boron nitride 252 as illustrated in FIG. 26. In accordance with this embodiment of the invention, boron nitride layer 252 is doped with titanium. This is typically done by adding organo-titanium reactant to the process gas during the LPCVD process. Such processes use 25 to 30 SCCM of ammonia, 60 to 70 SCCM diborane, and 540 to 600 SCCM of N2. (1 SCCM equals one cubic centimeter per minute at 1 atmosphere.) This process takes place at 340.degree. C. In one embodiment of the invention, 2 to 5 SCCM of TiF.sub.4 or tetramethyltitanium is added to the process gas mixture. In another embodiment, 25 to 50 SCCM of H.sub.2 and 2 to 5 SCCM of either titanium isopropoxide or tetraethoxy titanium are added to the process gas mixture. The hydrogen is added to avoid oxygen in the boron nitride. The doped boron nitride layer is typically 3 to 5 microns thick. In accordance with this embodiment of the invention, the FAT bond is created between titanium doped boron nitride layer 252 and a pyrex ring 254. This is done by placing the pyrex ring 254 against boron nitride layer 252, providing a voltage of approximately 1300 volts across the boron nitride-pyrex interface, and heating boron nirode-coated substrate 250 and pyrex 254 to a temperature between 340.degree. and 350.degree. C. Thereafter, the boron nitride 252 on one side of substrate 250 is removed as described above, thus exposing substrate 250. Then, substrate 250 is removed, leaving titanium-doped boron nitride membrane 252 bonded to pyrex ring 254. The boron nitride is then annealed, as described above, covered with polyimide, tantalum and gold, and the tantalum and gold layers are patterned as described above. While the invention has been described with reference to specific embodiments, those skilled in the art will recognize that minor changes and modifications can be made to this process without departing from the spirit and scope of the invention. For example, instead of using a silicon substrate, a glass substrate such as borosilicate, aluminoborosilicate, fused silica, or other form of glass can be substituted. (Borosilicate is easiest to FAT bond to silicon. Aluminoborosilicate and fused silica require an intermediate metal layer.) Accordingly, all such modifications come within the scope of the invention.
046722114	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS U.S. Pat. No. 4,317,042 to Frederick O. Bartell is incorporated by reference and is excerpted below to aid in understanding the modified cavity shapes of the present invention. Although the radiation properties of a blackbody are well defined by the earlier mentioned Stefan-Boltzmann law and Planck radiation formula, the radiation properties of blackbody simulators are not so tidily summarized. Numerous articles have been published which attempt to describe or define the radiation of a blackbody simulator having a specified cavity shape. In order to reach any useful conclusions, numerous simplifying assumptions are made in the published theories of blackbody simulators. In general, the theoretical studies of blackbody simulators have used as a figure of merit for a blackbody simulator its on-axis emissivity. More recent theoretical studies, such as "Emissivity of Isothermal Spherical Cavity with Gray Lambertian Walls", by F. E. Nicodemus, Appl. Opt., Vol. 7, No. 7, pps. 1359-1362, July, 1968, have been concerned with the angular uniformity of emissivity of a blackbody simulator. Experimental studies of blackbody simulators having cavity shapes which are spherical, conical, or cylinderical have demonstrated that the commonly used conical and cylindrical cavity shapes do not have the angular uniformity of emissivity which a true blackbody would have. Such experimental work is described, for instance, in "Cavity Radiation Theory" by F. O. Bartell and W. L. Wolfe, Infrared Physics, 1976, Vol. 16, pps. 13-24. As described in this second paper, the experimentally measured non-uniformity of emission of blackbody simulators may be explaied by considering the effect of the projected solid angle formed by the aperture with respect to the cavity surface. Experimental and theoretical studies have demonstrated that for a given cavity depth, i.e., distance along a perpendicular to the aperture to the furtherest position of the cavity surface, a spherical cavity will have lower but more uniform emissivity than a conical cavity when both are used as blackbody simulators. The cavity shapes for blackbody simulators of the present invention and those of U.S. Pat. No, 4,317,042 are based on the concept that opposite the aperture a conical apex will provide high emissivity, and that this high emissivity can be maintained across other positions of the cavity surface by a cavity surface which is shaped to assure that the projected solid angle of the aperture with respect to each portion of the cavity surface takes the same value as it does at the apex. Standard numerical integration techniques have been used to determine cavity shapes for a family of blackbody simulator cavities in which uniformily high emissivity may be expected. There are two concepts of principal importance in the description of the inventive blackbody simulator cavities. They are that of the projected solid angle and that of a primary radiating surface for a cavity. FIG. 1 diagrammatically illustrates a cross-section of a blackbody simulator core 101. The core 101, as will be described in more detail below, is of a material such as metal, graphite, or ceramic which may withstand the temperatures to which it will be heated to generate the desired radiation. On one side of the core 101 is an aperture 102 to an interior cavity 103. For minimum size, weight, complexity, and costs, cavities in blackbody simulators generally have rotational symmetry or are composed of subcavities which are each rotationally symmetrical. There are exceptions to this general rule of axial symmetry. For example the core or cavity of a spherical cavity blackbody simulator may be oriented in a tilted or off center way so the total system optical axis intersects the back wall of the sphere at a nonperpendicular angle. The aperture 102 is typically a circle, although other aperture shapes may be easily provided for by placing a suitable plate having a cut-out of the desired shape in the aperture or in front of the aperture. Aperture 102 has diameter D. Line 104 is the axis of rotational symmetry of the cavity 103. L is the depth of the cavity as measured along the rotational axis 104 from the aperture 102. Such a blackbody simulator provides apparent blackbody radiation from the aperture 102 as though it were a true blackbody located at the aperture and having the shape and size of the aperture 102. (Of course, a true blackbody radiates energy in all directions, unlike a blackbody simulator cavity which radiates simulated blackbody radiation only within a limited angular field measured from the rotational axis 104). The projected solid angle may be described as follows. Let S.sub.1 designate the surface 106 of the cavity 103, with s.sub.1 a point on S.sub.1. Let the figure formed by the aperture 102 be designated S.sub.2 and let a point on S.sub.2 be designated s.sub.2. Let d=d(s.sub.1,s.sub.2) be the length of the line 107 between s.sub.1 and s.sub.2. Let r be the distance from s.sub.1 to line 104, and let z be the point on line 104 at which a perpendicular to line 104 will intersect s.sub.1. Line 109 is the tangent to the cavity surface 106 at s.sub.1. Line 110 is the normal to the cavity surface 106 at s.sub.1. Line 108 is the normal to the aperture 102 at s.sub.2. Let A.sub.1 be the angle formed between lines 107 and 110, and let A.sub.2 be the angle formed between lines 107 and 108. The projected solid angle of the aperture 102 with respect to point s.sub.1 on s.sub.1 is given by the formula ##EQU1## As is well known, the projected solid angle of a second surface with respect to a first surface is proportional to the fraction of the total amount of radiant energy leaving the first surface that impinges on the second surface. If a uniform cavity surface is at a uniform temperature, i.e., the surface is isothermal, and if the projected solid angle of the aperture with respect to any portion of the cavity surface is constant, the radiation from each cavity surface portion through the aperture will also be constant. Therefore, such a uniformly heated cavity surface will tend to stay at a uniform temperature since each portion of the cavity surface will suffer the same energy loss through the aperture. FIG. 2 illustrates the concept of a primary radiating surface for a blackbody simulator cavity. In FIG. 2, a blackbody simulator core 101a is shown in cross-section. The blackbody simulator is assumed to be used to radiate electromagnetic radiation 201 from the aperture 102a onto some utilization object or volume or area 202. For instance, the blackbody simulator may be providing infrared radiation to an infrared optics system. The primary radiating surface of the cavity surface 203 is that portion of the cavity surface 203 which is in direct line of sight through the aperture 102a to some portion of the utilization object or volume or area 202. In FIG. 2, this would include that portion of the cavity surface 203 from point 204 around to the rear 205 of the cavity surface to point 206. The primary radiating surface of a cavity is therefore that portion of the cavity surface which may directly radiate energy onto some portion of the utilization object or volume or area 202. The importance of the concept of the primary radiating surface is that it is this portion of a blackbody simulator cavity surface which principally determines the emissivity and uniformity of emissivity of the blackbody simulator. If it is known that uses would be made of a blackbody simulator, i.e., what the utilization objects will be, and their planned distances from the aperture of the blackbody simulator, the inventive blackbody simulator cavity shapes may be designed to provide the desired high emissivity and uniformity of emissivity, as may be measured at the utilization objects. As is clear from FIG. 2, the closer a utilization object or volume or area 202 approaches the aperture, the larger the primary radiating surface will be. If it is not known what use will be made of a blackbody simulator, then a larger primary radiating surface will provide a device with greater versatility. Inasmuch as the inventive cavity shapes are rotationally symmetrical about an axis, in order to describe the cavity shapes, it is sufficient to specify a process for determining a radius of the cavity at all positions on the rotational axis. Therefore, the inventive cavity shapes will be described in terms of a two dimensional graph of a function which, if "rotated" about the rotational axis will form the inventive cavity shape. The inventive cavity shapes have not been susceptible to description by a mathematical formula. Numerical approximation techniques have been used to determine the cavity shapes. Each of the inventive cavity shapes will be described in terms of a "normalized form" which assumes that the depth of the cavity is unity and the diameter of the aperture is D. Proportional reduction or expansion of a normalized cavity shape will allow manufacturing of a cavity of any arbitrary depth. Each of the inventive cavity shapes has a conical apex opposite the aperture. A.sub.0 will be used to designate the apex half angle, i.e., the angle formed between the axis of rotational symmetry and the tangent to the cavity surface at the apex. As is well known, a conical apex in a rotationally symmetrical blackbody simulator cavity generates high emissivity along the axis of a symmetry. The inventive cavities will be shaped so that the high emissivity of the apex will be uniformly generated by all portions of the cavity surface or at least those portions which directly radiate energy onto utilization objects. As with the cavity in most commercial black body simulators, the inventive cavity shapes are rotationally symmetrical and are for use with a circular aperture. It will be obvious to one skilled in the art that the methods to be described below can be extended to define cavity shapes terminating in any arbitrary shape aperture. However, the practical difficulties in manufacturing cavities according to the teachings of the invention which will have a non-circular aperture tend to discourage production of blackbody simulators with such apertures. The conventional approach to providing a simulator for a non-circular blackbody is to insert a plate having a suitably shaped cut-out between a blackbody simulator having a circular aperture and whatever apparatus will be subjected to the radiation emitted from the blackbody simulator or alternatively to place such a plate in the cavity aperture. The apex half angle is a fundamental parameter in the definition of a specific cavity shape. Each of the embodiments of the invention described below define a family of cavity shapes which have as one of its parameters the apex half angle. The choice of a particular apex half angle for a cavity is made in part by reviewing the shapes which result from that choice to determine if the resulting maximum radial cross section will result in a blackbody simulator having an acceptable size and weight for the intended purposes. FIG. 3 is a graph of a function illustrating one of the "small aperture" embodiments of the blackbody simulator cavity shapes of U.S. Pat. No. 4,317,042. As discussed above, it is assumed that the axis of symmetry 104 is one unit long, with z=0 at the aperture 102 and z-1 at the apex end. The small aperture cavity shapes are determined by assuming that the aperture 102 is sufficiently small with respect to the length of the axis of symmetry 104 so that the integral specified in Equation 1 may be simplified by assuming that for each point s.sub.1 on S.sub.1, the quantities A.sub.1, A.sub.2, and d will be effectively constant during the integration over S.sub.2. As mentioned, the inventive cavity shapes are based on the concept that maximum uniform emissivity should be generated by a cavity shape in which the projected solid angle of the aperture with respect to points on the primary radiating surface of the cavity is held constant. The small aperture embodiments assume the entire cavity surface is the primary radiating surface. Using the mathematical terminology previously introduced (summarized in TABLE 1), under the simplifying small aperture assumption, at the apex, the projected solid angle of the aperture 102 will be ##EQU2## since the aperture 102 is perpendicular to the axis of symmetry 104. Therefore, since the projected solid angle of the aperture as seen from all cavity surface locations is a constant, then with respect to any other point s.sub.1, the projected solid angle of the aperture will be ##EQU3## Assuming A.sub.1, A.sub.2, and d will not vary during the integration over S.sub.2 leads to the following simplification of Equation (3): EQU sin (A.sub.0)=[cos (A.sub.1) cos (A.sub.2 )]/ d.sup.2 (4) Further, under out simplifying assumption, d.sup.2 =z.sup.2 +r.sup.2. Let line 111, shown in FIG. 1, be parallel to the axis of symmetry 104 and pass through s.sub.1. Let A'.sub.1 be the angle formed between lines 111 and 109, i.e., the angle of the tangent at s.sub.1 with respect to the axis 104. Then A'.sub.1 +A.sub.1 +A.sub.2 =90.degree.. After further observing that A.sub.2 =arctan (r/z), Equation 4 can be further simplified to: ##EQU4## Equation 5 is an equation which is susceptible to solution by numerical approximation techniques. At the apex, r=0, z=1, and A'.sub.1 =A.sub.0. An arbitrary set of points on the axis of symmetry 104 is chosen for which the corresponding cross-section radius will be computed. For instance, assume the cross-sectional radius will be determined for z=1.00, 0.99, . . . , 0.01, 0.00. Starting at the apex, i.e. z=1.00, the tangent specified by A'.sub.1 is followed up until it intersects the line perpendicular to the axis of symmetry determined by z=0.99, thereby determining a tentative corresponding value for r when z=0.99. A'.sub.1 at z=0.99 may be computed by use of Equation 5. To improve the accuracy of the curve which satisfies Equation 5, the value of A'.sub.1 which was computed should be averaged with A.sub.0 and from this average, a second r value is determined for z=0.99. From this second r value a second A'.sub.1 value can be computed. This second A'.sub.1 value should now be averaged with A., and from this new average, a third r value is determined for z=0.99. This iterative process should be repeated several times to improve the numerical accuracy of the r and A'.sub.1 values for z=0.99 which satisfy Equation 5. The values of r and A'.sub.1 when z=0.98 is determined in a similar manner from the values of A'.sub.1 and r for z=0.99. Continuing this process in sequence for each of the chosen points on the axis defines a curve as shown in FIG. 3. Table 2 lists the values of an embodiment of U.S. Pat. No. 4,317,042 determined with respect to the small aperture assumption when the apex half angle is 30 degrees. All cavity shapes determined by the described method have resulted in very small r when z=0, with smaller r for smaller values of A. When A.sub.0 have been 20.degree. or less, it has been r=0.0+0.00001 when z=0.0; and when A.sub.0 has been as large as 88.degree., it has been r=0.0+0.001 when z=0.0. Table 3, lists the maximum cross-sectional radii and corresponding z values which have been determined for various apex half angles. A'.sub.2 is the aperture half angle, i.e., the angled formed with respect to the axis of symmetry 104 by the tangent to the cavity surface S.sub.1 where it meets the aperture, i.e., z=0. As indicated in Table 3, the small aperture cavity shapes are characterized by having A'.sub.2 approximately -A.sub.0 /2 and the maximum cross sectional radius occurring near r=0.58 if A.sub.0 is not greater than 60 degrees. As shown in FIG. 3, the small aperture cavity embodiments have a smooth shape, except at the apex and aperture. The cavity shapes determined by the above described process are not of practical interest unless an aperture of useful size is provided, so that radiation may be emitted. Satisfactory results may be expected by truncating the curve defining the cavity as z between 0.01 and 0.31, and possibly at higher values, to form the aperture. Analogizing to the most popular designs for reentrant cone cavities, the preferred embodiments of the inventive small aperture cavities will truncate the curve at the point near the aperture that will result in an aperture radius which will be approximately 1/2 the maximum cross-sectional radius. Use of a more sophisticated numerical approximation technique, in which the integration over S.sub.2 is approximated by a finite sum, allows determination of other inventive cavity shapes without the necessity of the small aperture assumptions which led to Equation 5. FIG. 4A is a cross-section of an illustrative cavity shape of a "three surface" finite aperture embodiment of U.S. Pat. No. 4,317,042 in which the integral over S.sub.2 is computed in determining the aperture's projected solid angle with respect to points on the cavity surface S.sub.1. As previously discussed, it is assumed that the aperture is circular with diameter D. Numerical integration techniques approximate an integral over a surface by a finites sum, each term of the sum approximating the integral over a small portion of the surface. In the present invention, the surface S.sub.2 of the circular aperture has been approximated by several grids of elements. The more elements in this grid (i.e., the finer the grid), and the more closely the grid approximates S.sub.2, the more accurate the approximation to the projected solid angle of the aperture with respect to points on the cavity surface S.sub.1. Table 4a lists the x-y coordinates for the centers of a set of 57 squares which form a grid approximating a circular aperture with diameter D=8.52. Each square will have area 1. In order to compute the projected solid angle of S.sub.2 with respect to a point s.sub.1 on S.sub.1, the integrand of Equation 1 is computed with respect to the centers of each of the squares. It is assumed that the values of A.sub.1, A.sub.2, and d will not significantly vary over the small grid elements, and that therefore the projected solid angles of the aperture will correspond to the sum over the 57 squares. Although Table 4a lists the coordinates for a grid of 57 squares approximating a circular aperture with D=8.52, the coordinates of this grid may be scaled to approximate a circle with diameter D' by merely multiply each x and each y coordinate by D'/8.52. Table 4a should not be construed to imply that the embodiments of U.S. Pat. No. b 4,317,042 would have L/D=1/8.52. In actuality, useful cavity shapes have an L/D ratio of from less than 1/1 to more than 50/1 with most ratios between about 2/1 and 10.1. Table 4a is only meant to specify the manner in which a circular aperture may be approximated by a grid of elements. The coordinates of the grid elements of Table 4a may be scaled as necessary to provide any desired L/D ratio. An alternate grid of elements approximating a circle of diameter D=8.20 is provided by 61 hexagonal elements with centers having x-y coordinates as listed in Table 4b. The elements are tightly arranged in a hexagonal array. The hexagonal elements each have opposite sides separated by a distance of 1. The x-y coordinates of this array may be also scaled as necessary to approximate an aperture with any specific diameter to obtain a cavity with any desired L/D ratio. It will be obvious to those skilled in the art that the grid arrays of Tables 4a and 4b are arbitrary approximations to a circulr aperture, and that similar results will be obtained by substituting any other grid of elements that approximate the aperture's shape. Further, the modifications necessary to approximate non-circular apertures are equally obvious to those skilled in the art. It has been found that the cavity shapes which result from a numerical integration with respect to a grid of 57 squares based on Table 4a are in close agreement to those which are computationally based on a hexagonal grid of 61 elements based on Table 4b. It is not the particular grid which determines the cavity shape, but the size of the aperture being approximated by the grid. Two other grids have been useful. The seven innermost points of Table 4b, (0,0), (0,.+-.1), (.+-.0.5 .sqroot.3,.+-.0.5) have been used to obtain approximate results with a Hewlett Packard Model 41C handheld calculator. The twenty-one innermost points of Table 4a, (0,0), (0,.+-.1), (.+-.1,0), (0,.+-.2), (.+-.2,0), (.+-.1,.+-.1), (.+-.1,.+-.2), (.+-.2,.+-.1, have been used to obtain cavity shapes that are in close agreement to those based on all 57 points of Table 4a. The embodiments of U.S. Pat. No. 4,317,042 based on a numerical integration over the aperture result in a cavity surface having an axial cross-section with the general appearance of the curve of FIG. 4A. As previously mentioned, in determining a particular cavity shape, one parameter is the apex angle A.sub.0. Another parameter is D, the aperture diameter, or more precisely the L/D ratio. Since the normal form for describing the cavity shapes has L=1, an aperture diameter D allows direct conversion to the corresponding L/D ratio. Once A.sub.0 and D have been specified, the following method may be used to determine a cavity shape in which the projected solid angle over the aperture 102 with respect to points on the cavity surface 106 is constant. As before, it is assumed that the axis of symmetry has length L=1. It can be proved that a spherical cavity with diameter [1+(sin (A.sub.0))(D.sup.2 /4)]/.sqroot.sin (A.sub.0) having a circular aperture of diameter D will have a projected solid angle of its aperture with respect to all points on the cavity surface that is identical to the projected solid angle of the same aperture with respect to a conical apex opposite the aperture at z=1 with half angle A.sub.0. Further, it can be proved that the projected solid angle of an aperture on a spherical cavity with respect to any point on the cavity surface is constant. In other words, spherical shaped cavities may be considered to be a limiting case for the inventive cavity shapes as A.sub.0 approaches 90 degrees. The importance of these observations are that, given a conical apex at z=1, a first portion 401 of the cavity surface near the aperture 102 may be defined by a sphere 400 with diameter [1+(sin (A.sub.0))(D.sup.2 /4)]/.sqroot.sin (A.sub.0). The projected solid angle of the aperture with respect to any point on this first subsurface 401 will be the same as is at a conical apex at z=1 with half angle A.sub.0. Numerical techniques are used, in a manner similar to that described earlier with respect to the small aperture embodiments, to incrementally extend the conical apex from z=1.00 toward z=0. Unlike the small aperture embodiments, for each z value for which an r value will be determined, a numerical integration over the aperture surface must be performed. Nevertheless, the numerical approximation techniques to determine successive cross-sectional radii and tangents for decreasing z values is straightforward, although computationally lengthy. More specifically, at z=1.00, r=0, Equation 1 can be used to determine the projected solid angle of the aperture at the apex by summing over the elements in the grid rather than integrating over S.sub.2, with the integrand of Equation 1 determined for each grid point, and with dS.sub.2 replaced by the area of each element. A straightforward computation allows a determination of A.sub.1, A.sub.2, and d for each grid element with respect to the apex. The tangent at the apex can be extended until it intersects the line perpendicular to the axis of symmetry at z=0.99, or whatever z value closer to the apex for which the cross-sectional radius is next to be computed. Using A.sub.0 as a first approximation for determining the r value at this second Z value, by standard interpolation and iterative techniques similar to those described earlier, the finite sum version of Equation 1 may be solved to determine corresponding A'.sub.1 and r values for the chosen z value such that the projected solid angle of the aperture remains the same as it was at the apex. The process may be continued step by step for z=1.00 toward z=0, thereby defining a second subsurface 402 of the cavity which extends the conical apex in a manner to hold constant the projected solid angle of the aperture 102 with respect to each point on this second subsurfce 402. For each finite aperture cavity shape embodiment which has been determined by this numerical integration technique, there is a point X on this second subsurface 402 which for most practical cavities has a z value between z=0.50 and z=0.20, in which the tangent 403 of the cavity surface at this point intersects the rim of the aperture. When this occurs, the second subsurface 402 of the cavity surface cannot be further continued since to continue it would define a cavity shape in which previously defined portions of the second cavity subsurface 402 would not be in direct line of sight of all of the aperture. Such an occurance would violate the conditions of determination of the previous points where it was assumed those previous points were in direct line of sight of the entire aperture. A third subsurface 404 of the finite aperture cavity surface embodiment joins the second subsurface 402 to the first subsurface 401, thereby completing the cavity shape. It is determined in the following way. At point X on the second subsurface 402, a line 405 is drawn which intersects the rim of the aperture at a point opposite the point on the aperture at which the tangent 403 to subsurface 402 at X intersects the aperture. This line 405 is assumed to approximate a tangent to the third subsurface 404 at X in which the third subsurface 404 is moving away from the aperture. This tangent 405 is used to define an initial guess of a small portion of the third subsurface 404. A point on this line 405 is chosen near X to define an initial guess for a new value of z and r. An appropriate tangent at this point is then calculated by the previously discussed numerical integration and approximation techniques. An average tangent is then calculated which is half way between the tangent just calculated and the initial guess tangent 405. This average tangent is then used in place of tangent 405 to find a second guess value of z and r. From the new z and r a new calculated tangent is determined. By iteration, final values of z and r are found. The point X is the last point on subsurface 402 and the first point on subsurface 404. The point (z,r) just found is the second point on subsurface 404. Successive points on subsurface 404 are then determined the way successive points on subsurface 402 were found. This process continues until the third subsurface 404 intersects the first subsurface 401. The curve of FIG. 4A is illustrative of the resulting cavity cross-section for such a "three surface" finite aperture embodiment. For many parameter combinations of A. and L/D that are of practical interest, the tangent to subsurface 404 is approximately perpendicular to the axis of rotational symmetry 104 at the point where surbsurface 404 intersects the first subsurface 401. Table 5 lists the z and r values for such a "three surface" finite aperture embodiment in which A.sub.0 =45.degree. and D=0.1 (with L=1, of course). Although the method described to determine a finite aperture cavity shape embodiment results in a cavity shape in which the projected solid angle of the aperture is constant with respect to any point on the cavity surface, there is a disadvantage to these "three surface" finite aperture embodiments in that the maximum radial cross-section may approach that of the sphere used to define the first subsurface 401. Although the embodiments are shorter than the sphere, it would also be desirable to reduce the maximum cross-sectional radius, thereby reducing the size, weight, and cost of the resulting black body simulator. The simplest approach to obtaining a more commercially practical finite aperture cavity shape is to relax the requirement that the aperture's projected solid angle be constant with respect to all points on the cavity surface. By requiring the projected solid angle to be constant only over a cavity's primary radiating surface, significant economics may be obtained. It is believed that such a requirement will not seriously affect the high uniform emissivity of a blackbody with a cavity so simplified since the devices receiving the radiation emitted from the aperture will not be in the line of sight of the cavity portions in which the projected solid angle is not held constant. FIG. 4B illustrates several simplifications of the cavity shape of FIG. 4A. In each such cavity shape, it is assumed that there is no material deviation from the cavity shape of FIG. 4A over the primary radiating surface. Line 410 provides a cavity in which the cavity shape of FIG. 4A is merely truncated beyond a certain maximum radius. This results in a cavity having a cylindrical portion between the first and second subsurfaces of FIG. 4A. Line 411 truncates the curve of FIG. 4A at a maximum cross-sectional radius, which is extended to the plane of the aperture, thereby resulting in a cavity in which the cavity portion near the aperture is cylindrical with the aperture on the axial end of the cylinder. Of course, rather than having a cavity shape with the previously described first subsurface 401 of FIG. 4A, the cavity may be extended in a cylindrical manner from a point on the third subsurface 404 to the plane formed by the aperture 102, as indicated by line 412. Such an embodiment may not materially reduce the maximum cross-sectional radius, but does offer economics in manufacturing since the curved first subsurface 401 of FIG. 4A is avoided. Other simplications to the finite aperture embodiments will be obvious to those skilled in the art. So long as the projected solid angle of the aperture with respect to the primary radiating surface is constant or approximately constant, the approximately uniform and high emissivity of the inventive cavity shapes will be assured. FIG. 4C illustrates one of a series of "Fresnel" embodiments of the blackbody cavity shapes of U.S. Pat. No. 4,317,042. Fresnal embodiments are a variation on the finite aperture embodiments. Each Fresnel embodiment has as design parameters A.sub.0, the apex half angle, D, the aperture diameter, and M, the maximum desired cross-sectional radius. For FIG. 4C, A.sub.0 =50.degree., D=0.25, and M=0.35. A Fresnel cavity shape embodiment defines first 401 and second 402 subsurfaces in the same manner as a finite aperture embodiment with the same A.sub.0 and D. The third subsurface 404 is extended only to point X', where r=M. At this point, a fourth subsurface 420 is determined which approaches z=0 again. The initial tangent 421 to the fourth subsurface 420 at X' may be satisfactorily approximated by ensuring that the tangent 421 at X' forms the same angle with respect to a line 422 from X' to the center of the aperture 102 that the tangent 423 of subsurface 404 at X' forms with line 422. This fourth subsurface 420 is continued in a similar manner as was done with the second subsurface 402 until it intersects the first subsurface 401 or its tangent 424, say at X", intersects the aperture. At X", a fifth subsurface 425 is defined in a manner analogous to the third subsurface 404. This computational determination of subsurfaces continues until one of the subsurfaces intersects the first subsurface 401, resulting in a "Fresnel" version of a finite aperture embodiment in which the maximum cross-sectional radius is limited to a maximum value M, yet for which the projected solid angle of the aperture is constant with respect points on each of the subsurfaces. The "tilted sawtooth" configuration of the Fresnel portion 426 of the cavity surface of FIG. 4C may be satisfactorily approximated by a threaded cavity shape which does not materially differ from the computed shape. The tilted sawtooth configuration of the Fresnel portion 426 of the cavity surface of FIG. 4C and the threaded cavity shape which was mentioned as a variation to FIG. 4C suggest worthwhile variations to the cavity shapes shown in FIG. 4B. Lines 410, 411, and 412 of FIG. 4B provide cavity shapes with cylindrical parts. Those cylindrical parts might be replaced by a tilted sawtooth, tilted thread design, or a more conventional thread design. Such replacements of the cylindrical parts might be performed with relatively small increases in complexity and with appreciable improvements in the approximation of these cavities to cavities which have the projected solid angle of the aperture a constant when viewed from all points on the cavity surface. FIG. 4C with A.sub.0 =50.degree., D=0.25 and M=0.35 is useful to describe the general class of Fresnel embodiments of the inventive blackbody cavity shapes. However, the relatively large areas of subsurfaces 404 and 420 tend to make this a less suitable design for most applications. FIG. 4D shows a cross-section of a full cavity and core of a Fresnel embodiment. For FIG. 4D, A.sub.0 =76.5.degree., D=0.385 and M=0.40. Table 6 lists the corresponding coordinate values. The relatively large area of subsurface 402 and the relatively large value of D make this an attractive design for many applications. FIGS. 4C and 4D show that the sequence of points X, X.sup.II, X.sup.III, . . . X.sup.V (for FIG. 4D) or X.sup.XII (for FIG. 4C) form an arch 430. As the parameter M varies, the X points move back and forth on this arch, but the arch, and especially its maximum distance from the axis of symmetry 104, remain approximately constant. This maximum distance of the arch from the axis of symmetry 104 is important in the selection of the value of M. If M is closer to this maximum distance of thearch from the axis of symmetry 104, there will be more and smaller "teeth" in the cavity cross-section, somewhat like FIG. 4C. If M is farther from this maximum distance of the arch from the axis of symmetry 104, there will be fewer and larger "teeth", more like FIG. 4D. The maximum value of M is the distance fromm the axis of symmetry 104 to the place where subsurfaces 404 and 401 would intersect if they were not interrupted. The minium value of M is the maximum distance of the arch from the axis of symmetry 104, because points inside the arch cannot have the same projected solid angle of the aperture as do the other points on the cavity wall surface. If such a small value of M is nevertheless desired, then a different embodiment of the inventive cavity could be employed according to FIG. 4B, where the projected solid angle of the aperture is maintained constant only where viewed from points on the primary radiating surface. Thus, it is seen that the arch 430 and the sphere 400 define a region of subsurfaces. Additional examples of cavity subsurfaces within the region of subsurfaces are shown in FIGS. 5A-5F and are described and claimed in my copending applications Ser. No. 502,004, filed June 7, 1983 U.S. Pat. No. 4,514,639. FIGS. 5A-5F illustrate cross-sections of several embodiments having aperture half-angles less than 60.degree.. In each of these embodiments, the cross-sectional curve of the cavity shape lies between a pair of inner and outer limiting curves, both of which lay within the region of subsurfaces. FIG. 5A shows a cross-section of a cavity shape embodiment having an apex half-angle of 13.degree.. A first subsurface 510 extends from the apex 507 to the inner limiting curve which in this case is an arch 530 which is defined in a manner similar to that of arch 430 of FIG. 4C. Accordingly, a tangent to the surface 510 at point Y intersects the rim of the aperture 506. A second subsurface 511 extnds from the intersection of the surface 510 with the arch 530 at point Y to the outer limiting curve 508 which is a straight line passing through the apex 507 and perpendicular to the axis. The outer limiting curve 508 is placed a distance N of 1.0 from the plane of the aperture 506. Extending from Y' (the point at which the subsurface 511 intersects the outer limiting line 508), a third subsurface 512 extends to the inner limiting curve 530 until the tangent to the subsurface 512 intersects the rim of the aperture as indicated at Y". This computational determination of subsurfaces continues until subsurface 518 intersects the inner limiting curve 530. In order to reduce the overall width of the cavity, the next subsurface 519 extends from the inner limiting arch 530 to a second outer limiting curve 509 which is a straight line parallel to the axis at a distance M (which is 0.6 in this embodiment) from the axis of symmetry. The computational determination of the subsurfaces then continues in a manner similar to that described for FIGS. 4C and 4C until one of the subsurfaces (subsurface 529) intersects the subsurface 401 described in connection with FIGS. 4A-4D. Each of the subsurfaces of the cavity of FIG. 5A are characteized by the fact that the projected solid angle of the aperture with respect to the subsurfaces remains constant for each point on the subsurfaces. Table 7 lists a representative set of z and r coordinates for the subsurfaces of the cavity of FIG. 5A. An alternative embodiment is shown in FIG. 5B, which resembles the embodiment shown in FIG. 5A except that the perpendicular outer limiting curve 508 of FIG. 5A is replaced by a slanted straight line outer limiting curve 500 which makes an arbitrary 63.degree. angle with the perpendicular axis through the apex. The inner limiting curve 580 is also an arch similar to the arches 530 and 430 of FIGS. 5A and 4C, respectively. Accordingly, the tangents to the subsurfaces at the arch 580 intersect the rim of the aperture 506. The remaining outer limiting curve is again the line 509 parallel to and spaced a distance of 0.6 from the axis of symmetry. The resulting subsurfaces are less deep and somewhat more uniform in cross-section than those shown in FIG. 5A. A representative set of coordinates for the subsurfaces of the cavity of FIG. 5B is listed in Table 8. This embodiment has an apex half angle of 15.degree.. The cavity shape represented by the outline shown in FIG. 5C is also similar to that shown in FIG. 5A. Here however, the inner limiting arch 530 of FIG. 5A has been replaced by a pair of perpendicular lines 601 and 602 parallel to the outer limiting lines 508 and 509, respectively. The outer limiting line 509 is placed a distance of 0.65 from the axis of symmetry and the inner limiting line 602 is placed at a distance O of 0.55 from the axis. The other inner limiting line 601 is placed a distance P of 0.85 from the aperture. As seen in FIG. 5C, this embodiment may conveniently be fabricated with a backwall plate and sidewall cylinder as starting materials from which the subsurfaces may be machined. The embodiment of FIG. 5C has an apex half angle of 20.degree.. Representative coordinates for the subsurfaces are listed in Table 9. Combining elements of the previous three embodiments, FIG. 5D shows a cavity outline in which the inner and outer limiting curves 508 and 601 of FIG. 5C are replaced by slanted straight line inner and outer curves 650 and 651. The lines 650 and 651 are slanted at an angle of 68.degree. with respect to the perpendicular. The apex half angle of the embodiment of FIG. 5D is 21.degree.. Table 10 lists representative coordinates for the cross-sectional outline of this embodiment. FIG. 5E shows an embodiment having an outer limiting curve 701 defined by a circle having a radius of 0.6 with a center indicated at 702 which is at a distance of 0.4 from the aperture. The inner limiting curve 703 is also defined by a circle having a radius of 0.45 with the same center 702. The embodiment of FIG. 5E has an apex half angle of 20.degree. and the subsurfaces are represented by the coordinate points listed in Table 11. FIG. 5F shows an embodiment which has inner and outer limiting curves 751 and 752 which are similar to the curves 703 and 701 of FIG. 5E except that a sine wave perturbation has been added to the two circles. Accordingly, it is seen that the inner and outer limiting curves may be arbitrarily selected to have any shape within the region of subsurfaces described above. The embodiment of FIG. 5E has an aperture half angle of 20.degree. and the subsurfaces are represented by the coordinates listed in Table 12. As previously mentioned, FIG. 4C shows a region of subsurfaces between the arch 430 and sphere 400. Examples of cavity subsurfaces within the region of subsurfaces are shown in the above described FIGS. 5A-5F. Embodiments of the present invention are illustrated in FIGS. 6A, 6B, 7A, 7B, 8A and 8B. The cavities of these Figures are additional examples of cavity subsurfaces within the region of subsurfaces between the arch 430 and the sphere 400 of FIG. 4C. FIGS. 6A and 6B show embodiments like that of FIG. 5C with an L/D ratio of 5:1, but, in accordance with the present invention, where FIG. 5C has an apex half angle A.sub.o of 20.degree., the cavities of FIGS. 6A and 6B have apex half angles of 30.degree. and 40.degree., respectively. As shown in FIGS. 6A and 6B, cavity designs which have larger apex half angles also have a more simple structure and are therefore easier to build. Although increasing the apex half angle reduces the emissivity of the cavity, it has been determined that the reduction in emissivity is relatively small, as more fully explained below. In order to further simplify the cavity design, the spherical subsurface 401 extending from the aperture of the cavities of FIGS. 6A and 6B is larger than the corresponding subsurface 401 of the cavity of FIG. 5C. In another aspect of the present invention, FIGS. 7A and 7B show cavities in which the ratio of the cavity depth (L) to cavity aperture diameter (D) has been reduced. The cavity of FIG. 7A is similar to that of FIG. 6A in that they both have an apex half angle of 30.degree.. However, the cavity of FIG. 7A has an L/D ratio of 5:2 in contrast to the L/D ratio of 5:1 for the cavity of FIG. 6A. Thus, if the aperture diameters of the cavities of FIGS. 6A and 7A are the same, it is seen that a significant reduction in size and weight has been achieved in the cavity of FIG. 7A relative to the cavity of FIG. 6A. It has been found that reducing the L/D ratio also decreases the emissivity of the cavity. However, for many applications, the advantages of the reduced size and weight of the cavity can far outweigh the disadvantage of any decreased emissivity. Even greater savings in size and weight can be achieved by further decreasing the L/D ratio of the cavity. FIG. 7B shows a cavity which is similar to that of FIG. 6B where both cavities have an apex half angle of 40.degree.. However, the L/D ratio of the cavity of FIG. 7B is 1:1 as compared to L/D ratio of 5:1 for FIG. 6B. The amount of reduction in emissivity associated with larger values of the apex half angle and reduced L/D ratios is shown by the following equations set forth in a paper by Frederick O. Bartell entitled: "The Symbiotic Relationship Between Infrared Imaging Arrays and a New Type of Blackbody Simulator", Proceedings of SPIE, Volume 501, State-of-the Art Imaging Arrays and Their Applications, (Aug. 21-23, 1984). ##EQU5## It is believed that the values of the projected solid angle of the aperture as seen from points on the cavity wall change with the apex half angle for the embodiments shown in FIGS. 5C, 6A, and 6B (A.sub.0 values of 20.degree., 30.degree. and 40.degree. ) in the ratios of approximately 1.000:1.462:1.879. In accordance with equation 6 above, for a wall emissivity of 0.5, it is believed that the emissivities of these three cases are approximately 0.9966, 0.9950 and 0.9936. Thus, increasing the apex half angle from 20.degree. to 30.degree. and from 30.degree. to 40.degree. simplifies the construction of the cavity at a relatively small penalty in emissivity. The amount of the reduction in emissivity associated with smaller values of L/D (the ratio of cavity depth to aperture diameter) may be shown in a similar way. For many applications, this reduction in emissivity is not critical. For such applications, the reduction in the overall size and weight of the cavity by reducing the L/D ratio can be quite significant. For example, by reducing the L/D ratio of 5:1 of the cavity of FIG. 6A to the L/D ratio of 5:2 of the cavity of FIG. 7A, the weight of the FIG. 7A cavity would be reduced to about 1/8th that of the cavity of FIG. 6A, if the FIG. 7A cavity were uniformly scaled down by 1/2 to result in a cavity with an aperture of the same size as that of FIG. 6A. Similarly, the cavity of FIG. 7B which has an L/D ratio of 1:1, may weigh as little as 1/100th that of the cavity of FIG. 6B if the cavity of FIG. 7B were scaled down by approximately 1/5th. The construction of these cavity shapes may be further simplified by relaxing the requirement that the aperture's projected solid angle remain constant for certain portions of the cavity surface. For example, FIG. 8A shows a cavity similar to that of FIG. 6A in which the outer radial portion of the cavity has been truncated. Specifically, the outer cavity subsurface 815 and a portion 401a of the spherical cavity subsurface 401 has been replaced by cylindrical subsurface 816. Such a substitution can result in considerable savings of size and weight. However, these advantages may be partially offset by limitations on the performance of the cavity caused by the subsurface 816 which does not maintain the constancy of the projected solid angle of the aperture as seen from points on the subsurface 816. These limitations are: (1) Multiple reflection contributions to the total cavity performance will be degraded, and (2) the size of the primary radiating surface is reduced. With respect to degraded multiple reflection contributions, small aperture embodiments such as the embodiment of FIG. 6A are likely to be less affected than the larger aperture embodiments such as FIG. 7A or 7B. If the primary radiating surface is reduced, FIG. 2 shows that as the available portion of the cavity wall surface is reduced, the angular size of objects that might be illuminated is also reduced. Thus, it might be appropriate to move an object to be illuminated further from the blackbody simulator cavity to maintain illumination by a radiating surface having a constance projected solid angle of the aperture as viewed from all points on that (primary) radiating surface. A possible disadvantage of moving the object to be illuminated away from the aperture is that the total amount of power available to the illuminated object might be reduced. For some applications, the size of the primary radiating surfaces is of less importance. Accordingly, additional savings in size and weight can be achieved by further truncation. Phantom line 817 of FIG. 8A represents a cylindrical surface replacing the subsurfaces 813, 814, 816 and 401b of FIG. 8A. The subsurfaces of each of the cavities may be smooth or rough but in general, rough surfaces are preferred over smooth surfaces. Blackbody simulators are often used in the infrared region of the electromagnetic spectrum to provide wavelengths from 0.7 microns to 1000 microns although most blackbody simulator usage today is for wavelengths from about 0.5 to about 30 microns. As a result, for many applications, a roughness fine structure from approximately 0.0001 inches to approximately 0.01 is appropriate. Threaded and saw-tooth cross-sectional subsurfaces may also be utilized, particularly for the cylindrical substitute subsurfaces such as that indicated at 816 in FIG. 8A. The threaded surfaces may be as fine as 80 threads per inch or finer. For some applications, more coarse threads are also appropriate having threads up to 1/4" or greater in size. Subsurfaces having a saw-tooth cross-sectional shape might have teeth ranging from 0.1" to perhaps 0.5" or more. The above noted dimensions are particularly applicable to blackbody simulator cavities having an internal depth from approximately 1" to approximately 10". For larger or smaller cavities, the dimensions should be varied accordingly. To further simplify the construction of the simulator, the spherical subsurface 401 can be completely replaced by a cylindrical subsurface 818 and flat aperture plate 819 as shown in FIG. 8B. Further truncation can be achieved by substituting cylindrical subsurfaces 816 or 817, for example as represented in phantom in FIG. 8B. The manufacturing of blackbody simulators using the invention cavity shapes is conventional. Typical construction will involve a cylindrical steel, graphite or ceramic core 101 as shown in FIG. 4D. Typical heating methods will be by the use of insulated nichrome wire 501 wrapped in a spiral around nearly all of the curved side of the cylindrical core. One or more temperature sensors 502, such as thermocouples or platinum resistance thermometers will be fitted into narrow cylindrical cavities which will open to the opposite face of the cylinder from the cavity aperture. Insulation 505 will be used on all sides, and the entire assembly will be contained in an appropriate cylindrical or other shaped enclosure 503, with an opening provided to expose the cavity aperture. Insulation material and thickness will be determined by temperature reequirements. Special vacuum type thermal insulation will be used for space and space simulator applications. A fan 504 may be located in the opposite end of the enclosure from the aperture to provide cooling. A conventional temperature controller controls the electric power to the heating wire 501 based on signals from a temperature sensor 502. It will be obvious to those skilled in the art that the desirable properties of the inventive cavity shapes may be obtained by minor deviations from the previously disclosed embodiments without departing from the scope of the invention. For instance, although the described cavity shapes are formed from one or more smoothly curving subsurfaces, a cavity having a cross-section formed by short line segments closely following an embodiment's curving subsurfaces will result in a cavity shape having perhaps only minor or theoretical deficiencies from that of the computationally perfect cavity shape. Accordingly, the foregoing description and figures are illustrative only and are not meant to limit the scope the invention, which is defined by the claims.
054250633	claims	1. An apparatus for simultaneous quantitative production and sequential recovery of [.sup.13 N]NH.sub.3 and [.sup.18 F]F.sup.-, comprising: a proton source for providing a beam of protons, a target cell containing low-enriched [.sup.18 O]H.sub.2 O target water for irradiation by said proton beam, anion separation means, serially connected to the target cell, through which said target water may be passed for removing [.sup.13 N]NO.sub.x.sup.- and [.sup.18 F]F.sup.- from the target water, [.sup.18 F]F.sup.- eluting means, serially connected to an input of the anion separation means, by a valving means comprising a first eluant reservoir including a first eluant for selective elution of [.sup.18 F]F.sup.- from the anion separation means as a collectable [.sup.18 F]F.sup.- fraction, and [.sup.13 N]NO.sub.x.sup.- eluting means, serially connected to an input of the anion separation means, by a valving means comprising a second eluant reservoir including a second eluant for selective elution of [.sup.13 N]NO.sub.x.sup.- from the anion separation means as a collectable [.sup.13 N]NO.sub.x.sup.- fraction means for separately and sequentially connecting each of said [.sup.18 F]F.sup.- eluting means and said [.sup.13 N]NO.sub.x.sup.- eluting means to said input of said anion separation means, whereby exposure of low-enriched [.sup.18 O]H.sub.2 O target water in the target cell to proton irradiation simultaneously produces [.sup.13 N]NO.sub.x.sup.- and [.sup.18 F]F.sup.- in quantitatively recoverable amounts usable for radiotracer synthesis for PET imaging. basifying means, serially connected to an output of the anion separation means for rendering the [.sup.13 N]NO.sub.x.sup.- fraction alkaline to yield a basic [.sup.13 N]NO.sub.x.sup.- fraction, and reducing means, serially connected to an output of the basifying means, for reducing the basic [.sup.13 N]NO.sub.x.sup.- fraction to yield collectable [.sup.13 N]NH.sub.3. 2. The apparatus of claim 1, further comprising a target water recovery reservoir, serially connected to an output of the anion separation means, such that target water can be recovered once [.sup.13 N]NO.sub.x.sup.- and [.sup.18 F]F.sup.- have been removed. 3. The apparatus of claim 1, wherein the target cell is further adapted to receive proton irradiation from at least one proton beam having a beam energy of between about 10 MeV and about 30 MeV. 4. The apparatus of claim 1, wherein the anion separation means comprises an anion exchange column containing particulate anion exchange resin having quaternary ammonium functional groups having the formula: ##STR2## wherein X is a polymeric support resin and R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently selected from the group consisting of hydrogen, and alkyl groups having 1 to 4 carbons. 5. The apparatus of claim 4, wherein the functional groups have the formula: EQU X--CH.sub.2 --N--(CH.sub.3).sub.3, 6. The apparatus of claim 1, wherein the [.sup.18 F]F.sup.- eluting means includes the first eluant as aqueous 0.01M K.sub.2 CO.sub.3. 7. The apparatus of claim 1, wherein the [.sup.13 N]NO.sub.x.sup.- eluting means includes the second eluant as aqueous 1N HCl. 8. The apparatus of claim 1, further comprising: 9. The apparatus of claim 8, wherein the basifying means includes a strong base. 10. The apparatus of claim 9, wherein the strong base includes aqueous 2N NaOH. 11. The apparatus of claim 8, wherein the reducing means includes DeVarda's alloy.
	abstract	An injection system designed to deliver a chemical solution into a reactor through feedwater system taps during normal operating condition of a power reactor is disclosed. The process of delivery is via positive displacement pumps. Injection of chemical is in a concentrated solution form, which is internally diluted by the system prior to discharging from the skid. The injection system minimizes chemical loss due to deposition on the transit line, enables a higher concentrated solution to be used as the injectant, eliminates the time consuming laborious process of chemical dilution, raises chemical solution to the pressure required for injection, prevents solid precipitations out of solution at the injection pump head through the use of a flush solution, and deposits fresh chemical on new crack surfaces that develop during a power reactor start-up, shutdown and operation.
	claims	1. An X-ray target, comprising:a first cap layer;a target layer composed of a material capable of generating characteristic X-rays, said target layer formed under said first cap layer; anda second cap layer formed under said target layer; anda support block formed under said second cap layer to hold said structure, wherein a first material of which said first and second cap layers are composed is lower in electron beam absorptivity than a second material of which said target layer is composed, said target layer is buried and arranged in the form of a linear or an elliptical matrix in said first and the second cap layer, and each target layer of said matrix is made a microfocus X-ray source corresponding to its size. 2. The X-ray target as set forth in claim 1, wherein said target layer is composed of a material capable of generating characteristic X-rays of a wavelength ranging between 0.3 and 10 Å. 3. The X-ray target as set forth in claim 1, wherein said first and second cap layers are composed of a material selected from the group which consists of B, C, SiC and B4C. 4. The X-ray target as set forth in claim 1, wherein said target layers are of an identical size. 5. The X-ray target as set forth in claim 1, wherein said target layers are varied in size. 6. The X-ray target as set forth in claim 1, wherein on the first cap layer is provided an antistatic layer. 7. An X-ray apparatus comprising:an X-ray source made of an electron beam generating section andan X-ray target, wherein said X-ray target comprisesa first cap layer,a target layer, anda second cap layer, wherein said first cap layer, said target layer, and said second cap layer are successively laminated in the recited order, thereby forming a laminated structure, anda support block to hold said laminated structure, wherein said first and second cap layers are composed of a first material which is lower in electron beam absorptivity than a second material of which said target layer is composed, said target layer is buried and arranged in the form of a linear or an elliptical matrix in said first and second cap layers, and each target layer of the matrix forms a microfocus X-ray source corresponding to its size, wherein each target of said matrix is irradiated with a convergent electron beam generated by said electron beam generating section to cause said target to generate a microfocus X-rays. 8. The X-ray apparatus as set forth in claim 7, wherein said electron beam generating section comprises an electronic lens, said X-ray target is disposed with an inclination to the convergent electron beam generated by said electron beam generating section, and said convergent electron beam is similar in shape and size to each target layer of said matrix. 9. The X-ray apparatus as set forth in claim 7, wherein on said first cap layer is provided an antistatic layer. 10. The X-ray apparatus as set forth in claim 7, wherein said X-ray apparatus is an X-ray diffraction apparatus further provided with an observation sample holder section and an X-ray detecting means. 11. The X-ray apparatus as set forth in claim 7, wherein said X-ray apparatus is a fluorescent X-ray analysis apparatus further provided with an observation sample holder section and an X-ray detecting means. 12. The X-ray apparatus as set forth in claim 7, wherein said X-ray apparatus is further provided with an X-ray optical element. 13. An X-ray microscope comprising:an electron beam generating section,an X-ray target,an observation sample holder section for an observable object, and an X-ray detecting means,wherein said X-ray target comprises:a first cap layer,a target layer, anda second cap layer, wherein said first cap layer, said target layer, and said second cap layer are successively laminated in the recited order, thereby forming a laminated structure,wherein said first and second cap layers are composed of a material which is lower in electron beam absorptivity than that of which said target layer is composed,wherein said X-ray target is irradiated with a convergent electron beam generated by said electron beam generating section to cause said target to generate microfocus X-rays, and said microfocus X-rays are used as divergent X-rays to obtain a transmission X-ray image of said observable object. 14. The X-ray microscope as set forth in claim 13, wherein said electron beam generating section includes an electronic lens, said X-ray target is disposed with an inclination to the convergent electron beam generated by said electron beam generating section, and said convergent electron beam is similar in shape and size to each target layer of the matrix of the X-ray target. 15. The X-ray microscope as set forth in claim 13, wherein on said first cap layer is provided an antistatic layer. 16. The X-ray microscope as set forth in claim 13, wherein said transmission X-ray image includes a contrast by phase contrast. 17. The X-ray microscope as set forth in claim 13, wherein said X-ray detecting means is an image sensor and provided with an image processing means for said image sensor, and X-rays are used as divergent X-rays to obtain a transmission X-ray image of said observable object.
047298650	description	DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In connection with the detailed description of the structure and operation of the present invention, it is to be understood that dimensions and values set forth are illustrative only and may be greater or lesser depending upon the size of reactor and the output desired. Referring in particular to the drawings and first to FIGS. 1 and 2, two large toroidal electromagnets 4 are provided which are opposite hand to each other and both of which possess horseshoe-type cross sections with the openings containing longitudinal superconducting winding means 5. The large electromagnets are vertically positioned one below the other as shown in FIG. 2 such that a continuous flow of magnetic flux will pass through a toroidal metallic wave guide 6 of rectangular cross section which is positioned between them, this occurring all along the entire circumference of all three structures. This continuous flow of magnetic flux, as indicated by the straight arrows A in FIG. 2, passes downward through half of the wave guide 6 cross section and upward through the opposite half, forming the boundary 7 between the two parts of the magnetic field. When the wave guide 6 is curving as in the present case the inner magnetic poles must extend wider inwardly to cause the inner magnetic field A to be slightly weaker than the outer magnetic field. Very narrow but closely spaced ferromagnetic by-pass vanes 8 extend downward and outward from the lower ends of both vertical surfaces of the upper electromagnet 4, and upward and outward from the vertical surfaces of the lower electromagnet, with the vanes spaced equidistantly to pass between each other. Only a representative number of these vanes 8 are shown in FIG. 3 but it is to be understood that they are equally spaced around the entire wave guide. The ends of the ferromagnetic by-pass vanes 8 are curved in toward the wall guide 6, terminating with their end surfaces positioned against the wave guide and well beyond the midpoint of its vertical surfaces, as shown in FIG. 2. Spaces between the vanes contain a lattice of support material, and should magnetic flux leakage between parallel, opposite-hand components prove to be extreme the vanes might appear as fanlike structures at the ends of solid ferromagnetic bars such that opposite-hand components are well separated. The by-pass vanes 8 present a considerably shorter magnetic flux path and produce a type of composite magnetic field across all four corners of the toroidal wave guide cross section, consisting of very narrow, concentrated, curving segments of magnetic field as indicated by the curved arrows B in FIG. 2, spaced between much wider, weaker layers of vertical containment field as indicated by the straight arrows A, with opposite-hand components being equidistantly staggered. A plurality of equally spaced oscillator probes 9 from oscillators 10 are positioned about the entire circumference of the toroidal wave guide 6, extending to its entire surface. The probes 9 provide a type of transverse electromagnetic coupling between a pulsating plasma within the wave guide and the oscillators 10 with the plasma assuming the function of an internal coaxial cable. The volume enclosed by the wave guide 6 is a vacuum, produced by conventional vacuum pumps. Ringlike lithium blankets 11 extend horizontally inward and outward from the toroidal wave guide 6 with a vertical thickness equal to the height of the waver guide, as shown schematically in FIG. 1. A representative size for the toroidal wave guide 6 is 26 cm wide by 34 cm high internally with a mean circumference of 7.5 meters. A representative outer magnetic field A is 33.2 kG with a 29.8 kG inner magnetic field serving to balance the plasma pulsations. A representative spacing for the ferromagnetic by-pass vanes 8 is 1 cm with a vane thickness narrowing to 1 mm at their end surfaces. A representative reactor shape is a toroid with a mean circumference equal to an odd number of wavelengths of the plasma pulsation frequency. In initiating operation of the system, 2.25 MeV deuterons are injected tangentially into the wave guide 6 by the deuteron accelerator 12, at the midpoint of its vertical surfaces. Some of the vanes 8 will be outwardly distorted somewhat to allow the ions to be injected. The deuterons, designated by the numeral 13 in FIG. 3, intersect the magnetic field boundary 7 at the center of the wave guide 6 with 108.degree. intersection angles 14, and are caused to oscillate in circular arc lengths along the wave guide 6 with amplitudes of 12 cm and with frequencies of 20 MHz. If the mean circumference of the wave guide 6 is selected to be 7.5 meters the ions will spontaneously arrange themselves into two narrow, oppositely-phased groups, constituting a horizontally pulsating, self-bombarding wave, resonating around the toroidal wave guide 6 with a frequency of 40 MHz and with a free-space phase velocity. These groups of oscillating ions, shown as they would appear at the plasma outer pulsation node reduced to 100 keV energy levels and with ignition widths, are indicated by the numeral 21 in FIG. 2. the resonating ionic wave perpetuates itself by continuously reincorporating the oscillating ions to beta-1 densities counter to their own coulomb scattering, largely because the oscillating ions maintain similar amplitudes and develop a pulsating self-field which increases outwardly within each narrow group of ions 21 and which continuously maintains its stability. Electrons from an incandescent wire are distributed through the plasma along the boundary 7 between the oppositely-directed magnetic fields A and move horizontally inward and outward within the narrow, resonating groups of ions 21 under the influence of microwave frequency electric fields, and axially in the same manner because of the inductance of the rapidly converging and diverging ionic wave. The magnetic viscosity of the oppositely-directed magnetic fields A forces the electrons to arrange themselves into systems of parallel charges pulsating at cyclatron frequencies parallel to the wave guide 6, producing highly organized microwave patterns which propagate within the beta-1 ionic wave as multiple harmonics of the plasma pulsation frequency, and which enable the electrons to ratchet their way rapidly across the magnetic field lines. Why should this scenario evolve and not any one of a million others? Because it becomes established at optical plasma densities and because it is the only system other than purely random which can achieve a stabilized continuation within the given parameters. Plasmas are not observed to spontaneously revert to random conditions and an exact adherence during early stages is not required. The electrons most likely move in the required precise numerical flow only when the microwave electric fields locally exceed the oppositely-directed magnetic fields A, and when their accompanying J.times.B behavior locally nullifies and doubles the magnetic fields A, and the microwave component of the resonating plasma pulsations causes the vertical magnetic field lines to vibrate like violin strings at GHz frequencies. The slightest departure from a precise numerical electron flow results in powerful electric fields which then propagate within the plasma with phase velocities appropriate to the resonating plasma pulsations, reinforcing and canceling each other until the proper microwave patterns are obtained to produce the required electron flow. The individually oscillating electrons must execute collectively coordinated, drifting-elliptical mode shapes in the process of ratcheting across the 33.2 KG magnetic fields A at the 40 MHz plasma pulsation frequency, which tends to reduce them all to the same temperature and which largely reduces their motions to horizontal planes. The unimpeded resonance establishes a situation in which every particle, including instantaneous scattering distributions, is arranged into some type of coordinated pattern, leaving nothing to be unstable. The microwave patterns actually constitute a type of powerful plasma self-field which eliminates rather than overcomes portions of the internal plasma pressure. Microwaves escaping from the plasma propagate within the metallic wave guide as powerful ionizing agents which prevent the backstreaming of thermal velocity neutral particles into the plasma, except in shielded collection channels leading to the vacuum pumps. The theory is that electrons correlated into extremely powerful microwave-sustaining patterns in maintaining normal charge and induction equilibriums can only produce a greatly reduced plasma pressure and syncrotron radiation of a corresponding lower power density. The microwaves are contained within the pulsating plasma and within the metallic wave guide 6, and locally concentrate and disperse the vertical magnetic fields A, causing the oscillating plasma ions to jiggle, and transferring large amounts of energy from the pulsating electrons to the oscillating plasma ions. In an electromagnetically resonating plasma equilibriums tend to be established by charge velocities in addition to particle energy levels. The energy is returned to the electrons through ionic collisions but the resulting massive circulating energy flow results in a uniform, greatly reduced electron temperature and a further reduction of all types of plasma radiation energy losses, with the possibility of using advanced fusion fuels. A large portion of the plasma radiation energy losses might be reabsorbed in passing outwardly through the concentrated microwave beams produced by the coordinated electron charges pulsating parallel to the wave guide 6. Suppose, as an example, that the oppositely-directed magnetic fields A were increased from 33.2 kG to 40 kG. What happens to the plasma pulsations? The intersection angle 14 of the oscillating deuterons at the center of the wave guide 6 simply increases to 130.degree., their amplitudes increase slightly when the intersection angle remains less than 135.degree., and the particles continue to resonate at about 20MHz. If the magnetic fields A are reduced to 26.4 kG the intersection angle 14 decreases to 86.degree., their amplitudes decrease slightly in retaining the proper periods, and the particles continue to resonate at about 20 MHz. Increasing or decreasing the energy levels of the particles increases or decreases their amplitudes without greatly affecting their intersection angles, as in a cyclotron. Consider an ion oscillating horizontally in phase with the plasma pulsations, possessing a modest vertical velocity, and entering a pair of composite magnetic fields at the top or bottom of the wave guide 6. The horizontal components of the narrow, curving magnetic fields B convert the vertical velocity of the ion into horizontal velocity and the amplitude of the ion tends to increase while it remains in phase with the horizontal plasma pulsations. But the vertical components of the curving magnetic fields B decrease the horizontal amplitude of the ion, and its intersection angle 14 increases and then decreases as the ion moves into and exits from the composite magnetic fields. The vertically oscillating ion generally exits from the composite fields leading the plasma pulsations but moves back into phase at the vertical midpoint of the wave guide 6 because of a generally increased intersection angle 14. The ion enters the alternate composite fields trailing the plasma pulsations, moves back into phase at its point of maximum penetration, exits from the composite fields leading the plasma pulsations, and moves back into phase at the vertical midpoint of the wave guide 6. A vertically oscillating ion will thus develop a slightly larger average intersection angle 14 and will continuously teeter slightly out of phase in both directions with the resonating plasma pulsations. But the resonating plasma pulsations continuously manipulate the vertically oscillating ions in both directions, particularly while their intersection angles are changing, in an attempt to reincorporate them back into phase, resulting in an immediate and powerful damping of the vertical components of the ionic oscillations, and the ions contain themselves within the modest magnetic fields A and B. This is actually a controlled application of the type of behavior which occurs randomly in unstable plasmas - energy flows into structured configurations. A powerful, horizontally resonating composite wave of enormous power density must be visualized as drawing energy out of the vertical components of its particle oscillations, particularly where pulsating, outwardly-increasing self-fields exist within the plasma. This damping phenomenon must not be confused with the typical reflection of particle velocities that occurs in a standard mirror machine. A designer of choke-field magnets would note that the composite fields will not contain a particle of determined vertical velocity. Such velocities are not obtainable through the statistical accretion of a large number of small-angle coulomb collisions. Large-angle collisions between reactive particles such as two tritons tend to result in fusion events, particularly in this structured environment. Collisions with helium ash tend to scavenge an alpha particle in one direction with the loss of a deuteron or a triton in the other. The elliptical, constantly changing mode shapes assumed by the pulsating electrons in their horizontal microwave orientation actively damp vertical electron oscillations and allow the electrons to be contained within their own modest electrostatic field in a manner similar to the vertical ionic containment. The higher propensity of the electrons to scatter is compensated by the higher frequency of the damping mechanism, and by the uniform, greatly reduced electron temperature. It is possible to consider the arc lengths of all the various ions oscillating in phase to be partial individual turns in a sinusoidal transformer operating at 40 MHz, similar to what occurs between the electrons and the patterned microwaves. Each of the ionized particles contributes to an induced electron flow at the plasma outer pulsation node as a function of its charge, velocity, and intersection angle, and receives slightly-more-average electron inductances as the plasma proceeds to its inner pulsation node. Each particle is rapidly reduced to the vicinity of the mean amplitude and energy level of that type of particle including replacement electrons, newly introduced deuterons and tritons, and suprathermal alpha particles as they are reduced to the mean energy level of the oscillating helium ash. In theory this transformer effect would rapidly reduce both the amplitudes and the energy levels of the narrow groups of doubly-charged, oscillating helium ash to half that of the oscillating deuterons while the groups of tritons would become several times more energetic because of their smaller velocities and intersection angles. The helium ash might be readily scavenged at low temperatures out the ends of the composite fields. It will be later shown that half of the collisions between deuterons and tritons occur from a head-on direction while the other half are from the rear, offset 36.degree. to the side - advantage deuterons. Half of the collisions between deuterons and alpha particles occur from a head-on direction, offset 36.degree. to the side, while the other half are from the rear - advantage alpha particles. Half of the collisions between tritons and alpha particles occure from a head-on direction, while the other half are from the rear, offset 36.degree. to the side-advantage tritons. The summation of all of this appears to indicate the scavengement of the helium ash by the energetic tritons, and an excellent plasma containment. The plasma pulsations also induce an alternating voltage in the wave guide 6, which sees the plasma as an internal coaxial cable, with its charge separations and pulsating self-field constituting a type of transverse electromagnetic wave. This alternating voltage constitutes the input impulses in the axially distributed oscillators 10, which also produce a type of powerful, unidirectional, 40 MHz transverse electromagnetic wave in the wave guide 6, with the plasma radiation energy losses producing the equivalent of powerful Q losses in the wave guide 6. The powerfully resonating plasma pulsations may be compared to a giant, nuclear-driven oscillator which produces a reverse-voltage counter to the oscillator impulses and which increases with ionic density and energy levels. This voltage is due to ohmic impedance reducing the induced electron flow, which produces a pulsating self-field and an alternating electric field in the plasma. During an initial start-up procedure the oscillator voltage is maintained above that of the pulsating plasma, energy flows into the wave guide 6, and the particle energy levels are maintained until an ignition density is obtained. After ignition has been achieved the situation is reversed and energy is continuously removed from the pulsating alpha particle halo through the oscillators 10 to maintain an optimal collision energy level for the narrow, beta-1 groups of head-on colliding tritons and deuterons which widen out with increasing plasma density. Returning again to the start-up procedure, the developing ionic wave assumes similar particle velocities and amplitudes about some rapidly decreasing energy level, which then becomes stabilized at between 100 and 200 keV by the introduction of a relatively small amount of energy from the oscillators 10. The primary purpose of the 2.25 MeV deutron accelerator 12 is to produce a powerfully resonating, beta-1 composite wave and to develop its microwave component into an effective ionizing medium. 100 keV neutral deuterium and tritium beams are tangentially injected slightly inward from the centerline of the wave guide 6 by the injectors 15 and 16, the beam particles become ionized within about 4 cm of the magnetic field boundary 7, and the ions arrange themselves at the proper intersection angles to allow them to become incorporated into the resonating plasma pulsations. The injected 100 keV deuterons, designated by the numeral 17 in FIG. 3, arrange themselves at about the same 108.degree. intersection angle 14 as the 2.25 MeV deuterons 13, but the injected 100 keV tritons, designated by the numeral 18 in FIG. 3, arrange themselves at a 72.degree. intersection angle 19. This demonstrates how disparate particles can contribute to the same resonating fusioning wave while meeting in periodic head-on collisions at the center of the wave guide 6. The ionic oscillation frequencies actually decrease slightly with increasing particle energy levels and increase slightly with increasing intersection angles, causing 10 keV deuterons, for example, to resonate at higher frequencies than 100 keV tritons with their high axial velocities, and with most of the ions ending up with slightly different intersection angles 14 at the center of the wave guide 6. The composite magnetic fields contain the particles, the oscillators 10 provide a massive infusion of energy, and the neutral particle beam injectors increase the plasma density to achieve ignition, after which the magnetic fields A must be readjusted to achieve the maximum energy production in the existence of the various plasma self-fields. The neutral particle beam injectors can be used to maintain the plasma density through a smaller number of particles at a reduced energy level, but low energy replacement ions might be more efficiently drifted vertically into the resonating ionic wave from the ionizer 20 along the boundary 7 between the oppositely-directed magnetic fields A. The neutral particle beam injectors might be eliminated, with the plasma being raised to ignition energy levels solely by the oscillators 10. The density of the ionic wave at its inner pulsation node is not limited to a theoretical beta-1 value as determined by the reduced electron temperature and the microwave self-field. The oscillating deuterons, tritons, and alpha particles have different mean amplitudes and the beta-1 density of each doubles as opposite sides pass through each other. It might be possible to employ some type of catalyzed, slower reacting deuterium fuel. The narrow groups of ions 21 widen rapidly in the vicinity of the inner pulsation node due to plasma pressure and reconverge more slowly everywhere else due to their outwardly-increasing self-fields. The resulting ionic bellows-action literally pumps energy out of the electrons and would be very important in the burning of advanced fusion fuels. The resonating ions implode, pass through, and explode back to beta-1 vicinities while simultaneously producing lateral electron explosions, and each of the ions is periodically accelerated laterally across the resulting electric potentials which move with free-space phase velocities. The 72.degree. intersection angle 19 of the oscillating tritons increases their outwardly-increasing self-fields, which serves to increase their intersection angle 19, which then permits a smaller, more stable deuteron intersection angle 14. If the fusion fuel is properly polarized the 3.5 MeV alpha particles will be emitted at the plasma inner pulsation node in phase with the resonating plasma pulsations with the same intersection angle 14 as the oscillating deuterons and with 71% of the amplitude of a deuteron of an equal energy level. If the planes-of-action of the fusion events are assumed to be roughly horizontal the 3.5 MeV alpha particles will oscillate within the wave guide 6 with amplitudes of 11 cm and the 14 MeV neutrons will penetrate the vertical side walls of the wave guide and enter the inward and outward located lithium blankets 11 at angles corresponding to the intersection angle 19 of the oscillating tritons. Neutron damage is largely limited to the sides of the wave guide 6, the ferromagnetic by-pass vanes and supports 8, and the oscillator probes and cables 9. The various beta-1 groups of resonating ions 21 are supplemented by an internally pulsating halo of accelerating tritons and deuterons and by an externally pulsating halo of decelerating suprathermal alpha particles. The fusion reactor is capable of being converted to a catalyzed deuterium reaction at higher particle energy levels. The 33.2 kG magnetic field A is reduced to 24.6 kG to bring the resonating deuterons together with 80.degree. intersection angles 14, which then increase to perhaps 85.degree. due to the outwardly-increasing self-fields. Synthesized tritium ions would then oscillate with 53.3.degree. intersection angles, and sythesized helium-3 ions would oscillate with 106.6.degree. intersection angles. Alpha particles would oscillate with 80.degree. intersection angles, as would synthesized 3 MeV protons with twice the deuteron oscillation frequency. 14.6 MeV protons would be containable only if the oscillation frequencies and the 24.6 kG magnetic field A were doubled. Each type of ion would resonate in two beta-1 groups 21 with an energy level determined by a combination of the transformer effect, coulomb collisions, and the circulating microwave and ionic bellows-action energies. Interesting reactions can be made to occur when 13.5 MeV protons are injected into a 37 kG magnetic field A to produce a 120 MHz, 80.degree.-85.degree. resonating proton wave, maintained at 1 MeV by the oscillators 10. Ions of lithium, beryllium or boron could be drifted into such a plasma, but these reactions would not generally be self-supporting or even containable in this machine, except in the case of lithium-7 if the ionic bellows-action could keep the electrons cool. The massive, low velocity lithium ions would resonate in two beta-1 groups 21 with beginning intersection angles of 34.3.degree., which would then increase somewhat due to the powerful, outwardly-increasing self-fields. The density and reaction rate of the resonating lithium fuel would be determined by the final electron temperature. The 85.degree. intersection angle of the bombarding protons would produce pairs of 8.5 MeV alpha particles which would resonate in four distinct groups with 80.degree. intersection angles and with half the proton oscillation frequency. Half of the collisions between resonating plasma protons and alpha particles would occur at the plasma inner pulsation node, with half of these being from behind and half occurring from a forward direction. All of the collisions between protons and alpha particles occurring at distances from the plasma inner pulsation node would possess distinct forward-direction collision components, and the lithium fuel might also resonate in four distinct groups at half the proton oscillation frequency with beginning intersection angles of 68.6.degree.. In theory the alpha particle ash would consistently lose energy to both the plasma protons and the lithium ions until it would be scavenged at low temperatures out the ends of the composite fields. This would be very important from the standpoint of first wall loading and impurity suppression, and also in retaining an additional 2 MeV of energy within the plasma for each fusion event, which is applicable in principle for any fusion fuel. It is to be understood that the form of my invention herein shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention, or the scope of the subjoined claims.
	claims	1. A nuclear fuel storage cask comprising:an outer shell having a length extending from a first end to a second end of the outer shell positioned opposite the first end, the outer shell defining:an inner cavity circumscribed by the outer shell;an outer perimeter extending around the outer shell;an inner perimeter positioned inward from the outer perimeter and positioned between the outer perimeter and the inner cavity; anda cooling circuit extending along the length of the outer shell, the cooling circuit comprising an inner passage, and an outer passage positioned outward of and in fluid communication with the inner passage;a coolant positioned within the cooling circuit, wherein the coolant is configured to move through the inner passage, absorbing heat from the inner cavity of the outer shell, and the coolant is configured to move through the outer passage, dissipating heat through the outer perimeter of the outer shell; anda lid coupled to the outer shell, wherein the lid covers the inner cavity of the outer shell and the lid comprises a lid cooling circuit, the lid cooling circuit comprising a vapor passage and a lid outer passage distinct from one another, the lid outer passage positioned outward of the vapor passage, and a lid coolant positioned within the lid cooling circuit, wherein the lid coolant remains in the lid cooling circuit and circulates between the vapor passage and the lid outer passage. 2. The nuclear fuel storage cask of claim 1, wherein the inner passage of the cooling circuit is an annular inner passage extending circumferentially around the inner perimeter of the outer shell. 3. The nuclear fuel storage cask of claim 1, wherein the outer passage of the cooling circuit is an annular outer passage extending circumferentially around the inner passage of the cooling circuit. 4. The nuclear fuel storage cask of claim 1, further comprising an exit passage in fluid communication with the inner passage and the outer passage, wherein the exit passage is positioned at the first end of the outer shell and extends circumferentially around the outer shell. 5. The nuclear fuel storage cask of claim 1, further comprising an exit passage radially extending between the inner passage and the outer passage, wherein the exit passage extends radially along the length of the outer shell. 6. The nuclear fuel storage cask of claim 1, further comprising a return passage in fluid communication with the inner passage and the outer passage, wherein the return passage is positioned at the second end of the outer shell and extends circumferentially around the outer shell. 7. The nuclear fuel storage cask of claim 1, further comprising a return passage radially extending between the inner passage and the outer passage, wherein the return passage extends radially along the length of the outer shell. 8. The nuclear fuel storage cask of claim 1, wherein the lid further comprises a lid exit passage. 9. The nuclear fuel storage cask of claim 8, wherein the lid outer passage and the lid exit passage comprise a porous material along the passages. 10. A nuclear fuel storage cask comprising:an outer shell having a length extending from a first end to a second end of the outer shell positioned opposite the first end, the outer shell defining:an inner cavity circumscribed by the outer shell;an outer perimeter extending around the outer shell;an inner perimeter positioned inward from the outer perimeter and positioned between the outer perimeter and the inner cavity; anda cooling circuit extending along the length of the outer shell, the cooling circuit comprising an inner passage, and an outer passage positioned outward of and in fluid communication with the inner passage;a coolant positioned within the cooling circuit, wherein the coolant is configured to move through the inner passage, absorbing heat from the inner cavity of the outer shell, and the coolant is configured to move through the outer passage, dissipating heat through the outer perimeter of the outer shell; anda lid coupled to the outer shell, wherein the lid covers the inner cavity of the outer shell and comprises a heat pipe lid cooling circuit contained entirely within the lid, the cooling circuit comprising a central vapor passage surrounded by a wick and a lid coolant circulating between the vapor passage and wick, wherein the lid further comprises a lid coolant positioned within the lid cooling circuit.
	claims	1. A method of making axial alignment of a charged particle beam in a charged particle beam system for adjusting the axis of the beam by a first alignment coil that deflects the beam in a first direction and a second alignment coil that deflects the beam in a second direction crossing the first direction, irradiating a sample with the beam, detecting a signal emanating from the sample, and obtaining image data, said method comprising the steps of:obtaining at least first through sixth image data while varying acquisition conditions including a focal position of the beam on the sample in a direction of incidence, an excitation current in the first alignment coil, and an excitation current in the second alignment coil; andcalculating a value of the excitation current in the first alignment coil and a value of the excitation current in the second alignment coil for the axial alignment of the beam from the at least first through sixth image data obtained by the step of obtaining the image data;wherein during said step of obtaining the at least first through sixth image data,said first image data is obtained under conditions where said focal position is a first position, the value of the excitation current in said first alignment coil is a first electric current value, and the value of the excitation current in said second alignment coil is a second electric current value,said second image data is obtained under conditions where the focal position is a second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is the second electric current value,said third image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by a first incremental current value,said fourth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by the first incremental current value,said fifth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by varying the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value, andsaid sixth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is an electric current value obtained by varying the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value. 2. A method of making axial alignment of a charged particle beam as set forth in claim 1, wherein during said step of calculating the values, a first image displacement vector indicating an amount of positional deviation between the first image data and the second image data, a second image displacement vector indicating an amount of positional deviation between the third image data and the fourth image data, and a third image displacement vector indicating an amount of positional deviation between the fifth image data and the sixth image data are calculated, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through third image displacement vectors. 3. A method of making axial alignment of a charged particle beam as set forth in claim 2, wherein during said step of obtaining the at least first through sixth image data, seventh image data and eighth image data are also obtained, andwherein said seventh image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by a second incremental current value, and said eighth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by varying the first electric current value by the second incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value. 4. A method of making axial alignment of a charged particle beam as set forth in claim 3, wherein during said step of calculating the values, a fourth image displacement vector indicating an amount of positional deviation between the first image data and the seventh image data and a fifth image displacement vector indicating an amount of positional deviation between the first image data and the eighth image data are also calculated, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through fifth image displacement vectors. 5. A method of making axial alignment of a charged particle beam as set forth in claim 2, wherein during said step of calculating the values, a fourth image displacement vector indicating an amount of positional deviation between the first image data and the third image data and a fifth image displacement vector indicating an amount of positional deviation between the first image data and the fifth image data are also calculated, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through fifth image displacement vectors. 6. A charged particle beam system for adjusting the axis of a charged particle beam by a first alignment coil that deflects the beam in a first direction and a second alignment coil that deflects the beam in a second direction crossing the first direction, irradiating a sample with the beam, detecting a signal emanating from the sample, and obtaining image data, said charged particle beam system comprising:image data acquisition means for obtaining at least first through sixth image data while varying acquisition conditions including a focal position of the beam on the sample in the direction of incidence and excitation currents in the first and second alignment coils, respectively; andcomputing means for calculating values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the beam from the at least first through sixth image data obtained by the image data acquisition means;wherein said first image data is obtained under conditions where the focal position is a first position, the value of the excitation current in the first alignment coil is a first electric current value, and the value of the excitation current in the second alignment coil is a second electric current value,said second image data is obtained under conditions where the focal position is a second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is the second electric current value,said third image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by a first incremental current value,said fourth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by the first incremental current value,said fifth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is a value obtained by varying the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value, andsaid sixth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is an electric current value obtained by varying the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value. 7. A charged particle beam system as set forth in claim 6, wherein said computing means calculates a first image displacement vector indicating an amount of positional deviation between the first image data and the second image data, a second image displacement vector indicating an amount of positional deviation between the third image data and the fourth image data, and a third image displacement vector indicating an amount of positional deviation between the fifth image data and the sixth image data, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through third image displacement vectors. 8. A charged particle beam system as set forth in claim 7, wherein said image data acquisition means further obtains seventh and eighth image data, andwherein said seventh image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by a second incremental current value, said eighth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by varying the first electric current value by the second incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value. 9. A charged particle beam system as set forth in claim 8, wherein said computing means further calculates a fourth image displacement vector indicating an amount of positional deviation between the first image data and the seventh image data and a fifth image displacement vector indicating an amount of positional deviation between the first image data and the eighth image data, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through fifth image displacement vectors. 10. A charged particle beam system as set forth in claim 7, wherein said computing means further calculates a fourth image displacement vector indicating an amount of positional deviation between the first image data and the third image data and a fifth image displacement vector indicating an amount of positional deviation between the first image data and the fifth image data, and wherein values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through fifth image displacement vectors. 11. A charged particle beam system as set forth in any one of claims 6 to 10, wherein said image data acquisition means controls said focal position by controlling at least one of an accelerating voltage of a beam source producing the charged particle beam and a value of an excitation current in an objective lens. 12. A method of making axial alignment of a charged particle beam as set forth in any one of claims 2 to 5, wherein during said step of calculating the values, a decision is made as to whether the calculated first through third image displacement vectors are used to calculate the values of the excitation currents in the first and second alignment coils, respectively, and wherein if the decision is that the first through third image displacement vectors are not used for the calculations, at least one of magnification and field of view is varied and the first through sixth image data are again obtained. 13. A method of making axial alignment of a charged particle beam as set forth in claim 4, wherein during said step of calculating the values, a decision is made as to whether the calculated fourth and fifth image displacement vectors are used to calculate the values of the excitation currents in the first and second alignment coils, respectively, and wherein if the decision is that the fourth and fifth image displacement vectors are not used for the calculations, at least one of magnification and field of view is varied and the first through sixth image data are again obtained. 14. A method of making axial alignment of a charged particle beam as set forth in any one of claims 2 to 5, further comprising the steps of:obtaining two image data under conditions in which the values of the excitation currents in the first and second alignment coils, respectively, are calculated by said step of calculating the values and in which the two image data are obtained at different values of the focal position;calculating a sixth image displacement vector from these two image data; andmaking a second decision as to whether or not the sixth image displacement vector is greater in magnitude than the first image displacement vector;wherein if the second decision is that the sixth image displacement vector is greater in magnitude than the first image displacement vector, at least one of magnification and field of view is varied and the first through sixth image data are again obtained. 15. A method of making axial alignment of a charged particle beam in a charged particle beam system for adjusting the axis of the beam by a first alignment coil that deflects the beam in a first direction and a second alignment coil that deflects the beam in a second direction crossing the first direction, irradiating a sample with the beam, detecting a signal emanating from the sample, and obtaining image data, said method comprising the steps of:obtaining first through fifth image data under acquisition conditions where a focal position of the beam on the sample in the direction of incidence, an excitation current in the first alignment coil, and an excitation current in the second alignment coil are varied;obtaining sixth image data;calculating first through fourth image displacement vectors from the first through fifth image data;determining acquisition conditions under which seventh and eighth image data are obtained, based on the first through fourth image displacement vectors;obtaining the seventh and eighth image data based on the acquisition conditions determined by the determining step; andcalculating values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam from the first through eighth image data obtained by the steps of obtaining the first through eighth image data;wherein during said step of obtaining the first image data, said first image data is obtained under conditions where the focal position is a first position, the value of the excitation current in the first alignment coil is a first electric current value, and the value of the excitation current in the second alignment coil is a second electric current value,said second image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by varying the second electric current value by a first incremental current value,said third image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by incrementing the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value,said fourth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by decrementing the second electric current value by the first incremental current value, andsaid fifth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by decrementing the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value;wherein during said step of obtaining the second image data, said sixth image data is obtained under conditions where the focal position is a second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value in the excitation current in the second alignment coil is the second electric current value;wherein during said step of calculating the first through fourth image displacement vectors, said first image displacement vector indicating an amount of positional deviation between the first image data and the third image data, said second image displacement vector indicating an amount of positional deviation between the first image data and the second image data, said third image displacement vector indicating an amount of positional deviation between the first image data and the fifth image data, and said fourth image data displacement vector indicating an amount of positional deviation between the first image data and the fourth image data are calculated;wherein during said acquisition determining step, two adjacent vectors of a set are selected based on given conditions from the first through fourth image displacement vectors to thereby determine the values of the excitation currents in the second and first alignment coils, respectively, for the seventh and eighth image data, respectively; andwherein during said step of obtaining the seventh and eighth image data, the seventh image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value determined by the acquisition condition determining step, and the eighth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is an electric current value determined by the acquisition condition determining step, and the value of the excitation current in the second alignment coil is the second electric current value. 16. A method of making axial alignment of a charged particle beam as set forth in claim 15, wherein during said acquisition condition determining step, two adjacent angles of a set which make an angle closest to an angle made between said first direction and said second direction among sets of the first through fourth image displacement vectors are selected from these sets. 17. A method of making axial alignment of a charged particle beam as set forth in claim 15, wherein during said acquisition condition determining step, said set is selected from the sets of the first through fourth image displacement vectors based on a sum of magnitudes of two adjacent vectors of the set. 18. A method of making axial alignment of a charged particle beam as set forth in any one of claims 16 and 17, wherein during said step of calculating the values of the excitation currents in the first and second alignment coils,one of the second image data and the fourth image data is selected and one of the third image data and the fifth image data is selected based on the selected set,a fifth image displacement vector indicating an amount of positional deviation between the first image data and the sixth image data, a sixth image displacement vector indicating an amount of positional deviation between the selected one of the second and fourth image data and the seventh image data, and a seventh image displacement vector indicating an amount of positional deviation between the selected one of the third and fifth image data and the eighth image data are calculated, andthe values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated from the first through seventh image displacement vectors. 19. A charged particle beam system for adjusting the axis of a charged particle beam by a first alignment coil that deflects the beam in a first direction and a second alignment coil that deflects the beam in a second direction crossing the first direction, irradiating a sample with the beam, detecting a signal emanating from the sample, and obtaining image data, said charged particle beam system comprising:image data acquisition means for obtaining first through eighth image data while varying acquisition conditions including a focal position of the beam on the sample in the direction of incidence and excitation currents in the first and second alignment coils, respectively;image acquisition condition determining means for determining image acquisition conditions under which the seventh and eighth image data are obtained based on the first through fifth image data obtained by the image data acquisition means; andcomputing means for calculating values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam from the first through eighth image data obtained by the image data acquisition means;wherein said first image data is obtained under conditions where the focal position is a first position, the value of the excitation current in the first alignment coil is a first electric current value, and the value of the excitation current in the second alignment coil is a second electric current value,said second image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by incrementing the second electric current value by a first incremental current value,said third image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by incrementing the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value,said fourth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value obtained by decrementing the second electric current value by the first incremental current value,said fifth image data is obtained under conditions where the focal position is the first position, the value of the excitation current in the first alignment coil is an electric current value obtained by decrementing the first electric current value by the first incremental current value, and the value of the excitation current in the second alignment coil is the second electric current value,said sixth image data is obtained under conditions where the focal position is a second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is the second electric current value,said seventh image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is the first electric current value, and the value of the excitation current in the second alignment coil is an electric current value determined by said image acquisition condition determining means, andsaid eighth image data is obtained under conditions where the focal position is the second position, the value of the excitation current in the first alignment coil is an electric current value determined by the image acquisition condition determining means, and the value of the excitation current in the second alignment coil is the second electric current value;wherein said computing means calculates a first image displacement vector indicating an amount of positional deviation between the first image data and the third image data, a second image displacement vector indicating an amount of positional deviation between the first image data and the second image data, a third image displacement vector indicating an amount of positional deviation between the first image data and the fifth image data, and a fourth image displacement vector indicating an amount of positional deviation between the first image data and the fourth image data; andwherein said image acquisition condition determining means selects two adjacent vectors of a set from the first through fourth image displacement vectors based on given conditions to thereby determine values of excitation currents in the second and first alignment coils, respectively, for the seventh and eighth image data, respectively. 20. A charged particle beam system as set forth in claim 19, wherein said image acquisition condition determining means selects two adjacent vectors of a set which make an angle closest to an angle made between the first direction and the second direction among the sets of the first through fourth image displacement vectors from these sets. 21. A charged particle beam system as set forth in claim 19, wherein said image acquisition condition determining means selects the set from the sets of the first through fourth image displacement vectors based on a sum of magnitudes of the two adjacent vectors of the set. 22. A charged particle beam system as set forth in one of claims 20 and 21, wherein said computing meansselects one of the second image data and the fourth image data and selects one of the third image data and the fifth image data based on the selected set,calculates a fifth image displacement vector indicating an amount of positional deviation between the first image data and the sixth image data, a sixth image displacement vector indicating an amount of positional deviation between the selected one of the second image data and the fourth image data and the seventh image data, and a seventh image displacement vector indicating an amount of positional deviation between the selected one of the third image data and the fifth image data and the eighth image data, andcalculates values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam from the first through seventh image displacement vectors. 23. A method of making axial alignment of a charged particle beam as set forth in any one of claims 2 to 5, 13, and 15 to 17, further comprising the step of making a first decision as to whether or not an image displacement vector calculated from two image data which are different only in the focal position is greater than a given value, and wherein if the first decision is that the image displacement vector is greater than the given value, values of the excitation currents in the first and second alignment coils, respectively, for the axial alignment of the charged particle beam are calculated.
047388196	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIGS. 1 to 7, there is shown a prior art nuclear fuel assembly, generally designated 10, for a BWR to which the improved features of the present invention can be advantageously applied. The fuel assembly 10 includes an elongated outer tubular flow channel 12 that extends along substantially the entire length of the fuel assembly 10 and interconnects an upper support fixture or top nozzle 14 with a lower base or bottom nozzle 16. The bottom nozzle 16 which serves as an inlet for coolant flow into the outer channel 12 of the fuel assembly 10 includes a plurality of legs 18 for guiding the bottom nozzle 16 and the fuel assembly 10 into a reactor core support plate (not shown) or into fuel storage racks, for example in a spent fuel pool. The outer flow channel 12 generally of rectangular cross-section is made up of four interconnected vertical walls 20 each being displaced about ninety degrees one from the next. Formed in a spaced apart relationship in, an extending in a vertical row at a central location along, the inner surface of each wall 20 of the outer flow channel 12, is a plurality of structural ribs 22. The outer flow channel 12, and thus the ribs 22 formed therein, are preferably formed from a metal material, such as an alloy of zirconium, commonly referred to as Zircaloy. Above the upper ends of the structural ribs 22, a plurality of upwardly-extending attachment studs 24 fixed on the walls 20 of the outer flow channel 12 are used to interconnect the top nozzle 14 to the channel 12. For improving neutron moderation and economy, a hollow water cross, generally designated 26, extends axially through the outer channel 12 so as to provide an open inner channel 28 for subcooled moderator flow through the fuel assembly 10 and to divide the fuel assembly into four, separate, elongated compartments 30. The water cross 26 has a plurality of four radial panels 32 composed by a plurality of four, elongated, generally L-shaped, metal angles or sheet members 34 that extend generally along the entire length of the channel 12 and are interconnected and spaced apart by a series of elements in the form of dimples 36 formed in the sheet members 34 of each panel 32 and extending therebetween The dimples 36 are formed in and disposed in a vertical column (FIG. 6) along the axial length of the sheet members 34. Preferably, the dimples 36 in each of the sheet members 34 are laterally and vertically aligned with corresponding dimples 36 in adjacent sheet members 34 in order to provide pairs of opposed dimples that contact each other along the lengths of the sheet members to maintain the facing portions of the members in a proper spaced-apart relationship. The pairs of contacting dimples 36 are connected together such as by welding to ensure that the spacing between the sheet members 34 forming the panels 32 of the central water cross 26 is accurately maintained. The hollow water cross 26 is mounted to the angularly-displaced walls 20 of the outer channel 12. Preferably, the outer, elongated longitudinal edges 38 of the panels 32 of the water cross 26 are connected such as by welding to the structural ribs 22 along the lengths thereof in order to securely retain the water cross 26 in its desired central position within the fuel assembly 10. Further, the inner ends of the panels together with the outer ends thereof define the inner central cruciform channel 28 which extends the axial length of the hollow water cross 26. Disposed within the channel 12 is a bundle of fuel rods 40 which, in the illustrated embodiment, number sixty-four and form a 8.times.8 array. The fuel rod bundle is, in turn, separated into four mini-bundles thereof by the water cross 26. The fuel rods 40 of each mini-bundle, such being sixteen in number in a 4.times.4 array, extend in laterally spaced apart relationship between an upper tie plate 42 and a lower tie plate 44 and connected together with the tie plates comprise a separate fuel rod subassembly 46 within each of the compartments 30 of the channel 12. A plurality of grids or spacers 48 axially spaced along the fuel rods 40 of each fuel rod subassembly 46 maintain the fuel rods in their laterally spaced relationships. Coolant flow paths and cross-flow communication are provided between the fuel rod subassemblies 46 in the respective separate compartments 30 of the fuel assembly 10 by a plurality of openings 50 formed between each of the structural ribs 22 along the lengths thereof. Coolant flow through the openings 50 serves to equalize the hydraulic pressure between the four separate compartments 30, thereby minimizing the possibility of thermal hydrodynamic instability between the separate fuel rod subassemblies 46. The above-described basic components of the BWR fuel assembly 10 are known in the prior art, being disclosed particularly in the patent applications cross-referenced above, and have been discussed in sufficient detail herein to enable one skilled in the art to understand the improvements of the present invention presented hereinafter. For a more detailed description of the construction of the BWR fuel assembly, attention is directed to both of the above cross-referenced Barry et al and Doshi patent applications. Features for Avoiding CHF Performance Degradation While the openings 50 allow improved flow stability and pressure equalization, analysis shows that at the spacer locations sharp changes in pressure gradients raise the cross-flow levels between the mini-bundle subassemblies 46 by more than 100 times the nominal cross-flows, becoming comparable to axial mass flow rates in the separate mini-bundle subchannels or compartments 30. This is a large number which can affect and degrade the predicted CHF margin by five to ten percent depending on the operating conditions. Data shows that such undesirable cross-flow behavior around the locations of the spacers 48 washes off beyond plus or minus approximately three inches of the spacer location. Also, in a BWR, CHF occurs predominantly at the top three spacer locations. Thus, the solution of the present invention is to provide means for blocking lateral flow around the top three spacer locations, at least up to three inches in either direction. More particularly, two different embodiments of the features of the present invention for accomplishing lateral cross-flow blockage and thereby eliminating or minimizing CHF performance degradation are shown in FIGS. 8 and 9 incorporated in respective BWR fuel assemblies 10A and 10B. The same parts of the fuel assemblies 10A,10B as described previously with respect to the prior art fuel assembly 10 are identified with the same reference numerals but with the addition of either an A or B suffix depending upon whether the part identified is in the fuel assembly 10A or in the fuel assembly 10B. As seen in FIGS. 8 and 9, each of the respective blocking means which interconnects each water cross radial panel 32A,32B and channel 12A, 12B for closing predetermined ones of the openings 50A,50B at upper ones of the spacers 48A,48B is in the form of a solid continuous structure impervious to cross-flow of moderator/coolant fluid. Specifically, in FIG. 8 the blocking means is a continuous rib 52 formed in the channel 12A and connected to a respective one of the water cross radial panels 32A. Each rib 52 extends along the channel 12A through a distance which encompasses the levels or regions of the adjacent subassemblies 46A occupied by the upper ones of the spacers 48A, preferably the upper three of the spacers 48A. In FIG. 9, the blocking means is a continuous weld or bar 54 interconnecting the channel 12B with a respective one of the water cross radial panels 32B, which covers the same distance as the ribs 52 of FIG. 8. Due to the continuous connection provided between the water cross panels and the channel at the top three spacer locations or the BWR fuel assembly, it is believed that the water cross and channel will be better coupled and hence improvement in structural integrity can be expected. Also, elimination of large cross-flows at upper spacer locations would lead to an improvement in the area of flow induced structural vibrations. As discussed earlier, the impact on the disclosed BWR fuel assembly thermal hydraulic design would be vastly improved due to elimination of cross-flow related penalties and uncertainties and, as a consequence, allow for enormous reduction in analytical complexity by permitting one-dimensional thermal hydraulic analysis, rather than multi-dimensional analysis (which would require development, qualification and licensing of a code to handle it). It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
046817050	description	DETAILED DESCRIPTION As set forth earlier herein, prior to the present invention, it was believed that substantially all of the radioactivity present in waste lubricating oil was present in the aqueous portions of the oil/water emulsions which formed during the operation of certain typical types of machinery. Accordingly, it was similarly believed that the problem of decontaminating waste lubricating oil could be addressed simply by separating essentially pure oil from emulsions containing radioactive water. This has been found to be somewhat unsuccessful, however, as even after such separation techniques the resulting oil always has a significant enough radioactive contamination to require disposal as a radioactive low level waste. In contrast to all of these prior assumptions and methods, the present invention has developed under the more proper discovery that radioactivity present in the mixtures of water and waste lubricating oil formed as byproducts of the operation of a nuclear power plant has an organic component. This organic component tends to be substantially associated with the oil rather than with the aqueous portion of the mixture and thus is not removed when oil and water are separated regardless of the sophistication or effectiveness of the particular separation technique. Accordingly, the present invention is a method which has been developed for attacking and then removing the radioactive component present in the organic material as well as that present in the inorganic material in waste lubricating oil. The present invention is additionally novel in that contaminated oil is mixed with another material in order to accomplish the decontamination process. In almost all prior processes, it has been believed by those most familiar with the problem that physical separation techniques were required to decontaminate such oil and that any further mixing of such materials was an especially unattractive and unsatisfactory method of decontamination. Although the invention can be broadly applied to the decontamination of water-immiscible organic liquids, the decontamination of mixtures of water and water-immiscible organic liquids and the decontamination of mixtures of either of the above with particulate material, the embodiment described herein will refer to the decontamination of mixtures of water and waste lubricating oil produced during the normal operations of nuclear powered electric generating plants. According to the present invention, when any particulate matter is present in the waste oil, a first step in decontamination comprises separating the mixture of radioactively contaminated particulate material and a mixture of radioactively contaminated water and radioactively contaminated lubricating oil into an liquid mixture portion and a particulate portion. Such separation can be carried out by conventional means in a straightforward manner, such as filtration. The resulting particulate material, even if contaminated, can be disposed of as solid waste without the practical and regulatory problems set out earlier with respect to liquid waste. The thus separated liquid mixture is then separated into a waste water fraction carrying metal radionuclides and an organic liquid fraction carrying metal radionuclides. In one preferred embodiment of the invention, the separation is accomplished in a centrifugal separator, one commercial embodiment of which is an Alfa Laval 103B centrifuge, or an equivalent product. In order to enhance the separation of the waste water fraction from the lubricating oil fraction, the mixture may additionally be heated, preferably to a temperature of about 180.degree. F. Heating the mixture lowers the viscosity of the oil, improving its flow characteristics and enhancing the separation process. As in the case of the particulate material initially separated, the waste water fraction may be decontaminated by conventional methods such as selective precipitation or extraction which result in decontaminated water and low level solid waste which can be disposed of more conveniently than low level liquid waste. It will be apparent to those familiar with the problem and the industry that the use of existing commercial technology and materials in the present invention makes the invention attractive and useful for current application on a wide scale. In preferred embodiments of the invention, the separated contaminated oil fraction can be filtered at this stage to further remove any fine particulate material suspended therein which may not have been carried off in the separation from the waste water fraction. The contaminated oil fraction is then mixed with a sufficient amount of an aqueous solution of a water-soluble chelating agent in a manner and for a time period sufficient for water-soluble metal-chelate complexes to form between the chelating agent and substantially all of the metal radionuclides carried by the organic liquid fraction. Appropriate chelating agents are those organic molecules which contain enough functional groups, two or more, located in such positions on the molecule that when the functional groups attach to the metal ion with which they complex, they surround the metal ion and form a ring. In a preferred embodiment of the invention, one appropriate chelating agent is ethylenediamine tetraacetic acid (EDTA). EDTA forms stable, water-soluble complexes with many metal ions, can potentially bond to metal ions at as many as six different sites, and tends to result in the formation of five-membered chelate rings. Because the preferred embodiment of the invention relates to the decontamination of waste lubricating oil from a nuclear powered electric generating plant, the radionuclide which is characteristically most difficult to remove is Cobalt 60 (Co-60). EDTA is an especially attractive chelating agent for removing Cobalt 60, but the invention is equally applicable to situations in which other radionuclides need to be removed from either waste lubricating oil or some other water-immiscible organic liquid. In such circumstances, several other chelating agents may be appropriate. Typical chelating agents suitable for other radionuclides include the following: nitrilotriacetic acid, alpha-nitrosobeta-naphathol, 1,2-cyclohexanedionedioxime, disodium dihydrogen EDTA, ethylenediaminetetraacetate dihydrate, tetrasodiumethylenetiamine tetracetate, N-hydroxyethylethylenediaminetriacetic acid, and 4-(2-pyridylazo)-resorcinol. In another embodiment of the invention, the aqueous solution containing the chelating agent may also include a water soluble inorganic precipitating agent. When the aqueous solution contains an inorganic precipitating agent, insoluble metal precipitates may form between the precipitating agent and some of the metal radionuclides which are not affected by the chelating agent. In such cases, the metal precipitates will separate from the organic liquid fraction along with the aqueous solution after which the metal precipitates may in turn be separated from the aqueous solution before the aqueous solution is otherwise decontaminated. The invention thus provides a method whereby substantially all of the metal radionuclides may be removed from water immiscible organic liquids which contain some radionuclides which are more likely to complex with the chelating agent and which also contain other radionuclides which are less likely to form chelates but which will in turn be likely to precipitate out as insoluble salts of the inorganic precipitating agent. Typical appropriate inorganic precipitating agents include the following: NH.sub.4 OH, H.sub.2 S, (NH.sub.4).sub.2 S, (NH.sub.4).sub.2 HPO.sub.4, H.sub.2 SO.sub.4, H.sub.2 PtCl.sub.6, H.sub.2 C.sub.2 O.sub.4, (NH.sub.4).sub.2 MoO.sub.4, HCl, AgNO.sub.3, (NH.sub.4).sub.2 CO.sub.3, NH.sub.4 SCN, NaHCO.sub.3, HNO.sub.3, H.sub.5 IO.sub.6, NaCl, Pb(NO.sub.3).sub.2, BaCl.sub.2, NgCl.sub.2, and NH.sub.4 Cl. It is to be understood that the aforementioned chelating agents and inorganic precipitating agents are illustrative of the types of materials known by those familiar with this art and that while some examples have been given, the invention is not limited to these particular examples. As in the case of the initial separation of the mixture into an oil fraction and waste water fraction, the method of mixing the oil fraction with the chelating agent can give more satisfactory results. According to the present invention, it has been found that the mixing of the oil fraction with the aqueous solution of chelating agent can be best accomplished in a centrifuge similar to that used for separation, with the separation function of the centrifuge being switched over to a mixing function. Additionally, the mixing may be enhanced by heating the mixture during the mixing process. Additionally, as is known to those familiar with chelating agents, the acidity of a solution affects the chelating capability of the chelating agent. In the embodiment preferred for the removal of Co-60 with EDTA, best results are obtained when the mixture is kept at a pH greater than 7 with most preferable results being obtained with a pH of about 10.5. For the removal of other metals with EDTA, Co-60 with other chelating agents or other metals with other chelating agents, the optimum pH can be determined based on the chemical characteristics of both the particular chelating agent and those of the particular radionuclide to be removed. One further preferable characteristic of both the solution and the chelating agent is that the chelating agent selected be one which has a greater solubility in water than in the water immiscible organic liquid with which it is mixed. The relative solubility of EDTA in water and in oil is appropriate in this regard. In the embodiment of the invention preferred for removing Co-60 from waste lubricating oil, an EDTA concentration of 0.125 Molar (M) and a solution to oil ratio of 8% have been found to be most satisfactory. As presently best understood, of the radionuclides set out earlier which exist in the original waste mixtures of water and lubricating oil to be decontaminated, Co-60 generally dominates the total radioactivity of the oil fraction. Because waste lubricating oil, even when separated from an emulsion of waste water, always contains a residual measure of radioactivity, it is believed that the Co-60 forms organo-metallic complexes and other oil-soluble compositions which are not removed by any of the prior known techniques. According to the present invention, because EDTA is soluble both in water and in the oil component, Co-60 can be preferably encouraged to form EDTA complexes during the mixing process rather than forming or remaining a part of other organo-metallic compounds. When mixing is completed, the greater affinity of EDTA for water than for oil causes the EDTA to be preferably removed with the water and to carry with it the radioactive Co-60 originally picked up from the lubricating oil. Accordingly, after mixing the next step in the present invention comprises separating the aqueous solution of the chelating agent from the lubricating oil. This also can be accomplished by centrifugal separation and the aqueous fraction which results can be disposed of in a conventional manner. If so desired, the oil fraction may be filtered one more time to remove any further fine particulate material which may have been introduced and not removed to this point. The decontaminated lubricating oil, or other organic liquid, may then be disposed of in a conventional manner, preferably by burning. There are, of course, regulatory limits as to the amount of radioactivity that may be introduced into the atmosphere by the combustion of low level radioactive waste. One advantage of the present invention is that the method of decontamination set forth herein brings the contamination level of the oil to such a low level that combustion of the oil does not result in the release of any significant or prohibited amount of radioactivity into the atmosphere. To further reduce even these insignificant amounts, the waste oil decontaminated by the present method can be mixed with larger amounts of conventional fuel oil and burned in a conventional fuel boiler. It is to be understood that burning of waste lubricating oil decontaminated in the present manner is not the only conventional method of disposal and the scope of the invention or the claims is not to be considered as limited thereto. It will be further understood that while the preferred embodiment of the present invention has been described with regard to the decontamination of waste lubricating oil produced at nuclear powered electric generating plants, the invention is equally applicable to the decontamination of a number of radioactively contaminated water immiscible organic liquids. As in the case of waste lubricating oil, these liquids may be found alone, in mixtures, in water emulsions, in mixtures of water emulsions and particulate material or with particulate material alone. All of these various situations may be addressed by the method of the present invention and are to be considered within the scope of the description and the claims herein. Additionally, the foregoing embodiments are to be considered illustrative, rather than restrictive of the invention and those modifications which come within the meaning and range of equivalent of the claims are to be included therein.
