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description | This application claims priority to Provisional Application Ser. No. 61/561,974, filed Nov. 21, 2011, and is related to patent application Ser. No. 13/612,905, filed Sep. 13, 2012 (now issued U.S. Pat. No. 8,857,027, issued Oct. 14, 2014), entitled METHOD OF SEGMENTING IRRADIATED BOILING WATER REACTOR CONTROL ROD BLADES, filed concurrently herewith. 1. Field This invention relates generally to the storage, transportation and disposal of highly radioactive components, and, more particularly to apparatus for vertically segmenting a boiling water reactor control rod blade to facilitate storage and/or transportation. 2. Description of Related Art One type of commonly used boiling water nuclear reactor employs a nuclear fuel assembly comprised of fuel rods surrounded by a fuel channel. Each fuel channel of a boiling water reactor typically consists of a hollow, linear, elongated, four-sided channel of integral construction, which except for its rounded corner edges, has a substantially square cross section. Commonly, each channel is roughly 14 feet (4.27 meters) long by five inches (12.7 cms.) square and laterally encloses a plurality of elongated fuel elements. The fuel elements are arranged to allow for the insertion of a cruciform shaped control rod, which, during reactor operation, is movable vertically to control the nuclear reaction. As is generally known, the control rods come in a number of similar shapes, e.g., an American version, a Nordic version and a German version, and generally include an upper portion having a handle and four upper ball rollers for guiding the upper portion of the control rod as it moves vertically and a lower portion comprising a lower casting that in at least one of the versions functions as a velocity limiter and lower ball rollers that serve as a lower guide for the vertical movement. The main body structure, between the upper and lower portions, includes four blades or panels which extend radially from a central spline. Preferably, the blades extend longitudinally to at least a height that substantially equals the height of the fuel elements, which is approximately 12 feet (3.66 meters). The width of the control rods at the blade section is approximately twice the width of the panels, which is in the order of 10 inches (25.4 cms.) and the blades are approximately 2.8 inches (7 mils.) thick. Following functional service, boiling water reactor control rod blades are difficult to store and dispose of because of their size, configuration, embrittled condition, and radiological activity. Heretofore within the United States, in-pool storage of control rod blades has been extremely space inefficient and dry cask storage is not readily available. The control rod design may vary with the manufacturer, but the four-panel design with the panels radially extending from a central spline at 90° intervals around the circumference of the control rod is common to all of the boiling water reactor designs, and thus, a common storage problem. Control rod blades and other irradiated hardware are typically Class C low level radioactive waste as defined and determined pursuant to 10 CFR §61 and related regulatory guidance e.g., NRC's Branch Technical Position on Concentration Averaging and Encapsulation. Since Jul. 1, 2008, low level radioactive waste generators within the United States that are located outside of the Atlantic Compact (Connecticut, New Jersey and South Carolina) have not had access to Class B or Class C, low level radioactive waste disposal capacity. Lack of disposal capacity has caused boiling water reactor operators considerable spent fuel pool overcrowding. Though currently very uncertain and subject to numerous regulatory and commercial challenges Class B and Class C, low level radioactive waste disposal capacity for the remainder of the United States low level radioactive waste generators is anticipated in the relatively near future. One technique for reducing the volume of boiling water reactor control rods for spent fuel pool storage has been to sever the upper and lower portions of the control rods from the control rods' blades. In the remaining main blade structure, the individual blade sections have been removed from the central spline by longitudinal cuts and the severed parts are then stacked for storage or burial as described in U.S. Pat. No. 4,507,840. This type of process requires three approximately 4 meter long cuts with handling time in between that makes this an arduous process. The packing of the segmented blades is also inefficient leading to high customer costs. An alternate approach has been taken in U.S. Pat. No. 5,055,236, which suggests that a vertical cut be made along the center line of the spline to divide the control rod blades into two chevrons. The chevrons can then be closely stacked for storage. Each of the approaches yields 12-foot (3.6 meters) or longer segments that are costly to shield and transport. U.S. Pat. No. 4,507,840 recognizes that since the blades enclose neutron absorber rods, which contain radioactive gas, the vertical cuts must be made quite near the central spline to avoid releasing the radioactive gases. Thus, horizontal segmentation of the blades, which would cut across the sealed rods that contain the neutron absorber material and the radioactive gases, while making the handling of the blades more manageable, is problematic. Copending patent application Ser. No. 13/612,905, filed Sep. 13, 2012, now issued U.S. Pat. No. 8,857,027, issued Oct. 14, 2014, overcomes this difficulty, but first requires a convenient way to the vertically segment the blades into four flat panels. Therefore, for safe and cost effective shipment and storage of a spent boiling water reactor control rod a new apparatus is desired for vertically segmenting the control rod blades in an efficient manner to make the blades more amenable to further lateral segmentation to reduce the storage volume of the component to a manageable size that can be packaged in a dry cask. Additionally, such an apparatus is desired that will minimize the release of radioactive debris in segmenting a boiling water reactor control rod. These and other objects are achieved by the apparatus claimed hereafter for reducing the storage volume of a boiling water reactor control rod by simultaneously, vertically severing the control rod spline along a central axis extending along an elongated dimension of the spline, into four substantially equal sections without cutting through the blade panels. In one preferred embodiment, the apparatus is a double bladed band saw having a tool base plate including a first pair of spaced pulley wheels rotably supported from one side of the tool base plate. One of the first pair of spaced pulley wheels includes a drive wheel that is operatively connected to a motor to rotate the drive wheel when the motor is in an on state. A second of the first pair of spaced pulley wheels is oriented along a first axis extending between the drive wheel and the second of the first pair of spaced pulley wheels. A first band saw blade extends around the drive wheel and the second of the first pair of spaced pulley wheels. A first side of the first band saw blade extends between the drive wheel and the second of the first pair of spaced pulley wheels and around the second of the first pair of spaced pulley wheels. A second side of the first band saw blade extends between the second of the first pair of spaced pulley wheels and the drive wheel and around the drive wheel. Furthermore, the first side of the first band saw blade extends over a first opening in the tool base plate