	description	The instant application claims priority from U.S. patent application Ser. No. 15/677,098 filed Aug. 15, 2017, the disclosures of which are incorporated herein by reference. The disclosed and claimed concept relates generally to nuclear power generation equipment and, more particularly, to a detection apparatus and a method of use that are intended to evaluate the neutron absorption capability of control elements of BWR and PWR nuclear reactors. Various types of nuclear power generation systems are known to exist and are particularly known to include boiling water reactors (BWRs) and pressurized water reactors (PWRs). A BWR includes, among other components, a number of blades that are used as control elements that absorb neutrons and control the nuclear reaction within a reactor of a nuclear installation. As employed herein, the expression “a number of” and variations thereof shall refer broadly to any non-zero quantity, including a quantity of one. One such blade is depicted in an exemplary fashion in FIG. 1 at the numeral 6. Such blades and are configured to be of an elongated cruciform shape having a hub and four wings that protrude from the hub. The wings are structured to each be received between adjacent pairs of fuel assemblies to absorb neutrons in the water within which the fuel assemblies are situated. During normal operation of the BWR, the a substantial fraction of the blades typically are at least partially withdrawn from being situated between the fuel assemblies and can be, as needed, advanced further into a position situated between the adjacent pairs of fuel assemblies. The balance of the blades will be positioned partially to fully withdrawn as determined by the core reactivity management requirements as a function of the core depletion with exposure and the reactor thermal margin requirements. Such further insertion of the blades causes the blades into the reactor fuel region results in absorbing a greater number of neutrons, thereby slowing or controlling the nuclear reaction in a known fashion. The BWR control blades each include a plurality of elongated hollow passages that are filled with boron or other neutron absorbing substance and are capped. In one such type of blade design, the passages are oriented substantially perpendicular to the longitudinal extent of the hub and are formed by drilling holes in the edges of the wings. The holes are formed with boron or another neutron absorbing substance and are capped. In another such blade design, the blades are formed by providing elongated hollow tubes that each have an elongated passage that is filled with boron or another neutron absorbing and that is then capped at the ends, and then the tubes are laid side-by side and affixed together in any of a variety of fashions such as by covering the tubes with a sheet of metal to form the elongated cruciform shape. Over time, the passages in the blades that contain the boron or other neutron absorbing substance can develop defects in any of a variety of fashions. Such a defect will then allow the highly pressurized cooling water for the reactor into the space reserved for the absorbing material. The water intrusion into the neutron absorbing substance generally has the effect of washing away the absorbing material within the defective absorber tube, thereby leaving a region within the control bade partially or completely devoid of a neutron absorbing substance. The consequence is that the blade in the vicinity of such a breached passage does not absorb neutrons as required. This loss of absorption becomes significant from a safety and operational perspective when the defective portion of the control blade is large enough to either diminished the overall ability of the plurality of control blade insertions to extinguish the nuclear chain reaction within the reactor or results in unacceptable reactor power distributions and resulting loss of thermal margin. Over time, any given blade can have one or more locations thereon where the neutron absorbing substance is lacking due to such a defect, at which locations the blade does not absorb neutrons, and rather allows neutrons to pass directly therethrough. While a certain number of zones and/or a certain distribution of zones where neutrons pass directly through the blade can be deemed acceptable, the overall ability of the blade to absorb neutrons and to slow or otherwise control a nuclear reaction must not be compromised. As such, blades must be non-destructively examined once there are either visual or operational defect indications to assess their continued ability to effectively absorb neutrons and thereby meet the design and safety requirements. In one such prior inspection methodology, a neutron absorbing film is applied on one side of a wing and a neutron source is applied at the opposite side of the wing. Neutrons that are not absorbed and that rather pass through the wing at any given location thereon leave a telltale indication on the film at that location. A neutron source that has been used in such procedures employs californium 252, which is a neutron source that constantly emits neutrons and thus requires special shielding during transport and during certain portions of its use during an inspection procedure. After extensive exposure of the blades to the neutrons from the neutron source, the film would then be removed and examined, much in the way of X-ray film, for regions that include the telltale indication where neutrons had passed through the wing. The neutron absorption capability of the wing is then evaluated based upon an evaluation of the film. The use of such film has been cumbersome for a number of reasons, including the extended time frame to achieve meaningful film exposure that is required to quantify the blade effectiveness, the special shielding of the californium 252 neutron source that is required, and the extensive time that transpires between initiating the procedure and obtaining the results of the procedure. Improvements would thus be desirable. An improved detection apparatus is usable to detect the neutron absorption capability of a control element of a nuclear installation and includes a neutron radiograph apparatus and a robot apparatus. The neutron radiograph apparatus includes an neutron emission source, a detector array, and a mask apparatus. The neutron emission source is advantageously switchable between an ON state and OFF state and employs an accelerator that emits a deuterium particle at either another deuterium particle or a tritium particle to result in the generation of helium isotopes and excess neutrons by a nuclear fusion reaction. The neutron emission source thus does not require shielding during transport and is energized to the ON state only after being submerged to a certain depth in the fuel inspection pool, which avoids any need for additional personnel or apparatus shielding. The neutron emission source is situated at one side of a wing and generates a neutron stream, the detector array is situated on an opposite side of a wing, and the neutron emission source and detector array are robotically advanced along the wing. The detector array is monitored in real time to determine whether the detector array emits an output signal that is representative of a detection of a defect by measuring the neutron stream passing through the blade. If the detector array does not measure excessive transmission of neutrons through the wing anywhere along the length of the wing, that wing is deemed to have passed the inspection and to be acceptable. On the other hand, if the detector array at a given location on the wing detects the transmission of neutrons through the wing, various masks of the mask apparatus are positioned between the neutron emission source and the detector array to more specifically identify the position on the blade where the neutrons are passing through. Each mask is in the form of a plate-like neutron absorber having a small opening formed therein. By employing one or more masks and manipulating the one or more masks with robotic manipulators, the detector array can determine the precise position(s) on each wing where neutrons are detected as passing through the wing. Such processing can occur rapidly and, when completed, the results can be evaluated to determine whether or not that wing is passed or whether it is in need of replacement or repair. Accordingly, an aspect of the disclosed and claimed concept is to provide an improved detection device that is usable to detect and evaluate the neutron absorption capability of a control element of a nuclear installation. Another aspect of the disclosed and claimed concept is to provide an improved method of operating such a detection apparatus in the detection and evaluation a neutron absorption capability of a control element of a nuclear installation. Another aspect of the disclosed and claimed concept is to provide such a device and method that enable the neutron absorption properties of a blade of a control element to be evaluated in real time. Another aspect of the disclosed and claimed concept is to provide such an improved detection apparatus and method wherein an neutron emission source is capable of being switched between an OFF state and an ON state and which therefore does not require shielding during transportation or during use and rather relies upon the water in a fuel inspection pool for any shielding that may be needed when the neutron emission source is in its ON state. Another aspect of the disclosed and claimed concept is to provide such an improved detection apparatus and method that allow for the rapid evaluation of the neutron absorption properties of a control element of a nuclear installation by providing a mask apparatus having a number of masks that can be used individually and in various combinations to enable a region of a blade at which neutrons have been detected as passing therethrough to be evaluated using progressively finer evaluation devices that permit a rapid evaluation of various portions of the blade with an appropriately high resolution without requiring evaluation of the entire blade at the same high resolution, thereby saving time. As such, an aspect of the disclosed and claimed concept is to provide an improved detection apparatus that is usable to detect a neutron absorption capability of a control element of a nuclear installation, the detection apparatus can be generally stated as including a processor apparatus which can be generally stated as including a processor and a storage, a robot apparatus in communication with the processor apparatus and that can be generally stated as including a number of manipulators, a neutron radiograph apparatus that can be generally stated as including an neutron emission source, a detector array, and a mask apparatus, the neutron radiograph apparatus being structured to receive the control element generally between the neutron emission source and the detector array, the neutron emission source being switchable between an ON state and an OFF state, the neutron emission source in the ON state being in an electrically energized condition structured to generate a neutron stream, the neutron emission source in the OFF state being in an electrically de-energized condition structured to output no meaningful neutron stream, the detector array being structured to detect an unabsorbed portion the neutron stream that passes without being absorbed through the control element, the detector array being further structured to generate an output signal that is representative of the unabsorbed portion the neutron stream; and the mask apparatus being movable by at least a first manipulator of the number of manipulators among a number of positions, a position of the number of positions being that in which the mask apparatus is disposed at least partially between the neutron emission source and the detector array, another position of the number of positions being that in which the mask apparatus is removed from between the neutron emission source and the detector array. Other aspects of the disclosed and claimed concept are provided by an improved method of operating the aforementioned detection apparatus to detect a neutron absorption capability of a control element of a nuclear installation wherein the nuclear installation has a pool of water available to accomplish control element inspection. The method can be generally stated as including receiving into the inspection pool of water with the neutron emission source in the OFF state, submerging the neutron emission source in the OFF state in the pool of water to a predetermined water depth, and switching the neutron emission source from the OFF state to the ON state when the control element inspection is to commence subject to the depth of the neutron emission source in the pool of water meeting or exceeding the predetermined water depth to provide adequate shielding to allow the neutron emission source to emit a neutron stream. The method potentially may further include receiving the detector array and the mask apparatus into the pool of water, receiving at least a portion of the control element generally between the neutron emission source and the detector array, and monitoring the detector array for the possible outputting therefrom of an output signal that would be representative of an unabsorbed portion the neutron stream passing without being absorbed through the at least portion of the control element. Similar numerals refer to similar parts throughout the specification. An improved detection apparatus 4 in accordance with the disclosed and claimed concept is depicted generally in FIGS. 1 and 3-4 and it is depicted schematically in FIG. 2. The detection apparatus 4 is advantageously usable to inspect a control element 6 of a nuclear installation 8 for its capability of absorbing neutrons. FIGS. 1 and 3-4 depict the control element 6 having been removed from what would be its usual position situated among a plurality of fuel assemblies of the nuclear installation 8 and having been received in a water pool 30 such as used fuel pool although any pool of water can be used to receive the control elements 6 for the inspection method that is set forth in greater detail below and that is performed using the detection apparatus 4. The detection apparatus 4 can be said to include a neutron radiograph apparatus 12, a robot apparatus 14, and a processor apparatus 16. Additionally, the detection apparatus 4 includes an input apparatus 18 that provides input signals to the processor apparatus 16 and an output apparatus 20 that receives output signals from the processor apparatus 16. Certain of the components, such as the processor apparatus 16, the input apparatus 18, and the output apparatus 20, or portions thereof, by way of example, may be situated on a control panel 21 that may be situated remotely from the robot apparatus 14 and which may be connected with the robot apparatus 14 via an umbilical 23. Other configurations of the various components will be apparent. The processor apparatus 16 can include a number of various components and can be generally in the nature of a general purpose computer that includes a processor such as a microprocessor or other processor and storage such as RAM, ROM, EPROM, EEPROM, FLASH, and the like and that function in the nature of internal storage on a computer. The processor apparatus 16 includes a number of routines 22 that are stored in the storage and that are executable on the processor to cause the processor apparatus 16 and thus the detection apparatus 4 to perform certain operations such as will be set forth in greater detail below. The input apparatus 18 can include any of a number detection devices or other input devices and can include the input terminals that are connected with the processor apparatus. The output apparatus 20 can include any of a wide variety of output devices and may include, for instance, visual displays, audio transducers, and data output devices, etc., without limitation. As can be understood from FIGS. 1 and 3, the control element 6 is of an elongated cruciform shape that can be generally described as including a central hub 24 and a plurality of wings 28A, 28B, 28C, and 28D, which may be collectively or individually referred to herein with the numeral 28, and each of which extends from the hub 24. Each of the wings 28 has formed therein a number of passages 39, a small number of which are represented in dashed lines on the wing 28B, that are filled with a boron containing material or other neutron-absorbing material that causes the control element 6 to absorb neutrons. It is noted that all of the wings 28 have the passages 39 formed therein, and the passages 39 are situated along substantially the entirety of the length of each wing 28. As will be set forth in greater detail below, the detection apparatus 4 is advantageously usable to assess whether any one or more of the passages 39 that are formed in each of the wings 28 have lost their boron or other neutron absorbing material to render the control element 6 at any one or more positions thereon transparent to neutrons and thus to not absorb neutrons or to have reduced neutron absorption as such positions. The neutron radiograph apparatus 12 can be said to include an neutron emission source 32, a detector array 36, and a mask apparatus 38. As a general matter, the neutron emission source 32 is switchable between an ON state and an OFF state. In the ON state, the neutron emission source 32 is in an electrically energized condition and is configured to output a neutron stream 50 such as is depicted generally in FIG. 4. In the OFF state, the neutron emission source 32 is in an electrically de-energized condition and outputs no meaningful stream of neutrons. The neutron emission source can be viewed as being shielded on all sides except the side that faces a wing 28 of the control element 6 and thus emits the neutron stream 50 generally only in one direction, namely that which faces toward the wing 28. The neutron emission source 32 can be said to include an accelerator 42, a number of first particles 44, and a number of second particles 48. The accelerator 42 is a particle accelerator which, when electrically energized, has a potential difference of multiple hundred kilovolts. The ability to switch the accelerator 42 between an energized ON state and a de-energized OFF state advantageously enables the neutron emission source 32 to be switched between the ON and OFF states. In the exemplary embodiment depicted herein, the first particles 44 are a number of deuterium particles. Also in the exemplary embodiment depicted herein, the second particles 48 can be either deuterium particles or tritium particles. When the accelerator 42 is in its electrically energized ON state, it accelerates the first particles 44 to cause them to impact the second particles 48 to cause nuclear fusion of the deuterium and/or tritium particles and thereby produce neutrons that form the neutron stream 50. In the situation wherein the second particles 48 are deuterium particles, the collision of one of the first particles 44 with one of the second particles 48 produces helium three (He3, which includes two protons plus a neutron in the nucleus) plus an additional neutron that is emitted as a part of the neutron stream 50. In the situation where the second particles 48 are tritium particles, the collision of one of the first particles 44 with one of the second particles 48 result in the generation of helium four (He4, which includes two protons and two neutrons in the nucleus) plus an additional neutron that is emitted as a part of the neutron stream 50. The detector array is a device that is configured to detect neutrons and, in particular, the neutron stream 50 and can be viewed as likewise being shielded on all sides except for the side that faces toward a wing 28. The detector array 36 can be any of a wide variety of devices that detect neutrons including but not limited to an ion chamber containing or coated with BF3, He3, enriched uranium (fission chamber) or other such isotopes that absorb neutrons and thereby promptly release a charged particle such as an alpha or beta particle, proton, deuteron, or fission fragments that can be subsequently collected and measured as a charge pulse or integrated into a current. The detector array 36 desirably will have a high neutron sensitivity and also have the ability to reject gamma radiation that is necessarily a component of a normal, irradiated control element. When the detector array 36 detects a neutron signal that exceeds a certain threshold, meaning a detection of portion of the neutrons from the neutron stream 50 that meets or exceeds a predetermined threshold, the detector array 36 outputs an alert signal that is received at the input apparatus 18 as an input to the processor apparatus 16. In response to the reception of such an alert signal originating from the detector array 36, the routines 22 may initiate further processing in the location where the detector array 36 is situated. Additionally or alternatively, the routines 22 may cause the processor apparatus 16 to generate some type of an output signal that is communicated to the output apparatus 22 and that generates an output that is detectable by a technician, for example. The mask apparatus 38 can be said to include a plurality of masks, at least some of which are represented by the four exemplary masks that are shown in FIGS. 1 and 3 and which are indicated at the numerals 52A, 52B, 52C, and 52D, and which may be collectively or individually referred to herein with the numeral 52. As will be explained below, the masks 52 can be said to additionally include another mask 85 that is depicted in FIG. 5C and may include other masks without limitation. The masks 52 are each of a plate-like configuration and are formed of a neutron absorbing material such as cadmium or other appropriate material. The masks 52A, 52B, 52C, and 52D each have an opening formed therein that is indicated, respectively, at the numerals 56A, 56B, 56C, and 56D, and which can be collectively or individually referred to herein with the numeral 56. In the depicted exemplary embodiment, the openings 56 are each in the form of an elongated slot wherein the material of the corresponding mask 52 has been removed, which thus permits neutrons to flow through the opening 56 if such a portion of the neutron stream 50 exist in the vicinity of the opening 56. The masks 52 with the openings 56 formed therein can each additionally or alternatively each be referred to as being a collimator. The robot apparatus 14 can be said to include a support 58 and a plurality of manipulators that are situated on the support 58 and that are indicated at the numerals 62A, 62B, 62C, 62D, 62E, and 62F, which may be collectively or individually referred to herein with the numeral 62. The manipulators 62 are each robotic manipulators having one end situated on the support 58 and another end opposite thereto carrying a component of the neutron radiograph apparatus 12. In the depicted exemplary embodiment, the manipulators 62A, 62B, 62C, and 62D carry at the free end thereof a corresponding mask 52A, 52B, 52C, and 52D, respectively. The manipulator 62E carries the neutron emission source 32, and the manipulator 62F carries the detector array 36. The manipulators 62 are each robotically operated and thus are operable independently of one another to move the masks 52 and the neutron emission source 32 and the detector array 36 independently of one another. It is expressly noted that the neutron radiograph apparatus 12 and the robot apparatus 14 are depicted herein as including only four masks 52 (plus the mask 85) and four corresponding manipulators 62 that carry the masks 52, but it is understood that any number of manipulators 62 and any number of masks 52 can be employed depending upon the needs of the particular application, as will be set forth in greater detail below. The openings 56A, 56B, 56C, and 56D in the depicted exemplary embodiment are each of an elongated approximately rectangular shape having a length 64A, 64B, 64C, and 64D, respectively and a width 68A, 68B, 68C, and 68D, respectively. As mentioned above, the masks 52 themselves absorb neutrons, but the openings 56 permit neutrons to flow therethrough. The robot apparatus 14 additionally includes some type of a robotic tractor mechanism that is situated on the support 58 and which engages the control element 6 on a wing 28 thereof or otherwise and moves the support 58 with respect to the control element 6 or vice versa. In this regard, it is understood that detection apparatus 4 or the support 58 or both may include additional structures or support elements that are situated at the base of the water pool 30 and which are configured to receive and to carry thereon the control element 6 when it is received in the water pool 30. Alternatively, the control element 6 can simply be received in the water pool 30 and can have the support 58 received thereon, with the tractor then being robotically operated to move the support 58 along the longitudinal extent of the control element 6. In use, the detection apparatus 4 with the neutron emission source 32 in its OFF state is received in the water pool 30 and is submerged therein until the neutron emission source 32 is situated at a predetermined depth 82 (FIG. 1) within the water pool 30. At the predetermined depth 82, the neutron emission source 32 can be switched to its ON state because the water in the water pool 30 provides sufficient shielding from the neutron stream 50 that no additional shielding is required to protect personnel from the neutron stream 50. Advantageously, therefore, the detection apparatus 4 relies upon the shielding that already exists in the water pool 30 to shield personnel from the neutron stream 50 when the neutron emission source is in its ON state. The ability to switch the neutron emission source between the ON and OFF states avoids the need for other shielding when the neutron emission source 32 is being transported from one location to another and prior to the neutron emission source 32 being submerged to the predetermined depth 82. That is, the neutron emission source 32 during transport and prior to being submerged to the predetermined depth 82 is imply in its OFF state and is not placed in its ON state until it is submerged to a depth in the water pool 30 at or below the predetermined depth 82. When the support 58 is situated on the control element 6 or vice versa, the manipulators 62E and 62F are operated to cause the neutron emission source 32 and the detector array 36 to be situated at opposite surfaces of the wing 28 that is to be inspected, which is the wing 28A in FIGS. 1, 3, and 4. Since the neutrons exiting the neutron emission source 32 are at too high of an energy state to be detected by the detector array 36, the neutron emission source 32 must be spaced away from the surface of the wing 28 by a sufficient distance to enable the neutrons to be thermalized and thus slowed sufficiently that the neutrons of the neutron stream 50 that pass through the wing 28 can be absorbed by the control element or, in the case of a defect, be detected by the detector array 36. At the initial stage of the detection operation, the manipulators 62 that have a mask 52 situated thereon are arranged such that the masks 52 are positioned away from the neutron emission source 32 and the detector array 36, such as is depicted generally in FIG. 1. The neutron emission source 32 is then switched to its ON state if it is not already in such a state, and the detector array 36 output signal is monitored to determine whether there is a defect at any given position on the wing 28. If no output is detected from the output 36, the tractor on the support 58 is operated to cause the support 58 and thus the manipulators 62 and the neutron radiograph apparatus 12 situated thereon to be advanced along the longitudinal extent of the control element 6. If no signal is detected from the detector array 36 at any point along the longitudinal extent of the wing 28 that is being inspected, the wing 28 is considered to be good, meaning that it has no regions thereon where neutrons from the neutron stream 50 pass unabsorbed through the wing 28, and rather the wing 28 has absorbed all portions of the neutron stream 50 without permitting any portions of the neutron stream 50 to be detected by the detector array 36. The process can then be repeated for the other wings 28 on the control element 6 until all of the wings 28 have been inspected. On the other hand, the detector array 36 may, at some location along the wing 28, generate an output signal that is received by the input apparatus 18 and is provided as an input to the processor apparatus 16 whereupon one of the routines 22 will view the signal originating from the detector array 36 as being indicative of the detection of a portion of the neutron stream 50 that has passed unabsorbed through the wing 28 at such location. An exemplary set of passages 69 are depicted in FIGS. 1 and 4 and demonstrate that the neutron emission source 32 and the detector array 36 are at any given time adjacent a plurality of the passages 69 that are formed in the wing 28 that is being evaluated. As such, an output signal from the detector array 36 that the detector array 36 has detected a portion of the neutron stream 50 passing through the wing 28 does not, of itself, indicate which of the one or more passages 69 that are situated adjacent the detector array 36 may be breached and may have lost its boron or other neutron absorbing substance. It is noted, however, that the mere detection of an output from the detector array 36 signaling the passage through the wing 28 of an unabsorbed portion of the neutron stream 50 does not automatically result in rejection of the wing 28 or the control element 6 as being defective and in need of replacement. Rather, if the result of the analysis presented herein is that a given control element 6 has no more than a predetermined number of failed positions (i.e., meaning positions thereon where neutrons are not being absorbed), and if the distribution of such positions is sufficiently scattered, the control element 6 can be declared to be effective and not in need of replacement. It is necessary, however, to determine the extent and location of any such positions on the control element 6 where neutrons are not being absorbed and are passing through the control element 6. As noted above, however, the detection of an output signal from the detector array 36 does not necessarily indicate which of the passages 69 is/are in a state of partial or total failure. As such, whenever the detector array 36 provides an output signal that is representative of a neutron signal being detected at a position on the wing 28 where neutrons are passing unabsorbed therethrough, the mask apparatus 38 is operated to more finely analyze the region of the wing 28 where the neutron emission source 32 and the detector array 36 are disposed in order to determine with greater specificity exactly what positions on the wing 28 are permitting neutrons to pass therethrough. Advantageously, therefore, the mask apparatus 38 is deployed, such as is depicted generally in FIG. 3 by operating one or more the manipulators 62 to position one or more of the masks 52 between the neutron emission source 32 and the detector array 36 to block from the detector array 36 all neutrons except those neutrons from the neutron stream 50 that are passing through the opening 56 that is formed in each of the masks 52 that have been deployed in such a masking fashion. While the masks 52 are individually deployable by the corresponding manipulators 62, it can be understood that any individual deployed mask 52 will block all of the neutrons of the neutron stream 50 except in the location where the opening 56 is situated, which may be a region having the length 64 and the width 68 of the corresponding opening 56 of the mask that is being situated between the neutron emission source 32 and the detector array 36. However, if a plurality of the masks 52 are deployed and positioned such that the openings 56 overlie one another, the portion of the neutron stream 50 that can be received by the detector array 36 is only that portion of the neutron stream 50 that passes through the wing 28 and that also passes through the region where the corresponding openings 56 are overlying one another. Such a cooperating plurality of masks 52 can be referred to herein as being a mask system 70, and the overlying portions of the openings 56 of the masks 52 of the mask system 70 can be said to form an orifice 72. If the openings 56 are oriented perpendicular to one another, the resulting orifice 72 is much smaller than the cross-sectional area of the detector array 36, meaning that relatively smaller portions of the wing 28 (i.e., smaller than the cross section dimensions of the detector array 36) can be separately inspected to determine whether each such position on the wing 28 is defective and is permitting neutrons from the neutron stream 50 to pass therethrough. As can be understood from FIG. 5A, the mask system 70 has the orifice 72, which can be understood to be much smaller than the detector array 36 that is overlying the wing 28. It is noted that FIGS. 5A, 5B, 5C, and 5D depict in phantom lines an exemplary outline of the detector array 36 as it would be situated overlying the wing 28, but with the detector array 36 having been removed in order to better visualize the overlying openings 56 in the masks 52. As can be understood from FIG. 5A, the orifice 72 can be said to have a first dimension 76 (which, in the exemplary embodiment depicted herein, is equal to the width 68A) and a second dimension 78 (which, in the depicted exemplary embodiment, is equal to the width 68B). With the masks 52A and 52B of that particular mask system 70 being situated as depicted in FIG. 5A, the detector array 36 is monitored to determine whether it generates an output signal that would be representative of neutrons from the neutron stream 50 passing through the orifice 72 which overlies a given position 84A on the wing 28. If a signal is detected from the detector array 36, this fact is recorded in the processor apparatus 16. That is, the processor apparatus 16 would record the fact that neutrons were detected at the position 84A on the wing 28. On the other hand, if neutrons were not detected when the mask system 70 was positioned as depicted in FIG. 5A, the processor apparatus 16 may (and likely would) record the fact that neutrons were not detected at the position 84A on the wing 28. The mask system 70 then can be manipulated to move the orifice 72 to a different position, such as the position 84B that is depicted in FIG. 5B. As can be understood from a comparison of FIGS. 5A and 5B, it can be understood that the orifice 72 was moved from the first position 84A of FIG. 5A to the second position 84B of FIG. 5B by employing the manipulator 62B to translate the mask 52 in the vertically downward direction from the perspective of FIGS. 5A and 5B when going from FIG. 5A to FIG. 5B. With the mask system 70 as arranged in FIG. 5B, the detector array 36 is monitored to determine whether it is generating an output signal that would be indicative of neutrons passing through the orifice 72 at the position 84B. Whether or not an output signal is detected from the detector array 36 when the orifice 72 overlies the position 84B is recorded in the processor apparatus 16. In this regard, it is understood that any number of intermediate positions between the position 84A of FIG. 5A and the position 84B of FIG. 5B can also be evaluated for the detection of neutrons by the detector array 36 and such detection (or non-detection) recorded in the processor apparatus 16, as appropriate. The mask apparatus 38 thus can be manipulated until all of the positions on the wing 28 that are adjacent the detector array 36 have been evaluated by overlying the orifice 72 over such positions and detecting whether or not the detector array 36 has generated an output signal that is indicative of neutron passage at such position on the wing 28. In so doing, it may be necessary to employ different masks, such as is depicted in FIG. 5C wherein the mask 52B is combined with the other mask 85 of the mask apparatus 38 to form another mask system 70A having an orifice 73 overlying another position 84C on the wing 28. For instance, the mask 52A may have been withdrawn and the mask 85 deployed in its place. The other mask 85 was not depicted in FIGS. 1 and 3 for reasons of simplicity of disclosure. The mask 85 is manipulated separately by its own manipulator of the robot apparatus 14 that is likewise not depicted in the accompanying drawings for reasons of simplicity of disclosure. In the depicted exemplary embodiment, the orifice 73 of FIG. 5C has the same first and second dimensions 76 and 78 as the orifice 72 of FIGS. 5A and 5B. It can be seen that the mask 85 has its own opening formed therein that is positioned thereon at approximately the middle thereof rather than being situated closer to the end thereof (as is the case with the mask 52A), and this enables an end 87 of the mask 85 to extend beyond the edge of the opening 56B. That is, the various masks (such as are indicated at the numerals 52, 85, etc. and which can include other masks that are not expressly depicted herein) are configured such that in various combinations they can completely block the passage of neutrons from the neutron stream 50 that may pass through the wing 28 other than the neutrons that additionally pass through the orifice 72 or 73, by way of example. It can be understood that the movement of one or more of the masks 52 with respect to other masks 52 and the like can be programmed into one of the routines 22 and executed by the processor apparatus 16 and the robot apparatus 14 that is connected therewith. Likewise, the selection of the various masks 52 and 85 and other such masks that may not be expressly depicted herein and their use in combination with other such masks 52 can likewise be programmed into one of the routines 22. It thus can be understood from the foregoing that the detector array 36 situated at the location depicted generally in FIG. 5A had generated an output signal, indicating that neutrons were passing from the neutron stream 50 through the wing 28 at one or more positions on the wing 28 directly adjacent the detector array 36 and were being detected by the detector array 36. As such, the masks 52A and 52B were deployed and were positioned as is depicted in FIG. 5A. The mask system 70 was manipulated such that the orifice 72 thereof was successively positioned, in a raster-like fashion, across all of the positions (84A, 84B, 84C, etc.) between the detector array 36 and the wing 28 to determine at which of such positions the detector array 36 again produced an output that is indicative of neutrons. In other words, the detector array 36 positioned as situated in FIGS. 5A-5C detected neutrons at some position on the wing 28 adjacent the detector array 36, and the various masks 52 were thus deployed between the detector array 36 and the wing 28 and were positioned to move the orifice 72 among all of the positions (such as the positions 84A, 84B, and 84C) to determine with greater specificity the particular position(s) on the wing 28 adjacent the detector array 36 where neutrons were actually passing through the wing 28. By way of example, it may have been determined that a positive signal was received from the detector array 36 only at the position 84C in FIG. 5C. This would indicate that when the detector array 36 was situated in the location on the control element 6 that is depicted in FIGS. 5A-5C, and when the detector array 36 initially generated its output signal representative of detecting neutrons somewhere along its cross-sectional area, it really was detecting neutrons somewhere within the position 84C. This would indicate that the wing 28 has a failed region within position 84C. Depending upon the sizes of the transverse dimensions of the orifice 73, the determination, as in FIG. 5C, that the position 84C was the source of neutrons may be sufficiently precise information that no further analysis is needed. On the other hand, it may be decided that merely identifying position 84C to the processor apparatus 16 is insufficiently accurate to evaluate the overall ability of the control element 6 to absorb neutrons, whether simply at the location or overall, and that more specific and fine detail may be warranted, as is depicted generally in FIGS. 5D and 6. For instance, it may be decided to remove the masks 52B and 58 from being situated adjacent the detector array 36 and to instead deploy the masks 52C and 52D to form another mask system 70B whose openings 56C and 56D are relatively narrower than those of the mask system 70A. That is, the widths 68C and 68D are relatively narrower than the widths 68B and the width of the opening in the mask 58. As such, the openings 56C and 56D overlaid as in FIG. 5D may form a relatively smaller orifice 83 having relatively smaller first and second dimensions 76A and 78A (FIG. 6), i.e., relatively smaller than the first and second dimensions 76 and 78 of the orifices 72 and 73. The mask system 70B can be manipulated such that the orifice 83 is successively positioned along a plurality of further positions 88 that are depicted in FIG. 6 and are themselves each discrete areas within the position 84C that was identified in FIG. 5C as having neutrons passing therethrough from the neutron stream 50. As such, the masks 52C and 52D can be manipulated by the manipulators 62C and 62D such that the resultant orifice 83 moves in a raster-like fashion across the position 84C among the various further positions 88 until a number of the further positions 88 are detected to have a neutron signal passing therethrough. Whether or not the detector array 36 output its alarm signal coincident with any of the further positions 88 is recorded in the processor apparatus 16. The exemplary further positions 88 where neutrons were detected are indicated schematically in FIG. 6 with cross-hatching and are represented at the numerals 90A, 90B, 90C, 90D, and 90E, which may be collectively or individually referred to herein with the numeral 90. If the detection of a neutron signal at the further positions 90 is information that is sufficiently detailed and precise, the evaluation of the position 84C can end and the detector array 36 can be moved to another location along the length of the control element 60. Alternatively, if more detailed analysis of the further positions 90 is desired, further masks 52 having even smaller openings formed therein can be deployed to evaluate in a raster-like fashion a number of smaller areas within each of the further positions 90, and the resulting output signals from the detector array 36 coincident with such smaller areas recorded in the processor apparatus 16, until sufficiently detailed information regarding exactly where on the wing 28 the neutron stream 50 is passing through is obtained. It is reiterated that all such outputs from the detector array 36 are received in real time at the processor apparatus 16. It is understood that the initial use of the detector array 36 without the mask apparatus 38 until the detector array 36 provides an output, and then the responsive use of masks 52 having progressively smaller openings 56 at the positions (84A, 84B, and 84C, for example) and further positions 84 and 90 (further by way of example) where neutron signals were detected saves inspection time and results in a rapid inspection procedure. While the entire wing 28 can be evaluated at the finest possible orifice size, such evaluation of the entire wing with such fineness would take an excessively long period of time and likely would be unnecessary. However, by performing a relatively coarse analysis by using the masks 52A and 52B with relatively larger openings 56A and 56B to identify, on a coarse basis, the various positions 84 where a neutron signal is detected, and by then performing a relatively finer evaluation using the masks 52C and 52D having the relatively smaller openings 56C and 56D, the relatively finer evaluation is done only at the positions 84 where it is known that a neutron signal exists. As such, the various positions where no signal is detected can be rapidly evaluated and ignored using the relatively coarse analysis afforded by the masks 52A and 52B, and the relatively finer analysis can be deployed only where neutron signals are known to have been detected. The use of such progressively finer evaluation at the positions where neutron signals are detected provides for a greater efficiency and minimized time waste. It is understood that the various masks 52 that are used may be dependent upon the configuration of the passages 69 in the control element 6. As mentioned above, the passages 69 that are depicted in an exemplary fashion in FIG. 1 in the wing 28B (and which are representative of the passages 69 that are situated along substantially the entirety of the lengths of all of the wings 28) represent one known way of configuring the passages 69 with the boron or other neutron absorbing substance contained therein, i.e., perpendicular to the longitudinal extent of the hub 24. As noted above, an alternative design exists wherein the passages that contain the boron or other neutron absorbing materials are oriented parallel with the longitudinal extent of the hub 24. It thus may be desirable to provide masks of different configurations having openings with different sizes and/or shapes and/or orientations that are optimized to evaluate such an alternative arrangement of passages. An alternative mask system 170 is depicted in FIGS. 7A-7C. The alternative mask system 170 is configured such that its opening 156 can selectively have a plurality of different dimensions. This is accomplished by configuring the mask system 170 to include a plate-like first member 154 having a notch 160 formed therein and by further providing a plate-like second member 166 which is movable with respect to the first member 154. In this regard, a separate robotic tractor may be provided on the mask system 170 to move the second member 166 with respect to the first member 154 or vice versa. As can be understood from FIGS. 7A-7C, the opening 156 is of a fixed length 164, but the width is variable between, for instance, a relatively wider width 168A (such as is depicted in FIG. 7A), a relatively smaller width 168B (such as is depicted in FIG. 7B), and a further smaller width 168C (as is depicted in FIG. 7C). The various widths 168A, 168B, and 168C are exemplary and can be larger, smaller, etc. without departing from the spirit of the present disclosure. By way of example, the mask system 170 potentially could take the place of the mask 52A being removed and replaced with the mask 52C having the relatively narrower opening 56C. Likewise, another instance of the mask system 170 could take the place of both the masks 52B and 52D and would avoid having to remove the mask 52B to be replaced with the mask 52D. Rather, the mask system 170 could be retained in place adjacent the detector array 36 and simply manipulated to make its opening 156 relatively narrower, such as by progressively changing it such that its width goes from that depicted in FIG. 7A and is indicated at the numeral 168A until the width is reduced to that indicted at the numeral 168C in FIG. 7C. The mask system 170 could be used with additional instances of the mask system 170 or with other masks 52 without limitation. It can be understood that the mask system 170 could take other forms that permit not only the width of the opening 156 to be changed, but also the length 164 can be changed as well as the position of the opening 156 thereon can likewise be changed. Any of a number of configurations of additional mask systems that provide various opening positions or dimensions and both can be envisioned. An improved method in accordance with the disclosed and claimed concept is depicted generally in FIGS. 8A and 8B. Processing can be said to begin, as at 204, where the neutron radiograph apparatus 12 in its OFF state is received in the inspection water pool 30 of the nuclear installation 8 and is submerged until the neutron emission source 32 is at or below the predetermined depth 82. The control element 6 can then be positioned, as at 208, in the water pool 30 such that a wing 28 or other portion of the control element 6 is situated generally between the neutron emission source 32 and the detector array 36. The neutron emission source 32 can then be switched from its OFF state to its ON state, as at 212, by energizing the accelerator 42 to cause it to emit the neutron stream 50. The support 52 can then be incrementally moved with respect to the control element 6 or vice versa while the detector array 36 is monitored for the possible outputting of a signal from the detector array 36 that would be representative of an unabsorbed portion of the neutron stream 50 passing unabsorbed through a portion of the control element 6. Such an output, if detected, could be received by the input apparatus 18 and provided as an input signal to the processor apparatus 16. If, as at 220, no signal above a threshold value is detected from the detector array 36, processing can continue, as at 216, where the neutron radiograph 12 is incrementally moved farther along the control element 6. On the other hand, if at 220 a signal is received from the detector array 36, an output can be generated, as at 224. The output, as noted above, can be received by the input apparatus 18 and can result in the outputting of an alarm signal or the triggering of a routine 22 to manipulate the mask system 38, or both. For example, and as at 228, a portion of the mask apparatus 38 can be moved from a location that is disposed generally away from the neutron emission source 32 and the detector array 36 to another location situated generally between the neutron emission source 32 and the detector array 36. Processing can then continue, as at 232, where the control element 6 is evaluated using the mask system 38 by using an orifice 72 that is of an initial size and that is moved in a raster-like fashion about that region of the control element 6 while monitoring the detector array 36 for additional signals that would be representative of an unabsorbed portion of the neutron stream 50 passing unabsorbed through the control element 6 and through the orifice 72. As at 236, the processor apparatus 16 can record the one or more positions on the control element 6 at which the additional signals were received from the detector array 36. If it is determined, as at 240, that greater fineness in the evaluation is not needed, the analysis can be terminated, as at 244, and the results of the analysis can be output for expert evaluation. However, if it is determined at 240 that further fineness in the evaluation is desired, processing can continue, as at 248, where a further evaluation of the positions at which the signals were detected with the detector array 36 can be carried out by using the mask system and an orifice 83 of a relatively smaller size. Again, such analysis would be performed in a raster-like fashion as set forth above, or can be carried out in other fashions without departing from the spirit of the present disclosure. Recordation can occur, as at 252, as to any one of more finely defined positions on the control element 6 at which further signals have been received from the detector array 36. It is understood that the procedure noted above can be performed in any of a variety of different orders depending upon the need for efficiency. For example, it is possible that the wing 28 may be evaluated in its entirety using the neutron emission source 32 and the detector array 36 without deployment of the mask apparatus 38 in order to find the various locations thereon where neutron signals are detected. Afterward, another pass can be made using the masks 52A and 52B having the relatively larger openings 56A and 56B, and such mask system 70 can be moved in a raster-like fashion across the various locations that were detected and stored during the first pass when the mask apparatus 38 was not employed. The various positions where signals are detected with the masks 62A and 62B in place would be recorded. This could occur across the entirety of the length of the wing that is being evaluated. Then, perhaps, a further pass can be performed across the entirety of the length of the control element using the relatively finer masks 52C and 52D, and only those positions where signals have been detected and stored would be the subject of further analysis by the mask system 70A. Other variations will be apparent. It thus can be understood that the detection apparatus and the method described herein permit rapid evaluation of the control element 6 and permits a determination to be made whether the control element is in need of replacement or whether the control element 6 can be redeployed in the nuclear installation 8. It is possible that variations of the detection apparatus 4 can be provided wherein multiple wings 28 are simultaneously evaluated using multiple neutron emission sources and detector arrays. The neutron emission source 32 advantageously can be switched between an OFF condition and an ON condition, thereby avoiding the need for shielding when the emissions source 32 is being transported from one location to another. As mentioned above, known californium neutron emission sources cannot be switched off, and thus the neutron emission source 32 advantageously avoids the need for the separate, heavily shielded shipping cask required to transport a californium source without the presence of a 5 meter deep large pool of water. Additionally, the evaluation using the detector array 36 and the mask system 38 provides real time analysis of the wing 28, which enables greater efficiency in directing the evaluation, and it also avoids the need for prolonged exposure of film, to a neutron source. Additionally, the configuration of the mask apparatus 38 to provide progressively smaller orifices to provide finer evaluation only in those positions where such finer evaluation is needed saves evaluation time and results in a rapid overall evaluation of the control element 6. Further advantages will be apparent. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
046559973	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is illustrated in diagrammatic and fragmentary manner an embodiment of thermal insulation, designated generally 1 and typically consisting of a pack of elements 2, mounted on the roof of a vault or concrete pressure vessel, the reference numeral 3 indicating either the concrete itself or a metallic membrane lining the concrete, as appropriate to the design of nuclear reactor involved. The mounting is effected by a plurality of hangers, one being shown in the drawings, designated 4. Each hanger 4 is elongate, is of metal, preferably of circular cross-section, and has a hooked end 5 engageable with an eye 6 which can be part of an eyebolt embedded in the concrete or is welded to the said membrane. In alternatives, not shown, the hooked end 5 can be formed as an eye and engaged with the eye 6, or the eye 6 can instead be a hook and be engaged either with the hooked upper end 5 of a hanger 4 or with an eye constituting the said upper end. All four alternatives give freedom for each hanger 4 to move in two dimensions in a pivotal manner. The thermal insulation 1 has a number of apertures 7 one for each hanger 4, consisting of a part 8 of larger diameter to provide clearance for the hook/eye or alternatives, and a part 9 of smaller diameter to accommodate the intermediate part of the respective hanger 4. A lining 10 for the parts 8 and 9 is included. The aperture 7 also extends through a casing 11 which forms the lower extremity of the thermal insulation 1. The latter is advantageously provided in separate, adjoining units (not shown) with overlapping or interleaving to avoid radiation shine and hot spots. The lower end of each hanger 4 carries a composite assembly 12 composed of three elements 13, 14, 15 respectively. The purpose of the composite assembly 12 is to retain the thermal insulation on the roof in a manner which avoids undue straining when ambient temperature varies, as will happen during different operational states of the nuclear reactor, including shut-down, normal operation for power generation (when the ambient temperature may vary over a relatively small range depending on reactor power or loading) and fault conditions. The element 13 is hollow cylindrical with a ridge 16 in one dimension and with opposed holes 17 across the ridge 16 and corresponding with holes 18 in the casing 11, there being a dowel pin 19 engaging each pair of holes 17, 18 and extending between element 13 and casing 11. Beneath element 13 is disposed the element 14 which is another hollow cylindrical element having a one dimensional ridge 20, opposed holes 21 across the ridge 20 and aligned with holes 22 in the lower part of element 13, and dowel pins 23 engaging the holes 21, 22 and extending between elements 13 and 14. The ridge 16 is 90.degree. offset from ridge 20, and each hole pair 17, 18 is disposed 90.degree. offset from each hole pair 21, 22 as can be appreciated from the drawings. The third element of each composite assembly 12 is a nut 15 engaging a screwthread 24 at the lower end of the respective hanger 4 and serving to hold the composite assembly in operative position both axially and angularly such that the ridge 16 engages that part of casing 11 which surrounds the respective aperture 7, the ridge 20 engages the lower surface of element 13, and consequently the dowel pins 19, 23 are retained in their respective hole pairs. The nut 15 can be welded in its operative position as shown. Each composite assembly 12 enables the insulation 1 to move laterally whilst avoiding any tilting thereof, as dictated by thermal expansion or contraction. The ability of the insulation to move laterally without tilting avoids straining of the insulation, this contributing significantly to its ability to fulfil its design life in trouble-free manner.
046817271	claims	1. A one-step chemical manipulation in combination with a distillation and collection process for producing At-211 comprising; a. providing a target of irradiated Bismuth coated to a predetermined thickness of a backing member, b. providing a vapor-producing still operably connected with a condenser that has a water cooled condensate collector formed of a dry silica gel mesh therein maintained at a temperature above the freezing point of water, and providing an effluent gas filter that is operably connected to receive effluent gas from the condenser, c. heating the target in said still at a temperature in the range of about 630.degree.-680.degree. C. for a time period in the range of 50 to 80 minutes, to evole At-211 vapor from said target, d. providing a dry carrier gas having an oxygen concentration that is sufficient to form Bi.sub.2 O.sub.3 thereby to essentially preclude vaporization of Bi metal, passing said carrier gas through said still to carry the At-211 vapor to said condenser, and to carry effluent from the condenser to the effluent gas filter, e. eluting At-211 from the condensate collector of said condenser with a controlled volume of eluent containing predetermined solvents that are compatible with a given desired radiopharmaceutical procedure, and f. collecting said At-211 in said controlled volume of eluent for use in said given radiopharmaceutical procedure. a. providing a gas dryer apparatus comprising a trap cooled by a mixture of dry ice and isopropyl alcohol, b. providing a carrier gas mixture of about 50% O.sub.2 and 50% N.sub.2, and c. passing said carrier gas mixture through said gas dryer apparatus, to dry the gas mixture, before passing the gas mixture through said still. a. providing an aluminum backing member, forming a depression in a surface of said member, heating the member to above the melting temperature of Bi, b. placing particles of high purity Bi in the depression in said heated Al member to melt the Bi, and scratching the surface of the depression to help the Bi wet and uniformly coat that surface, cooling the backing member, c. and machining the Bi coating to a smooth outer surface, thereby to form the Bi coating in a layer of generally uniform thickness having about 100 mg of Bi per cm.sup.2 of coated backing member area, and d. irradiating the target for a time period in the range of 1 to 3 hours with a beam of 26.5.+-.0.5 MeV accelerating voltage accelerated alpha particles having a current in the range of 6 to 10 microamperes. 2. A process as defined in claim 1 including: 3. A process as defined in claim 1 wherein said controlled volume of eluent is effective to elute about 90% of the At-211 from the condensate collector responsive to being passed through the collector only once. 4. A process as defined in claim 3 wherein said controlled volume of eluent includes a first portion and a second portion, said first and second portions being about equal in volume, and said second portion being effective to elute about 8% of the original amount of At-211 collected in the condenser, after said first portion has effectively eluted about 90% of said original amount of At-211 from the condenser. 5. A process as defined in claim 1 including making said target of Bi coated on an aluminum backing member, by the steps comprising;
	claims	1. A method of moderating a fuel bundle of a boiling water reactor, comprising:inserting at least one moderating fuel rod into the fuel bundle, the at least one moderating fuel rod including a nuclear fuel section, a neutron moderator section including a metal hydride, and a threaded connector joining the nuclear fuel section and the neutron moderator section;wherein an average diameter of the neutron moderator section is different when a position of the at least one moderating fuel rod is in an interior of the fuel bundle as compared to an average diameter of the neutron moderating section of a moderating fuel rod at a more exterior location in the fuel bundle. 2. The method of claim 1, further comprising:configuring the neutron moderator section to include an inner tube within an outer tube, the metal hydride being contained within the inner tube. 3. The method of claim 1, further comprising:laterally supporting the at least one moderating fuel rod with a spacer grid, the at least one moderating fuel rod being positioned such that the threaded connector is within the spacer grid. 4. The method of claim 1, further comprising:varying an axial length of the neutron moderator section based on the position of the at least one moderating fuel rod in the fuel bundle. 5. The method of claim 4, wherein the axial length of the neutron moderator section is longer when the position of the at least one moderating fuel rod is in an interior of the fuel bundle relative to axial lengths of neutron moderator sections of other moderating fuel rods that are at more exterior locations in the fuel bundle. 6. The method of claim 4, wherein the axial length of the neutron moderator section is shorter when the position of the at least one moderating fuel rod is in an exterior of the fuel bundle relative to axial lengths of neutron moderator sections of other moderating fuel rods that are at more interior locations in the fuel bundle. 7. The method of claim 4, wherein the average diameter of the neutron moderator section is larger when the position of the at least one moderating fuel rod is in an interior of the fuel bundle relative to average diameters of neutron moderator sections of other moderating fuel rods that are at more exterior locations in the fuel bundle. 8. The method of claim 4, wherein the average diameter of the neutron moderator section is smaller when the position of the at least one moderating fuel rod is in an exterior of the fuel bundle relative to average diameters of neutron moderator sections of other moderating fuel rods that are at more interior locations in the fuel bundle.
041586050	summary	CROSS-REFERENCE TO RELATED APPLICATIONS Reference is made to the following applications, assigned to the Westinghouse Electric Corporation and filed concurrently herewith: 1. Application filed in the name of R. T. Berringer and O. J. Machado entitled "Nuclear Core Region Fastener Arrangement", Ser. No. 635,024, herein referred to as the first Berringer/Machado application. The first Berringer/Machado application may be referred to for a more complete understanding of the thermally induced stresses imposed upon core region baffling components and fasteners. This invention may be utilized in conjunction with the invention of the first Berringer/Machado application. 2. Application filed in the name of R. T. Berringer and O. J. Machado entitled "Baffle-Former Arrangement For Nuclear Reactor Vessel Internals", Ser. No. 635,025, herein referred to as the second Berringer/Machado application. The second Berringer/Machado application may be referred to for a better understanding of the functions and operating limitations of a baffling arrangement for a nuclear reactor. This invention may be utilized in conjunction with the inventive teachings of the second Berringer/Machado application. 3. Application filed in the name of R. T. Berringer entitled "Nuclear Reactor Core Flow Baffling", Ser. No. 635,026, herein referred to as the Berringer application. The Berringer application may be referred to for a better understanding of flow patterns through and about a nuclear reactor core. This invention provides an alternative baffling arrangement to the inventive arrangement of the Berringer application. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to nuclear reactors, and more particularly to reactor internals apparatus for baffling reactor coolant flow into and about the reactor core. 2. Description of the Prior Art A typical nuclear reactor core includes a plurality of fuel assemblies positioned adjacent one another so as to approach the configuration of a right circular cylinder. The core typically seats upon and is supported by a lower core plate which in turn is supported by a flow control and support structure, such as a core barrel surrounding the core radial periphery. As the core barrel must support this large load, it is a relatively thick-walled massive structure. The core barrel, however, must be spaced from the peripheral core assemblies to alleviate the effects of irradiation upon the barrel wall. Also, cool reactor coolant entering the vessel passes about the outer surface of the core while the coolant passing through the core is hotter. Therefore, spacing the barrel from the core also protects the barrel wall from an excessive thermal gradient. It is, however, undesirable to allow a large flow of coolant to bypass the core in the area between the barrel and core, as the bypass flow detracts from the reactor thermal efficiency. A baffle plates and formers assembly has therefore been utilized to baffle flow into and immediately about the core, while also providing an acceptable bypass coolant flow. This assembly has included a plurality of longitudinally positioned baffle plates each extending throughout the core height, and abutting against one another about the core periphery. The baffle plates are affixed to and supported by transversely positioned formers, which are supported by the core barrel. The barrel, baffle plates, and formers are affixed by fasteners, such as welds or, more typically, bolts. Because the barrel is relatively thick walled, and the baffle is relatively thin walled, they experience a thermal expansion differential that must be accommodated by the fastening means affixing the barrel, baffle plates, and formers, such as the bolts. With increased reactor core lengths, the differential expansion and resulting loads are increased even more. The resulting loads on the fasteners are significant, and can potentially result in failure. Also, the differential expansion can cause bending of the baffle plates, resulting in potential interference with the fuel assemblies and undesirable changes in the coolant flow. Particularly, enlarged gaps may occur between adjacent baffle plates, allowing cross flows which detrimentally vibrate the fuel assemblies. It is therefore desirable to provide a baffle arrangement which not only baffles coolant flow into and about the core and provides cooling of the baffle and support components, but which also alleviates the large stresses and loads imposed upon the components and the fasteners affixing these components. SUMMARY OF THE INVENTION This invention provides core baffling apparatus which overcomes the above discussed deficiencies of the prior art. It includes utilization of the structure surrounding the core radial periphery, such as a core barrel. It further includes a plurality of longitudinally aligned baffle plates spaced closely adjacent the core periphery within the surrounding structure which are positioned to present a substantial barrier to flow of reactor coolant through the plates and minimal resistance to longitudinal thermal expansion. The baffle plates are affixed to the surrounding structure through means such as formers and fasteners such as bolts which, due to the plurality of aligned baffle plates, are stressed less than prior art arrangements. In the regions where the baffle plates are longitudinally aligned they can be provided with mating extensions and longitudinal clearances that allow longitudinal growth without significant interference. The plates can also be oriented with a small transverse clearance or a sliding interference fit to minimize leakage at the mating region. Further, the mating region may be aligned with the means of attachment, such as the formers, to present an even greater barrier to leakage across the plates.
	description	This application is a continuation of prior International Patent Application No. PCT/JP2010/052681, filed Feb. 23, 2010, the entire contents of which are incorporated herein by reference. 1. Field of Invention The present invention relates to a stage device, and particularly to a stage device using an air bearing in a vacuum in an electron beam exposure apparatus or the like. 2. Background Art In electron beam exposure apparatuses and electron microscopes, a sample is exposed, observed, or measured while being mounted on a stage. For example, an electron beam exposure apparatus performs an exposure process while moving a stage in accordance with exposure data so that a required position on a wafer may be exposed. A roller stage of cross roller type has been provided as a stage including a mechanical bearing. Regarding this stage, multiple rollers provided in a track between a movable stage and a fixed stage are rolled (rotated) to move the stage. When such a stage with a mechanical bearing is used in a state where a particle exists on a track, the particle causes strain in the stage mechanism. Such strain degrades the accuracy of stage position detection, and makes it difficult to detect a stage position accurately. Moreover, a particle does not remain at a certain place on the track but moves as the stage moves. This phenomenon hinders replication of the position change of the stage and prediction of a position where to move the stage. Thus, the stage mechanism has difficulty in correcting the position of the stage. Further, in the case where oil is applied to the track and the rollers for lubrication of the track and the prevention of dust generation, particles can be removed to a certain extent while the oil exists, but dust may be generated rapidly when the oil is lost. In contrast to the stages using mechanical bearings, techniques using air bearings are coming to be studied and used. For example, Japanese Patent Application Publication No. 2006-66589 describes a stage device in an exposure apparatus for use in photolithography. In the stage device, a movable member is supported on a base member in a noncontact manner using a fluid bearing (gas bearing). When such an air bearing is used, the degradation of accuracy of a stage caused by particles on the track of the stage can be reduced compared to when a mechanical bearing is used. On the other hand, when an air bearing stage is used, air needs to be supplied for driving a stage mechanism. Usually, the air generated by an air generator is supplied to the stage via air piping made of a PTFE-based material which is usable in a vacuum chamber. In this case, the air piping in this vacuum chamber moves every time the stage moves, and accordingly is partly bent. Since a moving range of the stage is limited, the air piping is frequently bent nearly at the same portion, and therefore may be ruptured due to fatigue after numerous bending actions. For this reason, the operating life of the entire stage device is determined by a defect of the air piping even if the stage itself has no failure. For example, continuous use of a typical stage device available at present requires replacement of the piping every several years. The present invention has been made in view of the problems of the conventional technology, and has an objective to provide a stage device which has no risk that air piping may rupture due to bending actions along with movement of the stage. In order to solve the above problems of the conventional technology, according to a preferred aspect of the present invention, a stage device to be used in a vacuum environment, comprising: a gas supply unit configured to generate a gas; a base member having four of upper, lower, right, and left surfaces; a slider formed in a frame shape surrounding the base member and having surfaces facing the respective four surfaces of the base member, and disposed to be movable; and an air bearing configured to float the slider by supplying the gas to a space between the base member and the slider. The slider includes an air chamber provided on the surfaces facing the base member and configured to accumulate air; and the base member includes thereinside a slider-moving air flow passage configured to supply the gas from an inlet port for guiding the gas generated by the gas supply unit to an outlet port for supplying the gas to the air chamber of the slider. In the stage device according to this aspect, the base member includes a pressure receiving plate configured to divide the air chamber of the slider into a first air chamber and a second air chamber, and the slider-moving air flow passage includes a first air flow passage and a second air flow passage, and is configured to supply the air from the outlet port of the first slider-moving air flow passage to the first air chamber and to supply the air from the outlet port of the second slider-moving air flow passage to the second air chamber. Additionally, the slider includes the air chambers located on both the upper and lower surfaces or both the right and left surfaces of the slider being opposed to each other and facing the base member, and the outlet ports of the slider-moving air flow passages formed inside the base member respectively supply the air to the air chambers on both the surfaces. Moreover, in the stage device according to this aspect, the slider includes an air pad configured to emit the air for floating the slider above the base member, and an air supply groove configured to supply the air to the air pad, and the base member includes an air flow passage for air pad configured to connect a supply port for supplying the air generated by the gas supply unit to an air outlet port for infusing the air into the air supply groove. Additionally, the infused air is supplied to the air pad of the slider through (piping) buried inside the slider. Furthermore, the stage device according to this aspect further comprises a first slider and a second slider configured to move simultaneously in a direction perpendicular to a moving direction of the slider. One end of the base member is connected to the first slider and another end of the base member is connected to the second slider, the air supplied to any of the slider-moving air flow passage and the air flow passage for air pad inside the base member is supplied through the first slider and the second slider. Additionally, the first slider is formed into a frame shape around a first fixed member and the second slider is formed into a frame shape around a second fixed member, a flow passage inside the first slider is connected to a flow passage formed inside the first fixed member through a first air supply groove formed on a surface of the first slider facing the first fixed member, and a flow passage inside the second slider is connected to a flow passage formed inside the second fixed member through a second air supply groove formed on a surface of the second slider facing the second fixed member. In addition, the stage device further comprises a first end plate located between the base member and the first slider; and a second end plate located between the base member and the second slider. The air flow passage formed inside the base member includes a first flow passage and a second flow passage, the air is supplied to the first flow passage in the base member through the flow passage formed inside first fixed member, a passage hole formed inside the first slider, and a passage hole formed in the first end plate, and the air is supplied to the second flow passage in the base member through the flow passage formed inside second fixed member, a passage hole formed inside the second slider, and a passage hole formed in the second end plate. According to the stage device of the present invention, the air flow passage is provided inside the base member. Moreover, the stage device supplies the air necessary for moving the slider to the air chamber and necessary for floating the slider to the air supply groove of the slider through this flow passage. In this way, it is not necessary to use the piping for air supply inside the vacuum chamber, which makes it possible to eliminate a risk of rupture of the piping and to avoid dependency of the operating life of the stage on the operating life of the piping. Now, embodiments of the present invention will be described below with reference to the accompanying drawings. First, a configuration of an electron beam exposure apparatus and a stage device will be described with reference to FIG. 1 to FIG. 5B. Then, an air supply mechanism not requiring air supply pipes inside a vacuum chamber will be described with reference to FIG. 6 to FIG. 8. Note that although the following description is intended for the case of using a stage device in an electron beam exposure apparatus, the present invention is not limited thereto. It is of course possible to use the stage device as a stage in a different vacuum apparatus such as an electron microscope. (Configurations of Electron Beam Exposure Apparatus and Stage Device) FIG. 1 is a schematic configuration diagram of an electron beam exposure apparatus provided with a stage device according to this embodiment. The electron beam exposure apparatus is roughly divided into an exposure unit 100 and a digital control unit 200 configured to control the exposure unit 100. The exposure unit 100 includes an electron beam generating section 130, a mask deflecting section 140, and a substrate deflecting section 150. In the electron beam generating section 130, an electron beam EB generated from an electron gun 101 is subjected to a convergence action of a first electromagnetic lens 102. Then, the electron beam EB passes through a rectangular aperture 103a (a first opening) on a beam shaping mask 103, whereby a cross section thereof is shaped into a rectangle. The electron beam EB shaped into the rectangle forms an image on a second mask 106 for beam shaping by way of a second electromagnetic lens 105a and a third electromagnetic lens 105b. Thereafter, the electron beam EB is deflected by a first electrostatic deflector 104a and a second electrostatic deflector 104b provided for variable rectangular shaping and passes through a rectangular aperture 106a (a second opening) of the second mask 106 for beam shaping. The electron beam EB is thus shaped by the first and second openings. Thereafter, the electron beam EB forms an image on a stencil mask 111 by a fourth electromagnetic lens 107a and a fifth electromagnetic lens 107b in the mask deflecting section 140. Then, the electron beam EB is deflected by a third electrostatic deflector 108a (also referred to as a first selective deflector) and a fourth electrostatic deflectors 108b (also referred to as a second selective deflector) in line with a specific pattern P formed on the stencil mask 111, whereby a cross-sectional shape of the electron beam EB is formed into the shape of the pattern P. The pattern is also referred to as a character projection (CP) pattern. The electron beam EB is bent so as to be incident on the stencil mask 111 parallel to an optical axis by a deflector 108b disposed in the vicinity of the fifth electromagnetic lens 107b. While the stencil mask 111 is fixed to a mask stage, the mask stage is movable in a horizontal plane. When using the pattern P located outside a deflection range (a beam deflection region) of the third electrostatic deflector 108a and the fourth electrostatic deflector 108b, the pattern P is shifted to the beam deflection region by moving the mask stage. A sixth electromagnetic lens 113 disposed under the stencil mask 111 has a role to collimate the electron beam EB in the vicinity of a shield plate 115 by adjusting an amount of a current flowing thereon. The electron beam EB passing through the stencil mask 111 is bent back to the optical axis by deflecting actions of a fifth electrostatic deflector 112a (also referred to as a first bend-back deflector) and a sixth electrostatic deflector 112b (also referred to as a second bend-back deflector). The electron beam EB is bent by the deflector 112b disposed in the vicinity of the sixth electromagnetic lens 113 so as to be aligned with the axis and to travel along the axis thereafter. The mask deflecting section 140 includes first and second correction coils 109 and 110 configured to correct beam deflection aberrations caused by the first to sixth electrostatic deflectors 104a, 104b, 108a, 108b, 112a, and 112b. Thereafter, the electron beam EB passes through an aperture 115a (a round aperture) of the shield plate 115 constituting the substrate deflecting section 150, and is projected onto a substrate 12 by an electromagnetic projection lens 121. In this way, an image of the pattern on the stencil mask 111 is transferred onto the substrate 12 at a predetermined reduction ratio such as 1/10. The substrate deflecting section 150 includes a seventh electromagnetic deflector 119 and an eighth electromagnetic deflector 120. The electron beam EB is deflected by these deflectors 119 and 120, whereby the image of the pattern on the stencil mask 111 is projected in a predetermined position on the substrate. Moreover, the substrate deflecting section 150 is also provided with third and fourth correction coils 117 and 118 configured to correct deflection aberrations of the electron beam EB on the substrate. The digital control unit 200 includes an electron gun control unit 202, an electrooptical system control unit 203, a mask deflection control unit 204, a mask stage control unit 205, a blanking control unit 206, a substrate deflection control unit 207, and a wafer stage control unit 208. The electron gun control unit 202 controls the electron gun 101 and thereby controls an acceleration voltage, beam radiation conditions, and the like of the electron beam EB. The electrooptical system control unit 203 controls parameters including amounts of currents flowing on the electromagnetic lenses 102, 105a, 105b, 107a, 107b, 113, and 121 and thereby adjusts magnifications, focal positions, and the like of electrooptical system formed of these electromagnetic lenses. The blanking control unit 206 controls a voltage to be applied to a blanking deflector so as to deflect the electron beam EB, which has been generated prior to the start of the exposure, onto the shield plate 115 and thereby to prevent the electron beam EB from being applied onto the substrate 12 prior to the exposure. The substrate deflection control unit 207 controls voltages to be applied to the seventh electrostatic deflector 119 and the eighth electrostatic deflector 120 and thereby deflects the electron beam EB in the predetermined position on the substrate 12. The wafer stage control unit 208 moves a the substrate 12 in a horizontal direction by adjusting a drive amount of a drive unit 25 so as to apply the electron beam EB to a desired position on the substrate 12. All of the units 202 to 208 described above are integrally controlled by an integration control system 201 such as a workstation. FIG. 2 shows a block configuration diagram of the stage device on which the sample is to be mounted in the exposure apparatus. The stage device basically includes a gas supply unit 21, a pressure regulator 22, a wafer stage 23, laser interferometers 24, the drive unit 25, and the wafer stage control unit 208. The gas supply unit 21 generates and sends out clean dry air (CDA). The pressure regulator 22 is disposed in the middle of a gas flow path for connecting the gas supply unit 21 to a supply port of an air bearing of the wafer stage 23 and is configured to adjust a pressure of gas to be supplied to the air bearing. The pressure regulator 22 includes an electropneumatic regulator configured to adjust the pressure of gas and to eject the gas at a preset pressure. The laser interferometers 24 are respectively disposed in a position facing a side surface of the wafer stage 23 and another position facing a different side surface perpendicular to the side surface, and are configured to measure the position of the wafer stage 23 and postures (pitching, rolling, and yawing) of the wafer stage 23 from two directions perpendicular to each other. The laser interferometer 24 also is provided above the wafer stage 23 for measuring a height (vertical position) of the wafer stage 23. The wafer stage control unit 208 detects the position of the wafer stage 23 with high accuracy by controlling the gas supply unit 21, the pressure regulator 22, and the laser interferometer 24. FIG. 3 is a schematic configuration diagram of main parts of the stage using the air bearing in the sample stage device. The sample stage includes a slider 35 on which the sample is to be mounted and a square shank (a base member) 34, which are disposed in a vacuum chamber 37. The slider 35 is formed into a frame shape so as to surround the square shank 34 and is configured to move along with the square shank 34. The square shank 34 is disposed on a stone surface plate 32 disposed on a vibration isolated table 31 by use of support rods 33. FIG. 4 is a view for explaining an air servo stage. The square shank 34 and the slider 35 are disposed in the vacuum chamber 37 evacuated with a turbomolecular pump 42. The slider 35 includes air pads 36 configured to emit the air sent from the gas supply unit 21 into the square shank 34, and a differential exhaust unit configured to adjust the pressure of the emitted air so as to prevent the air from flowing out of a clearance between the slider 35 and the square shank 34. The air pads 36 are made of aluminum ceramics or zirconia ceramics, for example, and are provided with openings which determine a state of distribution of the air. The pressure of the air to be supplied to the air pads 36 is 0.5 [MPa], for example. The slider 35 is floated by emitting the air into the air pads 36 through the square shank 34. The differential exhaust unit includes exhaust ports 43, 44, and 45. The pressure of the air is gradually reduced from the clearance to the outside by discharging the air through the exhaust ports 43, 44, and 45. For example, the air pressure is set to 0.1 [MPa] by use of the exhaust port 43 and an exhaust groove 46, then to 400 [Pa] by use of the exhaust port 44 and an exhaust groove 47, and then to 1 [Pa] by use of the exhaust port 45 and an exhaust groove 48. In this way, the air flow on the outside of the clearance becomes 0.0001 [L/min] which means that the air hardly flows there. Hence it is possible to maintain a vacuum state in the vacuum chamber 37. The slider 35 is provided with cylinder spaces (air chambers) 41a to 41d configured to accumulate the air necessary for forming an air cylinder mechanism to move the slider 35. A pressure receiving plate 50 is formed on the square shank 34 in a direction toward the cylinder space 41. FIGS. 5A and 5B are views for explaining a structure of an air servo. FIG. 5A is a vertical sectional view taking along a direction perpendicular to a moving direction of the slider for showing structure of the square shank and the slider related to the air servo while FIG. 5B is a transverse sectional view taken along a direction parallel to the moving direction of the slider. As shown in FIGS. 5A and 5B, pressure receiving plates 50a and 50b are attached to the square shank and do not contact the slider 35 with a gap (a clearance) in a range from 10 to 20 μm. A clearance between the square shank 34 and the slider 35 is set in a range from 3 to 4 μm when floating. Accordingly, the pressure receiving plate 50 is prevented from contacting the slider 35 irrespective of whether the air bearing is floating or not floating. The pressure receiving plate 50 divides the cylinder space 41 into two spaces and the slider 35 is allowed to move in a desired direction by generating a difference in the pressure to be applied to the pressure receiving plate 50 depending on amounts of the air to be supplied to the cylinder spaces. Moreover, the movement of the slider 35 is stopped by setting the difference in the pressure to zero. A stage drive method using the air servo has an advantage that it is easy to obtain high thrust. For example, when the difference in the pressure between the right and left cylinder space is 0.2 MPa and the area of the pressure receiving plate 50 is 28 cm2 (14 cm2 per side), then it is possible to obtain thrust of about 550 N (56 kgf). Therefore, it is possible to accelerate the slider of 50 kg at 1 G or higher. FIG. 6 is a view showing a configuration of a conventional air bearing stage. As shown in FIG. 6, air is supplied to the air pads 36 in the slider 35 through an air supply pipe 61 and piping inside the slider 35. In addition, the air is supplied to the cylinder spaces 41c and 41d of the slider 35 through the air supply pipes 62a, 62b and the piping inside the slider 35. In this way, air supply pipes 61, 62a, and 62b provided in a vacuum chamber 37 moves along movement of the slider 35 and therefore generate bent portions. It is necessary to replace the air supply pipes (61, 62a, and 62b) before these bent portions cause fatigue and rupture. According to this embodiment, an air supply mechanism not requiring such air supply pipes which will be deteriorated by bending actions and the like is provided in the vacuum chamber. Now, the air supply mechanism in the stage device using the air bearing will be described below with reference to FIG. 7 and FIG. 8. FIG. 7 is a view for explaining the stage device using the air bearing of this embodiment. FIG. 7 shows a cross sectional view of a square shank 71 and a slider 72 which are disposed in a vacuum chamber 70. The square shank (base member) 71 is fixed to the vacuum chamber 70 by use of support rods 33 (FIG. 3) and bellows 75. The slider 72 includes air pads 79 and a cylinder space 78 for accumulating air for moving the slider by use of the difference in the pressure of the air, which are located on a surface facing the square shank 71. The square shank 71 includes flow passages 76a to 76f for feeding the air. Moreover, a pressure receiving plate 77 is provided to face the cylinder space 78 of the slider 72. The pressure receiving plate 77 is configured to divide the cylinder space (air chamber) 78 of the slider 72 into two regions. Specifically, the cylinder space 78 is divided into a cylinder space 78a and a cylinder space 78b on an upper side of the slider 72 by a pressure receiving plate 77a when the slider 72 is floating. The pressure applied to the pressure receiving plate 77a varies depending on the amounts of air supplied to the cylinder space (air chamber) 78a and the cylinder space (air chamber) 78b of the slider 72. The slider 72 moves in a right-to-left direction in FIG. 7 by the difference in the pressure. The air in the cylinder space 78a and the cylinder space 78b is supplied through the flow passages provided inside the square shank 71. The flow passage 76a provided inside the square shank 71 is further split into the flow passage 76b and the flow passage 76c inside the square shank 71 and an outlet port 76g for the flow passage 76b is provided in a position facing the cylinder space 78a. Meanwhile, the flow passage 76d provided inside the square shank 71 is further split into the flow passage 76e and the flow passage 76f inside the square shank 71 and an outlet port 76h for the flow passage 76e is provided in a position facing the cylinder space 78b. The outlet port 76g is provided on the left side of the pressure receiving plate 77a in FIG. 7 while the outlet port 76h is provided on the right side of the pressure receiving plate 77a in FIG. 7. These outlet ports 76g and 76h are located very close to the pressure receiving plate 77a. By locating the outlet ports very close to the pressure receiving plate 77a, it is possible to prevent interruption of the air supply to the cylinder spaces 78a and 78b when the slider 72 moves to the right and left. The pressures inside the cylinder spaces are individually controlled by respectively supplying the air to the cylinder spaces 78a and 78b on the right and left of the pressure receiving plate 77a. The air generated by the gas supply unit 21 (FIG. 2) is supplied to the flow passage 76a through piping 73a. The amount of the supplied air is controlled by a servo valve 74a. Similarly, the air generated by the gas supply Unit 21 is supplied to the flow passage 76d through piping 73b. The amount of the supplied air is controlled by a servo valve 74b. A slider located on a lower side in FIG. 7 has a similar configuration to that of the above-described cylinder. Specifically, the square shank 71 includes a pressure receiving plate 77b located on a surface facing a lower side cylinder 72, and the cylinder space 78 of the slider 72 is divided into a cylinder space (air chamber) 78c and a cylinder space (air chamber) 78d by the pressure receiving plate 77b. The pressure applied to the pressure receiving plate 77b varies depending on the amounts of air supplied to the cylinder space (air chamber) 78c and the cylinder space (air chamber) 78d of the slider 72. The slider 72 moves in the right-to-left direction by the difference in the pressure. The amount of the air to be supplied to the cylinder space 78c is set equal to the amount of the air to be supplied to the cylinder space 78a. Likewise, the amount of the air to be supplied to the cylinder space 78d is set equal to the amount of the air to be supplied to the cylinder space 78b. By setting the configurations of the upper and lower cylinder spaces and the upper and lower pressure receiving plates equal to one another, a difference in traveling motion between the upper and lower sliders is avoided. The following effects can be obtained by disposing the upper and lower cylinder spaces. Specifically, while a force attempting to float the slider 72 up from the square shank 71 is generated by the air servo pressures, it is possible to cancel that force by locating the cylinder spaces vertically opposite to each other and thereby to stabilize the clearance between the square shank 71 and the slider 72. Moreover, it is possible to drive the center of gravity of the slider 72 and thereby to suppress vertical vibration such as pitching motion associated with the movement of the slider 72. As described above, since all the piping for supplying the air to the slider 72 are located inside the square shank (base member) 71, it is possible to eliminate the piping in the vacuum chamber 70 for supplying the air, which has been provided in the conventional apparatus, and to avoid occurrence of rupture and other troubles of the conventional piping attributable to bending of the piping associated with the movement of the slider 72. In this way, since there are no movable portions for supplying the air, it is also possible to form the piping inside the square shank 71 by use of metal or ceramics. Hence the operation life of the piping will be virtually infinite. Here, it is also possible to perform the air servo control by supplying the air to any one of the upper and lower cylinder spaces as long as stability of the movement of the slider 72 is ensured. Next, the supply of the air to the air pads 79 of the slider 72 will be described with reference to FIG. 8. FIG. 8 shows a cross-sectional view of the square shank 71 and the slider 72 disposed in the vacuum chamber 70. This cross-sectional view is taken in a different position from that of the cross-sectional view in FIG. 7. The air pads 79 are provided on the surface of the slider 72 facing the square shank 71 and an air supply groove 80 for supplying the air to the air pads 79 are provided on the same surface of the slider 72. The air supplied to the air supply groove 80 is sent to the air pads 79 through piping 81 formed (buried) inside the slider 72. A flow passage 82 for feeding the air to be supplied to the air supply groove 80 is provided inside the square shank 71. A length of the air supply groove 80 in a direction of movement of the slider is set to a sufficient length so as not to interrupt the air supply from the square shank 71 when moving the slider 72. Specifically, it is so designed that an outlet port 83 of the flow passage 82 is always located to face the air supply groove 80 despite the movement of the slider 72. A floating force of the slider 72 generated by the pressure inside the air supply groove 80 can be used directly to cancel an own weight of the slider 72 by providing the air supply groove 80 only in the upper slider 72. For example, if a width of the air supply groove 80 is 2 mm and a length thereof is 300 mm, it is possible to generate a force of 24 kgf in the case of 0.4 MPa. For this reason, if the own weight of the slider 72 is 30 kg, it is possible to substantially cancel the own weight of the slider 72 and to maintain the clearances above and below the slider within proper ranges. When the own weight does not need to be cancelled, the air supply grooves 80 may be provided symmetrically on the upper and lower sliders 72. In this case, it is possible to cancel the air pressures. Here, the air supply groove 80 may be provided on the square shank 71 instead of the slider 72. When the air supply groove is provided on the square shank 71, a groove having the same size as that of the air supply groove 80 in FIG. 8 is formed on a surface of the square shank 71 facing the slider 72. Meanwhile, a suction port for suctioning the air to be supplied to the groove on the square shank 71 is provided on the slider 72. The suction port is connected to the piping 81 inside the slider 72. As described above, since all the piping for supplying the air to the air supply groove 80 of the slider 72 is located inside the square shank 71, it is possible to eliminate the piping inside the vacuum chamber 70 for supplying the air, which has been provided in the conventional apparatus, and to avoid occurrence of rupture and other troubles of the conventional piping attributable to bending of the piping associated with the movement of the slider 72. In this way, since there are no movable portions for supplying the air, it is also possible to form the piping inside the square shank 71 by use of metal or ceramics. Hence the operation life of the piping will be virtually infinite. A second embodiment will describe an XY stage combining the slider mechanisms, which employ the air bearing stage formed of the square shank and the slider as described in the first embodiment. FIG. 9A shows a plan view of an H-type XY stage and FIG. 9B shows a cross-sectional view thereof. As shown in FIGS. 9A and 9B, the XY stage includes slider mechanisms 91a and 91b for an X axis and a slider mechanism 92 for a Y axis. The slider mechanism 91a includes a fixed square shank 91c to be fixed to the inside of a vacuum chamber, and a slider 91d. Similarly, the slider mechanism 91b includes a fixed square shank 91e and a slider 91f. The slider 91d and the slider 91f are configured to move in the same direction at the same time. The slider mechanism 92 includes a square shank 92a, a slider 92b, and a wafer table 93. One end of the square shank 92a is connected to the slider 91d of the slider mechanism 91a through an end plate and the other end thereof is connected to the slider 91f of the slider mechanism 91b through an end plate. This square shank 92a will also be referred to as the movable square shank 92a. The wafer table 93 is provided on a surface of the slider 92b of the slider mechanism 92 and a wafer W is fixed to the wafer table 93 by use of an electrostatic chuck ESC. The wafer W is moved to a desired position defined in XY coordinates by driving the slider mechanisms (91a and 91b) and the slider mechanism 92. As shown in FIG. 9B, the sliders (91d and 91f) on the X axis and the slider 92b on the Y axis are disposed on the same plane. Accordingly, it is possible to align the centers of gravity for driving and to obtain a high motion performance without causing pitching or rolling. Flow passages 94a for discharge to the atmosphere, flow passages 94b for a low vacuum, and flow passages 94c for a medium vacuum are provided inside the fixed square shanks (91c and 91e). Meanwhile, a flow passage for discharge to the atmosphere, a flow passage for a low vacuum, and a flow passage for a medium vacuum are also provided inside the movable square shank 92a and are connected to the corresponding flow passages in the fixed square shanks. FIG. 10 is a view for explaining a problem of conventional air piping in the XY stage, and FIG. 11 is a configuration diagram for explaining an outline of the XY stage according to this embodiment. FIG. 10 shows an example in the case of using the movable square shank 92a provided with the air piping as described in conjunction with the first embodiment. As shown in FIG. 10, piping (96a and 96b) for the air to be supplied to the movable square shank 92a also moves along with the movement of the movable square shank 92a. Specifically, the bent portions are formed on the air piping (96a and 96b) and rupture of the piping and other troubles may occur depending on the number of times of bending actions. Hence the operating life of the stage device is determined by such rupture and the like. On the other hand, in the XY stage device of this embodiment, as shown in FIG. 11, the flow passages for feeding the air are also provided inside the fixed square shanks (91c and 91e) corresponding to the X axis, so as to eliminate the piping (96a and 96b) provided in the chamber and configured to supply the air to the movable square shank 92a. A connection structure of the air flow passages between the movable square shank 92a and the fixed square shanks (91c and 91e) will be described by using FIG. 12. FIG. 12 is a cross-sectional view showing partial cross sections of the X axis and the Y axis of the XY stage. The X axis is formed of the fixed square shank 91c and fixed shank slider 91d formed to surround the fixed square shank 91c in a frame fashion. Meanwhile, an end plate 95a serving as a stopper for the slider 92b is provided on the Y axis side of the fixed shank slider 91d, i.e., on one surface close to the mobile square shank 92a. The first fixed square shaft flow passage 96a is provided in the fixed square shaft 91c along the moving direction of the slider 91d while the second fixed square shaft flow passage 96b is provided in a predetermined position along a direction perpendicular to the fixed square shaft flow passage 96a. The second fixed square shaft flow passage 96b is formed to penetrate the fixed square shank 91c. A first air supply groove 97a is provided on one surface (a surface close to the movable square shaft 92a) out of surfaces of the slider 91d facing the second fixed square shank flow passage 96b and in a position opposed to an outlet port thereof. Meanwhile, a second air supply groove 97c is provided symmetrically on the other surface and in a position opposed to an outlet port. The first air supply groove 97a is provided as the groove having a length covering a range of movement of the movable square shank 92a. Meanwhile, a passage hole 97b for discharging the air is formed from a portion of the first air supply groove 97a to the opposite side of the first air supply groove 97a. Another passage hole 98 configured to penetrate the end plate 95a is provided in a position aligned with this passage hole 97b. An air inlet port for a flow passage 76 inside the movable square shank 92a is connected to the passage hole 98 on the end plate 95a. Air flow passages similar to the above-described air flow passages in the slider mechanism 91a and the end plate 95a are also formed in the slider mechanism 91b and an end plate 95b, and are connected to the flow passage inside the movable square shank 92a. The air generated by the air supply unit 21 (FIG. 2) is supplied to the flow passages 76 inside the movable square shank 92a through the above-described flow passages and the passage holes which are formed in the fixed square shanks (91c and 91e) of the slider mechanism 91a and the slider mechanism 91b, the sliders (91d and 91f) and the end plates (95a and 95b). As described above, the piping buried in the movable square shank is allowed to penetrate from the end plate to the slider for the fixed square shank and is then connected to the piping inside the fixed square shanks. In this way, since all the piping routes are formed inside the square shanks and the sliders, it is possible to eliminate movable portions of the air servo piping that move along with movements of the sliders, whereby there is no piping left in the vacuum chamber. Accordingly, it is possible to eliminate occurrence of rupture and other troubles of the conventional piping attributable to bending of the piping associated with the movement of the sliders. Moreover, since there are no movable portions for supplying the air, it is also possible to form the piping inside the square shanks by use of metal or ceramics. Hence the operation life of the piping will be virtually infinite. It is to be noted that the present invention is a patent application pertaining to the result of research entrusted by the Japanese national government or the like (i.e., a patent application subject to Article 19 of the Industrial Technology Enhancement Act of Japan, pertaining to the research titled “Development of Comprehensive Optimization Technologies to Improve Mask Design, Drawing and Inspection” which is conducted by New Energy and Industrial Technology Development Organization in fiscal year 2009).
054385970	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Transportation and Storage of Failed Fuel Rod Assemblies FIG. 1 shows a transportation and storage assembly indicated generally by reference numeral 20 formed in accordance with the present invention. Transportation and storage assembly 20 is preferably for the storage and transport of failed fuel rod assemblies for a nuclear reactor. However, it will be readily appreciated by those skilled in the art that assembly 20 could also be used for the transportation and storage of undamaged nuclear fuel rod assemblies. For convenient reference, transportation and storage assembly 20 has been divided into two major components, the canister indicated generally by reference numeral 22 and the basket assembly indicated generally by reference numeral 24. Canister 22 includes a substantially cylindrical hollow shell 26. A bottom lid 28 caps the bottom of shell 26, forming a base. Bottom lid 28 has a substantially circular cross section of a diameter approximately equal to the inside diameter of shell 26. Bottom lid 28 is inserted into the bottom end of shell 26 until the generally planar bottom surface of lid 28 is flush with the bottom edge of shell 26. Bottom lid 28 is secured to shell 26 by conventional means, such as welding to form an air-tight seal. After bottom lid 28 has been welded into place, basket assembly 24 is inserted into the top open end of shell 26. Basket assembly 24 includes a plurality of generally circular plates 36 having a plurality of generally square-shaped apertures 38 formed therethrough. The plates 36 are preferably made of stainless steel. Plates 36 include four generally rectangular recesses 40 formed symmetrically around the outside edge of each plate 36, at approximately equal intervals. Rectangular recesses 40 are arranged so that the longer edge of each rectangular recess is generally perpendicular to a diagonal of each plate 36. Preferably, plates 36 are maintained in a spaced-apart axial alignment relative to one another by eight elongate rectangular plates 42. Rectangular plates 42 have a width that is substantially equal to the inside length of each rectangular recess in plates 36. Thus, rectangular recesses 40 receive rectangular plates 42. Hence, the series of plates 36 are attached to each rectangular plate 42 by conventional means such as welding to rigidly maintain plates 36 in a spaced-apart axially-aligned arrangement. In the illustrated embodiment, two plates 42 are stacked on top of one another so that each rectangular recess 40 receives two rectangular plates 42. Alternatively, each recess 40 could receive a single rectangular plate 42 of a greater thickness. Thus, in an alternative embodiment, four thicker rectangular plates 42 could be used, rather than eight plates. The ends of rectangular plates 42 project slightly beyond the surface of the first and last plates 36, as best seen in FIG. 1A. Each plate 36 contains a substantially identical arrangement of square apertures 38. Thus, when the plates are axially aligned relative to one another by plates 42, apertures 38 are axially aligned into a plurality of rows. Inserted into each row is a failed fuel container, indicated generally by reference numeral 44 in FIG. 1. Turning to FIG. 2A, each failed fuel container 44 includes an elongate substantially square-shaped sleeve 46. Square-shaped sleeve 46 is capped at its bottom end by a square-shaped lid 48 that is welded to sleeve 46. Welded to the top end of the sleeve 46 is a square-shaped sleeve 50 that is substantially shorter than sleeve 46. Square-shaped sleeve 50 has internal width dimensions substantially equal to the exterior width dimensions of sleeve 46. Thus, the top end of the longer sleeve 46 is inserted into the bottom end of shorter sleeve 50, whereupon the two sleeves are welded together. The open end of sleeve 50 receives top lid 52 which serves to cap failed fuel container 44. Lid 52 is inserted into the shorter sleeve 50 until a lip 54, best seen in FIG. 2B, contacts the upper edge of sleeve 50. (FIG. 2B is a perspective view, looking towards the lower surface of lid 52.) Referring to FIG. 2B, lid 52 has an insertable portion 56 that is substantially square-shaped, and has a width dimension slightly smaller than the internal width dimension of the shorter square-shaped sleeve 50. Thus, the insertable portion 56 of the lid 52 slidably fits within shorter sleeve 50. Lid 52 includes a beveled portion 58 to facilitate sliding lid 52 into place in the shorter sleeve 50. Returning to FIG. 2A, lid 52 includes a centrally mounted pintle 60, projecting radially from the upper surface of lid 52. Pintle 60 is substantially identical to a conventional control rod cluster pintle so that standard fuel handling tools available at a nuclear reactor can be used to remove and insert lid 52 into shorter sleeve 50. Additionally, lid 52 includes four oval slots 62 formed symmetrically in each vertical wall that define insertable portion 56 of lid 52, best seen in FIG. 2B. When lid 52 is inserted into shorter sleeve 50, oval slots 62 line up with corresponding oval slots 63 formed in each vertical wall of shorter sleeve 50. Hence, the prongs on handling tools can be used to engage slots 62 and 63 when the lid 52 is in place, so that the entire failed fuel 44 container can be manipulated with the tools. Further, slots 62 and 63 may be optionally fitted with a pin (not shown) to lock lid 52 into place on shorter sleeve 50. As is well known by those skilled in the art, fuel rods used by nuclear reactors in the United States comprise a plurality of rods maintained in radially spaced-apart relationship by a plurality of generally square-shaped brackets, having an interior grid that supports each individual fuel rod in the assembly. The internal width dimensions of the square-shaped sleeve 46 are sized preferably so that there is a sliding fit between the square-shaped brackets holding the fuel rods together in the assembly and the internal walls of the square-shaped sleeve 46. The sliding fit is such that there is a small gap between the square-shaped bracket holding the fuel rods together and the internal walls of sleeve 46. Preferably, sleeve 46 is made of stainless steel, but may be made of any material of sufficient structural rigidity that has the capability to significantly impede the passage of neutrons therethrough. Other substances that may be used include cadmium, borated stainless steel, borated ceramic materials, and a layer of borated aluminum sandwiched between structural members, as described later in the discussion of Transportation and Storage for Undamaged Fuel Rod Assemblies. Returning to FIGS. 1 and 1A, a failed fuel container 44 is inserted longitudinally into each row of axially aligned apertures 38. The internal width dimensions of square-shaped apertures 38 is substantially equal to the external width dimensions of square-shaped sleeve 46, such that there is a sliding fit. Failed fuel containers 44 are each inserted into rows of axially aligned apertures 38, until the bottom surface of shorter sleeve 50 contacts the upper surface of upper plate 36. Thus, shorter sleeve 50 serves to limit the depth to which a failed fuel container 44 may be inserted into an axially aligned row of apertures 38. When basket assembly 24 is inserted in shell 26, basket assembly 24 rests on the bottom ends of rectangular plates 42 that project beyond the surface of the last plate 36, as best seen in FIG. 1A. Once inserted in shell 26, basket assembly 24 is sealed in place by a series of items welded to the top end shell 26. The first item welded into place is a siphon tube mounting block 64. Siphon tube mounting block 64 is welded to the inside of shell 26, adjacent to the upper surface of the top plate 36. Welded around the inner periphery of shell 26, at an elevation intermediate the upper and lower surfaces of siphon tube mounting block 64 is a ring 66. Ring 66 includes a cut-out portion for the siphon tube mounting block. The next item is a shield plug 68 which is for preventing the escape of harmful radiation to the environment. Preferably, shield plug 68 includes a layer of lead 70, surrounded on its lower and radial sides by a steel layer 72. Lead layer 70 is sealed on its upper surface by a thinner layer of steel 74, as shown in FIG. 6A. Shield plug 68 is preferably not welded to shell 26 for the following reasons. When shield plug 68 is in place, it is shielding against the escape of harmful radiation from the interior of shell 26. Thus, exposure of personnel to any radiation must be kept at a minimum, requiring that shell 26 be sealed in a minimum of time. Therefore, shield plug 68 is dropped into place, and an inner top cover plate 80 is welded into place over shield plug 68. As inner top cover plate 80 is preferably made only of stainless steel, a simple weld is required because there is no danger of melting lead and causing contamination of the weld. In contrast, welding of shield plug 68 would pose such a danger. The peripheral edge of inner top cover plate 80 includes an essentially rectangular recess 82, that receives the siphon tube mounting block 64, illustrated in FIG. 1. In regard to the type of material comprising storage and transportation assembly 20, preferably the shell 26 is made of stainless steel. Other types of materials e.g. carbon steel, may be used, but stainless steel is preferred for its structural strength, ability to withstand corrosion, ability to significantly impede the passage of neutrons, and ability to withstand welding without a loss of ductility, requiring subsequent heat treatment. In addition, preferably all components that are welded together comprise the same type of material, to avoid complications from different materials that have different material properties, such as different rates of thermal expansion. Therefore, any items welded to the shell 26, such as the siphon tube mounting block 64, the ring 66, the inner top cover plate 80, etc., are also preferably made of stainless steel. In contrast, circular plates 36 and interconnecting rectangular plates 42 are preferably made of a high strength carbon steel, to provide a high strength supporting framework. Since shield plug 68 is not welded to shell 26, steel layers 72 and 74 comprising shield plug 68 may be made of a different material that is less expensive than stainless steel, such as carbon steel. Alternatively, shield plug could be made of solid steel as shown in shield plug 76 in FIG. 5A. Notwithstanding, solid steel shield plug 76 is thicker, relative to shield plug 68 with an interior lead layer 70, because lead has greater shielding capabilities than steel. Referring to FIG. 1, the peripheral edge of shield plug 68 includes an essentially rectangular recess 78 so that shield plug 68 slides over the top of siphon tube mounting block 64. In the foregoing position, shield plug 68 is supported by ring 66, and the step 79, shown in FIG. 10A, in siphon tube mounting block 64. When shield plug 68 is in place on ring 66 and step 79, the clearance between the lower surface of shield plug 68 and each failed fuel container 44 is sufficiently small to prevent the displacement of top lid 52 from each failed fuel container. Typically, fuel rod assemblies are loaded into storage assembly 20 in the fuel pool of a nuclear reactor. Thus, the fuel rod assemblies are loaded into storage assembly 20 under water. The underwater loading makes it necessary to remove the water from canister 22 after the transportation and storage assembly 20 has been removed from the fuel pool. For this purpose, a siphon tube arrangement has been provided in accordance with the present invention. The siphon tube arrangement includes siphon tube mounting block 64 attached to the upper portion of shell 26, adjacent the inner top cover plate 80. Defined longitudinally through the siphon tube mounting block 64 are two passages 84 and 86, shown in FIGS. 10A and 10B. Passages 84 and 86 include right angles, so that there is not a straight through passage which prevents radiation streaming and minimizes the escape of harmful radiation. Additionally, passage 86 includes a T-shaped portion, with one branch of the "T" plugged. The T-shaped portion is included simply for ease of manufacturing purposes because passages 86 and 84 are preferably formed by boring or drilling. Once inner top cover plate 80 has been welded into place, an air-tight interior cavity is formed inside of shell 26, with the only access being through passages 84 and 86 in siphon tube mounting block 64. The siphon tube arrangement includes a siphon tube 88 connected to passage 86 in siphon tube mounting block 64. As can be seen in FIG. 1, siphon tube 88 passes through a generally circular aperture 90 defined in each plate 36. An enlarged view of basket assembly 24 is provided by in FIG. 1A, which also includes an enlarged view of siphon tube 88. The foregoing siphon arrangement is used to remove liquid from canister 22 in the following manner. An air hose (not shown) is connected to passage 84 in siphon tube mounting block 64. Preferably, passage 84 has been threaded and fitted with a "quick-connect and disconnect" fitting, such that an air hose can be rapidly connected and disconnected from the passage. Compressed air, or another gas, is then forced into shell 26, which in turn forces any fluid in the canister to exit through siphon tube 88. To ensure that substantially all liquid is forced out of shell 26, counter bore 92 is formed in the upper surface of bottom lid 28, as shown in FIG. 6B. The bottom end of siphon tube 88 extends below the upper surface of bottom lid 28 into counter bore 92, ensuring that substantially all fluid within shell 22 can be forced out through the siphon tube. Once substantially all liquid has been forced out of shell 22, compressed air, or other gas can be continually forced through passage 84, and out of siphon tube 88 until any remaining liquid has been evaporated. Then, end caps 94, shown in FIG. 10A, are welded over each of passages 84 and 86, forming a completely airtight seal in the interior of shell 26. Shell 26 is then further sealed by welding a substantially circular outer top cover plate 96 around the inner periphery of shell 26 as shown in FIG. 1. As shown in FIG. 1, outer top cover plate 96 is welded over the upper surface of siphon tube mounting block 64 and inner top cover plate 80. As may be readily appreciated by those skilled in the art, canister 22 includes significant amounts of steel and is heavy. Therefore, canister 22 may include lifting lugs 98 to facilitate maneuvering the canister with equipment, as shown in FIGS. 9A and 9B. Preferably, four lifting lugs 98 are attached symmetrically, at substantially equal intervals and elevations around the inner periphery of shell 26. In FIGS. 9A and 9B, the lifting lugs 98 are welded to the inner radial surface of ring 66. Usually, a fuel transportation and storage assembly 20 is placed inside a cask (not shown), when the assembly is used for transportation. Thus, the lifting lugs 98 facilitate the insertion of canister 22 into a cask. The cask provides additional support and protection of the environment from harmful radiation, and the cask includes lifting trunions that facilitate maneuvering the cask with equipment. One such cask is described in an application entitled Transportation and Storage Cask for Spent Nuclear Fuel, filed on Oct. 8, 1993, and assigned U.S. application Ser. No. 08/131973 by Kyle B. Jones, Robert A. Lehnert, Ian D. McInnes, Robert D. Quinn, Steven E. Sisley, and Charles J. Temus. The subject matter of the above-identified application is expressly incorporated herein by reference. When the cask/canister combination is transported on a vehicle, it is typically placed in an impact limiter for further safety. The impact limiter attenuates shocks that might occur during transportation, for example during a vehicle accident, and thus protects the cask/canister combination from damage, and the environment from the escape of harmful radiation. One such impact limiter is described in an application entitled Impact Limiter for Spent Nuclear Fuel Transportation Cask, filed on Oct. 8, 1993 and assigned U.S. application Ser. No. 08/131972 by Robert A. Johnson, Ian D. McInnes, Robert D. Quinn, and Charles J. Temus. The subject matter of the above-identified application is expressly incorporated herein by reference. Bottom cover plate 28 is a sandwiched layer construction as shown in FIG. 6B. The top most layer 108 is steel, while the middle layer 110 is lead, followed by a bottom layer 112 of steel. Generally, top steel layer 108 is welded to the inner surface of shell 26 first. Subsequently, lead is poured over bottom steel layer 112, to form lead layer 110. Layers 110 and 112 are then inserted and layer 112 is welded to shell 26. Welding may be performed with lead incorporated into the bottom lid 28 because at the time the bottom lid is inserted, the shell does not contain fuel rod assemblies. Thus, with no danger of exposure to harmful radiation, more time consuming welding operations can be conducted which reduces the danger of lead contamination of the welds, in contrast to shield plug 68. Alternatively, bottom lid 28 may be composed of all steel layers as shown in FIG. 5B. However, steel does not have the shielding ability of lead, and thus bottom lid 28 of FIG. 5B is thicker relative to bottom lid 28 of FIG. 6A. In FIG. 5B first layer 116 is preferably a stainless steel layer for welding to the inner surface of shell 26. The next layer 118 is less expensive carbon steel, to provide shielding, which is a dissimilar material from shell 26, and therefore is not welded to shell 26. The top-most layer is another stainless steel layer 120, that is welded to shell 26. Finally, bottom lid 28 includes a ram engagement ring 114 in FIGS. 1, 5B, and 6B. Ram engagement ring 114 mates with a hydraulic ram (not shown) for pushing and pulling the canister 22 along its longitudinal axis, for example, to insert into or remove it from a storage site. When basket assembly 24 is inserted into canister 22, rotation of basket assembly 24 relative to canister 22 is prevented by two rectangular keys 100 that project radially from the inner radial surface of shell 26, and ring 66, shown in FIGS. 9A and 9B. Preferably keys 100 are welded to the inner radial surface of the shell 26 at approximately equal elevations and spaced apart 180.degree. around the inner periphery of shell 26. The radially projecting keys 100 are received by two rectangular slots 102 formed in the outer edge of the top-most plate 36 of the basket assembly 24, as illustrated in FIG. 1A. In FIG. 1A, only one slot 102 is visible, the other slot being spaced approximately 180.degree. from slot 102. Preferably, basket assembly 24 is first inserted into shell 26, and then keys 100 are placed in slots 102 and welded to shell 26. Thus, keys 100 serve to prevent rotation of basket assembly 24 relative to canister 22, by bearing against slots 102 in top-most plate 36. As previously noted, transportation and storage assembly 20 is preferably for use with failed fuel rod assemblies. As is well known in the art, a fuel rod includes a hollow tube, termed a cladding layer, that encloses a plurality of pellets comprising a fissionable material. The rods themselves, are arranged in assemblies of several rods, described previously. In some instances, the cladding layer becomes damaged, which is termed a failed fuel rod. Failed fuel rods may permit fissionable material to escape from the rod. Further, in some cases during nuclear reaction of the fuel, the pellets disintegrate into sand-sized particles, capable of easily escaping from a failed fuel rod. As noted in the Background of the Invention, an important part of transporting spent fuel is avoiding criticality. This is achieved by carefully arranging the spent fuel rod assemblies so that there is a minimum distance between each assembly, such that there is little chance of neutron multiplication occurring to the point of criticality. In the case of failed fuel rod assemblies, however, fissionable material can escape from failed rods, and potentially accumulate near enough other fissionable material that criticality is achieved. The storage and transportation assembly 20, however, addresses the foregoing problem by ensuring that substantially all fissionable material from a failed fuel rod assembly is kept confined to a single failed fuel container 44. For this purpose, top and bottom lids 52 and 48 each include four screened passages 104, best seen in FIGS. 2B and 2C. As shown in FIGS. 2B and 2C, the passages are positioned in the surfaces of the top and bottom lids 52 and 48, that are generally parallel to the top and bottom of the canister 22. (FIGS. 2B and 2C are perspective views, looking towards the lower surface of the top and bottom lids 52 and 48.) When liquid is removed from a canister 22, any liquid in the failed fuel containers 44 can drain out through four screened passages 104 in bottom lid 48. However, the screening in passages 104 is fine enough, that any escaped fissionable material from a failed fuel rod is prevented from passing through screened passages 104. Additionally, four vertical rectangular projections 106 along each edge of lid 48, shown in FIG. 2C, on the lower surface of bottom lid 48 ensure that a minimum spacing is maintained between screened passages 104 and the upper surface of bottom lid 28 for canister 22. Alternatively, a single square vertical projection may be used in the center on the lower surface of lid 48. Thus, sufficient spacing is maintained so that liquid in failed fuel container 44 can easily drain out through passages 104. Further, screened passages 104 in top lid 52 permit air, or other gas, to enter the interior of failed fuel container 44, as liquid in failed fuel container 44 is draining out, thus facilitating the draining of liquid from a failed fuel container. As previously noted the clearance between each failed fuel container 44 and shield plug 68 is such to prevent the removal of top lids 52 from each failed fuel container when shield plug 68 is in place. Nonetheless, the surface of each top lid 52 where screened passages 104 are formed, are recessed below a lip 54, as seen in FIGS. 2A and 2B. The foregoing arrangement, thus ensures a sufficient space between screened passages 104 of each top lid 52 and the lower surface of shield plug 68, so that air or other gas can enter the interior of each failed fuel container 44, as liquid drains out. Moreover, the screening in passages 104 of the lid 52, ensure that fissionable material cannot escape from container 44, if the container is oriented in a position such that the upper surface of the top lid 52 is not horizontal, or at an elevation less than that of bottom lid 48. Transportation and Storage of Undamaged Fuel Rod Assemblies While basket assembly 24 is preferably for failed fuel rod assemblies, the basket assembly 122 (indicated generally by reference numeral 122), shown in FIG. 3, is designed for the transportation and storage of undamaged fuel rod assemblies. Basket assembly 122 is inserted into canister 22, shown in FIGS. 1, 9A, and 9B, in the same manner that basket assembly 24 of FIGS. 1 and 1A is inserted. Moreover, the manner of sealing the basket assembly 122 into canister 22, is the same as that described with respect to basket assembly 24. Basket assembly 122 includes a plurality of generally circular plates 124 having a plurality of generally square-shaped apertures 126 formed therethrough. A top view of a single plate 124 is shown in FIG. 7. Plates 124 are maintained in a spaced-apart axial alignment relative to one another by four rods 128 that pass through each plate. Each rod 128 passes through one of the four holes 130 formed in each plate 124. Rods 128 are welded to each plate 124, to prevent movement of the plates 124 relative to rods 128. The plates 124 are preferably made of a high strength carbon steel, and interconnecting rods 128 are preferably made of stainless steel. The holes 130 preferably include an insert, to mitigate complications caused by welding a stainless steel to a high strength carbon steel. Each plate 124 includes a substantially identical arrangement of square apertures 126. Thus, when plates 124 are axially aligned relative to one another by rods 128, apertures 126 are aligned into a plurality of rows. Inserted into each row is a guide sleeve assembly 132, indicated generally by reference numeral 132 in FIG. 3. The top and bottom ends of each rod 128 extend beyond the top and bottom ends of each guide sleeve assembly 132. Thus, when basket assembly 122 is inserted into a shell 26, the bottom ends of rods 128 contact the upper surface of bottom lid 28, maintaining a space between the bottom ends of guide sleeve assemblies 132 and bottom lid 28. Additionally, when shield plug 68 is placed on top of basket assembly 122 while in shell 26, the top ends of the rods 128, and ring 66, support shield plug 68 above the top ends of the guide sleeve assemblies 132. An enlarged view of a part of guide sleeve assembly 132 is shown in FIG. 8A. An assembled view of the assembly of FIG. 8A is shown in FIG. 8B. Each guide sleeve assembly 132 includes an elongated, generally square-shaped inner guide sleeve 134, shown in FIG. 8A. Inner guide sleeve 134 is preferably made of stainless steel, and is inserted into each row of axially aligned square-shaped apertures 126, thus passing through each plate 124. The top end of each guide sleeve 134 includes a flare 140, to facilitate the insertion of a fuel rod assembly, described below. Disposed adjacent each exterior face of inner guide sleeve 134 is a rectangular-sheet 136 of a neutron absorbing material or of aluminum, depending on the location of the rectangular sheet 136. If a rectangular sheet 136 is in a location A, as shown in FIG. 7, that directly faces another row of axially aligned apertures 126, the rectangular sheet is made of a neutron absorbing material. However, if rectangular sheet 136 does not directly face another row of axially aligned apertures 126, e.g., position B in FIG. 7, the rectangular sheet need not be made of neutron poisoning material, but may be made of aluminum, steel, or other structural support material. If the rectangular sheet is made of a neutron poisoning material, preferably the material is borated aluminum. However, any neutron poisoning material may be used such as cadmium, borated stainless steel, borated ceramic materials, etc. Four such rectangular sheets 136 are inserted into each row of axially aligned apertures 126, so that one rectangular sheet 136 is disposed between each exterior face of each inner guide sleeve 134, and each plate 124. Surrounding rectangular sheets 136 and inner guide sleeves 134, are a series of shorter outer guide sleeves 138. An outer guide sleeve 138 surrounds each portion of an inner guide sleeve 134, and the corresponding rectangular sheets 136, that is exposed between an adjacent pair of plates 124. Thus, outer guide sleeves 138 may be of different lengths to account for different spacing between an adjacent pair of plates 124. The ends of each outer guide sleeve 138 include a flare 140 to bear against the surface of each plate 124, best seen in FIG. 4A. The ends of each inner guide sleeve 134 that projects beyond the top and bottom plates 124, are not surrounded by an outer guide sleeve 138. The top projecting end of each inner guide sleeve is surrounded by a finishing cap 142, that is preferably made of steel. The bottom end of each inner guide sleeve is as shown in FIG. 4A. Best seen in FIG. 4A is the that the bottom end of each rectangular sheet 136 includes a rectangular notch 146, for receiving an L-shaped bracket 148. Each bracket 148 is fastened to the inner guide sleeve 134 and to bottom plate 124, which prevents vertical movement of inner guide sleeves 134 and rectangular sheets 136 relative to the plates 124. The brackets 148 may be fastened to the inner guide sleeves 134 and the bottom plate 124 by welding, screws, or any other known manner. As previously noted, items welded together are preferably of the same of material to avoid complications with items having different material properties. Since the inner guide sleeves 134 are preferably made of stainless steel, the brackets 148 may be made of stainless steel and welded to the inner guide sleeves, and screwed to the bottom plate 124, which is preferably made of a high strength carbon steel. As noted previously, basket assembly 122 is inserted into a canister 22, in the same manner as the basket assembly 24 for failed fuel rod assemblies. Once basket assembly 122 for undamaged fuel rod assemblies is inserted into canister 22, undamaged fuel rod assemblies may be inserted into each guide sleeve assembly 132, and canister 22 sealed and siphoned, as described earlier. The multi-layer construction of the guide sleeve assemblies 132, including a neutron poisoning layer (the rectangular sheets 136) in "A" positions, as previously described, provide an additional safety factor against the danger of neutron multiplication to a critical level. Thus, basket assembly 122 in combination with canister 22, may be inserted into a cask, described before, and the cask/canister combination may be used to transport the fuel rod assemblies across areas accessible to the public. Fuel Only Kod Assemblies vs. Fuel Rod Assemblies Including Control Elements As is well know in the art, fuel rod assemblies that include only fuel, are shorter in length than fuel rod assemblies that include control elements. In accordance with the present invention, canister 22 and basket assembly 122 may be used with either type of fuel rod assembly, without any change in the outside dimensions of canister 22. The foregoing is accomplished by the use of the two different shield plugs 76 and 68, shown in FIGS. 5A and 6A, respectively. When canister 22 and basket assembly 122 is to be used with the shorter fuel rod assemblies that include only fuel, all-steel shield plug 76 is used. All-steel shield plug 76 is thicker than shield plug 68 that also includes a lead layer. Thus, thicker shield plug 76 takes up more vertical space in the canister 22, and accounts for the shorter length of the fuel only fuel rod assemblies. Thicker shield plug 76 is preferably used with thicker bottom lid 28, shown in FIG. 5B, that includes only steel layers 116, 118 and 120, as previously described. The thick bottom lid 28, comprising all steel layers, also takes up more vertical space in canister 22, relative to the thinner bottom lid 28, shown in FIG. 6B, that includes a lead layer 110. When basket assembly 122 is to be used with the longer fuel rod assemblies including control elements, thinner shield plug 68 is used, that includes a lead layer 70. Lead has a greater shielding capability, and thus provides the same amount of shielding as the non-lead plug, although the thinner shield plug 68, is significantly thinner relative to the all-steel shield plug 76. Thinner bottom lid 28, incorporating a lead layer 110 is preferably used in combination with thinner shield plug 68. Rather than using shield plug 76 of greater thickness, spacers could be inserted into each guide sleeve assembly 132, that would account for shorter fuel rod assemblies. Further, such spacers, could be used to mix shorter fuel rod assemblies with longer fuel rod assemblies in the same basket assembly. Finally, such spacers could also be used with basket assembly 24 for failed fuel rod assemblies of different lengths. While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
054597676	abstract	An accurate method for testing the strength of nuclear fuel particles. Each particle includes an upper and lower portion, and is placed within a testing apparatus having upper and lower compression members. The upper compression member includes a depression therein which is circular and sized to receive only part of the upper portion of the particle. The lower compression member also includes a similar depression. The compression members are parallel to each other with the depressions therein being axially aligned. The fuel particle is then placed between the compression members and engaged within the depressions. The particle is then compressed between the compression members until it fractures. The amount of force needed to fracture the particle is thereafter recorded. This technique allows a broader distribution of forces and provides more accurate results compared with systems which distribute forces at singular points on the particle. 05459767621 00000000000000000460000000000000000000000000000000000000000000000000000000 000098
	abstract	A light source device that irradiates a discharge vessel with a laser beam to produce radiant light that is reflected by an ellipsoidal reflecting surface efficiently utilizes the light produced by directing the laser beam through an unirradiated region where reflected light from the ellipsoidal reflector is blocked by the discharge vessel, through an opening side of the ellipsoidal reflector to the discharge vessel. The discharge vessel has an emission substance enclosed inside which is excited by the laser beam and produces radiant light, is arranged at a focal point of the ellipsoidal reflector. A planar mirror, with which radiant light reflected by the ellipsoidal reflector is reflected in a different direction has a window in an unirradiated region where reflected light from the ellipsoidal reflector is blocked by the discharge vessel through which the laser beam passes to the discharge vessel.
	description	This invention is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Space and Naval Warfare Systems Center, Pacific, Code 72120, San Diego, Calif., 92152; voice (619) 553-5118; [email protected]. Reference Navy Case Number 100794. The present invention relates to self-contained power cells capable of supplying electrical energy, and more particularly to a compact energy source capable of supplying a low level of energy for a relatively long period of time. Electric power cells provide self-contained sources of electrical energy for driving external loads. Chemical batteries are a common example of a practical electric power cells, in that they are relatively inexpensive to produce and capable of supplying a reasonably high energy output, even though it may be for a relatively short period of time. These batteries are effectively employed in a large variety of applications and environments, which can range in requirements from a very large current demand over a short period of time, such as a heavy-duty fork lift truck, to a small current demand over a long period of time, such as a small wristwatch. While chemical batteries are very effective at providing the power needs of such devices, the size and durational requirements sometimes associated with microelectronic devices are not always compatible with employment of chemical batteries. One example of a microelectronic device possibly requiring a compact, long-life, low-current battery is a nonvolatile memory circuit of a compact computing device. Another example is a low-power electronic sensor which is intended for long term unattended operation in an inaccessible location. The amount of electrical energy supplied by chemical batteries is directly related to the mass of reactive materials incorporated in the chemical batteries. This characteristic can result in the size of a chemical battery being much larger than its load. Even a chemical battery in a modern electronic wristwatch is usually much larger in size and heavier relative to the electronic microchip circuitry which drives the watch. It is therefore desirable to provide a battery that can fit in a very small space, and preferably one which can also provide many years of uninterrupted service. Disclosed herein is a radioisotope-powered energy source comprising: a flexible center substrate, wherein the substrate comprises upper and lower surfaces which are both coated with the radioisotope or have a thin layer of the radioisotope bonded thereto; and two substantially identical sequences of layers bonded to each other and to the upper and lower surfaces via electrically insulating mesh barriers, wherein each sequence comprises the following layers bonded together in a y-direction in the following order: a first low-density alpha particle impact layer, a first high-density beta particle impact layer, a second low-density alpha particle impact layer, a second radioisotope-coated substrate, a third low-density alpha particle impact layer, a second high-density beta particle impact layer, and a photovoltaic layer. FIG. 1 depicts an embodiment of a radioisotope-powered energy source 10, which comprises a radioisotope-coated flexible center substrate 12, and two substantially identical sequences of layers 14. One sequence 14 is bonded to an upper surface 16 of the center substrate 12 via an electrically insulating mesh barrier 18. The other sequence 14 is bonded to a lower surface 20 via another electrically insulating mesh barrier 18. All of the constituent layers of each sequence 14 are also bonded to each other via electrically insulating mesh barriers 18. Each sequence 14 comprises the following layers bonded together in the following order: a first low-density alpha particle impact layer 22, a first high-density beta particle impact layer 24, and a photovoltaic layer 26. The center substrate 12 may be made of any thin flexible material that is capable of carrying a layer of the radioisotope with minimal self-absorption of the emitted alpha particulates. A suitable example of the center substrate 12 is a very thin flexible plastic matrix of a suitable actinide radioisotope. The radioisotope that coats the center substrate 12 may be any radioisotope that emits alpha and beta particles and x-ray/gamma photons. Suitable examples of the radioisotope include, but are not limited to, depleted uranium (i.e. the Radium/Uranium Series, See FIG. 5), a radioisotope from the Thorium series (e.g. Thorium 232), a radioisotope from the Neptunium series (e.g. Np-237), and a radioisotope from the Actinium series (U-235). The radioisotope may be incorporated or coated onto the substrate 12 by a number of methods including but not limited to powder coating or by other methods of adhesion. In reverse, the substrate material(s) themselves may be applied to the radioisotope (depending on whether it is in a solid or powdered form, which would help limit the possibility of contamination. In another embodiment, the substrate 12 may be a very thin layer of the radioisotope itself. The insulating mesh barrier 18 may be any non-conductive barrier suitable for electrically insulating adjoining layers while allowing alpha and beta particles and x and gamma ray photons to pass substantially therethrough. Suitable examples of the mesh barrier 18 include ceramic, fiberglass, polymer or plastic non-conductive materials. Due to the limited range of Alpha and low energy Betas, the mesh should be as thin as practicable. The mesh openings should be sufficient in size and geometry to allow Alpha and Beta particles to pass with minimal obstruction but be sufficient to electrically insulate the Alpha and Beta collection media. The mesh barrier 18 may also serve as a thermal barrier between constituent layers of the sequences 14. The first alpha particle impact layer 22 may be any low-density film capable of interacting with alpha particles emitted from the radioisotope and collecting the positive charge therefrom. Approximately all of the alpha particles emitted by the radioisotope will interact with, and give up their energy to, the first alpha particle impact layer 22. Suitable examples of the first alpha particle impact layer 22 include, but are not limited to, sodium beta-alumina or various silicone devices, Gallium Arsenide (GaAs) diodes, and diamond films. The first alpha particle impact layer 22 may be a solid film or a mesh design. The first beta particle impact layer 24 may be any high-density film capable of interacting with beta particles emitted from the radioisotope and collecting the negative charge therefrom. A high percentage of emitted beta particles (electrons) will pass through the first alpha particle impact layer 22 with no interaction (and therefore no loss of negative charge) and will then interact with the first beta particle impact layer 24, which may be designed to interact with nearly all the incident beta particles that pass through the first alpha particle impact layer 22. Upon impacting the first beta particle impact layer 24, the beta particles will give up their negative charge. Suitable examples of the first beta particle impact layer 24 include, but are not limited to, a film of beryllium, carbon, silver, aluminum, and gold. The photovoltaic layer 26 may be any photocell capable of converting x and gamma ray photons into electrical current. Many commercially-available photovoltaic materials currently exist that would be suitable for the photovoltaic layer 26. A suitable example of the photovoltaic layer includes, but is not limited to a layer of un-doped Lithium Niobate (LiNbO3). U.S. Pat. No. 5,721,462, which issued 24 Feb. 1998 to Howard Shanks, which is incorporated by reference herein, provides instructions on how such a photovoltaic layer may be constructed. FIGS. 2a-2b are illustrations showing how the energy source 10 may be assembled on a flat surface and then rolled into a cylindrical shape to enhance the interactions between the various radioactive emissions of the radioisotope coating and the sequences of layers 14. In this configuration, any high energy beta particles or photons that don't interact with the first particle-specific layer they encounter will have at least one more chance to do so. With respect to drawing scale, it will also be appreciated that the drawings, particularly those showing a rolled configuration, are not in an actual scale, but in a scale selected to best illustrate the invention. More particularly, the respective layers which make up the energy source 10 are on the order of a millimeter or less in thickness, and thus a cylindrical energy source of a given real diameter will usually contain many more layers than are shown in FIGS. 2a-2b. Specifically, FIGS. 2a-2b are intended primarily to illustrate the relationship between the respective layers, and not the number of layers which will make up this particular embodiment of the energy source 10. FIG. 3 illustrates another embodiment of the sequence of layers 14. In this embodiment, the sequence 14, in addition to the layers depicted in FIG. 1, further comprises the following layers interposed between the first beta particle impact layer 24 and the photovoltaic layer 26: a second low-density alpha particle impact layer 28, a second radioisotope-coated substrate 30, a third low-density alpha particle impact layer 32, and a second high-density beta particle impact layer 34. As with the embodiment of the sequence depicted in FIG. 1, each layer is separated from adjoining layers by an insulating mesh barrier 18. Although FIG. 3 illustrates only one sequence 14 bonded to the upper surface 16 of the substrate 12, it is to be understood that this is only for the sake of ease of display and that a complete depiction of the energy source 10 would also include a mirror image of the sequence of layers 14 shown in FIG. 3 bonded to the lower surface 20. FIG. 4 is a cross-sectional view of another embodiment of the energy source 10 showing positive leads 36 and negative leads 38 connected to the various layers. Each alpha particle impact layer 22 has a positive lead 36 connected thereto for conducting positive charge collected from the alpha particles. Each beta particle impact layer 24 has a negative lead 38 connected thereto for conducting negative charge collected from the beta particles. Each photovoltaic layer 26 has a positive lead 36 and a negative lead 38. The positive and negative leads 36 and 38 serve for connection of the energy source 10 to a load. A plurality of energy sources 10 can be formed separately or on the same substrate, and can be interconnected in series or in parallel to derive the necessary voltage and current capacities to meet the requirements of a particular load. FIG. 5 is a table showing the 4n+2 chain of U-238, which is commonly called the “radium series” (or sometimes “uranium series”). Beginning with naturally occurring uranium-238, the radium series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least transiently, in any uranium-containing sample, whether metal, compound, or mineral. From the above description of the energy source 10, it is manifest that various techniques may be used for implementing the concepts of the energy source 10 without departing from its scope. The described embodiments are to be considered in all respects as illustrative and not restrictive. It should also be understood that energy source 10 is not limited to the particular embodiments described herein, but is capable of many embodiments without departing from the scope of the claims.
	claims	1. A system to monitor a control rod movement mechanism of a nuclear power plant, comprising:an electrical connector configured to connect to one or more test points of the control rod movement mechanism;an impedance measuring unit configured to obtain signal values from the test points during operation of the nuclear power plant, and to determine a present impedance of at least one component of the control rod movement mechanism based on obtained signal values; anda control unit configured to compare the present impedance to a reference impedance, and to generate a graphical output indicating degradation of the control rod movement mechanism if the present impedance deviates from the reference impedance by a predetermined amount. 2. The system of claim 1, wherein the impedance measuring unit obtains voltage and current values as the signal values. 3. The system of claim 1, wherein the at least one component of the control rod movement mechanism includes a coil, connector, cable, or any combination thereof. 4. The system of claim 1, wherein the reference impedance corresponds to historical impedance measurements of the control rod movement mechanism during operation of the nuclear power plant. 5. The system of claim 1, further comprising a recording unit configured to record one or more determined impedances corresponding to the at least one component to determine the reference impedance. 6. The system of claim 1, wherein the impedance measuring unit is further configured to measure a resistance of the at least one component to determine a temperature of the at least one component. 7. The system of claim 1, further comprising a graphical output configured to display one or more signal values associated with the at least one component. 8. The system of claim 7, wherein the graphical output includes plotting the one or more signal values over a time period including one or more energy states and transitions between energy states of the at least one component.
	claims	1. A method of judging practical conditions for use of an ordered structure alloy under an irradiation environment, comprising:preparing an irradiated state diagram that expresses for the ordered structure alloy a relation of a degree of long range order S to a variable R of an irradiated state of the ordered structure alloy, related to a damage rate and an irradiation temperature, on basis of an evaluation formula related to an effect of irradiation on the degree of long range order of the ordered structure alloy under irradiation environments by using as parameters, a first threshold value Sth1 at which the degree of long range order begins to decrease, under irradiation, at a rate greater than a rate at which the degree of long range order decreased prior to the first threshold value having been reached, a second threshold value Sth2 at which the degree of long range order is nearer to reaching equilibrium than the degree of long range order was prior to the second threshold value having been reached and after decrease of the degree of the long range order which began at the first threshold value Sth1, and the degree of long range order in an equilibrium state Seq;for irradiation conditions under which the ordered structure alloy is to be used, calculating an R-value, and corresponding to the R-value, finding an S-value, an Sth1-value, an Sth2-value, and an Seq-value; andcomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, to thereby predict a damage level and a variation condition of the damage level of the ordered structure alloy under the irradiation environment. 2. The method according to claim 1, whereincomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, with 0<Seq-value<Sth2-value<Sth1-value<1, and considering a magnitude relation of these values, results in the following judgments being made(i) when Sth1-value<S-value, the ordered structure alloy is in an ordered state and has a large degree of long range order, corresponding to a low damage level,(ii) when Sth2-value<S-value<Sth1-value, the ordered structure alloy is in a transition process from an ordered state to a disordered state and the degree of long range order decreases, corresponding to a damage level of the alloy fluctuating greatly and tending to increase rapidly,(iii) when Seq-value<S-value<Sth2-value, the ordered structure alloy is in a process of reaching a disordered state and an amount of a decrease in the degree of long range order is small while the degree of long range order is small, corresponding to a damage level of the alloy being large but fluctuating little, and(iv) when S-value<Seq-value, the ordered structure alloy is in a disordered state and the degree of long range order is small, corresponding to a high damage level. 3. The method according to claim 2, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 4. The method according to claim 1, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 5. A method of judging practical conditions for use of an ordered structure alloy under an irradiation environment, comprising:preparing an irradiated state diagram that expresses for the ordered structure alloy a relation of a damage rate to a reciprocal of an irradiation temperature on basis of an evaluation formula, related to an effect of irradiation on a degree of long range order S of the ordered structure alloy under irradiation environments, by using as parameters, a first threshold value Sth1 at which the degree of long range order begins to decrease, under irradiation, at a rate greater than a rate at which the degree of long range order decreased prior to the first threshold value having been reached, a second threshold value Sth2 at which the degree of long range order is nearer to reaching equilibrium than the degree of long range order was prior to the second threshold value having been reached and after decrease of the degree of the long range order which began at the first threshold value Sth1, and the degree of long range order in an equilibrium state Seq;for irradiation conditions under which the ordered structure alloy is to be used, calculating a value of the reciprocal of an irradiation temperature of the ordered structure alloy, and corresponding to the value of the reciprocal of the irradiation temperature, finding an S-value, an Sth1-value, an Sth2-value, and an Seq-value; andcomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, to thereby predict a damage level and a variation condition of the damage level of the ordered structure alloy under the irradiation environment. 6. The method according to claim 5, whereincomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, with 0<Seq-value<Sth2-value<Sth1-value<1, and considering a magnitude relation of these values, results in the following judgments being made(i) when Sth1-value<S-value, the ordered structure alloy is in an ordered state and has a large degree of long range order, corresponding to a low damage level,(ii) when Sth2-value<S-value<Sth1-value, the ordered structure alloy is in a transition process from an ordered state to a disordered state and the degree of long range order decreases, corresponding to a damage level of the alloy fluctuating greatly and tending to increase rapidly,(iii) when Seq-value<S-value<Sth2-value, the ordered structure alloy is in a process of reaching a disordered state and an amount of a decrease in the degree of long range order is small while the degree of long range order is small, corresponding to a damage level of the alloy being large but fluctuating little, and(iv) when S-value<Seq-value, the ordered structure alloy is in a disordered state and the degree of long range order is small, corresponding to a high damage level. 7. The method according to claim 6, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 8. The method according to claim 5, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms.
041860489	summary	This invention relates generally to nuclear reactors and, more particularly, to an improved neutron flux monitoring system for use with a nuclear reactor. Normal operation of a nuclear reactor, particularly a power reactor, may be divided broadly into three ranges; source or start-up range, intermediate range and power range. In order to indicate the power level in the reactor at all times to permit safe control, the neutron flux in the reactor is monitored. The neutron flux at any point in the reactor is proportional to the fission rate and hence also to the power level. Because of the extreme temperatures and radiation levels in the core, the neutron sensors used for start-up and safety operation are usually placed outside the core. Typical neutron flux measurements in the intermediate range and in the power range are achieved utilizing fission chambers. These fission chambers, which are well known in the art, for practical reasons are placed at specific locations outside but adjacent to the reactor core. It is customary to have an array of detectors both vertical and around the core so that a relatively accurate picture of the flux distribution in the reactor core may be obtained during start-up and power operation of the reactor. The array of fission chambers are also required to provide (usually four) independent and redundant flux measurements for reactor safety purposes. As is known to those skilled in the art, the output of the electronic circuits used with the fission chambers may be logarithmic (used during the rise to power) or linear (used at or near the full power level). Count rate circuits are typically utilized in the low ranges of flux whereas Campbelling type circuitry or d.c. current techniques may be required for the higher flux ranges, where pulse resolution becomes a problem. In the shutdown condition of the reactor, the source level neutron flux is typically at an extremely low level, and because the detectors used for flux monitoring in the higher ranges have such low sensitivity, a separate low level monitoring system has typically been required. In the past, prior art systems in this lower flux range of reactor operation have employed high sensitivity proportional counters feeding locally mounted preamplifiers which deliver signals through coaxial cables to count rate circuits mounted in the control room. Such proportional counters have exhibited significant disadvantages as a result of short operating life and being highly susceptible to gamma background radiation. Moreover, because separate placements, preamplifiers and wiring are required for such a separate system, a significant added cost results. It is an object of the present invention to provide a means for combining the pulse signals from the array of independent fission chamber assemblies placed around the core for power range monitoring and safety purposes to achieve a high system sensitivity to neutrons in the source range and in the shutdown condition without violating their independence. It is a further object of the invention to provide an inexpensive, reliable neutron flux monitoring system capable of measuring the full range of neutron flux in a nuclear reactor, including very low levels of neutron flux.
	summary
048062790	claims	1. A method of producing impregnated synthetic rock precursor comprising: feeding particulate synthetic rock precursor into a vibratory conveying means having an elongated path along which the particulate material is progressively moved under vibration, spraying the particulate material with a liquid comprising radioactive waste over an extended region of the elongated path such that the liquid is absorbed into the particulate material which continues to advance to the discharge end of the device, applying heat over an extended region of said elongated path for maintaining the synthetic rock precursor in a substantially dry state and causing evaporation of water contained in said liquid, and discharging the impregnated synthetic rock precursor. 2. A method as claimed in claim 1 characterised by the continuous vibratory conveying means having an elongated path extending from spaced upstream and downstream ends. 3. A method as claimed in claim 1 or claim 2 characterised by a temperature of the order of 300.degree. C. being established in the synthetic rock precursor passing along said elongated path. 4. A method as claimed in claim 3, characterised in that the conveying means used has a generally trough-like form and has a vibrating element connected thereto near its upstream end, the downstream end of the vibratory conveyor being mounted and supported in flexible mountings and remaining substantially stationary. 5. A method as claimed in claim 5, characterised by the conveyor means using a multiplicity of spray heads spaced along and above said elongated path for spraying said liquid. 6. A method as claimed in claim 5 and characterised by including taking synthetic rock precursor in powder form and forming the precursor into a granu1ated form and supplying the granulated form of the precursor to be fed into said vibratory conveying means. 7. A method as claimed in claim 6, further characterised by advancing said impregnated synthetic rock precursor in flowable particulate form into an elongated downwardly inclined tubular duct, establishing vibration of the tubular duct and applying high level heating so as to calcine the synthetic rock precursor during its passage along said duct, and disoharging the calcined synthetic rock precursor at the downstream end of the duct. 8. A method as claimed in claim 7 and characterised in that said applied high level heating establishes a temperature of the order of 750.degree. C. in the synthetic rock precursor passing down the duct. 9. A method as claimed in claim 7 and characterised in that said step of establishing vibration of the tubular duct is effected by a vibrator unit connected to the downstream region of the tubular duct, the upstream end of the tubular duct being mounted in flexible mountings and the method further comprising adjusting the frequency of vibrations to control the flow rate of the synthetic rock precursor. 10. A method as claimed in claim 9 and characterised by using a gas circulation system through said tubular duct and controlling the atmosphere within the tubular duct, gas extracted from the tubular duct being filtered to remove volatile radioactive components taken up from the radioactive waste content of the synthetic rock precusor. 11. A method as claimed in claim 10 and characterised by mixing titanium powder into the discharged calcined synthetic rock precursor by using a vibratory conveyor which is downwardly inclined in the downstream direction, the titanium powder being mixed into the synthetic rock precursor near the upstream end of said vibratory conveyor. 12. A method of producing canisters containing compacted, impregnated synthetic rock precursor, the precursor being impregnated with radioactive waste and the canisters being adapted to be treated in a hot pressing operation whereby the radioactive waste is immobilised in a matrix of synthetic rock in the canisters, the method characterised by processing synthetic rock precursor by a method as claimed in claim 11 and further comprising pouring the synthetic rock precursor into a canister having a generally cylindrical form with a bellows like cylindrical wall and flat end walls, closing the canister after pouring the synthetic rock precursor into the canister and effecting a cold precompaction by uniaxial pressing along the axis of the canister. 13. A method as claimed in claim 12 and characterised in that the cold precompaction of each bellows canister is effected using an apparatus comprising a hydraulic press having an upwardly acting ram with a refractory facing thereon for supporting the bottom of the canister, a fixed top abutment, a heating zone immediately below the abutment and adapted to surround the bellows container during the hot uniaxial pressing process and a retractable platen adapted to be inserted laterally into the press below the heating zone such that a bellows canister can be placed on the refractory facing and partially compressed at ambient temperature by upward displacement of the hydraulic press, the platen being removable to permit the press to be displaced upwardly to a higher level whereby the bellows-like canister is inserted within the heating zone and abuts against the top abutment. 14. A method as claimed in claim 8 and characterized in that said step of establishing vibration of the tubular duct is effected by a vibrator unit connected to the downstream region of the tubular duct, the upstream end of the tubular duct being mounted in flexible mountings and the method further comprising adjusting the frequency of vibrations to control the flow rate of the synthetic rock precursor.
	abstract	A method of irradiating a target tissue in a patient comprising positioning the patient on a patient support system so that the target tissue in the patient is within irradiating distance of at least one source of a beam of radiation and moving the patient support system relative to the at least one source of a beam of radiation and, coordinately with movement of the patient support system, rotating the at least one source of radiation relative to the target tissue, which comprises and/or is adjacent to a non-target tissue, so that the center of rotation of the beam of radiation is placed at one or more desired locations within the target tissue, while simultaneously and/or sequentially irradiating the target tissue; a collimator; a method of making such a collimator; a system for irradiating a target tissue in a patient; and a method of planning irradiation of a target tissue in a patient.
	summary
	summary
	abstract	The invention is directed to an x-ray flux management device that adaptively attenuates an x-ray beam to limit the incident flux reaching a subject and radiographic detectors in potentially high-flux areas while not affecting the incident flux and detector measurements in low-flux regions. While the invention is particularly well-suited for CT, the invention is also applicable with other x-ray imaging systems. In addition to reducing the required detector system dynamic range, the present invention provides an added advantage of reducing radiation dose.
	summary
051805278	abstract	The present invention provides improved nuclear fuel pellets having high thermal conductivity for use in an LWR. This can be achieved by creating a continuous deposition phase of high-thermal conductivity substances in the grain boundaries in the pellets. As a result, the temperature in the center of the fuel rod can be significantly reduced, and the discharge amount of gases generated on the nuclear fission can be efficiently reduced.. The present invention also provides a method of manufacturing the above-described nuclear fuel pellets.
	abstract	A thermal control system for a reactor pressure vessel comprises a plate having a substantially circular shape that is attached to a wall of the reactor pressure vessel. The plate divides the reactor pressure vessel into an upper reactor pressure vessel region and a lower reactor pressure vessel region. Additionally, the plate is configured to provide a thermal barrier between a pressurized volume located within the upper reactor pressure vessel region and primary coolant located within the lower reactor pressure vessel region. One or more plenums provide a passageway for a plurality of heat transfer tubes to pass through the wall of the reactor pressure vessel. The plurality of heat transfer tubes are connected to the plate.
	summary
	claims	1. A method for mounting at least one radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface;(b) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face, a lower face and at least one mounting hole or slot that extends at least partially through the radiation treatment block mounting plate from its upper surface, and wherein said mounting hole or slot is positioned to permit radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(c) providing at least one affixing means for compressibly affixing said radiation treatment block to said radiation treatment block mounting plate, wherein said affixing means has an upper portion and a lower portion;(d) placing the bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) attaching said upper portion of said affixing means to said radiation treatment block;(f) placing said lower portion of said affixing means through said mounting hole or slot present in said radiation treatment block mounting plate;(g) securing said lower portion of said affixing means to said radiation treatment block mounting plate; and(h) adjusting said affixing means to compressibly and releasably affix said radiation treatment block to said radiation treatment block mounting plate. 2. The method of claim 1 wherein at least one mounting hole or slot extends through said radiation treatment block mounting plate from said upper face to said lower face. 3. The method of claim 1 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 4. The method of claim 3 wherein at least one mounting hole or slot extends through said radiation treatment block mounting plate from said upper face to said lower face. 5. The method of claim 1 wherein said upper portion of said affixing means is attached to said top surface of said radiation treatment block. 6. The method of claim 1 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 7. The method of claim 6 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 8. A method for mounting at least one radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face and at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving one or more external clamping means, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface;(c) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(d) providing external clamping means for compressibly affixing each radiation treatment block to said upper face of said radiation treatment block mounting plate;(e) attaching said external clamping means to said radiation treatment block mounting plate;(f) positioning said external clamping means on each radiation treatment block;(g) adjusting said external clamping means to compressibly affix said radiation treatment block to said upper face of the radiation treatment block mounting plate. 9. The method of claim 8 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 10. The method of claim 8 wherein said external clamping means is a clamp, a pivot clamp, a hook clamp, a toggle clamp, a nylon tie or a swing clamp. 11. The method of claim 8 wherein at least one piece of compressible material is positioned at least partially between the bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 12. The method of claim 11 wherein said compressible material is an elastomeric washer. 13. The method of claim 8 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 14. The method of claim 13 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 15. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device having an end portion sized and shaped to fit within a mounting hole or slot for securing said clamping device to said radiation treatment block mounting plate and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) positioning said end portion of said clamping device through a mounting hole or slot and securing said clamping device to said radiation treatment block mounting plate;(f) positioning said opposite end portion of said clamping device above and adjacent to said top surface of said radiation treatment block; and(g) adjusting said clamping device until at least part of said opposite end portion of said clamping device engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 16. The method of claim 15 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 17. The method of claim 15 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 18. The method of claim 17 where said compressible material is an elastomeric washer. 19. The method of claim 15 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 20. The method of claim 19 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 21. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, wherein at least one clamping device comprises a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate,(e) inserting said threaded end portion of said shaft through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to at least one side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of said shaft;(g) positioning said shaft until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 22. The method of claim 21 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 23. The method of claim 21 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 24. The method of claim 21 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said shaft through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 25. The method of claim 21 wherein said shaft of said clamping device is flexible. 26. The method of claim 25 wherein said opposite end portion of said shaft sized and shaped to engage said top surface of said radiation treatment block is substantially hook shaped. 27. The method of claim 25 wherein said opposite end portion of said shaft sized and shaped to engage said top surface of said radiation treatment block is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 28. The method of claim 27 wherein said angle α is about 90 degrees. 29. The method of claim 21 wherein said shaft of said clamping device is bent. 30. The method of claim 29 wherein said opposite end portion of said shaft sized and shaped to engage said top surface of said radiation treatment block is substantially hook shaped. 31. The method of claim 29 wherein said opposite end portion of said shaft sized and shaped to engage said top surface of said radiation treatment block is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 32. The method of claim 31 wherein said angle α is about 90 degrees. 33. The method of claim 21 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 34. The method of claim 33 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 35. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, wherein at least one clamping device comprises a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of said shaft through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of said shaft;(g) positioning said shaft of said clamping device until said shaft is positioned at least partially in said groove and said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 36. The method of claim 35 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 37. The method of claim 35 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 38. The method of claim 35 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said shaft through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 39. The method of claim 35 wherein said groove is rectangular shaped. 40. The method of claim 35 wherein said groove is U-shaped. 41. The method of claim 35 wherein said groove is V-shaped. 42. The method of claim 35 wherein said radiation treatment block has four side surfaces. 43. The method of claim 35 wherein each side surface has at least one groove positioned therein. 44. The method of claim 35 wherein said shaft of said clamping device is flexible. 45. The method of claim 44 wherein said opposite end portion of said shaft is substantially hook shaped. 46. The method of claim 44 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 47. The method of claim 46 wherein said angle α is about 90 degrees. 48. The method of claim 35 wherein said shaft of said clamping device is bent. 49. The method of claim 48 wherein said opposite end portion of said shaft is substantially hook shaped. 50. The method of claim 48 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 51. The method of claim 50 wherein said angle α is about 90 degrees. 52. The method of claim 35 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 53. The method of claim 52 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 54. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate,(e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to at least one side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of said rod;(g) pivoting said shaft of said clamping device until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said threaded nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 55. The method of claim 54 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 56. The method of claim 54 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 57. The method of claim 54 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said rod through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 58. The method of claim 54 wherein said radiation treatment block has four side surfaces. 59. The method of claim 54 wherein said opposite end portion of said shaft is substantially hook shaped. 60. The method of claim 54 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 61. The method of claim 60 wherein said angle α is about 90 degrees. 62. The method of claim 54 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 63. The method of claim 62 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 64. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of said rod;(g) pivoting said shaft of said clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 65. The method of claim 64 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 66. The method of claim 64 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block and said mounting face. 67. The method of claim 64 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said rod through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 68. The method of claim 64 wherein said groove is rectangular shaped. 69. The method of claim 64 wherein said groove is U-shaped. 70. The method of claim 64 wherein said groove is V-shaped. 71. The method of claim 64 wherein said radiation treatment block has four side surfaces. 72. The method of claim 64 wherein said opposite end portion of said shaft is substantially hook shaped. 73. The method of claim 64 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 74. The method of claim 73 wherein said angle α is about 90 degrees. 75. The method of claim 64 wherein each side surface has at least one groove positioned therein. 76. The method of claim 64 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 77. The method of claim 76 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 78. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having a plurality of mounting holes or slots extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting holes or slots being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and four side surfaces, each side surface having a groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing four clamping devices to externally affix said radiation treatment block to said radiation treatment block mounting plate, each clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite substantially hook shaped end portion;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of each rod of each clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of each rod;(g) pivoting said shaft of each clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said substantially hook shaped end portion of each shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said nut on said threaded end portion of each rod until at least part of each substantially hook shaped end portion of each shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 79. The method of claim 78 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 80. The method of claim 78 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 81. The method of claim 78 where an elastomeric washer is provided for each of said clamping devices, each elastomeric washer having an opening therein, inserting said threaded end portion of said rod through said opening and positioning each elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 82. The method of claim 78 wherein said groove is rectangular shaped. 83. The method of claim 78 wherein said groove is U-shaped. 84. The method of claim 78 wherein said groove is V-shaped. 85. The method of claim 78 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 86. The method of claim 85 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 87. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least three side surfaces, the intersection of a side surface with another side surface forming a corner edge, said radiation treatment block having a groove positioned on at least one corner edge, said groove extending from said top surface to said bottom surface and projecting from said corner edge into said radiation treatment block, said groove sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, said clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion shaped and sized to engage said top surface of said radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot positioned proximate to a groove in a corner edge;(f) attaching a threaded nut onto said threaded end portion of said rod;(g) pivoting said shaft of said clamping device until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; and(h) adjusting said nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 88. The method of claim 87 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 89. The method of claim 87 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 90. The method of claim 87 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said rod through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 91. The method of claim 87 wherein said opposite end portion of said shaft is substantially hook shaped. 92. The method of claim 87 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 93. The method of claim 92 wherein said angle α is about 90 degrees. 94. The method of claim 87 wherein said groove is rectangular shaped. 95. The method of claim 87 wherein said groove is U-shaped. 96. The method of claim 87 wherein said groove is V-shaped. 97. The method of claim 87 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 98. The method of claim 97 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 99. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate having a plurality of mounting holes or slots extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting holes or slots being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting tray;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least three side surfaces, the intersection of a side surface with another side surface forming a corner edge, said radiation treatment block having a groove positioned on at least one corner edge, said groove extending from said top surface to said bottom surface and projecting from said corner edge into said radiation treatment block, said groove sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, said clamping device comprising a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of the radiation treatment block;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of said shaft of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot positioned proximate to a groove in a corner edge;(f) attaching a threaded nut onto said threaded end portion of said shaft;(g) positioning said shaft of said clamping device until said shaft is positioned at least partially in said groove and said opposite end portion of said shaft is positioned above and adjacent to said top surface of radiation treatment block;(h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 100. The method of claim 99 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 101. The method of claim 99 wherein at least one piece of compressible material is positioned at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 102. The method of claim 99 where an elastomeric washer is provided for at least one of said clamping devices, said elastomeric washer having an opening therein, inserting said threaded end portion of said rod through said opening and positioning said elastomeric washer at least partially between said bottom surface of said radiation treatment block and said upper face of said radiation treatment block mounting plate. 103. The method of claim 99 wherein said shaft of said clamping device is flexible. 104. The method of claim 103 wherein said opposite end portion of said shaft is substantially hook shaped. 105. The method of claim 103 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 and about 120 degrees. 106. The method of claim 105 wherein said angle α is about 90 degrees. 107. The method of claim 99 wherein said shaft of said clamping device is bent. 108. The method of claim 107 wherein said opposite end portion of said shaft is substantially hook shaped. 109. The method of claim 107 wherein said opposite end portion of said shaft is a substantially lever shaped end portion, said substantially lever shaped end portion and said shaft forming an angle α, said angle α being between about 60 degrees and about 120 degrees. 110. The method of claim 109 wherein said angle α is about 90 degrees. 111. The method of claim 99 wherein said groove is rectangular shaped. 112. The method of claim 99 wherein said groove is U-shaped. 113. The method of claim 99 wherein said groove is V-shaped. 114. The method of claim 99 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 115. The method of claim 114 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 116. A method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising:(a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving an external clamping device, said mounting hole or slot positioned to allow the mounting of radiation treatment blocks having different sizes to said radiation treatment block mounting plate;(b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove;(c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite oversized end portion, at least one dimension of said oversized end portion being greater than a dimension of said groove;(d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate;(e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block;(f) attaching a threaded nut onto said threaded end portion of said rod;(g) pivoting said shaft of said clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said oversized end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block;(h) adjusting said nut on said threaded end portion of said rod until said oversized end portion of said shaft engages said top surface of said radiation treatment block or one or more face of said groove and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. 117. The method of claim 116 wherein said radiation treatment block mounting plate has at least one mounting hole and at least one mounting slot. 118. The method of claim 116 wherein said radiation treatment block has a ridge protruding from a side surface, said ridge extending from said top surface to said bottom surface of said radiation treatment block. 119. The method of claim 118 wherein said radiation treatment block mounting plate has a radiation treatment block alignment line marked or scribed on said upper face, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of radiation treatment blocks having different sizes is aligned over said radiation treatment block alignment line when said radiation treatment blocks are affixed to said upper face of said plate. 120. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one radiation treatment block mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate;(c) means to releasably secure said plate to said frame body, said means allowing said plate to move relative to said frame body when in a released position and when in a fastened position said means compressibly secures said plate to said frame body. 121. The adjustable radiation treatment block mounting tray as in claim 120 wherein said plate has at least one mounting hole and at least one mounting slot. 122. The adjustable radiation treatment block mounting tray as in claim 120 wherein said means to releasably secure said plate to said frame body is a clamp, a cam clamp, a threaded fastener, a bolt and nut, or a screw. 123. The adjustable radiation treatment block mounting tray as in claim 122 wherein said screw is a thumb screw, a knurled head screw, or a knob screw. 124. The adjustable radiation treatment block mounting tray as in claim 120 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 125. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, and at least one bore for receiving a releasable fastener therein;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body;(c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, wherein a diameter of said orifice is larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body. 126. The adjustable radiation treatment block mounting tray as in claim 125 wherein said plate has at least one mounting hole and at least one mounting slot. 127. The adjustable radiation treatment block mounting tray as in claim 125 wherein at least one bore in said frame body is threaded. 128. The adjustable radiation treatment block mounting tray as in claim 125 wherein said releasable fastener is a screw, a thumb screw, a knurled head screw, a knob screw, an adjustable diameter pin, a cam clamp, or a bolt. 129. The adjustable radiation treatment block mounting tray as in claim 125 wherein said plate has four orifices. 130. The adjustable radiation treatment block mounting tray as in claim 125 further comprising at least one spring attachment fitting affixed to said top face of said upper frame body member, at least one spring attachment fitting affixed to said upper face of said plate, and a spring, said spring connecting a spring attachment fitting affixed to said top face of said upper frame body member to a spring attachment fitting affixed to said upper face of said plate. 131. The adjustable radiation treatment block mounting tray as in claim 130 wherein said spring attachment fitting is a screw, a bolt, or a rod. 132. The adjustable radiation treatment block mounting tray as in claim 125 wherein said plate has one or more notch positioned on at least one outer edge of said plate, said notch positioned to align over a spring attachment fitting affixed to said frame body. 133. The adjustable radiation treatment block mounting tray as in claim 125 wherein said frame body or said plate or optionally both said frame body and said plate has at least one measuring gauge positioned thereon to allow an extent of movement of said plate relative to said frame to be observably measured. 134. The adjustable radiation treatment block mounting tray as in claim 125 further comprising a plurality of rail mounting bores in said upper frame body or lower frame body members and optionally in both upper and lower frame body members for receiving a fastener therein, at least one rail positioned on said upper frame body member or lower frame body member and optionally on both upper and lower frame body members, each rail extending beyond an outer edge of said upper or lower frame body member to adapt a dimension of said frame body to fit within a radiation treatment machine, each rail having a plurality of rail mounting holes for receiving a fastener there through, each rail being affixed to said upper or lower frame by at least one fastener that extends through a rail mounting hole and into a rail mounting bore in said upper or lower frame body member. 135. The adjustable radiation treatment block mounting tray as in claim 134 wherein said fastener is a releasable fastener to releasably affix said rail on said upper or lower frame body member. 136. The adjustable radiation treatment block mounting tray as in claim 134 wherein said rail has one or more identifying mark or color that correlates said rail to a particular manufacturer or model number of a radiation machine. 137. The adjustable radiation treatment block mounting tray as in claim 125 wherein said frame body has a slotted orifice positioned in at least one side frame body member, said slotted orifice forming a handle portion in said side frame body member, said handle portion optionally having at least one hole present therein for mounting one or more handle fitting thereto. 138. The adjustable radiation treatment block mounting tray as in claim 125 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 139. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, a generally central opening and least one bore for receiving a releasable fastener therein;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body;(c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body. 140. The adjustable radiation treatment block mounting tray as in claim 139 wherein said plate has at least one mounting hole and at least one mounting slot. 141. The adjustable radiation treatment block mounting tray as in claim 139 wherein at least one bore is threaded. 142. The adjustable radiation treatment block mounting tray as in claim 139 wherein said releasable fastener is a screw, a thumb screw, a knurled head screw, a knob screw, an adjustable diameter pin, a cam clamp, or a bolt. 143. The adjustable radiation treatment block mounting tray as in claim 139 wherein said plate has four orifices. 144. The adjustable radiation treatment block mounting tray as in claim 139 further comprising at least one spring attachment fitting affixed to said top face of said upper frame body member, at least one spring attachment fitting affixed to said upper face of said plate, and a spring, said spring connecting a spring attachment fitting affixed to said top face of said upper frame body member to a spring attachment fitting affixed to said upper face of said plate. 145. The adjustable radiation treatment block mounting tray as in claim 144 wherein said spring attachment fitting is a screw, a bolt, or a rod. 146. The adjustable radiation treatment block mounting tray as in claim 139 wherein said plate has one or more notch positioned on at least one outer edge of said plate, said notch being positioned to align over a spring attachment fitting affixed to said frame body. 147. The adjustable radiation treatment block mounting tray as in claim 139 wherein said frame body or said plate or optionally both said frame body and said plate has at least one measuring gauge positioned thereon to allow an extent of movement of the plate relative to the frame to be observably measured. 148. The adjustable radiation treatment block mounting tray as in claim 139 further comprising a plurality of rail mounting bores in said upper frame body or lower frame body members and optionally in both upper and lower frame body members for receiving a fastener therein, at least one rail positioned on said upper frame body member or lower frame body member and optionally on both upper and lower frame body members, each rail extending beyond an outer edge of said upper or lower frame body member to adapt a dimension of said frame body to fit within a radiation treatment machine, each rail having a plurality of rail mounting holes for receiving a fastener there through, each rail being affixed to said upper or lower frame by at least one fastener that extends through a rail mounting hole and into a rail mounting bore in said upper or lower frame body member. 149. The adjustable radiation treatment block mounting tray as in claim 148 wherein said fastener is a releasable fastener to releasably affix said rail on said upper or lower frame body members. 150. The adjustable radiation treatment block mounting tray as in claim 148 wherein said rail has one or more identifying mark or color that correlate said rail to a particular manufacturer or model number of a radiation machine. 151. The adjustable radiation treatment block mounting tray as in claim 139 wherein said frame body has a slotted orifice positioned in at least one side frame body member, said slotted orifice forming a handle portion in said side frame body member, said handle portion optionally having at least one hole present therein for mounting one or more handle fitting thereto. 152. The adjustable radiation treatment block mounting tray as in claim 139 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 153. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, opposing side frame body members, a generally central opening, and a plurality of bores for receiving a releasable fastener therein;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and four orifices extending through said plate from said upper face to said lower face, each orifice positioned over a bore in said frame body;(c) four releasable fasteners to releasably secure said plate to said frame body, each releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, each shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position, said releasable fasteners and washers compressibly secure said plate to said frame body. 154. The adjustable radiation treatment block mounting tray as in claim 153 wherein said plate has at least one mounting hole and at least one mounting slot. 155. The adjustable radiation treatment block mounting tray as in claim 153 wherein at least one bore in said frame body is threaded. 156. The adjustable radiation treatment block mounting tray as in claim 153 wherein said releasable fastener is a screw, a thumb screw, a knurled head screw, a knob screw, an adjustable diameter pin, a cam clamp, or a bolt. 157. The adjustable radiation treatment block mounting tray as in claim 153 further comprising at least one spring attachment fitting affixed to said top face of said upper frame body member, at least one spring attachment fitting affixed to said upper face of said plate, and a spring, said spring connecting a spring attachment fitting affixed to said top face of said upper frame body member to a spring attachment fitting affixed to said upper face of said plate. 158. The adjustable radiation treatment block mounting tray as in claim 157 wherein said spring attachment fitting is a screw, a bolt, or a rod. 159. The adjustable radiation treatment block mounting tray as in claim 153 wherein said plate has one or more notch positioned on at least one outer edge of said plate, said notch positioned to align over a spring attachment fitting affixed to said frame body. 160. The adjustable radiation treatment block mounting tray as in claim 153 wherein said frame body or said plate or optionally both said frame body and said plate has at least one measuring gauge positioned thereon to allow the extent of movement of the plate relative to the frame to be observably measured. 161. The adjustable radiation treatment block mounting tray as in claim 153 further comprising a plurality of rail mounting bores in the upper frame body or lower frame body members and optionally in both upper and lower frame body members for receiving a fastener therein, at least one rail positioned on said upper frame body member or lower frame body member and optionally on both upper and lower frame body members, each rail extending beyond an outer edge of said upper or lower frame body member to adapt a dimension of said frame body so as to fit within a radiation treatment machine, each rail having a plurality of rail mounting holes for receiving a fastener there through, each rail being affixed to said upper or lower frame by at least one fastener that extends through a rail mounting hole and into a rail mounting bore in said upper or lower frame body member. 162. The adjustable radiation treatment block mounting tray as in claim 161 wherein said fastener is a releasable fastener to releasably affix said rail on said upper or lower frame body members. 163. The adjustable radiation treatment block mounting tray as in claim 161 wherein said rail has one or more identifying mark or color that correlate said rail to a particular manufacturer or model number of a radiation machine. 164. The adjustable radiation treatment block mounting tray as in claim 153 wherein said frame body has a slotted orifice positioned in at least one side frame body member, said slotted orifice forming a handle portion in said side frame body member, said handle portion optionally having at least one hole present therein for mounting one or more handle fitting thereto. 165. The adjustable radiation treatment block mounting tray as in claim 153 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 166. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, and at least one bore for receiving a releasable fastener therein;(b) a plate having an upper face and a lower face, said bottom face of said frame body being positioned on said upper face of said plate, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body;(c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, wherein a diameter of said orifice is larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body. 167. The adjustable radiation treatment block mounting tray as in claim 166 wherein said plate has at least one mounting hole and at least one mounting slot. 168. The adjustable radiation treatment block mounting tray as in claim 166 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 169. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, a generally central opening and least one bore for receiving a releasable fastener therein;(b) a plate having an upper face and a lower face, said bottom face of said frame body being positioned on said upper face of said plate, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body;(c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body. 170. The adjustable radiation treatment block mounting tray as in claim 169 wherein said plate has at least one mounting hole and at least one mounting slot. 171. The adjustable radiation treatment block mounting tray as in claim 169 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 172. An adjustable radiation treatment block mounting tray comprising:(a) a plate having an upper face and a lower face, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having a plurality of bores for receiving a releasable fastener therein;(b) a substantially rigid frame body having a top face and a bottom face, said bottom face of said frame body being positioned on said upper face of said plate, said frame body having an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one orifice extending through said frame body from said top face to said bottom face, at least one orifice being positioned over at least one bore in said plate;(c) at least one releasable fastener to releasably secure said frame body to said plate, said fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said frame body and inserted into a bore in said plate, a diameter of said orifice being larger than a diameter of said shank portion to allow said frame body to move relative to said plate when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said frame body to said plate. 173. The adjustable radiation treatment block mounting tray as in claim 172 wherein said plate has at least one mounting hole and at least one mounting slot. 174. The adjustable radiation treatment block mounting tray as in claim 172 wherein at least one bore in said plate is threaded. 175. The adjustable radiation treatment block mounting tray as in claim 172 wherein said releasable fastener is a screw, a thumb screw, a knurled head screw, a knob screw, an adjustable diameter pin, a cam clamp, or a bolt. 176. The adjustable radiation treatment block mounting tray as in claim 172 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 177. An adjustable radiation treatment block mounting tray comprising:(a) a plate having an upper face and a lower face, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having a plurality of bores for receiving a releasable fastener therein;(b) a substantially rigid frame body having a top face and a bottom face, said bottom face of said frame body being positioned on said upper face of said plate, said frame body having an upper frame body member, a lower frame body member, opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one orifice extending through said frame body from said top face to said bottom face, at least one orifice being positioned such that said orifice is aligned over at least one bore in said plate;(c) at least one releasable fastener to releasably secure said frame body to said plate, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said frame body to said plate. 178. The adjustable radiation treatment block mounting tray as in claim 177 wherein said plate has at least one mounting hole and at least one mounting slot. 179. The adjustable radiation treatment block mounting tray as in claim 177 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 180. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having a plurality of threaded bores for receiving a threaded rod therein;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one threaded bore in said frame body;(c) at least one rod having opposing end portions, both of said end portions of said rod being threaded, one end portion of said rod being inserted into a threaded bore in said frame body, an opposite exposed end portion of said rod being positioned through an orifice in said plate, a diameter of said rod being less than a diameter of said orifice in said plate, a threaded nut being attached to said exposed end portion of said rod, a diameter of said nut being greater than a diameter of said orifice such that when said nut is in a fastened position said nut compressibly secures said plate to said frame body and when said nut is in a released position allowing said plate to move relative to said frame body. 181. The adjustable radiation treatment block mounting tray as in claim 180 wherein said plate has at least one mounting hole and at least one mounting slot. 182. The adjustable radiation treatment block mounting tray as in claim 180 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 183. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having a plurality of threaded bores for receiving a threaded rod therein;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one threaded bore in said frame body;(c) at least one rod having opposing end portions, both of said end portions of said rod being threaded, one end portion of said rod being inserted into a threaded bore in said frame body, an opposite exposed end portion of said rod being positioned through an orifice in said plate, a diameter of said rod being less than a diameter of an orifice in said plate, a washer being positioned over said exposed end portion of said rod and positioned on said upper face of said plate, a diameter of said washer being greater than a diameter of said orifice, a nut being attached to said exposed end portion of said rod, such that when said nut is in a fastened position said nut and washer compressibly secure said plate to said frame body and when said nut is in a released position allowing said plate to move relative to said frame body. 184. The adjustable radiation treatment block mounting tray as in claim 183 wherein said plate has at least one mounting hole and at least one mounting slot. 185. The adjustable radiation treatment block mounting tray as in claim 183 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 186. An adjustable radiation treatment block mounting tray comprising:(a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one tray adjustment slot extending through said frame body from said top face to said bottom face;(b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one tray adjustment slot extending through said plate from said upper face to said lower face, at least one tray adjustment slot in said plate being generally perpendicular to a tray adjustment slot in said frame body and being positioned to overlap a tray adjustment slot in said frame body;(c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end, said shank portion of each releasable fastener positioned through both a tray adjustment slot in said plate and a tray adjustment slot in said frame body wherein when said releasable fastener is in a fastened position said releasable fastener compressibly secures said plate to said frame body and when said releasable fastener is in a released position said releasable fastener allows said plate to move relative to said frame body. 187. The adjustable radiation treatment block mounting tray as in claim 186 wherein said plate has at least one mounting hole and at least one mounting slot. 188. The adjustable radiation treatment block mounting tray as in claim 186 wherein said releasable fastener is a bolt and nut, a screw and nut or a cam clamp and nut. 189. The adjustable radiation treatment block mounting tray as in claim 188 wherein said nut is a T-nut, a wing nut, a lock nut, a finger nut, a knurled nut, a handle nut, or a push nut. 190. The adjustable radiation treatment block mounting tray as in claim 188 wherein said screw is a thumb screw, a knurled head screw or a knob screw. 191. The adjustable radiation treatment block mounting tray as in claim 186 wherein said plate has a radiation treatment block alignment line marked or scribed on said upper face of said plate, said radiation treatment block alignment line positioned such that a ridge protruding from a side surface of a radiation treatment block is aligned over said radiation treatment block alignment line when said radiation treatment block is affixed to said upper face of said plate. 192. A method for adjusting a radiation treatment block in a radiation beam comprising:(a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable treatment block mounting tray comprising:a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening;a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate;means to releasably secure said plate to said frame body, said means allowing said plate to move relative to said frame body when said means is in a released position and when said means is in a fastened position said means compressibly securing said plate to said frame body;(b) adjusting said means to a released position so that said plate and said radiation treatment block affixed thereto can move relative to said frame body;(c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient;(d) adjusting said means to a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. 193. The method as in claim 192 wherein said plate has at least one mounting hole and at least one mounting slot. 194. The method as in claim 192 wherein said means to releasably secure said plate to said frame body is a clamp. 195. A method for adjusting a radiation treatment block in a radiation beam comprising:(a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable radiation treatment block mounting tray comprising:a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one bore for receiving a releasable fastener therein;a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one bore in said frame body;at least one releasable fastener to releasably secure said plate to said frame body, at least one releasable fastener having a head portion at one end, a shank portion at an opposite end, said shank portion of said each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body;(b) adjusting each releasable fastener to a released position so that said plate and said radiation treatment block affixed thereto can move relative to said frame body;(c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient;(d) adjusting at least one releasable fastener until said releasable fastener is in a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. 196. The method as in claim 195 wherein said plate has at least one mounting hole and at least one mounting slot. 197. A method for adjusting a radiation treatment block in a radiation treatment beam comprising:(a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable radiation treatment block mounting tray comprising:a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one bore for receiving a releasable fastener therein;a plate having an upper face and a lower face, said lower face being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one bore in said frame body;at least one releasable fastener to releasably secure said plate to said frame body, at least one releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body;(b) adjusting each releasable fastener to a released position so that said plate and radiation treatment block can move relative to said frame body;(c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient;(d) adjusting at least one releasable fastener until said fastener is in a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. 198. The method as in claim 197 wherein said plate has at least one mounting hole and at least one mounting slot.
	summary
	claims	1. A Method for producing a part made of ceramic material matrix and ceramic material fibres composite material, the method comprising the following successive steps:formation of a fibrous preform by intertwining threads constituted of ceramic material fibres on a contact surface of a support element reproducing the internal and/or external shape of the part to be produced;partial densification of the fibrous preform at a temperature below the melting temperature of the material of the support element and below the melting temperature of the material of the fibres of the preform, said partial densification resulting in a consolidated fibrous preform comprising a matrix volume fraction above 5% and at the most equal to 40% of the matrix volume of the part to be produced;removal of the support element from the consolidated fibrous preform by chemical attack of the contact surface of the material of the support element;densification of the consolidated preform, carried out at a temperature below the melting temperature of the fibres of said preform. 2. The method according to claim 1, wherein the fibrous preform consolidated at the partial densification step comprises a matrix volume fraction at the most equal to 30% of the matrix volume of the part to be produced. 3. The method according to claim 2, wherein the fibrous preform consolidated at the partial densification step comprises a matrix volume fraction at the most equal to 20% of the matrix volume of the part to be produced. 4. The method according to claim 3, wherein the fibrous preform consolidated at the partial densification step comprises a matrix volume fraction at the most equal to 10% of the matrix volume of the part to be produced. 5. The method according to claim 1, wherein the support element is made of silica, preferably made of silica glass. 6. The method according to claim 5, wherein the chemical attack of the support element is obtained using an acid, preferably hydrofluoric acid, or a base. 7. The method according to claim 1, wherein the support element is made of alumina. 8. The method according to claim 1, wherein the support element is made of zirconium oxide. 9. The method according to claim 1, wherein the support element comprises a core that is made of a metal able to withstand the densification temperature of the preform and which is covered with a layer of silica, silica glass, alumina or zirconium oxide. 10. The method according to claim 9, wherein the chemical attack of the support element is obtained by carrying out the chemical attack of the layer of silica, silica glass, alumina or zirconium oxide present on the core using an acid, preferably hydrofluoric acid, or a base. 11. The method according to claim 1, wherein the support element is a hollow element. 12. The method according to claim 1, wherein the support element has an axis of revolution or is of flat shape. 13. The method according to claim 1, wherein the fibres are made of a material selected from carbon and silicon carbide. 14. The method according to claim 1, wherein the matrix is made of a material selected from carbon and silicon carbide. 15. The method according to claim 1, wherein the part made of composite material is a composite material cladding for a gas cooled or sodium cooled fast reactor or for a pressurised water reactor. 16. The method according to claim 1, wherein the part made of composite material is a hexagonal composite material tube for a gas cooled or sodium cooled fast reactor or for a pressurised water reactor.
043022871	summary	BACKGROUND OF THE INVENTION The present invention relates to a method for operating a nuclear reactor to increase nuclear reactor power and especially a method for increasing nuclear reactor power without danger of failure of the fuel rods disposed in a core of a nuclear reactor. A core of a nuclear reactor is provided with a plurality of fuel rods where each fuel rod is assembled such that a plurality of fuel pellets are packed in a clad tube. A rapid increase of nuclear reactor power causes pellet-clad-mechanical-interaction in a recognized linear heat generating rate range (indicated as PCI in the following description) between the fuel pellets and the clad tube due to volume expansion of the fuel pellets and causing excessive strain in the clad tube. Thus, there is a possibility of a failure of the fuel rod, which means that one or more than one openings, cracks or pin holes appear on the clad tube so that nuclear fission products are relieved into a surrounding coolant from the fuel rod through the openings, cracks or pin holes. Regarding the failure of the fuel rod, it has been proposed, as described in Japanese Published Patent Application No. 50-143,999, and U.S. Pat. No. 4,057,466 to Thompson et al, to restrain the rate of increase of the linear heat generating rate when the linear heat generating rate is increased above the linear heat generating rate at which the PCI begins. As disclosed in the Thompson et al patent, in order to properly condition the fuel rods so as to avoid PCI failure, the rate of increase of the fuel power or linear heat generating rate within the pellet-cladding interaction range is maintained below a critical rate of increase. The critical rate of increase necessarily requires a long term of at least several days to attain the desired operating power level for the nuclear reactor and the length of time to attain such level cannot be shortened due to the limitation on the rate of increase. SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a method for operating a nuclear reactor which overcomes the disadvantages of the prior art by increasing the power to attain the rated power level within a short period of time while also preventing failure of the fuel rods. In accordance with the present invention, there is provided a method for controlling the operation of a nuclear reactor to increase the reactor power in a range in which pellet-clad-mechanical-interaction occurs comprising the steps of increasing the reactor power from a power level in which pellet-clad-mechanical-interaction begins to take place up to a predetermined power level for the nuclear reactor and controlling the rate of increase of reactor power to a rate no less than 0.15 KW/ft/hr., and no greater than a predetermined critical rate so as to shorten the time necessary to raise the reactor power to the predetermined power level without causing pellet-clad-mechanical-interaction damage of the fuel elements.
	summary
	description	The present invention relates to the field of design of computer systems and data storage systems. More particularly, the present invention relates to the field of techniques and user interfaces for the design and configuration of computer systems and data storage systems. A computer system including a data storage system may be designed and configured for a specific application. This generally requires that a skilled designer rely on experience while making design choices based on requirements for the storage system and on possible memory devices to be incorporated into the storage system. Particularly, a variety of different memory devices form the building blocks of modern data storage systems. Specific devices can be based on, for example, optical, magnetic and/or electronic storage technologies and may include solid-state memory devices, magnetic tape drives and optical or magnetic disk drives and arrays. Memory devices can be further characterized, for example, by capacity, levels or types of redundancy provided (e.g., RAID-1 or RAID-5), bandwidth, cost, latency (e.g., read latency and/or write latency), and whether they are read and write capable, read-only capable, dynamic, static, volatile or non-volatile. Additionally, storage capacity and other resources of the data storage system may be assigned to one or more applications that are to be served by the data storage system. For example, various data elements, such as files or databases, may be placed in a storage system in a number of different ways. One form of this may be referred to as the “bin-packing problem,” the goal of which is to fit data elements of various different sizes into storage devices of given sizes, while minimizing wasted space. The assignment task quickly becomes more complicated, however, when one attempts to apply additional constraints. For example, certain applications may have minimum requirements in terms of storage capacity, access times and so forth. Since storage system resources are most often limited, the design process typically includes making a number of trade-offs with respect to the system resources. Further, design trade-offs that are appropriate in one context may not be appropriate in other contexts. For example, in a storage system for serving Internet downloads, high bandwidth and fault tolerance may be priorities, whereas, in a storage system for archiving data records, low cost and low power consumption may be priorities. However, the effects of some trade-offs may not be readily apparent, particularly where a single storage system serves multiple different applications. For example, when storage system resources are allocated to one application, the effect this will have on other applications served by the storage system may not always be readily apparent, even to a skilled designer. Modeling tools are known for predicting the performance of data storage systems. However, the capabilities of such modeling tools are limited. For example, they do not provide a solution when predicted performance falls short of requirements. Because specialized skills are required to design and configure a storage system, including assigning storage system resources to applications and verifying that the design meets requirements, such specially-designed storage systems tend to be expensive. Further, due to lack of a systematic approach, the design process can be time consuming and may yield a less-than-optimal result. Accordingly, it would be desirable to provide a technique for the design and configuration of a data storage system that is more systematic, more likely to yield optimal results and that is less time-consuming than conventional design techniques. The present invention is a technique and user interface for the design and configuration of computer systems and, particularly, for the assignment of data storage system resources. The invention allows a user to make design selections and, then, automatically provides an indication to the user of the effect of the selections. For example, various performance parameters for each of several applications served by a storage system may be displayed graphically as a chart. In response to the user adjusting a parameter for one application, the invention determines what effect this change will have on the other displayed parameters. The effects may then be displayed graphically in the chart. The invention is particularly useful for allocating data storage system resources among several different applications. In one aspect of the invention, a method of and an apparatus for assigning resources for a computer system design are provided. Desired levels of specified performance parameters for a computer system design are received from a user via a user interface to a computer system. The design is developed. Levels of performance parameters for the design are predicted. The predicted levels of performance parameters are compared to the desired levels of performance parameters. When the predicted levels are lower than the desired levels, the design is modified by the computer system. The computer system design may include a design for data storage system. Developing the computer system design may include assigning system resources to applications to be served by the design. A design tool operating on a computer system may perform the assigning. The design may be modified by reducing the desired levels of performance parameters. The reductions to the desired performance parameters may be based on utility functions which may be received via the user interface to the computer system. The user interface may be a graphical user interface. For example, the user may manipulate heights of bar graphs shown on a display of the computer system to specify the desired levels. Each bar graph may include indicia of the corresponding desired level of the performance parameter and indicia of the corresponding predicted level of the performance parameter. For example, different colors may be used to indicate the level of each. Predicting the performance of the design and comparing its predicted performance may be repeated after the design is modified. In addition, the user may be notified when the predicted levels are lower than the desired levels after the design is modified. The invention provides an easy-to-use technique for assigning resources in a data storage system based on desired levels of performance and on utility information provided by the user. The present invention provides a technique and user interface for the design and configuration of computer systems and, particularly, for the assignment of data storage system resources. A user, such as a system designer or administrator, is typically provided with a set of applications (e.g., software applications) that require resources of a computer system and, particularly, its data storage system resources. Thus, a single computer (or storage system) may serve one or more applications. Each application will generally have requirements, such as those relating to bandwidth, request rates, response times, and so forth. The resources of the computer system and, particularly, data storage system resources, such as disks, cache memory, parity groups, back-end bus traffic, and so forth, are to be assigned to the applications in an attempt to meet the requirements of each application. The invention provides an interface, such as via a computer system monitor, mouse and keyboard, through which the user may receive certain information regarding the design for the computer system, its configuration and its predicted performance. The term “performance” is used herein in its ordinary sense and includes parameters that tend to characterize the system, such as its size, weight, power consumption, availability, cost, bandwidth, latency, and so forth. Information may be provided to the user in numeric or graphic form and may be displayed on the computer monitor. As an example of a numeric display, a table or spreadsheet that includes various data storage system parameters that may be displayed to the user. As an example of a graphic display, a chart or graph may displayed which represents the various parameters. In addition, the user may provide input which affects the design, configuration and performance of the computer system under design. The input may be provided by the user via the mouse and/or keyboard of the computer system. FIG. 1 illustrates an exemplary graphic display 100 in accordance with the present invention. As shown in FIG. 1, parameters of three applications (Application #1, Application #2 and Application #3) are represented as vertical bars 102-118 where the height of a bar indicates the value of the corresponding parameter. The parameters shown in FIG. 1 include bandwidth, response time and capacity; however, it will be apparent that other parameters may be selected. As shown in FIG. 1, vertical bar 102 may represent the amount of bandwidth allocated to Application #1; vertical bar 104 may represent the response time for read or write requests initiated by Application #1 and vertical bar 106 may represent the amount of storage capacity allocated to Application #1. Similarly, vertical bars 108-112 may represent parameters for Application #2, while vertical bars 114 may represent parameters for Application #3. As explained herein, the displayed levels may be desired levels and/or predicted levels. It will be apparent that the arrangement of the display 100 of FIG. 1 is exemplary and that other arrangements may be selected. For example, other parameters, such as request rate or throughput may be displayed. As another example, parameters for the applications may be represented by one or more pie charts or tables. Preferably, the displayed parameters represent measures of performance that are relevant to the applications served by the computer system or data storage system under design. As mentioned, the user may also provide input via the display 100. In one embodiment, the user may position a cursor over a selected one of the vertical bars 102-118, depress control key, such as a mouse button, and then lengthen or shorten the bar by moving the cursor (this technique may be referred to as “clicking and dragging”). Alternate input may also be accepted, such as by the user typing desired numeric values for selected parameters. Accordingly, the invention provides an interface that is easy-to-use in that it readily displays relevant information and easily accepts input from the user. The parameters shown on the display 100 relate to applications to be served by a computer or data storage system that may be under design. Thus, in response to a user changing the displayed parameters, the design may be altered to accommodate the change. For example, the storage system design may only have a specified total amount of capacity. Accordingly, if the user changes the capacity parameter for Application #1, this may affect the storage capacity available to Applications #2 and #3. A design tool may be employed to make modifications to the design. The altered design may then be evaluated to determine whether it still meets the requirements of the applications served by the storage system. The user may then be informed of the results (e.g., whether the change is met with success or failure). For example, if the user increases the capacity parameter for Application #1 and this increase results in a reduction of the capacity available to Applications #2 and #3 such that their capacity requirements may still be met using a modified design, the display 100 may be updated to reflect new capacity parameters for Applications #2 and #3. Alternately, if this increase would not leave sufficient capacity for either Application #2 or #3, then a message may appear on the display 100 to inform the user of this. For example, the message: “insufficient resources available” may appear. Further, the parameters for which the application requirements could not be met may change color on the display 100. In addition, how much of the requirement that could not be met may be represented by using two colors: one showing the amount of a parameter available to an application and the other showing a difference between the amount of the parameter available and the minimum requirement for the application. In one embodiment, if a desired change to a parameter for an application is met with failure, the requirements for the other applications may be modified in order to accommodate the user's desired changes. However, to accomplish this, certain trade-offs may have to be made to the performance goals for the applications. One approach is to reduce the corresponding delivered performance parameter for all the other applications evenly (e.g., by the same percentage or amount). For example, assume that the user desires to increase the capacity of Application #1, which requires freeing up three Gigabytes. Assume also that Application #2 has a requirement of ten Gigabytes and that Application #3 has a requirement of twenty Gigabytes. Under these circumstances, one option is to reduce the requirement of Application #2 by one Gigabyte (i.e. 10% of ten Gigabytes) and to reduce the requirement of Application #3 by two Gigabytes (i.e. 10% of twenty Gigabytes). Another option is to reduce the capacity requirement for each of Applications #2 and #3 by the same amount (one and one-half Gigabytes). Another approach is to reduce only the requirement for the application whose requirement is highest. For example, assume that the user desires to increase the capacity of Application #1 by three Gigabytes. Assume also that Application #2 has a requirement of ten Gigabytes and that Application #3 has a requirement of twenty Gigabytes. Under these circumstances, one option is to reduce the requirement of Application #3 by the entire three Gigabytes since Application #3 has the highest requirement. This approach will tend to reduce the requirements of the other applications to the same level. Thus, if the capacity requirement for Application #3 is reduced to ten Gigabits, then any further reductions may be shared equally by Applications #2 and #3. When confronted with a failed attempt, the user may be provided the ability to select from one of these schemes for trading-off the levels of performance parameters. Alternately, one approach may be pre-selected and, thus, may be performed without further input from the user. Still another approach is to obtain input from the user regarding the relative importance of the requirements or goals for each application. For example, the user may specify certain “utility functions” for each parameter. A utility function represents how much utility (or value) is attached to various levels of the performance parameters. FIGS. 2A-C illustrate exemplary utility functions in accordance with the present invention. As shown in FIGS. 2A-C, each utility function may be represented as a function in two-dimensions with a performance parameter (e.g., bandwidth) on the X-axis and a corresponding delivered utility on the Y-axis. More particularly, FIG. 2A illustrates that the user has determined that for a particular application and performance parameter, utility is proportional to bandwidth. In other words, the faster this application operates, the greater the utility. Thus, FIG. 2A illustrates a linear relationship between the performance parameter and its utility. FIG. 2B illustrates a situation in which the user has determined that the faster the application operates, the greater the utility except that once the bandwidth reaches a certain point, additional bandwidth is less useful. Thus, FIG. 2B illustrates a linear relationship between the performance parameter and its utility, except that the slope is reduced after a certain level of the parameter is reached. An example suitable for this function may be an order entry system. This is because an ability to handle normal ordering traffic is very important. It would also be helpful, but not as important, to also have an ability to handle peak loads. FIG. 2C illustrates a situation in which there is no utility below a certain bandwidth, but that once that level is reached, a certain level of utility is achieved. This first level of utility is shown in FIG. 2C by vertical portion of the curve. Then, as bandwidth increases, so does utility. This is shown by the sloping portion of the curve. When a certain point is reached, utility no longer increases. This is shown by the horizontal portion of the curve. An example suitable for this function may be a video server. This is because the lowest bandwidth may be necessary for minimal image quality. As the bandwidth goes up, so does image quality. However, a point is eventually reached where the storage system is no longer the limiting factor on image quality. It will be apparent that the utility functions illustrated in FIGS. 2A-C are exemplary and that other functions may be selected. Further, utility functions may be multi-dimensional. For example, the utility of certain performance parameters, such as bandwidth and response time, may be interdependent. As explained herein, by specifying utility functions, desirable trade-offs can be made when resources are limited, without requiring further input from the user. More particularly, given user-specified relationships between utility and levels of certain performance parameters, appropriate trade-offs can be made so as to maximize the utility provided while allocating limited resources. FIG. 3 illustrates a block schematic diagram of a general-purpose computer system 300 by which the present invention may be implemented. The computer system 300 may include a general-purpose processor 302, a memory 304, such as persistent memory (e.g., a hard disk for program memory) and transitory memory (e.g., RAM), a communication bus 306, and input/output devices 308, such as a keyboard, monitor and mouse. The computer system 300 is conventional. As such, it will be apparent that the system 300 may include more or fewer elements than shown in FIG. 3 and that other elements may be substituted for those illustrated in FIG. 3. Software for implementing the present invention, such as assigning data storage system resources in accordance with the present invention and for providing the user interface of the present invention, may be stored in the memory 304 in accordance with the present invention. Further, the display 100 of FIG. 1 may be provided by the monitor 308 of the system 300. FIG. 4 illustrates a flow diagram 400 of a process for assigning resources for a computer system design in accordance with the present invention. As mentioned, a software program which implements the process of FIG. 4 may be stored in the memory 304 of the computer system 300 of FIG. 3 for causing the processor 302 to perform the steps of the process. Accordingly, the process is preferably performed automatically, such as by the computer system 300, however, it will be apparent that one or more of the steps may be performed manually. Referring to FIG. 4, program flow begins in a start state 402. From the state 402, program flow moves to a state 404. In the state 404, the user may specify a scheme for trading-off system resources should the need arise. For example, utility functions, such as those illustrated in FIGS. 2A-C, may be captured and stored for later use (e.g., in the memory 304 of FIG. 3). Thus, the user may specify the utility functions for various performance parameters of each application to be served by the computer or data storage system under design. Alternately, the user may select from a number of pre-configured utility functions. For example, the utility functions illustrated in FIGS. 2A-C may be displayed on the display 100 (FIG. 1) along with a menu of applications and performance parameters. Then, the user may select appropriate ones by “clicking” on them. From the state 404, program flow moves to a state 406 in which application goals may be captured and/or modified. In addition to the utility functions, the desired levels of performance parameters may be stored in the memory 304 of the computer 300. For example, the user may specify desired measures of performance for each application by making selections from a menu shown on the display 100 (FIG. 1). As shown in FIG. 1, the selections may include bandwidth, response time, capacity and so forth. In the state 406, the user may also set desired levels for each selection. For example, the user may click and drag the bars 102-118 (FIG. 1) to the desired levels. From the state 406, program flow moves to a state 408. In the state 408, a determination may be made as to whether to modify the design of the system based on the utility functions set in the state 404 and/or the performance levels set in the state 406. In one embodiment, this determination is made by the user; if no affirmative input from the user is provided, then the default condition is a negative determination. In which case, program flow moves to a state 410. In the state 410, a determination may be made as to whether to finalize the current design of the computer or storage system. In one embodiment, this determination is made by the user; if no affirmative input from the user is provided, then the default condition is a negative determination. In which case, program flow returns to the state 404. Accordingly, program flow remains in a loop which includes the states 404, 406, 408 and 410 until the user decides to either modify the design or finalize the current design. While in the loop, the user may make as many changes to the utility functions (in state 404) or to the performance levels (in state 406) as desired. Once the user decides to modify the design, program flow moves from the state 408 to a state 412. In the state 412, a design tool may be invoked to develop a design for the computer or its storage system based on the desired performance levels. Any suitable conventional design tool may be used for this purpose, such as a computer-aided design tool. In a preferred embodiment, the design tool is similar to the one disclosed in co-pending U.S. patent application Ser. No. 09/924,735, of Eric Anderson, filed on Aug. 7, 2001, and entitled “SIMULTANEOUS ARRAY CONFIGURATION AND STORE ASSIGNMENT FOR A DATA STORAGE SYSTEM,” the contents of which are hereby incorporated by reference. Further, manual design techniques may be employed in the state 412, such that the system is designed completely or partially “by hand.” From the state 412, program flow moves to a state 414 in which a performance modeling tool may be invoked in order to characterize the design developed in the state 412. The tool invoked in the state 414 preferably provides a prediction of the actual levels of performance that may be achieved by the design developed in the state 412. For example, if one of the performance goals specified in the state 406 is bandwidth, then the tool invoked in the state 414 preferably provides a predicted level of bandwidth for the design developed in the state 412. The tool invoked in the state 412 may be any suitable conventional modeling tool. In a preferred embodiment, the modeling tool is similar to the one disclosed in co-pending U.S. patent application Ser. No. 09/843,903, filed Apr. 30, 2001, of Mustafa Uysal et al., and entitled “Method and Apparatus for Morphological Modeling of Complex Systems to Predict Performance,” the contents of which are hereby incorporated by reference. Further, manual modeling techniques may be employed in the state 414, such that the system is modeled completely or partially “by hand.” Also, actual performance of a data storage system may be measured in the state 406. From the state 414, program flow moves to a state 416. In the state 416, a comparison may be made between the desired levels of the performance parameters set in the state 406 and the levels achieved in the state 414. From the state 416 program flow moves to a state 418 where a determination may be made as to the results of the comparison performed in the state 416. If the desired levels were not achieved, then program flow may move to a state 420. In the state 420, the performance levels set in the state 406 may be adjusted based on the utility functions set in the state 404. Thus, where resources of the storage system are limited, trade-offs can be made in the state 420. For example, assuming the total available storage capacity of the storage system under design is exceeded by the amount of capacity the user desires to provide to each application, a trade-off will have to be made. If the utility function for one of the applications is flat (horizontal) beyond a certain capacity level (e.g., similar to the curve in FIG. 2C), this means that the capacity allocated to that application can be reduced to that level in the state 420 with no loss of utility. As another example, if all the applications have the same utility function for capacity as shown in FIG. 2A (and with the same slope), then the capacity for each may be reduced by the same amount in the state 420. Numerous other trade-offs relative to the limited resource can be made in the state 420. From the state 420, program flow may return to the state 412. Then, the newly adjusted performance levels (in state 420) may be used to develop a new design for the computer or storage system (in state 422) and newly achieved performance results compared to the desired performance levels 416. This program loop (including states 420, 412, 414, 416 and 418) may continue until the desired levels are achieved. Thus, if in the state 420, it is determined that the desired performance levels (as set in the state 404 (or modified in the state 420), are met, then program flow may move from the state 420 to a state 422. In the state 422, the current performance levels that can be achieved (as predicted in state 416) may be shown on the display 100 (FIG. 1). From the state 422, program flow returns to the first loop (including states 402, 404, 406, 408 and 410) where the user may make further adjustments to the utility functions (404) and the desired performance levels (state 406). Note that when program flow is in the loop that includes states 420, 412, 414, 416 and 418, with each pass through the loop beyond two or three passes, it is becomes increasingly less likely that the desired performance goals can be met without making more drastic trade-offs. Thus, rather than making such drastic tradeoffs in the state 420, program flow may return to the first loop (including states 402, 404, 406, 408 and 410) where the user may make these trade-offs manually by changing the utility functions and/or the desired performance levels. Under these circumstances, the levels displayed in the state 422 may show how much of a requirement that could not be met such as by using two colors, as explained above in reference to FIG. 1. When a satisfactory design is achieved and the user no longer wishes to make any additional changes, the user may indicate that the process is complete. For example, the user may click on an icon on the display 100 labeled “done.” Then, program flow moves from the state 410 to a state 424. In the state 424, the design may be completed. For example, a physical data storage system may be configured as indicated by the design tool invoked in the state 412. From the state 424, program flow may terminate in a state 426. While the foregoing has been with reference to particular embodiments of the invention, it will be appreciated by those skilled in the art that changes in these embodiments may be made without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims.
	description	The invention relates to a molten salt fission reactor. In particular, the invention relates to a pool type reactor with a molten salt core. Molten salt nuclear reactors are based on a critical mass of a fissile material dissolved in a molten salt. This is commonly referred to as fuel salt. They were pioneered at the Oak Ridge National Laboratory in the 1950's to 1970's but have never been successfully commercialised. They have several potential advantages over other reactor types which include the ability to breed fissile 233U from thorium, production of much lower levels of transuranic actinide waste than uranium/plutonium reactors, operation at high temperatures, avoidance of accumulation of volatile radioactive fission products in solid fuel rods and much higher burn up of fissile material than is possible in conventional reactors. Two major factors have prevented the commercialisation of such reactors. Many designs of molten salt reactors require attached reprocessing plants to remove fission products continually from the fuel salt. This is necessary since fission products act as neutron poisons, especially in moderated reactors based on a thermal neutron spectrum. It is also necessary to remove insoluble fission products which would otherwise foul pumps and heat exchangers. Such reprocessing plant is complex, expensive and requires extensive development work. Secondly, molten salts are highly corrosive. While nickel based superalloys are more resistant to such corrosion than standard steels, over long time periods corrosion would still occur. Thus design and manufacture of essential components such as pumps and heat exchangers represents a major development challenge. In principle, new composite materials based on carbon and/or silicon carbide have the chemical resistance to withstand the molten salt but building complex structures such as pumps and efficient heat exchangers from such materials remains very challenging. Recently, Mattieu and Lecarpentier (Nuclear Science and Engineering: 161, 78-89 (2009)) showed that a non-moderated molten salt reactor could run for a decade or more without reprocessing. Their design still however involved pumps and heat exchangers and could only be built after major research and development of materials for such components. A critical factor in any molten salt fuelled reactor is extraction of the heat produced by nuclear fission from the fuel salt. Many ways have been proposed to achieve this, a particularly good summary is provided by Taube (1978) (EIR Bericht no 332, Fast reactors using molten chloride salts as fuel). The methods described are Pumping a molten coolant such as lead, mercury or a volatile salt into the fuel salt so that the coolant both mixes and extracts heat from the fuel salt Pumping the fuel salt through an external heat exchanger Pumping a second molten salt or other coolant through pipes passing through the fuel salt with the fuel salt being forcibly pumped in a circulation pattern around the coolant pipes All of these proposed designs, other than the first, require pumping of the molten salt in some way. The first design, direct contact between the fuel salt and coolant, has been extensively investigated and is considered impractical for a number of reasons including entrapment of fuel salt in the coolant liquid. A further design of molten salt reactor was proposed by Romie and Kinyon (ORNL CF 58-2-46, 1958) where the molten fuel salt was allowed to circulate through a heat exchanger by natural convection. This design however allowed only low power output and required a high volume of fuel salt outside the critical area of the core. Large volumes of fuel salt outside the core result in most delayed neutrons being emitted outside the critical area of the core. The resulting low delayed neutron fraction in the critical area of the core renders it unstable and liable to undergo a rapid and uncontrollable increase in power level leading to explosive destruction of the reactor. A common feature of many conventional non molten salt reactor designs is to place the fuel material passively in tubes, around which coolant circulates, usually by pumping but sometimes just by natural convection. The fuel in the tubes can be a solid, as in the current generation of pressurised water reactors, a paste of solid material in molten sodium (GB 1,034,870), a metal (U.S. Pat. No. 3,251,745) or an aqueous solution (U.S. Pat. No. 3,085,966). Such an arrangement using molten salt fuel was considered by the Aircraft Reactor Experiment (The Aircraft Reactor Experiment-Design and Construction, E. S. Bettis et al, Nuclear Science and Engineering 2, 804, 1957). However, the researchers concluded that it would require fuel tubes with a very small diameter (of the order of 2 mm) in order to prevent overheating of the fuel salt due to the low thermal conductivity of the fuel salt. As a result, the project adopted a system of pumping the fuel salt rapidly through heat exchangers so that the resulting turbulent flow allowed effective heat transfer from the fuel salt to the walls of the much larger tubes. All molten salt reactor designs since then, including the Molten Salt Reactor Experiment which was actually built and operated (ORNL 5011 Molten Salt Reactor Program Semi-annual Progress Report August 1974) have used a similar pumped fuel salt arrangement. No effective proposal has been made to construct such a reactor with molten fuel salt in tubes where the fuel salt is not actively pumped through the tubes. In large part that is due to the belief that the low thermal conductivity of molten salts would not permit sufficiently rapid heat transfer from the salt to the wall of the tube without the forced turbulent mixing that pumping permits. As discussed above, the elimination of pumps for the fuel salt would greatly reduce the materials challenge in building a practical molten salt reactor. According to one aspect of the present invention, there is provided a nuclear fission reactor comprising a core, a pool of coolant liquid, and a heat exchanger for extracting heat from the coolant liquid. The core comprises an array of hollow fuel tubes, each containing molten salt of at least one fissile isotope. The fuel tube array is at least partly immersed in the pool of coolant liquid. The fuel tube array comprises a critical region, where the density of the fissile isotopes during operation of the reactor is sufficient to cause a self-sustaining fission reaction. Heat transfer from the molten salt in each fuel tube to the exterior of that tube is achieved by any one or more of natural convection of the molten salt, mechanical stirring of the molten salt, oscillating fuel salt flow within the fuel tube, and boiling of the molten salt within the fuel tube. The molten salt of fissile isotopes are contained entirely within the tubes during operation of the reactor. Thus the heat can be transferred from the interior to the exterior of unpumped fuel tubes without relying solely on the thermal conductivity of the molten salt, and this in turn allows the provision of tubes of a useful diameter. In particular, the tube diameter can be chosen to be sufficiently large to optimise natural convection within the tube. According to a further aspect of the present invention, there is provided a nuclear fission reactor comprising a core, a pool of coolant liquid, and a heat exchanger. The core comprises an array of hollow tubes which contain molten salts of fissile isotopes. The tube array is at least partly immersed in the pool of coolant liquid. The tube array comprises a critical region, where the density of the fissile isotopes during operation of the reactor is sufficient to cause a self-sustaining fission reaction. The coolant liquid contains a sufficient proportion of a neutron absorbing material to substantially shield a containing tank of the liquid from neutrons emitted by the core, and the coolant liquid contains a fertile isotope such that the reactor acts as a breeder reactor. Said neutron absorbing material is optionally a fertile isotope such as 232Th or 238U such that the reactor acts as a breeder reactor. According to a further aspect of the present invention, there is provided a nuclear fission reactor comprising a core, a pool of coolant liquid, and a heat exchanger. The core comprises an array of hollow tubes which contain molten salts of fissile isotopes. The tube array is at least partly immersed in the pool of coolant liquid. The tube array comprises a critical region, where the density of the fissile isotopes during operation of the reactor is sufficient to cause a self-sustaining fission reaction. The coolant liquid is a molten metal salt contained within a single tank, and the circulation of the coolant liquid is driven by natural convection only. According to a further aspect of the present invention, there is provided a nuclear fission reactor comprising a core, a pool of coolant liquid, and a heat exchanger. The core comprises an array of hollow tubes which contain molten salts of fissile isotopes. The tube array is at least partly immersed in the pool of coolant liquid containing one or more fertile isotopes. The tube array comprises a critical region, where the density of the fissile isotopes during operation of the reactor is sufficient to cause a self-sustaining fission reaction. The reactor further comprises a layer of molten metal in contact with the coolant liquid, the molten metal being such that the bred fissile isotope is soluble in the molten metal, and the reactor comprising a system for extracting the molten metal. According to a further aspect of the present invention, there is provided a method of operating a nuclear fission reactor. The reactor comprises a core, a pool of coolant liquid and a heat exchanger, where the core comprises an array of hollow fuel tubes, each containing the molten salt of one or more fissile isotopes, the fuel tube array is at least partly immersed in the pool of coolant liquid and comprising a critical region, where the density of the fissile isotopes during operation of the reactor is sufficient to cause a self-sustaining fission reaction. The method comprised containing the molten salt entirely within the fuel tubes and transferring heat from the molten salt in each fuel tube to the exterior of that tube and thus to the coolant using one or more of: natural convection of the molten salt, mechanical stirring of the molten salt, oscillating molten salt flow within the fuel tube, boiling of the molten salt within the fuel tube. Heat is extracted from the coolant using the heat exchanger. Further aspects and preferred features are set out in claim 2 et seq. The Convection Cooled Nuclear Core A reactor may be constructed from a nuclear core using an array of fuel tubes immersed in a pool of molten coolant as shown in FIG. 1. FIG. 1 shows a reactor 100 comprising a tank of coolant 101, a core made up of an array of fuel tubes 102, and a heat exchanger (e.g. steam tubes) 103. The coolant can be a wide variety of liquids including water, molten metals, and molten salts. The tubes may be of any suitable shape, but in one embodiment they have a design whereby they have a large diameter region 201 at the bottom and a narrow region 202 towards the top (see FIG. 2). The result is that the lower portion of the array achieves critical mass while the upper portion remains subcritical. The tubes 102 may be filled with molten fuel salt containing fissile isotopes up to the top of the narrow region 202, or they may be filled only within all or part of the wide region 201. If the narrow region 202 is filled, then this prevents neutrons from escaping by passing up through the empty space within the fuel tube. If the narrow region is not filled with salt, then the narrow region may be formed into a spiral, helix or other non-linear form to prevent neutrons passing directly up the tube and out of the reactor. The tubes are arranged in an array which can be of any dimension and shape although a cylindrical array has certain advantages. The design output power of the reactor can be adjusted by varying the number of fuel tubes in the array. Heat can be removed from the tube array by convective flow of the coolant (e.g. blanket salt). The narrow upper part 202 of the tubes allows for lateral flow of the heated blanket salt out of the tube array with less restriction than would be the case with fuel tubes of uniform diameter. Furthermore, the subcritical region increases the distance between the critical region of the core and the top of the tank, allowing for more effective neutron shielding. Heat is removed from the blanket salt through a heat exchanger 103 such as an array of boiler tubes immersed in the blanket salt, around the periphery of the reactor. The coolant for the heat exchanger could be, for example, water/steam, which may be passed directly to turbines, a gas, which is passed directly to a closed Brayton cycle turbine, or a molten metal or metal salt which is passed to a steam generator to generate steam for use in turbines. Alternatively, the hot blanket salt can be pumped out of the reactor for use in other heat dependent processes and then returned to the reactor tank, Neither the fuel salt nor the blanket salt requires pumps. This advantage removes what is perhaps the major technical hurdle that has held back molten salt reactor development. However, acceleration of the natural convective flow of the blanket through the array of fuel tubes by turbines or other pumping systems may be desirable in order to increase the power output from the reactor. The natural convective flow can also be increased by increasing the depth of the tank. In order to achieve an adequate convection rate within the blanket salt, there needs to be a substantial temperature difference between the fuel salt and the blanket salt. This comprises the major trade off implicit in this reactor design—simplicity and cheapness vs. reduced thermodynamic efficiency. However, since fuel costs of nuclear reactors are essentially trivial, reduction of the cost of construction is far more important to the economics of the reactor than is the thermodynamic efficiency—indeed thermodynamic efficiency only really matters at all in such reactors to the extent that it spreads the capital cost over more kW of capacity. Heat transfer from the fuel salts to the tube wall may be achieved by thermal conduction and convection, without pumping of the salts themselves. The convection may be assisted in various ways, further described below. The dimensions of the fuel tubes are selected to enable rapid natural convection of the fuel salt at the operating temperature. This improves flow of the salt from the centre of the tube to the periphery, allowing the tubes to be cooled by natural convection and conduction alone. In general, tubes of smaller diameter will allow more rapid cooling of the fuel salt. However, this does not apply when the tube diameter becomes sufficiently small as to inhibit convection of the fluid. For a molten salt with a density of 4837−1.9537T kg/m3, a specific heat of 418+0.136T J/kg·K, a viscosity of 0.0259−0.00198T kg/sec·m where T is the temperature in kelvin and a thermal conductivity of 0.81 w/m·K, convection does not occur for tube diameters below 5 mm. Other molten salts are likely to have minimum convective diameters of a similar order, so tubes with a diameter of at least 5 mm should be used. Another factor limiting the diameter of the fuel tubes is the thickness of the tube walls, and the effect on criticality and neutronics of the reactor. In a non-moderated fast neutron reactor criticality is largely dependent on achieving a certain average concentration of fissile isotopes within the core region. The space between tubes cannot be arbitrarily reduced as tube diameter is reduced since gaps of less than 5 mm result in a rapidly increasing resistance to coolant flow. Nor can the wall thickness be arbitrarily reduced in proportion to tube diameter, since very thin walls would be easily perforated. For a tube of external diameter d (mm), a wall thickness of 0.5 mm and minimum distance between tubes of 5 mm, the fraction of total core volume occupied by fuel salt decreases from 70% for a 46 mm tube diameter (d) to 10% for a 4 mm tube diameter. Thus a reactor core comprising 4 mm tube would need a fuel salt containing seven times higher concentration of fissile material, which may well be unobtainable. Furthermore, all materials absorb neutrons to some extent. The greater the quantity of wall material within the reactor core, the higher this parasitic neutron loss. Higher parasitic losses mean that still higher concentrations of fissile material are required to achieve a critical mass. Small tube diameters result in a higher concentration of tube wall material within the core region. Thus smaller diameter fuel tubes result again in a higher concentration of fissile isotopes being needed. The fuel tubes can incorporate fins on their outer surface in order to increase the area available for heat transfer to the coolant. Corrugation or ridging of the fuel tube wall similarly improves heat transfer to the coolant salt. The shape of the fins, corrugation, or ridging may be chosen to increase the heat transfer within the fuel salt due to convection. Convective mixing of the fuel salt within the wide region of the fuel tube can allow realistic levels of heat transfer from the fuel salt. Temperature differences between the fuel salt in contact with the fuel tube wall and that at the centre of the fuel tube could be 500° C. or more without risking boiling of the fuel salt, which would correspond to a density difference of about 25% for many salt compositions which would enable significant convection. Molten salts with greater thermal expansion may be chosen to allow for more rapid convection. Similarly, molten salts with low viscosity can be chosen in order to enable more rapid convection. Heat transfer could also be improved by rifling the inner wall of the fuel tube or adding baffles to deflect convective flow from the vertical to the horizontal direction. The ratio of length to diameter of the fuel tube, roughness and/or structure of the inner wall may affect the effectiveness of heat transfer and can all be optimised for any particular reactor configuration by standard methods of computational fluid dynamics. FIG. 3 shows the results of computational fluid dynamics calculations carried out on a smooth walled round tube of varying diameter. The molten salt had a density of 4837−1.9537T kg/m3, a specific heat of 418+0.136T J/kg·K, a viscosity of 0.0259−0.00198T kg/sec·m where T is the temperature in kelvin and a thermal conductivity of 0.81 w/m·K. Two simulations are given for different levels of heat generation in the fuel salt. A further simulation is given for a similar notional molten salt with a coefficient of thermal expansion of zero which shows the maximum temperature in the absence of convective cooling. This shows the extraordinary effect of convection on heat transfer within the fuel salt and also demonstrates that for any particular geometry, fuel salt composition and power level, there is a range of diameters of the tubes where changes in diameter or in power level have relatively little effect on the maximum temperature reached by the molten salt. Tube diameters in that range have advantages that are significant in certain embodiments of the invention. FIG. 4 shows a fuel tube according to one embodiment, where the fuel tube contains baffles 400, perforated at the centre, which divide the fuel tube into segments 401 in order to improve the convection of the fuel salt, e.g. segments 401 with height substantially the same as, or at least of a similar order to, the diameter of the fuel tube. Convection within the segment carries heat more efficiently to the wall of the fuel tube while the perforation aids filling and emptying of the fuel tube and allows mixing of the fuel salt between different segments. The fuel tubes may be arranged such that the critical region of the tubes is approximately horizontal. A slight slope may be required in order to allow off-gassing of fission products. Arranging the fuel tube horizontally reduces the vertical size of the convection cells, reducing the time taken for fuel salt at the centre of the tube to reach the edge. An example fuel tube according to this embodiment is shown in FIG. 5. The fuel tube may be formed into a shallow helix 501 with a circular 502 or oval 503 cross section. Because the tube is slightly sloped, any evolved gasses will rise to the top of the helix, and material may be added from the top of the tube as with the straight fuel tubes. The reactor design also permits limited boiling of the fuel salt in the hot centre of the fuel tube to drive convection and create mixing. In this option, it would be desirable for the fuel salt to fill only the lower part of the fuel tube leaving a helically constructed upper part of the fuel tube to act as a condenser for any vapour escaping from the fuel salt. This configuration of the reactor would permit use of a fuel salt melting at a relatively high temperature provided that the vapour produced from that fuel salt melted at a lower temperature than the working temperature of the coolant so that it condensed as a liquid which would run back into the fuel salt. Inclusion of up to about 40% of zirconium halide in the fuel salt is one of several effective ways to achieve this. Heat transfer from the fuel salt to the wall of the fuel tube can also be increased by use of the oscillatory baffled column system. There are many possible configurations of such columns. The baffles may be designed such that the motion of the baffles is not impaired by the deposition of fission products, e.g. by ensuring adequate separation of moving surfaces which are immersed in the fuel salt. FIG. 6 shows an embodiment of an oscillatory baffled column where a series of baffles 601 is inserted into the fuel tube, optionally in the form of a helix or a series of perforated plates 602, with the baffles being mechanically driven up and down in a vertical direction, e.g. by a mechanical actuator 603. The eddy mixing created by the movement of the baffles increases heat transfer from the fuel salt to the fuel tube wall. Another embodiment of oscillatory baffled column is to form the fuel tube into a U shaped tube 701 with both ends of the tube anchored in the lid of the reactor tank as shown in FIG. 7. Oscillating gas pressure 700 is applied to one or both ends of the U shaped tube 701 to create an oscillating motion of the fuel salt within the tube. In one embodiment, the frequency of oscillation of the fuel salt is matched to the resonant frequency of its oscillation so as to achieve maximum movement with minimum applied gas pressure. The efficiency with which the oscillating motion of the fuel salt is converted to greater heat transfer to the fuel tube wall can be increased by including baffles of varying shapes in the fuel tube, by corrugating the wall of the fuel tube or by other methods. In contrast to conventional pumped fuel tubes, the oscillation allows the fuel salt to be kept within the core, and does not require it to be passed through a pump or external heat exchanger. It will be appreciated that the use of U shaped fuel tubes without oscillating flow and with baffles being optional is also possible. Such tubes have the advantage of simpler manufacture as closure of the end is not required. If the tubes have narrower sections where they are attached to the lid of the reactor, those narrower sections can be intertwined in a helical manner to prevent neutron passage up the tube. A narrower region at the bottom where the tube bends back on itself is also advantageous as it can increase strength and reduce the resistance to flow of coolant into the bottom of the fuel tube array. Corrugation of the external fuel tube wall also enhances transfer of heat from the fuel salt to the fuel tube wall as shown in FIG. 8. The neutron flux across any reactor core is inevitably higher at the centre of the critical region than it is at the edges. A particular advantage of this reactor design is that the effect of this uneven neutron flux on fission rates and hence heat production can be mitigated in a number of ways. For example, the spacing of the fuel tubes can be wider at the centre of the array than at the periphery, as shown in plan view in FIG. 12. Tubes at the periphery can also contain fuel salt with a higher concentration of fissile and/or fertile isotopes. In one embodiment the fuel tubes form a cylindrical array with a diameter similar to the height of the wide region of the fuel tube, with tubes spaced more widely at the centre of the array with, optionally, an empty zone 1201 at the centre of the array so that the array forms an annulus. In another embodiment the spacing of fuel tubes is uniform but selected tubes towards the centre of the array are left empty of fissile material. The neutron economy of the reactor and the uniformity of neutron flux across the core region can also be improved by placing a neutron reflector around the array of fuel tubes so that neutrons lost from the core region may be reflected back into it. The neutron reflector can conveniently be combined in a structure that constrains flow of the coolant to a circuit including the heat exchanger and the fuel tube array. The same structure can support turbines to accelerate the natural convective flow of the coolant and can be arranged so as to be easily replaced by lifting it out of the reactor tank as a single unit or a set of segments forming a complete ring around the fuel tube array. The reactor as described above is a fast neutron reactor with only limited moderation of the neutrons by the relatively heavy nuclei of the fuel and coolant salts. Epithermal and thermal configurations of the reactor are also possible through incorporating moderating material such as graphite into the reactor core. This can be achieved for example as shown in FIG. 13 by replacing some fuel tubes 1301 with graphite tubes 1302 or building a solid graphite core perforated by channels somewhat wider than the fuel tube diameter into which the fuel tubes are inserted so that a gap is left between the fuel tube wall and the graphite through which the coolant salt circulates. Construction Materials and Temperatures The below discussion of materials and temperatures is by way of example only, in order to illustrate the technical considerations in the selection of such materials. Any specific materials disclosed should not be taken as limiting the scope of the attached claims in any way. Choice of Molten Salts Most molten salt reactor designs utilise lithium salts due to their low melting points. In the reactor disclosed lithium is ideally avoided as it produces substantial 3H on neutron irradiation—even if purified 7Li is used. 3H in molten salts readily penetrates metals and would therefore contaminate the steam in the boiler tubes, with costly containment and engineering consequences. Avoiding lithium has other advantages. The cost of purified 7Li is unclear (but certain to be high) and facilities for the isotopic purification of lithium are subject to major regulatory constraints. An example of a suitable blanket salt would be a eutectic mixture of 10% NaF/48% KF/42% ZrF4 which has a melting point of 385° C. and would usefully operate across a temperature range of 450-900° C. Such a mixture has a relatively low viscosity, only slightly higher than water, which improves the convective flow of the blanket. There are many other options for coolant salts, including use of chloride salts that have lower melting points. Salts of fertile isotopes such as 238uranium or 232thorium can also be included in the coolant salt. One example among many others of a suitable fertile coolant salt would be a eutectic mixture of thorium tetrafluoride and sodium fluoride. The fuel salt must be capable of dissolving substantial amounts of salts of fissile material (e.g. uranium or plutonium). It must be usable at temperatures significantly higher than the coolant salt but if the fuel salt occupies the subcritical region of the fuel tubes, the fuel salt should have a melting point not substantially higher than the working temperature of the coolant salt, in order that the fuel salt does not freeze in the cooler parts of the fuel tube. If the fuel salt does not occupy the subcritical region of the fuel tubes then it should preferably release a vapour which condenses to a liquid rather than a solid at the working temperature of the coolant salt. More effective convection of the fuel salt in the fuel tube can be achieved if a fuel salt is selected that has a large coefficient of thermal expansion. The greater buoyancy achieved from heating of such liquids allows either wider diameter fuel tubes to be used or less use of devices such as corrugation, baffles, ridges, oscillating flow, internal helical baffles etc. to achieve adequate convection. NaCl forms liquids containing 30-35% UCl3/PuCl3 and 60-65% NaCl melting at from 450-520° C. as shown in FIG. 9 (temperatures in diagram in ° K). As such these allow for inclusion of a wide variety of uranium, plutonium and other actinide chlorides at quite high concentrations. It is also possible to use mixtures of UCl3 and PuCl3 with little or no added NaCl. Mixtures containing high UCl3 concentrations exhibit particularly high thermal expansion as shown in FIG. 10. The nuclear interactions of the salts must also be considered. The main interactions for 35Cl are the (n,p) producing 35S, the (n,a) producing 32P and the (n,γ) producing 36Cl. The first two have moderately low cross sections for fission neutrons (96 mb and 56 mb respectively) and produce short lived isotopes that do not present significant disposal problems. The (n,γ) reaction producing 36Cl has a very small cross section for fast neutrons (1 mb) but the product is long lived and would require safe disposal or reuse of chloride salt at the end of its useful life. Use of chloride salt isotopically enriched with 37Cl is an option whereby the chloride salt can be improved for use in the reactor with less neutron absorption and less long lived radioactive waste production. Fluoride salts are substantially more favourable neutronically than chloride salts. Mixtures of UF4/NaF/KF with up to 30% UF4 have melting points around 550° C. which would make them suitable for fuels comprising natural uranium enriched in 235 uranium or 233 uranium bred from thorium Use of fluoride salts of plutonium or mixed transuranics from spent fuel is more challenging however. Plutonium is only stable as the trifluoride and mixtures of this with NaF are liquid only above about 800° C. Even allowing for modest melting point depression by adding KF and UF4 to the mixture this would make freezing of the salt in the narrow part of the fuel tube likely. Inclusion of low concentrations of plutonium in a fluoride salt mixture is possible but achieving critical mass using only plutonium as the fissile isotope would be challenging. A minor modification to the fuel tube design would however make use of such high melting salt mixtures practical. If the tube was only partially filled with fuel salt, filling only most of the wide part, then convective mixing of, and continual fission heat production in, the fuel salt would be expected to prevent freezing of the fuel salt. In this arrangement, it would be desirable to adjust the composition of the fuel salt so that any vapour produced would condense to a liquid, rather than a solid, in the upper part of the tube. This could be conveniently achieved by including approximately 20% ZrF4 in the fuel salt though many other options exist including incorporation of low concentrations of chloride salts Fission may cause a net release of halogen from the fissile fuel salts, with the fission products only neutralising part of the released halogen. Left alone, the accumulated halogen will attack most fuel tube materials and will result in the volatilisation of other halogen fission products such as iodine. Two principle ways can be used to neutralise the excess halogen. First is to use as fuel salt the trichlorides or trifluorides of the fissile and fertile isotopes. Uranium trihalide will react with excess halide to produce uranium tetrahalide which is compatible with most fuel tube materials. Second is to include small amounts of metal of intermediate reactivity with halogens (intermediate between the actinides and the fuel tube material) in the fuel tube or salt which will react with excess halogen while not being so reactive as to reduce the fissile or fertile halides to their metallic form. Suitable metals include niobium, titanium and nickel which could be incorporated as solid particles in the fuel salt or as plating on the inside wall of the fuel tube or as constituents of baffle structures inserted in the fuel tubes. Fuel Tube Material The fuel tube represents the major materials challenge for the reactor. It must be resistant to corrosion by both fuel and blanket salts and must tolerate the high neutron flux existing in the core. The material does not however have to survive for the life of the reactor. Fuel tubes are readily removed and replaced and would probably need to be replaced at least every 20 years for reprocessing of the fuel. The materials challenge is therefore substantially less severe than would be the case for a permanent reactor component. There are a number of advanced materials such as metal composites and SiCf/SiC composites that might have excellent properties for fuel tubes but all these are technologically immature. Use of such materials would slow down the development process for the reactor, but may be suitable for future implementations. Two mature technologies that could be considered are Cf/C composites and refractory metals, for example nickel or molybdenum, and their alloys. Cf/C composites have excellent chemical resistance to molten salts, though at very high temperatures UCl3 can react with carbon to produce carbides. They are however subject to severe loss of strength at high neutron doses and would therefore need replacing regularly—perhaps every 2-4 years. The cost of this programmed replacement may however be compensated for by the superior neutron transparency of carbon compared to other fuel tube options. Carbon based fuel tubes are especially attractive where fertile isotopes are included in the coolant salt since they allow for less parasitic capture of neutrons by the fuel tube material and hence superior breeding of fissile isotopes. In such a reactor it is likely that shorter fuel tube life would be acceptable as more frequent reprocessing of the fuel salt would also be desirable. When considering metals for the fuel tubes two factors dominate the choice—resistance corrosion and physical strength at high temperatures. It is useful to consider the physical strength requirements in a little detail as the requirements are far less stringent than normally considered for structural use of a metal. One of the characteristics of the fuel tubes is that they experience minimal mechanical stress. The tubes hang from clamp fittings in the reactor lid with most of weight of the tube supported by the blanket salt, which also effectively insulates it from shocks. Lateral flow of the blanket salt at the thin region of the tubes is not expected to exceed 1 m/s which would exert only low lateral force on the tubes. What lateral force the moving blanket salt did apply would largely result in a bending moment where the tube is anchored to the reactor lid. At that location the metal is cooler and protected from neutron flux, which improves its physical strength and longevity considerably. Finally, the tubes do not have to support any pressure differences and the outer surface of the tubes will be cooled to below about 700° C. by the blanket salt, thereby minimising overall heat softening of the metal. These very modest physical requirements may make alloy selection relatively non challenging. There is a substantial literature on both nickel and molybdenum alloys but the minimal strength requirements of the fuel tubes might even make use of the pure metals practical. The choice of metal may be dictated by the maximum fuel salt temperature to which they could be exposed. Detailed calculations of thermal and fluid flows within the fuel salt are required to determine what those maximum temperatures are likely to be. Molybdenum alloys may be usable up to 1500° C. which is well above any expected fuel salt temperatures. Control of corrosion is important. The chemistry of the blanket salt would be essentially constant and could readily be adjusted to the optimum redox state to maximise the alloy life. A simple way to do this would be to include samples of zirconium metal in the coolant salt which would reduce any oxidising species introduced, and in particular would trap any oxygen from water or air that dissolved in the coolant salt in the form of insoluble zirconium oxide. The relatively low temperature of the blanket salt would also make corrosion control straightforward. Control of corrosion from the fuel salt is rather more complex. Fission results in the creation of a complex mix of elements ranging in redox potential from caesium to iodine. Halogen released from fissioned actinide halides may or may not be fully neutralised by reactive metal fission products. Detailed material evolution calculations are required to establish the nature of the chemical corrosion challenge and if there is a need for systems, such as the inclusion of moderately reactive sacrificial metals in the fuel mix, to manage that challenge. Use of trichlorides or trifluorides of uranium in the fuel salt would also provide a large capacity to absorb any net release of halogen in the form of tetrahalides. Boiler Tubes The boiler tubes are exposed to maximum temperatures in the region of 600-700° C. Since the steam temperature within them would be about 350° C. and they would be somewhat protected from the full temperature of the blanket salt by a boundary layer of cooler salt, that is comfortably within the capabilities of existing nickel alloys. Such alloys are already used for boiler tubes within coal fired power stations where they are exposed to far more aggressive conditions (including a complex mix of molten salts condensed from the fireball). Nonetheless, the boiler tubes are likely to have a shorter life than the reactor—if only from the effects of “steam side” corrosion. They can however be made in modular format allowing relatively easy replacement. Reactor Tank The reactor tank is one of the few permanent components of the reactor since both fuel tubes and boiler tubes are replaceable on a lift out/drop in basis. There may be a primary containment vessel above the tank filled with inert gas and containing mechanisms for off gas collection/pumping and fuel tube/boiler tube replacement. By way of example, a steel tank lined with graphite or carbon composite would have the necessary physical and chemical resistance for the reactor tank. Its lifetime would ultimately be determined by its exposure to neutron flux which embrittles the steel and eventually disintegrates the carbon. Protection from neutron flux is therefore most desirable and this is considered below. Provided neutron protection was adequate, a reactor life of a century is a realistic prospect. Neutron Flux Neutrons escaping from the core region represent a significant screening challenge. If allowed to reach the boiler tubes they could cause embrittlement which would be a serious issue for high pressure tubes. If they reached the reactor tank wall, similar embrittlement of the steel and swelling of the carbon lining would limit its effective life. Building neutron absorbing shielding into the reactor is one option for dealing with the excess neutrons but would increase the complexity of the design. Another potentially attractive option is to include a “non-burnable” neutron absorber in the blanket salt. Hafnium is a classic non burnable poison as most of its isotopes transmute into other stable neutron absorbing isotopes on absorbing neutrons. Hafnium is also a major contaminant in zirconium ores and has almost identical chemical properties. Preparing hafnium free zirconium is difficult and expensive which is why reactor grade zirconium is about ten times more expensive than “normal” zirconium metal. In one embodiment, such a neutron absorber would have a low neutron absorption for fast neutrons, thereby not reducing the neutron economy in the fuel tube array where the neutron spectrum is fast, but which has significant absorption of slower neutrons so that it effectively absorbs neutrons escaping the fuel tube array before they reach the permanent structures of the reactor. This therefore opens up the opportunity to simultaneously save substantial cost and provide effective neutron screening by simply using cheap, hafnium contaminated, zirconium tetrafluoride in the blanket salt. The optimum level of hafnium in the blanket salt would need to be calculated based on neutron scattering, moderation and absorption in the blanket salt. There will be a trade-off in the level to be used since blanket salt passes through the core region and the presence of a neutron absorber in the blanket salt would reduce the core neutron economy (albeit only marginally) and therefore somewhat increase the initial fissile inventory. Control Systems Conventional reactors use control rods to offset the initial excess reactivity of their fuel rods. Continuous monitoring of fission rate through neutron detectors inside and outside the core is necessary to control local transients which can lead to overheating. The reactor disclosed herein requires no such control systems. The fuel tube array contains just sufficient fissile fuel to be critical at its design temperature in the reactor. As the fuel heats it expands with a coefficient which may vary from approximately 3×10−4 up to 2×10−3. A 100° C. temperature increase thus decreases the concentration of fissile material within the core region by 3-20% which is more than sufficient to quench the chain reaction. If fuel salts such as UCl3 are used, the thermal expansion coefficient approaches the upper end of the range given, giving the reactor yet greater stability. The basic physics of the reactor therefore maintains the temperature of the fuel at an almost fixed average temperature irrespective of the rate at which heat is transferred from the fuel to the blanket. The reactor power level is hence effectively controlled by the rate of heat withdrawal through the boiler tubes in the blanket salt. If heat withdrawal ceased then the fuel would heat and expand until the rate of fissions fell to a level just sufficient to maintain the new, higher, fuel temperature against any remaining heat loss from the reactor. The primary reactor monitoring system may be a set of temperature sensors, e.g. as schematically shown in FIG. 14, spectral temperature sensors, built into the tube cap assemblies 1402. These would monitor the temperature of the fuel salt in each fuel tube 1401. As fissile material was consumed and fission products accumulated in the fuel tubes, the temperature of the fuel salt in the tubes would fall, the salt would contract, fissile isotope concentration would rise and the chain reaction would continue. Another option for the temperature sensor is to measure the expansion of the fuel salt. This can be done in several ways but a simple one is to measure the resonant acoustic frequency of the gas column in the tube between the tube cap and the surface of the fuel salt. This method would be particularly useful where the upper portion of the fuel tube was non-linear. A number of neutron absorbing or moderating control rods may be included in the design to allow a lower temperature shut down of the reactor in emergency, at decommissioning and when replacing the fuel tube array. The use of neutron moderating rather than absorbing control rod material is made possible by the presence of strong absorbers of slower neutrons, such as hafnium, in the blanket salt, though a control rod structured with a moderating core surrounded by a periphery of strong neutron absorber might be preferable Alternatively, control rods could be entirely dispensed with. In an emergency a large quantity of a strong fast neutron absorber could be added to the coolant salt. One example would be europium fluoride. In order to quench the chain reaction during refuelling or decommissioning, half of the fuel tubes could be partially raised from the tank, leaving the fuel filled portion immersed in the coolant salt. The increased volume of the region of the reactor containing fuel salt would result in its becoming subcritical. An important aspect of control systems is their operation during reactor start up. It is normal to hold a reactor subcritical with control rods until fuelling is complete and then to very slowly withdraw the control rods. Too rapid a withdrawal can trigger a prompt critical event which can be disastrous. A similar system could be used in the Simple MSR with one or more control rods that were completely withdrawn at the conclusion of the start up sequence. However, it would be possible to dispense with control rods at start up by adding fuel tubes progressively to the core until criticality is reached, then continuing to add more fuel tubes until the design fuel salt temperature is reached. It is vital to avoid prompt critical events during this process due to too rapid insertion of reactivity into the reactor core. The potential for prompt criticality can be reduced by one of more of the following steps. A neutron source can be incorporated into the core so that the core rapidly generates heat when it reaches a delayed critical state instead of having a potentially long lag time while the neutron flux builds up. This can be conveniently done by incorporating higher actinides such as 244Cm from spent nuclear fuel into the fuel salt. A fuel composition with a delayed high neutron fraction can be used. This would entail use of 235U rather than just 239Pu and/or incorporation of 238U in the fuel, which has a particularly high delayed neutron fraction when fissioned by fast neutrons. The fuel tubes can be added at startup first as a central, subcritical central core set and then as a peripheral set building up from the outside of the core inwards. That would ensure that when the final fuel tube needed to create criticality was added it was some distance away from the main central fuel tube group so the reactivity insertion was quite small and therefore safe. The gap between the inner and outer group of fuel tubes would then be filled with fuel tubes causing the core to achieve its design fuel salt temperature when the annulus was filled. An alternative start up procedure would be to preheat the coolant salt to a relatively high temperature and then build up the array of fuel tubes. The high temperature would expand the fuel salt rendering the core subcritical. When the core was assembled, the coolant salt could be slowly cooled allowing the core to approach criticality in a slow and controlled way. Fuel Choice and Refuelling/Reprocessing System It is a characteristic of most molten salt reactors that they have great fuel flexibility. This reactor is no exception and could be fuelled with, for example, plutonium, enriched uranium or mixed transuranic actinides from waste conventional reactor fuel. Top up of the fissile material in each tube as fissile material was consumed during reactor operation would be practical though it would represent a relatively mechanically complex system in the reactor. A safe, easily monitored and audited fuel handling system would be to have fuel pellets (simply frozen molten salts) loaded into a radiation screened cartridge system at a central secure processing plant. The cartridge would be mounted at the reactor into a mechanism that would track over the array of fuel tube caps, lock onto the relevant one and discharge single fuel pellets into that fuel tube. The fuel salt may, by way of example, contain approximately 30-35% total actinide chlorides, of which most may be fertile 238U. Consumption of the fissile isotopes during reactor operation would tend to reduce the power output resulting in the fuel salt cooling and contracting, thereby maintaining its critical mass. Production of new fissile isotopes from fertile isotopes in the fuel salt could maintain the levels of fissile isotopes and thereby the reactor power output. If such “breeding” was insufficient to maintain the power output then the fuel tubes could be topped up by adding small amounts of fresh fissile material to each tube through its cap assembly. An alternative to this option would be to add fresh fuel tubes in addition to those already in the reactor either at the centre of the array in the annular space or around the periphery of the array. Where the core has been designed with tubes lacking fissile material towards the centre of the tube array, those tubes could be replaced with tubes containing fissile material as the reactor burns its initial fissile load. In general, but particularly where the fuel salt is chosen to have a large coefficient of thermal expansion, substantial cooling of the average fuel salt temperature due to consumption of fissile material can be tolerated. The resulting large contraction of the volume of the fuel salt maintains criticality of the core with only acceptable net loss of power output. Examples of such fuel salt compositions are 85% UCl3/15% XCl3 where X represents mixed plutonium, americium, curium and trace higher actinides from reprocessed nuclear fuel. A further option for fuel salt is to use a mixture of low enriched uranium and plutonium trichlorides as the fissile fuel. Both 235U and 239Pu are consumed by fission but most bred fissile material is 239Pu which has a relatively greater contribution to reactor criticality than the 235U due to its higher fission cross section and higher fission neutron yield. The result is that a breeding ratio of less than 1.0 can nonetheless maintain the fuel salt with a critical concentration of fissile isotopes. Yet a further option to avoid the need to add fresh fissile material to the fuel tubes would be to incorporate a removable neutron absorber in the coolant salt which can be removed progressively as fissile material is consumed. One option would be cadmium fluoride which could be easily removed from the coolant salt by electrolytic reduction or reduction by addition of a reactive metal such as sodium. The resulting metallic cadmium would be molten at reactor temperatures and could either be removed or allowed to accumulate at the bottom of the tank. Still a further option would be to incorporate neutron absorbing control rods in the reactor core which could be gradually withdrawn as fissile material was consumed. In the event that the reactor operated as an “over breeder” producing more fissile material than it consumed and therefore causing power output to increase, the selective removal of individual fuel tubes could be used to bring the reactor back to its design power level. Accumulation of fission products can become the limiting factor dictating reprocessing intervals in molten salt reactors. Fast reactors like the one disclosed herein are relatively resistant to the problem of neutron poisoning by fission products but when fission products reach their solubility limit in the fuel salt they precipitate. That precipitation is a major problem for reactors which need to pump the salt through heat exchangers because it can lead to blockages, flow restrictions or accumulation of heat generating fission products in regions with inadequate cooling. Prevention of such precipitation can ultimately be the key factor determining the maximum possible reprocessing period. In the reactor disclosed herein however where fuel salt is not pumped or piped, precipitated material would have little effect whether it was carried dispersed in the fuel, plated out on the fuel tube wall or accumulated as a deposit at the bottom of the tube. In the case where the fuel salt is mechanically agitated, moving parts which are immersed in the fuel salt can be designed such that surfaces that move relative to each other do not approach closely enough that deposition is likely to be a problem over the lifetime of the reactor. Off Gas System Most designs of molten salt reactors have relatively complex off gas systems with helium sparging of the fuel, separation of foamed noble metals and filtration and processing of the evolved gasses. Particular attention has to be paid to tritium which is produced in quite large quantities from the lithium salt used, even if expensive 99.995% 7LiF is used. A very much simpler system can be used in the reactor disclosed herein. Because the neutron spectrum is fast, neutron poisoning by 135Xe is not a significant problem (the neutron cross section falls from 2,700,000 barns for thermal neutrons to 7600 barns for neutrons in the slowing down region and to virtually zero for fast neutrons). Rapid removal of Xenon is therefore not necessary either to improve neutron economy or to prevent reactivity excursions due to changes in power levels. Xenon and Krypton can therefore be allowed to build up to saturating concentrations (about 10−5 mol/l) in the molten fuel and then to spontaneously bubble out of the fuel salt. In an exemplary design, the rate of noble gas production at full power would saturate the fuel in 30 minutes. The resulting flow of noble gas from each fuel tube would be about 13 ml per day at NTP or about 50 ml/day at reactor temperature. A gas space above each fuel tube of about 500 ml would give an average residence time of evolved gas in the fuel tube of 10 days which would allow most highly radioactive isotopes to decay within the fuel tube. Other volatile fission species would be limited. Tritium would be produced only by rare ternary fission events but very small amounts would be carried from the fuel salt as HF by the evolved noble gasses. Volatile chlorides such as ZrCl4 would have low but not insignificant vapour pressures over the hot salt and small amounts may therefore be carried with the noble gas stream. Iodine might form mixed halides with UCl3 or react with a scavenging metal included in the fuel mix. Small amounts might however be carried with the noble off gas stream. Overall, an entirely passive off gas system would be adequate and would require only simple nickel alloy tubing leading to a condenser/absorber to collect the off gas products. Accelerating the off gas process with a helium flow would be unnecessary and in fact undesirable as it would result in evaporative loss of fuel salt over time with consequent deposition of radioactive material in the tubes of the off gas system. The off gas system can be conveniently combined with the system of oscillating gas pressure described hereinabove. Reactor Safety The basic physics and chemistry of the reactor design give it a very high level of intrinsic safety. Some of these factors are common to all molten salt systems The strong negative feedback due to thermal expansion of the fuel shuts down the chain reaction automatically in the event of overheating. Control rods are not needed (except possibly as a backup should it be necessary to shut down the reactor) as there is no excess reactivity in the reactor. The fuel and fission products are in physically and chemically stable forms which would react neither with water nor air to significant degrees in the event of containment failure. Volatile fission products are continuously removed for safe storage and decay so that volatile radioactivity resulting from any containment failure would be minimal. Some are common to most fast neutron reactors Xenon transients will not be significant during changes in power output since the reactor operates on a fast neutron spectrum and the concentration of xenon in the fuel will be constant at its saturating concentration under all load conditions. Some are common to “pool” type reactors Primary cooling of the core is by passive convection so that even a complete failure of the secondary coolant system would not result in rapid core overheating. The huge pool of molten blanket salt would be capable of absorbing residual decay heat from the core for many hours before auxiliary cooling would be needed, if indeed it ever was. Some are unique to this design The efficient neutron absorption by the blanket salt results in minimal exposure of reactor structures to neutron flux; hence the reactor structures do not become highly radioactive nor experience physical degradation. Any failure of a fuel tube, or indeed of all the fuel tubes simultaneously, would result in the molten fuel mixing with the large excess of neutron absorbing blanket salt. That would instantly quench the chain reaction while providing a large heat capacity to absorb decay heat from the fission products. All molten salts, at all times, are immersed in the large pool of blanket salt. Freezing of salt in a pipe or heat exchanger in the event of pump failure etc. is therefore not possible and a single heating system can be used to melt the salt at startup and keep it molten during down time. That single heating system represents a substantial simplification compared to other molten salt reactor designs. All fuel salt is located within the reactor so that loss of delayed neutrons that are emitted outside the core region is minimised. This substantially increases the reactor stability and resistance to “prompt critical” power excursions. One potential danger intrinsic to the design relates to the presence of the boiler tubes within the reactor tank. It would be essential to establish that rupture of one of those tubes would not result in a dangerous accident. Steam reacts rather slowly with ZrF4 at the temperature of the blanket, with a Gibbs free energy of about zero. The bulk of the steam would therefore discharge into the head space above the molten blanket salt with a small amount of HF and ZrF4 vapour included. A pressure release system, discharging into a suitable reservoir would therefore need to be included in the design of the reactor lid, together with automatic shutdown of water pumps in the event of pressure loss (a normal feature of boiler systems). Capital Costs of the Reactor Accurate capital cost estimates are of course far beyond the scope of this disclosure. However, the main cost differences from conventional nuclear reactors can be highlighted and suggest that the reactor would be substantially cheaper to build. The following major differences should be considered. Reduced containment due to the reactor's intrinsic safety Fuel fabrication costs cut to a fraction of solid fuel rods No high pressure radioactive system with pumps, plumbing etc. No thin channel high efficiency heat exchangers with associated costs Much simplified control systems with no need for multiple redundancy. No neutron detector network required. No rapid acting precision control rod system. A small number of simple SCRAM rods is sufficient for emergencies and reactor shut down. Potential for factory production of the nuclear island instead of on site construction. Nuclear Industry Infrastructure The new nuclear infrastructure needed for a fleet of reactors according to the present disclosure is relatively modest and should cost a small fraction of the cost of the current infrastructure. In the long term it would therefore be a sound investment if it made possible nuclear electricity production that was price competitive with fossil fuels. The infrastructure would also support a lucrative export market in reactors if the ambition of producing power at lower cost than fossil fuels could be realised. Fuel Production and Purification Fuel for the reactor is simply salts of the fissile isotopes. No manufacturing of fuel rods is involved and relatively low purity of the fissile material is acceptable. In the UK it would be reasonable to initially use the 100 tonne stock of plutonium dioxide currently accounted for as having zero net value. On the basis of figures for the MSFR design, the UK plutonium stock would be sufficient to fuel perhaps twenty 500MWe reactors. A plant capable of 10 tonne per year production would allow two reactors per year to be fuelled and would be of very modest size. In the longer term, actinide waste from existing stocks of uranium/plutonium oxide fuel could be used as feedstock. It may be economical to use existing reprocessing facilities for this, though the process could be substantially simplified as lower purity is acceptable, but electrolytic pyroprocessing would probably be cheaper and more efficient for new plant. Fuel Salt Reprocessing Reprocessing of fuel salt from the reactor would be infrequent, perhaps only after 10-20 years, although more frequent refuelling may be necessitated by the lifetime of the fuel tubes. Used fuel could in fact be stored in much the same way that current used fuel is stored but reprocessing to separate the remaining actinides from the fission products and used salt would be relatively straightforward since significant contamination of the recovered actinides with fission products is perfectly acceptable for reuse of the actinides. Breeding Configuration It is likely that the reactor will contain fertile isotopes in the fuel salt with the result that new fissile material is bred continually during operation. This happens in most nuclear reactors. The present reactor has the potential to be a more effective breeder of new fissile isotopes if fertile isotopes are also included in the coolant salt. The same basic reactor design can be configured as a breeder reactor, but with significant changes. The reactor would be more costly and would only make economic sense when the cost of fissile material rose significantly—as would inevitably occur if nuclear power substantially replaced fossil fuels for power generation. Choice of Salts The blanket salt would be an important breeding site in the reactor. Thorium would be an exemplary fertile material for a number of reasons. It is cheap, abundant and breeds to 233U which is advantageous as a fuel because it generates far less long lived actinide waste. Thorium has a very small fission cross section even in fast reactors which will ensure minimal contamination of the blanket salt with fission products. Depleted uranium could be used instead of thorium but greater care would be needed to remove fission products from the coolant salt since 238uranium has a larger cross section for fission by fast neutrons than thorium, An example salt mixture would be 22 mole % ThF4 in NaF which has a melting point of 620° C. That would necessitate having a fuel salt working temperature of about 900° C. and a similar NaF/actinide fluoride mixture would be possible as the fuel salt though a chloride based salt would still be practical and would have certain advantages as set out above. The thorium in the blanket would efficiently absorb the neutrons escaping the core, thereby providing the same screening effect as the hafnium in the non-breeding design. The large volume of the blanket salt would require much larger amounts of thorium than most current molten salt reactor designs. However, thorium is relatively abundant and currently represents a troublesome, mildly radioactive, waste product of rare earth mining. The cost of imported thorium to the USA in 2011 varied from $27 to $250 per kg depending on purity. Even at $250 per kg, 250 tonnes of thorium would cost only £40 million. Fuel Tube Material The high temperature of the fuel salt in the above example would make nickel alloys unsuitable for the fuel tubes. Molybdenum alloys, or even pure molybdenum might suffice. Alternatively, Cf/C composites could be used with the proviso that the fuel tubes were replaced and the fuel reprocessed on a 2-4 year cycle. That timing would be consistent both with preventing tube weakening due to neutron damage and maximising breeding efficiency by removal of fission products. In the longer term less well developed materials such as metal composites and silicon carbide composites could be superior options. Boiler Tubes Despite the higher blanket salt temperature, nickel alloys would probably still be suitable for the boiler tubes. The large temperature difference between the steam and the molten salt would likely result in a frozen shell of salt forming around the boiler tubes. That layer would protect the tube from corrosion. Recovery of Bred 233U Compared to most breeder reactor configurations, this reactor has a huge volume of blanket salt. That results in the 233Pa produced from the 232Th being diluted so much that its chance of undergoing neutron capture before it decays to 232U is tiny. Separation of the 233Pa is therefore not necessary. Rapid recovery of the 233U is however desirable so as to avoid it undergoing fission in the blanket and thereby contaminating the blanket with fission products. There are many ways to do this but an attractive option, as shown in FIG. 11, is to include a layer of molten bismuth/thorium alloy 1101 in the bottom of the tank. Reductive extraction into bismuth of uranium by thorium is well established as a method to recover uranium from molten salts. The uranium could be allowed to accumulate for many months, protected from the neutron flux by the thorium in the blanket salt, before being recovered. Separation of uranium from thorium fluorides by reductive extraction into molten bismuth has been well described (U.S. Pat. No. 3,577,225). Normally this is achieved by pumping the molten salt through tall columns of molten bismuth. In a reactor where the breeding takes place in a tank of molten salts, such as the reactor disclosed herein, it would only be necessary to include a layer of molten metal, such as bismuth, in the bottom of the tank with an excess of thorium metal incorporated or dispersed in the molten metal layer. Optionally, the layer of molten metal may be drawn from the bottom of the tank by a circulating system 1102, passed through a steam generator or other heat exchanger 1103, and reintroduced at the top of the tank as a spray or a number of liquid columns 1104, which fall through the coolant blanket absorbing heat. This arrangement therefore both acts as a heat exchanger, without the need for physical separation of the blanket salt and heat exchanger coolant, and improves the collection of the fissile material from the blanket. Uranium could then be recovered from the molten metal by pumping it from the reactor and fluorinating it so that the uranium volatilised as the hexafluoride. An alternative to this conventional procedure would be to circulate the molten metal either continually or periodically through a cooling system that cooled the metal to above its melting point. Both thorium and uranium dissolved in the metal would precipitate as bismuthides or the corresponding complex with the other metal which could then be removed and processed to recover the uranium. The advantage of this process is simplicity and the avoidance of transporting or processing large volumes of bismuth or other metal. Several exemplary reactor configurations will now be described to further exemplify the principles discussed above. A cylindrical reactor tank is constructed from 5 cm thick steel lined on the inner surface with 10 cm of graphite tiles. It is insulated on the external side and enclosed below ground level in a concrete and steel lined pit. The dimensions of the tank are 6 m diameter by 4 m deep. The tank is filled with a coolant salt mixture composed of 40% zirconium tetrafluoride 60% sodium fluoride. The zirconium contains between 1-2% hafnium. The salt is initially melted by insertion through the reactor lid of an electric heating system that is removed when the reactor is operational. Arrays of steam tubes are positioned in the form of 6 arrays of tubes around the internal perimeter of the reactor tank. Each array occupies 60 degrees of curvature of the tank and together they form a complete annulus of 1 m thickness. The steam tubes are formed from seamless nickel alloy tubing and are joined to feeder tubes above the tank so that no welds or joins are immersed in the molten salt. Water at approximately 300 C is pumped into the tubes and emerges as a mixture of steam and water at 350-400 C. Steam is separated in a steam drum and the steam fed back into another part of the steam tube array to superheat. The portion of the steam tube array used as superheater is positioned above that portion used to produce the water/steam mixture so that it is in contact with the highest temperature coolant salt. The superheated steam is piped to a convention steam turbine/generator set. Connections of the steam tube arrays with the steam turbines are remotely severable so that steam tube arrays can be remotely disconnected, removed from the tank, replaced with fresh arrays and reconnected to the turbine systems. Fuel tubes are formed from 99+% pure molybdenum with a wall thickness of 0.5 mm. They have a diameter of 4 cm in the lower 1.5 m of the tube and of 1.5 cm in the upper 1.5 m of the tube. The upper 1.5 m is formed into a spiral with outer diameter of 4 cm and a pitch of 40 cm. They are secured to the lid of the reactor using a clamp fitting that has an easily and remotely released connection to a 5 mm nickel alloy tube network which is connected to a cryogenic trap to condense and store any gasses evolved from the fuel salt. Fuel tubes are arranged in a hexagonal pattern with centre to centre spacing of 5 cm in a cylindrical array of diameter 3 m. The lower 2.8 m of the tubes are immersed in the coolant salt leaving a 20 cm gas space above the coolant salt which is filled with helium. 3 m×2 cm diameter rods of zirconium metal are passed through the reactor lid into the space between the fuel tubes and steam tubes to act as sacrificial scavengers of any reactive chemicals in the coolant salt. 80% of the fuel tubes are filled to a depth (at 1000 C) of 1.4 m with a mixture of uranium chloride enriched to 5% in the 235 isotope of uranium and a mixture of plutonium and higher actinide trichlorides recovered from uranium oxide fuel rods that had been used once in conventional light water moderated reactors. Of the uranium chloride, 95% is trichloride with 5% tetrachloride. The frozen salts are packed as granules into the tubes at a central manufacturing facility and inserted into the reactor when the coolant salt is heated to above the melting point of the fuel salts, thereby avoiding the possibility of the expansion of the salts through melting causing cracking of the fuel tubes. The concentration of uranium trichloride falls from 80% in fuel tubes at the centre of the array to 70% for tubes at the outer perimeter of the array with the remainder being the plutonium and higher actinide trichlorides. The remaining 20% of the fuel tubes are filled with the coolant salt mixture and are distributed within the array so that the proportion of coolant salt filled fuel tubes increases from zero at the outer edge of the array to 30% at the centre of the array. Each fuel tube clamp assembly contains a temperature sensor that operates by detecting the resonant frequency of the gas column above the molten fuel salt, expansion of the fuel salt resulting in a shortening of the gas column. Fuel tubes are loaded into the reactor progressively with the temperature being monitored as further tubes are added so that the completed array of fuel tubes reaches the design temperature. As the reactor operates and fissile material is consumed, coolant salt filled fuel tubes are replaced with fuel salt filled tubes so as to maintain the fuel salt at close to its design temperature. The region above tank consists of a helium filled chamber of similar diameter to the reactor tank and height of 5 m. It contains a remote operated crane apparatus that can remove fuel tubes or steam tube banks and an airlock assembly to allow movement of fuel tubes or steam tube banks in and out of the chamber. The helium is continually circulated through and absorption/filtration apparatus to maintain very low oxygen, nitrogen and humidity levels. Low pressure “burst valves” are incorporated into the reactor lid with piping to steel condenser units to allow any steam release within the reactor tank due to a burst steam tube to be vented and condensed rather than build up pressure within the reactor tank. The reactor is similar to that described in example 1 except as follows. It is particularly designed to be a net breeder of fissile material. The fuel tubes are manufactured from silicon carbide fibre/silicon carbide composite with a wall thickness of 1 mm and a 50 um coating of pyrolytic carbon on each surface. The lower portion has a diameter of 20 mm and the upper of 10 mm. They are arranged in a hexagonal array with centre to centre spacing of 28 mm. Fuel salt is a 45/45/10 mixture of sodium fluoride, uranium tetrafluoride (with the uranium containing 5% 235U and 10-20% 233U) and zirconium tetrafluoride. The coolant salt is a mixture of 78% sodium fluoride and 22% thorium tetrafluoride. A 10 cm deep layer of molten bismuth is at the bottom of the reactor tank and a pumping apparatus is suspended from the reactor lid that continually sprays the bismuth on the surface of the coolant salt in the space between the fuel tubes and steam tubes. A portion of the pumped bismuth is diverted through a cooling system that cools the bismuth to 50 C above its melting point. Precipitated uranium and thorium bismuthides are collected and processed to recover 233U. Pellets of metallic thorium placed at the bottom of the tank ensure that the bismuth is always saturated with thorium metal, thereby causing reductive extraction of uranium produced in the coolant by the action of neutrons on the thorium into the molten bismuth layer. The reactor is similar to that described in example 1 except as follows. It is particularly designed to allow sustained periods of operation without replacement of the fuel tubes. The 20% of fuel tubes not initially containing fuel salt are filled with 70% natural uranium trichloride/5% uranium tetrachloride/25% NaCl instead of coolant salt. This results in a low level of fission and hence heat production within the tube due to fission of uranium isotopes but a relatively large absorption of neutrons by 238U. Progressive replacement of these tubes with tubes containing fuel salt therefore adds significantly to the net reactivity of the core which will otherwise decline as fissile isotopes are depleted. Coolant salt contains cadmium fluoride, or another neutron absorbing fluoride, at up to 5 mol % at reactor start up. As the core reactivity falls due to fissile isotope consumption, the cadmium fluoride is progressively reduced to cadmium metal by addition of metallic sodium to the coolant salt. The cadmium metal is molten at the temperature of the coolant and accumulates as a thin layer at the bottom of the tank. The reactor is similar to that described in example 1 except as follows. It is particularly designed to allow long periods between fuel tube replacements while consuming a pre-existing inventory of transuranic isotopes without producing significant amounts of new transuranic isotopes. The fuel salt contains 15-20% of trichlorides of transuranic isotopes and 80 to 85% thorium tetrachloride. Production of 233U within the fuel salt from the thorium is not sufficient to maintain the reactivity of the core which accordingly falls in temperature quite rapidly as fissile material is consumed. Fresh fissile material in the form of pellets of 5 mm diameter formed from frozen transuranic trichloride is added periodically to each fuel tube as its individual average temperature falls below a defined threshold. The fuel pellets are inserted into each fuel tube through a mechanism in the fuel tube cap assembly and fall down through the spiral portion of the fuel tube until they reach the molten fuel salt in which they dissolve and mix. Although the invention has been described in terms of embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein. In particular, the following features are identified which may be used with a molten salt fuelled fission reactor separately or in combination. The heat transfer from the molten salt fuel is achieved by convection or mechanical agitation of the salts within the tubes, i.e. the fuel salts are not driven through external pumps or heat exchangers as in conventional molten salt reactors. The blanket liquid is a molten salt which circulates convectively within a single tank. In the breeder configuration, the blanket liquid acts as coolant, neutron absorber, and breeding blanket for the reactor. A layer of molten metal is present in the blanket, within which the bred fissile isotopes are dissolved, thereby extracting them from the blanket. The above list is not limiting and the skilled person will appreciate that other features of the above disclosure may be used alone or in combination with other features. Any discussion of specific materials, concentrations, dimensions, or other specific properties of the reactor are to be taken as exemplary and non-limiting, and the skilled person will recognise that other suitable materials, concentrations, and dimensions will be possible, and within the scope of the invention.
040381366	abstract	A hexagonal ring structure whose internal contour conforms to the external contour of the reactor core rests on the periphery of the reactor diagrid and is constituted by a plurality of layers of metallic plates. The layers are maintained in relative positional relation by means of clamping members, the plates of one layer being angularly displaced with respect to the plates of adjacent layers. The bottom end-connectors of the elements constituting the lateral shield system are fitted in vertical through-holes formed in the ring structure.
	claims	1. A radioactive composition of matter, comprising:a plurality of radioactive particles and a plurality of affinity metallic particles disposed in a ceramic matrix;wherein the plurality of affinity metallic particles have an affinity for isotopes of hydrogen;wherein the composition yields a first rate of emission and has an affinity to absorb an isotope of hydrogen; andwherein the composition yields a second, increased rate of emission in response to absorbing the isotope of hydrogen. 2. The composition of matter of claim 1, wherein the ceramic matrix comprises a zirconium oxide. 3. The composition of matter of claim 1, wherein the composition is configured to absorb the isotope of hydrogen in gaseous form. 4. The composition of matter of claim 1, wherein the radioactive particles comprises a Uranium salt. 5. The composition of matter of claim 4, wherein the Uranium salt comprises Uranium acetate. 6. The composition of matter of claim 1, wherein the affinity metallic particles include Palladium. 7. The composition of matter of claim 6, wherein the Palladium comprises between 5% and 35% by mass of the composition. 8. The composition of matter of claim 1, wherein the affinity metallic particles include Nickel. 9. The composition of matter of claim 8, wherein the Nickel comprises between 5% and 35% by mass of the composition. 10. The composition of matter of claim 1, further comprising 0.5% and 5% by mass of one or more elements having Z from 57 to 71. 11. The composition of matter of claim 1, wherein the affinity metallic particles comprise a plurality of grains having an average grain size of less than 1 micron. 12. The composition of matter of claim 11, wherein the grains are substantially isolated from each other. 13. The composition of matter of claim 12, further comprising zeolites that contain and isolate the grains. 14. The composition of matter of claim 11, wherein the ceramic matrix comprises zirconium oxide that contains and isolates the grains. 15. The composition of matter of claim 1, wherein the isotope of hydrogen comprises Deuterium. 16. The composition of matter of claim 1, wherein the isotope of hydrogen comprises Tritium.
053965256	claims	1. Method for repairing the internal surface of an adapter of tubular shape passing through a head of a nuclear reactor vessel cooled by pressurized water and fastened to the head by a weld, said method comprising the steps of (a) carrying out a detection and inspection of cracks on an internal surface of said adapter at least in a zone close to said weld, using remote inspection operations comprising at least one dye penetration inspection with remote borescope examination of cracks revealed by dye penetration; (b) excavating at least one excavation cavity by machining to a specified depth of each zone of said internal surface of said adapter having a crack; and (c) as a function of the result of a dye penetration inspection in each zone having a crack, building back up the zone after excavation. (a) making a first excavation cavity to a first depth of pass in a radial direction of a wall of said adapter; (b) inspecting the external surface of the excavated zone in said wall of said adapter; (c) considering a crack as having been repaired if said crack is not detected on said external surface of said excavated zone; (d) carrying out additional machining at a second depth of pass in a radial direction inside said wall of said adapter, in the case when a crack is detected on said external surface of said excavated zone; (e) making a new inspection of said external surface of said excavated zone; and (f) building back up said excavated zone with a weld metal, in the case when said crack is detected on the new external surface of said excavated zone. 2. Method according to claim 1, comprising the step of inserting tooling inside said adapter, into a position defined as a function of the location of the cracks using the dye penetration operation and making said excavation cavity by machining of said internal surface of said adapter by using said tooling. 3. Method according to claim 1, comprising the steps of 4. Method according to any one of claims 1 to 3, comprising carrying out the detection and inspection of cracks on said internal surface of said adapter through a first end of said adapter located above the head of the vessel, and making the excavation cavity by machining inside the adapter, through a second end of the adapter located below a head of said reactor vessel. 5. Method according to claim 4, comprising cutting a lower end of said adapter projecting below said head and then making said excavation cavity or building said internal surface of said adapter back up. 6. Method according to claim 1, comprising brushing and cleaning said internal surface of the adapter and then carrying out a crack detection and inspection using dye penetration on said internal surface of said adapter.
	description	The present application is a divisional application of U.S. patent application Ser. No. 16/404,342 filed on May 6, 2019, entitled “MEDICAL DEVICES FOR DIAGNOSTIC IMAGING,” which is a divisional application of U.S. patent application Ser. No. 15/590,751 filed on May 9, 2017, and titled “MEDICAL DEVICES FOR DIAGNOSTIC IMAGING,” which claims priority under 35 U.S.C. 119(e) to the filing date of U.S. Provisional Patent Application 62/333,754 filed, May 9, 2016 entitled, “DEVICES FOR MONITORING THE DELIVERY OF RADIO-ISOTOPE TAGGED THERAPEUTIC DRUGS; DIAGNOSTIC IMAGING; AND FOR REAL-TIME DOSIMETRY FOR OCCUPATIONAL AND PERSONAL HEALTH AND SAFETY APPLICATIONS FROM RADIOACTIVE MATERIAL AND IONIZING RADIATION GENERATING DEVICES,” the contents of which are incorporated herein by reference in their entireties. A majority of research in medicine takes advantage of radiotracers for the identification of areas to which tagged drugs travel in the body. Where the drug is and when it is there, are critical pieces of information for scientists developing new drugs and applications. When treating patients with radiotherapeutic medications designed to treat a local target area of the body, there is often a need to know the medication's total dose received by the target area, as well as the dose received by other, undesired areas. The dose can be controlled by the rate at which the medication is concentrated in the target area and the rate at which it is dissipated. For medications that are radioactive or have a radioactive tag, concentration and dissipation can be determined by local measurements of radioactivity. For example, if a radio-tagged medicine designed to treat deep-vein thrombosis (DVT) were used in conjunction with a bed containing sensors, real-time computed tomography would allow for assessment of treatment. This assessment may improve medical outcomes by allowing medical staff to administer the smallest dose that provides therapeutic value, potentially reducing complications arising from side effects of drugs, while also monitoring potential side effects from the dose received by other parts of the body. The ability to monitor where the drug is at all times is a key knowledge point. Various embodiments are directed to a medical imaging system or device including one or more pixilated imagers positioned to acquire patient image data; one or more position sensors positioned to acquire patient position data; one or more processors operably connected to each of the one or more pixilated imagers and one or more position sensors, the one or more processors being configured to calculate a three-dimensional mass distribution based on patient image data and patient position data. In some embodiments, the one or more processors is configured to detect radiopharmaceuticals using the patient image data. IN particular embodiments, the system may further include a mounting apparatus on which the one or more pixilated imagers and one or more position sensors are mounted, and in some embodiments, the one or more pixilated imagers and one or more position sensors can be movable on the mounting apparatus. In certain embodiments, each of the one or more pixilated imager, one or more position sensor, or combinations thereof can be individually attached to a mounting apparatus. In some embodiments, the system may further include a platform positioned to allow acquisition of patient image data, and the platform may be a table, a bed, or a chair. IN certain embodiments, at least one of the one or more position sensors can be mounted on the platform. In various embodiments, each of the one or more pixilated imagers may individually be selected from the group consisting of photodiodes, color imagers, monochrome imagers, low light imagers, infrared (IR) imagers, thermal imagers, carbon-metal-oxide semiconductor (CMOS) imagers, and charge-coupled device (CCD) imagers, and in various embodiments, the position sensors may be selected from the group consisting of temperature sensors, piezoelectric pressure transducers, MEMS sensors, and capacitive contact-detection technology. Further embodiments are directed to a radiation detection system, including a radiation adsorption bed; an air inlet; an air outlet; and a pump operably connected to the air inlet or air outlet configured to create a flow of ambient air through the air inlet, over the radiation adsorption bed, and out the air outlet. In various embodiments, the radiation adsorption bed comprises an activated-carbon sorbent. In some embodiments, the system may further include a temperature sensor positioned to measure an internal temperature of the system, and in some embodiments, the system may further include a heating element operably coupled to the temperature sensor and configured to heat the adsorption bed based on the internal temperature of the system. IN particular embodiments, a processor may be operatively coupled to the temperature sensor and a network connection device and configured to store the internal temperature of the system in at least one of a local storage device and a remote storage device. In some embodiment, the system may further include a radiation monitor positioned to measure a radiation level in the radiation adsorption bed, and in particular embodiments, a heating element may be operably coupled to the radiation monitor and configured to heat based on the radiation level of the system. In some embodiments, the heating element may raise the temperature of the radiation adsorption bed to about 60° C. and about 150° C. The system of various embodiments, may include a housing encompassing the radiation adsorption bed, air inlet, air outlet, and pump, and in some embodiments, the housing may be configured as a wearable device. Other embodiments are directed to a wearable radiation detection system, including a housing; one or more pixilated imager chips located within the housing; one or more processors operably connected to each of the one or more pixilated chips, the one or more processors being configured to detect radiation using patient image data. The above summary of the present invention is not intended to describe each illustrated embodiment or every possible implementation of the present invention. The detailed description, which follows, particularly exemplifies these embodiments. Before the present compositions and methods are described, it is to be understood that they are not limited to the particular compositions, methodologies or protocols described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit their scope which will be limited only by the appended claims. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments disclosed, the preferred methods, devices, and materials are now described. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. “Substantially no” means that the subsequently described event may occur at most about less than 10% of the time or the subsequently described component may be at most about less than 10% of the total composition, in some embodiments, and in others, at most about less than 5%, and in still others at most about less than 1%. For purposes of the description hereinafter, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” and derivatives thereof shall relate to the orientation of embodiments disclosed in the drawing figures. However, it is to be understood that embodiments may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. It is to be understood that the disclosed embodiments may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments. 1. Medical Imaging Various embodiments are directed to medical imaging devices for carrying out tomography and methods for medical imaging. The devices and methods use ubiquitous digital cameras to detect ionizing radiation from radiopharmaceuticals for the identification of areas to which tagged drugs travel in the body. Where the drug is and when it is there, are critical pieces of information for scientists developing new drugs and applications. When treating patients with radiopharmaceuticals designed to accumulate in a target area of the body, it is often necessary to know the medication's total dose received in the target area, as well as the dose received by other, undesired areas. The dose received can be determined by the rate at which the medication is concentrated in the target area and the rate at which it is dissipated. For medications that are radioactive or have a radioactive tag, concentration and dissipation can be determined by local measurements of radioactivity. Embodiments of the invention include methods, devices, and systems in which with one or more image capture devices containing pixilated imagers, position sensors, and processing devices to perform real-time computed tomography that allows for real-time imaging and assessment of treatment. In certain embodiments, the methods, devices and systems may be used in conjunction with radiopharmaceuticals to improve contrast of various body part. This assessment may improve medical outcomes by allowing medical staff to administer the smallest dose that provides imaging or therapeutic value, potentially reducing side effects of drugs. The ability to monitor where the drug is at all times is a key knowledge point. As used herein, the systems of embodiments can be referred to as devices and vice versa. Thus, the systems of various embodiments include the same components as the devices described below. Such devices and systems may include one or more pixilated imagers positioned to acquire patient image data. The pixilated imagers may by positioned by any means. For example, in some embodiments, the pixilated imagers can be mounted on a bed, table, chair, or other apparatus on which the patient is placed for imaging, and in other embodiments, the pixilated imagers can be mounted on a mounting apparatus arranged around a bed, table, chair, or other apparatus on which the patient is placed for imaging. In certain embodiments, the pixilated imagers may be movable while mounted on the mounting apparatus. In some embodiments, the pixilated imagers can be moved and repositioned by hand to, for example, focus imaging on a particular part of the patient's anatomy such as a leg, arm, torso, head, and the like and combinations thereof. In some embodiments, the pixilated imagers can be associated with motors or actuators that move the pixilated imagers in patterns dictated by a computer or processing unit associated with the device. In other embodiments, each of the one or more pixilated imagers can be individually attached to a mounting device such as a tripod that a technician positions before imaging commences. In still other embodiments, the one or more pixilated imagers can be mounting on walls of a room in which imaging takes place. In such embodiments, the imagers can be movable by hand or by motors or actuators associated with each imager, and movement can be dictated by a processor. In some embodiments, the imaging devices may further include one or more position sensors. Like the pixilated imagers, the one or more position sensors can be positioned by any means. For example, in some embodiments, the position sensors can be mounted on a bed, table, chair, or other apparatus on which the patient is placed for imaging, and in other embodiments, the position sensors can be mounted on a mounting apparatus associated with the a bed, table, chair, or other apparatus on which the patient is placed for imaging. In still other embodiments, the position sensors can be mounted on walls of a room in which imaging takes place. In such embodiments, the position sensors can be moveable by hand or by motors or actuators to aid in focusing on a particular part of the anatomy of the patient under study, and movement of the position sensors can be dictated by a processor associated with the device. The imaging device may generally include one or more processors operably connected to each of the one or more pixilated imagers and one or more position sensors. The one or more processors being configured to calculate a three-dimensional mass distribution based on patient image data acquired from the one or more pixilated imagers, patient position data acquired from the one or more position sensors, or combination thereof. For example, in some embodiments, two or more sensors may acquire pressure and temperature data from the patient. The processor may use this data with information related to the actual, known position of the position sensors relative to each other and use image data to produce a two or three-dimensional image of the patient. Simultaneously, the processor may acquire data related to the position and concentration of radiopharmaceutical in the imaged area using the methods discussed below, and overlay this data on the image to show the location and concentration of radiopharmaceutical in the imaged area of the patient. In some embodiments, such imaging can be carried out on a particular part of the patient's anatomy such as a leg, arm, torso, abdomen, head, and the like to provide two or three dimensional images of the body part including the concentration and location of a radiopharmaceutical. In other embodiments, such imaging can be carried out on the entire body of the patient. Images acquired from full-body imaging can be used to compare the concentration of radiopharmaceutical in various parts of the body to identify anatomical anomalies throughout the entire body and the compare, for example, the size and location of such anomalies. For example, images and position data can be acquired after administering a radiopharmaceutical designed to detect deep vein thrombosis of a patient's leg to locate blood clots in the vasculature of that leg. In other embodiments, imaging and positioning of the patient's whole body may identify additional blood clots in, for example, the vasculature of untreated leg or arms, lung, or brain. The imaging and positioning data can further provide information relating to the relative size and density of the blood clots identified in various parts of the patient's body. Such information may allow physicians to determine the type of treatment necessary, overall condition of the patient, criticality of treatment, and develop an informed timeline for treating the patient. The various embodiments are not limited to a particular type of pixilated imager. For example, the pixilated imagers can be photodiodes, color imagers, monochrome imagers, low light imagers, infrared (IR) imagers, thermal imagers, carbon-metal-oxide semiconductor (CMOS) imagers, charge-coupled device (CCD) imagers, and the like and combinations thereof, including imager containing silicon-germanium, germanium, silicon-on-sapphire, indium-gallium-arsenide, cadmium-mercury-telluride or gallium-arsenide substrates and the like, or combinations thereof. In some embodiments, raw video data can be captured by an ensemble of three-dimensional structure scanning sensors. Examples of structure scanning sensors could include one or more of the following used individually or in combination: video or still-image cameras, ultrasonic rangefinder, or other types of devices that identify the physical location of the subject. In some embodiments, the pixilated imagers can include optics such as lenses and focusing apparatuses necessary to focus the imager and created images. The imagers can be configured to take still images, continuous video images, or combinations thereof. For example, in some embodiments, the pixilated imagers can acquire video images of the patient, and still images at certain points during the procedure such as, for example, particular time points identified by the user, when the radiopharmaceutical reaches a particular concentration at a location in the body, or combinations thereof. The pixilated imagers can be arranged to focus on an individual part of the patient's anatomy or the patient as a whole, and in some embodiments, the imagers can be movable by hand or automatically as dictated by a processor associated with the device. In some embodiments, the pixilated imagers may include a pixilated chip without optics or focusing apparatuses and position sensor data can be used to determine the location of the radiopharmaceutical in the patient's body, produce images of the patient, and combinations thereof. The positions sensors can include, for example, temperature sensors, piezoelectric pressure transducers, MEMS sensors, capacitive contact-detection sensors, accelerometers, and the like and combinations thereof. The position sensors may generally acquire position data through the procedure, and can be arranged to acquire position data for an individual part of the patient's anatomy or the patient as a whole. In some embodiments, the position sensors may individually be operably connected to the processor, and in other embodiments, the position sensors may be operably linked to each other and/or to additional positioning apparatuses such as GPS or other location means. Data from the position sensors and pixilated imagers mounted at specific designated locations on the device or in a treatment room are used to determine the precise location and distribution of the subject's body. The location and physical distribution information are used to support calculations in order to increase the precision of the results. The use of pixilated imagers arranged in multiple fixed-planes and/or conformal manifolds further increases the precision of the calculations and results. To obtain these data, additional planes of sensors are used on one or more sides of the patient. Although a full box surrounding a patient may or may not be used, each additional sensor adds numerous baselines to the calculations, potentially increasing the value of the data, and the degree of localization achieved. Where localized temperature is needed, additional sensors or thermal IR pixilated imagers are used. In further embodiments, the devices described above can be combined with traditional computer tomography (CT) devices, position emission tomography (PET) devices, magnetic resonance imaging (MRI) devices, single-photon emission computerized tomography (SPECT) devices, ultrasound devices, and the like. Such devices can include pixilated imagers and position sensors, and processors associated with these devices can be used to produce detailed images of the patient and more precisely located radiopharmaceuticals and other tracers. For example, potential orthogonal measurements can be made using digital imager-based sensing devices that can help confirm or confound the functional assessment by PET. A key functionality of the platform is to integrate heterogeneous data sets from other sensors integrated in real time using the camera-imager-based detection device to collect and transmit information to a central processing unit. In some embodiments, the imaging devices described above can be used in conjunction with surgical interventions to aid the surgeon in locating abnormalities in the patient. For example, the devices of embodiments can be used with a gamma-knife/gamma-scalpel surgery, a type of radiation therapy used to treat tumors and other abnormalities. The imagers of various embodiments can permit medical staff to monitor the application of treatments in situ and in real time as an independent safety system that could issue an alarm in the event excessive dose is inadvertently delivered. The devices may also provide real-time treatment information to confirm the delivery of therapeutic levels of radiation. Such real-time monitoring could serve as a permanent record of the therapy, enabling doctors to plan future treatments with the goal of minimizing delivered dose to healthy tissue while maximizing dose to the tumor. It would also be a valuable source of data for researchers seeking to improve the medical standard of care that is not currently available. Further embodiments are directed to wearable imaging devices having incorporated one or more position sensors and, in some embodiments, one or more pixilated imagers. For example, in some embodiments, articles of clothing, such as pants, shirts, headwear, coveralls, or pajamas incorporating one or more positions sensors may be used in combination with mounted pixilated imagers in devices such as those described above, and image, position, and location of radiopharmaceutical data acquired from these devices can be used to create detailed images of the patient and the locations and concentration of radiopharmaceutical in various locations in the patient's body. In other embodiments, the one or more position sensors can be incorporated into a blanket that is used to cover the patient during imaging. In other embodiments, the one or more pixilated imager may be incorporated into the article of clothing or blanket. In such embodiments, the pixilated imagers can identify the location and concentration of radiopharmaceuticals while the position sensor data is used to produce a two or three-dimensional image of the patient. In some embodiments, the pixilated imagers may include optics and focusing apparatus, and in other embodiments, the pixilated imagers may be a pixilated chip with no optics or focusing apparatus. Additional embodiments include methods for using the devices described above to produce tomographic images of the patient or to locate radiopharmaceuticals or therapeutic radiation in the body of a patient. For example, in some embodiments, as illustrated in the flow diagram FIG. 1, position data acquired from position detectors such as pressure sensors 105, and image data acquired from pixilated imagers 110 can be used to produce a mass distribution and patient position information combined with the position and pressure sensor data to calculate a shielding model 115. Radiation data may be collected from the one or more pixilated imagers or pixilated chips 120 and these data may be combined with calculated shielding model to perform tomography 125. The steps provided above can be carried out in essentially any order. For example, in some embodiments, radiation detection 120 can be carried out in a first step and position and pressure sensor data can be used to calculate a shielding model 105, 110, 115 of only portions of the patient's body that emit radiation at a particular level. As illustrated in the flow diagram of FIG. 2, in some embodiments, different processors can carry out data processing for various steps of the methods simultaneously and the processed data can be combined by a central processor. For example, a mass distribution model can be created from image data and position center data at one processor 210, radiation measurements can be determined in another processor 215, and relevant meta-data can be compiled in another processor 220. These data can be compiled and used to create CT data reconstruction 230 in any one of the processors used in the preceding steps or in another processor. In some embodiments, the radiation data can be collected and analyzed by data-processing boards, which may be single-board computers (SBC), digital signal processors (DSP), field programmable gate array (FPGA) processor boards, general-purpose computers, or specially designed processing components. The sensors may be embedded on computing devices (middle tier) or flow data to a processor that is physically distinct or even distant. Once the processors make and quantify each radiation measurement, the resulting readings can be sent to another processor, which collects and collates these measurements with associated meta-data. The meta-data may include, for example, the subject's location, the temperature of the sensor to characterize signal and noise characteristics, amplifier settings to characterize signal and noise characteristics, the sensor's identification code to keep track of differing sensor characteristics, the type of sensor (e.g. ELP-USB30W02M-L21 CMOS sensor or OV6211 CMOS sensor, a Cesium-Iodide crystal based detector, etc.), and other similar meta-data. The data and meta-data can be stored and made available for subsequent sensor-fusion and analysis. In another embodiment, the collection of the physical location and physical extent of a subject can be used to improve computed tomography calculations. Multiple detectors may be positioned and aimed to capture the location and physical extent (i.e. size) of the subject. The subject may be simultaneously imaged by several pixilated imagers that surrounding the subject. Image processing software can be used to perform feature detection, identification of common features, image registration, and calculation of trigonometric parallax. From this information a three-dimensional model can be developed that mimics the subject's physical extent. Since this mathematical model is tied to the subject's physical body, a detailed model is built that incorporates body structures (e.g., musculo-skeletal and organ structures). This model can then be used to add constraints to the CT calculations to improve the calculations for the source and shielding terms. In some embodiments, 3-D structure data can be collected by pixilated imagers (bottom tier) and analyzed by data-processing boards (middle tier), which may be single-board computers (SBC), digital signal processors (DSP), field programmable gate array (FPGA) processor boards, general-purpose computers, or specially designed processing components. The sensors may be embedded on compute devices or flow data to a processor that is physically distinct or even distant. Once the processors make and quantify each 3-D measurement, the resulting readings are sent to another processor, which collects and collates these measurements with associated meta-data. The meta-data may include: the subject's location, the scanner's location, the temperature of the sensor to characterize signal and noise characteristics, amplifier settings to characterize signal and noise characteristics, the sensor's identification code to keep track of differing sensor characteristics, the type of sensor (e.g., video camera, LIDAR, RADAR, etc.), and other similar meta-data. The data and meta-data are stored and made available for subsequent sensor-fusion and analysis that incorporates other position data. This analysis can build a full 3-D model that contains locations of key components (e.g., bones, heart, bladder, thyroid gland, etc.) as well as the composition of those structures. This combined digital model will be used as input. In further embodiments, the results of the radiation measurements over time and location can be fused with the detailed mass-distribution model. Associated subject meta-data informs the details of the CT reconstruction. The resulting computed image makes use of all available data to achieve a cost-effective time-tagged, 3-dimensional representation. In some embodiments, the systems and devices described above may include one or more mobile devices having a display, a processor, a location-aware component (for example, Global Positioning Satellite (“GPS”) component, a wi-fi location component, indoor positioning system capability, and a means for communicating with processor, and in certain embodiments, the processor may be operably connected to other computing devices, such as, for example, a server. Each mobile device may be configured to communicate with a processor via a network, such as, for example, the Internet, an intranet, a wide area network, a metropolitan area network, a local area network, an internet area network, a campus area network, a virtual private network, a personal network, and the like and combinations thereof. For example, the processor may communicate digital still or digital video images to the mobile device, and the mobile device may transmit commands to the processor to, for example, provide images of a particular body part of the patient or focus the one or more imagers on a particular location. A user having access to the mobile device may control all or some of the aspects of the device throughout use. Table 1 provides various examples of certain types of imaging that can be carried out using the devices describe above. PotentialImagingFunctionalorthogonalDiseaseagentassessmentPrinciplemeasurementCardiacFDGMyocardialDifferentiate betweenVisualmetabolism at rest,ischemic, viableCardiac markersmeasure fatty acidmyocardium andin blooduptake by thenecrotic, scarredmyocardiummyocardiumFDGMyocardialIn compromisedVisualperfusionmyocardium, uptake ofCardiac markersFDG indicate viabilityin bloodand likely positiveresponse to myocardialrevascularization11C-MQNBReceptor densityCongestive heart failureis associated with anup-regulation ofmyocardial muscarinicreceptorsFDGPresence ofFDG uptake correlatesarterial plaquewith macrophageaccumulation andinflammation.VascularFDGEffectiveness ofTherapy with anti-Visualdevice or drugs ininflammatory agents inCardiac markersreducing plaquearterial vasculaturein bloodreduces plaque FDGuptake.CancerFDGDiagnosis, stagingHigher FDG uptake byPanels for cancerand detection oftumorsmarkersmetastatic diseaseFDGPrognosticinformation basedon response totherapyInfectious -FDGNodal PET/CTHigh nodal FDG uptakeFluorescentHPVparameters predictshould raise suspicionbiomarkerHPV statusfor positive HPV statusNeurologicalflorbetapir F-Estimate ofGlucose transport is up-18amyloid neuriticregulated in diseasedAmyvidplaque density intissuedifferent regions ofthe brainflorbetapir F-Dose response ofIncreasing dosages of18new drugdrug candidates removeAmyvidcandidatesincreasing amounts ofdesigned toplaque associated withAlzheimer's disease Various improvements on existing technology can be obtained using the devices and methods described herein. For example, in some embodiments, higher spatial resolution determinations of the location of radioactive materials and enhanced angular resolution of the resultant tomographic reconstruction of source material distribution beyond the current technology can be obtained. Embodiments include several techniques that can increase the resolution compared to simply using the average 3-dimensional location of each image sensor as a location node in the tomographic reconstruction. For example, more than one pixilated imager or pixilated chip can be used in a specific location, thereby breaking sensitivity degeneracies. Shielding can be employed to preferentially occlude certain regions, yielding an effect similar to “coded aperture” techniques. Individual chips or clusters of chips can be placed inside of boxes or cylinders that are open (unshielded) in only one direction, greatly reducing the solid-angle that is effectively contributing to the overall reconstruction. Algorithms can be used to compute the direction of origin of each gamma ray from its on-chip energy distribution. In certain embodiments, combinations of these techniques can be incorporated into the device. These techniques are described in more detail below. Multiple chips in one place—Placing multiple detectors near one location in the distribution of detectors gives two advantages to the system. Locally, they enhance sensitivity by providing more detector volume and thereby geometric gain. This effect is proportional to the square root of the number of equivalently sized detectors. More importantly, with strategically chosen spacing at various locations, the additional number of baselines obtained by combining multiple, nearby pairs, increases the spatial resolution that can be achieved in the CT analysis. The ability to improve the spatial resolution of source terms between sets of multiple detectors will also improve contrast data for overall image quality improvement. Coded-aperture-like shielding—For large, single detectors, or arrays of detectors, at a location, a suitably constructed mask made of lead or a similar radiation-blocking material can be used to occlude certain portions of the field of view from these detectors. In this case, the distribution of radiation detections on the detector can then be used to recover directional information regarding the origin of the gamma rays. Use of shielded boxes/cylinders to occlude large solid-angles—Similar to the above, in this case the detector or detectors are partially enclosed in an enclosure made of lead or a similar ionizing radiation-blocking material. For example, by placing a detector in an open cylinder or cone, the sensor's sensitivity to off-axis radiation is diminished, whereas normally the detectors are sensitive to ionizing radiation coming from all directions. By so enclosing them, the direction from which detected ionizing radiation could be coming is restricted. This additional information can then be used in assessing the spatial distribution of ionizing radiation sources within the field of interest. This effect is particularly significant when using relatively lower energy radiation, e.g. less than ˜250 keV, which is far less penetrating for bone than higher energy radiation. Increasing sensitivity or selectivity by temperature modulation or other active sensing—The use of temperature modulation has the potential to enhance the sensitivity or selectivity of pixilated imagers or pixilated chips to gamma rays (or betas). This approach can be used effectively with metal oxide (MOX) sensors for gas mixtures in which the MOX sensor adapts its operating temperature in real time to sequentially reduce uncertainty in the concentration estimates for a gas mixture. This is an example of what is known as active sensing, where the sensor adapts to the measurement environment. In various embodiments described above, radiation may be detected using the method illustrated in FIG. 3. For example, the processor may examine 310 individual portions of the capture information such as, for example, frames within an image and the like to identify 315 local maxima and/or minima. In embodiments in which the pixilated imager is calibrated to detect radiation, the application environment may identify local maxima. As each local maximum is identified 315, the application environment may compare 320 the characteristics of the image pixels comprising the local maximum with any pixels substantially surrounding each local maximum. A wide range of suitable maxima-finding algorithms may be used to compare local maxima with the surrounding pixels. For example, a non-limiting way of comparing may include evaluating the four closest pixels (4CP) in digital image data. If the pixel or image data point under consideration is (X,Y), then the 4CP are: (X+1,Y), (X,Y+1), (X−1,Y), and (X,Y−1). The local background value of the imager may be taken as the average of the eight pixels corresponding to (X−2,Y−2), (X,Y−2), (X+2,Y−2), (X−2,Y), (X+2,Y), (X−2,Y+2), (X,Y+2), (X+2,Y+2). Alternatively, if a known reference object is in the field, it may be set to be the background and the average of the pixels or data points corresponding to the object set to the background. Based on the captured information and/or the comparison, the application environment may determine 325 whether a potential hit exists. For example, if the local maxima that meet or exceed one or more thresholds may be considered areas that include potential hits for radiation emission. In embodiments where radiation is detected, the thresholds may include total counts in the local maximum, total counts summed over the local maximum plus surrounding pixels, an excess of either of the above-described thresholds with respect to a measure of the average counts in pixels away from any local maximum, ratios of such total counts or excesses to the average, standard deviation, and/or other statistical measures of counts in areas away from a local maximum. If a potential hit exists, the application environment may add 330 the potential hit to a list or enter the potential hit in a database and store information regarding the potential hit for further review. Once a potential hit has been added to the potential hit list, the application environment may determine 335 whether additional portions must still be examined, and if so, may examine 310 the additional portions. In some embodiments, the application environment may repeat the process or identify local maxima or minima meeting lower or higher thresholds, where such adjustments to the thresholds may be determined from the information stored from previously detected potential hits. If no more frames remain, the application environment may assess 340 each potential hit in the hit list with one or more additional quality control (QC) filters. Examples of additional QC filters may include, but are not limited to, limits on the number of potential hits detected on a single frame, limits on the number of potential hits detected on a single pixel and/or on groups of neighboring pixels, limits on the frequency of potential hits detected on a single pixel and/or on groups of neighboring pixels, comparison to thresholds as previously described herein as may have been adjusted according to the information stored regarding all or a portion of the potential hits in the list or other lists, or a location on the component. The application environment may determine 345, after assessing 340 each potential hit, whether each potential hit is an actual hit. A potential hit may be determined to be an actual hit if it passes some or all of the additional QC filters. If the potential hit is found to not be an actual hit, the application environment may discard 350 the potential hit from a final hit list, and may optionally adapt dynamic parameters that would update thresholds and/or QC filters. If the potential hit is found to be an actual hit, the application environment may add 355 the potential hit to the final hit list and/or enter the actual hit into a database and store the actual hit. In some embodiments, the application environment may also add 355 information relating to the hit to the final hit list. Examples of information relating to the hit for embodiments in which imagers are calibrated may include, but are not limited to, images, coloration of local maxima pixels, coloration of surrounding pixels, the total number of pixels examined, the total number of frames, the detection parameters associated with the maximum or minimum detection, additional QC filter results, the number of hits that passed the additional QC filter, the number of potential hits that did not pass the additional QC filter, information regarding the initialization results obtained from the initialization, information about the electronic device, information about the components, geolocation information, information regarding a user of the electronic device and the like, or combinations thereof. Examples of information relating to the hit for embodiments related to other components may include baseline magnetic readings (e.g., strength and direction), variability of magnetic readings, various statistical moments of magnetic readings, baseline accelerometer readings, variability of accelerometer readings, various statistical moments of accelerometer readings, temperature readings, variability of temperature readings, various statistical moments of temperature readings and the like, or combinations thereof. 2. Occupational Health and Safety As discussed herein, radiology is regularly used in medical environments (e.g., hospitals). Generally, the staff or personal in these facilities need to monitor their exposure to radiation. Thus, there is an ongoing need for dosimeters to worn by hospital staff, security personnel, and the like who work near X-ray scanners or devices that put off trace amounts of radiation (e.g., workers who operate near industrial radiography equipment, aircrew, etc.). Accordingly, some embodiments described herein may provide an improvement over current dosimeter technology, (e.g., dosimeter badges) by allowing continuous, real-time readings of ionizing radiation exposure. In addition to radiation exposure levels being recorded, additional user information, such as for example, positional information (e.g., relative to the building they are located in) and time stamping may be recorded to help locate a potential source of radiation exposure. Moreover, the ability to provide data to a Radiation Safety Officer, in real time, as to the exposures being monitored on all workers at potential risk for radiation enables full compliance with even the most strict applicable policies and regulations. Accordingly, in some embodiments, a radiometer system may be used that includes a small, light-weight sensor. The light-weight sensor may then be in communication with one or more computers (e.g., laptop or server) in order to analyze, store, and transmit the results from the sensor to a secondary system. In some embodiments, a sensor, (e.g., one or more image capture devices (digital pixelated image sensor)) may be operatively coupled to one or more controllers, one or more digital signal processors (DSP), or other similar computer node. The sensor may be worn by a user as a wearable device (e.g., a badge, a patch, a bracelet, a pendent, etc.). In some embodiments, the sensor may be solo in nature, collecting data and communicating with the one or more controllers or one or more DSP to analyze the data captured by the sensor. Additionally or alternatively, a plurality of sensors may operate in a group (e.g., mesh network, ad-hoc network, a network with a single base station, etc.). By way of a non-limiting example, medical staff who are performing a fluoroscopy procedure may wear multiple sensors (e.g., dosimeters) at key locations on their bodies. In some embodiments, the sensors may be located at an individual's core, at an individual's extremities, and/or at areas considered to be radiation sensitive. Once the data is collected by the one or more sensors, it may be transmitted as either raw data (e.g., video, long exposure images, etc.) or as reduced data (e.g., determined radiation results) via a wired network connection or wireless network connection (e.g. Bluetooth, Wi-Fi, etc.) to a computing device (e.g., smartphone, tablet, laptop, desktop, server, etc.). In some embodiments, a specific software application (e.g., GammaPix, etc.) may allow a smartphone or other computing device to receive and analyze the images transmitted by the one or more sensors. In addition, in some embodiments, the computing device may store the results, which may then be displayed locally or remotely (e.g., after being transmitted to a remote location, such as the office of an attending physician) for review. In some embodiments, the systems and devices described above may include one or more mobile devices having a display, a processor, a location-aware component (for example, Global Positioning Satellite (“GPS”) component, a wi-fi location component, indoor positioning system capability, and a means for communicating with processor, and in certain embodiments, the processor may be operably connected to other computing devices, such as, for example, a server. Each mobile device may be configured to communicate with a processor via a network, such as, for example, the Internet, an intranet, a wide area network, a metropolitan area network, a local area network, an internet area network, a campus area network, a virtual private network, a personal network, and the like and combinations thereof. As discussed herein, an image capture device (e.g., one with a pixelated imager) may be used to track or monitor radiation levels. Thus, although personal dosimeters exist, an embodiment, as described herein may allow a personal dosimeter to be constructed from any electronic device that contains a pixelated imager. By way of non-limiting example, a wearable device (e.g., a common wrist-computing device or the like) may capture data and process it onboard using organic compute capabilities (i.e., an embedded processor). Additionally or alternatively, the data may be captured and either partially or wholly processed onboard the wearable device or not processed onboard at all. When the wearable device is not used for the complete processing of the detected data, the wearable device may transmit the intermediate-processed or raw data to an external compute node (e.g., smartphone, tablet, laptop, etc.). That node may be another mobile device, a nearby computer, or a far distant resource. It should be understood by those skilled in the art, that the transition may happen directly (e.g., via Bluetooth) with a device in close proximity, and/or through the use of proxy devices (e.g., a Wi-Fi hotspot and the internet). Thus, the computer device used for processing the information gathered from the wearable sensor may be in close proximity (e.g., a user's smartphone) or extremely far away (e.g., a remote server accessed via the Internet). In some embodiments, and as discussed herein, a dosimeter (e.g., sensor) may provide real-time data to a remote computer. The remote computer may be located in a stationary office, mobile vehicle, determined command-post, or the like. In a further embodiment, the remote computer may be monitoring and receiving information from a plurality of dosimeter devices (e.g., devices carried by each person on the medical staff). The monitoring of radiation in real time allows for quick and responsive action. For example, if an individual were to receive a sudden increase in dose-rate (e.g., radiation dose rate), or begins to approach their administrative or safety limit, an action can be performed (e.g., alarm can be sound, medical personal may be notified, systems within the proximity of the detection may be shut down to avoid high contamination risks). Accordingly, in some embodiments, users (e.g., staff) may be warned by an alarm or message sent from the detecting device (e.g., dosimeter) or a remote command post (e.g., smartphone, tablet computer, server, etc.). Although medical applications are discussed herein, alternative uses exist. By way of non-limiting example, embodiments discussed herein may be particularly relevant to an industrial radiography unit, which, for example, may perform non-destructive X-ray evaluation of a structure (e.g., bridge, building, etc.) or transport (e.g., ship, plane, vehicle, etc.). In some embodiments, as discussed herein, the sensor (e.g., dosimeter), including the housing may be small in size and cost. Thus, not only does the reduced cost of the detector, allow for the possibility of wearing multiple dosimeters on multiple body parts, but the small size (e.g., footprint) allows them to be less intrusive, and thus more likely to be worn. For example, current products make it difficult to identify an extremity dose. However, in some embodiments, the extremity dose can now easily be determined by one or more rings (e.g., smart rings) worn on each finger, all utilizing telemetry. Once all the sensor data has been collected, calculations may be carried out to determine various factors about the contamination. (e.g., which direction the exposure came from) may be possible in an immediate forensics effort for the Health Physicist. In some embodiments, a camera chip based dosimeter may contain one or more complementary metal-oxide semiconductor (CMOS), semiconductor charge-coupled devices (CCD), or similar image sensors along with camera-control circuitry. It should be understood, that various embodiments are not limited to a particular type of pixilated imager. For example, the pixilated imagers can be photodiodes, color imagers, monochrome imagers, low light imagers, infrared (IR) imagers, thermal imagers, carbon-metal-oxide semiconductor (CMOS) imagers, charge-coupled device (CCD) imagers, and the like and combinations thereof, including imager containing silicon-germanium, germanium, silicon-on-sapphire, indium-gallium-arsenide, cadmium-mercury-telluride or gallium-arsenide substrates and the like, or combinations thereof. Relevant control circuits would accompany photodiode or other sensors. In one embodiment, the data would be processed locally and results shown to the user and transmitted wirelessly to a database for subsequent processing. In another embodiment, the data would be wirelessly transmitted to a processor for centralized analysis, storage, and monitoring. Additional valuable metrology is collected with embedded sensors such as iBeacon, pressure, accelerometer, magnetometer, and thermometer detectors. As described herein, many professions require that personnel who work with radioactive sources or ionizing radiation generating devices use a personal dosimeter based upon the likelihood that they exceed exposure limits. However, due to the limitations of current monitoring systems, other personnel who work nearby, but who are not regularly exposed to radioactivity may not actively use dose-monitoring equipment. This non-use may be due to cost measures, or simply that the utility of current dosimeters makes them ineffective for such individuals (i.e., those not regularly exposed to radiation). However, with the real-time monitoring, the additional information gathered by devices in proximity to radiation may still help determine issues or timing of incidents. Of particular note is the ability of some embodiments to store the time, using a time-tagged exposure record, and optionally store location information associated with the location at which the exposure was logged. As discussed herein, an embodiment may identify an emerging exposure problem before it has a chance to harm anyone, (e.g., a leak from a storage drum that allows radioactive waste to travel from an isolated containment area.) In additional to ensuring safety measures, an embodiment may also be capable of eliminating fraudulent claims of radiation exposure. Although rare, there are instances where individuals have placed a dosimeter near a known radioactive source for an extended period of time, and then claimed to have received a large dose radiation based on their dosimeter reading. Thus, because, as discussed herein, embodiments capture not just location, but also timing of the exposure, it makes fraudulent claims much easier to identify. This saves an employer money, as it avoids the employee's request for damages, legal fees, lost time, as well as other negative consequences. In order to further strengthen this capability, some embodiments may include one or more of body-temperature sensors, accelerometers, and location monitoring technologies to not only determine exposure rate and time, but also various other factors. By way of non-limiting example, the body-temperature sensor may indicate that a user has removed their wearable dosimeter. If it can be shown that radiation exposure of the dosimeter occurred when the user was not wearing their device (e.g., based on the body-temperature sensor), it may indicate that the user was, in fact, not exposed at the same rate as the dosimeter. Moreover, if a dosimeter were to be removed from the user's body and placed near a radiation source, the resulting lack of motion (e.g., based on the accelerometer), combined with its location, would make the resulting exposure a good candidate for further investigation—all the more so if an on-board temperature sensor simultaneously detected a substantially lower “body temperature” reading. Because some embodiments tag the exposure location and time, it may also be straightforward for an embodiment to interact with a separate system and to search security video records for nearby locations to verify that the person of interest did not, in fact, remain where the alleged exposure was reported to have occurred. In addition to monitoring external sources of radiation, the sensor device (e.g., dosimeter) may be used to monitor drug dosage in a patient's body. In some embodiments, a sensor may be worn by the patient as a wearable device (e.g., a patch, a bracelet, a pendent, or other means of attachment), singly or in groups. By way of non-limiting example, radioactive iodine would be expected to concentrate in the thyroid gland. With this knowledge, a sensor device may be placed in an area adjacent or contacting the thyroid gland. Using the dosimeter, a doctor can determine the amount and residence duration of a chemical. Thus, rather than injecting a patient with an average or recommended dose, a doctor may start out using a smaller dose and then assess the resulting concentration of radioactive material actually delivered to the target site. Due to the physiological difference between patients (e.g., size, sex, age, etc.) each person has a unique rate at which they process therapeutic material. Thus, being able to monitor the drug dose accurately and in real time may save many people from receiving an excess dose. In some embodiments, more than one medicine may need to be administered at a time, and each one could contain (or be) a different isotope that emits varying energy gamma rays. The ability to differentiate gamma rays of different energies (see U.S. Pat. No. 9,000,386) would allow for tracking the source materials separately. The advantages, as discussed herein, of multiple embodiments, are: low cost, light weight, small volume, well calibrated, low power, portability, and low network bandwidth requirements. In addition, as discussed, embodiments may provide continuous monitoring, automatic reading, and automatic reporting to a physician or radiation safety officer. In a further embodiment, the new proliferation of activity trackers may be utilized for abilities discussed herein. Generally, these activity (fitness) trackers are wearable devices that monitor and record a person's activity level. These trackers may record activity using a variety so sensors (e.g., pedometer, accelerometers, altimeters, etc.). This recorded data can be used to calculate mileage, estimate calorie expenditures, determine sleep quality, and measure heart rate. Additionally, most activity trackers interact with a secondary device (e.g., a smartphone, tablet, etc.) to generate charts and/or graphs that display the monitored physical activity, food consumption, water consumption, etc. As their capabilities improve, additional technology, such as that disclosed herein may be included. By way of non-limiting example, GammaPix technology could be included in a wearable device/smartphone combination in order to measure the gamma and beta radiation exposure of an individual. In addition to gamma and beta radiation, embodiments may be able to detect radon and other radioactive gases. In at least one embodiment, continuous measurement of ionizing radiation caused by radon and other radioactive gases may be monitored and recorded. For example, for radon, Rn-222 and its associated solid daughter products polonium, bismuth, and lead all emit gamma rays that are easily measured by the system. According to the U.S. Environmental Protection Agency (EPA), radon is a leading cause of lung cancer among non-smokers, and it is responsible for more deaths than second-hand smoking. While radon is regulated to 4 pCi/l of ambient air, the daughter products contribute most of the undesired dose to lungs. Thus, an embodiment may measure the threat level and may show compliance with radon requirements. Radon is invisible, has no smell, and the only way to know one's exposure to radon is through testing. Currently, testing for radon is insufficient because, test procedures do not provide a continuous measurement and, thus, they need to be periodically repeated. Moreover, the current systems require handling, including mailing test kits to a laboratory, which can take days, weeks, or months depending on the test duration. Finally, adsorption temperature is not monitored or controlled, during the measurement, and it is well known that adsorption equilibrium is strongly temperature dependent. Thus, some embodiments, as discussed herein, provide active measurement for measuring gamma and beta radiation resulting from the presence of radon or other radioactive gases. The active measurement may be provided based on radon adsorption on activated carbon and the associated de-sorption. However, unlike current methods, the measurement is continuous, and device operation is fully automated and unattended, including spent-carbon regeneration. In addition, it is possible to record and monitor results on an on-going basis, either through a web-based app or any other suitable data logger. In some embodiments, a flow of air is forced through a bed of carbon material by a small pump (i.e., forced convection), thus, the measurement time is shorter than in the case where the air slowly diffuses into charcoal particles. Furthermore, it is in principle possible to eliminate or reduce gas humidity in a flow system, (e.g., by means of the appropriate drying unit placed upstream of the radon detector). Finally, the adsorption temperature is measured, and can thus be controlled and/or accounted for, so that the amount of radon detected in the carbon can be reliably related to radon concentration in the gas phase. As shown in FIG. 4, an embodiment may have a bed of activated carbon sorbent 410 where radon adsorption takes place. In some embodiments, ambient air 435 may be forced through the carbon bed 410 using a pump 440. Once the ambient air 435 moves across the carbon sorbent 410 it may then exit the system through one or more air outlets 445. In some embodiments, the temperature is monitored using a thermocouple or like device 415, and the continuous or semi-continuous radiation measurement is provided by means of a suitable ionizing radiation monitor 420 (e.g., a digital CMOS camera coupled with the GammaPix software). Additionally or alternatively, the sorbent material 410 may be enclosed in a temperature-controlled enclosure 450. In further embodiments, the saturated (e.g., partially saturated) sorbent 410 may be periodically regenerated by thermally desorbing radon into the flow of air 435. This regeneration is effected by the heating element(s) 425 and the power supply 430. In some embodiments, the entire operation may be fully automated and controlled by an information handling device (e.g., micro-computer, micro-controller, processor, etc.). Thus, as discussed herein the radon-enriched exhaust may be vented outside of the structure being monitored. Radon monitoring is generally related to homes and the sale of homes. Thus, there may be circumstances where a radon measuring device is in use while a property is occupied by individuals (e.g., homeowners, rents, potential purchasers, etc.). In order to ensure a home passes the test, a homeowner may be a tempted to move the radon-measurement device to an upper floor of the home, which typically has very low radon levels. Thus, some embodiments may include a motion sensor and/or location-monitoring equipment (e.g., accelerometers, GPS, GLONASS, iBeacon, etc.). IBEACON is a registered trademark of Apple Inc., in the United States of America and other countries. The location monitoring electronics may add protection against corrupt or incorrect measurements by detecting and storing information related to device movement. Another potential risk is that outside air may be blown (e.g., accidentally by an HVAC unit or on purpose by an individual to manipulate the test) into the space to be monitored. The addition of additional air could greatly dilute any radon adsorbed by the activated carbon sorbent, and thereby corrupt the measurement. However, as discussed herein, some embodiments may include a thermometer to measure the ambient temperature in the device. Measuring the temperature around the activated carbon may provide some protection from efforts to blow outside air into the controlled space (e.g., a basement) as such efforts will usually generate a perturbed temperature record. Accordingly, as shown in FIG. 5, embodiments as discussed herein may determine an ionizing radiation background prior to each measurement 505. In some embodiments, this process is performed when no gas-flow is occurring, immediately after the carbon bed has been regenerated. In further embodiments, the measurement is performed for a period of time sufficient to characterize the ambient radiation level to a statistically-significant degree. Once the radiation-background is determined 505, an embodiment may perform continuous ionizing radiation measurements as air flows through the sorbent bed 510. As the airflow passes through the system, the ionizing radiation and temperature data are detected and recorded. As discussed herein, these measurements may be recorded locally, or transmitted to a remote storage device (e.g., a server, smartphone, tablet, laptop, etc.). As further discussed herein, if temperature, location, and/or acceleration of the device is detected and appears erroneous, alerts or alarms may be triggered to inform a user of potential errors or tampering. In further embodiments, separate barometric pressure and humidity sensors may be used, and similar to the above, tracked rerecorded and stored (e.g., locally or remotely). Once the system described in various embodiments herein is functional for a period of time, it may be required to regenerate the sorbent. Thus, some embodiments may regenerate the sorbent by raising the internal temperature of the device 515. Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including LAN or WAN, or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. These computer readable program instructions may be provided to a processor of a computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operations steps to be performed on the computer, other programmable apparatus, or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical functions. In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. FIG. 6 is a block diagram of an example data processing system 600 in which aspects of the illustrative embodiments are implemented. Data processing system 600 is an example of a computer, such as a server or client, in which computer usable code or instructions implementing the process for illustrative embodiments of the present invention are located. In one embodiment, FIG. 6 may represent a server computing device. In the depicted example, data processing system 600 can employ a hub architecture including a north bridge and memory controller hub (NB/MCH) 601 and south bridge and input/output (I/O) controller hub (SB/ICH) 602. Processing unit 603, main memory 604, and graphics processor 605 can be connected to the NB/MCH 601. Graphics processor 605 can be connected to the NB/MCH 601 through, for example, an accelerated graphics port (AGP). In the depicted example, a network adapter 606 connects to the SB/ICH 602. An audio adapter 607, keyboard and mouse adapter 608, modem 609, read only memory (ROM) 610, hard disk drive (HDD) 611, optical drive (e.g., CD or DVD) 612, universal serial bus (USB) ports and other communication ports 613, and PCI/PCIe devices 614 may connect to the SB/ICH 602 through bus system 616. PCI/PCIe devices 614 may include Ethernet adapters, add-in cards, and PC cards for notebook computers. ROM 610 may be, for example, a flash basic input/output system (BIOS). The HDD 611 and optical drive 612 can use an integrated drive electronics (IDE) or serial advanced technology attachment (SATA) interface. A super I/O (SIO) device 615 can be connected to the SB/ICH 602. An operating system can run on processing unit 603. The operating system can coordinate and provide control of various components within the data processing system 600. As a client, the operating system can be a commercially available operating system. An object-oriented programming system, such as the Java™ programming system, may run in conjunction with the operating system and provide calls to the operating system from the object-oriented programs or applications executing on the data processing system 600. As a server, the data processing system 600 can be an IBM® eServer™ System p® running the Advanced Interactive Executive operating system or the Linux operating system. The data processing system 600 can be a symmetric multiprocessor (SMP) system that can include a plurality of processors in the processing unit 603. Alternatively, a single processor system may be employed. Instructions for the operating system, the object-oriented programming system, and applications or programs are located on storage devices, such as the HDD 611, and are loaded into the main memory 604 for execution by the processing unit 603. The processes for embodiments described herein can be performed by the processing unit 603 using computer usable program code, which can be located in a memory such as, for example, main memory 604, ROM 610, or in one or more peripheral devices. A bus system 616 can be comprised of one or more busses. The bus system 616 can be implemented using any type of communication fabric or architecture that can provide for a transfer of data between different components or devices attached to the fabric or architecture. A communication unit such as the modem 609 or the network adapter 606 can include one or more devices that can be used to transmit and receive data. Those of ordinary skill in the art will appreciate that the hardware depicted in FIG. 6 may vary depending on the implementation. Other internal hardware or peripheral devices, such as flash memory, equivalent non-volatile memory, or optical disk drives may be used in addition to or in place of the hardware depicted. Moreover, the data processing system 600 can take the form of any of a number of different data processing systems, including but not limited to, client computing devices, server computing devices, tablet computers, laptop computers, telephone or other communication devices, personal digital assistants, and the like. Essentially, data processing system 600 can be any known or later developed data processing system without architectural limitation. FIG. 7 shows a user's hand 705 with digits 710a-e. In this example, several digits (as shown, digits 710a-d) are wearing a respective smart ring assembly 720a-e. Each smart ring assembly (as shown, smart ring assembly 720a) may contain a ring portion 722a and a sensor portion 724a. FIG. 8 shows the user's human body 805. The user may be wearing one or more sensors (as shown, sensors 810a, 810b, and 810c) on various parts of the human body. For example, sensor 810a may be placed on the neck, sensor 810b may be placed on the chest, and sensor 810c may be placed on the forearm. The system and processes of the figures are not exclusive. Other systems, processes, and menus may be derived in accordance with the principles of embodiments described herein to accomplish the same objectives. It is to be understood that the embodiments and variations shown and described herein are for illustration purposes only. Modifications to the current design may be implemented by those skilled in the art, without departing from the scope of the embodiments. As described herein, the various systems, subsystems, agents, managers, and processes can be implemented using hardware components, software components, and/or combinations thereof. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” Although the invention has been described with reference to exemplary embodiments, it is not limited thereto. Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the invention and that such changes and modifications may be made without departing from the true spirit of the invention. It is therefore intended that the appended claims be construed to cover all such equivalent variations as fall within the true spirit and scope of the invention.
	description	This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-115241, filed Jun. 9, 2016; the entire content of which is incorporated herein by reference. The embodiments of the present invention relate to a core catcher and a boiling water nuclear plant using the same. The core catcher is safety equipment designed to cope with severe accidents that may occur in the nuclear plant. Even if the molten core falls through the bottom of the reactor pressure vessel onto the floor of the containment vessel of the nuclear reactor, the core catcher receives the core debris (i.e., residues of the molten core), and keeps cooling the containment vessel of the nuclear reactor, thereby preserving the safety of the containment vessel and limiting the release of radioactive substances. As the radioactive substances existing in the core debris decay, they keep generating heat that amounts to about 1% of the nuclear reactor output power. Without cooling means, the core debris may melt through the base mat concrete of the containment vessel, and a great amount of radioactive substances may be released into the environment. To prevent such an event, it is planned that a core catcher having cooling channels should be installed in the boiling water reactor (BWR). The core catcher of the European ABWR (EU-ABWR), for example, has radial cooling channels. In the cooling channels, the cooling water in the upper part of the core catcher is recirculated, efficiently removing the decay heat generated in the debris. This recirculation of cooling water is natural circulation, and does not require active pumps. Further, the cooling water can be circulated uniformly in the cooling channels because the cooling channels extend in radial directions. Taking the conventional ABWR and the conventional European ABWR (EU-ABWR) for example, the containment vessel and core catcher used in the conventional boiling water reactor (BWR) will be outlined with reference to FIG. 9 to FIG. 16. (ABWR Shown in FIG. 9) FIG. 9 is an elevational, cross-sectional view of a containment vessel of a conventional ABWR. FIG. 10 is a plan view of the containment vessel of the conventional ABWR. As shown in FIG. 9, a core 1 is provided in a reactor pressure vessel 2. The reactor pressure vessel 2 is provided in the containment vessel 3. The containment vessel 3 is shaped like a hollow cylinder (see FIG. 10). The interior of the containment vessel 3 is partitioned into a dry well 4 and a wet well 5. The dry well 4 and the wet well 5 each constitutes a part of the containment vessel 3. The wet well 5 has a suppression pool 6 in it. The suppression pool 6 has a normal water level 6a of about 7 m. The suppression pool 6 holds pool water in a large amount, about 3,600 m3. Above the suppression pool 6, a wet-well gas phase 7 is provided. The wet-well gas phase 7 is about 12.3 m high. The outer wall parts of the dry well 4 and the wet well 5 are integrated, forming the hollow cylindrical outer wall 3a of the containment vessel 3. The ceiling part of the dry well 4 is a flat plate. This part is called a top slab 4a of the dry well 4. In the case of the ABWR, the containment vessel 3 is made of reinforced concrete. Therefore, the containment vessel 3 of the ABWR is called “reinforced-concrete containment vessel (RCCV).” To make the containment vessel gastight, steel liners (not shown) are laid on the inner surfaces of the containment vessel. FIG. 9 and FIG. 10 show an example of an RCCV. As seen from FIG. 10, the outer wall 3a of the containment vessel 3 is shaped like a hollow cylinder. The bottom part of the RCCV is constituted by a part 99a of a base mat 99. The RCCV is made of reinforced concrete. The base mat 99 constitutes the bottom part of the reactor building 100. It is proposed that the base mat 99 could be made of steel concrete composite (SC composite) in the future. As shown in FIG. 9, the reactor pressure vessel 2 is supported by a hollow cylindrical pedestal 61 through a vessel skirt 62 and a vessel support 63. The pedestal 61 is constituted by a hollow cylindrical sidewall (i.e., pedestal sidewall 61a). The pedestal sidewall 61a has a thickness of, for example, 1.7 m. The pedestal sidewall 61a is made of concrete, and has inner and outer layers made of steel. The outer layer made of steel is strong enough to support, almost by itself, the weight of the reactor pressure vessel 2. The bottom of the pedestal sidewall 61a contacts the base mat 99, and is supported by the base mat 99. Below the reactor pressure vessel 2 and the vessel skirt 62 in the dry well 4, a space is formed, surrounded by the hollow cylindrical pedestal sidewall 61a and the part 99a of the base mat 99. This space is called pedestal cavity 61b. In the RCCV of the ABWR, the pedestal sidewall 61a constitutes a boundary wall between the wet well 5 and the dry well 4. Particularly, the space of the pedestal cavity 61b is called lower dry well 4b. The height from the floor of this lower dry well 4b to the bottom of the reactor pressure vessel 2 is about 11.55 m. The upper space in the dry well 4, excluding the lower dry well 4b, is called upper dry well 4c. (Lower Dry Well Part Shown in FIG. 11) FIG. 11 is an enlarged view of the lower dry well (lower DW) 4b and peripherals. On the bottom of the lower dry well 4b, a concrete floor 67 is provided, having a thickness of about 1.6 m. The concrete floor 67 has sumps 68. The sumps 68 have a depth of about 1.3 m. The sumps 68 are configured to collect leakage water therein if the coolant leaks from the pipes or components connected to the reactor pressure vessel 2. The water levels in the sumps 68 are monitored in order to detect the leakage. Two sumps 68, a high conductivity waste sump 68a and a low conductivity waste sump 68b, are provided (see FIG. 10), but only one sump is shown in FIG. 9 and FIG. 11. Each sump 68 has a corium shield (i.e., a lid for preventing inflow of debris; not illustrated), which prevents the in-flow of core debris in case a severe accident occurs. Various types of corium shields have been devised, one of which is disclosed in Japanese Patent Application Laid-Open Publication 2015-190876, the entire content of which is incorporated by reference. In the lower dry well 4b, there are provided control rod drives 10 and a control rod drive handling equipment 11. The control rod drives 10 are connected to the bottom of the reactor pressure vessel 2. The control rod drive handling equipment 11 is arranged below the control rod drive 10. About 205 control rod drives 10 are used in all. The control rod drive handling equipment 11 takes the control rod drives 10, one by one, from the reactor pressure vessel 2, rotates each control rod drive 10 to a horizontal position and moves up the same again, so that the control rod drives 10 may be carried out of the containment vessel. The control rod drive handling equipment 11 is therefore indispensable for the maintenance of the nuclear reactor. The control rod drive handling equipment 11 can rotate, in its entirety, in the horizontal direction to be positioned with respect to each of the all control rod drives 10. This is why the upper surface of the control rod drive handling equipment 11 is also called a turntable 11a. The control rod drive handling equipment 11 has a height of about 4.6 m, and can hold the control rod drives 10 in it. On the turntable 11a operators may stand to perform maintenance work. Therefore, the lower ends of the control rod drives 10 are spaced from the turntable 11a by about 2.2 m. On the other hand, the lower end of the control rod drive handling equipment 11 is spaced away from the concrete floor 67 by about 10 cm only. Thus, a gap is scarcely provided between the concrete floor 67 and the lower end of the control rod drive handling equipment 11. The lower end of the control rod drive handling equipment 11 is about 1.7 m above the upper end of the part 99b of the base mat 99. The upper surface of the concrete floor 67 is about 1.6 m above the upper end of the part 99b of the base mat 99. No space is therefore available to arrange the core catcher, and the core catcher is not arranged there. In the conventional ABWR, the lower dry well 4b holds the control rod drives 10 and the control rod drive handling equipment 11, and cannot accommodate a core catcher. It is proposed that the lower dry well 4b should be used as a space for the core catcher and the device (i.e., hopper) associated with the core catcher (see, for example, Patent Application Laid-Open Publication 2008-241657, the entire content of which is incorporated by reference). In practice, however, the lower dry well 4b of the conventional ABWR has no extra clearance, and a core catcher (disclosed in Patent Application Laid-Open Publication 2008-241657) cannot be arranged there. The size and shape of the containment vessel of the conventional ABWR are standardized as described above. The height from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a (i.e., total height of the containment vessel 3) is about 29.5 m. The dry well 4 and the suppression pool 6 are connected by LOCA vent pipes 8. Ten LOCA vent pipes 8, for example, are arranged (see FIG. 10), though only two LOCA vent pipes are shown in FIG. 9 and FIG. 11. Each of the LOCA vent pipes 8 has a plurality of horizontal vent pipes 8a submerged in the pool water and has openings in the pool water. In the case of the RCCV, three horizontal vent pipes 8a are provided for each of the LOCA vent pipes 8 and extend in the vertical direction. The uppermost horizontal vent pipe has its upper end located at the height of about 3.85 m from the part 99b of the base mat 99. If an accident occurs, the suppression pool 6 is used as water source for the safety system such as an emergency core cooling system. Even in such a case, the pool keeps holding water in such an amount that the water level never falls below the level of about 0.61 m to 1.0 m higher than the upper end of the uppermost horizontal vent pipe 8a. This measure is taken in order that the horizontal vent pipe 8a can keep a condensation function. Hence, in the event of an accident, the water in the suppression pool 6 can be maintained at a level of about 4.46 m to 4.85 m at the lowest. In the RCCV, the LOCA vent pipes 8 are arranged, extending in the interior of the pedestal sidewall 61a shaped like a hollow cylinder. The pedestal sidewall 61a is therefore called “vent wall 61c” if used in the case of the RCCV. As specified above, the vent wall 61c is about 1.7 m thick and made of concrete, and its inner and outer layers are made of steel. The outer layer made of steel can support, by itself, the weight of the reactor pressure vessel 2. The concrete part of the vent wall 61c reinforces the pedestal 61 and has the function of holding the LOCA vent pipes 8. The LOCA vent pipes 8 and the pedestal 61 constitute a part of the containment vessel 3. One of the methods of maintaining, in the suppression pool 6, water much enough to keep the water temperature low to cope with a severe accident is to supply water to the pool from an external water source. Various means (not shown) are available for supplying water to the suppression pool, such as a portable pump, a fire-fighting pump and an alternate water supply pump. The design pressure of the containment vessel 3 is about 3.16 kg/cm2 (0.310 MPa in terms of gauge pressure). The hollow cylindrical outer wall 3a and the top slab 4a are made of reinforced concrete and have thickness of about 2 m and a thickness of about 2.4 m, respectively. Their inner surfaces are lined with steel liners (not shown) for the purpose of limiting the leakage of radioactive substances. The base mat 99 has a thickness of about 5 m and is made of reinforced concrete, too. The containment vessel 3 has a design leakage rate of about 0.4% per day. Recently it is proposed that the hollow cylindrical outer wall 3a and the top slab 4a of the containment vessel 3 could be made of steel concrete composite (SC composite), not reinforced concrete. The SC composite comprises two steel frames secured to each other with ribs and concrete filled in the gap between the steel frames. The SC composite is advantageous in that rebars need not be laid and that it can be modularly assembled. Further, as the SC composite is stronger, raising the design pressure of the containment vessel 3 even higher is possible. An example of employing an SC composite in nuclear plants is the shield building of the AP1000 (registered trademark) of Westinghouse, Inc. (EU-ABWR Shown in FIGS. 12 and 13) How an EU-ABWR core catcher is installed will be explained with reference to FIG. 12 and FIG. 13. FIG. 13 is an enlarged view of the lower dry well 4b. As shown in FIG. 12 and FIG. 13, a core catcher 30 is mounted on the part 99b of the base mat 99 provided at the lower part of the lower dry well 4b. The core catcher 30 is arranged eliminating the concrete floor 67 (FIG. 9 and FIG. 11) about 1.6 m thick provided in the conventional ABWR. Further, in the EU-ABWR, the lower dry well 4b is about 2.1 m higher than in the ordinary ABWR, and the space for the core catcher 30 has a height of about 3.7 in including the thickness of the eliminated concrete floor, i.e., 1.6 m. The core catcher 30 has height of about 2.45 m. Furthermore, a lid 31 is arranged above the core catcher 30. The upper end of the lid 31 lies about 3.6 m above the upper end of the base mat 99. The lid 31 has a sump 68. The sump 68 is about 1.3 m deep. The lid 31 is positioned so high that the sump 68 does not interfere with the core catcher 30. The lower end of the control rod drive handling equipment 11 is located about 3.7 m from the upper end of the base mat 99. Hence, the core catcher 30 having a height of about 2.45 m can be arranged together with the lid 31 having a height of about 3.6 m. (Fusible Valve) In the pedestal cavity 61b, fusible valves 64 and lower dry well flooding pipes 65 are provided to cope with a core meltdown that might occur. The lower dry well flooding pipes 65 extend from the LOCA vent pipes 8, penetrate the pedestal sidewall 61a and are connected to the fusible valve 64. One fusible valve 64 and one lower dry well flooding pipe 65 are provided on each of the LOCA vent pipes 8. Each fusible valve 64 has a plug part made of low-melting-point material, and opens by melting the plug part if the temperature in the lower dry well 4b rises to about 260 degrees centigrade. If a core meltdown occurs, the corium melts through the bottom of the reactor pressure vessel 2, falls down into the pedestal cavity 61b, melts through the control rod drive handling equipment 11, and is held in the core catcher 30 provided at the bottom of the pedestal cavity 61b. Accordingly, as the temperature abruptly rises in the pedestal cavity 61b, the fusible valves 64 open. The cooling water in the LOCA vent pipes 8 then flows through the lower dry well flooding pipes 65 into the pedestal cavity 61b, flooding and cooling the corium on the core catcher 30. The cooled corium partly becomes solidified core debris. The cooling water in the LOCA vent pipes 8 are supplied from the suppression pool 6 through the horizontal vent pipes 8a. The configuration of the core catcher of the conventional EU-ABWR will be described with reference to FIG. 14 to FIG. 16. FIG. 14 is a sectional view showing the configuration of the core catcher of the conventional EU-ABWR. FIG. 15 is a plan view showing the configuration of the core catcher of the conventional EU-ABWR. FIG. 16 is a perspective view of one of the cooling channels used in the core catcher of the conventional EU-ABWR. (Configuration of FIG. 14) As shown in FIG. 14, the core catcher 30 is provided on the bottom of the lower dry well 4b surrounded by the pedestal sidewall 61a and the part 99b of the base mat 99. The core catcher 30 is constituted by a dish-shaped basin 32. The basin 32 is made of steel and has a thickness of about 1 cm. In some cases, the thickness of the basin 32 may be about 5 cm, about 10 cm, or the like, depending on the strength the basin 32 must have. A refractory layer 33 is laid on the basin 32, and a sacrificial layer 34 is laid on the refractory layer 33. The refractory layer 33 is composed of refractory bricks glued together, and has a thickness of about 17.5 cm. The refractory bricks may be made of alumina (aluminum oxide) and zirconia (zirconium oxide). The sacrificial layer 34 is made of concrete and has thickness of about 5 cm. If core debris falls on to it, the sacrificial layer 34 is eroded with the heat of the core debris, preventing the refractory layer 33 from being heated over the allowable temperature, until the cooling water is supplied from the fusible valve 64 and starts cooling the core debris. The peripheral part of the basin 32 is connected to a circular annular riser sidewall 38a having an axis extending in the vertical direction. Around the riser sidewall 38a, a circular annular downcomer sidewall 39a is provided and spaced from the riser sidewall 38a by about 10 cm. The upper edge of the downcomer sidewall 39a lies at a height of about 2.45 m from the upper end of the part 99b of the base mat 99. The lid 31 is provided above the core catcher 30. The lid 31 lies at a height of about 3.6 m above the part 99b of the base mat 99. The lid 31 is configured to fall onto the sacrificial layer 34 immediately if the molten core falls from above. Thereafter, the lid 31 melts due to the high temperature of the core debris and becomes part of the debris. Below the basin 32, many radial cooling channels 35 are provided (see FIG. 15). The cooling channels 35 incline at about 10 degrees. The cooling channels 35 have a length of about 4 m. The cooling channels 35 are defined by many channel sidewalls (ribs) 35a provided below the basin 32 (see FIG. 15 and FIG. 16). The number of cooling channels 35 used is, for example, 16, and may be changed as needed. The channel sidewalls 35a perform the function of cooling fins and ribs supporting the basin 32. The channel sidewalls 35a are made of metal having high thermal conductivity, such as steel or copper. A distributor 36 shaped like a hollow cylinder and having a vertical axis is provided at the center of the radial cooling channels 35. The diameter of the distributor 36 is, for example, about 2 m. The diameter of the distributor 36 may be changed if necessary. To the distributor 36, the channel inlets 35b of the cooling channels 35 are connected. The cooling water can therefore be uniformly supplied to all cooling channels 35 from the distributor 36. The lower end of the distributor 36 is closed by a bottom plate 36a. The bottom plate 36a contacts the part 99b of the base mat 99. In the distributor 36, a distributor pillar 36b is provided as shown in FIG. 14. Alternatively, two or more distributor pillars may be provided as needed. The distributor pillar 36b contacts the basin 32, whereby the distributor 36 bears a part of the weight of the basin 32. The outlet ports of the radial cooling channels 35 are connected to a riser 38 that guides the cooling water upward in the vertical direction. The riser 38 is a flow passage provided between the riser sidewall 38a and the downcomer sidewall 39a, and has a width of about 10 cm. The upper end of the riser 38, i.e., riser outlet 38b, opens in the upper part of the core catcher 30. The cooling water rises in the riser 38 and flows through the riser outlet 38b into the upper part of the core catcher 30. Further, a circular annular downcomer 39 is provided, surrounding the riser 38. The downcomer 39 is a flow passage provided between the downcomer sidewall 39a and the pedestal sidewall 61a and has a width of about 30 cm. The upper end of the downcomer 39 opens in the upper part of the core catcher 30. The downcomer 39 extends down to the bottom of the lower dry well 4b and is connected to the cooling-water inlet ports 37a of cooling water injection pipes 37. Each of the cooling water injection pipes 37 has a cooling-water outlet port 37b, which is connected to the sidewall 36c of the distributor 36. In the configuration described above, the cooling water accumulated in the upper part of the core catcher 30 flows down again in the downcomer 39, reaches the distributor 36 through the cooling water injection pipes 37, and is used in the cooling channels 35. Thus, the cooling water in the upper part of the core catcher 30 is circulated again by the downcomer 39. The basin 32, the cooling channels 35, the distributor 36 and the cooling water injection pipes 37 are made watertight, and the cooling water would not leak from them. If the fusible valves 64 are melted with the heat generated in the core debris, the cooling water that floods the core debris existing above the basin 32 and cools the core debris is supplied from the LOCA vent pipes 8 through the lower dry well flooding pipes 65. Until the core debris becomes flooded by the cooling water, the sacrificial layer 34 protects the refractory layer 33 and the basin 32 from overheating, while the sacrificial layer 34 is melting. The main body 30a of the core catcher 30 is composed of the basin 32, the distributor 36, the cooling channels 35 and the riser 38. The refractory layer 33 and the sacrificial layer 34 have the function of protecting the main body 30a of the core catcher 30. The downcomer 39 and the cooling water injection pipes 37 have the function of circulating the cooling water and supplying the cooling water to the main body 30a. (Configuration of FIG. 15) FIG. 15 is a plan view of the core catcher used in the conventional EU-ABWR, specifying the positions of the cooling channels 35 of the core catcher. As shown in FIG. 15, the cooling channels 35 extend from the distributor 36 in radial directions. The cooling channels 35 are partitioned, one from another, by the channel sidewalls (ribs) 35a. Each channel sidewall 35a has an opening (not shown). In some case, the cooling water can flow from one cooling channel to another through the opening made in the channel sidewall 35a. More channel sidewalls (ribs) 35a may be provided in order to strengthen the peripheral part of the core catcher and to increase the number of heat transfer fins (see U.S. Pat. No. 8,358,732, the entire content of which is incorporated by reference). (Configuration of FIG. 16) FIG. 16 is a perspective view illustrating the configuration of the cooling channels 35 used in the core catcher of the conventional EU-ABWR. In FIG. 16, the thicknesses of the walls are not shown. Each cooling channel 35 is composed of a part 32a of the basin 32, a channel sidewall 35a, and a channel bottom wall 35c, and is shaped like a fan. The cooling channel 35 inclines, gradually upward to the outer circumference. The angle of inclination is about 10 degrees. The channel inlet 35b of the cooling channel 35 is connected to the sidewall 36c of the distributor 36. The other end of the cooling channel 35 is connected to the riser 38. The riser 38 is composed of a riser sidewall 38a, a riser rib 38c, and a downcomer sidewall 39a. The cooling water flows into the cooling channels 35 through the channel inlets 35b, is heated with the heat generated by the core debris, rises in the riser 38, and flows into the upper part of the core catcher 30 through the riser outlet 38b. Thereafter, again, the cooling water flows down through the downcomer 39, then flows from the cooling-water inlet port 37a into the cooling water injection pipe 37, and further flows from the cooling-water outlet port 37b into the distributor 36 (see FIG. 14 and FIG. 15). The cooling water supplied into the distributor 36 is circulated again in the cooling channels 35. The drive force recirculating the cooling water results from the water head of the cooling water in the downcomer 39, which is about 2.45 m high. In order to acquire this drive force, the core catcher of the conventional EU-ABWR has a height of about 2.45 m except the lid 31. The space below the channel bottom wall 35c is filled with concrete, embedding the cooling water injection pipe 37 therein. The channel bottom wall 35c can thereby withstand the load applied to the cooling channel 35. In some cases, a support member such as a rib may be used to support the channel bottom wall 35c, instead of filling the space with concrete. (Disadvantages of the Prior Art) In the containment vessel 3 of the EU-ABWR, the lower dry well 4b has a height about 2.1 m greater than the value used in the conventional ABWR. Hence, the levels of the reactor pressure vessel 2 and the core 1 are about 2.1 m higher than the conventional ABWR. This reduces the seismic resistance. The reduction of seismic resistance is not so problematic in, for example, Europe where earthquakes are not severe, but should be avoided in a country, such as Japan, which suffers from severe earthquakes. Further, the total height of the containment vessel 3 increases by about 2.1 m, and the total height of the reactor building 100 increases by about 2.1 m, too. This increases the amount of concrete used and worsens the economy. The containment vessel 3 of the EU-ABWR has a total height of about 31.6 m, from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a. Accordingly, the core catcher 30 influences not only the lower dry well 4b, but also the entire plant including the containment vessel 3 and the reactor building 100. One of the methods of avoiding such a problem is to dig down the part 99b of the base mat 99, i.e., bottom of the lower dry well 4b, by about 2.1 m and put the core catcher 30 therein. The rebars that have been arranged in the conventional part 99b of the base mat 99, that is digged down, are to be cut and removed. In this case, however, the configuration of the base mat 99 becomes complicated, causing longer construction time and reducing the strength of the base mat 99 against earthquakes. In the containment vessel 3 of the conventional ABWR, the height of the lower dry well 4b is not increased about 2.1 m, unlike in the EU-ABWR. In view of the construction schedule and the structure strength, it is undesirable to dig down the part 99b of the base mat 99. Hence, if a gap of about 10 cm is secured between the core catcher 30 and the lower end of the control rod drive handling equipment 11, the height of the space for accommodating the core catcher 30 is limited to about 1.6 m, because this space is provided by removing a part of the concrete floor 67. As described above, the core catcher 30 of the EU-ABWR is about 2.45 m high and the upper end of the lid 31 is about 3.6 m high. Consequently, the core catcher 30 cannot be disposed in the ABWR core catcher space having a height of about 1.6 m. The core catcher 30 can be disposed in the ABWR core catcher space about 1.6 m high if the cooling channels 35 are inclined less, thereby reducing the thickness of the basin 32 and the height of the distributor 36 is also reduced, and so on. In such a case, however, the height of the downcomer 39 decreases from about 2.45 m to about 1.6 m. The height of the downcomer 39 determines the water head that is the drive force for circulating the water in the upper part of the core catcher 30 in the cooling water injection pipes 37, the distributor 36, the cooling channels 35 and the risers 38. Therefore, if the height of the downcomer 39 decreases to about 1.6 m, the flow rate of the cooling water flowing in the radial cooling channels 35 inevitably decreases, and the decay heat generated in the core debris cannot be sufficiently removed. The flow rate of recirculating the cooling water in the upper part of the core catcher 30 by the downcomer 39 is determined by the density difference between the cooling water in the radial cooling channels 35 and the riser 38, and the cooling water in the downcomer 39. The lower the temperature of the cooling water in the upper part of the core catcher 30 flowing into the downcomer 39, the larger the density difference will be. Generally speaking, however, the upper part of the core catcher 30 holds the hottest core debris, which heats the cooling water. It is therefore physically difficult to keep the cooling water flowing into the downcomer 39 at low temperature. Accordingly, the cooling water in the upper part of the core catcher 30 is heated to a high temperature as time passes, though it remains at low temperature immediately after the core debris has fallen. Consequently, there is a problem that the heated cooling water will impede a sufficient natural circulation flow rate. Since the cooling water recirculated by the downcomer 39 contacts the core debris existing in the upper part of the core catcher 30, part of the core debris may be released, flow into the downcomer 39 and move to the lower part of the core catcher 30. If this happens, the core catcher 30 would lose the function of holding and cooling the core debris. To prevent this, a filter is arranged in the opening made in the downcomer 39. The filter may be clogged with the loose parts scattered in the event of a severe accident. The core debris may melt through the bottom of the reactor pressure vessel 2, and may then fall onto the upper part of the core catcher 30. Accordingly in this process, the thermal insulators and such might become loose parts. Once the filter has been clogged with the loose parts, the cooling water may not be recirculated in a sufficient flow rate. In the conventional core catcher 30, the cooling water does not exist in the cooling channels 35 during the normal operation of the plant. If the core debris falls, raising the temperature in the lower dry well 4b and melting the fusible valves 64, the water in the LOCA vent pipes 8 submerges the core catcher 30 and the core debris, flows down in the downcomer 39, passes through the cooling water injection pipe 37 and distributor 36, and cools the cooling channels 35. Therefore, there is a time lag after the falling of the core debris until the cooling channels 35 start cooling the basin 32. During this time lag, the sacrificial layer 34 and the refractory layer 33 prevent the overheating of the basin 32. However, if the impact of the falling core debris damages the sacrificial layer 34 and the refractory layer 33, the core debris may contact the basin 32 directly and may melt a part of the basin 32. An object of the present embodiments is to provide a thin core catcher which has a main body about 1.6 m or less high and can be arranged in a lower dry well of a conventional ABWR without interfering with the control rod drive handling equipment. Another object of the present embodiments is to provide a core catcher which keeps cooling water in the cooling channels during normal operation and enables cooling channels to achieve cooling immediately if a sever accident occurred and core debris fell onto it. Yet another object of the present embodiments is to provide a thin core catcher which can, despite its small thickness, preserve the flow rate of cooling water flowing in the cooling channels by means of natural circulation. Yet another object of the present embodiments is to provide a core catcher in which the cooling water on the upper surface is not recirculated in the cooling channels, preventing the core debris and loose parts from flowing into the cooling channels. According to an embodiment, there is presented a core catcher for use in a boiling water nuclear plant which has: a base mat; a reactor building built on a part of the base mat; a containment vessel provided in the reactor building, built on the base mat and having a total height of not exceeding 29.5 m to a lower end of a top slab; a core; a reactor pressure vessel holding the core; a dry well constituting a part of the containment vessel and holding the reactor pressure vessel; a pedestal connected to the base mat and supporting the reactor pressure vessel through a vessel skirt and a vessel support; a wet well constituting a part of the containment vessel, the wet well being provided around the pedestal, holding a suppression pool in a lower part thereof, and having a wet well gas phase at an upper part thereof; LOCA vent pipes provided in a sidewall of the pedestal and connecting the dry well to the suppression pool; a lower dry well which is a space in the dry well, is located below the vessel skirt and the reactor pressure vessel and is surrounded by the sidewall of the hollow cylindrical pedestal and the part of the base mat, which lies inside the sidewall of the pedestal; control rod drives provided in the lower dry well and connected to a lower part of the reactor pressure vessel; and a control rod drive handling equipment provided in the lower dry well and below the control rod drives; the core catcher comprising: a main body including: a distributor arranged on the part of the base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin, having inlets connected to the distributor and extending in radial directions, and a riser connected to outlets of the cooling channels and extending upward in vertical direction; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, penetrating the sidewall of the pedestal, connected at another end to the distributor, and configured to supply pool water to the distributor; and chimney pipes connected, at one end, to the riser, penetrating the sidewall of the pedestal, another end being located above the upper end of the riser and submerged and open in the pool water at a level lower than a minimum water level at a time of an accident, wherein the upper ends of the main body and the lid are at heights lower than lower end of the control rod drive handling equipment, as measured from upper end of the base mat. According to another embodiment, there is presented a boiling water nuclear power plant comprising: a base mat; a reactor building built on a part of the base mat; a containment vessel provided in the reactor building, built on the base mat and having a total height of not exceeding 29.5 m to a lower end of a top slab; a core; a reactor pressure vessel holding the core; a dry well constituting a part of the containment vessel and holding the reactor pressure vessel; a pedestal connected to the base mat and supporting the reactor pressure vessel through a vessel skirt and a vessel support; a wet well constituting a part of the containment vessel, the wet well being provided around the pedestal, holding a suppression pool in a lower part thereof, and having a wet well gas phase at an upper part thereof; LOCA vent pipes provided in a sidewall of the pedestal and connecting the dry well to the suppression pool; a lower dry well which is a space in the dry well, is located below the vessel skirt and the reactor pressure vessel and is surrounded by the sidewall of the hollow cylindrical pedestal and the part of the base mat, which lies inside the sidewall of the pedestal; control rod drives provided in the lower dry well and connected to a lower part of the reactor pressure vessel; a control rod drive handling equipment provided in the lower dry well and below the control rod drives; and a core catcher having: a main body including: a distributor arranged on the part of the base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin, having inlets connected to the distributor and extending in radial directions, and a riser connected to outlets of the cooling channels and extending upward in vertical direction; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, penetrating the sidewall of the pedestal, connected at another end to the distributor, and configured to supply pool water to the distributor; and chimney pipes connected, at one end, to the riser, penetrating the sidewall of the pedestal, another end being located above the upper end of the riser and submerged and open in the pool water at a level lower than a minimum water level at a time of an accident, wherein the upper ends of the main body and the lid are at heights lower than lower end of the control rod drive handling equipment, as measured from upper end of the base mat. A first embodiment of the present invention will be described with reference to FIG. 1 to FIG. 6. Any components identical to ones shown in FIG. 9 to FIG. 16 are identified by the same numbers in FIG. 1 to FIG. 6, and will not be described repeatedly in the following description. (Configuration of FIGS. 1 and 2) FIG. 1 is a sectional view illustrating a situation where a core catcher according to the present invention is arranged in the containment vessel of an ordinary type ABWR. FIG. 2 is an enlarged view showing the position the core catcher takes in the lower dry well 4b of the containment vessel 3. In FIG. 1 and FIG. 2, the main body 30a of the core catcher 30 has a height of no more than about 1.6 m. The main body 30a of the core catcher 30 is arranged in a space provided by removing that part of a concrete floor 67 (see FIG. 11) having a height of about 1.6 m, at the bottom of the lower dry well 4b of the ABWR containment vessel 3. Therefore, none of the heights of the lower dry well 4b, the containment vessel 3 and the reactor building 100 are increased by about 2.1 in, unlike in the EU-ABWR. The total height of the containment vessel 3 is about 29.5 m, from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a. The main body 30a of the core catcher 30 is provided below a control rod drive handling equipment 11 (about 1.7 m high), not contacting the lower end of the control rod drive handling equipment 11. A lid 31 is arranged also below the control rod drive handling equipment 11 (about 1.7 m high), not contacting the lower end of the control rod drive handling equipment 11. The upper end of the main body 30a of the core catcher 30 and the upper end of the lid 31 are below a height of 1.7 m from the upper end of the part 99b of the base mat 99. (Configuration of FIG. 3) The first embodiment of the present invention will be described with reference to FIG. 3 to FIG. 6. As shown in FIG. 3, the main body 30a of the core catcher 30 according to this embodiment includes a basin 32, a distributor 36, cooling channels 35 and a riser 38. This embodiment differs from the prior-art apparatus in several respects. First, the cooling channels 35 are inclined by, for example, 5 degrees (not 10 degrees as in the prior-art apparatus), and the main body 30a of the core catcher 30 is thin, having the total height of no more than about 1.6 m that is less than the height (1.7 m) of the control rod drive handling equipment 11. Second, the lid 31 is provided, contacting the upper end of the main body 30a of the core catcher 30 (i.e., the upper end of the riser 38). Third, the lid 31 is provided with no sumps. Fourth, no downcomers are provided. Fifth, the cooling water injection pipe 37 penetrates the vent wall 61c, and its distal end opens in the water in the suppression pool 6. Sixth, the upper end of the riser 38 is closed, not open to the upper part of the core catcher 30. Seventh, a chimney pipe 40 is provided and connected at one end to the riser 38. Eighth, the chimney pipe 40 penetrates the vent wall 61c, and its distal end opens in the water in the suppression pool 6. Finally, the chimney pipe 40 extends upward to a position higher than the riser 38. The chimney pipe 40 has an opening 40a in the suppression pool 6, at a height which is higher than the height (i.e., about 2.45 m) of the downcomer 39 of the core catcher 30 used in the conventional EU-ABWR and which is lower than the minimum water level (i.e., about 4.46 m to 4.85 m) in the suppression pool 6 in the event of an accident. For example, the upper end of the chimney pipe 40 may lie at a height of about 4 m. The cooling channels may be identical in structure to those shown in, for example, FIG. 16. (Configuration of FIG. 4) FIG. 4 is a plan view of a first embodiment of the core catcher according to the present invention. In FIG. 4, the cooling channels 35 are shown as exposed, but none of the lid 31, the sacrificial layer 34 made of concrete, the refractory layer 33 composed of refractory bricks and the basin 32 made of steel plate are not illustrated. As shown in FIG. 4, the number of cooling channels 35 provided is, for example, 10, and the number of LOCA vent pipes 8 used is, for example, 10. The number of the cooling channels 35 is not limited to 10, nevertheless. If eight LOCA vent pipes 8 are used, 8, 16 or 32 cooling channels 35 may be used in accordance with the cooling ability and structural strength that are desired. The chimney pipes 40 are positioned, not interfering with the LOCA vent pipes 8. In the configuration of FIG. 4, for example, each chimney pipe 40 is provided between two adjacent LOCA vent pipes 8. The chimney pipes 40 are arranged in the vent wall 61c (see FIG. 3). In the embodiment configured as described above, the cooling water injection pipes 37, the distributor 36, the cooling channels 35, the riser 38 and the chimney pipes 40 are kept communicated with the suppression pool 6 at all times, and always filled with the pool water of the suppression pool 6. During an accident, the pool water is supplied into the cooling channels 35 by virtue of the density difference between the water in the suppression pool 6 and the cooling water flowing in the cooling channels 35, the riser 38 and the chimney pipes 40. The chimney pipes 40 have an opening 40a at a height of about 4 m. Therefore, in each chimney pipe 40 up to about 4 m, exists low density cooling water heated to high temperature by the decay heat of the core debris. The water is vaporized, generating a two phase flow in each chimney pipe 40 in some cases. On the other hand, low-temperature, high-density water exists in the suppression pool 6 to a height of about 4 m. By virtue of the density difference between the respective water, the cooling water can be supplied into the cooling water injection pipe 37. The water head in the suppression pool 6 is about 4 m, much higher than the water head of about 2.45 m in the downcomer 39 of the conventional EU-ABWR core catcher. Therefore, much larger natural circulation flow rate can be obtained. The suppression pool 6 contains a large amount of pool water and can keep low temperature and high density of cooling water. Therefore, the large natural circulation flow rate can be maintained owing to the large density difference. A method for maintaining water at low temperature in the suppression pool 6 for a long time in the event of a severe accident may be to supply water from an external water source to the suppression pool 6, or to supply condensate from a passive containment cooling system to the suppression pool 6 (refer to WO2016/002224, the entire content of which is incorporated by reference). In the conventional core catcher 30, the density difference decreases because the downcomer 39 supplies the low-density, high-temperature water heated by the core debris above the basin 32. Consequently, it was difficult to keep a large flow rate of natural circulation. This problem can be solved in this embodiment. Further, the core catcher of the embodiment does not use for recirculation the contaminated water existing above the basin 32 that might contain some core debris and loose parts. Hence, it is possible to eliminate the possibility of loss of cooling function due to the clogging of the cooling channels 35 and so on. Furthermore, since the water is constantly supplied from the suppression pool 6 into the cooling channels 35 during the normal operation, the cooling of the basin 32 can be immediately started in an accident, even if the sacrificial layer 34 and the refractory layer 33 are damaged by an impact of core debris drop. Once the temperature of the basin 32 rises, the cooling water existing in the cooling channels 35 before the accident starts cooling the basin 32 naturally, and the cooling water is stably supplied thereafter by virtue of natural circulation. Thanks to the above cooling mechanism, the sacrificial layer 34 and the refractory layer 33 may be eliminated in the core catcher of this embodiment. The core debris existing above the core catcher 30 is cooled with the cooling water supplied from the lower dry well flooding pipes 65 through the fusible valves 64 that have been melted open (see FIG. 14). Since the chimney pipes 40 provide a water head of, for example, 4 m, the heights of the basin 32 and the riser 38 need not be increased. The main body 30a of the core catcher 30 can therefore be thin (or low in height). Hence, it is possible to provide a core catcher that can be arranged in the space with about 1.6 m height at the bottom of the lower dry well 4b, where is the only available space for the conventional ABWR to install a core catcher. Variations of the first embodiment of the present invention will be described with reference to FIG. 5 and FIG. 6. (Configuration of FIG. 5) As shown in FIG. 5, the chimney pipes 40 penetrate the pedestal sidewall 61a, each extending upward and slantwise. So shaped, the chimney pipes 40 have no elbow parts, reducing the flow resistance and increasing the natural flow rate of the cooling water. Alternatively, the chimney pipes 40 can have a smaller diameter for the same reason. (Configuration of FIG. 6) As shown in FIG. 6, the chimney pipes 40 penetrate the pedestal sidewall 61a in horizontal direction and then extend upward in the suppression pool 6. So shaped, the chimney pipes 40 have less elbow parts than otherwise. In addition, as they do not extend upward in the pedestal sidewall 61a the chimney pipes 40 can be installed more easily. A second embodiment of the core catcher according to the present invention will be described with reference to FIG. 7 and FIG. 8. (Configuration of FIG. 7) FIG. 7 is a plan view outlining the second embodiment of the core catcher according to the present invention. As shown in FIG. 7, two sumps 68, i.e., a high conductivity waste sump 68a and a low conductivity waste sump 68b, are arranged. In the vicinity of the sumps 68, a lid 31, a basin 32, a refractory layer 33, a sacrificial layer 34, cooling channels 35, channel sidewalls 35a, a riser 38, and chimney pipes 40 are configured to avoid interference with the sumps 68a and 68b and surround the peripheries of the sumps 68. The sumps 68a and 68b have a corium shield (not shown) each. In this embodiment, the core catcher 30 can be arranged without interfering with the sumps 68a and 68b. (Configuration of FIG. 8) FIG. 8 is an elevational sectional view outlining the second embodiment of the core catcher according to the present invention. A sump riser 38d, a sump refractory layer 33a, and a sump sacrificial layer 34a are arranged along the sidewall of the sump 68. The core catcher 30 can therefore be arranged without interfering with the sumps 68a and 68b. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
	claims	1. A system for containing high level radioactive materials comprising:a cask extending along a longitudinal axis and having an internal cavity for holding high level radioactive materials, the cask comprising at least one inlet vent at a bottom end of the cask for allowing cool air to enter the internal cavity and at least one outlet vent at a top end of the cask for allowing heated air to exit the internal cavity;a tubular shell extending from a bottom end to a top end, the tubular shell positioned to circumferentially surround the cask in a spaced apart manner so that an annular gap exists between the tubular shell and a sidewall of the cask, the tubular shell comprising at least one primary aperture forming a passageway through the tubular shell and at least one secondary aperture forming a passageway through the tubular shell; andan air flow barrier extending between the tubular shell and the sidewall of the cask that separates the annular gap into: (1) a first chamber that forms a passageway between the primary aperture and the inlet vent of the cask; and (2) a second chamber that forms a passageway between the secondary aperture and an opening at the top end of the tubular shell, wherein cross-flow of air between the first and second chambers of the annular gap is prohibited by the air flow barrier,wherein the primary aperture is configured as a first air flow inlet for the first chamber, for air to flow into the primary aperture, through the first chamber, and to the inlet vent of the cask, the primary aperture being located at an axial height below the air flow barrier, andwherein the secondary aperture is configured as a second air flow inlet for the second chamber, for air to flow into the secondary aperture, through the second chamber, and to the opening at the top end of the tubular shell, the secondary aperture being located at an axial height above the air flow barrier. 2. The system of claim 1 wherein the air flow barrier is an annular plate that separates the annular gap into an upper chamber and a lower chamber. 3. The system of claim 2 wherein the tubular shell comprises a plurality of the primary apertures circumferentially arranged in a spaced-apart manner about the tubular shell and a plurality of the secondary apertures circumferentially arranged in a spaced-apart manner about the tubular shell, wherein the secondary apertures are located at an axial height above the air flow barrier and the primary apertures are located at an axial height below the air flow barrier. 4. The system of claim 3 wherein the primary apertures are notches in a bottom edge of the tubular shell. 5. The system of claim 1 wherein the inlet vent comprises an inlet opening in the sidewall of the cask, the primary aperture of the tubular shell being radially offset from the inlet opening of the inlet vent. 6. The system of claim 1 further comprising:the tubular shell comprising a plurality of the primary apertures circumferentially arranged in a spaced-apart manner about the tubular shell;the cask comprising a plurality of inlet vents, each of the inlet vents comprising an inlet opening in the sidewall of the cask, the inlet openings of the inlet vents circumferentially arranged in a spaced-apart manner about the bottom end of the cask; andwherein the inlet openings of the inlet vents are radially offset from the primary apertures of the tubular shell. 7. The system of claim 6 wherein the inlet openings are notches formed in a bottom edge of the tubular shell. 8. The system of claim 6 wherein the tubular shell comprises a plurality of the secondary apertures circumferentially arranged in a spaced-apart manner about the tubular shell. 9. The system of claim 1 wherein the outlet vent terminates in an outlet opening in the sidewall of the cask in the second chamber of the annular gap. 10. The system of claim 1 wherein the tubular shell comprises a plurality of tube segments arranged in a stacked-assembly so that a surface contact interface is formed between a top edge and a bottom edge of adjacent tube segments, the system further comprising a collar located at each surface contact interfaces and extending above and below the surface contact interface. 11. The system of claim 10 wherein the primary aperture and the secondary aperture are located in a bottom-most tube segment of the stacked assembly. 12. The system of claim 11 wherein the air flow barrier is coupled to the bottom-most tube segment of the stacked assembly. 13. The system of claim 10 wherein the collar prohibits the adjacent tube segments from becoming axial misaligned while allowing the adjacent tube segments to be separated from one another through relative movement between the adjacent tube segments in the axial direction. 14. The system of claim 10 wherein each of the tube segments comprise a plurality of spacers circumferentially arranged in a spaced-apart manner about the tube segment and protruding from an inner surface of the tube segment to maintain the annular gap. 15. The system of claim 14 wherein each of the spacers comprise a means for facilitating engagement and lifting of the tube segment. 16. The system of claim 1 wherein the annular gap circumscribes the cask. 17. The system of claim 1 further comprising an annular top ring defining a central opening and coupled to a top end of the tubular shell, the annular top ring extending radially inward from the tubular end wall beyond the sidewall of the cask and spaced from a top surface of a lid of the cask, the central opening of the annular top ring being the opening at the top end of the tubular shell. 18. The system of claim 1 wherein the tubular shell has a height measured from the top end of the tubular shell to the bottom end of the tubular shell, the cask having a height measured from the top end of the cask to the bottom end of the cask, the height of the tubular shell being greater than the height of the cask. 19. The system of claim 18 wherein the tubular shell is a free-standing structure. 20. The system of claim 1 wherein the tubular shell is slidably removable from the cask by imparting axial movement to the tubular shell. 21. The system of claim 1 wherein the air flow barrier is coupled to the tubular shell and is flexible. 22. A system for containing high level radioactive materials comprising:a cask extending along a longitudinal axis and having an internal cavity for holding high level radioactive materials, the cask comprising a plurality of inlet vents at a bottom end of the cask for allowing cool air to enter the internal cavity and a plurality of outlet vents at a top end of the cask for allowing heated air to exit the internal cavity;a tubular shell extending from a bottom end to a top end, the tubular shell positioned to circumferentially surround the cask in a spaced apart manner so that an annular gap exists between the tubular shell and a sidewall of the cask, the tubular shell comprising a plurality of primary apertures forming passageways through the tubular shell and a plurality of secondary apertures forming passageways through the tubular shell; anda flexible annular seal coupled to the tubular shell that separates the annular gap into: (1) an upper chamber that forms a passageway between the primary aperture and the inlet vent of the cask; and (2) a second chamber that forms a passageway between the secondary aperture and an opening at the top end of the tubular shell, wherein cross-flow of air between the first and second chambers of the annular gap is prohibited by the flexible annular seal,wherein the primary apertures are each configured as a first air flow inlet for the first chamber, for air to flow into the primary aperture, through the first chamber, and to the inlet vent of the cask, the primary aperture being located at an axial height below the flexible annular seal, andwherein the secondary apertures are each configured as a second air flow inlet for the second chamber, for air to flow into the secondary aperture, through the second chamber, and to the opening at the top end of the tubular shell, the secondary aperture being located at an axial height above the flexible annular seal. 23. The system of claim 22 wherein the primary apertures are circumferentially arranged in a spaced-apart manner about the tubular shell and the secondary apertures are circumferentially arranged in a spaced-apart manner about the tubular shell. 24. The system of claim 23 wherein each of the inlet vents comprise an inlet opening in the sidewall of the cask, the primary apertures of the tubular shell being radially offset from the inlet openings of the inlet vents. 25. The system of claim 24 wherein each of the outlet vents terminate in an outlet opening in the sidewall of the cask in the upper chamber of the annular gap, wherein the primary apertures and the inlet opening are located at a first axial height, the secondary apertures are located at a second axial height, and the outlet openings are located at a third axial height, and wherein the first, second and third axial heights are different. 26. The system of claim 22 wherein the tubular shell comprises a plurality of tube segments arranged in a stacked-assembly so that a surface contact interface is formed between a top edge and a bottom edge of adjacent tube segments, the system further comprising a collar located at each surface contact interfaces and extending above and below the surface contact interface. 27. The system of claim 26 wherein each of the tube segments comprise a plurality of spacers circumferentially arranged in a spaced-apart manner about the tube segment and protruding from an inner surface of the tube segment to maintain the annular gap. 28. The system of claim 27 wherein each of the spacers comprise a means for facilitating engagement and lifting of the tube segment. 29. The system of claim 22 further comprising an annular top ring defining a central opening and coupled to a top end of the tubular shell, the annular top ring extending radially inward from the tubular end wall beyond the sidewall of the cask and spaced from a top surface of a lid of the cask, the central opening of the annular top ring being the opening at the top end of the tubular shell. 30. The system of claim 22 wherein the tubular shell has a height measured from the top end of the tubular shell to the bottom end of the tubular shell, the cask having a height measured from the top end of the cask to the bottom end of the cask, the height of the tubular shell being greater than the height of the cask. 31. The system of claim 22 wherein the tubular shell is a free-standing structure that is slidably removable from the cask by imparting axial movement to the tubular shell. 32. An apparatus for providing additional radiation shielding to a cask holding high level radioactive materials comprising:a tubular shell extending from an open bottom end to an open top end, the tubular shell having an inner surface that forms a cavity about a longitudinal axis;a plurality of primary apertures forming passageways through the tubular shell and circumferentially arranged in a spaced-apart manner about the tubular shell, each primary aperture being configured as a first air flow inlet;a plurality of secondary apertures forming passageways through the tubular shell and circumferentially arranged in a spaced-apart manner about the tubular shell, each of the secondary apertures being configured as a second air flow inlet;an annular seal coupled to the tubular shell and extending from the inner surface of the tubular shell; andwherein the secondary apertures are located at an axial height above the annular seal and the primary apertures are located at an axial height below the annular seal. 33. The apparatus of claim 32 wherein the annular seal is flexible. 34. The apparatus of claim 32 wherein the tubular shell comprises a plurality of tube segments arranged in a stacked-assembly so that a surface contact interface is formed between a top edge and a bottom edge of adjacent tube segments, the system further comprising a collar located at each surface contact interfaces and extending above and below the surface contact interface. 35. The apparatus of claim 34 wherein the primary aperture, the secondary aperture and the annular seal are located in a bottom-most tube segment of the stacked assembly. 36. The system of claim 34 wherein the collar prohibits the adjacent tube segments from becoming axial misaligned. 37. The system of claim 34 wherein each of the tube segments comprise a plurality of spacers circumferentially arranged in a spaced-apart manner about the tube segment and protruding from an inner surface of the tube segment to maintain the annular gap. 38. The system of claim 37 wherein each of the spacers comprise a means for facilitating engagement and lifting of the tube segment. 39. The system of claim 32 further comprising an annular top ring defining a central opening and coupled to a top end of the tubular shell, the annular top ring extending radially inward from the tubular end wall. 40. A method of containing high level radioactive materials comprising:a) positioning a cask on a support surface, the cask extending along a vertical axis and having an internal cavity containing high level radioactive materials, the cask comprising at least one inlet vent at a bottom end of the cask allowing cool air to enter the internal cavity and at least one outlet vent at a top end of the cask allowing heated air to exit the internal cavity; andb) sliding a tubular shell over the cask, the tubular shell circumferentially surrounding the cask in a spaced apart manner so that an annular gap exists between the tubular shell and a sidewall of the cask, the tubular shell comprising at least one primary aperture forming a passageway through the tubular shell, at least one secondary aperture forming a passageway through the tubular shell, and an air flow barrier extending between the tubular shell and the sidewall of the cask that separates the annular gap into: (1) a first chamber that forms a passageway between the primary aperture and the inlet vent of the cask; and (2) a second chamber that forms a passageway between the secondary aperture and an opening at the top end of the tubular shell, wherein cross-flow of air between the first and second chambers of the annular gap is prohibited by the air flow barrier,wherein the at least one primary aperture performs as a first air flow inlet for the first chamber, for air to flow into the primary aperture, through the first chamber, and to the inlet vent of the cask, andwherein the at least one secondary aperture performs as a second air flow inlet for the second chamber, for air to flow into the secondary aperture, through the second chamber. 41. The method of claim 40 further comprising:c) cool air entering the first chamber via the primary aperture of the tubular shell, the cool air within the first chamber being drawn into the internal cavity of the cask via an inlet duct, the cool air within the internal cavity becoming warmed within the internal cavity from heat emanating from the high level radioactive materials and exiting the internal cavity of the cask via an outlet duct as warmed air; ande) cool air entering the second chamber via the secondary aperture, the cool air within the second chamber being warmed by heat emanating from the cask and rising within the second chamber as warmed air; andwherein the warmed air exiting the outlet duct and the warmed air rising within the second chamber converge and exit the tubular shell via the opening at the top end of the tubular shell. 42. The method of claim 40 wherein step b) comprises sliding a plurality of tube segments over the cask and stacking the tube segments to form a stacked assembly that forms the tubular shell.
	claims	1. A method for evaluating a material specimen, comprising:mounting a neutron source adjacent the material specimen;mounting a detector adjacent the material specimen;bombarding the material specimen with neutrons from the neutron source to create prompt gamma rays within the material specimen, some of the prompt gamma rays being emitted from the material specimen, some of the prompt gamma rays resulting in the formation of positrons within the material specimen by pair production;collecting positron annihilation data by detecting with the detector a plurality of emitted annihilation gamma rays resulting from the annihilation of positrons, the detector producing the positron annihilation data;processing collected positron annihilation data in accordance with a Doppler-broadening algorithm; andcontinuing to collect and process positron annihilation data to measure an accumulation of lattice damage over time. 2. The method of claim 1, further comprising:collecting prompt gamma ray data by detecting with the detector a plurality of emitted prompt gamma rays, the detector producing the prompt gamma ray data;calculating positron lifetime data from the positron annihilation data and the prompt gamma ray data; andcontinuing to collect positron annihilation data and prompt gamma ray data and calculate positron lifetime data to measure an accumulation of lattice damage over time. 3. The method of claim 1, wherein said mounting a neutron source adjacent the material specimen comprises mounting the neutron source to the material specimen. 4. The method of claim 3, wherein said mounting a detector adjacent the material specimen comprises mounting the detector to the material specimen. 5. The method of claim 4, further comprising positioning a shield adjacent the neutron source to absorb stray neutrons. 6. The method of claim 5, further comprising positioning a moderator between the neutron source and the material specimen. 7. The method of claim 6, further comprising positioning a reflector adjacent the neutron source to reflect neutrons toward the material specimen. 8. The method of claim 1, wherein mounting a neutron source adjacent the material specimen comprises mounting an isotopic neutron source adjacent the material specimen. 9. The method of claim 8, wherein mounting an isotopic neutron source adjacent the material specimen comprises mounting a neutron source of 252Cf. 10. The method of claim 1, wherein continuing to collect and process positron annihilation data to measure an accumulation of lattice damage over time is performed while the material specimen is in service. 11. A method for evaluating a material specimen, comprising:mounting a neutron source adjacent the material specimen;mounting a detector adjacent the material specimen;bombarding the material specimen with neutrons from the neutron source to create prompt gamma rays within the material specimen, some of the prompt gamma rays being emitted from the material specimen, some of the prompt gamma rays resulting in the formation of positrons within the material specimen by pair production;collecting positron annihilation data by detecting with the detector a plurality of emitted annihilation gamma rays resulting from the annihilation of positrons, the detector producing the positron annihilation data;storing the positron annihilation data on a data storage system for later retrieval and processing; andcontinuing to collect and store positron annihilation data, the continued collected and stored positron annihilation data being indicative of an accumulation of lattice damage over time. 12. The method of claim 11, further comprising:collecting prompt gamma ray data by detecting with the detector a plurality of emitted prompt gamma rays, the detector producing the prompt gamma ray data; storing prompt gamma ray data on the data storage system for later retrieval and processing; and continuing to collect and store prompt gamma ray data, the continued collected and stored prompt gamma ray data being indicative of an accumulation of lattice damage over time. 13. The method of claim 11, wherein said mounting a neutron source adjacent the material specimen comprises mounting the neutron source to the material specimen. 14. The method of claim 13, wherein said mounting a detector adjacent the material specimen comprises mounting the detector to the material specimen. 15. The method of claim 14, further comprising positioning a shield adjacent the neutron source to absorb stray neutrons. 16. The method of claim 15, further comprising positioning a moderator between the neutron source and the material specimen. 17. The method of claim 11, wherein mounting a neutron source adjacent the material specimen comprises mounting an isotopic neutron source adjacent the material specimen. 18. The method of claim 11, wherein continuing to collect and store positron annihilation data is performed while the material specimen is in service. 19. The method of claim 11, further comprising: retrieving stored positron annihilation data; andprocessing the positron annihilation data in accordance with a Doppler-broadening algorithm to produce output data indicative of an accumulation of lattice damage over time. 20. The method of claim 1, further comprising removing the neutron source before collecting positron annihilation data. 21. The method of claim 11, further comprising removing the neutron source before collecting positron annihilation data.
062298682	abstract	The present invention relates to a fuel assembly for a light-water nuclear reactor with a substantially square cross section which comprises fuel rods (4) extending between a bottom tie plate (16) and a top tie plate (17). A coolant is adapted, during operation, to flow upwards through the fuel assembly. According to one aspect of the invention, the fuel assembly comprises a plurality of fuel units (3) stacked on top of each other, wherein each fuel unit (3) comprises a plurality of fuel rods (4) extending between a top tie plate (17) and a bottom tie plate (16). The fuel units are arranged attached to a support structure (4a, 14, 14a, 14b) extending through the whole fuel assembly such that axial gaps are formed between the fuel units (3). One of the tie plates is freely movable relative to the support structure.
039869253	claims	1. Power plant including nuclear reactor means, comprising: a plurality of similarly constructed units, each unit including a portion of the nuclear reactor, including nuclear fuel elements for developing thermal energy for the unit, each unit further having an individual, closed loop circulation path for liquidous alkaline metal as working and cooling liquid, passing through the reactor portion of the respective unit in heat exchanging relation therewith, there being a separate circulation path of alkaline metal in each unit, and a separate MHD-generator included in the respective circulation path for and of each unit accordingly, the alkaline metal passing through and serving as working fluid for the respective MHD-generator; the units of the plurality disposed in a bundle so as to be located in the vicinity to each other so that the several portions of the reactors are intercoupled through the neutron flux as established by each portion, the bundling providing inner units and outer units of the bundle; circuit means connected to the MHD-generators of the units, for connecting the respective electrical outputs of the generators in parallel so that the individual units operate as load wherein the MHD-generator of a unit draws energy from the circuit means and pumps working fluid through the unit, or as power producing unit, the outer units normally operating as pumps; and means defining an air circulation path coupled to the closed loop circulation paths for working fluid of the units of the plurality ahead of the respective returns thereof to the nuclear reactor, for extracting therefrom residual thermal energy. causing alkaline metal to circulate in each circulation path in heat exchange relation with the respective reactor portion of the unit and as working fluid for and in the respective MHD-generator; disposing the units in a bundle so as to be located in the vicinity to each other so that the several portions of the reactors are intercoupled through the neutron flux as established by each portion, the bundling providing inner units and outer units of the bundle; electrically interconnecting electrical outputs of the MHD-generators of the units in parallel; operating the inner units of the bundle as electrical power producing units; and operating the outer units as pumps by drawing power from the inner units and causing the respective MHD-generator to pump the working fluid through the respective units. a plurality of heat exchange fluid paths and circulations through the nuclear reactor, each path traversing different portions of the reactor; a plurality of MHD-generators each included in one of the circulations and operating with the same heat exchange fluid of the respective circulation that traversed one of the portions of the reactor, the heat exchange fluid in each circulation by alkaline metal; the different portions of the reactor having a common neutron flux distribution; some of the MHD-generators operating as pumps at relatively low thermal energy production in the respectively associated nuclear reactor portion; the remainder of the MHD-generators operating as electric power generators at relatively high thermal energy production in the respectively associated nuclear reactor portion; and circuit means interconnecting the MHD-generators so that the ones operating as generators drive the ones operating as pumps, the remainder of electric power generated being usefull electric output. 2. Power plant as in claim 1, the units of the plurality each having elongated extension, the nuclear reactor portion being on one end of each unit, an air-alkaline heat exchanger disposed close to the other end of each unit, the units disposed parallel to each other, the nuclear reactor portions aligned parallel to a plane transverse to the elongated extension of the units. 3. Power plant as in claim 1, the units of the plurality stacked in a bundle, there being outer ones and inner ones, the plant including control means connected to the units for normally operating the inner units for production of power, the outer units as disposed around the inner units establishing power reserve units, normally operated as loads, the control means operating the later units also for production of power upon increase of power demand. 4. Power plant as in claim 1, there being a honeycomb support structure for the units of the plurality. 5. Power plant as in claim 1, the air circulation path including a compressor and a turbine coupled for driving the compressor, the compressor sustaining air circulation for heat exchange with the alkaline metal, the turbine receiving the heated air. 6. Power plant as in claim 1, each unit including a compressor, a turbine, and a heat exchanger, the heat exchanger having primary circulation that is included in the closed circulation of alkaline metal in the unit, having secondary circulation of air, circulated by the compressor and driving the turbine, the turbine driving the compressor. 7. Power plant as in claim 1, the air circulation path including all units of the plurality, there being a sea water desalination plant connected to receive the heated air from all units as principal heating source. 8. Power plant as in claim 1, including common control means, individually controlling the nuclear reactor portions in accordance with a particular program and in dependence upon demand for electrical power. 9. Power plant as in claim 1, the program causing the control means to operate some of the units for production of electrical energy, others of the units are operated as load, some of the latter units operated for production of energy upon increase of demand. 10. Method of generating electrical energy, comprising the steps of providing a plurality of similarly constructed units, each unit including a portion of the nuclear reactor, including nuclear fuel elements for developing thermal energy for the unit, each unit further having an individual, closed loop circulation path for a cooling and working fluid, and a separate MHD-generator in the respective circulation path for each unit; 11. A method as in claim 10, and including the step of changing the number of units operated as power producing units vs. the number of units operating as pumps. 12. Power plant including a nuclear reactor comprising: 13. Power plant as in claim 12, wherein the reactor is physically subdivided into portions, the portions being physically mounted together with the respective MHD-generator in a modular construction of similar units, each composed of a reactor portion, and MHD-generator of the plurality and the circulation of alkaline metal. 14. Power plant as in claim 12, and including an additional circulation common to all units and having air coupled in heat exchange relation to the alkaline circulations of the units prior to return thereof to the respective nuclear reactor portion.
	claims	1. A radiolabelling kit comprising:a first vial, wherein said first vial is empty and under vacuum;a second vial, wherein said second vial comprises a suitable amount of acetate buffer for balancing the pH of an eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said eluate is eluted into the kit; anda third vial, wherein said third vial comprises a lyophilized chelate-functionalized targeting agent and a lyophilized metal inhibitor,wherein the chelator group of said chelate-functionalized targeting agent is selected from the group consisting of: NOTA, NODAGA, Tris(hydroxypyridinone) (THP), HBED, DFO 6SS, B6SS, PLED, YM103, and H2dedpa; andwherein said metal inhibitor is selected from the group consisting of: DOTA, tetra-tBu-DTPA, beta-cyclodextrin and a monosacccharide. 2. The radiolabelling kit according to claim 1, wherein the chelate-functionalized targeting agent is chelate-functionalized prostate-specific membrane antigen (PSMA)-targeting peptide. 3. The radiolabelling kit according to claim 1, wherein the monosaccharide is selected from the group consisting of glucose, fructose, and D-mannose. 4. The radiolabelling kit according to claim 1, wherein the kit comprises one or more of the list consisting of:a needleless transfer device for connecting two vials;an extension line comprising a proximal end adapted for connecting the extension line to a vial adapter and a distal end adapted for connecting the extension line to a needleless syringe;a vial adapter adapted for connecting an extension line or a needleless syringe to a vial; anda needleless syringe. 5. The radiolabelling kit according to claim 1, wherein the chelate-functionalized targeting agent is PSMA-11. 6. The radiolabelling kit according to claim 5, wherein the metal inhibitor is D-mannose. 7. An assembly comprising the radiolabeling kit according to claim 1 and a self-shielded device configured to hold said first vial. 8. The assembly according to claim 7, further comprising a gallium-68 generator. 9. The assembly according to claim 7, wherein the self-shielded device is invertible. 10. The assembly according to claim 7, wherein the self-shielded device comprises a support (2) and a container unit wherein said container unit comprises a container lid (3) and a container vessel (4) comprising a void space dimensioned to hold said first vial; and wherein the support comprises a base (1) and extending from the base and in fixed relation to the base at least one longitudinal member (6). 11. The assembly according to claim 10, wherein the dimensions of the void space suitable for holding the first vial are at most 10% larger than the dimensions of the first vial. 12. The assembly according to claim 10, wherein the at least one longitudinal member (6) is provided in revolute attachment with respect to the container vessel (4), where an axis of rotation is horizontal, non-parallel to a central axis of the first vial and/or parallel to an underside of the base (1). 13. The assembly according to claim 10, wherein the container lid (3) is in revolute attachment with respect to the container vessel (4), where an axis of rotation is vertical, parallel to a central axis of the first vial and/or non-parallel to an underside of the base (1). 14. The assembly according to claim 10, wherein the container unit is provided with a channel configured to hold a dismountable conduit for connecting the first vial within the self-shielding device to an environment external of the self-shielded device, wherein the channel configured to hold a dismountable conduit is provided at the interface of the container lid (3) and the container vessel (4). 15. The assembly according to claim 7, wherein the chelate-functionalized targeting agent is PSMA-11. 16. The assembly according to claim 15, wherein the metal inhibitor is D-mannose.
	abstract	A method of adjusting a lithography system or tool to enhance image quality correction is presented. The method enhances image quality correction by using a reduced dose during exposure of the lithographic test patterns. A typical lithography system (tool) comprises an exposure column unit and a control unit. The exposure column unit generates a shaped beam and directs this shaped beam through lenses and a series of deflectors to a mask which is positioned on a movable stage. The control unit provides control management for the components of the exposure column unit. The system maximizes pattern resolution using a mask having test pattern geometries that are at least the same size as the geometries of the pattern of a production mask. The reduced exposure dose used for the lithographic test patterns results in greater sensitivity to small beam setup errors. This enables finer tuning of the lithographic tool through adjustments in lens currents and correction coil currents and thereby results in improved resolution for production integrated circuits.
	description	Embodiments described herein generally relate to a shielding apparatus to shield a high-energy, high-power X-ray source. Here, high-energy denotes X-rays with energies in the multi-MeV energy range. In particular, embodiments relate to an apparatus for shielding an X-ray source, where the X-ray source is intended for the use of gamma activation analysis. Particular applications relate to use of the X-ray source for the analysis of gold and other valuable elements such as silver, copper and lead in mineral ore samples. A method is further provided to optimise shielding for an X-ray radiation apparatus. Gamma activation analysis (GAA), also known as photon activation analysis, uses a high-energy X-ray source to induce nuclear reactions in target elements in a sample, and then measures decay radiation emitted by the activated sample to determine the concentrations of these elements. Typically, X-rays in the multi-MeV energy range are produced using sources that use an electron accelerator fitted with a conversion target to produce X-rays via the Bremsstrahlung process. A common type of electron accelerator is a linear accelerator or LINAC. If elements present at low concentrations are to be detected with good sensitivity, then a high-intensity X-ray source is required. For example, a linear accelerator beam power of 5-10 kW or higher may be used. Beam power described herein refers to the power of the accelerated electron beam incident on the X-ray conversion target. Such high intensity sources produce prodigious quantities of X-ray radiation, often in the range of 100-200 Sieverts(Sv)/min, measured at one metre from the X-ray emission point. Such radiation levels present a severe risk to personnel, and must be reduced using appropriate shielding. X-ray sources used for GAA are generally operated at source energies of at least 7 MeV, and can be used at energies up to 15 MeV, or even higher. The source energy refers to the peak energy of the accelerated electron beam, which corresponds to the end-point energy of the X-ray Bremsstrahlung spectrum. These energies are sufficiently high enough to induce nuclear reactions in certain elements. These reactions commonly include the production of neutrons, which present an additional radiation hazard. It is necessary that shielding be designed to also reduce neutron radiation levels in accessible areas to an acceptable level. Conventionally, accelerator-based systems for industrial application fall into three broad categories: 1. Those used for radiation therapy in hospital environments. X-ray sources associated with these systems are typically operated at source energies ranging from a few MeV to 15-18 MeV, but have a relatively low power (a dose rate of a few Sv/min) and very low duty cycle (up to 500 Sv/week). Shielding is normally provided by building a massive concrete ‘bunker’ with a convoluted passageway or ‘maze’ to provide access. 2. Accelerators used for industrial sterilisation or product irradiation and which are typically operated at source energies of up to 10 MeV. In this type of system the beam powers can be very high, of the order of 10-20 kW or more. Again, shielding is provided by massive concrete construction, with objects to be irradiated conveyed on a curved path to avoid radiation streaming. Massive shielding doors may also be deployed. 3. Accelerators used for security imaging applications such as cargo scanning. Such systems are generally operated at a low source energy of about 6 MeV or in dual-energy mode (for example, alternating between 3 and 6 MeV), although energies up to 9 MeV can be used in some applications. In these systems the beam power is also generally very low and neutron production is not a significant consideration. Shielding generally comprises lead or tungsten around the accelerator, and a steel-walled cabin. Conventional methods of deploying the type of high-power accelerator source used for GAA require the construction of a dedicated, special-purpose concrete shield. Typically, the shielding thickness required is of order 1.5-2.0 m, which leads to a large footprint and masses of hundreds to thousands of tonnes. Alternative existing approaches to accelerator shielding include the development of special purpose materials that provide both X-ray and neutron shielding. One example consists of a concrete mixture combined with special X-ray and neutron absorbing additives. However, such approaches increase the overall mass of shielding required. It is desirable to provide an improved shielding apparatus for use with a high-energy, high-powered X-ray source suitable for GAA. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application. Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. A shielded X-ray radiation apparatus is provided. The shielded X-ray radiation apparatus comprising: an X-ray source; an X-ray attenuation shield including an elongated cavity having a region at one end to accommodate a sample; a neutron attenuation shield; a gamma attenuation shield; and wherein the neutron attenuation shield is adjacent to and substantially surrounds the X-ray attenuation shield; and wherein the gamma attenuation shield is adjacent to and substantially surrounds the neutron attenuation shield. The X-ray source may be any suitable device for gamma activation analysis. The X-ray source may include an electron accelerator for generating an electron beam having an electron beam direction, and an conversion target at which the electron beam is directed. In one embodiment, the energy of the electron beam generated from the electron accelerator may be between 7 MeV and 15 MeV and the electron accelerator may be operable with a beam power of at least 0.5 kW, and preferably of about 8 kW. The maximum beam power may be a decreasing function of the beam energy. In another embodiment the energy of the electron beam generated from the electron accelerator may be between 7 MeV and 10 MeV. In such an embodiment electron accelerator may have a maximum beam power of 2 kW. Conceivably, the energy of the electron beam generated from the electron accelerator may be between 8 MeV and 10 MeV. In such an embodiment electron accelerator may have a maximum beam power of between 8 kW and 20 kW. The X-ray attenuation shield is preferably constructed from a high density material and is preferably constructed principally of lead. Less preferably, the X-ray attenuation shield is constructed principally of tungsten. Alternatively the X-ray attenuation shield is constructed of layers of lead and tungsten. The neutron attenuation shield is preferably constructed from a polymer material having a hydrogen density of approximately 0.1 g/cm3. Polymers with the generic formula (—CH2—)n, such as polyethylene, are particularly suitable. Alternatively, the neutron attenuation shield may be formed from a cast resin such as polyurethane resin. The shield may include hydrogen enriching materials, such as, but not limited to one or more of polyethylene or polypropylene. The polymer material may optionally, or in addition, include a proportion of a substantially neutron-absorbing element chosen from the group including boron and lithium. The proportion of the neutron-absorbing element may be in the range 1-5 wt %, and preferably be 5 wt %. The gamma attenuation shield is preferably constructed principally of lead. Less preferably, the gamma attenuation shield is constructed principally of steel. Alternatively the gamma attenuation shield is constructed of composite layers of lead and steel. A portion of the cavity's inner walls may be lined with a support casing to support at least the electron accelerator, X-ray conversion target and irradiated sample in the correct relative positions. Preferably the support casing is constructed from steel. Alternative materials may be selected as long as the materials are substantially free from elements that readily activate via X-ray or neutron-induced nuclear reactions. The thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction may be in the range of 60-80% of the thickness in the forward direction, and the thickness at an angle of 180° from the electron beam direction may be in the range of 25 to 50% of the thickness in the forward direction. More preferably, the thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction may be approximately 75% of the thickness in the forward direction, and the thickness at an angle of 180° from the electron beam direction may be approximately 50% of the thickness in the forward direction. The thickness of the X-ray attenuation shield thickness in the forward direction may be estimated using tabulated tenth value layers and a desired dose attenuation factor. More particularly, the X-ray attenuation shield thickness (tXR) in the forward direction may be estimated by the equation: tXR=TVL×log10 [(R×60×106)/(r d2)], where d is the distance from the target at which the reduced dose rate is to be calculated, R is the dose rate at 1 m from the target produced by the unshielded source, r is the desired shielded does rate at the closest personnel-accessible point at distance d and TVL is the predefined tenth value layer for the X-ray attenuation shield material. The thickness of the neutron attenuation layer may be determined from knowledge of the neutron production rate of the X-ray source. The neutron production rate is a function of the design of the source, particularly the X-ray conversion target, and of the energy of the electron beam. Commonly, the neutron emission rate will be provided by the source manufacturer in terms of the dose rate (Sv) due to neutron emission divided by the dose rate (Sv) due to X-ray emission. From this parameter, the unshielded neutron dose rate at a given distance from the source may be calculated from knowledge of the forward-directed X-ray dose rate. The required neutron attenuation factor, f can be calculated as the ratio of the unshielded dose rate to the desired shielded rate. The thickness of the neutron shield in the forward direction can be estimated using the formula TVL*log10(f) where TVL is the tabulated tenth-value thickness of low-energy neutrons in the chosen neutron attenuation material. For example, the TVL in borated polyethylene for neutrons produced by X-rays with end-point energies up to 15 MeV is 62 mm. A neutron shield of thickness 200-300 mm will then reduce the neutron flux by a factor of 1700-7000. As neutron emission is substantially isotropic, the thickness of the neutron attenuation layer may be chosen to be approximately constant with angle from the electron beam direction. If the elongation of the shield required to accommodate the X-ray source is substantial, the closest accessible point in the rear direction (close to 180°) may be significantly further from the X-ray conversion target than the closest accessible point in the forward direction. In this case, the thickness of the neutron attenuation shield in the rear direction may be proportionally reduced. Preferably, the thickness in the rear direction is 50-100% of the thickness in the forward direction. Preferably the gamma attenuation shield has a thickness which is proportional to the optimised thickness of the neutron attenuation shield. The shielded X-ray radiation apparatus may further comprise a removable sample insertion means for inserting samples into the elongate cavity; wherein the removable sample insertion means is composed of adjacent blocks of materials, each respective block having a thickness and a composition which substantially matches the thickness and a composition of one of the X-ray attenuation, neutron attenuation and gamma-ray attenuation shields. The removable sample insertion means may further comprise a stage member on which a sample to be irradiated is locatable; and wherein the adjacent blocks of materials comprise a first block adjacent the stage member, a second block abutting the first block, and a third block abutting the second block; wherein: the first block is comprised of a material to substantially attenuate X-rays and having a thickness which is the same or substantially the same as the X-ray attenuation shield, the second block is comprised of a material to substantially attenuate neutrons and having a thickness which is the same or substantially the same as the neutron attenuation shield, and the third block is comprised of a material to substantially attenuate gamma-rays with a thickness which is the same or substantially the same as the gamma attenuation shield; and wherein the shielded X-ray radiation apparatus comprises a sleeve through which the stage member is able to traverse. Preferably the sleeve of the apparatus and the removable sample insertion means has a clearance tolerance of less than 2.00 mm, more preferably less than 1.00 mm, and more preferably less than 0.50 mm. The stage member of the removable sample insertion means may be manufactured from steel, or any another substance that is free from elements that undergo significant activation from X-rays or neutrons. In one embodiment, the outer profile of the removable sample insertion means is stepped, with at least one of the dimensions of one or more of the blocks increasing in a direction perpendicular to a direction of travel with increasing distance from the stage member. The width of the or each step is preferably in the range of 5 to 15 mm. For example, the first block may comprise of at least two steps, such that the dimensions of the block increase in a stepwise fashion from the innermost to outermost steps. The width of each step may be in the range 5 to 15 mm. The first block is preferably made from a material substantially attenuating for X-rays, such as lead or tungsten. The first block may be adhered to the stage member by any suitable means. For example, the stage may comprise an angled bracket incorporating holes through which bolts may be inserted to rigidly attached the first block portion to the stage. The second block may be a unitary block having an inner face and an outer face. The inner face of the second block portion preferably abuts the outer face of the outermost step of the first block. The second block may be adhered to the first block by any suitable means way, for instance by way of a steel bracket bolting respective sections to one another. The second block is preferably made of the material used to construct the neutron attenuation shield, or it may be made of an alternative material substantially attenuating to neutrons, such as polyethylene containing 5 wt % boron. The third block may be a unitary block having an inner face and an outer face. The inner face of the third block preferably abuts the outer face of the second block. The third block may be adhered to the second block by any suitable means, such as a steel bracket bolting the respective sections to one another. Alternatively, the third block may be shaped to provide direct means for bolting to the second block. The third block is preferably be made of a material substantially attenuating for gamma-rays, such as lead or tungsten. The removable sample insertion means may further comprise an attachment portion having an inner face, wherein the dimensions of the inner face are the same as or larger than the dimensions of the outer face of the third block, and wherein the outer face of the third block abuts the inner face of the attachment portion. The attachment block portion may be adhered to the third block by any suitable means. The attachment portion may be hollow. The material from which the attachment portion is constructed need not be a radiation shielding material. The attachment means may be fixed to a linear drive mechanism to insert and remove the removable sample insertion means from the X-ray shield. Advantageously, embodiments utilising the removable sample insertion means enable insertion and removal of samples to be analysed through the sequentially layered shield without compromising its shielding integrity. A further shielded X-ray radiation apparatus is provided, the radiation apparatus comprising: an X-ray source; an X-ray attenuation shield including an elongate cavity to house the X-ray source and incorporating a region to accommodate a sample; a neutron attenuation shield adjacent to and substantially surrounding the X-ray attenuation shield; a gamma attenuation shield adjacent to and substantially surrounding the neutron attenuation shield; and a removable sample insertion means for inserting samples into the elongate cavity; wherein the removable sample insertion means is composed of adjacent blocks of material, each respective block having a thickness and a composition which substantially matches the thickness and a composition of the X-ray attenuation, neutron attenuation and gamma-ray attenuation shields respectively. The removable sample insertion means may further comprise a stage member on which a sample to be irradiated is locatable; wherein the adjacent blocks of materials comprise a first block adjacent the stage member, a second block abutting the first block, and a third block abutting the second block; wherein: the first block is comprised of a material to substantially attenuate X-rays and having a thickness which is the same or substantially the same as the X-ray attenuation shield, the second block is comprised of a material to substantially attenuate neutrons and having a thickness which is the same or substantially the same as the neutron attenuation shield, and the third block is comprised of a material to substantially attenuate gamma-rays with a thickness which is the same or substantially the same as the gamma attenuation shield; and wherein the shielded X-ray radiation apparatus comprises a sleeve through which the stage member is able to traverse. The sleeve of the apparatus and the removable sample insertion means may have a clearance tolerance of less than 2.00 mm, more preferably less than 1.00 mm, and more preferably less than 0.50 mm. The outer profile of the removable sample insertion means may be stepped, with at least one of the adjacent blocks increasing in height or width, in a direction perpendicular to a direction of travel with increasing distance from the stage member. The width of the or each step may be in the range of 5 to 15 mm. In one embodiment, the first block comprises at least two steps, such that the dimensions of the first block increase in a stepwise fashion from the innermost to outermost steps. The X-ray attenuation shield may have a thickness which decreases with increasing angle from the electron beam direction. The thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction may be in the range of 60-80% of the thickness in the forward direction, and the thickness at an angle of 180° from the electron beam direction may be in the range of 25 to 50% of the thickness in the forward direction. More preferably, the thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction may be approximately 75% of the thickness in the forward direction, and the thickness at an angle of 180° from the electron beam direction may be approximately 50% of the thickness in the forward direction. The thickness and the materials from which the respective shields are formed may be configured in accordance with the description thus far taught. A method is provided to optimise shielding for an X-ray radiation apparatus, in which the apparatus comprises an X-ray attenuation shield including an elongate cavity to house an X-ray source, a neutron attenuation shield adjacent to and substantially surrounding the X-ray attenuation shield, and a gamma attenuation shield adjacent to and substantially surrounding the neutron attenuation shield, the method comprising: determining a first thickness (tXR) of the X-ray attenuation shield in the forward direction by the equation: tXR=TVL×log10 [(R×60×106)/(r d2)], where d is the distance from an electron target, R is the dose rate at 1 m from the electron target produced by an X-ray source, r is the shielded does rate at the closest personnel-accessible point and TVL is a predefined tenth value layer for the X-ray attenuation shield material; determining a thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction to be in the range of 60-80% of the thickness in the forward direction; and determining a thickness of the X-ray attenuation shield at an angle of 180° from the electron beam direction to be in the range of 25-50% of the thickness in the forward direction. The method to optimise shielding for an X-ray radiation apparatus may further comprise determining a thickness of the X-ray attenuation shield at an angle of 90° from the electron beam direction to be approximately 75% of the thickness in the forward direction. The method to optimise shielding for an X-ray radiation apparatus may further comprise determining a thickness of the X-ray attenuation shield at an angle of 180° from the electron beam direction to be approximately 50% of the thickness in the forward direction. The method to optimise shielding for an X-ray radiation apparatus may further comprise determining a thickness (tnt) of the neutron attenuation shield in a forward direction by the equation: tnt=TVLn log10(f), where TVLn is a predefined tenth-value layer for the attenuation of low energy neutrons in the neutron attenuation shield and f is a ratio of an unshielded dose rate to a desired shielded rate. The method to optimise shielding for an X-ray radiation apparatus may further comprise determining the thickness of the neutron attenuation shield at an angle of 180° from the electron beam direction in a rearward direction to be 50% to 100% of the thickness (tnt) in the forward direction. The method to optimise shielding for an X-ray radiation apparatus may further comprise determining the thickness of the gamma attenuation shield to be proportional to the thickness of the neutron attenuation shield. FIG. 1 illustrates an example of a shielded X-ray radiation apparatus 100 which is configured to operate with an end-point energy that can be varied over the range 8-14 MeV. The maximum X-ray dose rate delivered by the X-ray generator (not shown) varies from 160 Sv/min at an operating energy of 8 MeV to 25 Sv/min at an operating energy of 14 MeV. The shielded X-ray radiation apparatus 100 includes an X-ray attenuation shield 110 and 111, a neutron attenuation shield 120 and 121 and a gamma attenuation shield 130 and 131. The X-ray attenuation shield includes a cavity 106 which is approximately 1.5 m in length that houses the LINAC (not shown). The LINAC accelerates a beam of electrons 101 onto a conversion target 102, producing Bremsstrahlung X-ray radiation which is substantially directed in the direction of the electron beam. In use, the X-ray radiation irradiates a sample 103. The cavity 106 housing the forward portion of the LINAC, the conversion target 102 and the sample 103 is substantially surrounded by a support casing 104 that provides means of supporting the LINAC, target and sample in the correction relative positions. Lead, being a soft and malleable material, is poorly suited for this purpose. In this example, the support casing 104 is made from a material such as steel. In other examples the selected material should be substantially free from elements that readily activate via X-ray or neutron-induced nuclear reactions. For example, the casing should be free of the element cobalt, which leads to the formation of the long-lived 60Co isotope via the capture of neutrons. The formation of such long-lived isotopes may lead to difficulties in the eventual decommissioning or disposal of the shielding components. The X-ray attenuation shield (a primary shield) comprises a head portion 110 and a body portion 111. The thickness of the X-ray attenuation shield is a function of the angle from the electron beam direction: directions of 0, 30, 60, 90, 120, 150 and 180 degrees are indicated on FIG. 1. The thickness is calculated in accordance with the description provided later on in the specification. The X-ray attenuation shield 110, 111 may be formed by casting molten lead into a mould or steel shell. The X-ray attenuation shield 110, 111 is surrounded by a neutron attenuation shield (a secondary shield) 120, 121 formed of polyethylene containing 5% by weight of boron. The thickness of the neutron attenuation shield is in accordance with the description provided later on in the specification. In this example, the neutron attenuation shield 110, 111 is formed from flat sheets of material. The neutron attenuation shield 110, 111 is surrounded by a gamma attenuation shield 130, 131 (a tertiary shield) formed from lead sheets. The gamma attenuation shield has a thickness proportional to the thickness of the underlying neutron attenuation shield. In the example shown, the ratio of thicknesses of the gamma attenuation shield to the neutron attenuation shield is 1:10. The overall dimensions of the layered shield (110 and 111, 120 and 121, 130 and 131) are approximately 3300 mm in length and 1650 mm in width, and the total shielding mass is approximately 22 tonnes. Consequently, the shielding design can be comfortably accommodated within the size and mass constraints of a standard 20′ shipping container. The sample 103 to be irradiated is inserted and removed through the layered shielding by way of a movable sample insertion means, otherwise referred to as a plug 140. The plug 140 passes through a sleeve 141 fitted into the primary, secondary and tertiary shielding layers. The clearance between the sleeve 141 and plug 140 shall be as small as practicably possible, allowing for motion of the plug. The tolerance is preferably less than 0.5 mm. The design of the plug 140 is shown in more detail in FIG. 2. The sample 103 is supported on stage member 150 which is formed from steel or a similar material. In accordance with the design of the casing 104, the material from which the stage member is manufactured should also be free from elements that undergo significant activation from X-rays or neutrons. The second section of the plug 160 comprises at least two stepped portions 161, 162, with the dimensions of the outermost step 162 larger than the innermost 161. In the example shown, the step has a width of 10 mm. The second section of the plug 160 is formed from a material providing efficient attenuation of X-rays, such as lead or tungsten. Preferably, this section of the plug 160 shall be formed from a material substantially similar to that used for the X-ray attenuation shield 110,111. The third section of the plug 170 is constructed of a material that efficiently stops neutrons. Preferably the third section of the plug is manufactured from a material substantially similar to that used to form the neutron attenuation shield 120,121. A joining member 171 for joining the second and third sections of the plug is provided. The joining member 171 is a steel bracket bolted to the second and third sections of the plug. The fourth section of the plug 180 is constructed of a material that provides efficient attenuation of X-rays, such as lead or tungsten. In this example the fourth section of the plug includes two steps, though in other examples it could include more than two steps, or only a single step. The last section of the plug 190 is provided to enable the entire plug to be attached to a mechanism which provides linear motion (not shown) to transport the plug into and out of the cavity. This section 190, which is not required to provide any shielding function, may be solid or hollow structure with means to attach to a linear motion device. The X-Ray Attenuation Shield Tables of the X-ray shielding efficacy of different materials are readily available (for example, NCRP Report 151 “Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-ray Radiotherapy facilities”). Shielding efficiency is commonly quoted as ‘tenth value layers’ (TVLs), being the thickness of material required to reduce the X-ray dose rate by a factor of 10. TVLs are a function of material composition, material density and X-ray source energy. For example, reported TVL values for a 10 MeV X-ray source are 57/57 mm for lead, 410/370 mm for concrete and 110/110 mm for steel. In each case the first reported value is the TVL for the first layer of shielding, and the second reported value is the TVL for all subsequent layers of shielding. Consider a shielding design for a particular X-ray source designed to reduce dose rates by a particular factor. Let the shield be constructed from lead and have a total mass M. If the shielding material is changed to steel, then each linear dimension of the shield will need to be increased by a factor of 110/57=1.93 to achieve the same dose rate reduction factor. The mass of the new shield, M′, will be given by:M′=M×1.93k×density of steel/density of lead where k is an exponent with a value between 1 and 3. If the cavity 106 housing the X-ray generator is large compared to the layered shielding thickness (as is common in radiotherapy units, where the X-ray source is held in a room large enough to accommodate a patient) then k is approximately 1. If the thickness of the layered shielding is large compared to the size of the cavity 106, then k is close to 3. For relatively compact shielding designs, the value of k is between 2 and 3. With k=2, M′=2.6 M; for k=3, M′=5.0. Therefore, the consequence of switching from lead shielding to steel shielding is to increase the required mass of the shield by a factor of 2.6-5.0. If the X-ray attenuation shield 110, 111 is constructed from concrete rather than lead, which has a still lower density, the increase in mass is a factor of 8.8-57. The inventor has determined that it is advantageous to construct the X-ray attenuation shield 110, 111 from a high-density material, and most preferably lead, if the aim is to reduce the overall mass of the shielding. Neutron Attenuation Shielding A significant drawback of constructing the X-ray attenuation shield from an element such as lead is the production of photoneutrons. Generally, the X-ray threshold energy for the production of neutrons via (g,n) reactions decreases with increasing atomic number, and the reaction probability or cross-section increases. Lead consists of 4 naturally occurring isotopes: 204Pb (1.4%), 206Pb (24.1%), 207Pb (22.1%) and 208Pb (52.4%). The (g,n) thresholds for these isotopes are 8.4, 8.1, 6.7 and 7.4 MeV respectively. This means that an accelerator operated to produce X-rays with an end-point energy of about 6.7 MeV or higher will give rise to photoneutrons, with the production of neutrons increasing rapidly with increasing X-ray energy. Heavy metals such as lead are very poor at shielding neutrons. The inventor considered adding a neutron attenuation shield outside of the X-ray shield, being formed from a material which efficiently thermalises (slows-down) and absorbs neutrons. Materials with a high hydrogen content are very efficient at slowing down neutrons, due to the high energy loss that occurs in elastic (n,p) collisions. Examples of suitable materials having a high hydrogen content include polymers with the generic formula (—CH2-)n such as polyethylene and polypropylene, and water. The hydrogen content of these materials is approximately 0.11-0.13 g/cm3. Advantageously, polymers such as polyethylene are available in large, self-supporting sheets which simplifies construction of the shielding. Other neutron shielding options include materials such as polyurethane resin, which can be cast into the required form. The resin may be mixed with materials such as polyethylene pellets to increase the hydrogen content. Advantageously, the neutron shielding layer is designed to include a proportion of an element, such as boron (B), that strongly absorbs thermal neutrons. The isotope 10B (19.9% of natural boron) has a thermal neutron absorption cross-section of 3835 barns, compared to a value of just 0.333 barns for 1H and 0.00353 barns for 12C. The gamma-ray produced when boron absorbs a neutron has an energy of 478 keV compared to 2234 keV resulting from neutron capture by hydrogen. Optionally, lithium (Li) may be selected as an absorbing element. The isotope 6Li (7.6% of natural lithium) has a thermal neutron absorption cross-section of 940 barns. The lower cross-section and lower isotope fraction mean that lithium is a less efficient neutron absorber than boron. However, lithium produces no gamma-rays during neutron capture. Boron or lithium can be incorporated into the neutron shield in various forms. Boron-loaded and lithium-loaded polyethylene is available with various concentrations of dopants. A loading of 5% is typical and provides efficient thermal neutron absorption. Soluble boron or lithium compounds can be added to water. Powdered boron or lithium compounds can be added to resin or resin-polymer bead mixtures. The tenth value layer (TVL) thickness for neutrons in a material such as borated polyethylene is a function of neutron energy. Neutrons produced in (g,n) reactions have a maximum energy equal to the accelerator electron beam energy minus the reaction threshold, but most neutrons are produced at very low energy. In instances where the accelerator energy is less than 15 MeV, the mean neutron energy is <<1 MeV. The value for the neutron TVL in borated polyethylene is about 62 mm [NCRP Report No. 79, Neutron Contamination from Medical Electron Accelerators]. A neutron shield of thickness 200-300 mm will then reduce the neutron flux by a factor of 1700-7000. Gamma Attenuation Shielding Designing appropriate radiation shielding is further complicated since the capture of neutrons in the neutron shielding layer can produce energetic gamma-rays. The low-density hydrogenous materials used for the neutron shielding layer provide very limited shielding of these gamma-rays, which can be most efficiently blocked using a tertiary shield (gamma attenuation shield) comprised of lead, steel or other high density metal. If boron is used as the neutron absorbing material in the neutron attenuation shield, then the gamma-ray flux outside of the shield is dominated by 478 keV gamma-rays resulting from neutron capture by 10B. The TVL for 478 keV gamma-rays in lead is approximately 1.2 cm, and in iron, 5.2 cm. To provide 100-fold attenuation of the neutron-induced gamma-ray dose-rate would require a thickness of approximately 2.5 cm of lead or 10 cm of iron. The mass of iron shielding required to produce this level of attenuation would be about 3 times greater than the mass of lead shielding. Consequently, lead is the preferred choice for the gamma attenuation shield. Member for Inserting and Removing Samples A mechanism for rapidly inserting and removing samples from the vicinity of the X-ray source is desired. This is particularly true for short-lived activation reactions such as formation of the 197Au meta-state which has a half-life of 7.73 s. The layered shield includes a sleeve, or a sample access channel, which is substantially straight. The plug 140 completely fills the sample access channel when it is inserted and provides the means for inserting and removing samples as described previously. As illustrated in FIG. 2, the outer profile of the plug 140 is stepped to remove any straight-line paths through which either X-ray or neutron radiation can escape. Advantageously, this allows for larger tolerances to be left between the sides of the plug 140 and the walls of the channel through which the plug passes, simplifying both manufacture and movement of the plug. Determination of Thicknesses of the X-Ray, Neutron and Gamma Attenuation Shields The X-ray attenuation shield thickness in the forward direction is estimated using tabulated TVLs and the desired dose attenuation factor. Consider an accelerator that produces an unshielded dose rate at 1 m from the target in the forward direction of R Sv/min. Suppose that the desired, shielded dose rate at the closest personnel-accessible point at distance d from the target is r microSv/hour. For a lead X-ray attenuation shield where the TVL for Bremsstrahlung radiation is independent of the accelerator energy over at least the energy range 4-25 MeV, the shielding thickness t is given by:t=TVL×log10[(R×60×106)/(rd2)] (1) For example, consider a LINAC producing a maximum unshielded dose rate of 160 Sv/min. If the closest accessible point is 1 m from the target and the desired shielded dose rate is 2.5 microSv/hour, then t=9.8 TVL. Substituting the tabulated value of 57 mm for TVL yields t=560 mm. The determination of the optimum X-ray attenuation shield thickness at different angles is a more complex calculation, as it depends not just on the angular profile of X-ray emission from the source, but also on the processes of X-ray scattering and absorption inside the shielding. The inventor has determined empirically that for accelerator sources producing X-rays with end-point energies in the range 8-14 MeV, X-ray attenuation shielding thicknesses within the range of 60-80% (and more preferably 75%) and within the range of 25-50% (and more preferably 50%) of the thickness in the forward direction are suitable at angles of 90° and 180° to the electron beam respectively. For the example under consideration, an X-ray attenuation shield thickness of 420 mm is required at an angle of 90°, and a thickness of about 280 mm is required at an angle of 180°. Within these overall requirements on shield thickness, the detailed configuration of the shielding can be most conveniently optimised using a radiation transport computer code, such as a Monte Carlo simulation. The simulation code can be used to model the production, scattering and absorption of X-rays, and to record the simulated dose rate at different positions throughout the model. The shielding configuration can then be optimised to achieve the desired dose rate at all points on the outer surface of the shield. General-purpose Monte Carlo simulation codes such as EGS, MCNP and GEANT are readily available. Determination of the thickness of the neutron attenuation shield depends on the rate of production of neutrons, which is a strong function of the accelerator end-point energy. Neutron production can occur in the accelerator target, in the irradiated sample, and in the X-ray attenuation shield. Neutron production data are supplied by manufacturers of many accelerator systems. They can also be measured experimentally, or calculated using computer simulation codes. FIG. 3 plots the neutron dose rate per unit forward-directed X-ray dose for an accelerator with a tungsten target and lead X-ray attenuation shielding. The electron accelerator operating energy, and hence the X-ray end-point energy is varied between 8 and 14 MeV. The results were determined by the inventor using a computer simulation of X-ray transport and neutron production, performed using the MCNP Monte Carlo code. Returning to the example of a LINAC producing an unshielded forward X-ray dose rate of 160 Sv/min, if the LINAC operating energy is 8.5 MeV, then the corresponding neutron dose rate will be approximately 160×2×10−6 Sv/min=3.2×104 Sv/min. If it is desired to reduce this dose rate to 2.5 microSv/hr at a distance of 1 m, then equation 1 can be used to determine that t=3.9 TVL. With a TVL of 62 mm for low energy neutrons, the corresponding shielding thickness is 240 mm. As neutron production is a function of LINAC energy, the designed thickness should be calculated for the envelope of operating energies/dose-rate outputs for the application in question, and the largest thickness selected. As neutron production is approximately isotropic, a similar shielding thickness is required in all directions. If the design of the electron accelerator requires a substantial cavity to house the accelerating structure, such that the portion of the shield in a backwards direction is significantly further from the target than the portion in a forward direction, then equation 1 predicts that a reduced shielding thickness may be acceptable in the backward direction, due to the larger value of d2. A coupled photon-neutron Monte Carlo simulation can be used to optimise the detailed design of the neutron attenuation shield. A model of the X-ray attenuation shield and neutron attenuation shield is created, and X-rays and X-ray induced neutrons tracked through the model. The neutron dose rate is then recorded at points on the surface of the neutron attenuation shield. The thickness of the neutron attenuation shield can be adjusted to ensure that this outer surface approximately coincidences with a neutron isodose contour at the desired dose-rate level. As the production of neutron-induced gamma-rays is proportional to the neutron flux, and the respective thicknesses of the neutron attenuation shield and the gamma attenuation shield required to reduce the neutron and gamma-ray fluxes to acceptable levels are both proportional to the logarithm of the flux reduction factor, the required thickness of the gamma attenuation shield is proportional to the optimised thickness of the neutron attenuation shield. In the case that the neutron attenuation shield is made from polyethylene containing 5% boron by weight, and the gamma attenuation shield is made from lead, the inventor has determined that the optimal thickness of the gamma attenuation shield is 0.1 times the thickness of the secondary polyethylene layer. For example, if the thickness of the neutron attenuation shield in a particular location is 300 mm, then the optimal thickness of the gamma attenuation shield at this position is 30 mm. If the composition of the neutron or gamma attenuation shields are changed, a different constant of proportionality can be determined, for example through the use of Monte Carlo simulation. The embodiment herein described has the advantage in that it can provide GAA services in a compact, relocatable format. The embodiment herein described allows an 8 kW, 8-14 MeV LINAC-based X-ray source to be deployed in the footprint of a standard 20′ shipping container. With the addition of additional container(s) housing sample handling and radiation detection systems, an entire GAA facility can be constructed in a factory and then rapidly transported and set up in any desired location. This is particularly advantageous when it is desired to set up a minerals analysis lab at a remote location such as a mining site. Embodiments of the invention provide radiation shielding designed for use around a high-energy X-ray source in such a way as to reduce the size and weight of the shielding compared to existing designs. Advantageously, reducing the size and weight to be consistent with the allowed parameters for a standard 20′ shipping container permits easier installation of high-energy X-ray equipment. Whilst embodiments of the invention have been described as being particularly applicable to fields requiring the analysis of elements in mineral samples, the invention is additionally applicable to applications including radiography, cargo screening, fissionable material detection and sterilisation. In essence, the invention is application to any application requiring the deployment of X-ray sources operable at sufficiently high-energy to produce neutrons. Whilst not illustrated, it should be appreciated that to enable maintenance of the accelerator, the apparatus will in most circumstances be configured to enable access to the accelerator. The apparatus may therefore be configured with doors in the vicinity of the accelerator. In one instance the apparatus may be configured with doors situated at the rear end of the accelerator immediately behind the accelerator permit this access. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
	summary
	description	None. This invention was not developed in conjunction with any Federally sponsored contract. Not applicable. Non-patent literature “Tivoli Composite Application Manager for Response Time Tracking Administrator's Guide” Version 6.1, updated January, 2007, published by International Business Machines Corp., Armonk, N.Y., and non-patent literature “Technical Standard: Systems Management: Application Response Measurement (ARM) API” published in July, 1998, by The Open Group, Berkshire, UK, is incorporated by reference herein in its entirety. 1. Field of the Invention The present invention relates generally to systems and methods for simulating complex client-server transactions which mimic real transactions during realistic time periods and initiated from realistic geographies over actual network topologies. 2. Background of the Invention Whereas the determination of a publication, technology, or product as prior art relative to the present invention requires analysis of certain dates and events not disclosed herein, no statements made within this Background of the Invention shall constitute an admission by the Applicants of prior art unless the term “Prior Art” is specifically stated. Otherwise, all statements provided within this Background section are “other information” related to or useful for understanding the invention. Many online commerce services are provided in a generalized client-server arrangement wherein client devices are interconnected to one or more server systems via one or more computer networks. The client devices, such as personal computers and web-enabled cell phones, are often geographically separated from the server(s), such that when a transaction, such as booking a flight reservation, ordering a book from an online bookstore, or accessing an online bank account, is performed, many modules of software on the client and at the server(s) are executed, and many links of network, including protocol conversions, error corrections, etc., are utilized. As application programs on servers become more and more complex re-using modules of software from other programs, as client devices become more capable and thus more complex in their own configurations, and as networks become more interconnected and advanced, it becomes increasing likely that a problem or error will occur during such a transaction. Similarly, it has become increasingly more difficult to determine the source of each error, to replicate each error, and to correct each error. Many tools have been developed to simulate user transactions in client-server arrangements, both for lab use, and for use in the field. However, many problems still remain elusive due to limitations of these tools and the technologies they employ, which continues to result in high labor costs and high loss-of-opportunity costs when a user is unable to complete a commercial transaction. A system or method which accesses or otherwise receives collected performance data for at least one server application, where the server application is capable of performing a plurality of transactions with client devices and the client devices are geographically dispersed from the server in known geographical locales, which automatically determines from the performance data which of the transactions are utilized by users of the client devices, which selects utilized transactions according to at least one pre-determined selection criteria, which automatically generates a transaction playback script for each of the selected transactions substituting test information in place of user-supplied or user-unique information in the transactions, which designates each script for execution from a geographical locale corresponding to the locale of the clients which execute the utilized transactions, which deploys the playback scripts to robotic agents geographically co-located with client devices according to the locale designation, and which executes the playback scripts. The inventors of the present invention have recognized and solved problems previously unrecognized by others in the art of for simulating complex client-server transactions which mimic real transactions during realistic time periods and initiated from realistic geographies over actual network topologies. Existing monitoring agents in transaction-based client-server arrangements are able to be deployed to remote agents, and are able to execute a sequence of transactions from those remote clients to exercise a server or server application. This operates not only the software and hardware functions of the server(s) and the client(s), but also exercises the network topology which exists between the servers and the clients. Periodically executing these transactions by the client-robot allows the users and the suppliers to verify that quality of service is consistent, and to detect problems. However, these robotic transaction sequences have been manually designed up to this point. This requires a user or administrator to determine from his or her own best knowledge which transactions are most important, and then to know every detail of each step of the transaction to complete. For example, to exercise a portion of an online banking application, the sequence which must be known by an administrator wishing to write a robot exercise script may include the steps of go to a login page, enter a username, enter a password, click on “login”, click on “view account details”, click on “sort by date of account item”, enter a starting date, enter an ending date, etc. It has been recognized by the inventors of the present invention that the transaction monitoring data collected by an application response monitoring can be used to automatically determine which transactions are most important or most utilized and when those transactions are typically accessed, to automatically generate a robotic script according to the determined most important transactions, to automatically deploy the scripts to robotic agents which are located in geographical locales representing the clients from which their transactions are typically performed, and to execute those scripts to robotically exercise the client-server arrangement in the manners most important at the most appropriate, realistic times. One such application response monitoring system is the IBM Tivoli Composite Application Monitor (“ITCAM”) for Response Time Tracking (“RTT”), from which transaction performance data can be obtained using the well-known Application Response Monitor (“ARM”) application programming interface (“API”). However, the present invention is not limited to implementation with, or integration to ITCAM through ARM, whereas it can be utilized in conjunction with any suitable application performance monitoring system. While one embodiment utilizes the ARM API to collect monitoring data, other alternatives exist. For example, another component known as IBM Tivoli™ Web Response Monitor (“WRM”) “sniffs” IP packets to collect this real user web traffic, and writes that information into a log file. So, the invention can alternatively read and interpret an WRM log. Alternative products and tools from other suppliers can be used for this function, as well. Further, IBM Tivoli's more recent version of ITCAM for RTT, known as ITCAM for Response Time v6.2 (“ITCAM for RT”), may be alternatively employed. Suitable Computing Platform Whereas at least one embodiment of the present invention incorporates, uses, or operates on, with, or through one or more computing platforms, and whereas many devices, even purpose-specific devices, are actually based upon computing platforms of one type or another, it is useful to describe a suitable computing platform, its characteristics, and its capabilities. Therefore, it is useful to review a generalized architecture of a computing platform which may span the range of implementation, from a high-end web or enterprise server platform, to a personal computer, to a portable PDA or wireless phone. In one embodiment of the invention, the functionality including the previously described logical processes are performed in part or wholly by software executed by a computer, such as personal computers, web servers, web browsers, or even an appropriately capable portable computing platform, such as personal digital assistant (“PDA”), web-enabled wireless telephone, or other type of personal information management (“PIM”) device. In alternate embodiments, some or all of the functionality of the invention are realized in other logical forms, such as circuitry. Turning to FIG. 2a, a generalized architecture is presented including a central processing unit (21) (“CPU”), which is typically comprised of a microprocessor (22) associated with random access memory (“RAM”) (24) and read-only memory (“ROM”) (25). Often, the CPU (21) is also provided with cache memory (23) and programmable FlashROM (26). The interface (27) between the microprocessor (22) and the various types of CPU memory is often referred to as a “local bus”, but also may be a more generic or industry standard bus. Many computing platforms are also provided with one or more storage drives (29), such as hard-disk drives (“HDD”), floppy disk drives, compact disc drives (CD, CD-R, CD-RW, DVD, DVD-R, etc.), and proprietary disk and tape drives (e.g., Iomega Zip™ and Jaz™, Addonics SuperDisk™, etc.). Additionally, some storage drives may be accessible over a computer network. Many computing platforms are provided with one or more communication interfaces (210), according to the function intended of the computing platform. For example, a personal computer is often provided with a high speed serial port (RS-232, RS-422, etc.), an enhanced parallel port (“EPP”), and one or more universal serial bus (“USB”) ports. The computing platform may also be provided with a local area network (“LAN”) interface, such as an Ethernet card, and other high-speed interfaces such as the High Performance Serial Bus IEEE-1394. Computing platforms such as wireless telephones and wireless networked PDA's may also be provided with a radio frequency (“RF”) interface with antenna, as well. In some cases, the computing platform may be provided with an infrared data arrangement (“IrDA”) interface, too. Computing platforms are often equipped with one or more internal expansion slots (211), such as Industry Standard Architecture (“ISA”), Enhanced Industry Standard Architecture (“EISA”), Peripheral Component Interconnect (“PCI”), or proprietary interface slots for the addition of other hardware, such as sound cards, memory boards, and graphics accelerators. Additionally, many units, such as laptop computers and PDA's, are provided with one or more external expansion slots (212) allowing the user the ability to easily install and remove hardware expansion devices, such as PCMCIA cards, SmartMedia cards, and various proprietary modules such as removable hard drives, CD drives, and floppy drives. Often, the storage drives (29), communication interfaces (210), internal expansion slots (211) and external expansion slots (212) are interconnected with the CPU (21) via a standard or industry open bus architecture (28), such as ISA, EISA, or PCI. In many cases, the bus (28) may be of a proprietary design. A computing platform is usually provided with one or more user input devices, such as a keyboard or a keypad (216), and mouse or pointer device (217), and/or a touch-screen display (218). In the case of a personal computer, a full size keyboard is often provided along with a mouse or pointer device, such as a track ball or TrackPoint™. In the case of a web-enabled wireless telephone, a simple keypad may be provided with one or more function-specific keys. In the case of a PDA, a touch-screen (218) is usually provided, often with handwriting recognition capabilities. Additionally, a microphone (219), such as the microphone of a web-enabled wireless telephone or the microphone of a personal computer, is supplied with the computing platform. This microphone may be used for simply reporting audio and voice signals, and it may also be used for entering user choices, such as voice navigation of web sites or auto-dialing telephone numbers, using voice recognition capabilities. Many computing platforms are also equipped with a camera device (2100), such as a still digital camera or full motion video digital camera. One or more user output devices, such as a display (213), are also provided with most computing platforms. The display (213) may take many forms, including a Cathode Ray Tube (“CRT”), a Thin Flat Transistor (“TFT”) array, or a simple set of light emitting diodes (“LED”) or liquid crystal display (“LCD”) indicators. One or more speakers (214) and/or annunciators (215) are often associated with computing platforms, too. The speakers (214) may be used to reproduce audio and music, such as the speaker of a wireless telephone or the speakers of a personal computer. Annunciators (215) may take the form of simple beep emitters or buzzers, commonly found on certain devices such as PDAs and PIMs. These user input and output devices may be directly interconnected (28′, 28″) to the CPU (21) via a proprietary bus structure and/or interfaces, or they may be interconnected through one or more industry open buses such as ISA, EISA, PCI, etc. The computing platform is also provided with one or more software and firmware (2101) programs to implement the desired functionality of the computing platforms. Turning to now FIG. 2b, more detail is given of a generalized organization of software and firmware (2101) on this range of computing platforms. One or more operating system (“OS”) native application programs (223) may be provided on the computing platform, such as word processors, spreadsheets, contact management utilities, address book, calendar, email client, presentation, financial and bookkeeping programs. Additionally, one or more “portable” or device-independent programs (224) may be provided, which must be interpreted by an OS-native platform-specific interpreter (225), such as Java™ scripts and programs. Often, computing platforms are also provided with a form of web browser or micro-browser (226), which may also include one or more extensions to the browser such as browser plug-ins (227). The computing device is often provided with an operating system (220), such as Microsoft Windows™, UNIX, IBM OS/2™, IBM AIX™, open source LINUX, Apple's MAC OS™, or other platform specific operating systems. Smaller devices such as PDA's and wireless telephones may be equipped with other forms of operating systems such as real-time operating systems (“RTOS”) or Palm Computing's PalmOS™. A set of basic input and output functions (“BIOS”) and hardware device drivers (221) are often provided to allow the operating system (220) and programs to interface to and control the specific hardware functions provided with the computing platform. Additionally, one or more embedded firmware programs (222) are commonly provided with many computing platforms, which are executed by onboard or “embedded” microprocessors as part of the peripheral device, such as a micro controller or a hard drive, a communication processor, network interface card, or sound or graphics card. As such, FIGS. 2a and 2b describe in a general sense the various hardware components, software and firmware programs of a wide variety of computing platforms, including but not limited to personal computers, PDAs, PIMs, web-enabled telephones, and other appliances such as WebTV™ units. As such, we now turn our attention to disclosure of the present invention relative to the processes and methods preferably implemented as software and firmware on such a computing platform. It will be readily recognized by those skilled in the art that the following methods and processes may be alternatively realized as hardware functions, in part or in whole, without departing from the spirit and scope of the invention. In another embodiment of the invention, logical processes according to the invention and described herein are encoded on or in one or more computer-readable media. Some computer-readable media are read-only (e.g. they must be initially programmed using a different device than that which is ultimately used to read the data from the media), some are write-only (e.g. from the data encoders perspective they can only be encoded, but not read simultaneously), or read-write. Still some other media are write-once, read-many-times. Some media are relatively fixed in their mounting mechanisms, while others are removable, or even transmittable. All computer-readable media form two types of systems when encoded with data and/or computer software: (a) when removed from a drive or reading mechanism, they are memory devices which generate useful data-driven outputs when stimulated with appropriate electromagnetic, electronic, and/or optical signals; and (b) when installed in a drive or reading device, they form a data repository system accessible by a computer. FIG. 4a illustrates some computer readable media including a computer hard drive (40) having one or more magnetically encoded platters or disks (41), which may be read, written, or both, by one or more heads (42). Such hard drives are typically semi-permanently mounted into a complete drive unit, which may then be integrated into a configurable computer system such as a Personal Computer, Server Computer, or the like. Similarly, another form of computer readable media is a flexible, removable “floppy disk” (43), which is inserted into a drive which houses an access head. The floppy disk typically includes a flexible, magnetically encodable disk which is accessible by the drive head through a window (45) in a sliding cover (44). A Compact Disk (“CD”) (46) is usually a plastic disk which is encoded using an optical and/or magneto-optical process, and then is read using generally an optical process. Some CD's are read-only (“CD-ROM”), and are mass produced prior to distribution and use by reading-types of drives. Other CD's are writable (e.g. “CD-RW”, “CD-R”), either once or many time. Digital Versatile Disks (“DVD”) are advanced versions of CD's which often include double-sided encoding of data, and even multiple layer encoding of data. Like a floppy disk, a CD or DVD is a removable media. Another common type of removable media are several types of removable circuit-based (e.g. solid state) memory devices, such as Compact Flash (“CF”) (47), Secure Data (“SD”), Sony's MemoryStick, Universal Serial Bus (“USB”) FlashDrives and “Thumbdrives” (49), and others. These devices are typically plastic housings which incorporate a digital memory chip, such as a battery-backed random access chip (“RAM”), or a Flash Read-Only Memory (“FlashROM”). Available to the external portion of the media is one or more electronic connectors (48, 400) for engaging a connector, such as a CF drive slot or a USB slot. Devices such as a USB FlashDrive are accessed using a serial data methodology, where other devices such as the CF are accessed using a parallel methodology. These devices often offer faster access times than disk-based media, as well as increased reliability and decreased susceptibility to mechanical shock and vibration. Often, they provide less storage capability than comparably priced disk-based media. Yet another type of computer readable media device is a memory module (403), often referred to as a SIMM or DIMM. Similar to the CF, SD, and FlashDrives, these modules incorporate one or more memory devices (402), such as Dynamic (“DRAM”), mounted on a circuit board (401) having one or more electronic connectors for engaging and interfacing to another circuit, such as a Personal Computer motherboard. These types of memory modules are not usually encased in an outer housing, as they are intended for installation by trained technicians, and are generally protected by a larger outer housing such as a Personal Computer chassis. Turning now to FIG. 4b, another embodiment option (405) of the present invention is shown in which a computer-readable signal is encoded with software, data, or both, which implement logical processes according to the invention. FIG. 4b is generalized to represent the functionality of wireless, wired, electro-optical, and optical signaling systems. For example, the system shown in FIG. 4b can be realized in a manner suitable for wireless transmission over Radio Frequencies (“RF”), as well as over optical signals, such as InfraRed Data Arrangement (“IrDA”). The system of FIG. 4b may also be realized in another manner to serve as a data transmitter, data receiver, or data transceiver for a USB system, such as a drive to read the aforementioned USB FlashDrive, or to access the serially stored data on a disk, such as a CD or hard drive platter. In general, a microprocessor or microcontroller (406) reads, writes, or both, data to/from storage for data, program, or both (407). A data interface (409), optionally including a digital-to-analog converter, cooperates with an optional protocol stack (408), to send, receive, or transceive data between the system front-end (410) and the microprocessor (406). The protocol stack is adapted to the signal type being sent, received, or transceived. For example, in a Local Area Network (“LAN”) embodiment, the protocol stack may implement Transmission Control Protocol/Internet Protocol (“TCP/IP”). In a computer-to-computer or computer-to-peripheral embodiment, the protocol stack may implement all or portions of USB, “FireWire”, RS-232, Point-to-Point Protocol (“PPP”), etc. The system's front-end, or analog front-end, is adapted to the signal type being modulated, demodulate, or transcoded. For example, in an RF-based (413) system, the analog front-end comprises various local oscillators, modulators, demodulators, etc., which implement signaling formats such as Frequency Modulation (“FM”), Amplitude Modulation (“AM”), Phase Modulation (“PM”), Pulse Code Modulation (“PCM”), etc. Such an RF-based embodiment typically includes an antenna (414) for transmitting, receiving, or transceiving electromagnetic signals via open air, water, earth, or via RF wave guides and coaxial cable. Some common open air transmission standards are BlueTooth, Global Services for Mobile Communications (“GSM”), Time Division Multiple Access (“TDMA”), Advanced Mobile Phone Service (“AMPS”), and Wireless Fidelity (“Wi-Fi”). In another example embodiment, the analog front-end may be adapted to sending, receiving, or transceiving signals via an optical interface (415), such as laser-based optical interfaces (e.g. Wavelength Division Multiplexed, SONET, etc.), or Infra Red Data Arrangement (“IrDA”) interfaces (416). Similarly, the analog front-end may be adapted to sending, receiving, or transceiving signals via cable (412) using a cable interface, which also includes embodiments such as USB, Ethernet, LAN, twisted-pair, coax, Plain-old Telephone Service (“POTS”), etc. Signals transmitted, received, or transceived, as well as data encoded on disks or in memory devices, may be encoded to protect it from unauthorized decoding and use. Other types of encoding may be employed to allow for error detection, and in some cases, correction, such as by addition of parity bits or Cyclic Redundancy Codes (“CRC”). Still other types of encoding may be employed to allow directing or “routing” of data to the correct destination, such as packet and frame-based protocols. FIG. 4c illustrates conversion systems which convert parallel data to and from serial data. Parallel data is most often directly usable by microprocessors, often formatted in 8-bit wide bytes, 16-bit wide words, 32-bit wide double words, etc. Parallel data can represent executable or interpretable software, or it may represent data values, for use by a computer. Data is often serialized in order to transmit it over a media, such as a RF or optical channel, or to record it onto a media, such as a disk. As such, many computer-readable media systems include circuits, software, or both, to perform data serialization and re-parallelization. Parallel data (421) can be represented as the flow of data signals aligned in time, such that parallel data unit (byte, word, d-word, etc.) (422, 423, 424) is transmitted with each bit D0-Dn being on a bus or signal carrier simultaneously, where the “width” of the data unit is n−1. In some systems, D0 is used to represent the least significant bit (“LSB”), and in other systems, it represents the most significant bit (“MSB”). Data is serialized (421) by sending one bit at a time, such that each data unit (422, 423, 424) is sent in serial fashion, one after another, typically according to a protocol. As such, the parallel data stored in computer memory (407, 407′) is often accessed by a microprocessor or Parallel-to-Serial Converter (425, 425′) via a parallel bus (421), and exchanged (e.g. transmitted, received, or transceived) via a serial bus (421′). Received serial data is converted back into parallel data before storing it in computer memory, usually. The serial bus (421′) generalized in FIG. 4c may be a wired bus, such as USB or Firewire, or a wireless communications medium, such as an RF or optical channel, as previously discussed. In these manners, various embodiments of the invention may be realized by encoding software, data, or both, according to the logical processes of the invention, into one or more computer-readable mediums, thereby yielding a product of manufacture and a system which, when properly read, received, or decoded, yields useful programming instructions, data, or both, including, but not limited to, the computer-readable media types described in the foregoing paragraphs. General Arrangements of Monitored Transaction Processing Systems Whereas the generalized embodiment of the present invention utilizes, cooperates with, and operates on or within a transaction processing client-server arrangement, the following figures and paragraphs provide definitions and fundamentals of an embodiment based upon an IBM Tivoli Composite Application Manager for Response Time Tracking (“ITCAM for RTT”) platform. Other embodiments of the present invention are possible using alternative platforms to ITCAMM for RTT, and it is within the skill of those in the art to adapt the teachings made herein to such alternate embodiments. Further, while most embodiments described in the following paragraphs will be set forth relative to an exemplary embodiment using Application Response Monitoring (“ARM”) and/or Web Response Monitor (“WRM”) used with standard hyper text transfer protocol (“HTTP”), it will be readily recognized by those skilled in the art that alternative embodiments within the scope of the invention can utilize other protocols, monitoring schemes, and programming languages, including but not limited to web services over HTTP, Java Messaging Service (“JMS”), Message Queue series (“MQ”) messages, Structured Query Language (“SQL”), Java Database Connectivity (“JDBC”), Remote Method Invocation (“RMI”), or any other suitable network based protocol. ITCAM for RTT. Much of the following information is presented from the Tivoli Composite Application Manager for Response Time Tracking Administrator's Guide, Version 6.1, updated January, 2007, which is incorporated by reference herein. ITCAM for RTT measures the service level delivered to end users of client devices when they perform transactions with a server system. ITCAM monitors the availability and response time that end users experience at the client desktop or user interface. It can be used with a wide range of web-based, e-business, and Microsoft Windows™ applications that run across many different environments. In the alternative embodiment employing the IBM Tivoli™ Web Response Monitor component previously mention, real IP traffic from a real to a web server is monitored and recorded as real user transactions against a web application. For example, each URL to a web application is a transaction in this case. Also, if the URL has forms to submit via GET or POST commands, then the client-provided information is also recorded, and the ITCAM administrator would define what the robotic agent should provide as the input in place of the real customer data. For example, if the real client provided his login ID and password, the robot script is configured not to log in as a real user (with a real user ID and password), because the next set of collected transaction data would include that regarding real user transactions and information about the robotic transactions. Other such modifications may be needed against the automatically generated script, as certain cases arise. If the service delivered to end users degrades, ITCAM recognizes this and alerts a system administrator to the problem. ITCAM for RTT measures the end-user experience by monitoring the round trip response time of transactions originating at the client desktop, and it integrates with the IBM Tivoli Data Warehouse so collected data can be stored for historical analysis and long-term planning. ITCAM for RTT runs in both a single-server environment and in a clustered environment, and monitors what area of the Web or what transactions an administrator wants to investigate, the type of information to be collected, the thresholds that tell the software when and how to contact an administrator if performance degrades, and when the administrator wants the monitoring to occur. For the purposes of the present disclosure, a “transaction” will refer to an exchange of data and commands that accomplishes a particular action or result. A transaction can occur between a workstation and a program, two workstations, or two programs. ITCAM for RTT recognizes a transaction at the point when it first comes in contact with monitoring instrumentation. This point of contact is called the “edge”. The comprehensive transaction decomposition environment shows the “path” of problem transactions, isolates the source of problems, and launches the IBM Tivoli Monitoring Web Health Console or IBM Tivoli Composite Application Management for WebSphere™ to identify the problem so an administrator can restore good response time. A “subtransaction” will refer to an individual step (such as a single page request) in the overall transaction. ITCAM for RTT uses “monitors” to collect information and to forward collected information. Monitors are typically software programs loaded on a client system, on a server system, or on multiple clients and servers. There are a variety of monitors available in the ITCAM for RTT product, which allow an administrator to (a) recognize problems before they occur by accessing the health of business components with robotic monitors, and (b) pinpoint problems as they occur with listening monitors that monitor every step of real customer transactions. “Robotic monitors” run typical customer transactions from a robotic workstation and collect performance data. The performance data helps determine whether a transaction is performing as expected and exposes problem areas of the Web and application environment. “Listening monitors” help pinpoint problems as they occur by monitoring every step of real customer transactions. Listening monitors collect performance data and produce detailed information about transaction performance times to measure the performance of subtransactions. The monitoring software writes the collected “performance data” to disk. An administrator can specify whether to save aggregate data (to conserve system resources and to view fewer data points) or both aggregate and instance data. The software also correlates the collected data. Performance data can be categorized as follows: (a) Hourly Average data (also called Aggregate data), which averages all response times detected over a one-hour period to provide a view of the overall performance of a transaction; (b) Instance data, which consists of response times that are collected every time the transaction runs; (c) Instance on Failure data, which is automatically collected if a transaction exceeds specified thresholds; and (d) Correlation data, which tracks hierarchical relationships among transactions and associates transactions with nested subtransactions. ITCAM for RTT can be deployed to a single-server environment as well as to clustered server environments. Turning to FIG. 5, a general arrangement of components, networks, and users of client computers (“client, clients”) to perform transactions with server systems (“server, servers”) in a “single server” environment is shown. A typical infrastructure includes a Web tier with several Web servers hosting the static content for an application and an application tier hosting the dynamic content. The Web tier typically uses a load balancer to distribute application requests among Web servers. Each Web server can use a plug-in to direct requests for dynamic content from the Web server to the back-end application server. The application server provides many services to the application running on it, including data persistence, access to back-end databases, access to messaging infrastructures, security, and access to legacy systems. Management agents (50, 52, 56) run on computers across the environment, and identify transactions that might need monitoring, collect performance data by running regularly scheduled listening and robotic monitors, and send generated events to the management server. Each listening and playback component is instrumented to retrieve data using application response monitoring (“ARM”) standards, such as the Open Group's Application Response Measurement (ARM) Application Programming Interface (“API”), dated July 1998, which is incorporated by reference herein. Store and forward agents (51, 53) are located in the Internet, in a “DMZ”, or in both the Internet and a DMZ. A DMZ is computer or subnetwork between a private Intranet and the public Internet. The store and forward agents (51, 53) provide bidirectional support for a secure connection from the management agents to the management server through a firewall (a) by enabling point-to-point connections between management agents and the management server (54); (b) by enabling management agents to interact with Store and Forward as if Store and Forward were a management server; (c) by routing requests and responses to the correct target; (d) by supporting secure socket layer (“SSL”) communications; and (e) by supporting one-way communications through the firewall. The Management Server (54) is typically located in an Intranet, and it provides centralized management, employing web services to communicate with management agents at regularly scheduled intervals, called the upload interval, such as once an hour. A typical management server includes the following pieces (a) a user interface (55) which provides a way to interact with the monitoring software (e.g. an administrator can access the user interface through a Web browser); (b) a real-time report display to view collected performance data; and (c) an event system which notifies administrators in real time about the status of monitored transactions through reports, e-mail notification, or events sent to the IBM Tivoli Enterprise Console (502) or the simple network management protocol (SNMP). The Management Server also provides access to other system components, such as a relational database management system (“RDBMS”), and Tivoli Data Warehouse (“TDW”), and other well known Tivoli products and systems (TEP, ITM, ITSLA, TBSM), as well as non-Tivoli and non-IBM components. ITCAM for RTT also supports a high number of management agents connected to a single management server deployed to a server cluster, such as a WebSphere cluster, to provide high availability, fault tolerance, and increased scalability. Workload management and distributing requests through load balancers provides scalability in the cluster environment. Each server component can service any request from any management agent in any order. ITCAM for RTT supports “horizontal clustering”, which contains multiple physical machines (nodes), as well as “vertical clustering”, which contains multiple application server instances hosted on the same physical machine (node). Turning to FIG. 6, a representation of a clustered environment is shown having a plurality of management agents (60), and an administrator (61). The Deployment Manager (64), which is part of an “orchestration” layer (62), provides node configuration and management, as well as workload distribution. A Load Balancer (65), also part of orchestration (62), provides load balancing for multiple Application Server nodes (67, 68) by distributing requests to the various nodes. One or more Database Systems (600) act as data repositories, and provide session failover support. And, one or more Lightweight Directory Access Protocol (“LDAP”) systems (601) may be required for purposes such as providing a user registry for security in a horizontal cluster. An application server node (67, 68), such as IBM WebSphere Application Server servers. FIG. 7 provides more details of a clustered node (67) example. A node (67) hosts one or more server instances, and an IBM WebSphere Application Server node agent enables communication with the Deployment Manager (64). A Hyper Text Transfer Protocol (“HTTP”) server, such as an IBM HTTP server (70), provides load balancing (65) for server instances. A Java Messaging Service (“JMS”) agent allows communication (72) between nodes, a database client (73) allows communication to one or more database management systems (600). ARM and Correlation. In one embodiment of the invention, an Application Response Measurement (ARM) API is employed for capturing transaction performance data. The ARM standard describes a common method for integrating enterprise applications as manageable entities and extends enterprise management tools directly to ARM-instrumented applications. ARM provides a way for business applications to pass information about the subtransactions initiated in response to service requests that flow across a network. The ARM API also defines a set of functions for instrumenting an application so the start and stop of important transactions can be identified. This information is used to calculate response times, identify subtransactions, and provide additional data for determining the cause of performance problems. The ARM engine is a multithreaded application, and it exchanges data though an IPC channel with ARM instrumented applications. ARM aggregates collected data to generate useful information and correlates it with other transactions; users specify how thresholds are measured. ARM Correlation maps parent transactions to their respective child transactions across multiple processes and multiple servers. Each monitoring component is ARM-instrumented and generates a correlator. The initial root/parent (or edge) transaction is the only transaction that does not have a parent correlator. The response tracker automatically connects parent correlators with child correlators to trace the path of a distributed transaction through the infrastructure and visualizes the path in topology views. Correlation can be broken into several types or categories: (a) path-based aggregation, which is based upon the origin of the transaction, the first point in the infrastructure that the product detects the transaction, and the parent transaction who called the current transaction as well as the current transaction information (i.e. each subtransaction is aggregated separately whenever it is called on behalf of a different entry point); (b) policy-based correlators, through which monitors can control what percent of the transactions are monitored, as well as how much information is collected for those monitored transactions. (i.e. enabling subtransaction collection of all methods in IBM WebSphere Application Server instead of accepting the default collection of only Servlet, EJB, JMS, and JDBC methods, etc.); (c) instance and aggregated performance statistics, which provides additional metrics and a complete and exact trace of the path taken by a specific transaction; (d) threshold violation initiated trace, which provides dynamic collection of instance data across all systems where a transaction executes; and (e) sibling transaction ordering, which provides the ability to determine the execution order of a set of child transactions relative to each other. The monitoring processes treat periodic average correlation in the following three ways: (a) edge aggregation by pattern, which averages all transactions that match an edge monitor pattern; (b) edge aggregation by transaction name, which uniquely averages each transaction name that matches a monitor's edge pattern, also called “discovery,” because it discovers all the edges that match the specified edge pattern; and (c) aggregation by root/parent/transaction directs each transaction instance to a specific aggregator based upon correlation using the following properties: Origin Host UUID, Root Transaction ID, Parent Transaction ID, and Transaction ID. As previously mentioned, small amounts of data referred to as ARM “correlators” are passed along with the transaction requests and responses in order to enable end-to-end transaction identification and tracking. There are a variety of mechanisms for passing ARM correlators from one application to another or inside the application, including passing the correlator in an HTTP header, in a JMS header, RMI-IIOP context, and SOAP headers. Transactions entering the J2EE Application Server might already have an associated correlator if the transaction is monitored by Quality of Service, STI, J2EE instrumentation on another J2EE application server or Rational Robot (Generic Windows), otherwise the correlator contains information that tells this engine and downstream engines to not monitor anything about this transaction. Robotic transaction generation and playback according to the present invention allows a transactional client-server system to realistically, albeit automatically, simulate end user experiences, such as interactions with an online bookstore, online banking, travel reservation, etc. Traditionally, it has been difficult to manually generate simulated transactions for robotic playback because (1) it's difficult to know what software processes should be monitored, (2) it is time consuming to record simulated transactions and keep them updated over time to make sure they are simulating current user requests even after the software system is updated, and (3) it's difficult to know the geographic location at which to place robotic monitors to playback the transactions, to get an accurate view of world-wide end user experience. Having recognized this problem, the inventors of the present invention have developed a system and process which analyzes previously collected transaction monitoring data, such as log files generated by an HTTP server, web and application server configuration files and monitoring data from transaction tracking tools, and to determine the transactions that are being accessed most by end users, as illustrated in FIG. 1a by: (a) determining (100) which transactions are important to monitor based on frequency of usage, business value of the transaction, meeting of Service Level Agreement (“SLA”) requirements, transactions involving Universal Resource Locators (“URL”) which are designated as important, or other criteria, by accessing and analyzing server transaction logs (101) and optionally ARM logs and statistics (102); (b) automatically configuring (103), if necessary, one or more monitoring agents (104), which monitor the targeted servers and applications (109), to collect actual transaction details of the determined most important transaction types, optionally during specific transaction periods; (c) based upon collected transaction logs (101), and optionally upon ARM agent information (102), WRM data or transaction data from another source, automatically generating (105) one or more simulated transaction scripts that, when “played back” by a client robot, will exercise the most important requests to be monitored, preferably using simulated user accounts and passwords if applicable; and (d) deploying (106) transaction playback robots (107) and the generated transaction scripts to playback (108) the simulated transactions at the appropriate geographic locations with the appropriate schedules so that real end user experience can be accurately assessed of the monitored servers and applications (109). In an advanced embodiment of the invention, the process as shown in FIG. 1a is supplemented, as shown in FIG. 1b, by the addition of a automatically detecting (110) changes in the targeted servers and applications (109), and responsive (111) to a change, automatically updating the robotic simulated transactions to prevent interruption of monitoring and, optionally, updating the monitoring agent configurations (100-105). For example, consider a typical Apache HTTP Web Server that is to be monitored, such as an online bookstore. Such a server generates several logs containing transaction information such as the Universal Resource Locators (“URLs”) of the web pages requested over a period of time, the time of each request, the Internet Protocol (“IP”) address of the requesting client, and any errors encountered while servicing then requests, as shown in Table 1. TABLE 1Example HTTP Server Log for an Online Bookstore<URL requested><sourceIP><date><time><error>;. . .</childrens_features>,<239.00.134.279>,<04152007>,<16:22:03>,<OK>;</self_improvement>,<456.687.934.111>,<04152007>,<16:23:19>,<OK>;</discounts_clearances>,<987.456.333.321>,<04152007>,<16:23:24>,<404>;</travel/international/spain>,<123.456.789.555>,<04152007>,<16:22:03>,<OK >;. . . In this example, a first “hit” or page request to the children's features page of the bookstore website was made on Apr. 15, 2007, at 3:33:03 p.m., from a clients IP address of 239.00.134.279, and the result was that the page was served successfully. The third entry, though, shows a request for a “discounts and clearances” page, which was not successfully delivered to the client at IP address 987.456.333.321 because a 404 error (page not found) occurred. This would indicate a server-side error (e.g. a dead end link to this page), which needs to be addressed. Finally, the last entry in this example shows a deeper link into the web site as an access to a page about travel to Spain. This information is shown in chronological order, but may in practice be received or accessed in any order, sorted by any field (e.g. sorted by IP address, by time, by requested URL, by result, etc.). There are well-known methods for determining the approximate geography of the requesting client because of the methodology employed in assigning and sub-netting IP addresses. Other known methods, such as tracking a user session when the user's location is known, or retrieving a cookie from the client device, can be employed to determine geographic region, area or location, as well. In one embodiment, such a method is employed to determine the geography of each requesting client, and optionally, to annotate the log information as follows in Table 2. TABLE 2Example Annotated HTTP Server Log for an Online Bookstore<URL requested><sourceIP+location><date><time><error>;. . .</childrens_features>,<Houston-TX>,<04152007>,<16:22:03>,<OK>;</self_improvement>,<Atlanta-GA>,<04152007>,<16:23:19>,<OK>;</discounts_clearances>,<Idaho><04152007>,<16:23:24>,<404>;</travel/international/spain>,<Chicago-IL>,<04152007>,<16:22:03>,<OK>;. . . According to the present invention, this data is analyzed to determine information such as the most commonly used parts of the web application (e.g. URLs with the most requests), time periods of use, and the most commonly used parts of the application by client geography as known by the IP address or some other means (e.g. cookie, client registration, username, etc.). For example, consider an expanded example of Table 3. TABLE 3Example Annotated HTTP Server Log for an Online Bookstore<URL requested><sourceIP+location><date><time><error>;. . .</en/childrens_features>,<Houston-TX>,<04152007>,<16:22:03>,<OK>;</en/self_improvement>,<Atlanta-GA>,<04152007>,<16:23:19>,<OK>;</en/discounts_clearances>,<Idaho>,<04152007>,<16:23:24>,<404>;</en/ travel/international/spain>,<Chicago-IL>,<04152007>, <16:22:03>,<OK>;. . .</jp/childrens_features>,<Tokyo-JP>,<04152007>,<20:12:03>,<OK>;</ jp/self_improvement>,< Yokohama-JP>,<04152007>,<20:13:19>,<OK>;</ jp/discounts_clearances>,< Osaka-JP>,<04152007>,<20:13:27>,<404>;</ jp/travel/international/spain>,< Kyoto-JP>,<04152007>,<20:14:03>,<404>;. . . In this example, it is evident due to the arrangement and sorting of the records that a set of English pages (denoted by the “/en” in the URL) is accessed during a system time period around 3:20 p.m., and that a set of Japanese pages (denoted by the “/jp” in the URL) is accessed during a system time period around 10:12 p.m. This is likely due to the different time zones of the source geographies. Also, it can be seen from this set of examples that the Japanese access attempt to the Spanish travel page was unsuccessful, but the equivalent English access was successful earlier in the day, perhaps due to network difficulty or even due to late night, early morning server maintenance inavailability. Additionally, the present invention detects when a URL or portion of an application is updated or changed, which may also be detectable from such logs, as illustrated in Table 4 for a change to the self improvement books page. TABLE 4Example Annotated HTTP Server Log for an Online Bookstore<URL requested><URL-rev-date><sourceIP+location><date><time><error>;. . .</en/childrens_features>,<01012007>,<HoustonTX>,<04152007>,<16:22:03>,<OK>;</en/self_improvement>,<01012007>,<AtlantaGA>,<04152007>,<16:23:19>,<OK>;</en/discounts_clearances>,<01012007><Idaho>,<04152007>,<16:23:24>,<404>;</en/ travel/international/spain>,<01012007><Chicago-IL>,<04152007>,<16:22:03>,<OK>;. . .</en/childrens_features>,<01012007>,<HoustonTX><04162007>,<10:19:03>,<OK>;</en/self_improvement>,<04152007><AtlantaGA>,<04162007>,<10:19:19>,<OK>;</en/discounts_clearances>,<01012007><Idaho>,<04162007>,<10:19:24>,<404>;</en/ travel/international/spain>,<01012007><Chicago-IL>,<04162007>,<10:20:03>,<OK>;. . . According to user selections, the invention then identifies: (a) which URLs are accessed the greatest number of times; (b) which URLs are accessed most often; (c) what time periods each URL is accessed most often; (d) which geographies access each URL the greatest number of times; (e) which geographies access each URL the most often; and (f) optionally, which URLs have recently changed or been updated. Next, in order to capture detailed information needed to simulate an actual transaction, the invention automatically determines any updates needed to existing monitoring agents. In the example of Table 3, monitoring agents in Japan may be configured to collect transaction details during the 10:00 p.m. to 11:00 p.m. period (system time), and monitoring agents in the USA may be configured to capture transaction details during the period of 10:00 a.m. to 4:00 p.m. (system time). These changes are propagated through the normal means of remotely updating the monitoring agents, such as through the control means of ITCAM for RTT. After the collection period has completed, the invention then receives the logged monitor information, and compares the transactions to each other to determine differences between them, such as usernames, passwords, specific list choices, etc. (e.g. user-supplied and user-unique information) These points of differences are then used to remove “real” information from each transaction, and the real information is replaced with test information (e.g. fake usernames, fake passwords, fake list choices which are registered with the server and are valid with respect to the application logical flow). Preferably, an administrator is prompted to show the points of insertion of fake or test-case information, and the administrator is allowed to input or select the replacement information to be utilized in the script. Alternatively, in some embodiments, certain information may be replaced with standardized or pre-determined information. In either case, this results in a transaction sequence which is realistically based on actual steps taken by actual users, but which incorporates non-real user information. It is important to note that due to the automation of the invention, different transaction scripts for different topologies are easily and readily created. For example, if a bookstore's self-help area is most popular from Washington state in the USA, transaction scripts are automatically generated and associated with that geography. But, this area of the online bookstore may be relatively unpopular (and unaccessed) by users in Italy, who frequent the bookstore's art history area much more often. As such, scripts to exercise the self-help area and to exercise the art history area would be created. But, in the next phase of the invention, the scripts are not necessarily uniformly distributed to all robotic agents running on remote clients devices, and they are not necessarily configured to run a uniform times. Instead, the self-help area script would be distributed to the robotic agents running on clients in the Washington state area, while the art history script would be distributed to the robotic agents running on the clients in Italy. And, the self-help scripts would be configured to execute during the periods detected to be the most common times of usage from users in Washington, and likewise, the art history scripts would be configured to be executed during times most often accessed by Italian users. For the purposes of executing tests which closely simulate real transactions, geographic locales and regions are defined in such a manner so as to include at least one available robotic agent. Further, some robotic agents may be defined to fall within two or more regions or locales (e.g. the regions overlap), depending on equipment availability, network topology, security issues, and costs of hardware. In a variation of the present invention, rather than synchronize the execution of the transaction scripts with the detected, actual periods of greatest use of the target URLs and application portions, the scripts can also be programmed to execute during lower or least usage periods. This type of out-of-phase execution is useful for load testing an application at times which are less critical to serving the actual business objectives of the system. Alternatively, the scripts can be programmed to execute at times evenly throughout a day or week, thus creating a background testing scenario. In another variation of the present invention, when a change to a targeted URL is detected, such as a revision of a page or a portion of an application, the scripts which exercise that URL are automatically disabled to prevent aberrant creation of errors and potentially triggering unnecessary maintenance corrective actions. Instead, the process of reconfiguring monitoring agents is performed, if necessary, and new transaction data is collected. Then, the analysis of the new transaction data is performed to yield new scripts which target the modified or updated URLs. These new scripts are then distributed accordingly (e.g. to relevant geographies), and enabled to resume testing as previously described (e.g. at times of greatest usage, or as background, or as out-of-phase). The schedules, locations and scripts that are automatically generated for playback are preferably automatic defaults, and preferably an administrator is allowed to customize those scripts to override any of the defaults. In some embodiments, the administrator is allowed to permanently override a default rule or parameter of a script. For embodiments which encode each assumption is a rule, as defined in any rule based system, then the administrator just need to replace the rule with one that matches their particular needs. Each rule then just acts as a template or default behavior that can be customized. Click-Path and Session Tracking Implementation Details In one available embodiment, the most frequent user click paths (sessions) are monitored and tracked using a unique tracking token such as a Session ID. This allows the invention to group sets of user requests into a common ordered list of requests that represent a single business transaction which is realized as a single robotic simulated transaction recording. For example, tracking and be performed using JSESSIONIDs in Websphere™, or by using the ARM Correlator defined in ITCAM for RTT. In an alternative embodiment, well-known “cookies” may be utilized to create a unique id that is persistent on the client's system, thereby allowing session and user tracking for the purpose of identifying collected transaction information. Other available techniques for session tracking may be employed in other embodiments of the invention. Packaging and Distribution Variations The automatically generated simulated transaction scripts may be created within each environment to be exercised, and alternatively may be transferred from one environment to another, with any appropriate adjustments as needed for the new target environment. This allows the development of a library or range of “out of the box” useable transaction scripts, which will then automatically be updated upon changes to the server or applications so that they evolve into customized transaction exercises for the targeted applications and servers as the applications and servers are updated. Alternative embodiments of the present invention include some or all of the foregoing logical processes and functions of the invention being provided by configuring software, deploying software, downloading software, distributing software, or remotely serving clients in an on demand environment. Software Deployment Embodiment. According to one embodiment of the invention, the methods and processes of the invention are distributed or deployed as a service by a service provider to a client's computing system(s). Turning to FIG. 3a, the deployment process begins (3000) by determining (3001) if there are any programs that will reside on a server or servers when the process software is executed. If this is the case, then the servers that will contain the executables are identified (309). The process software for the server or servers is transferred directly to the servers storage via FTP or some other protocol or by copying through the use of a shared files system (310). The process software is then installed on the servers (311). Next a determination is made on whether the process software is to be deployed by having users access the process software on a server or servers (3002). If the users are to access the process software on servers, then the server addresses that will store the process software are identified (3003). In step (3004) a determination is made whether the process software is to be developed by sending the process software to users via e-mail. The set of users where the process software will be deployed are identified together with the addresses of the user client computers (3005). The process software is sent via e-mail to each of the user's client computers. The users then receive the e-mail (305) and then detach the process software from the e-mail to a directory on their client computers (306). The user executes the program that installs the process software on his client computer (312) then exits the process (3008). A determination is made if a proxy server is to be built (300) to store the process software. A proxy server is a server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server. The two primary benefits of a proxy server are to improve performance and to filter requests. If a proxy server is required then the proxy server is installed (301). The process software is sent to the servers either via a protocol such as FTP or it is copied directly from the source files to the server files via file sharing (302). Another embodiment would be to send a transaction to the servers that contained the process software and have the server process the transaction, then receive and copy the process software to the server's file system. Once the process software is stored at the servers, the users via their client computers, then access the process software on the servers and copy to their client computers file systems (303). Another embodiment is to have the servers automatically copy the process software to each client and then run the installation program for the process software at each client computer. The user executes the program that installs the process software on his client computer (312) then exits the process (3008). Lastly, a determination is made on whether the process software will be sent directly to user directories on their client computers (3006). If so, the user directories are identified (3007). The process software is transferred directly to the user's client computer directory (307). This can be done in several ways such as, but not limited to, sharing of the file system directories and then copying from the sender's file system to the recipient user's file system or alternatively using a transfer protocol such as File Transfer Protocol (“FTP”). The users access the directories on their client file systems in preparation for installing the process software (308). The user executes the program that installs the process software on his client computer (312) then exits the process (3008). Software Integration Embodiment. According to another embodiment of the present invention, software embodying the methods and processes disclosed herein are integrated as a service by a service provider to other software applications, applets, or computing systems. Integration of the invention generally includes providing for the process software to coexist with applications, operating systems and network operating systems software and then installing the process software on the clients and servers in the environment where the process software will function. Generally speaking, the first task is to identify any software on the clients and servers including the network operating system where the process software will be deployed that are required by the process software or that work in conjunction with the process software. This includes the network operating system that is software that enhances a basic operating system by adding networking features. Next, the software applications and version numbers will be identified and compared to the list of software applications and version numbers that have been tested to work with the process software. Those software applications that are missing or that do not match the correct version will be upgraded with the correct version numbers. Program instructions that pass parameters from the process software to the software applications will be checked to ensure the parameter lists matches the parameter lists required by the process software. Conversely parameters passed by the software applications to the process software will be checked to ensure the parameters match the parameters required by the process software. The client and server operating systems including the network operating systems will be identified and compared to the list of operating systems, version numbers and network software that have been tested to work with the process software. Those operating systems, version numbers and network software that do not match the list of tested operating systems and version numbers will be upgraded on the clients and servers to the required level. After ensuring that the software, where the process software is to be deployed, is at the correct version level that has been tested to work with the process software, the integration is completed by installing the process software on the clients and servers. Turning to FIG. 3b, details of the integration process according to the invention are shown. Integrating begins (320) by determining if there are any process software programs that will execute on a server or servers (321). If this is not the case, then integration proceeds to (327). If this is the case, then the server addresses are identified (322). The servers are checked to see if they contain software that includes the operating system (“OS”), applications, and network operating systems (“NOS”), together with their version numbers, that have been tested with the process software (323). The servers are also checked to determine if there is any missing software that is required by the process software (323). A determination is made if the version numbers match the version numbers of OS, applications and NOS that have been tested with the process software (324). If all of the versions match, then processing continues (327). Otherwise, if one or more of the version numbers do not match, then the unmatched versions are updated on the server or servers with the correct versions (325). Additionally, if there is missing required software, then it is updated on the server or servers (325). The server integration is completed by installing the process software (326). Step (327) which follows either (321), (324), or (326) determines if there are any programs of the process software that will execute on the clients. If no process software programs execute on the clients, the integration proceeds to (330) and exits. If this is not the case, then the client addresses are identified (328). The clients are checked to see if they contain software that includes the operating system (“OS”), applications, and network operating systems (“NOS”), together with their version numbers, that have been tested with the process software (329). The clients are also checked to determine if there is any missing software that is required by the process software (329). A determination is made if the version numbers match the version numbers of OS, applications and NOS that have been tested with the process software 331. If all of the versions match and there is no missing required software, then the integration proceeds to (330) and exits. If one or more of the version numbers do not match, then the unmatched versions are updated on the clients with the correct versions (332). In addition, if there is missing required software then it is updated on the clients (332). The client integration is completed by installing the process software on the clients (333). The integration proceeds to (330) and exits. Application Programming Interface Embodiment. In another embodiment, the invention may be realized as a service or functionality available to other systems and devices via an Application Programming Interface (“API”). One such embodiment is to provide the service to a client system from a server system as a web service. On-Demand Computing Services Embodiment. According to another aspect of the present invention, the processes and methods disclosed herein are provided through an on demand computing architecture to render service to a client by a service provider. Turning to FIG. 3c, generally speaking, the process software embodying the methods disclosed herein is shared, simultaneously serving multiple customers in a flexible, automated fashion. It is standardized, requiring little customization and it is scaleable, providing capacity on demand in a pay-as-you-go model. The process software can be stored on a shared file system accessible from one or more servers. The process software is executed via transactions that contain data and server processing requests that use CPU units on the accessed server. CPU units are units of time such as minutes, seconds, hours on the central processor of the server. Additionally, the assessed server may make requests of other servers that require CPU units. CPU units are an example that represents but one measurement of use. Other measurements of use include but are not limited to network bandwidth, memory usage, storage usage, packet transfers, complete transactions, etc. When multiple customers use the same process software application, their transactions are differentiated by the parameters included in the transactions that identify the unique customer and the type of service for that customer. All of the CPU units and other measurements of use that are used for the services for each customer are recorded. When the number of transactions to any one server reaches a number that begins to effect the performance of that server, other servers are accessed to increase the capacity and to share the workload. Likewise, when other measurements of use such as network bandwidth, memory usage, storage usage, etc. approach a capacity so as to effect performance, additional network bandwidth, memory usage, storage etc. are added to share the workload. The measurements of use used for each service and customer are sent to a collecting server that sums the measurements of use for each customer for each service that was processed anywhere in the network of servers that provide the shared execution of the process software. The summed measurements of use units are periodically multiplied by unit costs and the resulting total process software application service costs are alternatively sent to the customer and or indicated on a web site accessed by the computer which then remits payment to the service provider. In another embodiment, the service provider requests payment directly from a customer account at a banking or financial institution. In another embodiment, if the service provider is also a customer of the customer that uses the process software application, the payment owed to the service provider is reconciled to the payment owed by the service provider to minimize the transfer of payments. FIG. 3c sets forth a detailed logical process which makes the present invention available to a client through an On-Demand process. A transaction is created that contains the unique customer identification, the requested service type and any service parameters that further specify the type of service (341). The transaction is then sent to the main server (342). In an On-Demand environment the main server can initially be the only server, then as capacity is consumed other servers are added to the On-Demand environment. The server central processing unit (“CPU”) capacities in the On-Demand environment are queried (343). The CPU requirement of the transaction is estimated, then the servers available CPU capacity in the On-Demand environment are compared to the transaction CPU requirement to see if there is sufficient CPU available capacity in any server to process the transaction (344). If there is not sufficient server CPU available capacity, then additional server CPU capacity is allocated to process the transaction (348). If there was already sufficient available CPU capacity, then the transaction is sent to a selected server (345). Before executing the transaction, a check is made of the remaining On-Demand environment to determine if the environment has sufficient available capacity for processing the transaction. This environment capacity consists of such things as, but not limited to, network bandwidth, processor memory, storage etc. (345). If there is not sufficient available capacity, then capacity will be added to the On-Demand environment (347). Next, the required software to process the transaction is accessed, loaded into memory, then the transaction is executed (349). The usage measurements are recorded (350). The usage measurements consists of the portions of those functions in the On-Demand environment that are used to process the transaction. The usage of such functions as, but not limited to, network bandwidth, processor memory, storage and CPU cycles are what is recorded. The usage measurements are summed, multiplied by unit costs and then recorded as a charge to the requesting customer (351). If the customer has requested that the On-Demand costs be posted to a web site (352), then they are posted (353). If the customer has requested that the On-Demand costs be sent via e-mail to a customer address (354), then they are sent (355). If the customer has requested that the On-Demand costs be paid directly from a customer account (356), then payment is received directly from the customer account (357). The last step is to exit the On-Demand process. Grid or Parallel Processing Embodiment. According to another embodiment of the present invention, multiple computers are used to simultaneously process individual audio tracks, individual audio snippets, or a combination of both, to yield output with less delay. Such a parallel computing approach may be realized using multiple discrete systems (e.g. a plurality of servers, clients, or both), or may be realized as an internal multiprocessing task (e.g. a single system with parallel processing capabilities). VPN Deployment Embodiment. According to another aspect of the present invention, the methods and processes described herein may be embodied in part or in entirety in software which can be deployed to third parties as part of a service, wherein a third party VPN service is offered as a secure deployment vehicle or wherein a VPN is build on-demand as required for a specific deployment. A virtual private network (“VPN”) is any combination of technologies that can be used to secure a connection through an otherwise unsecured or untrusted network. VPNs improve security and reduce operational costs. The VPN makes use of a public network, usually the Internet, to connect remote sites or users together. Instead of using a dedicated, real-world connection such as leased line, the VPN uses “virtual” connections routed through the Internet from the company's private network to the remote site or employee. Access to the software via a VPN can be provided as a service by specifically constructing the VPN for purposes of delivery or execution of the process software (i.e. the software resides elsewhere) wherein the lifetime of the VPN is limited to a given period of time or a given number of deployments based on an amount paid. The process software may be deployed, accessed and executed through either a remote-access or a site-to-site VPN. When using the remote-access VPNs the process software is deployed, accessed and executed via the secure, encrypted connections between a company's private network and remote users through a third-party service provider. The enterprise service provider (“ESP”) sets a network access server (“NAS”) and provides the remote users with desktop client software for their computers. The telecommuters can then dial a toll-free number to attach directly via a cable or DSL modem to reach the NAS and use their VPN client software to access the corporate network and to access, download and execute the process software. When using the site-to-site VPN, the process software is deployed, accessed and executed through the use of dedicated equipment and large-scale encryption that are used to connect a company's multiple fixed sites over a public network such as the Internet. The process software is transported over the VPN via tunneling which is the process of placing an entire packet within another packet and sending it over the network. The protocol of the outer packet is understood by the network and both points, called tunnel interfaces, where the packet enters and exits the network. Turning to FIG. 3d, VPN deployment process starts (360) by determining if a VPN for remote access is required (361). If it is not required, then proceed to (362). If it is required, then determine if the remote access VPN exits (364). If a VPN does exist, then the VPN deployment process proceeds (365) to identify a third party provider that will provide the secure, encrypted connections between the company's private network and the company's remote users (376). The company's remote users are identified (377). The third party provider then sets up a network access server (“NAS”) (378) that allows the remote users to dial a toll free number or attach directly via a broadband modem to access, download and install the desktop client software for the remote-access VPN (379). After the remote access VPN has been built or if it has been previously installed, the remote users can access the process software by dialing into the NAS or attaching directly via a cable or DSL modem into the NAS (365). This allows entry into the corporate network where the process software is accessed (366). The process software is transported to the remote user's desktop over the network via tunneling. That is the process software is divided into packets and each packet including the data and protocol is placed within another packet (367). When the process software arrives at the remote user's desktop, it is removed from the packets, reconstituted and then is executed on the remote users desktop (368). A determination is made to see if a VPN for site to site access is required (362). If it is not required, then proceed to exit the process (363). Otherwise, determine if the site to site VPN exists (369). If it does exist, then proceed to (372). Otherwise, install the dedicated equipment required to establish a site to site VPN (370). Then, build the large scale encryption into the VPN (371). After the site to site VPN has been built or if it had been previously established, the users access the process software via the VPN (372). The process software is transported to the site users over the network via tunneling. That is the process software is divided into packets and each packet including the data and protocol is placed within another packet (374). When the process software arrives at the remote user's desktop, it is removed from the packets, reconstituted and is executed on the site users desktop (375). Proceed to exit the process (363). While certain examples and details of a preferred embodiment have been disclosed, it will be recognized by those skilled in the art that variations in implementation such as use of different programming methodologies, computing platforms, and processing technologies, may be adopted without departing from the spirit and scope of the present invention. Therefore, the scope of the invention should be determined by the following claims.
	summary
041994027	description	DETAILED DESCRIPTION With more particular reference to the drawings there is shown generally at 1 a portion of a closed loop accelerator, the entirety of which has an interior chamber 2 in the form of an annulus having alternating maximum and minimum cross-sections. The accelerator wall 4 comprises a 1 cm. to 0.5 cm. thickness of any suitable high temperature resistant stainless steel. As shown in FIG. 2 the wall 4, referred to as the primary wall or the vacuum wall, is concentrically surrounded by shielding 6, known also as the blanket. SHIELDING The shielding comprises a combination of concentric layers selected by taking into account several factors. A first layer for vacuum wall cooling comprises a 9 cm. thick liquid layer 8 of LiF or KF or a suitable mixture of both. This layer is contained within an annulus having inner and outer walls 10 of Niobium (Nb), which are 0.5 cm. in thickness. The next layer 12 comprises a 20 cm. thick layer of 96% Li, 2% BeF.sub.2, known as the inner moderator and breeder. The next layer 14 comprises 7 cm. thick graphite and known as the outer moderator. The next layer 16 is a 3 cm. thick solid layer of 98% Li and 2% Nb which absorb thermally active neutrons. These layers described thus far comprise a primary attenuator or blanket portion of the shielding. Additional layers comprise, a 15 cm. thick layer 18 of lead serving as a gamma ray absorber and a 25 cm. thick layer 20 of insulation preferably in a vacuum chamber with walls 22 of any suitable thickness. These additional layers comprise the radiation shield portion of the shielding 6. Operation of the shielding is as follows. Neutrons in the accelerator tend to escape through the wall 4. The layer 8 provides initial cooling for the wall 4. The inner moderator and breeder layer 12 absorbs some of the neutrons, which are high in kinetic energy, to produce or breed tritium through reaction of the neutrons with liquid Li. Hence the kinetic energies of the absorbed neutrons are absorbed or moderated. The tritium produced will pass characteristically through the Nb tubing which comprises the containing wall for the layer 8 and can be extracted by any conventional extractor method from the liquid layer 8. The graphite layer 14 thoroughly absorbs or moderates the kinetic energy of the neutrons passing through the layer 12. Thus when the neutrons escape to or reach the layer 16 they contain solely thermal energy which can be extracted. The additional layers 18, 20 and 22 minimize the heat escape generated by the escaping neutrons. The lead absorbs gamma radiation escaping from the primary attenuator. Also shown is a power extractor shown generally at 26 comprising stainless steel inlet tube 28 and outlet tube 30 through which the liquid coolant 8 is circulated. Also the tubes 28 and 30 are passed through the primary loop 32 of a heat exchanger shown generally at 34. A suitable liquid such as water or liquid KF or LiF is circulated in the secondary looped tube 36 of the heat exchanger 34. Heat is drawn off in the form of a power turbine shown schematically at 38. As shown in FIGS. 1 and 2 the shielding 6 is surrounded by conventional Nb type magnetic coil windings 24 which generate force lines along the accelerator annular axis propelling charged ions and electrons around the chamber of the accelerator from left to right in FIG. 1. These windings comprise the primary coil of the accelerator. At each maximum cross-section ions are created and are circulated within the accelerator chamber. A magnetic field created in the conventional manner by the coils 24 so constructed and arranged, prevent the ions being propelled from left to right around the accelerator chamber from hitting the wall 4. The ions are preferably duterium and tritium. Hereafter the use of duterium and tritium only will be discussed. ELECTRON EXTRACTOR Within each maximum cross-section 40 of the accelerator is located an electron extractor 42 fabricated from an open mesh stainless steel grid in the form of a relatively short section of a curved paraboloid open at its ends 44. The electron extractor may be supported by insulation shown schematically at 46 from the wall 4. LASER A laser 48, or any suitable number thereof, is mounted in any suitable mechanical fashion externally of the shielding 6. If required, any projection system for the laser is schematically represented by a mirror 50 also mounted outside the shielding 6. A stainless steel tube 52 through the shielding 6 is sealably surrounded by the shielding 6. A high temperature glass window 54 covers a small opening in the accelerator wall 4. The laser beam is projected by the mirror 50 and additional mirror 56, if required, and focused by a lens 58 in the tube 52 to project through the lens and to an opening 60 in the electron extractor 42. The laser is advantageously a Neodyminium-glass laser having a wave length of 1.06.mu.. The peak power output is advantageously of between one and 10 kilo joules with a maximum pulse width of 10.sup.-9 seconds maximum. The laser beam is focused to impinge a maximum cross-sectional area of about 25.times.10.sup.-4 cm.sup.2 on the surface of a Duterium-Tritium pellet at 61. Each pellet is injected through a stainless steel tube 62 sealably encircled by the shielding 6. A flexible stainless steel nozzle or tube 64 may be removed after completing insertion of the pellet or pellets as desired. The laser beam impinges the pellet or pellets and produces electrons, duterium ions and tritium ions. The laser energy also gives initial kinetic energy to the ions propelling them toward a relative minimum cross-section or node 66 of the accelerator where fusion is to take place. Also the laser energy imparts initial high temperature to the ions prior to their reaching the critical temperature for fusion to take place. The electron extractor is charged so as to attract the electrons produced by the laser, removing the electrons from the ions propelled toward the node 66. A cathode grid 68 (a virtual cathode) located at the exit opening 44 of the electron extractor, and supported by insulation 69 against the wall 4, also pulls the ions toward the node 66. The accelerator windings 24 also propel the ions toward the node 66. Ions will cycle around the accelerator and will enter the open end 44, the entrance end, of the electron extractor, and will exit through the exit opening 44. The virtual cathode at the exit opening 44 passes positive ions therethrough toward the node 66. The electrons, if any are present, are drawn off by the extractor which is kept at positive potential with respect to the virtual cathode. TUBE DD To generate an electron cloud, as shown in FIGS. 3 and 4, a tube DD in the form of an annulus is located at the center of the node 66. The tube is made of stainless steel and is attached to and contacts the inner periphery of the wall 4. The inner surface of the tube is coated with a layer of insulation 70. An annulus of stainless steel forms a cathode 72 and is supported inside the tube DD by the insulation 70. A mesh grid in the form of an annulus forms an electrically biasing grid 74. The grid is supported by strips of insulation 76 from the cathode. A mesh anode 78 in the form of an annulus is supported inside the grid 74 by insulation strips 80. As shown the components described are provided with a continuous opening around the circumference facing the common center of curvature of the concentric annuli. The opening is covered by a grid 82 supported entirely by the insulation 70. As shown schematically the cathode 72 and anode 78 are connected electrically to a power supply providing the requisite polarity voltages. A modulation and bias voltage source is shown connected to the grid 74. The inside of the cathode is coated with a photoelectric material such as germanium or aluminum which will emit copious quantities of electrons in response to ultraviolet radiation which is spontaneously present in the node 66 in response to positive ions entering the tube DD. COILS M.sub.1 AND M.sub.2 Outside the shielding 6, as shown in FIG. 4, are located coils M.sub.1 and M.sub.2. For clarity the coils are shown separated on either side of the node 66. However, it is understood that the coils M.sub.1 and M.sub.2 both are distributed along the length of the accelerator wall so they surround the accelerator in the vicinity of the node 66, encircling the tube DD. The coils are magnetic superconducting coils of Nb.sub.3 Sn producing a magnetic field. Rods 82 running lengthwise of the accelerator are located outside the shielding 6 and are within the coils M.sub.1 and M.sub.2, as shown. Only a few rods are shown, whereas there are many, all around the node and encircling the accelerator. The rods are superconductive Nb.sub.3 Sn and create magnetic fields to compress the ions to a minimum B, as will be explained. As shown in FIGS. 1, 3 and 4, an electron injector 84, located within a stainless steel tube 86, which is joined to the wall 4 at a 45 degree angle, communicates with the interior of the accelerator in order to inject electrons to the center of the DD tube. Any desired number of tubes 86 and corresponding injectors 84 may be provided. An ion injector 88 is located in a stainless steel tube 90 which extends through the wall 4 and the stainless steel wall of tube DD, as shown in FIGS. 1 and 3. The tube 90 is attached to the tube DD and communicates with the interior of the tube through a hole in the insulation 70 and the cathode 72. A grid 92 supported totally by the insulation 70 can be charged at an appropriate time to prevent escape of electrons or ions from the tube DD. OPERATION OF TUBE DD When ions are propelled from left to right in FIG. 1, the coils M.sub.1 and M.sub.2 are turned on and their magnetic fields trap the ions C longitudinally within the accelerator at the node 66 and compress them to form the minimum radial configuration within the center of the tube so that the ions do not touch the DD tube and thereby tend to escape from the magnetic well or trap created by the coils M.sub.1 and M.sub.2. The rods 82 are turned on to compress even further the radial configuration to the minimum B configuration (mathematical model) at C.sub.7, thereby making the magnetic well deeper. The electron injector 84 injects electrons into the deep magnetic well or trap neutralizing the space charge of the ions thereby preventing their escape from the well or trap. Ultraviolet radiation will be present as is well known by quantum mechanics principles and will cause electrons in copious quantities to be emitted from the electroluminescent cathode 72. The grid 74, at positive potential with respect to the cathode and negative with respect to the anode 78, accelerates the emitted electrons toward the center of the toroidal tube DD to form a toroidal electron cloud 94. The cloud is maintained because the copious quantities of emitted electrons will continuously accelerate toward and then past the anode, neutralizing the space charge of the anode and thereby eliminating the anode attraction for the electrons in the cloud. Further, the grid will form its own image smaller than and concentrically within the anode further keeping the electrons in the cloud. The presence of the dense electron cloud, continuously regenerated with emitted electrons, causes the ions in the plasma to make trips or excursions at right angles to the axis of the accelerator back and forth, first toward the electron cloud reducing the ion density in the well, and then back toward the well to re-establish the correct ion density for a neutral space charge of the plasma. The confinement time of the ions has been increased because of this arrangement such that fusion occurs. Heretofore the ion-ion collisions within a "magnetic bottle" has caused the ions to escape before fusion was produced. Here, the product of the increased confinement time and the ion density is sufficient to satisfy the Lawson criteria (mathematical model) for fusion to occur. The ion injector is not necessarily utilized for the above to occur. However, ions are injected to cause electron emission if the ion density and the consequent ultraviolet radiation thereof is desired to be increased or adjusted. The ions injected directly into the tube DD through the tube 90 will speed toward the anode, pulling emitted electrons and accelerating them past the anode toward the center of the tube DD to form the electron cloud. The electrons will accelerate past the ions also according to quantum mechanics principles to form the cloud. The ions will tend to form a shell around the electron cloud. However, the electron to ion ratio yet increases as the distance toward the center or focus of the DD tube, thereby at the center the electron density is greatest, resulting in the desired cloud. Subsequent to fusion, the heat produced is extracted by the power extractor 34, pumping the cooling fluid 8 which has absorbed the heat transferred through the wall 4 in the vicinity of the node 66. The magnetic well is released by shutting off the coils M.sub.1 and M.sub.2 and the rods 82, allowing the particles, i.e., waste products of fusion, electrons and ions to escape from left to right in FIG. 1 from the node 66. The ions speed away and pass through magnetohydrodynamic coils, illustrated schematically at 96 in FIG. 4. The waste products of fusion are extracted by a pump having an inlet shown at 98 in FIG. 7. The waste products are in vapor form and, being heavy particles will fall out of the escaping stream of particles toward an enlarged annular portion 99 integral with and projecting outwardly of the wall 4, allowing their removal by the pump. The portion 99 is also out of the longitudinal portion of the accelerator after coils M.sub.2. An extractor field coil 101 encircles the escaping ion stream causing eddy current flow 103 of magnetic field. The waste products, in vapor form, are disturbed by the flow 103, striking collector plates 105, supported by insulation 107, where they are drawn off by the pump. The pump is a vacuum pump of the type known as, Diversey, Mag-ion, Model MI-900, manufactured by the VEECO Instruments Inc., Plainview, N.Y. The pump is guaranteed operative to 10.sup.-12 torr. But by heating the ions before being trapped in the magnetic mirror, outgassing at elevated temperature will approach 10.sup.-13 torr at a pump speed of 100 liters per second. Other tubes, one shown at 109, can be strategically placed for additional pumps to outgas the accelerator. Upon leaving the node and passing through extractor 98 the ion stream passes through an electron extractor 111, in the shape of a paraboloid with open ends, supported on the wall 4 by insulation 114, and similar to the extractor 42, is appropriately charged to remove electrons from the ion stream. The ions then pass through the coils 96. The magnetic field strength of the coils depends upon particle density. For: N.perspectiveto.10.sup.14 to 10.sup.15 cm.sup.-3 ; .beta..perspectiveto.10 K Gauss. For: N.perspectiveto.10.sup.-19 cm.sup.-3 ; .beta. will be over a Mega Gauss. A virtual cathode 115, supported by insulation 117 operates like cathode 68 to propel ions toward the next node of the accelerator. ELECTRON INJECTOR The details of the electron injector 84 are shown schematically in FIG. 5. The injector 84 includes a heater coil 100 with its electrical leads 102. The coil 100 is encircled by a cathode 104, in turn encircled by a grid 106. Electrical leads 108 for the cathode and 110 for the grid are shown for connection to suitable bias voltages. Emitter material shown at 111 emits electrons when heated which electrons are focused in a stream 112 through an opening 114 in a first anode 114 provided with electrical leads 116. Any well known electron lens system, shown schematically at 118 is used to form a convergeant beam of electrons emerging from the limiting aperture 120 formed at the opening of a second anode 122, having electrical leads 124. In accordance with accepted knowledge, the diameters of the encircling anodes 114 and 122 influence the focal length of the lens 118. Most important is the ratio of voltages impressed upon the anodes in order to obtain a desired convergence of the electron beam emitted from the limiting aperture. Also required is the potential difference between the second anode 122 and the cathode to be greater than that between the first anode 114 and the cathode. The electron beam is inside and directed along the tube 62 for electrons to be injected into the tube DD. ION INJECTOR The ion injector 88 is shown in FIG. 6 as having an envelope 126 having an inlet 128 for the introduction of any suitable gaseous source of ions. A gas outlet is shown at 130. Internally of the envelope there is illustrated schematically an anode 132, a grid 134 and a cathode 136. A D.C. source 138 biases the anode positive with respect to the grid 134. An R.F. supply 140 is connected directly to the grid 74 of the tube DD, through a capacitor 142 to the cathode 136, and through a resistor 144 to the grid 134. The envelope 126 also includes the tube 90 connected directly to the tube DD. The positive side of a power supply is connected to the anode 78 of the tube DD and to the junction of the grid 134 and the source 138. The power supply negative side is connected to the cathode 72. Another RF supply is connected between the cathode 72 and the anode of the tube DD as shown. The aperture of the outlet 90 comprises any well known ion optical system which collimates and directs the ion stream through the open mesh anode 132. The envelope 126 and the accelerator may have the same vacuum pressure since they open into each other. Controlled quantities of Duterium-Tritium gas are introduced in the inlet 128. Residual gas is exhausted via the outlet 130. Space charge between the anode, grid and cathode produce the ions which are directed into tube DD. A schematic section of a relative minimum section 66 is known as a magnetic mirror system. The plasma stream is shown at C. E.sub.B is the magnetic lines of force of the accelerator. E.sub.R represents electric induced vectors of force perpendicular to E.sub.B. The coil current is shown in circular path about annular M.sub.1 and M.sub.2. A hollow circular, looped tube DD is located about the focal plane center AA of the minimum section 2. An electron cloud is generated by conventional techniques within the tube DD. This gives the radial vector E.sub.R due to the electron cloud generation perpendicular to the E.sub.B. Ions are heated initially to about 10.sup.8 .degree. K. before being tapped in the magnetic mirror system. And as they are accelerated or brought to the focal plane the electrons are injected at 66 so as to create a plasma and the magnetic field B is switched on or pulsed in the form of a minimum B magnetic mirror configuration to trap the ions in the form of a plasma. Various conventional methods of trapping can be used, taking into account the injection angle of the ion stream to make the loss cone of the ion mass as small as possible. Also the electron cloud is generated in the tube DD and this creates a radial vector E.sub.R acting at C which is at right angles to E.sub.B. This causes rotation of the plasma at C, and due to the electrons and ions "trips" through C, the rotational energy is also transferred into thermal energy which helps in heating the plasma. Heating the plasma also occurs by magnetic compression by E.sub.B. The presence of E.sub.R also serves to increase the kinetic energy of the particles at right angles to B; this reduces considerably the escape of plasma through the mirror ends M.sub.1 and M.sub.2 resulting in longer confinement time for the plasma. An electrical discharge through tube DD is created to increase the particle density at C to satisfy the Lawson criterion. MODIFIED MIRROR SYSTEM As pointed out before, the tube "DD" holds the electron cloud so that the oscillations of charged particles at right angles to the magnetic field takes place and this contributes a higher velocity to the particles perpendicular to the lines of force, thereby trapping the particles more in the magnetic well. In order to create a higher density of particles at the focal plane, the space charge of the accelerated ions have to be slightly neutralized by injecting electrons even before they come to the focal plane and then completely neutralizing it when they reach the focal plane, thereby creating the required plasma. Further increase in the density of particles at the focal plane can be achieved by injecting neutral particles by the ion injector at the focal plane at right angles to the magnetic field lines. These neutral particles will be ionized by the plasma already entrapped inside the magnetic well and also by oscillating discharge through the tube "DD" at right angles to the magnetic field lines. Tube "DD" thus performs two functions, e.g., 1. It acts as a trap for the plasma as explained above and PA1 2. It acts as an ionizer for the neutrals which are injected to increase the density of particles at the focal plane. PA1 For: n.perspectiveto.10.sup.14 to 10.sup.15 cm.sup.-3 PA1 For: n.perspectiveto.10.sup.19 cm.sup.-3 PA1 e=electronic charge PA1 K=Boltzman's constant PA1 T=plasma temperature PA1 (a) very deep magnetic well PA1 (b) short lines of force PA1 (c) high .beta. (15%) PA1 (a) differential drift of ions and electrons and PA1 (b) microinstabilities PA1 I.sub.e =measured electron current PA1 n.sub.i =ion mass PA1 m.sub.e =electron mass PA1 e=electronic charge PA1 E.sub.o =dielectric constant PA1 a.sub.o =diameter of the ion beam at the minimum cross-section PA1 a=diameter of the ion beam at any point PA1 p.sub.o =space charge density at the minimum cross-section PA1 E.sub.o =dielectric constant PA1 m=mass of the ion PA1 e=electronic charge PA1 v=velocity of the ion= PA1 L=1 at Z=0 and L'=0=dL/dZ PA1 e=electronic charge. PA1 K=Boltzman's constant PA1 T=plasma temperature PA1 (a) very deep magnetic well PA1 (b) short lines of force PA1 (c) high .beta. (>15%) PA1 (a) differtial drift of ions and electrons and PA1 (b) microinstabilities. PA1 V=running voltage PA1 r.sub.c2 =radius of the electron cloud ##EQU7## N.sub.i and N.sub.e are the number of ion and electron trips respectively. I.sub.i =measured ion current PA1 I.sub.e =measured electron current PA1 n.sub.i =ion mass PA1 m.sub.e =electron mass PA1 e=electronic charge PA1 E.sub.o =dielectric constant The required fusion temperature at the focal plane is generated by adiabatic magnetic compression, or other suitable conventional techniques, e.g., laser beam, etc. As the magnetic well trap is released, the positive particles flow through the tube toward the maximum cross-section of the tube where a negative grid has been placed to create a virtual cathode. As soon as the positive particles arrive at the virtual cathode, the acceleration device for the ions is switched on so as to bring them back at the focal plane at the minimum cross-section. During the passage of positive particles from the focal plane to the maximum cross-section a diverter is used which filters off all the impurities and and other by-products of fusion, leaving only duterium and tritium ions. The process is thus repeated again and again. When the depletion of the duterium and tritium ions becomes considerable, as shown by a measuring device at the maximum cross-section of the tube, fresh ions are introduced at the maximum cross-section to make up for the depletion. During the passage of particles from the focal plane to the maximum cross-section of the tube, the electrons are also extracted off from the stream of positive particles; thus the flow of positive particles alone can also be utilized in the direct generation of electrical power. The sequence of operations between the focal plane at the minimum cross-section and the maximum cross-section of the tube can be repeated all along the total path of the tube as designed. The field inside the plasma is not always zero and the ratio of ".beta." of the plasma pressure to the magnetic pressure is important in confinement studies; it is of great importance that in a practical reactor the ".beta." should be high--(15% or so). .beta. is dependent upon particle density. B.perspectiveto.10 KGauss PA2 B.gtoreq.Mega gauss The first loss process is that due to diffusion "D" across the lines of force where "D.perp.".about.nTe.sup.-1/2 B.sub..perspectiveto..sup.-2 10.sup.-1 cm.sup.2 /sec. where n=particle density T.sub.e =electron temperature and B=magnetic field. Unfortunately, anamolous diffusion which is often called Bohm diffusion is observed (D.sub.B), where D.sub.B .about.1/16 KT/eB where This is actually due to low frequency electric field fluctuations in the plasma arising from what are called microinstabilities and are particularly based on drift waves. D.sub.B .perspectiveto.10.sup.5 cm/sec. and is too high. It is therefore important to keep the microinstabilities ver low, so that acutal diffusion rate to that given by D.sub.B is less than 1/100. The differential drift of the ions and electrons give rise to gross instabilities, which in turn give rise to large scale motions of the plasma across the lines of force. Also, excursion of particles larger than the Larmor radius enhance collisional diffusion across the magnetic lines of force. All the above instabilities are reduced considerably by introducing the magnetic well geometry with the modifications as indicated, wherey achieving the following: In the mirror system the confinement depends on the conservation of magnetic moment of the gyrating particles. As this is destroyed by collisions, the confinement time is limited to about the ion-ion collision time. The trips of electrons and ions across the electron cloud and through the center of the magnetic well, actually make the well very deep and prevent the The differential equation for the ion and electron trips through the center of the magnetic well can be written as this: ##EQU1## where .phi.=V/V.sub.C.sbsb.1 .nu.=Log.sub.e rc2/r PA0 V.sub.C.sbsb.1 =sometimes voltage due to escess positive ions at the center of the well and other times due to excess of electrons at the center of the well. PA0 v=running voltage PA0 r=running radius PA0 r.sub.c2 =radius of the electron cloud ##EQU2## N.sub.i and N.sub.e are the number of ion and electron tips respectively. I.sub.i =measured ion current PA0 P.sub.n =10.sup.14 -10.sup.15 cm.sup.-3 PA0 T.sub.i .perspectiveto.T.sub.e .perspectiveto.10 Kev PA0 where T.sub.e =electron temperature PA0 C.sub.t .perspectiveto.1 sec. PA0 N.sub.P =nuclear power output PA0 .perspectiveto.5-500 W/cc PA0 P.sub.n .perspectiveto.10.sup.14 cm.sup.-3 PA0 T.sub.i .perspectiveto.100 Kev PA0 C.sub.t .perspectiveto.1 sec. PA0 N.sub.p .perspectiveto.100 W/cc PA0 Here minimum scattering is required. PA0 P.sub.n .perspectiveto.10.sup.16 to 10.sup.20 cm.sup.-3 PA0 T.sub.i .perspectiveto.T.sub.e .perspectiveto.10 KEV PA0 C.sub.t .perspectiveto.10.sup.-6 .about.10.sup.-1 sec PA0 N.sub.p .perspectiveto.1 MW/cc The actual size of the magnetic well can be scaled up or down depending upon the particle density, gyrating radii of the particles around the magnetic field lines and the strength of the magnetic field used. All the magnetic wells are located at the minimum cross-sections of the device, as indicated in the drawings. At the nodes 66 the heat from fusion can be extracted by a conventional extractor 34 for electrical power production by conventional techniques. It is noted that the entire outer periphery of the accelerator 1 is covered with the shielding 6 which traps neutrons, electromagnetic radiation and other particles using their energy for supplementing the energy extracted by the extractor 34. At the exit of each node the positive particles diverge and become less dense and some kinetic enery is lost. All electrons are extracted by the electron extractor; and all fusion by-products and impurities are extracted by the diverter or extractor leaving only duterium and tritium positive ions for recirculation in the accelerator. The positive ions are then drawn away toward the virtual cathode as described. The particle density of the ions is measured and any deficit is resolved by injecting added ions by the injectors at 64. The kinetic energy lost by the ions by their passing through a magnetic field indicated schematically at 96 is extracted creating direct current production by magnetohydrodynamic techniques or other conventional techniques. The following equations hold true for the present invention. ION PATH The accerator has been so designed as to contain the envelope of the ion beam which can be mathematically expressed in the form of an integral equation at any point "Z" as follows: ##EQU3## S=(E.sub.o M.sub.o.sup.2 /ep.sub.o) L=a/a.sub.o Thus the maximum and minimum in the path of the ions can be determined using the above equation, of course, the ion desnity will be minimum at maximum cross-section and maximum at minimum cross-section as shown in the diagram. RELEASE OF FUSION ENERGY A. D+T.fwdarw..sup.4 He+n+17.6 Mev Where n=neutrons, D=Duterium, T=Tritium and .sup.4 He=helium. Here "n" is used to supplement the tritium breeding reaction as EQU n+.sup.6 Li.fwdarw.T+.sup.4 He=4.8 Mev where L.sub.i =Lithium ##EQU4## This is supplemented by reactions between .sup.3 He, T and D and energy yielding neutron capture reactions. Reaction (A) has the largest cross-section and provides easy confinement. CONDITIONS (1) The energy of the colliding nuclei must exceed about 5 Kev thus ion temperature T.sub.i .perspectiveto.10 Kev. (2) Nuclei must be confined at these energies for a time "C.sub.t " such that nuclear energy released exceeds the energy used in heating the ions. Hence the condition necessary is written as: EQU p.sub.n C.sub.t .gtorsim.10.sup.14 C.sub.m -.sup.3 S.sub.ec (Lawson criterion) where p.sub.n =number of nuclei per cubic centimeter (3) As the ratio of the scattering cross-section to the fusion cross-section varies more steeply than 1/T.sub.i 2, higher the T.sub.i better the fusion cross-section probability. Thus at lower T.sub.i nuclear velocities must be largely randomized (as it happens at the minimum cross-sections of the ion envelope) in order to satisfy the Lawson Criterion. Less randomized velocity spectrum is permitted at temperatures as high as 1 Mev due to large reduction in scattering cross-section. Taking into account the above three conditions, we can formulate nuclear power output as: (a) (b) (c) This is easily achieved in our focusing device at the minimum cross-section of the ion envelope. Here pressure becomes very high and already at P.sub.n =10.sup.19 cm.sup.-3 magnetic fields exceeding 10.sup.6 gauss will be required. Since in our system ions keep on circulating lower "P.sub.n " can be used as power can be extracted at each minimum cross-section and direct electric current can be extracted during the passge of the ions from one minimum cross-section to the next maximum cross-section. The ion envelope can be designed in such a way that only the initial ions like D+D or D+T are made to circulate through the system again and again till the ion density is depleted below the Lawson Criterion. At this point, a fresh input of ions can be injected into the system at maximum cross-section. At the minimum cross-section the by-products of fusion are filtered out by diverters. At each minimum cross-section, the positive ion space charge is neutralized by injecting a circulatory electron current so as to create the plasma which is then compressed by the magnetic field to create fusion; magnetic field is operated in such a way that the Lawson Criterion as regards ion density and containment time is fulfilled. Magnetic field is released and the ions pass on to the next minimum cross-section. It is to be pointed out that ions could be initially heated to about 10.degree. K. by circulating them through the accelerator before being trapped in the magnetic well. As they are brought to a focal plane at the minimum cross-section, they are neutralized, some of the neutralized atoms are left in highly excited atomic states and as these atoms enter the magnetic well they become easily reionized and trapped. More neutral atoms can be introduced in the magnetic well at right angles to the magnetic field lines by means of an injector as shown in the diagram so as to satisfy Lawson's Criterion. These neutrals can be ionized by using the tube "DD" as an ionizer as shown in the diagram and thereby can be easily trapped in the magnetic or potential well. In the potential well, the plasma is compensated with approximately N.sub.i .perspectiveto.N.sub.e where N.sub.i and N.sub.e are ion and electron densities respectively, but only for a short time due to the fact that the ions have already been brought to a dense focus by this device instead of bringing a dispersed plasma to a high density as is usually done with the consequent loss of energy as Bremsstrahlung. The magnetic well system is modified in such a way that the plasma finds itself in a true potential well with the field strength increasing outwards and thus the leakage is eliminated and the confinement time is larger than the ion-ion collision time. Once the confinement time is over, the tap is released by collapse of the potential and the ions are cooled through the cooling system. In the process of cooling the ions are attracted to the virtual cathode by a voltage generated at the grid at the maximum cross-section of the accelerator device which is turned on and the process is repeated. The collisions between the hot ions of the plasma and the residual atoms of cold background result in the sbustitution of a cold ion for a very hot ion and in the place of the hot ion a very fast neutral ion is produced which escapes from the magnetic well, whereas the cold ion moves slowly and is readily deflected and scattered through the mirrors and lost. In this device the ion density has been considerably increased in the focal plane at minimum cross-section, thus the confinement time can be correspondingly reduced, thereby minimizing the charge exchange phenomena. To minimize further the charge exchange phenomena, the background atoms and impurities can be further reduced by working at a pressure below 10.sup.-12 torr. The various conventional methods of trapping can be used taking into account the injection angle of the ions so as to make the loss cone for the ions as small as possible. Also, an electron cloud is generated in the hollow tube "DD" as shown in the figures; this creates a radial electric victor "E.sub.r " acting at "C", which is at right angles to E.sub.B. This rotates the plasma at "C" and due to the electron and ion trips through "C", the rotational energy is also transferred into the thermal energy, thereby helping in the heating of the plasma, which is also heated by the magnetic compression of the plasma. The action of "E.sub.r " is also to increase the kinetic energy of the particles at right angles to E.sub.B --this reduces considerably the escape of the plasma through the mirror ends. This results in better confinement time for the plasma, i.e., larger than the ion-ion collision time. PLASMA STABILITY INSIDE THE MAGNETIC WELL The field inside the plasma is not always zero and the ratio ".beta." of the plasma pressure to the magnetic pressure is important in confinement studies; it is of great importance that in a practical reactor the ".beta." should be high--(15% or so). The first loss process is that due to diffusion "D.perp." across the lines of force where "D.perp.".about.nT.sub.e.sup.-1/2 B.sup.-2 .perspectiveto.10.sup.-1 cm.sup.2 /sec. where n=particle density T.sub.e =electron temperature and B=magnetic field. Unfortunately, anamolous diffusion which is often called Bohm diffusion is observed (D.sub.B), where D.sub.B .about.1/16 KT/eB where This is actually due to low frequency electric field fluctuations in the plasma arising from what are called microinstabilities and are particularly based on drift waves. D.sub.B .perspectiveto.10.sup.5 cm/sec. and is too high. It is therefore important to keep the microinstabilities very low, so that actual diffusion rate to that given by D.sub.B is less than 1/100. The differential drift of the ions and electrons give rise to gross instabilities, which in turn give rise to large scale motions of the plasma across the lines of force. Also, excursion of particles larger than the Larmor radius enhance collisional diffusion across the magnetic lines of force. All the above instabilities are reduced considerably by introducing the magnetic well geometry with the modifications as indicated, whereby achieving the following: In the mirror system the confinement depends on the conservation of magnetic moment of the gyrating particles, as this is destroyed by collisions, the confinement time is limited to about the ion-ion collision time, but in our modified mirror system the confinement time is larger than the ion-ion collision time due to the ion and electron oscillations across the field lines as a result of the victor "E.sub.r ". The trips of electrons and ions across the electron cloud and through the center of the magnetic well, actually make the well very deep and prevent the The differential equation for the ion and electron trips through the center of the magnetic well can be written as: ##EQU5## where ##EQU6## V.sub.C.sbsb.1 =sometimes voltage due to excess positive ions at the center of the well and other times due to excess of electrons at the center of the well. The actual size of the magnetic well can be scaled up or down depending upon the particle density, gyrating radii of the particles around the magnetic field lines and the strength of the magnetic field used. All the magnetic wells are located at the minimum cross-sections of the device, as indicated in FIG. 1. Although preferred embodiments of the process have been described and schematically illustrated, modifications and other embodiments which would be obvious to one having ordinary skill in the art are intended to be covered by the scope and spirit of the following claims.
	abstract	A patterning device holding apparatus includes a support platform unit with a plurality of first positioning projections and a gripper unit. The gripper unit includes a head portion and a plurality of second positioning projections disposed on the head portion, and a rolling member set at a base portion. The grapping and releasing of the patterning device is achieved by the rotation of the gripper unit about a pivot substantially parallel with the center axis of the rolling member. The first and second positioning projections corporately abut against the edges of a patterning device to fix the patterning device in place.
055352537	description	DESCRIPTION OF PREFERRED EMBODIMENTS Since the arrangement of nuclear installations and in particular of their ventilation and/or cooling circuit are well known in the state of the art, a description will be given below only of those points directly or indirectly relating to the invention. For the rest, the person skilled in the art of the technical sector in question will draw on the currently available conventional solutions when tackling the particular problems with which he is confronted. The same reference number will always be used below to identify a similar element, whatever the embodiment or its variant. For clarity of explanation, each of the constituent parts of the invention will be described in succession before explaining their implementation. FIG. 1 illustrates the surroundings of, that is to say what is situated close by, the vessel head of a pressurised water nuclear reactor, and which is necessary for the invention. A vessel head 1 is provided with penetrations 2 which allow the rods of the control rod clusters, not shown, to pass through, which rods are controlled by mechanisms 3. A ventilation circuit cools the mechanisms 3. This circuit consists of an enclosure 4 surrounding the control mechanisms 3. Ambient air, which is sucked in above the enclosure 4 at its upper part 5, redescends into the volume of the enclosure 4 along the control mechanisms 3 and is sucked into one of the ducts 6, only one of which is shown. A chamber 7, normally called the "interior of the casing" is bounded by the vessel head 1 and thermal insulation plates 8 and 9. This cheer 7 confines the interfaces or junctions 10 between the penetrations 2 and the upper wall of the vessel head 1; it is at these interfaces or junctions that the possible leaks which the invention aims to detect emerge or appear. In normal operation, the ventilation circuit of the control mechanisms 3 of the rod clusters sucks the air into the chamber 7 through the clearances 11 which exist between the plates 8, 9 and the penetrations 2. These clearances 11 differ, and the local air flow rates around the penetrations 2 are not homogeneous. The function of the pick-off circuit according to the invention is that of sucking out a sample of air contained in the volume of the chamber 7, which sample is loaded with water vapour released by the leak. One of the difficulties raised by the pick-off technique resides in the fact that the air sample must be picked off before the water vapour is diluted in the high throughput of ventilation air which flows in the enclosure 4 then in the ducts 6. This difficulty is solved by a particular arrangement of the picking off which consists in continuously sucking the air to be analyzed within the volume of the chamber 7. This suction is provided using pipes 12 provided with tubes 13 which emerge into the chamber 7. All the pipes 12 are grouped on a common manifold 14. A pump 15 carries out the sampling of the air picked up from the volume of the chamber 7. Similarly, another pipeline 16 connected to another pump 17 picks off a sample of air from the containment 100 of the building of the reactor. A measurement assembly 18 is connected in by-pass to the manifold and pipeline 14 and 16 respectively, to measure the difference in concentration of the tracer in the two samples flowing in this manifold and pipeline pair 14 and 16. A leak is detected when the difference in concentration between these two samples is greater than the normal measurement uncertainties of the measurement assembly. This measurement assembly comprises improvements aiming to limit or detect: malfunctions of the tracer detector, with a view to avoiding false alarms. This measurement assembly 18 is connected to a control and processing unit 19 comprising a suitable, appropriate, preferably industrial, computer which allows control and command of the transmitters and actuators necessary for the measurements and for their interpretation. This unit is advantageously housed outside the containment of the building of the reactor. FIG. 2 illustrates a plan view of FIG. 1. The suction pipes 12 allowing picking off of air from the chamber 7 are seen. These pipes are connected to the common manifold 14. The pump 15 allows the gas contained in the manifold 14 to be transported. The pipes 12 advantageously run above bands 20 which constitute the upper thermal insulation plates 9 onto which they are fixed. A smaller number of tubes 13, which pass through the thermal insulation only, are connected to the pipes 12 and allow the picking off of air in the chamber 7. An expedient arrangement of these pick-off tubes 13 makes it possible to cover the entire detection region homogeneously. This configuration of the pick-off circuit has the essential advantages of simplicity, easy installation because of the attachment of the pipes 12 and the bands 20, and the limited number of pick-off points. FIG. 3 illustrates a plan of a variant of the circuit for picking off the air from the chamber 7. Its essential advantage over the one previously described is that each penetration 2 is surrounded by four pick-off tubes 13 arranged practically in a square, thus making detection of the leaks easier because of the individual monitoring of each penetration 2. The pick-off tubes 13 are connected to the pipes 12 which are solidly attached to the thermal insulation bands 20 and are connected together by the common manifold 14 in a manner similar to that previously explained. The sections of the pipes 12 and of the tubes 13 are such that the suction flow rates are balanced for all the penetrations 2. Identical sensitivity for detecting the leaks is thus obtained, whatever the position of the defective penetration 2. FIG. 4 illustrates another variant of the circuit for picking off air from the chamber 7. One of the technical difficulties raised by the picking off is that this pick off must be homogeneous throughout the chamber 7 so that the sensitivity of the technique for detecting the leaks does not depend greatly on the position of the defective penetration 2. This difficulty is resolved by a particular arrangement of the pick-off circuit, which consists in installing, as illustrated, at least one sleeve 22 in by-pass between a suction duct 6 of the ventilation circuit of the mechanisms 3 for controlling the rod clusters and the chamber 7. By a "water pump" effect, a suction flow is created in the sleeve 22 which depressurises the chamber 7. This flow and this pressure reduction are regulated using a damper 23 and a differential pressure sensor 24 so that the chamber 7 is at a very slightly lower pressure than the enclosure 4. The flow of air is then reversed between the enclosure 4 and the chamber 7, and all the air sweeping the chamber 7 is taken up by the sleeve 22. In the event of a leak, this sweeping air collects all the tracer released, independently of the position of the defective penetration 2. The sweeping air passes into the sleeve 22 where the pick-off manifold 14 sucks out a sample using the pump 15. The pipeline 16, connected to the pump 17, also picks off a sample of the ambient air in the confinement enclosure 100. The measurement assembly 18 is connected, as indicated previously, in by-pass on the manifold and pipeline pair 14 and 16, to measure the difference in concentration of the tracer in the two samples flowing in this manifold and pipeline 14 and 16. The sensor 75, such as, for example, a hot-wire anemometer or a Pitot tube, makes it possible to determine the flow rate through the sleeve 22. Measuring this flow rate, combined with the humidity measurements described below, allows an estimate of the possible flow rate of the leak detected. FIG. 5 illustrates the functional branchings and connections of the measurement assembly 18. Two by-pass lines 25 are connected to the pick-off pipeline and manifolds 16 and 14, and to a three-way solenoid valve 26 whose function is alternately to send a sample of air flowing in the manifold and pipeline 14 and 16 to a filter 27. The function of this filter is to remove the dust and vapours other than the water vapour, to avoid fouling of the humidity detectors 28 and 29 or hygrometers which are connected to the filter 27 and mounted in parallel. An absolute-pressure sensor 30 allows water vapour partial pressure correction in each sample coming alternately from the manifold and from the pipeline 14 and 16, in the event of pressure differences existing between this manifold and this pipeline 14 and 16. The overall flow rate through the humidity detectors 28 and 29 is measured using a flow meter 31. A pump 32 provides the pressure reduction necessary for the air to flow through the measurement assembly 18. The flow rate in each of the pick-off pipeline and manifold 16 and 14 is provided by the pumps 17 and 15 respectively, and is measured by the flow meters 34 and 33. A temperature sensor 35 measures the temperature of the sample to be analyzed and makes it possible to ensure that the detectors are used in their measurement range. A temperature sensor 36 measures the ambient temperature in a cabinet 37 where the measurement assembly is placed. This cabinet 37 is thermostated and provided with appropriate conventional dismountable connectors for linkage with the assembling circuit. The solenoid valve 26, the measurement output of the humidity detectors 28, 29, of the pressure sensor 30, of the flow meters 31, 33, 34, and of the temperature sensors 35, 36 are connected to a measurement and control system 38 associated with a computer 39 which, together, constitute the processing and control unit 19. This unit 19 fulfils the functions of control, measurement, interpretation of the measurements and control of the alarms. The connections with the measurement assembly 18 are diagrammatically represented in broken lines. The uncertainties in measuring the difference in concentration of the tracer are greatly reduced by the alternate "switch-over" of the samples on the same detectors. This makes it possible to cancel systematic errors and slow drifts of the detectors when calculating the difference in concentration. When the difference in the tracer concentration measurements of the two samples is greater than the normal measurement uncertainties of the two detectors, taking into account the cancellation of systematic errors and the absolute pressure correction, the unit 19 indicates the presence of a leak and triggers a "leak" alarm 40. Measuring this difference in concentration makes it possible to calculate the leakage flow rate by virtue of the prior knowledge of the sweeping flow rate passing through the chamber 7. This sweeping flow rate can be estimated by using one of the techniques provided according to the invention and described below. The presence of two identical detectors measuring the same concentration makes it possible to compare their indications and therefore to detect an excessively high measurement difference. Such an abnormal difference indicates malfunction of at least one of the detectors. In this event, a "system" alarm 41 is generated by the processing and control unit 19 to initiate a servicing operation or replacement of the detectors. The monitoring is designed so as to minimise the frequency of false "leak" alarms. The unit 19 regularly monitors the various functions of the measurement chain and triggers the "system" alarm 41 in the following non-limiting cases: excessively low airflows through the manifold and pipeline 14 and 16, measured by the flow meters 33 and 34, PA1 excessively low flow of air through the hygrometers 28, 29, measured by the flow meter 31, PA1 excessively low or excessively high temperature of the air sample analyzed by the humidity detectors 28, 29, and measured by the sensor 35, PA1 difference between the temperature of the cabinet 37, measured by the temperature sensor 36, and the dew temperature measured by one of the humidity detectors 28 or 29, being less than a certain threshold. When the dew temperature measured by the humidity detectors 28 and 29, and the temperature of the cabinet 37, measured by the temperature sensor 36, are very close, the unit 19 triggers a particular alarm 42 indicating "saturation" of the measurement. Degradation of the humidity detectors 28, 29 is reduced by the presence of the filter 27 which greatly limits fouling of these detectors. The humidity detectors 28 and 29 are, for example, cooled-mirror, lithium chloride or capacitive hygrometers. The measurement means advantageously operate by cooled-mirror hygrometry. It is possible in particular to use hygrometers having a cycle of virtual cleaning of the mirror so as to limit its servicing. These mirror hygrometers give a precise indication on the dew temperature of the sampled air. FIG. 6 diagrammatically illustrates a leak simulator allowing evaluation of the air flow passing through the chamber 7. This evaluation can be made during hot shutdown, preceding restarting of the reactor, in order to benefit from conditions as close as possible to those of the operation of the pick-off and leak detection devices. This simulator device uses a tracer gas, such as helium, which is advantageously detected by mass spectrometry. This gas, being inert and non-toxic, can be employed with ease. Using a mass spectrometer for the detection allows a large dynamic measurement range. The essential difficulty encountered in using this gas resides in the representivity of the vapour leak to be simulated. This difficulty is surmounted by using a tracer gas mixture such that its density is as close as possible to that of the water vapour coming from a leak. It is, for example, possible to use a mixture of air (53%)--helium (47%) or alternatively a mixture of neon (82%)--helium (18%). Furthermore, the gas mixture flow rate used is identical to that of the minimum leak which the device previously described aims to detect, i.e. 1 kg/h. Finally, the injection is carried out as close as possible to the head/penetrations 1/2 interfaces or junctions 10, this being the place where the leaks appear. The technique used is as follows. A continuous flow of a tracer gas mixture contained in a cylinder 43 is injected into the chamber 7 through a mass flow rate regulator 44, allowing control of this flow. The tracer gas mixture is transported into the chamber 7 through an immersed injector 50 which emerges near a head/penetration interface 10. The helium mixes with the sweeping air passing through the chamber 7. The pick-off circuit, as described with regard to FIGS. 1, 2 or 3, allows the gas to be transported to a mass spectrometer 45. This mass spectrometer allows measurement of the helium content of the gas transported by the pick-off circuit, at the output of the pumps 15 and 17. A multi-way valve 47 makes it possible to take a measurement either from the air sampled from the chamber 7 or from the air sampled from the outside 100 of the chamber 7, which is used as a reference. Calculating the ratio of the helium concentrations measured in the manifold and pipeline pair 14 and 16 makes it possible to calculate the dilution of the tracer and to calculate therefrom the local sweeping flow rate of air in the chamber 7. Most of the helium injected into the chamber 7 is taken up by the ventilation of the control mechanisms 3 of the rod clusters through the suction ducts such as 6. After passing over cooling coils, not illustrated, the air and the helium which is contained therein recirculate into the building of the reactor 100. The helium therefore partly accumulates in the reactor building because of the closed-circuit ventilation of the control mechanisms 3. This accumulation of helium in the building of the reactor is taken into account by making, in an original manner, an additional measurement which allows calibration of the signals delivered by the mass spectrometer 45. In order to do this, use is made of a gas reserve 49 containing helium at a perfectly known level, which is connected, via a line 48, to the multi-way valve 47 which is itself connected to the mass spectrometer 45. This gas reserve 49 may quite simply be the atmospheric air which naturally contains 5.2 parts per million of helium. The successive measurements of the helium content in the manifolds, pipeline and line 14, 16 and 48 allow better evaluation of the local flow rate of sweeping air in the chamber 7. Different local sweeping flow rates can be calculated from as many points of injection into the chamber 7. The maximum sweeping flow rate locally measured is then adopted for checking that the measurement assembly 18, taking into consideration its intrinsic performance, can detect a primary water vapour leak of 1 kg/h. This technique can be applied after each reassembly of the thermal insulation and of the constituent elements of the pick-off circuit, in order to ensure correct operation thereof. Its use can be limited to injecting the tracer mixture at a single point: the one where a maximum local sweeping flow rate has been measured during previous tests. FIG. 7 partially and diagrammatically illustrates the simulator of a leak of water vapour into the chamber 7, nearest the head/penetrations 1/2 interfaces or junctions 10. Injecting water vapour into the chamber where the possible leaks emerge is particularly advantageous in the case when the leak detection device used is based on the humidity detection according to the invention. This injection of a known flow of water vapour makes it possible simultaneously to check that the detection device is operating properly, that it has sufficient sensitivity and that the pick-off system is operating correctly. A first entity is composed of a containment 51 containing water heated to boiling point using a heating element 52. The vapour thus produced, whose flow rate is regulated by a flow rate regulator 53, is transported into the chamber 7 through a line 54 after passing through a superheater 55 in order to prevent any condensation of water before it enters the chamber 7. A second and a third entity are used for introducing water into the chamber 7 and to make use of the high temperature which exists therein to convert this water into vapour. The second entity is a pneumatic atomizer assembly consisting, on the one hand, of a water supply 56 passing through a filter 57 and a pressure regulator 58 and, on the other hand, of a compressed air supply 59 passing through another filter 60 and a pressure regulator 61. Two water 62 and air 63 conduits penetrate the chambers 7 where they supply a nozzle 64 whose characteristics are known. This nozzle allows atomisation of the water with a known flow rate, in proximity to a head/penetration 1/2 interface or junction 10. The sufficiently high temperature existing in the chamber 7 converts the water droplets into vapour. The third entity consists of a tank 65 containing water which passes through a filter 66 and a flow rate regulator 67. This water is transported by a conduit 68 into the chamber 7 in a cartridge 69. This cartridge 69 mainly consists of a heat-resistant and water-permeable material such as a sintered metal, glass fibre or high-density steel wool. The sufficiently high temperature existing in the chamber 7 converts the water flush with the surface of the cartridge into vapour. The method is implemented in the following manner using the device previously described. The procedure for detecting leaks is as explained below. With the ventilation of the rod cluster mechanisms 3 being in operation, a flow of sweeping air passing through the volume of the chamber 7 is set up. Air is picked off from the volume of the chamber 7 continuously using the pump 15 installed in the intake manifold 14. Another air sample 100, outside the volume of the chamber 7, is picked off continuously using the pump 17 mounted on the intake pipeline 16. In both cases, the pick-off is carried out at a low flow rate (approximately 3 m.sup.3 /h each). Sampling of approximately 100 l/h, made by the pump 32, allows air to be analyzed to be let into the humidity detectors or hygrometers 28 and 29. This air comes alternately from the manifold and pipeline 14 and 16. The switch-over of the sampling is made periodically by the solenoid valve 26. The time period of this switch-over is approximately 20 min, for example. The first step is waiting for the signals delivered by the hygrometers 28, 29 to stabilize. No "leak" alarm 40 can be generated during this time. In a second step, signals delivered by each of the hygrometers 28, 29 are recorded periodically. The means of the measurements made are then calculated. These values are displayed by the computer 39. Following this calculation, the unit 19 first assesses the detection system. A "system fault" alarm 41 is generated in the event that the thresholds for correct operation of the equipment are exceeded or in the event of an excessively large disparity in the signals delivered by the hygrometers. The computer 39 then compares the means of the measurements acquired in one of the pick-off lines with the mean of the measurements acquired in the other pick-off line. If the difference of the measurement averages calculated exceeds a certain threshold, a "leak" alarm 40 is generated by the unit 19. The natural presence of water vapour in the volume of the chamber 7 gives a stable indication and does not prevent high measurement sensitivity. It is possible to detect dew temperature variations between the two pick-off lines which are of the order of 0.4.degree. C., and leaks of water vapour in the chamber 7 of the order of 1 kg/h under unfavourable conditions (high sweeping flow rate in the volume of the chamber 7 and high ambient dew temperature). The presence of a leak is always characterized by a statistically stable increase in the quantity of water vapour measured in the pick-off made in the chamber 7, with respect to the water vapour content measured outside this chamber. In order to evaluate the leaks detected, the procedure is as below. The indication of the flow rate of sweeping air passing through the volume of the chamber 7 and taken up in whole by the sleeve 22, combined with the measurements delivered by the hygrometers 28 and 29, displayed by the computer 39, allows the operator of the nuclear installation to calculate and to periodically monitor the development of the leak possibly detected. In the case when the pick-off is carried out as illustrated in FIGS. 1, 2, or 3, the use, on each restart of the installation, of a leak simulation technique, using either a tracer gas mixture including helium, or water vapour, makes it possible to evaluate the maximum local sweeping flow rate passing through the volume of the chamber 7. This evaluation and the indications provided by the hygrometers allow the operators of the nuclear installation to estimate a maximum value of the flow rate of the leak detected. In order to check correct operation of the pick-off and leak detection devices, the procedure explained below is preferably carried out periodically. Whatever the pick-off device used, one of the leak simulation techniques proposed can be employed on each restart of a reactor. Either a tracer gas mixture containing helium, or water vapour, is injected into the volume of the chamber 7 with a flow rate corresponding to that of the leak which it is desired to detect. In the first case, the detection is made with the mass spectrometer 45 and only correct operation of the pick-off system is checked. In the second case, detection is carried out with the humidity detectors 28 and 29, and correct operation of the pick-off system used and of the measurement assembly 18 are simultaneously checked by triggering the alarm 40 corresponding to the appearance of a leak. The techniques of programming a computer are well known and do not form part of the invention. From the above description, the benefit of the invention is clear and the advantages which it provides are understood, especially as regards safety by allowing very early modification of the operational regime of the nuclear installation, in order to switch it over to a planned fall-back solution.
	abstract	A control rod drive mechanism according to the present invention includes a cylindrical guide tube having a latch hole, a hollow piston coupled to the control rod and freely moving up and down within the guide tube, a latch provided in the hollow piston so as to freely swing and freely engaging with and disengaging from the latch hole of the guide tube, and a spring locking the latch to the latch hole of the guide tube. Further, an elevating member having a latch guide which can come into contact with the latch is provided so as to freely move up and down within the guide tube. Further, the latch includes a guide surface coming into contact with the latch guide of the elevating member, and the latch guide includes a guide roller coming into contact with the guide surface of the latch.
	summary
	abstract	A modular light unit for illuminating a hazardous underwater environment includes a housing having a front portion with a light transmissive window and a back shell portion which enclose a layered lighting assembly. The layered lighting assembly includes a PCB with an array of LEDs mounted thereon with the LEDs in thermal communication with a bottom surface of the PCB. A thermal bridge abuts the bottom surface of the PCB on one side and a heat sink on the other. A thermally conductive potting material fills spaces between the heat sink and the back shell portion. An underwater connector provides releasable connection to an electrical cable for providing power to drive the plurality of LEDs. A quick-release mechanical fastener is attached to the housing for releasably attaching the modular light unit to a support structure installed within the hazardous underwater environment.
	abstract	A water lubricated composite thrust bearing of a nuclear main pump has a stainless steel base and an engineering plastic layer. The stainless steel base is provided with a concave-convex surface connected to the engineering plastic layer. The concave-convex surface and the engineering plastic layer are compositely molded by means of thermoplastic compound molding. A ratio of the area of the concave-convex surface to the area of an orthographic projection of the concave-convex surface on the stainless steel base ranges from 1.2 to 2. By means of the concave-convex surface and a specific bonding property obtained after fusion of a rough face and the engineering plastic layer, the concave-convex surface is bonded with the engineering plastic layer, thereby forming a reliable composite thrust bearing that is physically connected onto a whole.
	description	1. Field of the Invention The present invention relates to an ultraviolet laser sterilization system, especially to an ultraviolet laser light scanner for generating and receiving ultraviolet laser light having a wavelength of 266 nm. The system takes advantage of laser collimation as well as ultraviolet-C (UV-C) sterilization for effectively achieving the efficacy of comprehensive sterilization and disinfection rapidly and flawlessly. 2. Description of Related Art There are ubiquitous microorganisms in the living environment, e.g. air, utensils and hands. Therefore, when conducting microbiological experiments in a laboratory or hospital, researchers should make all demanded utensils used in experiments to stay in a sterile state so as not to affect the experiments and the results thereof. A sterilization technology is a process on the premise of keeping the nature of matter to destroy all microorganisms, e.g. all bacteria, spores, viruses, fungi and so on, by means of physical or chemical methods. Accordingly, a sterilization technology can effectively be used to control or inhibit the growth of a particular microorganism. Nowadays, sterilization technologies are primarily classified into contact and non-contact types according to their uses. Contact type sterilization techniques include alcohol disinfection and chlorination methods. The alcohol disinfection method is conducted by use of alcohol with a concentration ranging from 70% to 75% or by wiping sterilization cotton moistened with alcohol across the objects. Alcohols have characteristics of being able to penetrate through the cell membrane of microorganisms and causing the internal cytoplasm to lose its metabolic functions due to complete solidification, so that the alcohol disinfection method can achieve the efficacy of sterilization. Up to now, many places, e.g. public transport, restaurants, and other public places, still take advantage of the traditional alcohol disinfection method for sterilization purposes. Although such a method has an ability of rapid sterilization without leaving pigmentation on a target object, many disadvantages still exist in the method, i.e. incomplete sterilization in some areas, reduced disinfection efficacy due to change of alcohol concentration resulting from the volatility of alcohol, time-consuming and high labor costs. The other contact sterilization technique, chlorination method, is also one of the methods commonly used in our daily life. However, recent studies have shown that chlorination is easy to make chlorine and organic reaction in the water and thus generates harmful carcinogens. Moreover, chlorine compounds are also easy to cause injury to people in use of the chlorination method for sterilization and there will be remaining chlorine left on the surface of facilities to cause surface corrosion and damage. Non-contact sterilization techniques include ozone sterilization methods and UV-C sterilization methods. Ozone is a highly efficient, fast, and secure germicide without causing repeated pollutions. At a normal temperature and pressure, it is a pale blue gas accompanied by a natural fresh taste for not only destroying bacterial spores, viruses, fungi, botulism, Fusarium, Penicillium, Bacillus subtilis, natural bacteria, Neisseria gonorrhoeae, or the like, but also killing hepatitis A and hepatitis B viruses. However, due to the complexity of designing an ozone equipment, high designing and manufacturing cost is the main disadvantage in this method. Currently, UV-C sterilization method is the safest and most reliable for rapid, complete and lowest hazardous sterilization without causing repeated pollutions. UV-C is now widely used in various fields, for example, UV lamp applications in medicine, is the best way to disinfection and sterilization of infectious viruses. UV lamps are conducted by sterilizing and disinfecting irradiated areas. However, limitation of UV irradiated areas is easy to cause unevenness UV brightness resulting in problems of incomplete disinfection and sterilization. Moreover, because most users think that the UV lamp will have disinfection effect as long as it has been lit, the recession problem of the UV light intensity has scarcely been valued by users. Besides, users generally determine the quality of UV lamps by the methods for assessing the quality of fluorescent lamp, i.e. assessing the light intensity of the lamp and ionization degree of the light by eyes. If the UV lamp without disinfection capability is continuously used by users, of course, it cannot effectively and thoroughly disinfect and sterilize the target object well. If people mistakenly believe that the object has been actually sterilized and further use it, it may lead to pathogenic phenomena such as infection and poisoning. In particular, the UV lamps are belong to emitted lights, so it must prohibit users from entering irradiated areas for fear of generating skin aging or cancerous lesion due to long-term exposure to UV light. In view of the above-mentioned problems, the object of the present invention is to provide an ultraviolet laser sterilization system, especially referring to an ultraviolet laser light scanner for generating and receiving ultraviolet laser light having a wavelength of 266 nm. The system takes advantage of laser collimation as well as ultraviolet-C (UV-C) sterilization for effectively achieving the efficacy of comprehensive sterilization and disinfection rapidly and thoroughly. Disclosed herein is an ultraviolet laser sterilization system which comprises an ultraviolet laser module and a scanning module. The ultraviolet laser module emits an ultraviolet laser light with a wavelength ranging from 200 nm to 280 nm. The scanning module includes a plurality of reflectors for receiving the ultraviolet laser light, and a controller for controlling the rotation of the reflectors to adjust an angle of emergence of the ultraviolet laser light for sterilizing a target. Therefore, by using the ultraviolet laser sterilization system, users can save much more time as well as labor costs. The present invention takes advantage of laser collimation as well as the UV-C sterilization for effectively achieving the efficacy of thorough sterilization and disinfection. Moreover, the present invention can be an adjustable sterilization system by adjusting reflectors to change the angle of emergence, which also has an advantage of complete sterilization. According to an embodiment of the present invention, the wavelength of the ultraviolet laser light is 266 nm. The ultraviolet laser light irradiates an area ranging from 1 mm2 to 4 mm2 and has 5 kilowatts (KW) peak power of the light intensity. According to an embodiment of the present invention, the system can be further provided with an ozone detector module electrically connecting to the controller. The ozone detector module is used to detect the ozone concentration in the environment, convert the ozone concentration into an electrical signal and transmit the electrical signal to the controller. The controller further adjusts the power and the irradiation time of the ultraviolet laser light on a target according to the signal. First, for a better understanding of the present invention, the basic concepts including laser collimation and UV-C sterilizing will be briefly described as followings. The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation. Laser provides energy for active working media (gain medium) by the excitation system to amplify any photons passing through it. These photons can bounce within the laser cavity dozens to hundreds of times and finally go straight through the laser cavity to form a laser beam. Although the laser beam may disappear in the laser cavity if the forward direction of the laser beam is slightly non-parallel, the disappeared laser beam can be obtained again by fine tuning the system. Therefore, laser beam has a better directivity, a better collimation, and the precise dosage controlling ability of the single-point fast scanning. Furthermore, UV-C light has a wavelength of 253.7 nm, which is also generally known as a germicidal light, playing a great role in destroying the harmful bacteria, viruses, and other microorganisms. UV-C irradiation can directly cause damages to the DNA, RNA and other structures of the microorganisms leading to proteins that make up the microorganisms cannot form, so it will result in an immediate death or loss of propagation ability of the microorganisms. Generally, UV-C irradiating an object for 1-2 seconds can achieve a good result in sterilization, whereas the ozone disinfection and chlorination methods require taking several minutes or longer to achieve the same result. Accordingly, the UV-C disinfection method has been confirmed to be a disinfection and sterilization technique having many advantages of time saving, no pollution, easy operation, and lower maintenance costs. Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. Referring to the FIGURE, a block diagram showing an ultraviolet laser sterilization system according to the present invention is revealed. The ultraviolet laser sterilization system comprises: an ultraviolet laser module (1) emitting an ultraviolet laser light (11) with a wavelength ranging from 200 nm to 280 nm; and a scanning module (2) including a plurality of reflectors (21) for receiving the ultraviolet laser light (11), and a controller (22) for controlling rotation of the reflectors (21) to adjust an angle of emergence of the ultraviolet laser light (11) for sterilizing a target (4). The ultraviolet laser light (11) with a wavelength of 266 nm mainly irradiates an area ranging from 1 mm2 to 4 mm2 and has 5 kilowatts (KW) peak power of the light intensity. Moreover, the system can be further provided with an ozone detector module (3) electrically connecting to the controller (22) for transmitting a signal of ozone concentration detected in the environment to the controller (22), so as to allow the controller (22) to adjust the power and the irradiation time of the ultraviolet laser light (11) on a target (4). When assembling the abovementioned system, an ultraviolet laser module (1), a scanning module (2) comprising a plurality of reflectors (21) and a controller (22), and an ozone detector module (3) are installed to form an ultraviolet laser sterilization system having a scanner structure. This ultraviolet laser sterilization system can be an adjustable sterilization system by adjusting reflectors (21) to change the angle of emergence of the ultraviolet laser light (11), so it has an advantage of completely and rapidly sterilizing a target (4) well. The ultraviolet laser sterilization system is conducted by irradiating a target (4). After turning on the scanner, an ultraviolet laser light (11) having a wavelength ranging from 200 nm to 280 nm will be emitted from the ultraviolet laser module (1). Then the ultraviolet laser light (11) will eject from an opening of the scanner via the built-in reflector (21) of the scanning module (2) after reflection. Sterilization is conducted whenever users aim the emitted ultraviolet laser light (11) at a target (4). In addition, users can adjust an angle of emergence of the ultraviolet laser light (11) depending on their demand by a built-in controller (22) of the scanning module (2) for controlling rotation of the reflectors (21), so they can effectively control not only the laser scanning location but also a dose of the emitted ultraviolet laser light (11). The ultraviolet laser sterilization system according to the present invention can further be provided with an ozone detector module (3) for detecting an ozone concentration in the environment. The design concept is based on that ozone formed by the oxidation of oxygen atoms can penetrate into the bacteria or virus, causing DNA, RNA, and lysozyme damage and thus can effectively achieve the efficacy of sterilization. The ozone detector module (3) can transmit a signal of ozone concentration to a controller (22) by electrical connection, so as to allow the controller (22) to adjust the power and the irradiation time of the ultraviolet laser light (11) on a target (4) for thorough sterilization. According to the above description, in comparison with the traditional technique, an ultraviolet laser sterilization system according to the present invention has the advantages as following: 1. By taking advantage of laser collimation and the single-point fast scanning of the laser light as well as a precise control of the laser light intensity, the present invention solves shortcomings, i.e. uneven brightness and unstable dosage of UV lamps, to effectively achieve the efficacy of complete sterilization and disinfection. 2. The present invention equipped with an UV-C sterilization function can effectively destroy the harmful bacteria, viruses, and other microorganisms threaten to human bodies and make them an immediate death or loss of their reproductive capacity for purpose of disinfection and sterilization. 3. With a plurality of built-in reflectors to adjust the angle of emitted ultraviolet laser light, the present invention can be made into an adjustable sterilization system having an advantage of sterilization flawlessly. 4. By an addition of an ozone detector module to detect the ozone concentration in the environment, the present invention can adjusts the power and the irradiation time of the ultraviolet laser light on a target for achieving the efficacy of fast and efficient sterilization.
042253888	claims	1. A crack detection cell for checking the leakproofness of a fuel element in the deactivation swimming pool of a nuclear reactor, by measuring the gamma activity of fluids in contact with the fuel unit, said cell comprising: a double-walled chamber for resting vertically on the bottom of the deactivation swimming pool, the external wall of said chamber defining orifices which connect the gap between said walls of said chamber with the swimming pool; means for connecting said gap to a source of inert gas under pressure for creating a heat barrier between the interior of said chamber and the deactivation swimming pool; a leakproof pocket for receiving a fuel unit in a vertical position, said pocket being located inside said chamber and comprising an upper part for serving as a zone for introducing said unit and a leakproof cover for closing said pocket; means for introducing water into, and for removing water from, said pocket; heating means mounted on the lower part of said pocket and for heating water contained in said pocket by direct contact to cause a rise in temperature of a fuel element in said pocket; means for circulating said inert gas in said pocket; and means for continuously measuring the activity of the gas which has passed through the water contained in said pocket and in which the fuel element is immersed. causing circulation of inert gas in said pocket containing water in which said fuel unit is immersed, so as to entrain any fission products released by said fuel unit; and continuously measuring the activity of said circulating gas; thermally isolating said pocket containing said unit and energising said heating plates surrounding said pocket for a part of the time for which said gas is circulated; and checking the leakproofness of said unit by comparing the measurements of the activity of said circulating gas when said unit is not thermally isolated and heated and when said unit is both thermally isolated and heated. 2. A cell according to claim 1 including means for controlling opening and closing of said cover comprising at least two small linkage rods each hinged at one end to said cover and at the other end to the upper part of said pocket, and a jack of which one part is fixed to said upper part of said pocket and the other part is hingedly connected to one of said linkage rods. 3. A process for checking the leakproofness of a fuel element unit, using a crack detection cell according to claim 1, comprising:
	summary
047643331	abstract	An end closure for a nuclear fuel flask in which the gate, which is movable between open and closed positions across an end of the flask, has first and second portions which are urged apart, conveniently by spring-loaded means. A door has upper and lower wedge-shaped members mounted on and releasably connected to the respective gate portions. In use, a displacement of the gate into or out of its fully closed position effects movement of one only of the gate portions and its associated door member. As the door members are wedge-shaped the other door member is urged into or out of sealing engagement with the end of the fuel flask.
	claims	1. A multilayered spectroscopic device for use in fluorescent X-ray analysis of boron (B) contained in a sample, which device comprises a plurality of layer pairs, each pair including a reflecting layer and a spacer layer, that are laminated on a substrate; wherein lanthanum (La), an alloy containing lanthanum as a principal component or lanthanum oxide (La 2 O 3 ) is used as material for the reflecting layers, and boron is used as material for the spacer layers, a periodic length is chosen to be within the range of 7 to 14 nm and a film thickness ratio of the reflecting layers relative to the spacer layers is chosen to be within the range of 2/3 to 3/2; and wherein the multilayered spectroscopic device has a total laminated film thickness sufficient to allow a strength of reflection of B-Kxcex1 line to attain a value equal to or higher than 98% of a saturation value. 2. The multilayered spectroscopic device for use in fluorescent X-ray analysis of boron as claimed in claim 1 , wherein the total laminated film thickness is chosen to be within the range of 280 to 320 nm. claim 1 3. The multilayered spectroscopic device for use in fluorescent X-ray analysis of boron as claimed in claim 1 , wherein the film thickness ratio of the reflecting layers relative to the spacer layer is chosen to be within the range of 4/5 to 5/4. claim 1
	summary
	abstract	The invention relates to an assembly for exchanging heat between first and second fluids, the assembly comprising a central manifold communicating with one of the inlet and the outlet for the first fluid; an annular manifold disposed around the central manifold and communicating with the other one of the inlet and the outlet for the first fluid; a plurality of heat exchangers interposed radially interposed between the central manifold and the annular manifold; and a plurality of axial inlet manifolds communicating with the inlet for the second fluid, and a plurality of axial outlet manifolds communicating with the outlet for the second fluid, the axial inlet and outlet manifolds being interposed circumferentially between the heat exchangers. According to the invention, the assembly has an inlet chamber disposed at a first axial end of the heat exchangers and putting the inlet(s) for the second fluid into communication with at least a plurality of axial inlet manifolds.
	claims	1. A Terahertz (THz) electromagnetic radiation generator comprising:a composite dipole array comprising a plurality of dipoles electrically interconnected via non-linear resonant circuits; andtwo lasers configured to direct laser beams to the composite dipole array such that the laser beams cooperate with the composite dipole array to form THz electromagnetic radiation. 2. The THz electromagnetic radiation generator as recited in claim 1, wherein the lasers comprise ring type optical resonator lasers. 3. The THz electromagnetic radiation generator as recited in claim 1, wherein the lasers comprise infrared lasers. 4. The THz electromagnetic radiation generator as recited in claim 1, wherein the lasers are configured such that the laser beams are incident upon a common portion of the composite dipole array. 5. The THz electromagnetic radiation generator as recited in claim 1, wherein the lasers are configured such that the laser beams are incident upon the composite dipole array at approximately a same angle with respect to a normal to the composite dipole array. 6. The THz electromagnetic radiation generator as recited in claim 1, further comprising a transverse mode control configured to mitigate at least some transverse modes of each laser. 7. The THz electromagnetic radiation generator as recited in claim 1, further comprising a reverse mode suppressor configured to mitigate a reverse mode of each laser. 8. The THz electromagnetic radiation generator as recited in claim 1, further comprising a beam expander for expanding at least one laser beams so as to better correspond to a dimension of the composite dipole array. 9. The THz electromagnetic radiation generator as recited in claim 1, further comprising a reflector configured to reflect light from one side of the composite dipole array back toward the composite dipole array such that the reflected light constructively interferes with light from another side of the composite dipole array. 10. A Terahertz (THz) electromagnetic radiation imaging system comprising:a composite dipole array;THz imaging optics configured to direct THz electromagnetic radiation to the composite dipole array; anda laser configured to direct a laser beam to the composite dipole array such that the laser beam cooperates with the THz electromagnetic radiation and the composite dipole array to form optical electromagnetic radiation. 11. The THz electromagnetic radiation imaging system as recited in claim 10, wherein the laser comprises a ring type optical resonator laser. 12. The THz electromagnetic radiation imaging system as recited in claim 10, wherein the laser comprises an infrared laser. 13. The THz electromagnetic radiation imaging system as recited in claim 10, wherein the THz imaging optics form an image upon the composite dipole array. 14. The THz electromagnetic radiation imaging system as recited in claim 10, further comprising infrared imaging optics and an imaging sensor, the infrared imaging optics being configured to form an image upon the imaging sensor using the optical electromagnetic radiation from the composite dipole array. 15. The THz electromagnetic radiation imaging system as recited in claim 10, wherein laser beam cooperates with the THz electromagnetic radiation and the composite dipole array to form infrared electromagnetic radiation. 16. A method of frequency conversion, the method comprising:directing first electromagnetic radiation of a first frequency to a composite dipole array comprising dipoles that are electrically interconnected by non-linear circuits; anddirecting second electromagnetic radiation of a second frequency to the composite dipole array, wherein the composite dipole array radiates electromagnetic radiation at a difference frequency approximately equal to a difference between the frequency of the first electromagnetic radiation and the frequency of the second electromagnetic radiation. 17. The method as recited in claim 16, wherein the composite dipole array is resonant at the difference frequency and is further resonant at a summation frequency approximately equal to a summation of the frequency of the first electromagnetic radiation and the frequency of the second electromagnetic radiation, and wherein the composite dipole array radiates electromagnetic radiation at the difference frequency and the summation frequency. 18. The method as recited in claim 16, further comprising:mitigating at least some transverse modes of the first electromagnetic radiation;mitigating a reverse mode of the first electromagnetic radiation;expanding at least one beam of the first electromagnetic radiation to correspond to a dimension of the composite dipole array; andreflecting at least some of the radiated electromagnetic radiation at the difference frequency from a first side of the composite dipole array back toward the composite dipole array to constructively interfere with at least some of the radiated electromagnetic radiation from a second side of the composite dipole array. 19. The method as recited in claim 16, wherein the composite dipole array radiates electromagnetic radiation comprising Terahertz electromagnetic radiation. 20. The method as recited in claim 16, wherein the composite dipole array radiates electromagnetic radiation comprising optical electromagnetic radiation. 21. The method as recited in claim 20, further comprising forming a visible image based on the optical electromagnetic radiation. 22. The method as recited in claim 16, wherein the first electromagnetic radiation and the second electromagnetic radiation are within an optical frequency range and the difference frequency is in a Terahertz frequency range. 23. The method as recited in claim 16, wherein the first electromagnetic radiation is within an optical frequency range and the second electromagnetic radiation is within a Terahertz frequency range and the difference frequency is within an infrared frequency range.
	description	1. Field The present invention relates generally to nuclear reactors, and more particularly, to nuclear fuel assemblies that employ guide thimbles with tube-in-tube dashpots. 2. Related Art In a nuclear reactor for power generation, such as a pressurized water reactor, heat is generated by fission of a nuclear fuel such as enriched uranium, and transferred into a coolant flowing through a reactor core. The core contains elongated nuclear fuel rods mounted in proximity with one another in a fuel assembly structure, through and over which the coolant flows. The fuel rods are spaced from one another in co-extensive parallel arrays. Some of the neutrons and other atomic particles released during nuclear decay of the fuel atoms in a given fuel rod pass through the spaces between fuel rods and impinge upon fissile material in adjacent fuel rods, contributing to the nuclear reaction and to the heat generated by the core. Movable control rods are dispersed through the nuclear core to enable control over the overall rate of the fission reaction, by absorbing a portion of the neutrons, which otherwise would contribute to the fission reaction. The control rods generally comprise elongated rods of neutron absorbing material and fit into longitudinal openings or guide thimbles in the fuel assemblies running parallel to and between the fuel rods. Inserting a control rod further into the core causes more neutrons to be absorbed without contributing to the fission process in an adjacent fuel rod; and retracting the control rods reduces the extent of neutron absorption and increases the rate of a nuclear reaction and the power output of the core. FIG. 1 shows the schematic of a simplified conventional pressurized water nuclear reactor primary system, including a generally cylindrical pressure vessel 10 having a closure head 12 enclosing a nuclear core 14 that supports the fuel rods containing the fissile material. A liquid coolant, such as water or borated water, is pumped into the vessel 10 by pump 16, through the core 14 where heat energy is absorbed and is discharged to a heat exchanger 18 typically referred to as a steam generator, in which heat is transferred to a utilization circuit (not shown) such as a steam driven turbine generator. The reactor coolant is then returned to the pump 16 completing the primary loop. Typically, a plurality of the above described loops are connected to a single reactor vessel 10 by reactor coolant piping 20. One of the loops includes a pressurizer 22 for controlling the pressure in the reactor primary system. Commercial power plants employing this design are typically on the order of 1,100 megawatts or more. More recently, Westinghouse Electric Company LLC has proposed a small modular reactor in the 200 megawatt class. The small modular reactor is an integral pressurized water reactor with all primary loop components located inside the reactor vessel. The reactor vessel is, in turn, surrounded by a compact, high pressure containment. Due to both the limited space within the containment and the low cost requirement for integral pressurized light water reactors, the overall number of auxiliary systems needs to be minimized without compromising safety or functionality. For that reason, it is desirable to maintain most of the components in fluid communication with the primary loop of the reactor system within the compact, high pressure containment. In the processes for designing the small modular reactor, one of the fuel/core design requirements for the small modular reactor is that the reactor should have load follow capability while minimizing CVS duty, i.e., Chemical and Volume Shim system duty, which adds and removes Boron to control reactivity. In order to satisfy this requirement, a group of gray rod cluster assemblies will be moved up and down within the fuel assemblies during reactor operation to control reactivity to satisfy load follow requirements. Proper cooling of the gray rods becomes critical to ensure the safe operation of the reactor and protect the gray rods from overheating. One of the design options to keep the control rods from overheating is to form side holes in the control rod guide thimble cladding (also referred to hereafter as the sheath) near the thimble assembly end plugs. This design choice is not a problem for the integral dashpot tube designs. However, the tube-in-tube dashpot designs make it more difficult to implement this design choice because the inside dashpot assembly has to be designed such that there will be through holes existing after assembling the dashpot tube within the guide thimble tube, regardless of the installation orientation of the dashpot tube. Accordingly, a new tube-in-tube dashpot and thimble tube assembly design is desired that will provide adequate cooling without complicating manufacture. These and other objects are achieved by a nuclear fuel assembly design that has a top nozzle, a bottom nozzle and a plurality of elongated guide thimble tubes extending axially between and attached to the top nozzle and the bottom nozzle. At least some of the plurality of guide tubes have a tubular sheath that extends substantially the entire length of the corresponding guide tube with a lower end of the sheath capped by a lower end plug having an aperture extending axially therethrough. A tube-in-tube dashpot having an axially extending sidewall is disposed within a lower portion of the tubular sheath with an opening in the sidewall of the dashpot aligned with an opening in the tubular sheath. In one embodiment, the tube-in-tube dashpot has a lower end cap with an aperture extending axially therethrough that aligns with the aperture in the lower end plug of the tubular sheath. The elongated guide thimbles are connected to the bottom nozzle by a fastener that extends through the bottom nozzle, through the lower end plug of the tubular sheath and into the lower end cap in the tube-in-tube dashpot, attaching the guide thimble and the tube-in-tube dashpot to the bottom nozzle. In one embodiment the aperture in the lower end cap of the tube-in-tube dashpot is threaded and mates with a corresponding thread on the fastener. Preferably, the opening in one of the sidewall of the dashpot or the tubular sheath is oblong, extending partially around a circumference thereof with the larger diameter of the oblong opening extending in the circumferential direction. Desirably, the opening in the one of the sidewall or the tubular sheath comprises a plurality of circumferentially spaced oblong openings formed approximately at the same elevation. In one preferred embodiment, the openings in the one of the sidewall or the tubular sheath comprises two circumferentially spaced oblong openings formed approximately at the same elevation. Preferably, the two circumferentially spaced oblong openings extend substantially around the entire circumference of the one of the sidewall or tubular sheath and are spaced from one another by a distance substantially required to assure the structural integrity of the one of the tube-in-tube dashpot sidewall or tubular sheath. In one such embodiment, the opening in the other of the tubular sheath or the side wall is circular and overlaps a portion of the oblong opening in the one of the sidewall of the tube-in-tube dashpot or the tubular sheath. FIGS. 2 and 3 illustrate a small modular reactor design which can benefit from the guide thimble design principles of this invention. FIG. 2 shows a perspective view of the reactor containment of a modular reactor design to which this invention can be applied. The reactor containment illustrated in FIG. 2 is partially cut away, to show the reactor pressure vessel and its integral, internal components. FIG. 3 is an enlarged view of the reactor pressure vessel shown in FIG. 2. Like reference characters are used among the several figures to identify corresponding components. In an integral pressurized water reactor such as illustrated in FIGS. 2 and 3, substantially all the components typically associated with the primary side of a nuclear steam supply system are contained in a single reactor pressure vessel 10 that is typically housed within a high pressure containment vessel 34 capable of withstanding pressures of approximately 250 psig, along with portions of the safety systems associated with the primary side of the nuclear steam supply system. The primary system components housed within the reactor pressure vessel 10 include the primary side of a steam generator 26, reactor coolant pumps 28, a pressurizer 22 and the reactor itself having a core 14 and upper internals structure 30. The steam generator system 18 of a commercial reactor, in this integral reactor design, is separated into two components, a heat exchanger 26 which is located in the reactor vessel 10 above the reactor upper internals 30 and a steam drum which is maintained external to the containment 34 and described more fully in application Ser. No. 13/495,050, filed Jun. 13, 2012. The steam generator heat exchanger 26 includes within the pressure vessel 10/12, which is rated for primary design pressure and is shared with the reactor core 14 and other conventional reactor internal components, two tube sheets 54 and 56, hot leg piping 24 (also referred to as the hot leg riser), heat transfer tubes 58 which extend between the lower tube sheet 54 and the upper tube sheet 56, tube supports 60, secondary flow baffles 36 for directing the flow of the secondary fluid medium among the heat transfer tubes 58 and secondary side flow nozzles 44 and 50. The heat exchanger 26 within the pressure vessel head assembly 12 is thus sealed within the containment 34. The flow of the primary reactor coolant through the heat exchanger 26 in the head 12 of the vessel 10 is shown by the arrows in the upper portion of FIG. 3. As shown, heated reactor coolant exiting the reactor core 14 travels up and through the hot riser leg 24, through the center of the upper tube sheet 56 where it enters a hot leg manifold 74 where the heated coolant makes a 180° turn and enters the heat transfer tubes 58 which extend through the upper tube sheet 56. The reactor coolant then travels down through the heat transfer tubes 58 that extend through the lower tube sheet 54 transferring its heat to a mixture of recirculated liquid and feed water that is entering the heat exchanger through the sub-cooled recirculation input nozzle 50 from the external steam drum, in a counter flow relationship. The sub-cooled recirculating liquid and feed water that enters the heat exchanger 26 through the sub-cooled recirculation input nozzle 50 is directed down to the bottom of the heat exchanger by the secondary flow baffles 36 and up and around heat exchange tubes 58 and turns just below the upper tube sheet 56 into an outlet channel 76 where the moisture laden steam is funneled to the wet steam outlet nozzle 44. The wet saturated steam is then conveyed to the external steam drum where it is transported through moisture separators which separate the steam from the moisture. The separated moisture forms the recirculated liquid which is combined with feed water and conveyed back to the sub-cooled recirculation input nozzle 50 to repeat the cycle. This invention provides a new guide thimble assembly that employs a tube-in-tube dashpot design that enables enhanced cooling of the control rods and gray rods as they are moved within and out of the core to accommodate load follow. One exemplary embodiment which is specifically suited for small modular reactor fuel assemblies is illustrated in FIGS. 4, 5 and 6, though it should be appreciated that the same design is suitable for large scale reactors such as the AP1000® reactor offered by Westinghouse Electric Company LLC, Cranberry Township, Pennsylvania. The embodiment illustrated in FIGS. 4, 5 and 6 employs a tube-in-tube dashpot tube with side slots that has an end plug welded to its lower end with a threaded opening 68 extending through the bottom of the end plug. FIG. 4 is a sectional view of the lower portion of a thimble tube sheath 40 that is capped at its lower end with an annular end plug 42 that is welded to the sheath. Coolant enters the control rod guide thimble sheath 40 from the bottom nozzle, through the through the thimble screw center hole 64 shown in FIG. 6, to cool the control rods that are reciprocally movable within the thimble tube sheath 40. Side hole openings 38 in the sheath that communicate with corresponding openings in the dashpot tube provide additional coolant flow into the dashpot to enhance cooling of the gray rods or controls rods that are reciprocally movable within the sheath. The dimensions and the number of the holes/slots provided in the sheath 40 and the dashpot tube 48 are designed such that there will be at least X number of the through holes in alignment through the side of the thimble tube after assembling the dashpot tube and the thimble tube regardless of the orientation of the installed dashpot tube. This X number of through holes is determined by a thermal hydraulic analysis and may be less than the number of openings in the outer sheath or the dashpot tube wall. FIG. 5 shows the dashpot assembly 46 formed from a tubular member 48 that has an end plug 52 welded to a lower end, with a threaded opening 32 extending through the end plug into the interior of the dashpot tube. FIG. 6 shows a cross sectional view of the thimble tube assembly 70 connected to a portion of the bottom nozzle 62 with a thimble screw 64 that extends through an opening 72 in the bottom nozzle, through the thimble tube sheath end plug 42 and into the threaded opening 32 in the dashpot end plug 52. This embodiment of the design uses one or more oblong slots 66 in either the dashpot or the thimble tube sheath to align with the generally circular opening 38 in the other of the thimble tube sheath 40 or the dashpot. Four hole openings are drilled at approximately 90° apart in the thimble tube sheath 40 in this exemplary embodiment. The dashpot has two circumferentially extending oblong slots that are cut approximately 180° apart along the circumference of the dashpot tube 48 as shown in FIG. 5. The integrated tube-in-tube guide thimble assembly 70 and a portion of the bottom nozzle top plate 62 through which the thimble screw 64 extends is shown in FIG. 6. The integrated tube-in-tube guide thimble assembly is assembled in such a way that the guide thimble tube/assembly is sandwiched in between the dashpot assembly and the bottom nozzle top plate by the thimble screw as shown in FIG. 6. The design of the slot dimensions and positions ensure that orientation of the installed dashpot tube will not significant impact the flow of coolant into the dashpot with at least two through holes aligned for proper cooling. It should be appreciated that the number of hole openings in the outer sheath 40 and the number of slots 66 in the dashpot tube may vary without departing from the concepts claimed hereafter. Similarly, circumferentially extending oblong openings may be provided in both the guide tube sheath and the dashpot sidewall without departing from the concepts claimed hereafter. Accordingly, this arrangement provides enhanced cooling for gray rods or control rods while employing a tube-in-tube dashpot design. It should also be recognized that the concepts taught herein are applicable to any other guide tube such as those that guide water displacement rods that employ tube-in-tube dashpots and require enhanced cooling. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	summary
051165660	summary	BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates to a machine for milling off old, cracked weld material from control rod drive penetrations used in nuclear boiling water reactor systems and more particularly to a machine that can rapidly be positioned and used so as to reduce the time exposure of workers to nuclear radiation. II. Discussion of the Prior Art The control rod drive (CRD) penetrations in a nuclear boiling water reactor (BWR) system have welded end caps. Intergranular stress corrosion cracking, (IGSCC), occurs at the weld interface because of the high heat, radiation, and fatigue environment of nuclear boiling water reactors. The cracked condition must be fixed before the function of the CRD is compromised. To prevent compromise of the CRDs, one must enter the BWR's dry well, a high radiation area, to remove the old weld material and end caps from the CRD's whose welds exhibit IGSCC and then weld on new end caps. Protective suits are required in this high radiation area and an individual's exposure time in such a high radiation environment is limited by federal regulations. The removal of the old weld material has heretofore been a highly labor intensive procedure using a hack saw and an abrasive disk grinding wheel. Such a method is time consuming, inaccurate and results in air-borne contamination in the form of radioactive dust particles. Because of the limits on radiation exposure mandated by federal regulations, the time involved removing the old weld material necessarily limits the time for welding on the new end cap. A need exists for a method which reduces time, eliminates inaccuracies and minimizes air borne contamination. The primary object of this invention is to provide a device which shortens the time for removing old weld material from the CRDs in BWR installations. Another object is to minimize the amount of air borne radioactive contamination in the form of radioactive dust. Another object is to provide a manually adjustable device which readily clamps onto CRDs adjacent to the CRD to be milled for support. SUMMARY OF THE INVENTION To achieve these and other objects, there is provided a milling apparatus for use on control rod drive penetrations in a nuclear boiling water reactor system. In such systems, CRDs are equally spaced in a grid pattern. The apparatus manually clamps onto CRDs adjacent to the CRD to be milled. The drill bit works straight down onto the CRD end to remove the cracked weld material and end cap. The waste product of the milling procedure is radioactive material in the form of chip-like scraps which are too heavy to remain air-borne and hence, there is virtually no dust. For a better understanding of the above and other features and advantages, reference is made to the following and detailed description of a preferred embodiment reflected in the accompanying drawings in which like numerals in the several views refer to corresponding parts.
	description	FIG. 1 shows diagrammatically a known arrangement for X-ray analysis with two parabolic multilayer mirrors. This arrangement is notably suitable for X-ray diffraction. The arrangement includes an X-ray source 2 for irradiating a sample 4 to be analyzed by means of the arrangement. In order to parallel as well as possible the radiation 6 incident on the sample, a device for paralleling the radiation beam is arranged in the beam pat between the X-ray source and the sample, said device being a multilayer mirror 8 for X-ray reflection in the present example. The reflecting surface of this multilayer mirror has a parabolic shape as symbolically represented by a dashed line 10. The reflecting layers provided on the surface of the multilayer mirror may have a thickness which is dependent on the location, so that a so-called graded multilayer mirror is obtained. The grading is such that when the mirror is irradiated by a (from a two-dimensional point of view) point-shaped source (being a line-shaped source perpendicular to the plane of drawing when viewed three-dimensionally), the Bragg reflection condition is satisfied in each point of the multilayer mirror, with the result that a large reflecting surface is obtained for the multilayer mirror. After diffraction of the X-rays on the sample 4, a mainly mutually parallel beam of X-rays 12 emanates from the sample. Due to interaction of the X-rays with the sample or the vicinity thereof, however, directions other than the predominant parallel direction may also occur in the beam emanating from the sample. The X-rays having such deviating directions usually affect the accuracy of the measurement; therefore, it will be attempted to eliminate such deviating beam directions from the beam 12. To this end, a further multilayer mirror 14 for X-ray reflection is arranged in the beam path between the sample 4 and an X-ray detector 16. Like the multilayer mirror 8, the multilayer mirror 14 is constructed as a graded multilayer mirror whose surface has a parabolic shape as symbolically denoted by the dashed line 18. Due to the parabolic shape of the multilayer mirrors 8 and 14, the X-ray beam emanating from the X-ray source 2 is converted, before reaching the sample 4, into a substantially parallel beam and after the sample into a focused beam again that has a focus point in the focus 20 of the multilayer mirror 14. The collimator slit 22 is arranged at the area of said focus. FIG. 2 shows diagrammatically a detail of an arrangement for X-ray analysis in accordance with the invention. A number of auxiliary lines 24a, 24b, 26a and 26b in this Figure indicate how substantially the same angular value is observed for the passage width of the collimator from every reflecting point of the multilayer mirror. (For the sake of clarity it is to be noted that said auxiliary lines do not represent rays of the X-ray beam emanating from the multilayer mirror 14, but denote only the boundaries of the angle at which the angular value of the passage width of the collimator slit 28 is seen from the points A and B, respectively.) In the embodiment shown in FIG. 2 the collimator is shaped as a collimator slit that is formed by two knife edges which are situated at different distances from the reflecting points of the multilayer mirror. The distance between the relevant reflecting point (for example, the point B) and the center 32 of the passage width of the collimator 28 can be taken as said distance, for example, as represented by the length of the line segment 30. A situation in which the angular value xcex3 or xcex4 of the passage width is substantially constant for the points of the surface of the multilayer mirror 14 that participate in the reflection can be achieved by a suitable choice of said difference in distances. (For the sake of clarity this reflecting part of the surface in FIG. 2 is shown to be much larger than the value corresponding to a practical situation.) The desired effect of enhanced resolution is achieved only if the angular value (xcex3 or xcex4) of the passage width of the first collimator, viewed from the reflecting points of the multilayer mirror, is smaller than the maximum angular range of the reflection xcex1max. Because the value of the maximum angular range is of the order of magnitude of 0.05xc2x0 for practical multilayer mirrors, it will be evident that the angles xcex3 and xcex4 are significantly exaggerated in FIG. 2. The knife edges of the collimator are displaceable, in a manner not shown in the Figure, relative to one another in a direction transversely of the direction of the beam path through the collimator. The passage width of the collimator, and hence the resolution of the apparatus, is thus controlled without introducing deviations in respect of the angular value at which the collimator slit is viewed from the various points of the reflecting surface. FIG. 3 shows diagrammatically a further embodiment of the invention. Like in FIG. 2, the collimator 28 in this Figure is shaped as a collimator slit that is formed by two knife edges which are situated at different distances from the reflecting points of the multilayer mirror, so that the same angular value of the passage width is observed from every reflecting point of the multilayer mirror. The apparatus shown in FIG. 3 is also provided with a second collimator 34 which is arranged in the beam path between the sample 4 and the X-ray detector 16. The second collimator 34 is adjustable (in a manner not shown in the Figure) in that the knife edges are displaceable relative to one another in the direction of the beam path through the collimator. The detector will always perceive a defined part of the sample when the passage width is adapted to the angle of incidence of the radiation on the sample.
	summary
063226103	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to the attached Figures, the device according to the invention is indicated in its entirety by the reference number 10. The device 10 is suitable to be mounted axially fixed on the walls of a furnace for melting metals, or a recipient in general used to perform metallurgical transformations, and has a nozzle, or emission element 23 at the end, the outlet mouth 11 of which is located at a defined distance from the upper level of the liquid bath and above the overlying layer of slag. During the operating step, the outlet mouth is located at a height, with respect to the surface of the bath, of between about 0.5 m and 2.5 m. The angle of incidence of the jet is between about 30.degree. and about 70.degree., advantageously between 40.degree. and 50.degree.. The device 10 consists of a metallic body 12 (FIG. 1), suitable to be inserted into an appropriate aperture, sealed with air-tight sealing means and made on the wall of the furnace, and to cooperate with appropriate equipment of a kind known to the state of the art, to manipulate and possibly to insert, remove, direct, etc. the device 10. With the apertures on the walls of the furnace being air-tight, it is possible to manoeuvre the movable injection organs, drastically reducing the formation of nitrogen oxides or their precursors (the so-called NOx), and thus limiting the dissipation and dispersion of energy from the machine. On the end part of the metal body 12 the emission element 23 is housed, which is innerly defined by a double nozzle configuration. To be more exact, the emission element 23 has a first nozzle 13, inside and substantially coaxial, to emit a supersonic jet of oxygen, gas containing oxygen, or other technological gases, and a second annular nozzle 14 outside and substantially coaxial with the first nozzle 13, to emit a subsonic jet of oxygen or other substances, for example solid fuel in particles or other type of fuel. In a preferential embodiment, the speed at which the flow exits from the second nozzle 14 is between 0.3 and 0.9 Mach. The nozzles, the first 13 and the second 14, are suitably sized geometrically according to mathematical criteria to obtain maximum operational and technological efficiency, according to the method of calculation described and claimed in a parallel application in the name of this Applicant. To be more exact, the geometry of the channel defined by the second nozzle 14 has a profile such as to obtain a desired correlation of the gradient of speed between the supersonic flow, the subsonic flow and the still air inside the furnace. The emission element 23 is attached to the body 12 in such a way that it can be easily and rapidly attached/detached, thus ensuring that it can be replaced in the event of wear or breakage even without interrupting the functioning of the furnace. The nozzles 13 and 14 are advantageously made of copper, stainless steel or other similar metal. According to a variant, the nozzles 13 and 14 are made entirely or partly of ceramic material, so as to reduce the need for cooling also in those steps wherein the device 10 is not working, so as to facilitate the replacement of the nozzles 13 and 14. The two nozzles 13 and 14 are arranged inside a containing shell 15 inside which the channels 16 for the cooling water to circulate in are made. According to the invention, the first nozzle 13, or supersonic nozzle, has a convergent/divergent conformation (Laval-type) defined by a neck 20 made at a position upstream of the terminal section 21 of the nozzle 13; the neck 20 defines a convergent part 13a upstream and a divergent part 13b downstream which in turn forms the terminal section 21. The second nozzle 14, or subsonic nozzle, outside and concentric with the first 13, is convergent in shape wherein the terminal section 22 converges towards the axis 17 of the first nozzle 13. In one form of embodiment, the respective terminal sections 21 and 22 of the nozzles 13 and 14 are arranged inside the outlet mouth 11 of the emission element 23 in such a way that the respective flows interact and expand inside the inner element 23 itself, before they are introduced inside the atmosphere of the furnace. The primary gassy jet emitted by the first nozzle 13 has an outlet speed which can be regulated by acting on the pressure of the gas directly upstream of the nozzle 13 itself. In the embodiment shown in FIG. 1, this pressure is regulated by a throttling valve 18 arranged on the delivery pipe feeding the gas to the first nozzle 13. The throttling valve 18 is regulated in feedback by a control unit 19 according to signals related to the instantaneous pressure of the gas as monitored respectively upstream and in correspondence with the neck 20. This system of regulation in feedback ensures that the characteristics of the jet are maintained irrespective of the conditions of pressure/temperature/density inside the furnace so that the expansion of the supersonic jet takes place entirely inside the emission element 23. As the gas passes through the neck 20, the flow accelerates from subsonic to supersonic in correspondence with the outlet section 21 of the first nozzle 13. The supersonic flow is thermally and operationally protected by the outer ring created by the secondary, subsonic and convergent flow emitted by the second nozzle 14, so that the supersonic flow is less influenced and less able to be influenced by the operating conditions inside the atmosphere of the furnace and the bath. Moreover, the secondary gas flow makes possible to reduce the speed gradients and therefore to reduce energy loss of the primary jet. In this way, the quantity of motion of the primary jet is preserved, simultaneously excluding its interaction with surrounding gases. According to the variant shown with a detail in FIG. 3, in the divergent end part of the first nozzle 13 a plurality of circumferential grooves 24 are made with the function of stabilising that underlayer of the flow leaving the first nozzle 13 which is nearest the wall. The function of the primary jet emitted by the first nozzle 13 is substantially to penetrate the bath to about half of its overall depth and to spread inside the bath, ensuring an efficiency of use which is substantially 100%. This injection substantially takes place without splashing, since the penetration of the jet is determined only by the quantity of motion possessed by the gas delivered, and not by chemical reactions. The supersonic jet also has the function of creating a depression in the bath, suitable to increase the speed of decarburation, and also to promote stirring in the bath with exchange of mass and of energy, encouraging the homogenization and uniformity of the bath. At the same time, an increase is obtained in the foaming effect and in the homogenization of the overlying slag. The secondary flow emitted by the second convergent nozzle 14 creates an outer protective ring, concentric to the jet emitted by the first nozzle 13, and has the main function of surrounding the supersonic flow, protecting it thermally and fluido-dynamically from the surrounding disturbing agents; this increases the independence of the supersonic jet from the conditions in the atmosphere of the furnace. The shape of the outlet section 22 of the second nozzle 14 can be suitably chosen, for example, circular, elliptic or other, according to the desired position and direction of the flow. The secondary flow emitted from the second nozzle 14 reaches the overlying layer of slag, starting and encouraging the combustion of the CO emerging from the bath and giving an extra energy contribution for the melting process. With the nozzles 13 and 14 shaped according to the invention, the supersonic jet emerging from the first nozzle 13 maintains the fluid threads substantially parallel for a greater length than what happens in traditional systems, without there being any dispersion of the tubular flow caused by any other gas entering inside the volume of the jet itself. Moreover, when the jet is introduced into high density fluid systems (for example water, liquid metal or other), the supersonic jet of the first nozzle 13 reaches greater depths, since this jet is equipped with a greater quantity of motion and is completely surrounded by the subsonic jet emitted by the second nozzle 14. This is completely different from what happens in traditional systems, where the primary flow of gas, already turbulent as it leaves the lance, generates a cavity in correspondence with the zone where it penetrates into the bath, thus causing a large part of the oxygen injected to leave the injection area without exerting the desired effect in the bath of liquid metal and hence causing a reduction in efficiency. The device 10, thanks to its emission characteristics described above, allows to work at a greater distance from the bath, and does not necessarily require a manipulator as used at present, with a consequent reduction in wear and consumption of its mechanical parts. According to the invention, the device 10 can operate in burner mode with a variable stechiometric ratio and variable flame length, wherein the first convergent/divergent nozzle 13 is used as a Venturi tube to mix a combustible substance and a comburent substance, such as for example oxygen or air enriched with oxygen (FIG. 4). When the device 10 is used as a burner, the second nozzle 14 can be employed, according to a variant, to emit a jet of oxygen, or air enriched with oxygen, in order to obtain a combustion in stages, and therefore to maintain the fuel/comburent ratio in the primary flow in sub-stechiometric conditions and to use the secondary comburent to complete combustion. When the device 10 is used as a burner, the double nozzle configuration 13 and 14 allows to obtain a plurality of advantages, and also to reduce the formation of NO.sub.X. In the first place, it allows to increase the efficiency of the transfer of convective heat, and minimizes the excess of total comburent needed to complete combustion. Moreover, it guarantees a high level of stability for the flame in a wide range of operating conditions, allowing to regulate the characteristics of the flame itself both in terms of length and in terms of diameter according to the type of furnace and the required processing parameters. FIG. 4 shows an operating mode with a long flame, with the outer secondary annular jet 25 consisting of oxidant-rich gas which surrounds the inner primary jet 26 which is rich in combustible gas; this functioning is particularly useful for dissolving the scrap, in the initial steps of the cycle, which are in front of the outlet mouth 11 of the device 10. According to the operating conditions of the process of metallurgical transformation, the performance of the burner can be regulated to modify the length of the flame and also the stechiometric ratios in the different zones of the flame. FIGS. 5 and 6 show a variant wherein, in correspondence with the terminal section 22 of the second nozzle 14 there are deflector elements 27. These elements 27 rotate around a pin 29 and can assume a first, substantially horizontal position (shown by a line of dashes in FIG. 6), wherein they do not interact with the jets 25 and 26, allowing the long-flame configuration in burner mode, and a second position at least partly inclined (shown by a continuous line), wherein they reduce the outlet section of the second nozzle 14, generating a swirling movement of the second, outer jet (shown by the arrows 28). According to the greater or lesser inclination of the deflector elements 27, and to the consequent greater or lesser partial closing of the outlet, the length and shape of the flame are regulated according to the desired result. According to a further variant, at least the first nozzle 13 can be axially positioned with respect to the outlet mouth 11 of the device 10, which remains fixed, however, with respect to the wall of the furnace, for example retractable, in order to ensure the stability of the flame irrespective of the conditions which are established inside the furnace. Moreover, the retractability of the first nozzle 13, if combined with the retractability of the second nozzle 14, allows to create a pre-combustion chamber of variable volume inside the emission element 23 which guarantees an efficient mix of the two gassy jets before they are introduced into the atmosphere of the furnace. In a further functioning mode, the second nozzle 14 is used to inject material in particles or in powder form mixed with a vector gas or a transporter gas (FIG. 7). The material injected can also be a combustible material of a solid type in powder form or particles, or the atomized liquid type, or of the gassy type. In this case, the primary nozzle 13 can be used to inject secondary comburent. In the embodiment shown in FIG. 8, the second nozzle 14 is used to inject solid material, such as carbon powder or lime, on a fluid vehicle, for example an inert gas or similar. This embodiment is particularly useful in order to increase the foamy slag effect and the recarburization of the liquid steel. Moreover, a contribution of chemical energy is given, with a consequent saving in electric energy, and the composition of the slag is adjusted to values more suitable for the desired operating conditions inside the furnace. In this functioning mode, the emission element 23 can be replaced to modify the shape of the second nozzle 14 from a convergent configuration (FIG. 8), to non-convergent configurations (FIGS. 9, 12) with an outlet jet which is more or less parallel to the primary jet emitted by the first nozzle 13. FIG. 11 shows a further configuration wherein the second nozzle 14 has characteristics of great convergence in order to encourage the transport of the solid fuel in powder form by means of the supersonic jet emitted by the first nozzle 13. According to a further variant, the solid fuel in powder form is injected on a fluid vehicle through the first nozzle 13 (FIG. 10), while the second nozzle 14 can be used to emit a subsonic jet to protect the primary jet delivered by the first nozzle 13. The first nozzle 13 can be used for the whole of its section or, as shown in FIG. 12, a thin axial channel 30 may be made inside it, for solid fuel to be injected; in this case, the thin axial channel 30 extends substantially as far as the outlet mouth 11 of the device 10. The gassy jets emitted by the first nozzle 13 and the second nozzle 14 form annular crowns which protect and convey the jet of fuel delivered through the axial channel 30. According to a preferential embodiment of the invention, the walls of the nozzles or channels used to inject solid fuel are lined, at least in correspondence with the bends, with wear-resistant and erosion-resistant material, for example, high resistance resins, ceramic linings or specific protective varnishes. In the configurations shown in FIGS. 8-12, it is therefore possible to inject carbon powders (to produce foamy slag and to limit the power of the furnace), or lime powders or other material of a basic nature (to passivate the slag), at the same time as O.sub.2 or other technological gases which are needed for the metallurgical treatment of the melting baths are injected. It is clear from the above description what the characteristics and advantages of using the device 10 according to the invention are. The device 10 is mounted fixed to the wall of the furnace, also with its outlet mouth 11 at a distance from the liquid bath, so that it does not require manipulators or the substitution of parts which are progressively consumed. If the device 10 is used alternately in burner mode and simple oxygen lance mode, it is possible to open the road to the supersonic jet, for example dissolving the scrap and creating a direct passage towards the bath of liquid metal without deviations and reflections which cause energy losses and a slow down in the jet. According to the specific effect to be obtained, the inclination of the lance can be varied, for example maintaining a lesser inclination during the pre-heating step, the descent of the scrap step, and the melting step, and a greater inclination in the decarburation step and the bath stirring step. Apart from this, the quantity of motion in the primary jet, together with the protection effect caused by the secondary jet emitted by the second nozzle 14 causes the primary supersonic jet emitted by the first nozzle 13 to penetrate into the bath without dispersions and without loss of speed, maintaining a high level of efficiency, in the region of 100%, and preventing dangerous and harmful splashes of liquid metal. The depression which is created in the liquid bath, due to the pressure and dynamic impulse created by the supersonic jet, causes an increase in the speed of decarburation due to the increase in local and overall stirring of the bath and the consequent increased exchange of mass and energy. This improved stirring and uniformity of the bath deriving from the turbulence caused by the supersonic jet increases the spreading process in correspondence with the interface between the slag and the metal, which entails a reduced demand for electric energy and an increase in the speeds of decarburation. The increase in decarburation then allows a greater use of the device 10 for the high efficiency injection of carbon powder, causing a further input of chemical energy with an improved slag foaming effect and a consequent greater efficiency of the arc, reduction of electrode consumption, and reduction of energy losses through the cooling elements of the furnace. Moreover, the quantity of motion of the primary supersonic jet emitted by the first nozzle 13 generates a zone wherein the post-combustion caused by the second subsonic jet delivered by the second nozzle 14 can be carried out without contact with the slag or the metal, but in a zone in close proximity with the slag itself, thus increasing the efficiency of the reaction from a value of around 35% to a value of 75% and more. The energy deriving from the post-combustion process is transferred to the drops of metal trapped between the slag by conduction, instead of by radiance as traditionally happens. When the drops of metal return to the liquid bath, they transfer their energy content to it, further reducing the demand for electric energy. The fact that it is possible to inject carbon or lime through the device 10, even autonomously and independently with respect to the supersonic jet of oxygen, increases the flexibility and versatility of the device 10 with respect to the variation in the conditions of the furnace to obtain the desired quality of the final product.
	claims	1. A process for converting hydrocarbon-containing material into a resultant gas, comprising the steps of:a. providing a finely-ground hydrocarbon-containing solid;b. providing a light hydrocarbon gas;c. mixing said hydrocarbon-containing solid and said hydrocarbon-containing gas together to form a hydrocarbon mixture;d. preheating said hydrocarbon mixture;e. providing a gasifier, said gasifier including an acceleration tube and a heat source configured to heat said acceleration tube and the contents thereof;f. feeding said hydrocarbon mixture through said gasifier tube;g. further heating said hydrocarbon mixture emerging from said gasifier tube by passing said mixture through a microwave, wherein the heat added to said mixture in said gasifier and said microwave is sufficient to crack carbon bonds within said hydrocarbon mixture in order to form a resultant mixture containing shortened hydrocarbon chains, free hydrogen, and free electrons;h. providing a magnetohydrodynamic generator, said magnetohydrodynamic generator having a conduit fluidly connected with said microwave;i. passing said resultant mixture through said magnetohydrodynamic generator, said magnetohydrodynamic generator containing an anode configured to collect said free electrons from said resultant mixture passing through said conduit, said anode configured to transmit said free electrons away from said conduit;j. providing a decelerator/heat exchanger;k. after said resultant mixture gas stream has passed through said magnetohydrodynamic generator, passing said resultant mixture through said decelerator/heat exchanger wherein a velocity and a temperature of said resultant mixture are reduced in the absence of said free electrons;l. removing solids from said resultant mixture to create a resultant gas;m. removing hydrogen gas and hydrocarbon gas from said resultant gas; andn. storing said hydrogen gas and said hydrocarbon gas. 2. The process of claim 1, wherein said gasifier and said microwave heats said resultant gas stream to at least approximately 1700 degrees Celsius before transmitting said resultant gas stream through said magnetohydrodynamic generator. 3. The process of claim 1, wherein said decelerator/heat exchanger cools said resultant gas stream to at least approximately 700 degrees Celsius. 4. The process of claim 1, wherein said hydrocarbon-containing gas comprises methane. 5. The process of claim 4, wherein said gasifier breaks hydrocarbon bonds of said methane and thereby dissociates said methane into hydrogen atoms, carbon atoms, and said free electrons. 6. The process of claim 4, wherein said magnetohydrodynamic generator removes a sufficient quantity of said free electrons to prevent the reformation of said methane downstream of said magnetohydrodynamic generator. 7. The process of claim 5, further comprising the steps of:a. providing a separator configured to separate said carbon atoms from said hydrogen atoms in said resultant mixture, said separator downstream of said magnetohydrodynamic generator; andb. separating said carbon atoms from said hydrogen atoms present in said resultant mixture in said separator such that said hydrogen atoms and said carbon atoms are separately recovered from said resultant mixture. 8. A process for converting hydrocarbon-containing material into a resultant gas as recited in claim 1, wherein said step of preheating said hydrocarbon mixture is performed by passing said hydrocarbon mixture through the convergence of a plurality of laser beams. 9. A process for converting hydrocarbon-containing material into a resultant gas as recited in claim 1, wherein said step of preheating said hydrocarbon mixture is performed by supplying a second microwave and passing said hydrocarbon mixture through said second microwave before introducing said hydrocarbon mixture into said accelerator/gasifier.
	abstract	The present invention provides an x-ray beam conditioning system with a Kirkpatrick-Baez diffractive optic including two optical elements, of which one of the optical elements is a crystal. The elements are arranged in a side-by-side configuration. The crystal can be a perfect crystal. One or both diffractive elements can be mosaic crystals. One element can be a multilayer optic. For example, the multilayer optic can be an elliptical mirror or a parabolic mirror with graded d-spacing. The graded d-spacing can be either lateral grading or depth grading, or both.
045445222	abstract	A spacer for use in a fuel assembly of a nuclear reactor having thin, full-height divider members, slender spring members and laterally oriented rigid stops and wherein the total amount of spacer material, the amount of high neutron cross section material, the projected area of the spacer structure and changes in cross section area of the spacer structure are minimized whereby neutron absorption by the spacer and coolant flow resistance through the spacer are minimized.
047708409	abstract	For operating a PWR with spectral shift during all combustion cycles and with undermoderation during some cycles only, the reactor structure is designed for receiving either one of two types of fuel assemblies, having the same geometry. All fuel assemblies have guide tubes for receiving spectral shift clusters containing fissile material but with different elements bundles so as to be able to choose the type of operation.
	description	The present invention relates to a method of smoothing a solid surface by gas cluster ion beam irradiation and to an apparatus therefor. In semiconductor devices, electronic devices, and optical devices such as photonic crystals, multilayer thin-film structures and submicrometer order (approximately in the range of from 0.1 μm to less than 1 μm) fine pattern structures are fabricated by processing a semiconductor wafer surface or the like. In semiconductor quantum devices, for example, ultrafine particles and thin lines on the order of nanometers, which are called quantum dots and quantum wires, are fabricated and arranged on the surface of a substrate. The size and surface roughness of the fine structures (thin film structures, pattern structures, and relief structures formed by an arrangement of ultrafine particles) in these devices are important factors that determine the performance of the devices. Therefore, high fabrication precision is demanded in the formation of fine structures. The precision of the fine structures depends on the precision of fabrication techniques used in the film formation process, etching process, and the like. However, it is not easy to form a fine structure with a fabrication precision of up to a few nanometers. The devices formed through the film formation process, etching process, and the like are generally formed by fabricating a great number of chips on a wafer surface, and it is difficult to fabricate uniform fine structures across the wafer surface. In order to solve these problems, a process to enhance the precision of the structures (such as a surface smoothing process) is performed on the fabricated fine structures as post-processing. An example of such a surface smoothing technique is a technique of smoothing a side wall of a pattern structure or the like by a gas cluster ion beam irradiation, disclosed in International Publication No. WO2005/031838 (Patent literature 1). Unlike a monomer ion beam, a gas cluster ion beam is known to have a large sputter component in a direction parallel to the substrate. This phenomenon is called lateral sputtering effect. Lateral movements of atoms on a substrate surface of an irradiated area irradiated with the gas cluster ion beam are caused notably by the irradiation, these phenomena of atom movements in lateral directions smooth the surface. It is reported that surface smoothing based on lateral sputtering effect is more likely to come about with vertical irradiation than with oblique irradiation (Reference literature 1). Vertical irradiation means irradiating the substrate surface at an irradiation angle of about 0 degree to the normal to the surface. The symbol “°” will be used to express the angle. (Reference literature 1) N. Toyoda et al., Nucl. Instr. and Meth. In Phys. Res. B161-163 (2000) 980. A conventional commercial gas cluster ion beam apparatus gives out a beam on the order of millimeters (beam width). On the other hand, it is noted that a range which an action of smoothing based on the lateral sputtering effect of a single cluster reaches is about ten nanometers, which is estimated to be equal to the size of a crater that would be formed when a single cluster collides with the surface. It is conventionally possible to reduce surface roughness having intervals on the order of ten nanometers or below by means of beam irradiation and to reduce surface roughness having intervals on the order of one millimeter or above by means of beam scanning. In the intermediate range, surface roughness having intervals of several tens of nanometers to about a hundred micrometers cannot be reduced. The technique disclosed in patent literature 1 above is based on the knowledge that a solid surface is smoothed notably by gas cluster ion beam irradiation at an angle of 60° to 90° to the normal to the solid surface, in comparison with nearly vertical irradiation. This technique is used to smooth the side walls of pattern structures. This technique can smooth a solid surface with unevenness (surface roughness) having short intervals on the order of ten nanometers. It has not been clear whether unevenness (surface roughness) having longer intervals (of several tens of nanometers to about a hundred micrometers) can be smoothed. Therefore, in view of the problems described above, an object of the present invention is to provide a solid surface smoothing method of reducing surface roughness having intervals of several tens of nanometers to about a hundred micrometers on a solid surface by means of gas cluster ion beam irradiation and to provide an apparatus therefor. To solve the above-described problems, a method of smoothing a solid surface with a gas cluster ion beam according to the present invention includes, wherein an angle formed between the normal to the solid surface and the gas cluster ion beam is referred to as an irradiation angle, and an irradiation angle at which the distance of interaction between the solid and the cluster colliding with the solid (effective interaction distance) dramatically increases is referred to as a critical angle, an irradiation step of directing the gas cluster ion beam onto the solid surface at an irradiation angle not smaller than the critical angle. Because the irradiation angle is greater than or equal to the critical angle, the effective interaction distance becomes much greater than when the irradiation angle is smaller than the critical angle. The wide range of interaction between the cluster and the solid brings about solid surface smoothing. The critical angle is 70°. This angle is based on the knowledge obtained from experiments. The irradiation step may include a process of directing the gas cluster ion beam while varying the irradiation angle continuously in a range not smaller than the critical angle; a process of directing the gas cluster ion beam while varying a dose of the gas cluster ion beam continuously; or a process of directing the gas cluster ion beam by combining these two processes. With such gas cluster ion beam irradiation, the solid surface is smoothed in accordance with the roughness of the surface. The irradiation step may include a process of directing the gas cluster ion beam of a dose determined with reference to a database that allows a dose to be determined from at least a desired etching amount and the irradiation angle. By directing the gas cluster ion beam of the dose determined with reference to the database, desired etching depending on the irradiation angle can be easily provided. To solve the above-described problems, a solid surface smoothing apparatus according to the present invention includes, wherein an angle formed between the normal to the solid surface and the gas cluster ion beam is referred to as an irradiation angle, and an irradiation angle at which the distance of interaction between the solid and the cluster colliding with the solid (effective interaction distance) dramatically increases is referred to as a critical angle, a gas cluster ion beam emission means adapted to emit the gas cluster ion beam onto the solid surface and an irradiation angle setting means adapted to set the irradiation angle to the critical angle or a greater angle. In the solid surface smoothing apparatus according to the present invention, the irradiation angle setting means may be configured to vary the irradiation angle continuously in a range not smaller than the critical angle. The solid surface smoothing apparatus may be configured such that it includes a database that allows a dose to be determined from at least a desired etching amount and the irradiation angle, and the gas cluster ion beam emission means emits the gas cluster ion beam of the dose determined with reference to the database in accordance with the desired etching amount and the irradiation angle specified by the irradiation angle setting means. Prior to the description of an embodiment, the principle of smoothing used in the present invention will be summarized. The inventors have discovered experimentally that when a solid surface to be smoothed, that is, a smoothing target face, is hit by a gas cluster ion beam (GCIB) at an angle, the interaction distance between the solid and the cluster extends to several tens of nanometers to several micrometers. The irradiation angle of the oblique irradiation will be described later in detail. Based on this discovery, the surface roughness of fine structure with intervals of several tens of nanometers to about a hundred micrometers can be reduced. The intervals of several tens of nanometers to about a hundred micrometers will also be referred to as long intervals, in contrast to short intervals on the order of ten nanometers. The long interaction distance ranging from several tens of nanometers to several micrometers and the mechanism of the interaction will be described first. FIG. 1A shows an image of the surface of a silicon substrate subjected to oblique irradiation of SF6 (sulfur hexafluoride) GCIB at an irradiation angle of 70°, taken by an atomic force microscope (AFM). An arrow in FIG. 1A represents the direction of GCIB irradiation, vertically projected on the surface of the silicon substrate. In FIG. 1A, the irradiation angle is defined as an angle formed by the normal to the surface of the silicon substrate and the GCIB. On the surface of the silicon substrate subjected to oblique irradiation at an irradiation angle of 60° or greater, a striped structure leaving a trail in the direction of GCIB irradiation was observed, as described in Reference literature 1. Detailed observation revealed that the striped structure was a group of many stripes 110 having lengths of the same order and the same orientation. If the stripes 110 are formed as a result of interaction between each cluster and the solid surface, it is expected that the length of the stripe 110 would represent the distance of interaction given by the cluster, hereinafter referred to as an effective interaction distance (see FIG. 1B). A Fourier transform was performed on the AFM image to examine the effective interaction distance in a wide angular range. A Fourier transform was performed in two directions: GCIB irradiation direction vertically projected onto the solid surface (projected irradiation direction) and a direction perpendicular to that direction on the solid surface. The results are shown in FIG. 2. As FIG. 2 clearly shows, an increased irradiation angle increased the effective interaction distance in the direction parallel to the projected irradiation direction. When the irradiation angle was 70° or greater, the effective interaction distance increased dramatically. With an irradiation angle of 80°, the effective interaction distance extended to 1 μm. While the irradiation angle was 80° or greater, the striped structure was not able to be observed clearly because of the surface smoothing effects, and the data was not able to be shown in FIG. 2. However, it is expected that the effective interaction distance would increase further with an increase in irradiation angle. In a direction perpendicular to the projected irradiation direction, the effective interaction distance was nearly uniform at any irradiation angle within the range of 20° to 70°. The distance was likely to decrease slightly at an irradiation angle outside the range of 20° to 70°. However, clear dependence on the irradiation angle was not observed across the entire range of 0° to 90°. Those observations suggest that the interaction between the cluster and the solid surface occurs in a long range just in the GCIB irradiation direction. A verification experiment was conducted to verify whether the effective interaction distance actually extended to the order of micrometers at an irradiation angle of 83°. In the verification experiment, a variety of line-and-space pattern structures having different pattern intervals were fabricated on the surface of a silicon substrate. The structures were considered to be artificial surface roughness, and it was examined how the interaction with the GCIB changed the artificial surface roughness. The irradiation angle here was 83° to the normal to the surface of the silicon substrate. On the basis of the angle definitions shown in FIG. 3, θ was 7°, and φ was 90°. The definitions of irradiation angle and the like in FIG. 3 will be described. In a line-and-space pattern structure, let the longitudinal direction of the line (the projecting part in the line-and-space pattern structure) be the x-axis, the direction of line depth be the z-axis, and a direction orthogonal to the x-axis and z-axis be the y-axis. On a side wall of a line (a wall in the direction of line depth), the irradiation angle θ is an angle formed by the y-axis (normal to the side wall of the line) and the GCIB. The irradiation angle θ is a complementary angle of the angle formed by the GCIB and the GCIB irradiation direction vertically projected onto the side wall of the line. The irradiation inclination φ is an angle formed by the x-axis and the GCIB irradiation direction vertically projected onto the side wall of the line. If the effective interaction distance is very small in comparison with the pitch of the line-and-space pattern, the line-and-space pattern structure would be etched to an almost similar figure, without changing the surface roughness as a result. If the effective interaction distance is nearly equal to or greater than the pitch of the line-and-space pattern, etching of a line would affect adjacent spaces (groove parts in the line-and-space pattern structure) and adjacent lines, and the lines would be cut to fill the space with the cuttings. As a result, it is expected that this would smooth the form of the line-and-space pattern structure, reducing the surface roughness. The line-and-space pattern structure here had the same line-to-space ratio of 1:1, irrespective of the pitch of the line-and-space pattern. Therefore, the artificial average surface roughness before the GCIB irradiation, that is, the average depth of the spaces (or the average line height in the line-and-space pattern structure), was fixed to about 15 nm. FIG. 4 is a graph showing the results of the verification experiment. As clearly shown in FIG. 4, with the pitch of the line-and-space pattern, that is, the gap between adjacent lines, being smaller than about 2 μm, the surface roughness after GCIB irradiation was dramatically reduced. In FIG. 2, the value would be greater than the effective interaction distance at an irradiation angle of 80°. It is expected that the value would correspond to the effective interaction distance at an irradiation angle of 83°. The experiment demonstrated that the long-distance interaction effects created by oblique irradiation smooth the surface roughness having long intervals. As has been described above, it has been discovered that the oblique GCIB irradiation to the smoothing target face dramatically increases the effective interaction distance, that is, the distance of lateral movement of a substance (in a direction nearly parallel to the target face), to several tens of nanometers to several micrometers. On the basis of a mechanism described below, the distance of lateral movement of a substance would not be limited to several micrometers and could increase further to a hundred micrometers, with some combination of a solid surface state and the angle of GCIB irradiation. This discovery indicates that surface roughness having long intervals of several tens of nanometers to a hundred micrometers, which was heretofore difficult to reduce, can be reduced. The mechanism that the oblique GCIB irradiation to the smoothing target face increases the distance of lateral movement of a substance with an increase in irradiation angle is assumed to be as follows. An increased irradiation angle decreases the kinetic energy component of the cluster in the vertical direction (direction nearly perpendicular to the smoothing target face), increasing the kinetic energy component in the lateral direction. In comparison with the vertical atomic density of the solid, the lateral atomic density is very small because atoms in the direction nearly parallel to the solid surface (lateral direction) exist only in projecting parts of the surface. The average distance between the point where the cluster enters the solid at an angle and the point where the cluster loses its energy when it collides with atoms (projecting part) is longer than that in vertical irradiation. The cluster colliding with a projecting part sometimes cuts the tip thereof and puts the cuttings into a nearby hollow on the surface. A small density of projecting parts that would block the lateral movement makes the lateral movement easy for the atoms to be sputtered or moved laterally. With these effects, an increase in irradiation angle is considered to increase the distance by which a single cluster can move a substance on the solid surface laterally, that is, the effective interaction distance. FIG. 2 shows that the effective interaction distance dramatically increases at a certain irradiation angle in the direction parallel to the projected irradiation direction and that the irradiation angle is 70°. The irradiation angle at which the effective interaction distance increases dramatically is referred to as a critical angle. The mechanism providing a dramatic increase in effective interaction distance at an irradiation angle of 70° or greater is considered to be associated with the dissociation process when the cluster collides with the solid surface. The critical angle of 70° could correspond to the angle at which the individual atoms (or molecules) dissociated from the cluster colliding with the solid surface become likely to bounce back rather than entering the solid. If the irradiation angle exceeds the critical angle, most of the atoms (molecules) forming the cluster hitting the solid surface would bounce on the solid surface in the dissociation process. As the irradiation angle increases, an increasing number of atoms (molecules) forming the cluster hitting the solid surface bounce in a direction parallel to the solid surface, increasing the effective interaction distance greatly. Since the critical angle is considered to be determined by the binding state of the cluster, it is expected that the critical angle for a cluster having molecular bonds does not depend on parameters such as the gas type, accelerating voltage, and ionization condition. The characteristics of the monomer ion beam do not include the long-distance interaction effects described above. An embodiment of the present invention and examples will be described. The structure and functions of a solid surface smoothing apparatus 100 for implementing the method of smoothing a solid surface according to the present invention will be described with reference to FIG. 5. GCIB emission means is structured as follows. A source gas 9 is injected into a vacuum cluster generation chamber 11 by a nozzle 10. The gas molecules of the source gas 9 clump together to form a cluster in the cluster generation chamber 11. The size of the cluster depends on the gas pressure and temperature at a nozzle outlet 10a and the particle size distribution based on the shape and size of the nozzle 10. The clusters generated in the cluster generation chamber 11 pass through a skimmer 12 and enters an ionization chamber 13 as a gas cluster beam. In the ionization chamber 13, an ionizer 14 ionizes the neutral clusters by emitting an electron beam, such as thermal electrons. The ionized gas cluster beam (GCIB) is accelerated by accelerating electrodes 15, concentrated by a magnetic-field convergence unit 16, and brought into a sputtering chamber 17. A target 19, which is a solid (such as a silicon substrate) to be exposed to the GCIB, is attached to a rotary disc 41 disposed on a target support 18 provided in the sputtering chamber 17. The GCIB entering the sputtering chamber 17 is narrowed to have a predetermined beam diameter by an aperture 21 and directed onto the surface of the target 19. If the target 19 is an insulator, the GCIB directed to smooth the surface is neutralized by an electron beam. The solid surface smoothing apparatus 100 is also equipped with a tilting mechanism that can change the GCIB irradiation angle (θ in FIG. 3) and the irradiation inclination (φ in FIG. 3), as an irradiation angle-direction setting means. In this embodiment, the tilting mechanism can change the irradiation angle continuously in a range equal to or greater than the critical angle, depending on the shape data of the fine structure on the solid surface. In other words, the tilting mechanism is implemented by a rotation mechanism that allows the angle of the target support 18 to be set or adjusted for desired smoothing in accordance with shape data of the fine structure on the solid surface given beforehand. The irradiation angle θ and the irradiation inclination 4) must be specified independently of each other, in accordance with the shape data (including the intervals and orientation of surface roughness) of the smoothing target face. The solid surface smoothing apparatus 100 can specify the irradiation angle θ, the irradiation inclination φ, and a reference face for determining the irradiation angle θ and the irradiation inclination φ. The solid surface smoothing apparatus 100 includes a first rotation mechanism and a second rotation mechanism, as shown in FIGS. 6A and 6B, for example. The first rotation mechanism is structured as follows. The target support 18 has a projecting shaft 41a, and the rotary disc 41 is mounted on the projecting shaft 41a to rotate on the center of the projecting shaft 41a. The rotary disc 41 has a flat part 41b, on which the target 19 is attached. The rotary disc 41 has a great number of teeth in its rim 41c, and the teeth engage with the teeth of a gear 43. The gear 43 rotates when driven by a motor 42, and the rotation is transferred to the rotary disc 41 to rotate the target 19 attached to the rotary disc 41. The rotation of the rotary disc 41 is reflected in the irradiation inclination φ. The target support 18 is equipped with an angle detection unit (not shown) for detecting an angle of rotation of the rotary disc 41, that is, the irradiation inclination φ, as a digital value. The angle-of-rotation information detected by the angle detection unit is processed by an electric circuit unit 25b, and the currently detected angle (irradiation inclination) φc is displayed in a current angle area 26a of a display unit 26. The second rotation mechanism is structured as follows. A rotation shaft 21 is fixed to the target support 18, and the target support 18 can rotate on the center of the rotation shaft 21. The rotation shaft 21 is rotatably supported by stationary plates 22a and 22b. The rotation shaft 21 is fixed also to the center of a rotation axis of a gear 24b, and the gear 24b engages with a gear 24a. The gear 24a rotates when driven by a motor 23, and the rotation is transferred to the gear 24b and the rotation shaft 21, consequently rotating the target support 18. The rotation of the target support 18 is reflected in the irradiation angle θ. The stationary plate 22a is equipped with an angle detection unit 25a for detecting the angle of rotation of the target support 18, that is, the GCIB irradiation angle θ with reference to the smoothing target face of the target 19 attached to the target support 18, as a digital value, from the angle of rotation of the rotation shaft 21. The angle-of-rotation information detected by the angle detection unit 25a is processed by the electric circuit unit 25b, and the currently detected angle (irradiation angle) 0, is displayed in the current angle area 26a of the display unit 26. The solid surface smoothing apparatus 100 is also equipped with a scanning mechanism for changing the relative position of the target 19 with respect to the GCIB, such as an XY stage. Suppose that the stationary plates 22a and 22b are fixed to and supported by a stationary-plate supporting member 22c. The stationary-plate supporting member 22c and a first actuator 22d are connected via a first rod 22e. The first actuator 22d can push and pull the first rod 22e, and this action can change the position of the target support 18. In the solid surface smoothing apparatus 100 shown in FIG. 6B, for example, the motion of the first actuator 22d can change the position of the target support 18 in up and down directions in the figure. The first actuator 22d is fixed to and supported by a second rod 22g, and the first actuator 22d is connected to second actuators 22f through the second rod 22g. The second actuators 22f can push and pull the second rod 22g, and this action changes the position of the first actuator 22d. Consequently, the position of the target support 18 connected to the first actuator 22d can be changed by the first rod 22e or the like. The direction in which the first rod 22e can move is nearly orthogonal to the direction in which the second rod 22g can move. The scanning mechanism like an XY stage is implemented as described above. In the solid surface smoothing apparatus 100 shown in FIG. 6B, for example, the motion of the second actuators 22f can change the position of the target support 18 in the left and right directions in the figure. Therefore, in combination with the motion of the first actuator 22d, the target support 18 can be moved up and down, and left and right in the figure. The solid surface smoothing apparatus 100 is further equipped with a database 30 that allows a dose to be determined in accordance with conditions such as a desired etching amount, the material and etching rate of the target 19, and the gas type, accelerating energy, irradiation angle θ, and irradiation inclination φ of the GCIB. If the shape data of the fine structure on the target face and the above-mentioned conditions are given beforehand, a dose for desired smoothing can be determined with reference to the database 30. If the irradiation angle is greater than 0°, the beam projection area is large, so that the effective dose is small for the same GCIB current. Instead of associating the effective dose with a combination of the conditions such as the irradiation angle θ and the irradiation inclination φ, the database 30 may associate the combination with a dose calculated from the GCIB current and the projected area in the conditions of vertical irradiation. In the solid surface smoothing apparatus 100 shown in FIG. 6B, a setup unit 27 is used to specify the face of the target support 18 as the reference face and to specify conditions such as the shape data of the fine structure on the target surface, a desired etching amount, the material and etching rate of the target 19, and the gas type, accelerating energy, irradiation angle θp, and irradiation inclination φp of the GCIB. In a reference face display area 26b of the display unit 26, FACE OF TARGET SUPPORT is displayed, and an irradiation angle specified with reference to the normal to this face is displayed in a set angle area 26c. A control unit 28 drives the motor 23 and the motor 42 through a drive unit 29 to match the current irradiation angle θ, and the current irradiation inclination φc to the predetermined irradiation angle θp and the predetermined irradiation inclination φp, respectively. The control unit 28 also determines an appropriate dose on the basis of the above-mentioned conditions with reference to the database 30 and controls the GCIB emission means to perform GCIB irradiation with the determined dose. The control unit 28 includes a CPU (central processing unit) or a microprocessor and controls the operation as described above by executing a program required to control the solid surface smoothing process, such as displaying the data and driving the motors. A solid surface smoothing apparatus according to the present invention is not limited in structure and mechanism to the solid surface smoothing apparatus 100 described above, and modifications can be added within the scope of the present invention. For example, the irradiation angle setting means and others described above can be added to the conventional GCIB trimming equipment. In this structure, when trimming is performed, surface smoothing is also performed (smoothing of long-interval surface roughness can also be skipped), so that the fine structure fabrication precision can be improved. Examples will now be described. In the examples described below, an Ar gas cluster and a SF6 gas cluster were used. When the Ar gas cluster was used, Ar gas was used as a source. An Ar gas cluster beam was generated, the beam having a particle size distribution which had a peak at about 2000 Ar atoms per cluster, and the beam was directed to the target 19 at an accelerating voltage of 30 kV. When the SF6 gas cluster was used, SF6 gas and He gas were used as sources. A SF6 gas cluster ion beam was generated, the beam having a particle size distribution which had a peak at about 500 SF6 molecules per cluster, and the beam was accelerated at an accelerating voltage of 30 kV and directed to the target 19. A pattern structure was fabricated on the target 19, which was a silicon substrate, in the method described below. An electron beam resist was applied on the silicon substrate having a thermally-oxidized film, and a pattern structure was drawn on the resist by an electron beam lithography apparatus. After the resist was developed, the resist pattern was used as a mask, and the thermally-oxidized film was etched by a reactive ion etching (ME) apparatus. The resist was then removed, and silicon was dry-etched by using the thermally-oxidized film as a hard mask. The Ar ion milling method was used as a dry etching method. To fabricate a vertical groove shape as in a line-and-space pattern structure, the Ar-ion irradiation angle was varied appropriately during etching. Then, the thermally-oxidized film was removed by an ashing apparatus. To examine the morphology of a side wall of a line before and after the GCIB irradiation, a flat silicon substrate without line-and-space pattern structure was prepared as an observation sample. An observation sample formed of a Cr film (having a film thickness of 300 nm) on a silicon substrate by sputtering was also prepared as a sample of non-silicon material. The observation samples were placed in such a manner that the surfaces became parallel to the side wall of the line in the line-and-space structure, and were subjected to Ar ion milling and GCIB irradiation. By using the surfaces of the observation samples, the side wall of the line in the line-and-space pattern structure can be evaluated equivalently. The morphologies of side walls of lines in the examples described below were obtained from the measurement of the observation samples. Each dose of GCIB in the examples given below was an input value (a converted dose of irradiation at an irradiation angle of 0° given to the solid surface smoothing apparatus 100. If the irradiation angle is greater than 0°; the beam projection area increases, making the effective dose smaller than the input value given to the apparatus. The smoothing target face in a pattern structure was smoothed in accordance with the procedure illustrated in the flowchart in FIG. 7. The smoothing of the target face viewed from a different point of view is just etching of the target face. In the examples, trimming of the pattern structure and the smoothing of the target face were implemented by etching the target face. The procedure will now be described. Step S1 Prior to the GCIB irradiation, the pattern structure (fine structure) of the target 19 was observed by an atomic force microscope or the like, and the shape data were obtained. Step S2 Based on the differences between the shape data and desired values such as a pattern width and the like, an etching amount required to form a fine structure of a desired size was calculated. Step S3 The target 19 was attached to the target support 18 of the solid surface smoothing apparatus 100, and the angle of the target support 18 was specified as the irradiation angle θ and the irradiation inclination φ. To reduce (smooth) surface roughness having long intervals in the target face, the irradiation angle θ should be greater than 70°, as clarified in the present invention. Other irradiation angles can be selected for purposes other than smoothing. An appropriate irradiation angle can be selected depending on the application. (The solid surface smoothing apparatus 100 can be used for purposes other than smoothing of surface roughness having long intervals.) Step S4 Conditions such as a desired etching amount, the material and etching rate of the target 19, and the gas type, accelerating energy, irradiation angle θ, and irradiation inclination φ of the GCIB were specified. A dose was determined on the basis of the conditions, with reference to the database 30. Step S5 The gas cluster ion beam irradiation was then performed. As a result, the pattern structure on the surface of the target 19 was trimmed, and the target face was smoothed. The following specific processes were performed. A line-and-space pattern structure was fabricated on the surface of a silicon substrate under a design condition of each line width=each space width=1.0-μm and each depth of 1.0-μm. The line width distribution of the line-and-space pattern structure on the surface of the silicon substrate was measured with an atomic force microscope. The half-value width in the distribution was within the permissible range, but the average value was 1.05 μm, 50 nm greater than the designed value. In order to obtain a morphology of a side wall of a line in the line-and-space structure formed by Ar ion milling, the uneven shape of an observation sample surface was observed with the atomic force microscope (AFM). As shown in FIG. 8A, the uneven shape observed in the surface of the observation sample had characteristic stripes extending in a direction perpendicular to the projected irradiation direction (direction of depth of the line-and-space groove) of the AR ion beam, marked with an arrow. The observation by the AFM was made in such a manner that the stripes were diagonal in the AFM frame, so that the intervals of unevenness were able to be measured accurately. The uneven shape having the stripes is considered to be formed because the Ar ion beam was directed to the side of the line at an angle in Ar ion milling. The average surface roughness Ra obtained from the AFM image was 2.90 nm. The uneven shape was examined in further detail in a cross section taken along a white line (FIG. 8A). The uneven shape had relatively long intervals, and the uneven shape having long intervals had another uneven shape having shorter intervals (as shown in an oval frame in FIG. 8B). To analyze the intervals of the uneven shapes in detail, Fourier transform (FFT) of the uneven shapes in the cross section was obtained. The result showed that there were an uneven shape having long intervals with a peak in the vicinity of 1.2 μm and an uneven shape having short intervals of around a hundred nanometers to several tens of nanometers (FIG. 9). The SF6 gas cluster ion beam was directed to the side walls of the lines in the silicon substrate having the above-described uneven shapes at a variety of irradiation angles θ, in order to trim the line widths. The sides of the lines were smoothing target faces here. An irradiation angle of 30° or greater that allows irradiation onto the side of the line was used. As a dose required to bring the average value of the line widths closer to the designed value of 1.00 μm at each irradiation angle θ, data shown in FIG. 10 (at an accelerating energy of 30 keV and with a cluster particle size distribution which has a peak at 500 particles per cluster) stored in the database was used. The irradiation inclination φ was 90°, which was perpendicular to the long-interval unevenness (undulation) of the stripes. The line widths after trimming were measured, and the average value was within the range of 1.00±0.01 μm at any irradiation angle θ. An AFM image of a side of one of the lines at 0=83° (FIG. 11A), the graph of an uneven shape in the cross section taken along a white line (FIG. 11B), and the FFT spectrum (a curve of φ=90° in FIG. 9) were examined. The examination showed that the spectral intensity of unevenness having long intervals close to 1.2 μm and the spectral intensity of unevenness having shorter intervals decreased dramatically after the GCIB irradiation. An arrow in FIG. 11A represents the projected irradiation direction of the SF6 (sulfur hexafluoride) GCIB irradiation. The average surface roughness Ra was 0.21 nm, which was below 10% of the corresponding value before the GCIB irradiation, demonstrating that dramatic smoothing was accomplished. Dependence of the average surface roughness on the irradiation angle was examined. The average surface roughness decreased dramatically at an irradiation angle θ of 70° or greater(FIG. 12). The same experiment as in the first example was conducted, except that the irradiation inclination φ was 0°. An irradiation with an irradiation inclination φ of 0° corresponds to the GCIB irradiation in the direction parallel to the stripes formed in a side of a line by Ar ion milling (see the angle definitions in FIG. 3). FIG. 13A shows an AFM image of the side of the line after the GCIB irradiation at an irradiation angle θ of 83°. An arrow in FIG. 13A indicates the projected irradiation direction of the SF6 (sulfur hexafluoride) GCIB irradiation. The figure shows that the uneven shape of stripes found before the SF6 GCIB irradiation was not eliminated. A detailed observation of the uneven shape in the cross section taken along a white line (FIG. 13A) showed that the short-interval uneven shape laid on the long-interval uneven shape disappeared after the GCIB irradiation and that a smooth curve remained (as shown in an oval frame in FIG. 13B). Further analysis of the FFT spectrum showed that the spectral intensity of a short interval of around several tens of nanometers decreased dramatically and that the spectral intensity of unevenness having long intervals close to 1.2 μm was not reduced (a curve of φ=0° in FIG. 9). In an experiment conducted to check whether the effects observed in the first example could be seen with a combination of another material and a gas cluster, an Ar gas cluster ion beam was directed to an observation sample of a Cr film formed on a silicon substrate. The same Ar ion milling conditions as used in etching of the line-and-space pattern structure on the surface of the silicon substrate in the first example were used, and the same striped structure was observed in the Cr-film observation sample. With the Cr-film observation sample, the relationship between the irradiation angle θ of the Ar gas cluster ion beam and the average surface roughness Ra was examined. The dose of irradiation was determined from the relationship between the dose and the irradiation angle θ required to etch the Cr film by 50 nm (FIG. 14), stored in the database. (at an accelerating energy of 30 keV and with a cluster particle size distribution which has a peak at 2000 particles per cluster). FIG. 15 shows the result of the experiment, representing the relationship between the irradiation angle θ and the average surface roughness Ra. As the irradiation angle θ exceeded 70°, the average surface roughness decreased dramatically. Solid surface smoothing of a silicon wafer, which is the target 19, having an arrangement of many chips of one-dimensional diffraction grating (line-and-space pattern structure) formed on the surface will be described. Smoothing was performed in the procedure illustrated in a flowchart shown in FIG. 16. Step S1a Prior to the GCIB irradiation, pattern structures (fine structures) in all areas (for example, in all chip areas) on the surface of the silicon wafer were observed by an atomic force microscope or the like, and the shape data was obtained. The shape data was mapped in the areas on the surface of the silicon wafer to generate a data map. Step S2a Based on differences in values between the data map and desired values of pattern width and the like, an irradiation angle, irradiation inclination, and etching amount were calculated in each area to provide a fine structure of a desired size. In order to perform surface smoothing across the entire surface of the silicon wafer by scanning control, a scanning program was created to perform modulation control such that the irradiation angle, irradiation inclination, and etching amount obtained by the calculation in each area were provided. Step S3a The silicon wafer was placed on the target support 18 of the solid surface smoothing apparatus 100 and was used as a reference face. Step S4a The GCIB irradiation was performed as programmed in the scanning program specified in step S2a. The chips on the surface of the silicon wafer were trimmed, and the target face of each chip was smoothed. The following specific processes were performed. A great number of chips of one-dimensional diffraction grating (line-and-space pattern structure) was arranged on the surface of a silicon wafer (FIG. 17A). The structure was designed with both the line width and the space width set to 0.29 μm and the groove width set to 700 nm. A single chip was a 25 μm square. The line width distribution on the surface of the silicon wafer was examined. The line width was 0.32 μm in the center of the silicon wafer and was 0.35 μm at the edge of the silicon wafer (FIG. 17B). The line width distribution increased monotonically from the center to the edge of the silicon wafer. In order to obtain the morphology of the sides of lines in the line-and-space pattern structure at different positions on the surface of the silicon wafer, observation samples were placed beforehand in the locations on the target support 18 corresponding to the positions on the surface of the silicon wafer, and Ar ion milling was performed under the same conditions. The observation samples were observed by an atomic force microscope, and it was observed that each sample has a striped structure having intervals of about 1 μm. The extending directions and intervals of the stripes varied continuously from the center toward the edge of the silicon wafer. In the center of the silicon wafer, the stripes were perpendicular to the direction of depth of the grooves (ω=0°, that is, parallel to the x-axis in FIG. 17A), and the intervals of stripes were about 800 nm. In observation samples in an outermost circumference, the stripes extended in a direction displaced by 5° from the x-axis (direction of ω=5° in FIG. 17A), and the stripes had intervals of 1.1 μm. This is considered to result from uneven Ar ion beam irradiation across the entire surface of the silicon wafer in Ar ion milling. Based on the shape data, a program was created to bring the irradiation angle θ and the irradiation inclination φ of the SF6 gas cluster beam to θ=80° and φ=90° in the center of the silicon wafer and to θ=83° and φ=85° at the edge and to vary the angle and inclination of the GCIB irradiation continuously, in conjunction with scanning of the target silicon wafer. To bring the line widths to the designed value across the whole surface of the silicon wafer, the line widths needed to be reduced by 30 nm in the center of the silicon wafer and by 60 nm at the edge. Therefore, a required dose of SF6 gas cluster ion beam irradiation was set to 4.71014 ions/cm2 in the center and to 9.41014 ions/cm2 at the edge, and a program was written to change the irradiation dose continuously in association with the contour data of the line width distribution. The symbol “*” indicates multiplication. After the GCIB irradiation, the shapes of the diffraction grating chips across the entire surface of the silicon wafer were observed by an atomic force microscope. The chips across the surface of the silicon wafer, except ones in the outermost edge of the silicon wafer, had almost the same line width of 0.29 μm, which was almost equal to the designed value (FIG. 17C). The average surface roughness of the sides of the lines before and after the SF6 gas cluster ion beam irradiation was equivalently evaluated by observing an observation sample with an atomic force microscope (AFM). The average surface roughness Ra of the sides of the lines before the SF6 gas cluster ion beam irradiation varied in a range of 1.9 nm to 3.1 nm, depending on the position on the silicon wafer surface. The average surface roughness Ra of the sides of the lines after the SF6 gas cluster ion beam irradiation was within a range of 0.32 nm to 0.38 nm at any position on the silicon wafer surface. This demonstrates that the surface roughness was reduced. The examples described above show the following facts. The first example indicates that the average surface roughness of the smoothing target face decreases dramatically when the GCIB irradiation angle θ is 70° or greater relative to the normal to the target face. With the second example also taken into account, it is indicated that the dramatic decrease in the average surface roughness is caused by the reduction of unevenness (undulation) having long intervals of about 1 μm and that the long-interval unevenness reduction effect (long-distance interaction effect) is very large at an irradiation angle of 70° or greater. It is also indicated that the effects of reduction of unevenness of up to about 100 nm do not depend on the irradiation inclination, whereas the undulation having long intervals of about 1 μm can be effectively reduced when the direction of undulation matches the irradiation inclination. The third example indicates that the long-distance interaction effect does not depend on the combination of the solid material and the gas cluster and that the long-distance interaction effect can be obtained at an irradiation angle of 70° or greater. In the examples described above, the accelerating voltage was 30 kV. As the accelerating voltage increases, the etching amount increases, reducing the smoothing time. However, this can increase the surface roughness. Therefore, the accelerating voltage should be determined in accordance with the requirements of smoothing such as time and material. The apparatus conditions, such as the gas type, irradiation conditions, and cluster size, and parameters are not limited and can be changed appropriately. According to the present invention, the fabrication precision of fine structures such as semiconductor devices can be improved by reducing surface roughness having long intervals (of several tens of nanometers to about 100 micrometers). In addition to the fabrication precision of fine structures such as semiconductor devices and optical devices, the fabrication precision of three-dimensional structures such as dies used to create semiconductor devices and optical devices can be improved. According to the present invention, by setting the angle of gas cluster ion beam irradiation to the critical angle or greater, the effective interaction distance increases dramatically, in comparison with an irradiation angle smaller than the critical angle. The wide range of interaction between the cluster and the solid brings about solid surface smoothing. Therefore, solid surface roughness having intervals of several tens of nanometers to about a hundred micrometers can be reduced by gas cluster ion beam irradiation.
	claims	1. A charged particle beam application apparatus comprising,a stage for moving a specimen, anda specimen holding device arranged on the stage,wherein the specimen holding device including an electrostatic chuck capable of holding thereon at least a first specimen of first specimen size and a second specimen of second specimen size greater than the first specimen size, and a top table including an opening in which the electrostatic chuck is arranged,the top table has an outer peripheral portion including a side wall extending to surround an outer periphery of the second specimen held by the electrostatic chuck, and a reference planar portion arranged at an upper end of the side wall, andthe electrostatic chuck is capable of holding thereon a dummy specimen together with the first specimen. 2. The charged particle beam application apparatus according to claim 1, wherein the electrostatic chuck is capable of holding thereon the dummy specimen between an outer periphery of the first specimen and the side wall. 3. The charged particle beam application apparatus according to claim 1, wherein a size of the electrostatic chuck is greater than the first specimen size and smaller than the second specimen size. 4. The charged particle beam application apparatus according to claim 1, wherein the reference planar portion and a surface of the second specimen form a substantially common height. 5. A charged particle beam application apparatus comprising,a stage for moving a specimen, anda specimen holding device arranged on the stage,wherein the specimen holding device including an electrostatic chuck capable of holding thereon at least a first specimen of first specimen size and a second specimen of second specimen size greater than the first specimen size, and a top table including an opening in which the electrostatic chuck is arranged,the top table has an outer peripheral portion including a side wall extending to surround an outer periphery of the second specimen held by the electrostatic chuck, and a reference planar portion arranged at an upper end of the side wall,the electrostatic chuck is capable of holding thereon both of the first specimen and a dummy specimen arranged between an outer periphery of the first specimen and the side wall,an inner diameter of the dummy specimen is greater than an outer diameter of the first specimen size, and an outer diameter of the dummy specimen is greater than an outer diameter of the electrostatic chuck and smaller than an outer diameter of the opening. 6. The charged particle beam application apparatus according to claim 5, wherein a thickness of the dummy specimen is substantially equal to a thickness of one of the first and second specimen. 7. The charged particle beam application apparatus according to claim 5, wherein a material of the dummy specimen is equal to that of one of the first and second specimen. 8. The charged particle beam application apparatus according to claim 5, wherein the dummy specimen is electrically earthed to be prevented from being electrically charged. 9. The charged particle beam application apparatus according to claim 5, wherein the dummy specimen has a predetermined pattern. 10. A charged particle beam application apparatus comprising,a stage for moving a specimen,a specimen holding device arranged on the stage, anda specimen chamber arranged to surround the stage,wherein the specimen holding device including an electrostatic chuck capable of holding thereon at least a first specimen of first specimen size and a second specimen of second specimen size greater than the first specimen size, and a top table including an opening in which the electrostatic chuck is arranged, andthe electrostatic chuck is capable of holding thereon a dummy specimen together with the first specimen. 11. The charged particle beam application apparatus according to claim 10, further comprising a transfer mechanism for transferring onto and from the stage the dummy specimen and one of the first and second specimens independently of each other. 12. The charged particle beam application apparatus according to claim 10, wherein the electrostatic chuck has one of a groove and non-attractive region which one communicates with a gap between an outer periphery of the first specimen and the dummy specimen. 13. The charged particle beam application apparatus according to claim 10, further comprising a positioning device for positioning on the stage the dummy specimen and one of the first and second specimens. 14. The charged particle beam application apparatus according to claim 10, further comprising a stocker arranged adjacently to the specimen chamber to contain therein at least one of the dummy specimen, and a transfer device for selecting the dummy specimen in accordance with a size and material of the specimen to be treated.
	summary
	claims	1. An illumination system configured to condition a radiation beam, comprisinga mirror configured for grazing or normal incidence reflection comprising a stack of a plurality of alternating layers including a layer made of metal non-metal compound adjacent a reflection surface of the mirror with a non-metal layer between a substantially pure metal layer and the layer made of metal non-metal compound anda hydrogen radical source configured to supply gas containing hydrogen or hydrogen radicals to the reflection surface,wherein the layer made of metal non-metal compound to protect the substantially pure metal layer from the hydrogen or hydrogen radicals. 2. An illumination system according to claim 1, wherein the metal non-metal compound consists of a transition metal carbide, nitride, boride or silicide compound or mixture thereof. 3. An illumination system according to claim 1, wherein the metal non-metal compound is a metal silicon compound. 4. An illumination system according to claim 3, wherein the metal and silicon are present in the metal non-metal compound in a stoichiometric ratio. 5. An illumination system according to claim 1, wherein the metal in the metal non-metal compound is selected from the group of Mo and Ru. 6. An illumination system according to claim 5, wherein the metal non-metal compound is selected from the group consisting of Mo and Si in a ratio of two-to-one and Ru and Si in a ratio of two-to-three. 7. An illumination system according to claim 1, wherein the radiation beam is an EUV beam. 8. An illumination system according to claim 1, wherein the layer made of the metal non-metal compound being provided between said stack and the reflection surface. 9. An illumination system according to claim 8, wherein the stack comprises a plurality of substantially pure metal layers, alternating with non-metal layers. 10. An illumination system according to claim 8, wherein the stack of layers comprises only one layer of the metal compound. 11. An illumination system according to claim 1, wherein the layer made of the metal non-metal compound has a thickness sufficient to provide substantially all reflectivity of the mirror at an incidence angle at which the radiation beam is incident on the reflection surface. 12. An illumination system according to claim 1, wherein the layer made of the metal non-metal compound is provided between the reflection surface and a layer made of metal only and having a thickness sufficient to provide all substantially reflectivity of the mirror at an incidence angle at which the radiation beam is incident on the reflection surface. 13. A photolithographic apparatus comprisingan illumination system configured to condition a radiation beam and a hydrogen radical source configured to supply gas containing hydrogen or hydrogen radicals into the illumination system, the illumination system comprisinga mirror comprising one or more layers made of metal non-metal compound adjacent a reflection surface of the mirror with a non-metal layer between a substantially pure metal layer and the layer of metal non-metal compound, wherein the mirror includes one or more substantially pure metal layers such that a ratio between a number of the layers made of metal non-metal compound and a number of the metal layers is less than about 50%. 14. A photolithographic apparatus according to claim 13, wherein the metal non-metal compound consists of a transition metal carbide, nitride, boride or silicide compound or mixture thereof. 15. A photolithographic apparatus according to claim 13, wherein the metal non-metal compound is a metal silicon compound. 16. A photolithographic apparatus according to claim 15, wherein the metal and silicon are present in the metal non-metal compound in a stoichiometric ratio. 17. A photolithographic apparatus according to claim 13, wherein the metal in the metal non-metal compound is selected from the group of Mo and Ru. 18. A photolithographic apparatus according to claim 17, wherein the metal non-metal compound is selected from the group consisting of Mo and Si in a ratio of two to one and Ru and Si in a ratio of two to three. 19. A photolithographic apparatus according to claim 13, wherein the mirror comprises a stack of a plurality of alternating layers adjacent the reflection surface of the mirror, the one or more layers made of the metal non-metal compound being provided between said stack and the reflection surface. 20. A photolithographic apparatus according to claim 19, wherein the stack comprises a plurality of substantially pure metal layers, alternating with non-metal layers. 21. A photolithographic apparatus according to claim 19, wherein the stack of layers comprises only one layer of the metal compound. 22. A photolithographic apparatus according to claim 13, wherein a layer made of the metal non-metal compound of the one or more layers made of the metal non-metal compound has a thickness sufficient to provide substantially all reflectivity of the mirror at an incidence angle at which the radiation beam is incident on the reflection surface. 23. A photolithographic apparatus according to claim 13, wherein a layer made of the metal non-metal compound of the one or more layers made of the metal non-metal compound is provided between the reflection surface and a layer made of metal only and having a thickness sufficient to provide substantially all reflectivity of the mirror at an incidence angle at which the radiation beam is incident on the reflection surface. 24. A photolithographic apparatus according to claim 13, comprising a radiation source configured to emit radiation to the mirror. 25. A method of removing contamination from a mirror with a reflecting metal containing layer, the method comprisingsupplying hydrogen radicals to a reflection surface of the mirror andprotecting the mirror against damage due to the supply of the hydrogen radicals by using one or more layers made of a metal non-metal compound in the mirror adjacent the reflection surface,wherein the mirror includes one or more substantially pure metal layers with a non-metal layer between a substantially pure metal layer and the layer of metal non-metal compound, such that a ratio between a number of the layers made of metal non-metal compound and a number of the metal layers is less than about 50%. 26. A device manufacturing method comprisingprojecting a patterned beam of radiation onto a substrate, wherein the radiation that goes into the beam is reflected by a mirror, the method comprising a step ofremoving contamination from a mirror using a supply of a gas containing hydrogen radicals to a reflection surface of the mirror,wherein the mirror comprises one or more layers made of a metal non-metal compound adjacent the reflection surface,wherein the mirror includes one ore more substantially pure metal layers with a non-metal layer between a substantially pure metal layer and the layer of metal non-metal compound, such that a ratio between a number of the layers made of metal non-metal compound and a number of the metal layers is less than about 50%.
	summary
040574660	description	DESCRIPTION Although not limited thereto, the invention is described herein as employed in a nuclear reactor of the boiling water type. A typical power plant employing a direct cycle boiling water reactor is schematically illustrated in FIG. 1. A pressure vessel 100 contains a nuclear fuel core 101 and steam separating and drying apparatus 102. (The pressure vessel is normally housed in a thick-walled containment building, not shown). A plurality of control rods 103 may be reciprocated by drive devices 104 into and out of the core 101 to control the reactivity thereof. A rod selection and control system 105 controls the operation of the control rod drive devices 104. The vessel 100 is filled with a coolant (for example, light water) to a level somewhat above the core 101. The coolant is circulated through the core 101 by a circulation pump 106 which receives coolant from a downcomer annulus 107 and forces it into a plenum 108 from which the coolant flows upward through the fuel assemblies of the reactor core. The heat produced by the fuel elements is thereby transferred to the water and a head of steam is produced in the upper portion of the vessel. The steam is applied to a turbine 109, the turbine driving an electrical generator 110. The turbine exhausts to a condenser 111 and the resulting condensate is returned as feedwater to the vessel 100 by a feedwater pump 112. A variable speed motor or other drive means 113 is provided to drive the circulation pump 106. This provides a means, in addition to the control rods 103, for varying the reactivity of the core 101 over a limited range. More specifically, a reduction in the coolant flow rate causes an increase in the voids and a decrease in the density of the moderator-coolant with a consequent decrease in moderation of neutrons and hence a decrease in the reactivity of the core. Conversely, an increase in the coolant flow rate increases the moderator density and hence the reactivity of the core. In nuclear reactors of the type under discussion the fuel elements are conveniently formed in the shape of elongated rods formed of a corrosion-resistant, non-reactive material and containing suitable fuel. The fuel elements are grouped together at fixed distances from each other in a coolant flow channel as a fuel assembly or bundle. A sufficient number of the fuel assemblies are arranged in a spaced array to form a nuclear reactor core capable of self-sustained fission reaction. A typical fuel assembly is formed, for example, by a 7 .times. 7 array of spaced fuel rods, the fuel rods being several feet in length, on the order of one-half inch in diameter, and spaced from each other by a fraction of an inch. The fuel rods are contained in an open ended tubular flow channel between suitable tie plates. A typical fuel assembly of this type is illustrated, for example, by B. A. Smith et al in U.S. Pat. No. 3,689,358. A typical fuel element or rod 115 is illustrated in FIG. 2. It includes an elongated cladding tube 116 containing a column of fuel pellets 117 and a space or plenum 118 for the collection of fission product gases. The cladding tube 116 is sealed by an upper end plug 119 and a lower end plug 121 and the column of pellets is retained in position by a spring 122 extending through the plenum 118 from the top of the column of fuel pellets 117 to the upper end plug 119. The cladding tube 116 and the end plugs 119 and 121 are formed of a material suitable for use in a reactor such as an alloy of zirconium. The pellets 117 are preferably formed of an oxide of suitable fuel, such as uranium or plutonium, and the diameter of the pellets 117 is somewhat less than the inside diameter of the cladding tube 116 to provide an initial circumferential clearance or gap 123. For the type of reactor under discussion the fuel pellets 117 are typically 0.5 - 0.8 inches long and about 0.49 inches in diameter. The cladding tube 116 is typically about 0.564 inches in outside diameter with a wall thickness of about 0.032 inches. This provides an initial radial gap 123 of about 0.005 inches (diametral gap of about 0.010). Shown in FIG. 3 is a portion of the fuel element 115, partly cut away to illustrate pellet-cladding interaction. As the fuel pellets 117 produce an increasing amount of power (heat) the fuel pellets expand in such a way as to assume an "hour-glass" or spool shape with expanded and bowed ends 126 and 127 as shown in FIG. 3. Eventually the initial clearance 123 is taken up and the pellet edges 128 and 129 contact the inside surface of the cladding tube 116 and pellet-cladding interaction takes place. Further fuel pellet expansion causes circumferential stress in the cladding tube 116 at the points of pellet-cladding interaction. Also, the pellet ends 128 and 129 tend to lock against the cladding tube. Thus further bowing of the ends 126 and 127 causes a longitudinal moving apart of the pellets ends 128 and 129 with resultant longitudinal stress of the cladding tube. In addition, the pellets 117 develop longitudinal cracks 131. The sharp edges of these cracks may produce points of high local stress in the cladding. For the type of fuel elements under discussion the maximum operating peak power (or linear heat generation rate) is in the order of 16 - 18 kw/ft (kilowatts per foot) and it is found that pellet-cladding interaction occurs in the power range of 6 - 10 kw/ft and above. It has been found that if rapid large changes in power level are made in this pellet-cladding interaction range, the result is a rapid localized strain and stress increase in the cladding, beyond its yield strength, and the cladding may fail by developing cracks such as a characteristic crack 132. The likelihood of pellet-cladding interaction failure is increased with fuel life in a reactor because of the reduction of ductility of the cladding with irradiation. In accordance with the present invention a method has been discovered for conditioning the fuel so that subsequent rapid changes in power level within the conditioned envelope (that is, up to the maximum power level at which the fuel has been conditioned) can be made with minimized danger of cladding damage (that is, pellet-cladding interaction failure). The fuel conditioning method of the invention is illustrated in FIG. 4. It consists of initially increasing the fuel power over the pellet-cladding interaction range to the desired maximum power level at a rate below a critical rate which would cause cladding damage. The maximum rate of this initial power increase has been found to be about 0.1 kw/ft/hr (kilowatts per foot per hour) peak power for the type of fuel elements under discussion. To the extent now understood it is believed that the resistance of irradiated cladding to cracking when stretched is very dependent on the rate at which it is stretched. Thus, the described initial relative slow increase to power allows the cladding to plastically deform in response to the stresses created by the expanding fuel pellets. It is also believed that the cladding stress is relieved by slow plastic deformation or creep of the fuel pellets under the back forces developed by the stressed cladding. This is particularly the case at higher power levels where the oxide fuel pellets become more plastic. In any case it is found that fuel that is brought to power at the discovered conditioning rate does not fail and, furthermore, that subsequent rapid changes in power level of the fuel (for example, 15 percent of rated power per minute) can be made (for example, as is necessary for load following) as illustrated in FIG. 4 with minimum danger of fuel pellet-cladding interaction failure. While a continuous rate of initial power increase is illustrated in FIG. 4, in practice it is found more convenient to increase power in a series of steps. It is found that the fuel conditioning method of the invention can be performed in a step fashion if the individual steps or power ramps are sufficiently small. For example, power steps of about 0.1 kw/ft, peak power, have been found practical while steps of 0.5 kw/ft, peak power, appear to be about the maximum allowable. While the fuel conditioning method herein described allows subsequent rapid power changes, it is further found that this conditioning can be lost if the fuel is subsequently operated at power levels below or near the lower boundary of pellet-cladding interaction for an extended period of time. This loss of conditioning by operation of the fuel at low power levels is thought to result from fuel relaxation, healing of the fuel pellet cracks and relaxation and creep down of the cladding. Thus, after an extended period of operation of the fuel at low power it is found necessary to again condition the fuel for operation at high power levels if fuel pellet-cladding interaction failure is to be avoided. The time and conditions for loss of conditioning have not been completely determined and appear to depend upon a number of factors including prior high power operation history. In any event, as shown hereinafter, conditioning according to the invention has been found to be effective for a sufficient period to allow practical operation through day-to-day and week end load following. The invention is further illustrated by the following examples: EXAMPLE 1 A fuel rod was tested that had been operated in a reactor to an exposure in the order of about 9000-12000 megawatt days per ton. During the last several months of this exposure the peak power in this fuel rod was less than 10 kw/ft. This fuel rod was placed in a test reactor and the power therein was raised rapidly from 10 kw/ft to 14 kw/ft. This fuel rod failed by pellet-cladding interaction. EXAMPLE 2 Five fuel rods having operating histories similar to the fuel rod of Example 1 were tested, as shown in FIG. 5, by increasing the power therein from 10 kw/ft in a series of steps of 2 kw/ft with hold periods of 10 hours between steps. All of these fuel rods failed before reaching 16 kw/ft. EXAMPLE 3 One fuel rod with an operating history similar to the fuel rod of Example 1 was tested, as shown in FIG. 6, by increasing the power therein from 10 kw/ft in a series of steps of 1 kw/ft with hold periods of 5 hours between steps. This fuel rod failed before reaching 16 kw/ft. EXAMPLE 4 Two fuel rods having operating histories similar to that of the fuel rod of Example 1 were tested, as shown in FIG. 7, by increasing the power therein from about 6 kw/ft in a series of steps of 0.125 kw/ft with hold periods of 1 hour between such steps. These fuel rods failed. EXAMPLE 5 Five fuel rods with exposure histories similar to that of the fuel rod of Example 1 were tested, as shown in FIG. 8 as follows: In a fuel rod F-1 power was increased therein at a rate of about 16 kw/ft/hr to a power level of about 8 kw/ft. The power therein was then further increased in a series of steps of 0.08 kw/ft with hold periods of 1 hour between steps to a power level of 15.5 kw/ft. In fuel rods F-2, F-3 and F-4 power was increased therein at a rate of about 16 kw/ft/hr to a power level of about 7 kw/ft. The power therein was then increased in a series of steps of 0.08 kw/ft with hold periods of 1 hour between steps to a power level of 16.2 kw/ft for rod F-2, 15.5 kw/ft for rod F-3 and 13.5 kw/ft for rod F-4. In a fuel rod F-5 power was increased to about 6 kw/ft at about the 16 kw/ft/hr rate. The power therein was then increased at the 0.08 kw/ft/hour rate in 1 hour steps to a power level of 11.5 kw/ft. After the foregoing tests these five fuel rods F-1 to F-5 were thoroughly examined. None of these fuel rods had failed nor did they show any evidence of incipient failures. EXAMPLE 6 A fuel rod with an exposure history similar to that of the fuel rod of Example 1 was tested over the power range from about 7 kw/ft to about 16 kw/ft by increasing the power in a series of steps 0.09 kw/ft with hold periods of 1 hour between steps. Upon subsequent examination this rod showed no evidence of failure. EXAMPLE 7 A fuel rod with an exposure history similar to that of the fuel rod of Example 1 was, as shown in FIG. 9, was increased in power from about 7 kw/ft to about 16 kw/ft in a series of steps of about 0.1 kw/ft with hold periods of 1 hour between steps. The power in this fuel rod was cyclically decreased and increased at relatively rapid rates and with hold periods substantially as shown in FIG. 9. Subsequent examination of this fuel rod revealed no evidence of failure. Thus this test demonstrated the ability of the method of the invention to condition the fuel for subsequent large and rapid power changes, as might be required for load following. EXAMPLE 8 Several fuel rods with exposure histories similar to that of the fuel rod of Example 1 were tested, as illustrated in FIG. 10, by first conditioning the rods according to the method of the invention and thereafter cyclically decreasing and increasing the power therein at relatively rapid rates with various hold times at the lower power levels including hold times of up to 480 hours. None of these rods failed. This test demonstrated that the fuel conditioning persists through at least 480 hours of low power operation, a period more than sufficient to accommodate, for example, load following through a long holiday week end or the like. In addition to the foregoing examples, the utility and success of the present invention has been confirmed by use of the method of the invention in several commercial power reactors since May 1973. Information from these reactors indicates that use of the conditioning method of invention has allowed subsequent large and rapid changes in power level with significant reduction of fuel rod failures. While the fuel rod power (linear heat generation rate) of the fuel rods has been expressed herein in terms of kilowatts per foot, other equivalent terms can be used. For example, the fuel rod power alternatively can be expressed in terms of percent of rated power. For example if a fuel rod has a maximum power rating of 16 kw/ft, a rate of power change of 0.6 percent of rated power per hour corresponds to 0.096 kw/ft/hr. While the method of the invention has been described herein as applied to fuel rods with a fuel pellet diameter in the order of 0.49 inches, the invention is equally applicable to fuel rods of other diameter. Since at a given linear heat generation rate and fuel stress state the fuel creep rate is substantially inversely proportional to the square of the fuel pellet diameter, the conditioning rate (in terms of the rate of increase of the linear heat generation rate) is also inversely proportional to the square of the fuel pellet diameter. Also, the conditioning rate is directly proportional to the stress level of the cladding, hence to the cladding tube thickness to diameter ratio. Therefore, the conditioning rate can be simply generalized as follows: ##EQU1## where C.sub.r is the conditioning rate for the fuel rod in question; C.sub.1 is the known conditioning rate for a known fuel rod containing fuel pellets of known diameter D.sub.1 PA1 D.sub.1 is the diameter of the fuel pellets and cladding of the known fuel rod; PA1 D.sub.n is the diameter of the fuel pellets and cladding of the fuel rod in question; PA1 T.sub.1 is the cladding thickness of the known fuel rod; and PA1 T.sub.n is the cladding thickness of the fuel rod in question. PA1 T.sub.n and containing fuel pellets of diameter D.sub.n is: ##EQU2## As shown hereinbefore, for a fuel rod having a cladding thickness of about 0.032 inches and containing fuel pellets of about 0.49 inches in diameter, the maximum conditioning rate is about 0.1 kw/ft/hr and the critical rate (which is likely to cause cladding failure) is about 0.125 kw/ft/hr. Therefore, the maximum or permissible conditioning rate C.sub.rm for a fuel rod of cladding thickness Thus, for example, if the pellet diameter is halved and the cladding thickness is the same, the permissible conditioning rate is increased 8-fold. If the cladding thickness is also halved, the permissible conditioning rate is only increased 4-fold. It is noted that the onset of pellet-cladding interaction (which, as mentioned hereinbefore, occurs in the power range of about 6 - 10 kw/ft for fuel of about 0.49 inches in diameter with 0.032 inch cladding) is substantially independent of the fuel pellet diameter and cladding thickness.
	abstract	In one aspect, the present application is directed to a radiant energy emitting device. The radiant energy emitting device comprises (A) an outer housing including at least one aperture there through, the housing being operationally configured to (1) receive and contain radiant energy therein, and (2) emit radiant energy out through the aperture to a target surface; (B) an energy emission means; and (C) a sensor means disposed about the aperture of the housing, the sensor means being in communication with the energy emission means and operationally configured to detect the spatial relationship between the sensor means and the target surface, said spatial relationship determining activation of the energy emission means.
	claims	1. A passive reactor cooling system usable after a loss-of-coolant accident, the system comprising:a containment vessel in direct thermal contact with an external heat sink;a reactor well disposed inside the containment vessel;a reactor vessel disposed at least partially, in the reactor well, the reactor vessel containing primary coolant and a nuclear fuel core beating the primary coolant which is circulated between the reactor vessel and a steam generator in a closed primary coolant flow loop;a cooling water tank disposed inside the containment vessel and containing an inventory of emergency cooling water in selective fluid communication with the reactor well via at least one flow control apparatus, the flow control apparatus having a closed position preventing flow of cooling water to the reactor well and an open position providing flow of cooling water to the reactor well; anda heat exchanger comprising a plurality of longitudinally-extending heat dissipater ducts integrally attached directly to an inside surface of the containment vessel in a thermally conductive relationship, the heat exchanger in fluid communication with the reactor well and water tank via a closed cooling water flow loop in which flow is driven via gravity;wherein following a loss of primary coolant, the water tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core and flows through the closed cooling water flow loop to the heat exchanger;the steam flowing through the heat dissipater ducts of the heat exchanger and transferring heat to the external heat sink directly through the containment vessel which condenses the steam. 2. The system according to claim 1, wherein the steam condenses in the heat exchanger forming condensate, and the condensate flows via gravity back to the water tank via the closed cooling water flow loop. 3. The system according to claim 2, wherein the condensate flows from the water tank back to the reactor well via the flow control apparatus. 4. The system according to claim 1, wherein the flow control apparatus comprises at least one flow conduit and a dump valve movable between the open and closed positions, the dump valve controlling the flow of cooling water to the reactor well from the cooling water tank through the at least one flow conduit. 5. The system according to claim 2, wherein a top of the reactor well is sealed and enclosed by a closure structure, the closure structure capturing the steam produced in the reactor well which is directed to the heat exchanger via the closed cooling water flow loop by steam inlet piping penetrating the closure structure. 6. The system according to claim 5, wherein the closure structure is formed at least in part by a ring-shaped reactor support, flange attached to and extending circumferentially around a perimeter of the reactor vessel. 7. The system according to claim 5, wherein a top of the cooling water tank is sealed and enclosed, the condensate flowing back to the water tank from the heat exchanger via the closed cooling water flow loop through outlet condensate piping penetrating the enclosed closed top of the cooling water tank. 8. The system according to claim 1, wherein the cooling water tank has a volumetric capacity at least as large as the volumetric capacity of the reactor well to optimize cooling the reactor core during a loss of primary coolant event. 9. The system according to claim 1, wherein the containment vessel comprises a cylindrical metal shell in thermal communication with the external heat sink. 10. The system according to claim 9, wherein the heat dissipater ducts are parallel to each other and circumferentially spaced apart around a circumference of the inner surface of the containment vessel. 11. The system according to claim 1, wherein the heat dissipater ducts are vertically oriented, each heat dissipater duct having upper and lower ends fluidly coupled to a common upper inlet ring header and a common lower outlet ring header attached to the inner surface of the containment vessel. 12. The system according to claim 1, wherein each heat dissipater duct is formed of a half-section of pipe or tube defining parallel longitudinal legs which are seam welded to the interior surface of the containment vessel such that the steam and condensate flowing in each heat dissipater duct is in immediate contact with the interior surface of the containment vessel. 13. The system according to claim 1, wherein the external heat sink comprises an annular reservoir holding water that surrounds and contacts an exterior surface of the containment vessel. 14. The system according to claim 13, wherein the water in the annular reservoir has a temperature lower than the temperature of the steam for condensing the steam. 15. The system according to claim 13, wherein the annular reservoir is formed between the containment vessel and an outer containment enclosure structure. 16. The system according to claim 2, wherein the closed flow loop includes:inlet steam piping fluidly coupling the heat exchanger to an enclosed top portion of the reactor well which prevents escape of the steam to an environment inside the containment vessel; andoutlet condensate piping fluidly coupling the heat exchanger to an enclosed top portion of the cooling water tank;wherein the enclosed reactor well and cooling water tank form an integral part of the closed cooling water flow loop. 17. The system according to claim 1, wherein the reactor well and cooling water tank are formed in a concrete monolith disposed in the containment vessel, the reactor well and cooling water tank sharing a common wall therebetween. 18. A passive reactor cooling system usable after a loss-of-coolant accident, the system comprising:a metal containment vessel comprising a shell in direct thermal contact with an external annular water-filled reservoir which defines an external heat sink;a monolithic concrete structure disposed inside the containment vessel and defining a reactor well;a vertically elongated reactor vessel having a lower portion disposed in the reactor well and an upper portion, the reactor vessel containing primary coolant and a nuclear fuel core heating the primary coolant which is circulated between the reactor vessel and a steam generator in a closed primary coolant flow loop;a cooling water tank disposed inside the containment vessel and containing an inventory of emergency cooling water in selective fluid communication with the reactor well via at least one flow conduit controlled by a dump valve, the dump valve having a closed position preventing flow of cooling water to the reactor well and an open position providing flow of cooling water to the reactor well; anda heat exchanger comprising a plurality of longitudinal heat dissipater ducts integrally attached directly to an inside surface of the containment vessel shell in a thermally conductive relationship, the heat exchanger in fluid communication with the reactor well and cooling water tank via a closed cooling water flow loop in which flow is driven via gravity;wherein following a loss of primary coolant, the cooling water tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core and flows through the closed cooling, water flow loop to the heat dissipater ducts; andwherein the steam condenses in the heat dissipater ducts via rejection of heat to the external heat sink directly through the containment vessel shell forming condensate which flows via gravity back to the cooling water tank via the closed cooling water flow loop. 19. The system according to claim 18, wherein the cooling water tank is formed in the monolithic concrete structure adjacent the reactor well, the reactor well and cooling water tank sharing a common wall therebetween and the at least flow conduit formed through the common wall. 20. A passive reactor cooling system usable after a loss-of-coolant accident, the system comprising:a containment vessel in thermal communication with an external heat sink;a reactor well disposed inside the containment vessel;a reactor vessel disposed at least partially in the reactor well, the reactor vessel containing primary coolant and a nuclear fuel core heating the primary coolant which is circulated between the reactor vessel and a steam generator in a closed primary coolant flow loop;a cooling water tank disposed inside the containment vessel and containing an inventory of emergency cooling water in selective fluid communication with the reactor well via at least one flow control apparatus, the flow control apparatus having a closed position preventing flow of cooling water to the reactor well and an open position providing flow of cooling, water to the reactor well; anda heat exchanger attached to an inside surface of the containment vessel, the heat exchanger in fluid communication with the reactor well and water tank via a closed cooling water flow loop in which flow is driven via gravity;wherein following a loss of primary coolant, the water tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core and flows through the closed cooling water flow loop to the heat exchanger;wherein the heat exchanger comprises a plurality of longitudinally-extending heat dissipater ducts integrally attached to the containment vessel and in thermal communication with the external heat sink via the containment vessel;wherein each heat dissipater duct is formed of a half-section of pipe or tube defining parallel longitudinal legs which are seam welded to the interior surface of the containment vessel such that the steam and condensate flowing in each heat dissipater duct is in immediate contact with the interior surface of the containment vessel.
	description	The present invention relates to the production of fuel rods for light water reactor nuclear fuel assemblies. More specifically, the present invention provides a segment make-up system and method that is used to incorporate nuclear fuel pellets into nuclear fuel rod clad during the production of nuclear fuel rods for nuclear fuel assemblies. Production of nuclear fuel is often costly and complicated due to the amount of precautionary steps that are required to be undertaken during production of the fuel. In order to produce a safe nuclear fuel, nuclear fuel rods are designed with several different components, each of the components having a specific technical purpose. The innermost component is generally a uranium enriched ceramic material that is shaped in the form of a pellet. Individual pellets are placed end to end in a column. The pellets are then placed inside an elongated rod made of corrosion resistant metal called a fuel clad. The nuclear fuel pellets are loaded into the fuel clad generally according to several technologies. The uranium enriched ceramic material is protected from mechanical and chemical wear by the fuel clad during operation of the reactor. When originally fabricated, the nuclear fuel clad is open (unsealed) at the two ends of the rod. A first lower end piece can be welded onto the clad. The clad is then filled with the nuclear fuel pellets. Lastly, an upper end piece is welded to the remaining open end of the fuel clad thereby forming a completed fuel rod. As a precaution, springs and/or other devices are also included inside the volume encapsulated by the fuel clad to allow the uranium fuel pellets to swell and shift within prescribed limits in the fuel clad. Each completed fuel rod is then stored by the fuel rod manufacturer. A multitude of completed fuel rods are then configured in a parallel arrangement separated by fuel assembly spacers to prevent the fuel rods from contacting each other during use to form a fuel assembly. The technologies currently used to incorporate the nuclear fuel pellets into the fuel clad have several drawbacks and are therefore not economically efficient. Due to the sensitive nature of the components involved, the production of nuclear fuel rods requires quality assurance checks to ensure that defects do not occur during the production of the nuclear fuel rods. To eliminate human error, many systems and technologies attempt to use automated systems to eliminate worker involvement in the process. Although well intentioned, the automated systems must be carefully designed such that during fabrication of the fuel rod, no loose pieces and/or parts are generated which will jam the machine and stop production. The creation of these automated systems is extremely complicated and the systems created are prone to error due to the inability of designers to accurately predict the failure modes and problems encountered during production of the fuel rods. In current automated loading systems, nuclear fuel pellets are taken from a fuel pellet elevator and transferred by a conveyor to a segment make-up table. The pellets are loaded and discharged from the fuel pellet elevator with the assistance of a bar code reader which restricts entry and exit of the nuclear fuel pellets from the fuel pellet elevator. The fuel pellets are removed from the fuel pellet tray which carries the pellets and placed on a segment make-up table. The fuel pellets are placed in a parallel orientation and then compacted by a pusher device to form columns of uranium containing ceramic material. The pushing device is connected to a linear variable differential transformer which is configured to provide an electrical output signal. The signal is then read and an overall length of the individual fuel pellet column is determined. A computer then compares an overall design specification for the fuel rod with the output signal obtained from the linear variable differential transformer. If the difference between the expected design value of the nuclear fuel pellet column length and the measured value meets a predetermined threshold value, the fuel rod cladding is then loaded with the nuclear pellet column. If the overall length of the fuel pellet column is outside of the threshold value, the fuel pellets are then rejected from the segment make-up table. A top end cap is then welded the existing open side of the fuel rod cladding thereby completing the nuclear fuel rod. The automated systems which only use linear variable differential transformers cannot identify damaged fuel pellets which are positioned on the segment make-up table. These automated systems merely check for an overall length of the nuclear material to be incorporated into the clad and do not perform any other quality assurance checks during fabrication of the nuclear fuel rod. Thus, if an individual nuclear fuel pellet is cracked, the cracked fuel pellets will be loaded into the nuclear fuel rod as long as the overall length of the expected nuclear fuel pellet column is within established design parameters. In the case of an irregular shaped fuel pellet, as long as the overall length of the fuel pellet column is within expected overall length parameters, the cracked fuel pellet will be incorporated into the nuclear fuel rod cladding. If the fuel pellet is of an irregular shape, the pellet will bind on the tightly fitting clad and therefore jam the loading operations. An operator must then remove the nuclear fuel pellets from the segment make-up table. The loading apparatus must then be reset and a new fuel tray must be provided to the segment make-up table in order for production of nuclear fuel rods to continue. The unloading of the multiple nuclear fuel pellets from the segment make-up table while in a jammed condition requires numerous manual operations thereby stopping production of nuclear fuel rods. This jamming impedes the overall production capacity of the segment make-up device and severely limits productivity. An additional drawback of other fuel pellet loading systems is that these systems require continual fine tuning of the linear variable differential transformer systems in order to accurately measure the lengths of the nuclear fuel pellet columns present on the segment make-up table. Large numbers of the linear variable differential transformers are required for the fuel pellet columns on the segment make-up table to provide an accurate measurement of the fuel pellet columns present. There is therefore a need to provide a system which will accurately measure nuclear fuel pellet columns present on a segment make-up table. There is also a need to provide an apparatus and method which will enable an operator to perform additional quality assurance checks of the nuclear fuel pellets during the manufacturing process of a nuclear fuel rod. There is a further need to provide an apparatus and method which will allow for incorporation of ceramic materials inside nuclear fuel rod cladding such that the ceramic material is not harmed during the process of incorporating the ceramic materials into the fuel rod cladding. There is a further need to allow an operator to visually determine which fuel pellets should be included into a defined segment of nuclear fuel rod material such that the incorporation does not degrade the ceramic materials being incorporated into the fuel rod cladding. It is therefore an objective of the current invention to provide a system which will accurately measure nuclear fuel pellet columns present on a segment make-up table. It is also an objective of the present invention to provide an apparatus and method that will enable an operator to perform additional quality assurance checks of the nuclear fuel pellets during the manufacturing process. It is also an objective of the present invention to allow an operator to visually determine which fuel pellets should be included into a defined segment of nuclear fuel rod material such that pellets of improper uranium concentration or configuration are not loaded into to fuel clad. The objectives of the present invention are achieved as illustrated and described. The present invention provides a method to insert nuclear fuel pellets into a fuel rod cladding element, comprising the steps of providing the cladding element, providing at least one nuclear fuel pellet to be incorporated into the cladding element, measuring a length of the at least one nuclear fuel pellet with a camera, comparing the length of the at least one nuclear fuel pellet to an expected design length and incorporating the at least one nuclear fuel pellet into the cladding element when the compared length of the at least one nuclear fuel pellet is within a threshold value of the expected design length. The objectives of the present invention are achieved as illustrated and described in a second method. The second method provides insertion of nuclear fuel pellets into a fuel rod cladding element, the method steps comprising providing the fuel rod cladding element having a bar code on an exterior of the cladding element, reading the bar code on the cladding element, transporting the cladding element to a rod loader input queue, placing the cladding element on separator rollers, the separator rollers configured to separate the clad from each other, lifting the cladding element onto a vibration table, restraining the clad with a rod holding tool, inserting the cladding element into pellet funnels, the pellet funnels configured to accept a fuel pellets and transport fuel pellets into the clad, providing fuel pellets, the fuel pellets stored in pellet vaults, rotating the pellet vaults to a position to allow an operator to manually remove a pellet sheet containing the fuel pellets, manually removing the pellet sheet from the pellet vault containing the nuclear fuel pellets, deploying a segment stop across a segment make-up table to receive nuclear fuel pellets, discharging nuclear fuel pellets from the pellet sheet onto the segment make-up table, the nuclear fuel pellets positioned against the segment stop, pushing the pellets on the table against the segment stop, illuminating a laser to visually identify which of the nuclear fuel pellets should be incorporated into the cladding element, the laser calibrated to precisely visually indicate an expected length of a segment of nuclear fuel pellets to be incorporated into the cladding element, manually removing nuclear fuel pellets not illuminated by the laser from the table, measuring a cumulative length of fuel pellets in rows remaining on the table through the use of a camera, measuring the cumulative length of the fuel pellets in rows on the table through the use of linear variable differential transformers, verifying the cumulative length of the fuel pellets to a design specification of the fuel rod to a correct length, removing fuel pellets from the table which are not verified to the design specification correct length, transferring fuel pellets from the table which have been verified to a vibratory table input queue, and vibratory loading the fuel pellets from the table into the fuel rod cladding. The objectives of the current invention are also accomplished by a device for loading nuclear fuel pellets into nuclear fuel clad. The device comprises a fuel pellet vault to hold fuel pellet sheets, a segment make-up table to hold fuel pellets, a laser positioned to illuminate the segment make-up table such that the illumination range of the laser corresponds to segment lengths of fuel pellets to be incorporated into the nuclear fuel clad, a camera positioned to obtain data regarding an overall length of fuel pellets positioned on the segment make-up table, a vibratory table configured to vibrate fuel pellets into a fuel clad, a pellet pushing device configured to move fuel pellets from the segment make-up table to the vibratory table, a computer configured to receive the data from the camera and compare the data to a design specification, the computer further configured to indicate to an operator the result of the comparison, an arrangement to handle fuel clad, the arrangement including a rod loader device to accept fuel clad into the arrangement, and a feeding device to feed the fuel clad into a position where the clad can accept fuel pellets from the vibratory table and a pellet funnel arrangement to aid in the transfer of fuel pellets from the vibratory table into the fuel clad. Referring to FIGS. 1 and 2, a segment make-up system 10 is illustrated. A fuel pellet vault generally illustrated as element 12 is configured to accept nuclear fuel pellet, from a manufacturing facility. The pellets are placed upon fuel pellet sheets that are individually bar coded. As illustrated in the present invention, fuel pellets that have approximately the same concentration of fissile material are stored in the same fuel pellet vault 12. The fuel pellet vault 12 is in turn placed upon a fuel pellet vault turntable 14. The purpose of the fuel pellet vault turntable 14 is to rotate the supported fuel pellet vaults 12 such that a particular fuel pellet vault 12 is placed before an operator at position A who desires to access nuclear fuel pellets that contain a specified concentration of fissile material. The fuel pellet vault turntable 14 is controlled through an attached computer 46 which spins the turntable 14 to a position where an operator may access the fuel pellet vault 12 which has a specified concentration. Once the computer 46 issues the order to rotate the turntable 14 and the turntable 14 spins, the operator opens a door to the fuel pellet vault 12 and removes a nuclear fuel pellet sheet which contains the individual nuclear fuel pellets. Generally, the nuclear fuel pellet sheet is configured to support individual columns of fuel pellets such that the fuel pellets remain in place and do not shift during handling of the sheet. The operator manually removes this sheet and places the sheet upon a segment make-up table 44. A pellet pushing device 34 is then activated to unload the pellets provided on the fuel pellet sheet to the segment make-up table 44. The pellet pushing device 34 may include individual spring based elements to contact the columns of fuel elements placed upon the fuel element sheet. The pellet pushing device 34 may also move pellets placed upon the segment make-up table in bulk through the use of a single bar across the entire width of the fuel pellet sheet, the bar actuated through a spring mechanism or an pneumatic cylinder. The pellet pushing device 34 is configured to limit the amount of force exerted on the nuclear fuel pellets to prevent breakage of these pellets during transfer from the fuel pellet sheet to the segment make-up table 44. Although described as individual spring element devices, the pellet pushing device 34 may be any configuration to successfully offload nuclear fuel pellets from the fuel pellet sheet onto the remainder of the segment make-up 10. The pellet pushing device 34 is also configured such that when a nuclear fuel pellet is placed upon the segment make-up table 44, the pellet pushing device 34 slowly moves the nuclear fuel elements to a configuration where nuclear fuel pellets are aligned in a column form in rows 52 on the table 44. A laser 36 is then positioned over the segment make-up table 44 to illuminate the table 44 such that a pre-defined length of the nuclear fuel pellet columns on the table are illuminated. If a nuclear fuel pellet is illuminated by the laser 36 provided on the segment make-up system 10, then the individual fuel pellet should be incorporated into a nuclear fuel rod clad. If the laser 36 does not illuminate the individual fuel pellet, then the individual fuel pellet should not be included in the nuclear fuel element clad. The laser 36 may be located on a movable arm so that the laser 36 may be repositioned per the requirements of the operator. The laser 36 may also be activated by the computer 46 and/or timer to aid in the determination of which fuel pellets should be incorporated into the fuel rod. The laser 36 may be an industrial laser module Stock No. E-55-346 with power supply STK No. E55-323 from Edmund Industrial Optics, Barrington N.J. The laser 36 may be positioned upon a rotary table, such as a Daedel rotary table, CAT. No. 20502RTEPH2C2M1 E1T2 from Olympic Controls Wilsonville, Oreg. The laser may also be placed on a linear table CAT No. 06004CTEPD1L2C4M1E1 from Olympic Controls Wisonville, Oreg. A manual operation is then performed such that excess fuel pellets positioned on the segment make-up table 44 are removed and placed back upon the fuel element sheet. The fuel element sheet may then be removed from the segment make-up table 44 and placed back into the fuel pellet vault 12, thus keeping fuel pellets of like concentrations together. Alternatively, if the fuel pellet sheet is empty, the operator may stack the empty sheet in an empty sheet stack retaining device. The pellet pusher device 34 may also be configured to measure an overall length of the fuel pellet columns placed upon the segment make-up table 44. The pellet pusher device 34 may be actuated through a rodless actuator, for example a high speed ball screw model CAT. No. R4-B32-1518-56-P-BSE with RPS-2 Position Sensor at both ends for example. The overall length of the fuel pellet columns is measured, for example, through the use of a linear variable differential transformer connected to the pellet pusher device 34 and a stop 50 employed across the segment make-up table 44. The stop 50 may be either a fixed horizontal position or may be movable. After illumination of the nuclear fuel pellets by the laser 36, the operator then activates a camera system 38 which is configured to measure the overall length of the nuclear fuel pellet columns remaining upon the segment make-up table 44 through measuring a distance of the overall position of the pellet pusher device 34. The camera 38 may be any configuration or design which will allow an operator to successfully measure or allow an operator to measure an overall length of the fuel element column. A non-limiting example of the camera may be a DVT Legend Series Smartsensor 640×480 Monochrome Imager with L.E.D. No. PKG-540-MR-D. To aid in the analysis of the overall length of the fuel pellet columns, the segment make-up table 44 may be configured to allow light to pass through the table 44, thereby providing a backlighting situation for the pellets on the table 44 or the pellet pushing device may be light from the side for analysis by the camera. The segment make-up table 44 also may be configured with indentations to support the rows of fuel pellets being processed. Portions of the segment make-up table 44, such as the supporting part of the table contacting the fuel pellets may be placed on a roller carriage, to help transport fuel pellets from an entrance point to an exit point off of the supporting part of the table 44. The roller carriage may be, for example, a roller carriage CAT. No. 512P25A1 from Thomson Industries, Fort Washington, N.Y. The overall length of the fuel element column is measured by the linear variable differential transformer and\or the camera 38 and is then compared to a design specification which contains an expected length of the nuclear fuel pellet column. The comparison of the measured length and the expected length from the design specification is performed by a computer. If the nuclear fuel pellet column is within established tolerances and thresholds for the design, the nuclear fuel pellet column will then be incorporated into the nuclear fuel clad. If the comparison between the measured length of the nuclear fuel pellet column as provided by the linear variable differential transformer and\or the camera 38 is not within the threshold tolerance, the operator is then notified of the discrepancy for remedial action. The notification may be performed through the use of a warning light or computer display. The remedial action taken by the operator may include manually removing pellets from the individual nonconforming fuel pellet column in the event that a nuclear fuel pellet column is considered to be too lengthy. In the case of a nuclear fuel pellet column which is too short compared to design specifications, the operator may add nuclear fuel pellets to bring the overall length of the nuclear fuel pellet column into conformance with the design specification length. In the case of a nuclear fuel pellet column passing the overall length test, the fuel pellet column is then transferred to a vibratory table 28 for inclusion into the nuclear fuel clad. Individual clad are provided to the segment make-up system 10 such that nuclear fuel elements may be incorporated inside the volume defined by the clad. The individual clad may be inserted into an upset shape welder (USW) a TIG welder or a laser welder and a first end is welded onto the clad. A visual inspection is then carried out on the weld between the clad and the end cap. The visual inspection may include standard non-destructive weld examination techniques, including liquid penetrant tests and radiography as illustrative examples only. If the visual inspection of the weld is satisfactory, the clad is then moved to a rod translation station. Each clad is provided with a bar code to identify the individual fuel rod being manufactured. The bar code on the clad is read through a reading apparatus, such as a bar code scanner 54. The bar code may be placed upon the clad to positively establish a position of the clad by the placement of the bar code on the exterior portion of the clad. The clad is then transported axially to a rod loader input queue 56. As illustrated, the rod loader input queue 56 may store a number of clad units for manufacture. In the current illustrative embodiment of the application, twenty five clad may be stored in the rod loader input queue. Any number of clad units may be stored in the loader input queue 56. The clad are then transported by an elevator and eventually gravity fed down into the remainder of the segment make-up system 10 wherein the clad are held in position by a clad stop. The clad are then placed on separator rollers that transport the clad to a vibratory table input queue 58. The clad are lifted onto the vibratory table 28 for incorporation of the nuclear fuel pellets into the clad. A rod insertion\retraction system 60 then pushes the individual clad onto a rod holding tool 62. The rod holding tool 62 is configured to maintain the clad in position during further processing functions. The rod holding tool 62 is positioned on an exterior portion of the clad in a non-damaging manner to limit overall degradation of the completed fuel rod. Other positions and configurations of rod holding devices may also be used. After insertion of the clad into the rod holding tool 62, pellet funnels 32 are then selected according to the design specification of the nuclear fuel rod being manufactured. The pellet funnels 32 that are selected for use are based upon the overall diameter of the fuel elements being incorporated into the fuel clad. The pellet funnels 32 are made of non-damaging material so that insertion and deletion of the pellet funnels does not degrade the surface of the fuel rods. The pellet funnels 32 have the individual clad inserted into the funnel 32 for transfer of nuclear fuel pellets. The vibratory table 28 with the nuclear fuel pellets is then activated by the operator causing the nuclear fuel pellet column to vibrate toward the fuel pellet funnel 32. After entering the funnel 32, the pellets are transported down the fuel clad and are stacked in an end to end relationship. After all of the nuclear fuel pellets are incorporated into the fuel clad from the vibratory table 28, the rod holding tool 62 is then released. After releasing the rod holding tool 62, the fuel pellet funnel 32 is removed from the open end of the fuel rod clad. The clad is then discharged from the segment make-up system 10. After discharging the clad from the segment make-up system 10, internal vibration dampers and a gaseous atmosphere may be inserted into the clad prior to second end welding by an upset shape welder. An internal depth of the plenum remaining in the nuclear fuel clad may then be checked at a plenum check station 70 wherein a rod is inserted into the filled fuel clad. If the insertion of the calibrated rod meets expected parameters, the fuel clad is then considered acceptable and may be further processed. If the fuel clad plenum deviates from expected parameters, then the fuel clad is considered potentially defective and is rejected from further processing until expected parameters are achieved. A second end may be welded on the fuel clad. The second end welding by the upset shape welder is then inspected for defects. If the fuel rod clad is free from defects, the fuel rod may be then incorporated into a nuclear fuel assembly. The present invention also provides the capability of providing different enrichments of uranium into a single clad, thereby allowing the manufacturer to tailor the reactivity of the fuel rod along the axial length of the completed fuel rod. To accomplish the placement of different enrichments of uranium in a single fuel rod, pellets from differing pellet sheets containing different concentrations of fissile fuel may be added together on the vibratory table in desired sequences. The pellets, after passing the criteria presented above, are then incorporated into the fuel rod clad. The present invention allows several advantages over other systems for loading nuclear fuel rod clad. The present method and device to load nuclear fuel pellets into fuel clad allows the nuclear fuel pellets to be incorporated into fuel clad in a systematic manner such that the fuel pellets are loaded efficiently and safely. The current invention also allows an operator to visually check whether or not the nuclear fuel pellets provided by the fuel pellet vaults conform to an expected design. The present invention also provides a configuration that does not damage the fuel pellets during the manufacturing process of the nuclear fuel rod. The use of the vibratory table allows for the incorporation of the nuclear fuel pellets into the nuclear fuel clad without unnecessary stress being placed on the nuclear fuel pellets. Measurements of the overall length of the nuclear fuel pellet columns is performed through the use of a camera, thereby minimizing contact with the uranium containing ceramic fuel pellets. Additionally, the rod holding tool is configured to hold the fuel clad such that damage does not occur to the fuel clad during loading operations. All of these systems ensure a leak tight and contiguous nuclear fuel rod. Another advantage of the present invention is that the camera used to measure the overall length of the nuclear fuel element column does not need to be continually fine-tuned unlike other systems for loading nuclear fuel elements into cladding. The use of the camera, therefore provides for greater economy in the overall operation of the device described. The camera may also be used to supplement linear variable differential transformer readings in order to more accurately provide quality measurements for the overall length of the nuclear fuel element columns. The present invention also provides for accurate loading of nuclear fuel allowance into fuel clad without having the drawbacks of creating a jamming condition throughout the segment make-up system. The elimination of error prone systems allows the present invention to operate without having the significant drawbacks of jamming which occurs in other systems previously used. As a consequence, the elimination of jamming conditions allows for continuous production of nuclear fuel rods with minimized down time. The present invention also eliminates the use of numerous overhead cranes systems to transport fuel clad from processing station to processing station. The present invention allows fuel clad to be loaded into a rod loading input queue and from this position use gravity during subsequent processing steps. The elimination of numerous lifting devices during the processing of the nuclear fuel clad eliminates the need for expensive maintenance and repair of these systems and provides a more reliable system for processing of the clad. In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.
	claims	1. An intelligent air conditioner socket with abnormality alarm comprising a housing, jacks on the surface of the housing and a conductive component arranged within the housing, characterized in that:the housing having a single chip processor, a current detection module, a voltage detection module, an outdoor temperature detection module, an indoor temperature detection module, a display module and a power supply module wherein the current detection module, the voltage detection module, the outdoor temperature detection module, the indoor temperature detection module, the display module and the power supply module are electrically connected with the single chip processor respectively, wherein the power supply module is connected with the display module to power it;the current detection module and the voltage detection module to detect a sampled current and a sampled voltage output to the air conditioner after the power network is connected to the socket respectively, wherein the sampled current and the sampled voltage are fed back to the single-chip processor respectively through an operational amplifier circuit;the outdoor temperature detection module and the indoor temperature detection module to detect outdoor and indoor temperature signals and feeding the signals back to the single-chip processor;the single-chip processor is a control and a processing core, the single-chip processor to conduct voltage abnormality detection, current abnormality detection and temperature abnormality detection respectively using the feedback signals;wherein the voltage abnormality detection comprises comparing a difference between the sampled voltage and a rated voltage with a preset normal voltage difference, if the difference exceeds the preset normal voltage difference, an input voltage of the air conditioner is determined to be overvoltage or undervoltage, and a voltage abnormality alarm signal will be output;the current abnormality detection comprises comparing a difference between the sampled current and a rated current with a preset normal current difference, if the current difference exceeds the preset normal current difference, an input current of the air conditioners determined to be overcurrent or undercurrent, and a current abnormality alarm signal will be output;the temperature abnormality detection comprising determining whether a predetermined temperature reduction magnitude is within the range of an actual temperature reduction magnitude(−120%, +120%) within a time period T.di-elect cons.T.sub.0−Tm, and if not, an abnormality alarm signal will be output; wherein the actual temperature reduction magnitude=F(Tm)−F(T.sub.0), F(T.sub.0) is an initial indoor temperature, and F(Tm) is the indoor temperature at Tm; and the predetermined temperature reduction magnitude=.SIGMA.T.sub.0.about.Tm [voltage T(v)current T(a)]nominal energy efficiency ratio (B)/nominal space area (A)coefficient of performance R(T)*nominal power factor C, wherein the voltage T(v) and the current T(a) are the sampled voltage and sampled current detected at time T respectively, and the coefficient of performance R(T) is the corresponding coefficient of performance of the outdoor temperature and the indoor temperature at time T; andthe display module to display the current temperature, power and abnormality alarm prompts output by the single-chip processor. 2. An intelligent air conditioner socket with abnormality alarm according to claim 1, characterized in that: the single-chip processor prestores a table of values of coefficient of performance at different outdoor temperatures and indoor temperatures directly or indirectly, and reads the value of the coefficient of performance R(T) corresponding to the outdoor temperature and the indoor temperature at time T form the table. 3. An intelligent air conditioner socket with abnormality alarm according to claim 1, characterized in that: the power supply module is a switching power supply which comprises a rectifier IC, a transformer and an isolation optocoupler. 4. An intelligent air conditioner socket with abnormality alarm according to claim 1, characterized in that: the current detection module uses constantan wire as a current detection device. 5. An intelligent air conditioner socket with abnormality alarm according to claim 1, characterized in that: the display module comprises a display IC and a digital display screen. 6. An intelligent air conditioner socket with abnormality alarm according to claim 1, characterized in that: the outdoor temperature detection module and the indoor temperature detection module use an external thermistor as a temperature sensor to detect the outdoor and indoor temperatures, respectively.
	description	This application is a continuation-in-part application and claims the benefit of and priority to co-pending U.S. patent application Ser. No. 12/688,353, filed on Jan. 15, 2010, which claims the benefit of and priority to U.S. patent application Ser. No. 12/099,077, filed on Apr. 7, 2008, now U.S. Pat. No. 7,973,299 which claims the benefit of and priority to U.S. provisional patent application Ser. No. 61/022,174, filed on Jan. 18, 2008. This application also claims the benefit of and priority to co-pending U.S. patent application Ser. No. 12/557,703, filed on Sep. 11, 2009, which claims the benefit of and priority to U.S. patent application Ser. No. 11/611,627, filed on Dec. 15, 2006 and which issued on Oct. 27, 2009 as U.S. Pat. No. 7,608,847, which claims the benefit of and priority to U.S. provisional patent application Ser. No. 60/751,371, filed on Dec. 16, 2005, the disclosures of which are hereby incorporated by reference. The present invention relates in general to radiation protection and, more particularly, to a suspended personal radiation protection system. Radiation is used to perform many medical diagnostic and therapeutic tests and procedures. Medical, veterinary, or research personnel may be involved in the performance of these tests and procedures. These professionals are being exposed to scattered radiation as they perform their work. The long-term effects of this exposure are poorly understood at the present time, but are considered serious enough to warrant mandatory protection for operators, who are required to wear garments or barriers that contain materials, which absorb a significant proportion of the radiation. In order to properly perform tests or procedures on patients, operators require freedom of motion. Providing a personal radiation protection system and method that properly protects operators, while allowing operators to move freely and comfortably, presents a significant challenge for operators in radiation environments. In accordance with the present invention, a method and apparatus for implementing a suspended personal radiation protection solution are provided as disclosed herein. According to one embodiment of the present invention, a system for offering radiation protection includes a garment that substantially contours to an operator's body. The garment protects the operator from a substantial portion of radiation which is scattered about during a treatment or testing procedure. The garment is supported by a suspension component that reduces a portion of the garment weight on the operator. In one series of embodiments, jib cranes can be used for supporting the personal radiation protection system. Jib cranes typically utilize an arm that rotates around a post in the horizontal plane. A trolley can move along the arm of the jib, and anything may be suspended from the trolley, such as the radiation protection device and/or a balancing mechanism. When combined with a balancing mechanism to counteract the weight, it thus allows freedom of motion of the suspended object in the X, Y, Z spatial volume defined by the arc of the arm's rotation. The base may be attached to a ceiling, floor, wall, portable stand, or other fixed object. Many variations or enhancements upon the above described basic system can occur with jib systems. In one series of embodiments of the radiation protection system, the suspension component comprises a reaction arm, manipulating arm, balancing arm, articulating arm, torque arm, and/or other rotating-jointed, articulating, mechanically assisted manipulator. In these embodiments, the garment is attached to a frame which is directly and rigidly secured to such articulating suspension component or components. This is in contrast to embodiments of related applications where the frame is suspended by rope or wire, which, in some circumstances, may undesirably introduce slack, suffer from delayed suspension component movements, or even cause backlash, which is a common problem encountered in any tethered arrangement. Several terms exist for the above-mentioned rotating-jointed, articulating, mechanically assisted manipulators, such as: reaction arm, manipulating arm, torque arm, balancing arm, and articulating arm. Due to their similarity, they may be used herein interchangeably. In any case, there are at least two arms connected by joints that have at least one degree of freedom, and the joints are oriented such that the end load has at least two degrees of freedom. The end load can therefore move anywhere in the XY spatial planes by following any path. A third degree of freedom can be added for free motion in the XYZ volume either by adding joints in the system that allow vertical movement of the arms, combined with springs or pneumatic system for opposing gravity, or by using a vertical balancing system as described in related applications. In accordance with a preferred embodiment of the present invention, the suspension apparatus connects to and supports the shield and/or garment device about its center of gravity or about a point or points in close proximity to the shield and/or garment's center of gravity. This improves motion with regard to certain operator movements, such as bending forward or sideways. Suspension of the shield and/or garment about its center of gravity, or substantially close to the center of gravity or in the coronal (frontal) plane containing the center of gravity, can be accomplished using a ball-in-socket joint along the garment frame, or by pivoting the garment frame about strategically placed axles or pivot joints. In another embodiment of the present invention, a non-overhead means of suspension is discussed. The frame is supported at or near its center of gravity by a balancing arm, which is itself rotatably secured about the upright post of a floor-based stand. Floor-based docking and ceiling-based docking are possible as depicted herein. Variations of the floor-based stand may include: a mobile floor stand with wheels and counterbalancing weights; a mobile floor stand with an anchoring means for locking the floor stand in place; or, a mobile floor stand that is stabilized by a stationary ceiling post. Another alternative embodiment of the present invention involves a portable, floor-based, shield and/or garment-suspending back table. Such a back table can comprise a portable track stand which allows lateral sliding movement of a balancing arm for suspending the radiation shield/garment. Alternatively, the shield/garment can be suspended by a table-mounted manipulator arm, articulating arm, reaction arm, or balancing arm which can be rotatably secured to the back table by a table-mounted upright post. Several means for securing the back table to the floor are disclosed, including: stowable floor hooks, floor rings, lockable table wheels, and/or counterbalancing weights or a combination thereof. Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions and claims. While specific advantages and embodiments have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. For purposes of teaching and discussion, it is useful to provide some overview as to the way in which the invention disclosed herein operates. The following information may be viewed as a basis from which the present invention may by properly explained. Such information is offered for purposes of explanation only and, accordingly, should not be construed to limit the broad scope of the present invention and its potential applications. Radiation is used to perform many medical diagnostic and therapeutic tests and procedures. The human patient or animal is subjected to radiation using minimal doses to enable completion of the medical task. Exposures to radiation are monitored to prevent or reduce risks of significant damage. Medical, veterinary, or research personnel may be involved in the performance of such procedures in great numbers. Over many years, these professionals are being exposed to scattered radiation as they perform their work. Although their daily exposure is generally less than that for the patient, there are adverse cumulative effects to the operators. These long-term effects are poorly understood but are considered serious enough to warrant mandatory protection to workers in the form of garments or barriers that absorb a significant proportion of the radiation. There is a wide variety of such barriers commercially available, but these solutions have significant limitations for the operators who must come in close contact with the subject. These operators may be physicians and their assistants, or technically skilled medical personnel, who perform simple or complex medical procedures using their bodies and hands in proximity of the patient. In many cases, scatter radiation from the subject or physical elements in the direct radiation beam will pose significant health risks and unacceptably high exposure. Risks of radiation exposure at the levels of medical personnel include cancers, cataracts, skin damage, etc. A review of current protective systems outlines their limitations. Radiation-absorbing walls are useful to contain the radiation to a room, but do not prevent exposures within their confines. Barriers within the room (such as floor or ceiling supported shields) are effective at blocking radiation for personnel who are not in close contact with the radiation field (such as some nurses and technologists) but must be positioned or repositioned frequently when personnel move around the room. They also provide cumbersome interference for operators performing the actual medical procedure. They may also be difficult to keep sterile when attempting to use them within the sterile field. The most commonly used protection for operators involves the use of garments containing radiation-absorbing materials, generally lead or other metals, which are worn in the fashion of a coat, smock, skirt, vest, etc. and do not contaminate the sterile field because they are worn underneath the sterile covering gown. These garments are heavy and uncomfortable, and their long-term usage is known to be associated with diseases of the spine (in the neck and back), knee disorders, and other musculoskeletal problems, which can result in disability, medical expenses, and decreased quality of life for the operator. The trade-off between protection and garment weight results in the frequent use of garments that do not cover the legs, head, torso, and eyes optimally, and may provide sub-optimal radiation protection due to the thickness of the metallic material being limited by the tolerability of the operator. To protect other radiation-sensitive tissues (such as the corneas of the eye and the thyroid), special heavy glasses containing metallic compounds and a collar around the neck are often worn. Even when the operator is encumbered with these items, the base of the skull (which may contain sensitive bone marrow) and the face are still unprotected. Personal face and neck shields address this problem, and are commercially available, but are rarely worn due to their cumbersome nature and heavy weight. Such problems have been present for many years and there are current solutions that attempt to address them. Modifications to floor-supported mobile shields appear to attempt to provide improved dexterity for the operator relative to the standard bulky mobile barrier, and a floor support system with a modified garment design also attempts the same. However, they are still obstacles to free movement of the operator. Another system of barriers (such as those referred to as radio-protective cabins) around the patient has been proposed, but that appears cumbersome, confining, and inhibitory to operator movement both gross and fine, patient/subject contact, and sterile field operation. Ceiling mounted barriers around the patient also appear to limit contact between patient and operator, and may make control of a sterile field difficult. One configuration includes a ceiling mounted device, which supports the weight of a lead garment, involving a dolly movable in one linear axis, with or without an extension arm that rotates around a central point on the dolly. Such mechanical configurations are in place for other types of suspended barriers and their motion mechanics may not be well suited for use with something attached to the operator's body since the operator must frequently move rapidly and freely in all three spatial axes. Typically, the operator will walk in unpredictable and rapid patterns over an operating area. One configuration includes the garment being suspended by a simple expansion spring, which will provide uneven forces depending on its degree of expansion occurring with operator motion (due to the nature of its simple spring mechanics). It may also result in harmonic motions that affect operator dexterity. In addition, failure of the spring due to cycle stresses could lead to operator injury. In addition, location of the spring in a vertical direction above the operator could result in limitations due to ceiling height. Integration of the system with the heavy image intensifier monitor screen could further encumber the operator from normal motion. A discussion of the types of motion performed by operators during their work is relevant. Operators generally stand next to an operating table where the patient is positioned. They often reach over the patient to various parts of the body, and they may lean forward while reaching for items, surfaces, etc. This puts stress on the spine when heavy garments are worn. They may bend or stoop, but rarely is this possible because the workplace containing the patient limits vertical motion. In addition, most procedures involve a sterile field where the operator's hands, arms, and torso (from neck to waist, in the front and sides) must remain confined, so excessive vertical motion is prohibited. Nevertheless, motion in the vertical axis is required to some degree as the operator moves. The operator may move considerably in the x and y plane, which is horizontal and parallel to the floor, by walking or turning their body. The operator thus requires freedom of motion in all three spatial axes. Overhead cranes have been available for many years and are commonly employed in the materials-handling industry. The following is a description of a bridge crane. A bridge crane includes at least one bridge, and a trolley moving on the bridge, end trucks arranged at the ends of the main bridge to support the main bridge, wheels arranged to the end carriages intended to move along substantially parallel rails substantially parallel to the end trucks. In some embodiments, articulated end trucks provide increased maneuverability for the bridge so as to allow the bridge to rotate or sway, while staying safety attached to the rails. Smaller cranes (such as those to be used to support a load up to 250 pounds) are often operated by workers without the aid of motorized assistance because the crane's movable parts are light enough to be manipulated by hand. Different systems are employed to suspend the load from the cranes, including hoists, balancers, balancing arms, articulating arms, manipulators, and intelligent assist devices. Tool balancers are currently available and help to suspend tools in the workspace in a manner that provides ergonomic benefits for workers using them. The tool balancer is generally attached over the workspace, and reels out cable from which the tool is suspended. Adjustments may be made to provide a “zero gravity” balancing of the tool at the desired height such that the worker may move the tool up or down within a working range without having to bear a significant portion of the tool's weight. Adjustments may cause the tool balancer to exert a stronger upward force such that the operator must apply a downward force on the tool to pull it down to the workspace and the balancer will cause the tool to pull it down to the workspace and the balancer will cause the tool to rise when the operator releases it. Tool balancers may be of the spring, hydraulic or pneumatic variety, referring to the mechanism, which provides the force for its operation. A spring tool balancer, such as in one embodiment of the invention disclosed herein, generally contains a coiled flat spring (similar to a clock spring), which is attached to a reel with a conical shape and which serves as the platform for the winding of the cable. The conical shape provides a variable mechanical advantage, which offsets the variance of the force provided by the spring as it winds or unwinds. The result is a relatively constant force on the cable within a definable working range. Safety concerns mainly involve falling objects, strength of the suspension device, strength of the cable, and operator falls. The balancer can be attached to the trolley by its own hook and a safety chain. The suspension device is commercially available at specified maximum loads, which include a wide safety margin. The mounting of the suspension device will be done according to architectural/engineering standards where the present invention is to be utilized. Tools or other loads may also be balanced by arms that provide torque approximately equal to the weight of the load via various mechanical systems including internal cables and pulleys with springs, pneumatic force, or counter-weights. Such arm systems could be manipulator arms, torque arms, reaction arms, or balancing arms as are known in the art. Detachment of the radiation protection system from the suspension system will require certain care. A cable stop for cable-mounted garment systems will prevent the hanger from going higher than the set level. Some balancers are equipped with a locking mechanism that prevents motion of the cable during load change or removal. This permits simple removal or exchange while standing at ground level. Alternatively, without activating a locking mechanism, the worker could stand on a step stool and lift the load upwards until it contacts the balancer stop, or until the arm is fully raised to its capacity in the case of an arm system, and then remove the garment without concern for sudden upwards, uncontrolled motion of the balancer cable or arm, and attached system. Alternatively, a weight, which is approximately equivalent to the weight of the garment, could be attached to the hanger, cable, rod, or arm prior to disengaging the garment. This will drop the system and require it to be supported by the worker, who may then disengage it from the hanger. The weight will prevent any upward motion of the components in an uncontrolled manner. The next time the garment is attached, the weight could be removed after secure attachment of the system is confirmed. For most operations, the protection system need not be detached from the suspension system (e.g. cable, rod, or arm supporting the system). It could be left suspended and moved out of the way of other activities. Another alternative method would involve setting the force on the balancer or pretensioner to be slightly greater than the weight of the garment. Once removed from the body, the garment would then slowly and safely rise up until stopped by the cable stop or other safety-stopping mechanism—such as rotating-joint stops for manipulators, balancing arms, and articulating arms. Upon next use, it could be easily pulled back down into position. Annual inspections of the system may be performed for cable frays, hook lock malfunctions, rotating-joint bearing failures or seizures, movement stops, and/or rail component flaws. In the event of an operator fall, it is unlikely that the system will contribute to operator harm since in some embodiments the suspension system allows the operator to reach the floor without restriction. In view of the embodiments disclosed herein, the design of the system provides for the safe and quick detachment of the operator from the radiation protection system. The binder system quickly provides engagement/disengagement from radiation protection system as the binding forces keeping the operator in proximity to the radiation protection system would be easily overcome by the forces exerted during a fall. In the event of malfunction, many support systems are equipped with automatic locking mechanisms to prevent dropping of the load supported by the support system. In the event of actual detachment, the frame supporting the suspended shielding components may be designed such that there are pads positioned over the shoulders of the operator which would gently engage the operator's shoulders to support the weight of the device in the event of a suspension failure. However, this type of malfunction would be rare as it would generally be avoidable with adequate support structure strength and annual inspections of the entire system. In the event that rapid detachment of the operator from the system is necessary due to emergency, the binding system disclosed herein is designed to provide simple and quick disengagement between the operator and the radiation protection system. As disclosed further herein, a simple hand push or wave or actuation of a switch by the operator or another in various embodiments results in the operator disengaging quickly and safely from the radiation protection system without detachment of the garment from the system. The garment can be left hanging on the system and then moved clear of the patient or stretcher. Likewise, the operator can quickly disengage from, and then reengage with, the system while remaining sterile. Turning back now to the general problem of radiation, it is evident that operators are often exposed to radiation in the course of their work. The proposed concept, outlined herein, describes a device and technique intended to address many of the aforementioned problems. It provides extensive shielding for the operator: covering a large part of the body. The shielding capacity can be increased with thicker, heavy metal layering, thus reducing a dose to the operator because the device is weightless [or nearly so] to the operator. The device is close to the body of the operator, much like a conventional apron, however it is not supported by the operator. It moves substantially in concert with the operator as he/she moves around within the working field and sterile field, and allows movement of arms and body parts to accomplish the procedure at hand. The overall effects of the device include: improved comfort for the operator who is no longer supporting heavy-shielding clothing, improved radiation protection to an operator through a much greater portion of body shielding (compared to a conventional apron), as well as more effective shielding of much of the covered parts due to the substantial contour of the garment to the operator and thus better use of the shielding material. This approach also offers a musculoskeletal benefit due to the absence of a significant weight burden on the operator. FIG. 1 is a perspective view of one embodiment of a suspended personal radiation protection system 10, which is shown in greater detail in FIG. 2, where a rigid, substantially vertical suspension component 24 of a ceiling-mounted articulating arm 22 is used to directly attach to a radiation protection garment 14, in accordance with the present invention. System 10 may also include an operator 20, a patient 28, a radiation source 16, radiation rays 26, a suspension component 22, and frame 30 for supporting a radiation protection garment 14. The system 10 may also include a face shield 12, and an arm hole sleeve cover 18. Each of these components is discussed in further detail herein. In general, and as illustrated in FIG. 2, the garment 14 is suspended from a frame 30 which is in turn supported by a given suspension component. In one embodiment, hanger 32 is attached to frame 30 (or “garment frame”), which is the skeleton that contours around the shoulders, chest and torso of the operator 20. Frame 30 supports garment 14 and face shield 12, along with other devices such as an instrument tray, environmental control (e.g. a fan, a heater, an air conditioning device) and/or lighting apparatus. Frame 30 may be integrated—rigidly or with articulation—with hanger 32, or may be attached directly to the suspension component as required by operational mandate. In one embodiment, hanger 32 is a rigid rod that connects frame 30 to the desired suspension component, such as a reaction arm, balancing arm, a manipulating arm (“manipulator”), an articulating arm, any number of wire ropes, or any other suspension component described or envisioned herein. Attaching frame 30 to a suspension system over the operator's head, and roughly over the center of gravity, can have advantages for facilitation of balance and proper orientation of the device. Alternatively, attaching frame 30 in any other location, such as behind (as depicted in FIG. 2) or to the side of the operator 20, can offer advantage with regard to positioning of the suspension system in an alternate location, other than overhead the operator 20, for better function in some environments. FIG. 2 further illustrates the system architecture by a perspective view of a personal radiation protection system 10. An operator 20 may position herself in relative proximity to the garment 14 and frame 30 such that the operator 20 is not supporting the weight of the garment 14. In this sense, she is liberated from the typical and problematic weight constraint. While using radiation 26 during a procedure or task, the operator 20 can freely move in the X, Y and Z spatial planes such that the garment 14 and face shield 12 are substantially weightless. Garment frame 30, or when coupled with hanger 32, can lead upward from any portion of the garment system 10 to attach to an overhead suspension system such as a bridge system or reaction arm. Alternatively, frame 30, or when coupled with hanger 32, can lead to the suspension system in a non-overhead location by passing rearward, and/or to the side of the operator 20, as shown. Some embodiments of the invention depicted may also utilize a gimbal, end effector, or other type of articulation within the frame 30 or hanger 32, close to the operator 20 or near the center of gravity of the system 10 to facilitate certain movements, as described later herein. The rearward or sideward frame component 30 may arise at other levels of the operator 20 other than the shoulder, such as closer to the waist, or midway between shoulder and waist, or possibly lower. FIG. 3 is an elevated side view of the manipulator-arm-type, or reaction-arm-type, garment suspension system 40 seen in FIG. 1, in accordance with the present invention. A manipulator arm suspension assembly 40 allows the operator to move freely in the X, Y, and Z planes while maintaining proximity to and protection by the protection system. Suspension system 40 includes a post 42, which, in this embodiment, is attached to a moveable system consisting of ceiling rails and a trolley on wheels as depicted in FIG. 1. Post 42 alternatively could be attached to a fixed point, such as a wall or ceiling. A first arm 46 is attached to the post 42 such that the first arm 46 may rotate about a rotating first joint 44 in a planar fashion. A second rotatable arm 52 is attached to the first arm 46, and is also operable to rotate about a rotating second joint 48 in the X, Y plane and to rotate about a rotating third joint 50 in the Y, Z plane. The second and third joints 48, 50 may alternatively be combined into a single ball-and-socket (or “ball-and-cup”) joint to provide rotation in the X, Y, and Z space. A third arm 58 is operable to rotate about a rotating fourth joint 54 and a rotating fifth joint 56 in various planes relative to the second arm 52. Similarly, the fourth and fifth joints 54, 56 can be combined into a ball-and-socket joint. The joints connecting each of the arms described above are well known in the art and may consist of friction joints, torque joints or substantially frictionless connection joints using well-known means such as bearings or bushings. In this particular embodiment, arm 52 contains a linkage system (not depicted) that maintains the orientation of third arm 56 in the vertical axis, perpendicular to the first arm 46. As fifth joint 56 allows rotation in only 1 vertical plane, instead of infinite vertical planes as with wire rope, the remainder of the arm will more responsively follow the operator as he or she moves, starting and stopping in concert with the operator. In contrast, with wire rope suspension systems, the rope will first angle before pulling the arm, which may then give some undesirable backlash effect as it passes over the operator in a delayed manner, and comes to rest after the operator. The depicted device may also contain (not shown) an internal spring and cable mechanism that acts upon joint 50 between second arm 52 to first arm 46 to maintain an upward force of the suspended protection system approximately equal to its weight. It may have friction built into the joints so that there is some difficulty moving them, and then when the operator releases, the systems remains. In an alternative embodiment, the joints could be substantially free of friction to allow more fluid motion while working. FIG. 4 is an elevated side view of an alternative suspension component (which can be used in place of the articulating/manipulator arm 22 depicted in FIG. 1) comprising another embodiment of a reaction arm 60, in accordance with the present invention. Arm 60 is a type of articulating arm that can provide a predetermined amount of upward force to counteract the force of gravity that acts upon the desired tool or load to be attached at the end of the arm 60. A reaction arm (or torque arm) with parallelogram construction (i.e., dual, parallel hinged arms acting as one unit), such as that depicted, can allow translation in the X, Y, and Z space of the suspended load, while maintaining the load's pitch orientation. Parallelogram construction maintains effector pitch orientation even in the face of opposing torque forces that would otherwise result in rotation of the object (i.e. undesirably changing its orientation in the YZ plane). Balancing arm 60 shown in FIG. 4 is a heavy duty articulating arm with two boom or arm sections 66, 76 extending serially, via rotating joints 64, 68, 74, 78, from a mounting post 62. The mounting post 62 can extend upward to attach to the ceiling or a ceiling-mounted structure, such as the trolley and bridge crane assembly shown in FIG. 1. Alternatively, the mounting post 62 can extend downward to attach to the floor or a floor-based stand, such as any one of the examples shown in FIGS. 10, 11, 14, and 15. The mounting post 62 can even extend from floor to ceiling, as can be seen in FIG. 12. Returning to balancing arm 60 of FIG. 4, the first boom (or arm) section 66 rotates in a horizontal plane around mounting post 62 via a first joint 64. Second boom 76 also can rotate in a horizontal plane about a second joint 68 located at the end of first arm 66 opposite mounting post 62. Second boom 76 is also capable of rotating (tilting, swinging, or swiveling) in a vertical plane about a third joint 74. If it is desirable for the load-handling end of second boom 76 to maintain its pitch (i.e. forward/backward angle relative to vertical) regardless of the pitch/tilt of second boom 76, second boom 76 may comprise parallelogram construction (i.e. a pair of parallel arms and end joints). Hydraulic cylinder 72 can be used to provide a weight-counterbalancing force to the end of second boom 76. One end of hydraulic cylinder 72 attaches to a leverage extension 70, which may extend upward or downward from the end of boom 76 next to third joint 74. The other end of hydraulic cylinder 76 attaches to some point along second boom 74 to provide a torque about third joint 74 to oppose the torque caused by gravity on the load-bearing end of second boom 76. A zero-gravity, load-balancing effect is thereby provided for the operator. In other embodiments, many other types of balancing mechanisms or linkages are possible, including the use of cables, springs, and reels in various linkage systems. Other degrees of freedom of motion in various joints can be added or subtracted to provide the necessary freedoms and limitations to fit the working situation. FIG. 5 is an elevated side view of another alternative suspension component comprising a manipulator arm 80 that is holonomic (i.e., having six degrees of freedom) or perhaps even redundant (i.e., having seven or more degrees of freedom), where the manipulator arm 80 has a rotatable pitch axle wrist having at least three degrees of freedom for supportive attachment to the frame 30, in accordance with the present invention. A redundant or at least holonomic manipulator 80 is particularly advantageous because its range of motion and flexibility of orientation approximate those of the human arm. A human arm is considered to have seven degrees of freedom: a shoulder gives pitch, yaw, and roll; an elbow provides pitch; and a wrist allows for pitch, yaw, and roll. While three degrees of freedom enable positioning in three-dimensional space, additional degrees of freedom are needed to adjust the orientation (pitch, yaw, and roll) of the end effector (or hand). Three degrees of freedom in the manipulator arm shown in FIG. 5 enable the positioning of the end effector at any location in space (defined, for example, by X, Y, Z coordinates). The shoulder portion 82, which comprises a rotatable base 84 and a shoulder pitch joint 86, provides yaw and pitch motion to the manipulator 80. The rotatable base 84 enables rotation or yaw about an upright post for securing the manipulator 80 to a stable point above and/or below the manipulator 80 (such as to an overhead bridge and trolley as seen in FIG. 1, or to a floor stand such as that shown in FIG. 10, 11, 14, or 15). The shoulder pitch joint 86 enables an upper arm portion 88 of the manipulator 80 to tilt or pitch upward or downward. A lower arm (or forearm) portion 92 connects to the end of upper arm 88 via an elbow joint 90, which also allows for upward and downward pitch. At the opposite end of lower arm 92 is a robot wrist portion 94, which is rotatable about a wrist pitch joint 96. The robot wrist (or mechanical wrist) 94, which is shown in more detail in FIG. 6, provides an additional three degrees of freedom for orienting the end effector to a desired pitch, yaw, and roll. To help provide a zero-gravity-like environment for the shield 12 and/or garment 14 at the end of the manipulator arm 80, a hydraulic cylinder can span between the upper arm 88 and lower arm 92 to apply a counterbalancing torque about the elbow joint 90. A hydraulic cylinder can similarly span between the lower arm 92 and the wrist 94 to provide counterbalancing torque about the wrist pitch joint 96. In the depicted embodiment, frame 30 can attach to the wrist 94 of the manipulator arm 80 (via a hanger 32, if desired). To facilitate the ease of manipulating and orienting the shield/garment 12, 14, the hanger 32 is more preferably located as close as reasonably possible to shield/garment's center of gravity. This concept will be discussed in further detail in the description of FIGS. 7-9. If desired, a seventh degree of freedom can be provided to the manipulator arm system by using a manipulator hand 102—connected to the end of the wrist 94 that is capable of surge (i.e. extending forward and retracting backward). The hanger 32 and/or frame 30 may be made considerably shorter, allowing the robot wrist to be much closer to the operator, or closer to the center of gravity of the radiation protection system. This may provide more facile fine movements of the operator during pitch, roll, or yaw of his body. This may also be provided by altering the shape of the frame handle 30 or frame 32. Alternatively, additional joints of various configurations and functions may be placed within hanger 32 and/or frame 30 to provide additional degrees of freedom and means for connection to the manipulator arm 80. FIG. 6 is a perspective view of the wrist 94 of the manipulator arm 80 seen in FIG. 5, as well as the three perpendicular axes of rotation 106, 108, 110 for its three rotating joints 96, 98, 100, in accordance with the present invention. The wrist portion 94 of the manipulator arm 80 provides three degrees of freedom and approximates the flexibility of a ball joint (and the flexibility of the human wrist) by combining three perpendicular joints in a relatively compact space. The wrist pitch joint 96 connects the lower arm 92 to one end of the wrist 94 and has a horizontal axis, which enables the wrist 94 to tilt upward and downward, thus providing pitch. A wrist yaw joint 98 is located in the middle of the wrist 94 and has an axis orthogonal or perpendicular to that of the wrist pitch joint 96, thus providing yaw. At the wrist end opposite the wrist pitch joint 96 is a wrist roll joint 100. The wrist roll joint 100 comprises a rotatable base for providing roll. The wrist roll joint's rotational axis 110 is orthogonal or perpendicular to the axes of rotation 106, 108 of both the wrist yaw joint 98 and the wrist pitch joint 96. The closer in proximity that each of the wrist joints can be to one another, in the closer the wrist will be to behaving similarly to a spherical wrist. A spherical wrist is where the three axes of rotation actually intersect. Note that in the particular embodiment shown in FIG. 6, although the wrist yaw axis 108 and the wrist roll axis 110 do intersect, the depicted wrist 94 is non-spherical because the wrist pitch axis 106 and the wrist yaw axis 108 do not intersect. Spherical wrists (compared to non-spherical wrists) can be more compact and can reduce the degree of manipulator arm movement necessary to re-orient the shield/garment while maintaining the shield/garment's current spatial position. Non-spherical wrists, however, can be mechanically simpler and more robust. In order to provide proper balance of the radiation protection device and orientation in space, some of the joints permitting some of the degrees of freedom of the robot arm and wrist may include balancing systems to counteract the effects of gravity on the arm components and the radiation protection device, to render it substantially weightless. Such counterbalancing mechanisms will usually be used to counteract motion in the Z axis (vertically, due to gravity) but may also be incorporated to some degree in the other axes to accommodate the intended circumstances of usage. For example, counterbalancing may be employed in the pitch joint of the wrist, and in vertically moving joints in the arm. The counterbalancing mechanisms may be comprised of any type of system known in the art such as a pneumatic system, simple springs, complex springs, counterweights, or systems of cables and springs with reels. FIG. 7 is a block-diagram functionality-sketch—with four sub-FIGS. 7A, 7B, 7C, and 7D—of the center-of-gravity garment attachment concept, where side views 7A, 7C and frontal views 7B, 7D are offered of an axle-based and ball-in-cup-based suspension system, in accordance with the present invention. Previous discussions have focused on the suspension of the shield/garment device from the upper portion of its frame. Now we will expand upon suspension mechanisms that are in close proximity to the center of gravity of the shield/garment device in order to improve its motion with regard to certain operator motions such as bending forward or sideways. When a heavy object is suspended near its top (the point farthest from the earth and its gravitational pull), that object will not easily bend or tilt because such changes in orientation require forces in partial opposition to the gravitational forces. An operator may wish to partially bend over sometimes, as when leaning over the patient table a bit to reach for something. The operator would encounter the forces described, inhibiting the motion somewhat, although not preventing it. It is desired to limit these forces and render the shield/garment system easily tilted and/or bent (or creased or folded). This difficulty can be alleviated by suspension about an object's center of gravity or by a point near its center of gravity. One way to address this is to attach the suspension mechanism to the shield/garment system at its center of gravity. Depending on the type of joint used, this can lead to great ease of tilting or bending in some or all directions because gravitational forces are cancelled out, and the only force required is the minimal force required to overcome friction and accelerate the object into motion. To prevent unwanted free rotation, friction at the joint may be incorporated to desired level, and/or the device can be suspended at a point slightly above the center of gravity so that it tends to orient itself vertically but still requires only minimal force to rotate it. In FIGS. 7A-70, a typical suspension assembly is shown for the support of a load, which includes an axle system shown in FIGS. 7A and 7B, and a pivot system shown in FIGS. 7C and 7D. Such a system may be a rigid structure such as a rod (shown) or a flexible structure such as a wire rope. Flexible wire rope would allow more freedom of rotation in the YZ plane, which can be desirable or undesirable depending on the situation of use. For example, FIG. 8 offers perspective views of a ball-in-cup center-of-gravity attachment of the frame 30 to a suspension arm 120, with the left perspective view (FIG. 8A) showing the garment 14 in a natural and upright position, and the right perspective view (FIG. 8B) showing the garment 14 in a sideways-bending stance, and where the suspending arm 120 retains the same basic orientation in both instances, in accordance with the present invention. In this embodiment, there is a ball-in-socket joint 122 connecting a rigid suspension arm 120 to the frame 30. The garment portion covering the frame 30 has been removed to depict the frame 30. The center of gravity is high due to the density of the frame and garment making the overall shield/garment/frame system top heavy. By utilizing the ball-in-cup joint 122, the operator can accomplish side-to-side bending and forward bending while the shield 12 and garment 14 remain in proper orientation relative to the operator, and little resistance to these motions is encountered. The ball and cup joint 122 could be replaced by many different types of joints, such as needle in cup (with needle oriented with a vertical bias, and the cup in a corresponding manner), various manner of bearing or bushing joints, a universal type joint, an axle configuration, or a simple flexible connector such as a wire rope or strap which would permit forward bending. In the event that the center of gravity is located behind the front of the garment 14, possibly at a location that is extremely close to the operator's chest or torso, or perhaps within the operator's body, then it would not be feasible for an attachment at that exact location. However, several practical solutions are possible that permit iso-gravitational freedom of rotation in all planes. Likewise, a counterweight could be added to change the center of gravity forward to a more practical location for attachment. The counterweight would be integrated with the frame 30 in a manner to accomplish this goal, and could be placed as an extension of the frame 30 in any direction to increase moment arm of the counterweight, thus permitting a lighter counterweight to be used. The attachment could be as close as practical to the center of gravity. It does not need to be exactly at the center of gravity, because by being close to it, the forces required to tilt the device would still be minimal, especially since the overall weight of the device is expected to be less than 40 lbs. As another example embodiment, FIG. 9 offers perspective views of axle-based center-of-gravity attachment of the garment frame to a suspension component, with the left perspective view (FIG. 9A) showing attachment via unilateral axle, the next perspective view (FIG. 9B) showing attachment via bilateral axles and swiveling hanger, the next perspective view (FIG. 9C) showing attachment via bilateral axles, and the right schematic view (FIG. 9D) showing the wire ropes replaced with a rigid frame whose top portion is described by an arc with its center at the center of gravity, at the level of the pivot joints, in accordance with the present invention. An axle system could be employed to provide attachment location at the center of gravity in the Z axis (vertical). As seen in FIGS. 9A and 9B, this would therefore allow excellent forward bending function, without facilitating sideways bending, which may be less important or even undesirable in some situations. The axles could be located at the side(s) only, without running through the center where the operator's body may be located. Another option could be to place suspension components on both sides, such as wire ropes 130 (FIG. 9C), or rigid frame (FIG. 9D), which could be looped or passed over an overhead pulley to provide sideways bending function with great ease. The axle joint could be a simple shaft-in-bearing housing allowing only rotational motion of the shaft, like a bicycle wheel axle. This would allow a unilateral suspension arm configuration which could allow pitch while preventing roll as might be desired in this configuration to maintain proper orientation of the device. Instead of an axle, any type of rotating joint allowing rotation could be used. On the left in FIG. 9A, the unilateral axle 124 is at the height of the center of gravity, but it is suspended just left of it. This would allow easy forward bending for the operator, but sideways bending would not be markedly facilitated. In FIG. 9B, bilateral pivots 126 are present slightly above and to the left of right of the center gravity of a frame 30 with a different shape. This allows similar function as the embodiment shown in FIG. 9A, but with the option for using less bulky and strong unilateral support members. A pivot joint rotating in the horizontal plane is integrated with the hanger 32, enabling yaw in the system allowing the operator to twist his body along with the system. In FIG. 9C, bilateral attachments 126 to frame 30 at or near the center of gravity may be rigid since they are connected to wire ropes 130. They do not need to rotate as axles if the wire rope attachment allows rotation. The pulley system 128 overhead allows the system to bend sideways. Yaw would be enabled by flexibility in the wire rope, or the placement of a rotating joint above the pulley that allowed its rotation in the horizontal plane, similar as that depicted in FIG. 9B. This embodiment has somewhat similar function as the ball-and-cup joint at the precise center of gravity, without the need for placing a joint at or near the point of the center of gravity for the system, which may lie within the operator's body or otherwise inaccessible. In another embodiment shown in FIG. 9D, wire ropes are not used. Instead, a rigid hanger frame 120 may slide on a pulley. The hanger frame 120 includes an arc whose center is coincident with the center of gravity for the system, thus free rotation (roll) is allowed with very little force or change in weight bearing by the pulley 128. Not shown in this schematic are possibilities that facilitate its use, such as shaping of the lower hanger component to accommodate arm movement. The vertical component of the hanger may have many different shapes to facilitate fit and function, so long as the top arc is defined by its center at the center of gravity, and its highest point is directly over the center of gravity in the vertical Z axis. The pivot joints 126 allow pitch, the pulley 128 and arc hanger frame 120 allow roll, and yaw can be enabled using a pivot above the pulley as previously described, giving full ability to rotate about the center of gravity in all planes. When using a harness and binding system as described previously, the binding components may benefit from being placed at the same height as the center of gravity attachment. This will facilitate the linkage between operator and device with regard to bodily motion in the XY plane, such as with walking forwards or sideways. If the binding components are not at the same level as the attachment at the center of gravity, such motions of the operator will exert forces on the device that are sufficiently large to cause rotation about the attachment site, creating undesirable motions since in this situation, the operator would want the device to remain in its neutral orientation while it followed the operator's body as they walked. This undesirable effect would be more important for ball-and-cup type joints, than for a purely axle- or pivot-type joint as in the FIGS. 9A and 9B, where sideways motion of the operator would not cause roll of the garment as it might with a ball-and-cup. Therefore, these designs could be useful when the operator binding site is not near the center of gravity. In other embodiments, the preferred attachment site may be slightly above the center of gravity of the system, so the device remains in its neutral orientation for most operator motions in the XY plane, but is still amenable to tilting when the operator bends forward or sideways. In addition to the embodiments shown in FIGS. 9A-9D, a simple tether suspension could be used, such as a wire rope attached directly to the system at its center of gravity. FIG. 10 is a perspective side view of a portable, floor-based, non-overhead suspension system 140 having a mobile floor stand 142 with an upright post 144 and manipulator arm 146 for distal attachment and suspension of a shield/garment 14, via frame 30, substantially about the garment's center of gravity, in accordance with the present invention. For better stability, the mobile floor stand 142 includes weights 148 along a broad wheelbase 150. The wheelbase 150 has locking (or lockable) wheels 152 for securing the base 150 in position on the floor. Also, the wheelbase 150 is constructed of sufficient dimension and properly counterbalanced with sufficient weight to prevent tipping when the balancing arm 146 is fully extended and laden with the shield/garment 14. The balancing arm 146 is substantially horizontal and approaches the operator and shield/garment system from the side or back, rather than from overhead. In other embodiments, the arm could approach front the front. In this embodiment, the end effector 120 (end of the balancing arm) approaches the operator from the side at the level of the chest, then curves around the front, and attaches at the center of gravity of the frame of the shield/garment using a ball-and-cup joint 122. This system allows movement of the operator in the procedural area defined by an arc with a radius corresponding to the length of the arm. By putting the stand or mounting system a few feet from the operator, the operator's feet and body are not at risk of accidentally bumping into any part of the suspension system. This offers great advantages over any floor mounted system lacking the ability to distance (via articulating balance arms, for example) the operator wearing the shield/garment 12,14 from the bulk of the suspension system. A modified coat hanger, for example, might be capable of suspending a shield/garment so that the operator is not burdened by its weight. Such a modified coat hanger, however, would be in extremely close proximity to the operator. Without articulating balancing arms to distance the stand from the operator, the operator would be at great risk of inadvertently bumping into or tripping over parts of the stand. This system also offers advantages relative to an overhead floor based suspension system such as seen in FIG. 20, in that the post is not as tall and therefore need not be as wide to manage the same torque forces resulting from the arm and suspended system. Overall weight is reduced, and the system is more portable with fewer overhead collision issues with other apparatus. The system may also be transported through doorways without the need for telescoping posts. While a ceiling-mounted system (as opposed to a floor-based system) would prevent any possibility of tripping over floor-based suspension components, the floor-based portable system 140 shown in FIG. 10 has advantages over a ceiling mounted system, especially in some specific environments: crowded ceilings are not a problem with this embodiment; the device can be wheeled into different procedure suites in the same institution; there could be some cost savings related to the absence of ceiling mounting, or the need for reinforcement of the ceiling and expensive analysis of structural support; the absence of overhead structures can reduce risk of collision with other structures such as hanging lights, hanging shields, or a moving image intensifier, which is often angled obliquely towards the operator and is located over their head. Other configurations are possible, including a very short post, or no vertical post, with the arm attached to the wheelbase of the stand and extending upward to the attachment site with the radiation protection system. The arm could also be affixed rigidly to a site on a fixed surface, including the floor, wall, patient table, or stable back table. Also, the arm may attach to the frame with many different types of joints described elsewhere or located in other locations on the frame (e.g. an axle or pivot joint with one degree of freedom on the right side of the frame allowing forward tilt of the operator). The frame could be altered to allow a lower point of connection, by being extended more inferiorly towards the floor. FIG. 11 is a perspective side view of the portable, floor-based, non-overhead suspension system of FIG. 10 modified for floor-based docking, in accordance with the present invention. By extending downward a floor-docking post or pole 154 from the bottom of the floor stand 142 into a receiving sleeve or channel in the floor or ground, the mobile floor stand 142 can be securely docked in place. The floor-docking post 154 increases the suspension system's ability to withstand torque applied to the end of the balancing arm 146 due to the weight of the suspended shield/garment/frame components 12, 14, 30 by docking the post 154 with this fixed surface. When not docked, the system 140 could be unstable with the arm 146 extended and load 12, 14, 30 attached. To permit undocking and portability without removal of the load 12, 14, 30, a system could be employed involving a locking mechanism for the portion of post 144 docked under the floor level 154, such that it cannot be telescoped back into the base 150 until unlocked. Unlocking would be enabled only when the arm 146 is swung in so that the supported weight is positioned very close to the post 144, thus reducing torque. Once the post 144, 154 is retracted and undocked, the arm 146 would lock so that it could not be extended to make the system 140 unstable. The arm 146 could be unlocked once the post 144, 154 is docked again to this fixed surface. This safety mechanism can be incorporated into each of docking system embodiments described herein. Although FIG. 11 depicts one embodiment of this floor docking mechanism with a non-overhead suspension system, the floor supported system could be utilized with any of the described arm or jib systems, including overhead suspension systems. It could also be utilized with a bridge system where it might offer advantage if a floor-based bridge system were set up in a cantilevered fashion requiring stabilization as could be offered by this floor docking mechanism. Other types of floor docking mechanisms are possible. Any number of the wheels could be designed to bind or attach securely to components on the floor to provide stability and prevent translational or rotational (tipping) motion of the stand. Other extensions or plurality of extensions from the device could attach as described above for the wheels. The attachments could be rails allowing some degree of motion in some directions. Any type of securable attachment system could be envisaged using mechanisms widely known in the art. FIG. 12 is a perspective side view of the portable, floor-based, non-overhead suspension system of FIG. 10 modified for ceiling-based docking, in accordance with the present invention. By extending upward a ceiling-docking post or pole 156 from the top of the floor stand 142 into a receiving sleeve (e.g. a ceiling-post sleeve 158) or channel in the ceiling 160 or other ceiling-mounted structure, the mobile floor stand 142 can be securely docked in place. The ceiling-docking post 156 increases the suspension system's ability to withstand torque applied to the end of the balancing arm 146 due to the weight of the suspended shield/garment/frame 12, 14, 30 by docking the post 156 to this fixed surface. The diameter and bulk of the post 156 can be substantially reduced, and the wheelbase and weight of the base may also be reduced relative to non-docking systems. In the embodiment shown, the floor docking mechanism is depicted with a non-overhead suspension system; however, it could be utilized with any of the previously described arm or jib systems, including overhead suspension systems. It could also be utilized with a bridge system where it might offer advantage if a floor-based bridge system were set up in a cantilevered fashion requiring stabilization as could be offered by this floor docking mechanism. Also, floor docking and ceiling docking (fixed surface) mechanisms could be present in the same device. Other types of ceiling docking mechanisms are possible. Other extensions or plurality of extensions from the device could attach to sites secured to the ceiling. The attachments could be rails allowing some degree of motion in some directions. Any type of securable attachments system could be envisaged using mechanisms widely known in the art. FIG. 13 is a perspective side view of a portable, floor-based, back-table-mounted garment suspension system with non-overhead suspension 170, in accordance with the present invention. The embodiment shown in FIG. 13 allows for articulated, balanced arm support of the operator's shield/garment by relatively inexpensive modification of commonly used back tables (fixed surfaces). This helps reduce operator fatigue (due to the cumbersome weight of the shield/garment) without requiring the installation of a ceiling-based mounting system, such as a bridge crane and trolley, which can be quite expensive and/or complex, and without having to set aside precious floor space for a dedicated garment-holding floor stand. Such a back-table-mounted (fixed surface) suspension system is portable, therefore it can be easily moved with the back table from one room to the next, or even simply moved out of the way when not in use. A typical radiological examination room (and/or operating room) has a patient table 172 with an image intensifier 174 at one end of the room (which relative end will be referred to herein as the front of the room). The operator 20 generally works behind or adjacent the patient table 172 while wearing the radiation-blocking shield/garment 12, 14 with his or her back facing the back of the room. A back table 176 is located behind the operator 20 towards the back of the room and is used by the operator 20 to keep his or her tools and/or other equipment within convenient reach. With a few modifications to the typical back table—such as providing extended table legs (or outriggers) 178 for widening the table's base and providing locking wheels 180 and/or floor hooks—the back table 176 can be made stable enough to serve as a secure fixed-surface support platform for a shield/garment-suspending articulating arm and/or balancing arm 182 system. With a few modifications, it is also possible, in the alternative, to mount such a shield/garment-suspending articulating arm and/or balancing arm system at many different possible locations 184 including on the patient table or even to a point on the floor as depicted 184. Although the depicted embodiment is shown with a non-overhead articulating arm, any type of arm or jib system, including overhead or non-overhead, could be modified and used in alternative embodiments. FIG. 14 is a perspective view of one embodiment of a portable track stand 190 for use with the back-table-mounted garment suspension system 170 shown in FIG. 13, where stability is provided by the track stand's broad base 192 and locking wheels 194, in accordance with the present invention. Stand 190 rolls multi-directionally on wheels 194. It contains two track rails 196 that allow a trolley 198 to move longitudinally along the track via trolley wheels 200, while also providing the ability to withstand the moment arm forces produced by the weight of the balancing arm 202 (mounted onto the trolley 198) and shield/garment device (not shown). Trolley wheels 200 may be lockable, so that the trolley can be locked in the desired working position so that further motion during work is only available in the arm system connected to stand 190. The top of the portable track stand 190 may be covered or otherwise modified to simultaneously serve as a back-table. FIG. 15 is a perspective view of another embodiment of a portable track stand 210 (in the depicted embodiment, a floor-locking portable track stand) for use with the back-table-mounted garment suspension system shown in FIG. 13, where stability is provided by at least one stowable, recessed floor hook 212, in accordance with the present invention. In this embodiment of the portable track stand/table 210, there is attached to the floor a mechanism, hook 212, that can attach to and detach from a crossbar 214 along the base of the table 210 using simple operator movements. It stabilizes the table 210 by preventing the backside from elevating due to the torque created by the attached balancing arm 216 and the suspended radiation protection device (not shown). This allows a substantial reduction in weight and/or wheelbase of table for stability purposes and serves to further minimize unwanted lateral motion of the table 210 along the floor that might occur in small degrees even with the wheels 218 locked in place. One or more floor hooks 212 may be used in any of the portable stands or back table embodiments described herein and as required by the operational requirements. Alternative embodiments may provide a locking safety mechanism similar to that described in FIGS. 11 and 12 which only permits unlocking from the floor when a load is stowed over or close to table, and the support arm cannot be extended unless locked to floor. FIG. 16 is a perspective view of one variation of the stowable, recessed floor hook(s) 212, in accordance with the present invention. To prevent obstruction or tripping of personnel when the floor hook is not being used, the floor hook 212 can fold down into a recess or inset 220 in the floor. To stow away the floor hook 212, the operator might, for example, first rotate the floor hook 212 ninety degrees (90°) counter-clockwise, then fold it down into floor. Once in the floor (i.e. within the correspondingly-shaped floor recess 220), the floor hook 212 would lie flat/flush with the floor without risk of being obstructive. In yet another variation of the floor hook 212, the hook 212 can freely rotate about its floor attachment, allowing the table 210 to change orientation while securely but rotatably held by the floor hook 212 to this fixed surface. The floor hook 212 itself, along its hooking surfaces, can also have top rollers and side rollers (“top” and “side” relative to the table crossbar being hooked) 222 to allow the table 210, while hooked, to shift laterally—from side to side—along the floor (i.e. along its long axis) for increased range. FIG. 17 is a perspective view of another embodiment of a portable track stand 230 (more specifically, a cam-locked portable track stand) for use with the back-table-mounted suspension system 170 shown in FIG. 13, where stability is provided by at least one stowable, recessed floor ring 232 and at least one cam-locking hook (or other cam-locking ring catch) 234, in accordance with the present invention. The floor ring 232 folds up from the floor inset (or recess) 236, and the cam-locking hook 234, which has an operating handle 238 for locking the hook 234 and tightening its hold, attaches to it. The operator squeezes the cam lock handle 238 closed. This action shortens and tightens the apparatus, pulling downward as it locks, to provide sufficient downward pull on the table 230 to prevent it from wobbling or lifting slightly off its wheels when weight is applied on the balancing arm. There is also a length-adjustor mechanism 242 on the shaft of the cam lock 234 to provide coarse adjustment of the length. This mechanism can be supported from a trolley 242 with trolley wheels 244 that can roll freely along the track attached to the legs of the table 230. Such a rail system can be applied to any of the floor-docking table systems described herein. As in previous embodiments, this stand 230 can simultaneously serve as a back-table for procedural supplies by placing a tabletop on it, for example, and covering it with a sterile drape as is customarily done. A joint allowing rotation of the floor ring 232, and/or of the shaft for the cam-lock hook 234 that grips the ring 232, will allow rotation of the table 230 in the plane of the floor with the floor ring 232 as the center of rotation. There can be a safety mechanism to prevent unclamping of cam lock 234 while the shield/garment (or other load) is positioned on the balancing arm 240, as a sufficient torque applied against the balancing arm 240 might undesirably allow the table 230 to tip. To prevent the need to remove the load, the balancing arm 240 and its load could be placed into a parked position where the load is positioned substantially over the center of the table 230. FIG. 18 is an elevated top view of the range of motion available to the portable track stand 250 for use with the back-table-mounted garment suspension system 170 shown in FIG. 13 and with the floor-securing means depicted in FIGS. 15-17, in accordance with the present invention. The floor hook 254 is positioned near the middle of the table 250 in the neutral position, hooking the crossbar of the table as previously described. The table can be rolled to the left or right, or rotated around the hook 254 as shown, giving great range to the balancing arm 252 and shield/garment attached thereto. FIG. 19 is a perspective view of the portable, floor-based, back-table-mounted garment suspension system 170 shown in FIG. 13 where an example table-mounted manipulator arm 182 is depicted in two positions: an operating position and a parked position, in accordance with the present invention. The table 176 may be unhooked from the floor when tension is released from the hook mechanism 212, indicating the table 176 is stable. This can be achieved by removing the load, or in this instance, by rotating the load substantially over the table 176 to remove moment arm or torque forces. Another embodiment of safety lock could involve a mechanical linkage between a table-to-floor locking mechanism, and the arm such that the locking mechanism can unlock only when the arm is swung into a safe position where the table is stable without tethering to the floor. The device can swing over or under the table 176. The latter has the advantages of space savings, lower center of gravity, non-obstruction of the tabletop area, and better aesthetics. The garment 14 may be constructed to roll or fold up so that its vertical distance is reduced, allowing the device to park more easily in the space available. FIG. 20 is a perspective view of a back table 262 combined with a jib arm and trolley suspension for the radiation protection system 260. In this embodiment, a frame 266 on wheels 268 supports a column 272 for a jib-boom system. A table top 264 is connected to the frame 266 and serves as the fixed surface back table 262 for the operator's supplies. Underneath the table top 264 is a compartment 270 containing weights and a motor system to move the system 260 via powered wheels 268. A sterile drape may be placed over the table top 264 as is common in the art. The column 272 may also include hooks 274 for hanging medical supplies or instruments. The column 272 may telescope to change its height, and which may be facilitated with a counter-balance system 286 (of any type, but the use of counterweights may be advantageous to provide more weight and stability) to negate the weight of the upper column 272, boom 278, and suspended components 290 (e.g., garment/shield). A rotating joint 276 between the boom 278 and the column 272 allows rotation of the boom 278 in the horizontal plane. In this embodiment, the boom 278 is telescoping with an integrated trolley 280 with anti-kickup wheels 282 and side rollers 284, although a conventional boom could be used. A trolley 280 has linear motion along the boom 278. The radiation protection system 290 is suspended by a wire (or line) 288, and its weight is counterbalanced by a balancer 286 attached to the trolley 280, and placed rearward for counterbalance advantage in this embodiment. The entire system 260 allows free motion of the protection system 290 in the X, Y, and Z space. The system 260 may be moved into any position in the workplace by the motorized drive and at least two of the four wheels 268 are provided so as to allow steering. The table 262 is deep to create a long wheelbase in the short axis, to increase stability. In this embodiment, the table's front has an arced cut-out 292 to permit more ergonomic usage by the operator despite its deep shape. System 260 may prove advantageous over a separate floor mounted jib boom and back table because much space is saved, and it may be possible to put the post at any location by design, rather than working around the table. This may allow a shorter boom to reach the area of use, allowing less force to move it, and less bulky construction of the boom and base. Likewise, it may be possible to situate the support closer than a ceiling mounted system where ceiling obstacles may necessitate longer booms. It also obviates the need for ceiling tracks since the post may be moved by moving the table. Many variations of this system are possible including different shapes of the frame or table, numbers of floor contacts or wheels, function of column including any of the various mechanisms described elsewhere such as ceiling or floor docking, conventional boom with conventional trolley and balancer arrangement directly below trolley, absence of motorized drive, use of any other type of arm mechanism including robot arms, holonomic arms, or articulating arm systems of all types, or arms extending horizontally from the table/stand and attaching in a non-overhead manner as described in FIG. 11, or any of numerous mechanisms of counterbalancing the radiation protection system. The telescoping boom has the advantage of permitting the end of the boom to be retracted when overhead obstacles are encountered, such as the image intensifier, as seen in the Figure. With the telescoping boom design in FIG. 20, the operator is directly underneath the end of the boom, so the boom end will not collide with objects that are not directly overhead of the operator. There are many possible modifications and variations of the mobile floor stand system and/or the manipulator-type arm discussed thus far. However, the following example embodiments are not to be construed as limiting the scope of disclosure or claims herein with regard to the scope and spirit of the present invention. If desired another stabilization and safety mechanism can be built-in to the portable floor-based suspension system: the base, stand, or table can attach to the floor via a component that slips down into a mechanism in the floor that grips it. This could be a hole in the floor with internal teeth or some other mechanical binding system to grip a table component—such as a rod or key—that inserts into it. A plurality of these mechanisms could be employed. The action of locking the table to the floor can be the required mechanism for unlocking another lock on the tabletop, which allows the articulating/manipulator/balancing arm to swing out from its docked position over the table. The arm would then be available for suspending the radiation shield/garment for operations. After use, the shield/garment/apron-suspending arm could then be swung back over the table top so that the table, arm, and garment are stable without the floor lock. When docked over the table, a lock can automatically activate to keep all components in position. If desired, the docking and locking action can also simultaneously deactivate the locking/binding mechanism in the floor so that it is unlocked, thus releasing the table from the floor and allowing it to be moved. As discussed above, FIGS. 10-20 depict a variety of suspended radiation protection devices wherein a significant portion of the weight of the apparatus is supported by the floor, although it is contemplated that many alternative embodiments are possible within the scope of this invention. It is noted that alternative embodiments may include various components disclosed herein. For example, any of the different overhead or non-overhead suspension systems disclosed herein may be used on any device. Jib arms may be used where articulating arms are described, and vice versa. Motorized components may facilitate movement of the tables or stands, or movement of the suspension components such as the trolley. Other devices commonly known in the art besides wheels may be used to facilitate table motion, such as belts. A track may be present in the floor that supports and guides the table, which may ride on the tracks on wheels, rollers, or other common mechanisms. The tables or stands may be stabilized by secure, detachable attachment of one or more legs or components to the floor in fixed locations, wherein the tables or stands may not be slid or rolled about the floor once attached. This could also stabilize the table from tipping due to the cantilevered load. In various contemplated embodiments, stability may be provided by detachable or non-detachable connections to the tracks upon which the devices ride, slide or roll. Wheels, rollers or bearings positioned on the legs, or the bottoms of the stands or tables, may be capable of sliding or rolling inside a track which is attached to the floor, or imbedded within this fixed surface. This track could be securably attached to the floor so that the table or stand, once engaged in the track, could not be pulled away from the floor without substantive force, and therefore would not tip or fall. This engagement could be permanent, or semi-permanent and accomplished using mechanisms widely known in the art. A safety mechanism such as a mechanical lock or detent could be employed to prevent accidental dislodgement and de-stabilization of the device. Likewise, a single track or multiple tracks could be used for stabilizing the system disclosed herein. In the event of a single track, it could be attachable to the legs or side of the table opposite the suspended load, to prevent that side from rising up. Stabilization could also be provided through different means. A counterweight may be present in a remote location from the remainder of stand, base, table, or suspended apparatus. For example, it could be attached to a rigid arm extending in the opposite direction relative to the suspended device, thus counterbalancing it. It could be positioned above head level to remain free of personnel motion. It could be positioned lower to be free of obstructions higher in the room. The combination of weight and arm length could be chosen to provide the necessary counterbalancing effect while addressing other logistical considerations of each application or operating suite. The counterweight arm could be stationary, or it could be movable to allow optimization of its position. It could be linked with the arm for the suspended radiation protection device to remain in ideal counterbalancing position during use of the system. While the invention has been particularly shown and described with reference to a various embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
046860789	summary	BACKGROUND OF THE INVENTION Nuclear reactor ultrasonic inspection devices have long been available for scanning welds when a reactor is shut down for refuelling and its open reactor vessel is submerged in a water pool. Such devices typically include a spider assembly having legs spanning the reactor vessel flange at its open upper end, a telescopic vertical column mounted in the hub of the spider coaxial with the vessel, and a telescopic horizontal boom at the lower end of the column carrying the scanner. U.S. Pat. No. 3,780,571 is typical of the disclosures of such devices. It is characteristic of prior art inspection apparatus that they involve complicated telescopic and rotational drives often with pulley and cable systems, all of relatively high cost and substantial weight. It is the principal purpose of the present invention to provide a method and apparatus for displacing a reactor weld scanner into and out of position by a system which is inexpensive and which can be assembled at the site with lightweight individual parts transportable by one man. SUMMARY OF THE INVENTION The invention provides a method of displacing a weld scanner in and out of a horizontal reactor vessel nozzle, wherein vertical guide studs extend upwardly from an upper circular vessel flange with the studs and vessel submerged in a water pool. The scanner is mounted on a horizontal positively driven telescopic boom to which a vertical column is attached which is slideable between stop limits within a hub of a spider having legs adapted to span the flange with clamps on the outer ends of at least two legs adapted to slide on and grip two of the studs. Any or all of the boom and column and spider legs defines a buoyancy chamber into which air and water may be introduced. The method comprises the steps of first introducing air into the buoyancy chamber. The scanner-boom-colummn-spider assembly is then floated in the pool with the upper end of the column extending above and the scanner and boom extending below the water surface. Some water is then introduced into the chamber to cause the scanner-boom-column to sink relative to the spider until the column is stopped at its lower limit in the hub. Positioning rod means are then affixed coaxially to the upper end of the column. More water is then introduced into the buoyancy chamber to sink the scanner-boom-column-spider assembly at substantially neutral buoyancy with the rod means projecting at its upper end above the pool surface. The rod means are then manipulated and then more water is introduced into the buoyancy chamber so that the leg clamps are lowered about the studs and the spider legs descend onto the vessel flange. The clamps are then closed to fix the spider relative to the vessel. The rod means are next moved vertically and rotated to bring the scanner to a level coaxial with the nozzle. The telescopic boom is then positively extended to enable inspection by the scanner in the nozzle. After inspection the boom is positively retracted and the spider clamps are opened. Air is then introduced into the chamber until the entire assembly is buoyant. The rod means are manipulated as the assembly lifts upwardly off the studs and to the surface and then the rod means are detached. In a preferred form of the method the spider has three legs, two of which have clamps slideable on two studs, each of the three legs having a buoyancy chamber. Each of the boom and column may also define a buoyancy chamber. The column may be rotatable on the hub and adapted to be braked with respect to the hub. After retraction the boom may be rotated by the rod means to be under one of the spider legs. After the boom is retracted and before the clamps are opened air may be introduced into the spider legs chambers to render them positively buoyant while the other chambers are still negatively buoyant. The water introduced into the buoyancy chambers may be maintained separate from the pool water. The boom may be provided with two fore and aft buoyancy chambers. In combination with a weld scanner mounted on a positively driven telescopic boom to which a perpendicular column is attached, the invention also provides apparatus for buoyantly displacing the scanner in and out of a horizontal reactor vessel nozzle wherein vertical guide studs extend upwardly from an upper circular vessel flange with the studs and vessel submerged in a water pool. The apparatus of the invention comprises a spider having legs adapted to span the flange. A central hub is provided in the spider in which the column is slideable. Stop means are included for limiting the slideable movement of the column in the hub. Clamps operable by remote control are included on the outer ends of at least two legs adapted to slide and grip two of the studs. At least one of the boom and column and spider legs defines a buoyancy chamber. Means operable by remote control are included for introducing air into and releasing it from the chambers. Means operable by remote control are also included for introducing water into and draining it from the chambers. Positioning rod means are provided coaxially attachable to the column remote from the boom for manipulating the scanner-boom-column-spider assembly when submerged. The weight of this apparatus is such that it is buoyant in water when air is introduced into the chambers. In a preferred form of the apparatus two guide studs extend from the flange approximately 120 degrees apart and the spider has three substantially equally spaced legs with clamps included on two of the legs. Each of the boom and column and spider legs may define a buoyancy chamber and the boom may define two fore and aft chambers. The water supply for all of the chambers may be separate from the pool water. Braking means operable by remote control may be provided for controlling axial and rotational displacement of the column in the spider hub.
	description	This application claims the benefit of U.S. provisional application entitled X-RAY GENERATOR WITH POLYCAPILLARY OPTIC, application No. 61/044,148 filed on Apr. 11, 2008, the entirety of which is hereby incorporated by reference. 1. Description of the Related Art The present invention relates systems for generating and focusing x-ray radiation for analytical instruments including x-ray diffractometry, x-ray spectrometry or other x-ray analysis applications. 2. Description of the Known Technology There are numerous analytical instruments and procedures for which x-ray radiation is directed onto a target for analytical or metrology applications. Examples of such instruments include those based on the principles of x-ray coherent scattering such as x-ray scattering and x-ray diffraction, and those based on the principle of x-ray fluorescence such as x-ray spectroscopy and x-ray elemental mapping microscopy. In many such applications, there is a need to direct an intense beam of x-rays having controlled beam characteristics in its interaction with the target. These characteristics include spatial definition (divergence, beam size, focal spot size and intensity distribution at different locations), spectrum purity and intensity. However, these characteristic parameters can not be optimized independently. Improving one often comes at price of others. X-rays are inherently difficult to direct. Different technologies have been employed to form x-ray beams. These include total reflection reflectors, optics based on total reflection principle such as capillary and polycapillary made of bundle of micro-sized waveguides, natural crystals, and man-made layered structures called multilayer optics. In some cases, polychromatic radiation with energy spectrum over a relatively wide range may be desired. In other applications, highly monochromitized radiation is desired. Optics are made with selected technologies to match with the beam requirements while maintain an acceptable cost. X-ray beam systems with excellent performance have been developed with microfocusing sources and variety of beam conditioning optics. Typical focal spot projection of these microfocusing sources is less than 100 micrometers and as small as 10 micrometers. Future development of source technology and optics technology may drive the brilliance even higher and spot size even smaller. Both stability of the spot size and spot position are critical for x-ray beams in analytical applications. In addition to superior performance, microfocusing sources use much less energy therefore has a lower operation cost and cause less environment issues. Sealed tube microfocusing sources, not only offers good performance, but also offers good performance-cost ratio. Representative optics in a microfocusing sources based beam system include multilayer optics, crystal optics, total reflection mirrors, mono-capillary optics and polycapillary optics. Optics can be designed for redirecting x-rays in one direction only, i.e. so-called one-dimensional optics (1D optics), or designed for redirecting x-rays in two perpendicular directions either through single interactions, two interactions or multiple interactions, i.e. so called two-dimensional optics (2D optics). For a highly intense beam, close coupling to an x-ray source is critical in order to acquire a large solid capture angle. To obtain a monochromatic beam, diffraction element should be a key part of the system. Multilayer optics naturally delivers monochromatic beams. The beam characteristics, such as spatial definition, spectrum purity and intensity, can be optimized through various designs. Multilayer optics have been the major beam conditioning optics for x-ray scattering and diffraction. In many analyses, such as in x-ray powder diffraction and thin film analysis, the probe beam is conditioned typically by a one-dimensional optic, meaning to redirect and form a beam in one direction only. These optics include planar multilayer optic, parabolic multilayer optic, and elliptical multilayer optic. These optics have a profile of cylinder curve, i.e. the curvature in the direction perpendicular the beam propagation direction is straight line, and the curvature in the direction of beam propagation direction is a profile of either straight line (planar optic), or part of a parabola (collimating optics), or part of an ellipse (focusing optics). These optics are typically very efficient and are capable in delivering high flux beams. For many other applications, such as single crystal crystallography represented by small molecule crystallography and macro molecule crystallography (protein crystallography), the probe beam has to be a two-dimensional beam, i.e. a “pencil-like” beam formed in two perpendicular directions. Such a beam can be formed by a two-dimensional optic. Multilayer two-dimensional optics are the major beam conditioning optics for the need of two-dimensional beam conditioning. These optics delivers beams with well defined spatial characteristics and good spectrum purity. Optics based on the waveguide principle, such as waveguide bundle optics represented by polycapillary optics, have been used in x-ray micro-spectrometry and selected x-ray diffraction applications. Comparing to multilayer optics, waveguide bundle optics offer much large capture angle and therefore potentially much higher flux and brilliance. The issue with waveguide bundle optics is that the output, in nature, is x-rays with continuous spectrum and is not suitable for x-ray elastic scattering and x-ray diffraction. Being able to analyzing small sample is highly important, whether this is because of a local interest on a large sample or acquiring adequate signal strength from small available sample volume. High flux with well defined spectrum and spatial characteristics is often delivered by a focusing multilayer optic. Such an optic could consist of two cylinder elliptical mirrors; each of the mirrors focuses x-rays in one of the two perpendicular directions and the two mirrors are in a so-called Kirkpatrick-Baez geometry, either in sequential or “side-by-side” arrangement as depicted in U.S. Pat. No. 6,041,099. Such an optic could also be part of an ellipsoid with multilayer coating inside, where a single reflection from the optic directing the x-rays in 2-dimensions. Further improving the intensity of a multilayer focusing optical system depends on close coupling between source and optic. Unfortunately, the coupling distance is limited by the physically feasible dimension of the structure at low d-spacing end. The smallest layer thickness of the man-made layer structure is limited by the size of atoms. At extremely low d-spacing end, such as lower than 10 angstroms, the inter-layer roughness is high; the peak reflectivity is low; and rocking curve is narrow. As it can be seen, none of the solutions discussed above offers efficient coupling with a source and meanwhile provide a beam with controllable and satisfactory spectrum. U.S. Pat. No. 6,504,901 proposed an optical system coupled with a x-ray focusing mirror. But the proposed solution failed to demonstrate that the system will deliver a monochromatic beam and failed to illustrate its efficiency improvement. In fact, the description of the patent leads to a solution which is less efficient and renders an optical scheme without practical significance. The intention seems that using a polycapillary optic to form a small, intense and low divergence “virtual source”, the second optic, being a reflector limited with its capture angle, would be able to take the advantage of a source that is the small, more intense and with a lower divergence, and thus deliver a higher flux. However, from physics law we know, that the first optic, the polycapillary optic, as a kinematical system, i.e. without energy input, will not be able to convert a beam with large divergence into a beam with lower divergence without enlarging the focal spot size of the virtual source. This can also be illustrated by applying thermodynamics to the optical system: the entropy, or the ordering represented by the spot size and divergence, of an isolated system without external energy input will at best be preserved and can not be reduced (or improved in terms of spot size and divergence). The description in U.S. Pat. No. 6,504,901 “polycapillary lens comprises a plurality of tapered capillaries arranged such that both the diameter of the focal spot of an x-ray source and the angular divergence of x-rays are reduced” inevitably results in, in the best case, the same brilliance. Therefore, the performance of the system, in the best case, is equivalent to the performance of the direct coupling between the second optic and the source. The low efficiency of the proposed system in U.S. Pat. No. 6,504,901 could also be illustrated in an geometrical manner, as well. The mechanism of x-ray photons propagation through a single capillary is multiple external total reflection. It occurs in a quite small range of incident angles, which is below 0.3 degrees for the wave length commonly used for diffraction experiments. A collimating waveguide bundle optic, as depicted in FIG. 3, has a smaller cross section at a distance closer to the source. For an x-ray photon propagating inside a capillary, the incident angle at capillary wall gets smaller with each consecutive total reflection. On the other hand, if the optic is a focusing optic, the reflection angle gets smaller at first until the x-ray photons reach the point with largest diameter of the polycapillary optic, then gets larger with each consecutive reflection after passing the point with maximum diameter. When photons reach the exit of the proposed optic in the patent “bottle-shaped” optic where capillary diameter is smaller than at optic entrance, some portion of them will have incident angle larger than critical angle of external total reflection and will be lost, reducing optical system efficiency. In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides an improved x-ray generating system. The x-ray generating system includes a source of x-ray radiation, a waveguide bundle based optic, such as polycapillary optic, for collecting the x-ray radiation produced by the source at large capture angle, a focusing diffractive optic for capturing beam from the first optic and focusing the monochromatic x-ray radiation to a focal point. For avoiding the issues identified previously for the focusing polycapillary optic, the waveguide bundle optic should be designed in such a fashion that it provides a divergent beam, a collimated beam, or a slightly convergent beam. Generally, the focusing optic can be a Kirkpatrick-Baez side-by-side optic having multilayer Bragg x-ray reflecting surfaces that may be either laterally or laterally and depth graded. The focusing reflector can be parabolic, elliptic, and hyperbolic cylinder surfaces. The focusing optic can also be a doubly curved optic, such as paraboloidal, ellipsoidal, hyperboloidal, and toroidal optics, having multilayer Bragg x-ray reflecting surface that may be either laterally or laterally and depth graded. The coupling between the waveguide bundle optic and the diffractive optic is in such a way that the geometric focus of the diffractive optic is at the virtual focus of the waveguide bundle optic or the other way around. If the waveguide bundle optic is a collimating optic, the diffractive optic will be a parabolic or parabloidal optic having its focus at infinite; if the waveguide bundle optic delivers a divergent beam, the diffractive optic will be an elliptical or ellipsoidal optic having its geometric focus at the virtual focus of the divergent beam delivered by the waveguide bundle optic; if the waveguide bundle optic delivers a slightly focused (convergent) beam, the diffractive optic will be hyperbolic and hyperboloidal optic. The x-ray system in accordance with this invention seeks to overcome the previously described design challenges of the prior art by providing a waveguide bundle based optical element closely coupled with an x-ray source which captures x-ray radiation from the source at a large capture angle and directs it to a further diffraction element in a controlled beam size and desired ray configuration. For example, collimated beam configurations can be readily provided. Through the use of suitable additional diffraction optics, such as the previously mentioned Kirkpatrick-Baez multilayer parabolic optic or an paraboloidal optic, a beam with substantially high intensity can be acquired. Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. An x-ray analysis system 10a includes an x-ray source 12, a waveguide bundle optic (such as polycapillary optic) 14, a focusing optic 16a, an aperture 18, a sample 20, and an x-ray detector 22. The x-ray source 12 may be a laboratory source, such as a high brilliance rotating anode x-ray generator or a sealed tube microfocusing source. The x-ray source 12 generally includes an electron beam focusing system 24 and a target 26. Electron beam 28 is guided to the target 26 by the e-beam focusing system 24. The waveguide bundle optic 14 includes an input 30 and an output 32. The input 30 of the waveguide bundle optic is generally located about 3 mm to 15 mm, but not limited to, from the focus of the x-ray source 12. This distance between the input 30 of the waveguide bundle optic 14 and x-ray source 12 is better known as the focal distance. Once x-rays are received by the input 30 of the waveguide bundle optic 14, the waveguide bundle optic 14 guides the x-rays from its input to its output. The x-rays leaving the output 32 of the waveguide bundle optic are divergent, parallel, or slightly convergent. The focusing optic 16a in this embodiment is a Kirkpatrick-Baez side-by-side optic having multilayer Bragg x-ray reflecting surfaces 34 as described in U.S. Pat. No. 6,041,099, which is herein incorporated by reference. The Bragg x-ray reflecting surfaces 34 generally have graded-d spacing that is either lateral or lateral and depth graded. The x-rays 29 received by the Bragg x-ray reflecting surfaces 34 of the focusing optic 16a are then reflected by the Bragg x-ray reflecting surfaces 34 to a focal point 36. The surface shape of the mirrors of the diffractive optic depends on the design of the first waveguide bundle optic. If the first optic provides a divergent beam, the surfaces of the mirrors have an elliptical shape. If the first optic forms a collimating beam, the surfaces of the mirrors have a parabolic shape. If the first optic provides slightly focusing beam, the surfaces of the mirrors have an hyperbolic shape. In any combination, the diffractive optic is positioned in such a way that the virtual focus of one of optics coincides with the real focus of other optic. This condition is critical and provides an effective acceptance by the diffractive optic of all the rays from the waveguide bundle optic. The reflected x-rays by the diffractive optic x-rays 31 are further defined by the aperture 18 in order to remove any unnecessary x-rays. The sample 20 is located adjacent to the focal point 36 and receives the reflected x-rays 31 shaped by the aperture 18. The sample 20 may be any sample, such as a biological sample, a polymer, or a crystallized protein, whose structure is the interest of study. The x-rays altered by the sample are captured by an x-ray detector 22. Referring to FIG. 2, another x-ray generating system 10b is shown. The x-ray generating system 10b is similar to the x-ray generating system 10a in FIG. 1, however, the focusing optic 16b of the x-ray generating system 10b differs from that of the focusing optic 16a of the x-ray generating system 10a. In this embodiment, the focusing optic 16b is a doubly curved optic, such as an ellipsoidal, paraboloidal or hyperboloidal optic, having multilayer Bragg x-ray reflecting surface. Additionally, the multilayer Bragg reflecting surface 35 of the reflecting optic 16b has graded-d spacing that may be laterally graded or laterally and depth graded. Similar to the embodiment shown in FIG. 1, the pre-conditioned x-rays 24 from the output 32 of the waveguide bundle optic, or polycapillary optic, 14 are reflected by the diffractive optic 16b. The reflected x-rays 31 are then focused on a focal point 36. The sample 20 is located near the focal point 36 and is configured to receive the reflected x-rays 31. Thereafter, a detector 22 receives x-rays that have traveled through the sample 20 or are scattered or diffracted by the sample 20. Referring to FIG. 3, a more detailed illustration of the waveguide bundle optic 14, such as a polycapillary optic, is shown. The source 12 emitting the x-rays 28 are separated from the input 30 of the waveguide bundle optic 14 by a distance f, known as the focal distance. As stated previously, the focal distance f is generally between about 3 millimeters to 15 millimeters but not limited to. The waveguide bundle optic 14 includes a plurality of hollow waveguides 40 which are bundled together and plastically shaped into configurations which allow efficient capture of divergent x-rays emerging from the x-ray source 12. In this example, the captured x-rays 28 are shaped by the waveguide bundle optic 14 into the collimated x-rays 29. Channel openings 42 located at the input 30 of the waveguide bundle optic 14 are pointing at the x-ray source 12. The optic could be shorter than shown on the FIG. 3 providing divergent beam, or it could be longer providing a slightly convergent beam. In any of the described embodiments, the diameters of the individual channel openings 42 at the input 30 of the waveguide bundle optic 14 is smaller than the channel diameters at the output 32. Generally, the hollow waveguides, or capillaries, 40 are made of glass and have a diameter ranging from a few micrometers to sub-millimeters. However, the hollow capillaries may be made from carbon nanotubes with even smaller diameter of the channels. As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from the spirit of this invention, as defined in the following claims.
	claims	1. A method for determining a cross sectional dimension of a measured structural element having a sub-micron cross section, the cross sectional dimension defining an intermediate section of the measured structural element that is located between first and second traverse sections of the measured structural element, the method comprising the steps of:scanning, while an inspection tool is in a first tilt state, a reference structural element and at least the first traverse section of the measured structural element, to determine a first distance between a certain point of the reference structural element and the first traverse section, wherein the first traverse section represents a first edge of the measured structural element;determining whether additional scanning is required based on one or more of an estimated width of the first traverse section and an estimated width of the second traverse section;if the additional scanning is required, scanning, while the inspection tool is in a second tilt state, the reference structural element and at least the second traverse section of the measured structural element, to determine a second distance between the certain point of the reference structural element and the second traverse section, wherein the second traverse section represents a second edge of the measured structural element; anddetermining a cross sectional dimension of the intermediate section of the measured structural element in response to at least the first distance, wherein the cross sectional dimension is located between the first and second traverse sections of the measured structural element. 2. The method of claim 1 wherein the first edge of the measured structural element and the certain point of the reference structural element are substantially located on a same plane. 3. The method of claim 1 wherein a height of the certain point of the reference structural element is much smaller than a height of the measured structural element. 4. The method of claim 1 further comprising a preliminary step of generating the reference structural element at a vicinity of the measured structural element. 5. The method of claim 1 wherein during the scanning, while the inspection tool is in the first tilt stage, a measurement angle defined between a measured object that includes the measured structural element and an electron beam that scans the measured structural element is substantially ninety degrees. 6. The method of claim 1 wherein at least one additional reference structural element is provided at a vicinity of the reference structural element and wherein the steps of scanning further comprise scanning the at least one additional reference structural element to provide at least a third distance, in addition to the first and second distances, between the at least one additional reference structural element and a traverse section of the measured structural element. 7. The method of claim 6 wherein the step of determining is further responsive to the third distance. 8. The method of claim 1 wherein performing the scanning, while the inspection tool is in the second tilt state, is in response to determining a feature of the first traverse section. 9. The method of claim 8 wherein the feature is the estimated width or an estimated orientation of the first traverse section. 10. The method of claim 9 wherein the orientation is estimated by comparing detection signals generated as a result of a scan of the first traverse section and detection signals generated as a result of at least one scan of another traverse section of known width. 11. The method of claim 1 wherein at least one additional reference structural element is provided at a vicinity of the reference structural element and wherein the steps of scanning further comprise scanning the at least one additional reference structural element to provide at least a third distance, in addition to the first and second distances, between the at least one additional reference structural element and a traverse section of the measured structural element. 12. The method of claim 11 wherein the step of determining the cross sectional dimension is further responsive to the third distance. 13. A method for determining a cross sectional dimension of a measured structural element having a sub-micron cross section, the cross sectional dimension defining an intermediate section of the measured structural element that is located between first and second traverse sections of the measured structural element, the method comprising the steps of:scanning, while an inspection tool is in a first tilt state, at least a first point of a first reference structural element and at least the first traverse section of the measured structural element, to determine a first distance between the first reference structural element and the first traverse section, wherein the first traverse section represents a first edge of the measured structural element;determining whether additional scanning is required based on one or more of an estimated width of the first traverse section and an estimated width of the second traverse section;if the additional scanning is required, scanning, while the inspection tool is in a second tilt state, at least a second point of a second reference structural element and at least the second traverse section of the measured structural element, to determine a second distance between the second reference structural element and the second traverse section, wherein the second traverse section represents a second edge of the measured structural element; anddetermining a cross sectional dimension of the intermediate section of the measured structural element in response to at least the first distance, wherein the cross sectional dimension is located between the first and second traverse sections of the measured structural element. 14. The method of claim 13 wherein the measured structural element is positioned between the first and second reference structural elements. 15. The method of claim 13 further comprising a step of measuring a distance between the first and second points. 16. The method of claim 15 wherein the measured structural element is positioned between the first and second reference structural elements and wherein the step of measuring the distance comprises performing at least one scan of the first and second points and the measured structural element. 17. The method of claim 16 wherein the at least one scan comprises preventing an electron beam from illuminating the measured structural element. 18. The method of claim 13 wherein the measured structural element is a line that has a top section and two substantially opposing sidewalls. 19. The method of claim 13 wherein the measured structural element is a contact. 20. The method of claim 13 wherein the measured structural element is a recess. 21. The method of claim 13 wherein at least one additional reference structural element is provided at a vicinity of the first and second reference structural elements and wherein the steps of scanning further comprise scanning the at least one additional reference structural element to provide a third distance, in addition to the first and second distances, between the at least one additional reference structural element and a traverse section of the measured structural element. 22. The method of claim 21 wherein the step of determining the cross sectional dimension is further responsive to the third distance. 23. The method of claim 13 wherein the scanning, while the inspection tool is in the first tilt stage, comprises scanning with an electron beam that is substantially perpendicular to a measured object that includes the measured structural element. 24. The method of claim 13 wherein the determination of whether additional scanning is required is further based on an estimated orientation of a traverse section. 25. The method of claim 13 wherein the determination of whether additional scanning is required is further based on an estimated cross sectional dimension of the measured structural element. 26. The method of claim 13 wherein the determination of whether additional scanning is required is further based on relationship between a threshold and an estimated cross sectional dimension of the measured structural element. 27. The method of claim 26 wherein the threshold is a maximal width of the measured structural element. 28. The method of claim 26 wherein the threshold is a minimal width of the measured structural element. 29. The method of claim 13 wherein at least one additional reference structural element is provided at a vicinity of the first and second reference structural elements and wherein the steps of scanning further comprise scanning the at least one additional reference structural element to provide a third distance, in addition to the first and second distances, between the at least one additional reference structural element and a traverse section of the measured structural element. 30. The method of claim 29 wherein the step of determining the cross sectional dimension is further responsive to the third distance. 31. A method for determining a cross sectional dimension of a measured structural element having a sub-micron cross section, the cross sectional dimension defining an intermediate section of the measured structural element that is located between first and second traverse sections of the measured structural element, the method comprising the steps of:scanning, while an inspection tool is in a first tilt state, first portions of a set of reference structural elements and at least the first traverse section of the measured structural element, to determine a first set of distances between first certain points of reference structural elements of the set of reference structural elements and the first traverse section, wherein the first traverse section represents a first edge of the measured structural element;determining whether additional scanning is required based on one or more of an estimated width of the first traverse section and an estimated width of the second traverse section,if the additional scanning is required, scanning, while the inspection tool is in a second tilt state, second portions of the set of reference structural elements and at least the second traverse section of the measured structural element, to determine a second set of distances between second certain points of reference structural elements of the set of reference structural elements and the second traverse section, wherein the second traverse section represents a second edge of the measured structural element; anddetermining a cross sectional dimension of the intermediate section of the measured structural element in response to at least the first set of distances, wherein the cross sectional dimension is located between the first and second traverse sections of the measured structural element. 32. The method of claim 31 wherein the step of determining comprises statistical processing of the distances of the first set to provide a first distance. 33. The method of claim 31 wherein the step of determining comprises statistical processing of the distances of the second set to provide a second distance. 34. The method of claim 31 wherein the set of reference structural elements is positioned at both sides of the measured structural element. 35. The method of claim 31 wherein the set of reference structural elements is positioned at one side of the measured structural element. 36. A system for determining a cross sectional dimension of a structural element having a sub-micron cross section, the cross sectional dimension defining an intermediate section that is located between first and second traverse sections of the structural element, wherein the first traverse section represents a first edge of the measured structural element and the second traverse section represents a second edge of the measured structural element, the system comprising:means for directing an electron beam towards an inspected object including the measured structural element so as to scan, at a first tilt state, a reference structural element and at least the first traverse section of the structural element, and to scan ata second tilt state, the reference structural element and at least the second traverse section of the structural element;at least one detector that is positioned so as to detect electrons emitted from the measured structural element as a result of an interaction with the electron beam; anda processor, coupled to the at least one detector and to the directing means so as to process detection signals received from the at least one detector and to:determine whether additional scanning after the scan at the first tilt state is required based on one or more of an estimated width of the first traverse section and an estimated width of the second traverse section;determine a first distance between a certain point of the reference.structural element and the first traverse section;if scanning at the second tilt state is performed, determine a second distance between the certain point of the reference structural element and the second traverse section; anddetermine a cross sectional dimension of the intermediate section of the measured structural element in response to at least the first distance, wherein the cross sectional dimension is located between the first and second traverse sections of the measured structural element. 37. The system of claim 36 wherein the processor is capable of determining the cross sectional dimension in response to additional distances between the measured structural element and additional reference structural elements.
	claims	1. A nuclear reactor comprising:a reactor pressure vessel;a cylindrical core barrel supported within and spaced from an interior of the reactor pressure vessel and having a central axis substantially coaxially aligned with a central axis of the pressure vessel;a nuclear core comprising a plurality of fuel assemblies forming a fuel assembly array is supported between a lower core plate and an upper core plate, within and spaced from the core barrel;a shroud is supported between the core barrel and the fuel assembly array, having in part an outer contour that substantially matches an inner contour of the core barrel and an inner contour that substantially matches an outer contour of the fuel assembly array and a hollow interior portion;a neutron reflector positioned within the hollow interior portion of the shroud comprising a closely packed array of elongated rods with an elongated dimension extending in the axial direction and;wherein the shroud comprises former plates which extend from an inner surface of the core barrel, in a substantially tandem, parallel array at a plurality of spaced elevations and baffle plates which extend axially between the spaced elevations of the former plates and substantially form the inner contour of the shroud, wherein the elongated rods of the neutron reflector extend axially between the former plates and in between the baffle plates and the core barrel and a number of the former plates at an intermediate elevation comprise two former plates stacked back to back. 2. The nuclear reactor of claim 1 wherein the elongated rods are attached at a first and second end to radially adjacent ones of the elongated rods by the former plates. 3. The nuclear reactor of claim 2 wherein the first and second ends of the elongated rods have a reduced diameter relative to a central axial portion of the elongated rods. 4. The nuclear reactor of claim 3 wherein the reduced diameter of the first and second ends of the elongated rods respectively fit into a corresponding openings in the former plates. 5. The nuclear reactor of claim 4 wherein the elongated rods have a substantially round cross-section and are closely packed to contact each of an adjacent rod along an axial extent around a portion of a circumference of the adjacent rod and to be spaced from the adjacent rod around another portion of the circumference of the adjacent rod to form a coolant channel axially along the another portion of the adjacent rod. 6. The nuclear reactor of claim 5 including flow holes in the former plates that align with the coolant channel. 7. The nuclear reactor of claim 6 wherein a transition between the first and second ends and a central portion of at least some of the elongated rods is formed as a bevel and the diameter of at least some of the flow holes in the former plates adjacent the at least some of the elongated rods with the bevel is larger than the narrowest diameter of the corresponding coolant channels. 8. The nuclear reactor of claim 4 wherein the first and second ends of the elongated rods are respectively attached to the former plates at an edge of the corresponding openings in the former plates. 9. The nuclear reactor of claim 8 wherein the first and second ends of the elongated rods are welded to the former plates at the edge of the corresponding openings in the former plates. 10. The nuclear reactor of claim 8 wherein at least some of the elongated rods at a lower most elevation that extend between some of the former plates are axially aligned with other elongated rods which extend between the former plates at elevations above the elongated rods at the lower most elevation. 11. The nuclear reactor of claim 10 wherein the aligned elongated rods extend between at least five of the tandemly spaced former plates with an upper former plate immediately above the aligned elongated rods and a lower former plate immediately below the aligned elongated rods having one thickness and the number of the former plates in the tandem array at the intermediate elevations that are stacked back to back have a combined thickness of approximately twice the one thickness. 12. The nuclear reactor of claim 1 wherein the neutron reflector comprises a number of axially stacked elongated rod modules with each module comprising a plurality of elongated rod segments supported at opposing ends by a former plate. 13. The nuclear reactor of claim 2 wherein the elongated rods between adjacent former plates form a separable neutron reflector module. 14. The nuclear reactor of claim 1 wherein the elongated rods extend from a lower former plate to an upper former plate wherein the lower former plate is spaced above the lower core support plate on which the fuel assemblies are supported and the upper former plate is spaced from the upper core plate that restrains the fuel assemblies, with the space between the upper core plate and the upper former plate forming an upper coolant plenum having a first orifice in fluid communication with one of either a reactor coolant path on route to traversing the core or a reactor coolant path exiting the reactor core and the space between the lower core support plate and the lower former plate forming a lower coolant plenum having a second orifice in fluid communication with the other of the reactor coolant path on route to traversing the core or the reactor coolant path exiting the reactor core, so that coolant to cool the reflector enters from one of the upper coolant plenum or the lower coolant plenum, passes through the former plates around the elongated rods and into the other of the upper coolant plenum or the lower coolant plenum and exits to rejoin a main coolant flow path. 15. The nuclear reactor of claim 1 wherein the elongated rods are supported on a triangular pitch. 16. The nuclear reactor of claim 1 wherein the elongated rods are supported on a rectangular pitch. 17. The nuclear reactor of claim 1 wherein the former plates are formed in a plurality of circumferential sections extending around the circumference of the core. 18. The nuclear reactor of claim 17 wherein the former plates are formed in at least eight circumferential sections. 19. The nuclear reactor of claim 1 wherein at least some of the elongated rods extend in a continuous extent between a very top and a very bottom former plate. 20. The nuclear reactor of claim 19 wherein not all of the elongated rods extend in the continuous extent between the very top and the very bottom former plates.
051951215	summary	BACKGROUND OF THE INVENTION a) Field of the Invention The present invention broadly relates to an apparatus for modulating the intensity of an X-ray beam generated in a given direction by an X-ray tube. More specifically, the invention relates to an apparatus of the above mentioned type, hereinafter called "X-ray beam modulator", that is motorized, remotely controlled and easy to operate, thereby making it easy to use into the X-ray cone and tube assembly of a radiographic system, such as, for example, a system for lower limb angiography, in order to obtain better density and contrast and less radiation exposure of the patient's legs and feet. b) Brief Description of the Prior Art It is well known that the X-ray absorption of a body depends on the thickness and/or density of this body. Thus, in a human being, the X-ray absorption varies substantially according to both the portion of the anatomy to be radiographed, and the specific body feature of the patient who is radiographed, depending on the thickness of his or her bones and his or her weight. Accordingly, there is a need for an apparatus for modulating the intensity of the X-ray beam projected towards a patient, depending on the portion of his or her anatomy to be radiographed and his or her physical condition, in order to achieve proper density and contrast over the entire radiographic film without unduly overexposing some portion of the patient's body. So far, such a need has been fulfilled with filters of different absorption rates that must be selected and positioned to intersect the X-ray beam according to the radiographic need. Such filters are of course very efficient, but time consuming to install. SUMMARY OF THE INVENTION The object of the present invention is to provide an X-ray beam modulator which is simple in structure and very easy to use and remotely control and which can be very easily incorporated into an X-ray cone and tube assembly of conventional structure and used with all kinds of screens and films, in order to vary the intensity of irradiation on some parts of the patients' body such as his or her legs and feet in the case of lower limb angiography, and to generate different compensation curves according to the patient's anatomy. In accordance with the invention, this object is achieved with an apparatus comprising: a rotor having a rotation axis parallel to the direction of the X-ray beam, the rotor being positioned adjacent this X-ray beam; means to drive the rotor about its rotation axis at variable speeds; a set of at least three blades made of a material opaque to X-ray, each of the blades comprising a central hub and a pair of symmetrical wings extending away from the hub, the blades of the set having their hubs slidably mounted on a corresponding set of radially projecting shafts symmetrically fixed to and about the rotor; return spring means to urge each of the blades radially inwardly towards the rotor along their respective shafts; and guiding means on each pair of hub and shaft to cause the corresponding blade to pivot about the shaft on which it is mounted when the speed of the rotor increases and the blades are then moved in unison radially outwardly against the action of the return spring means as a result of the centrifugal force. The blades and their shafts are sized to cause the blades to intersect the X-ray beam when the rotor is driven, and then modulate the intensity of the X-ray beam as a function of the angular position of the blades about their shafts, which allow more or less radiation to pass therebetween. Advantageously, the apparatus may further comprises programmable control means operatively connected to the means to drive the rotor in order to allow preselection of at least one given speed of rotation of the rotor corresponding to a required compensation curve. The invention and its advantages will be better understood upon rading the following, non-restrictive description of a preferred embodiment thereof, given with reference to the accompanying drawings.
	summary

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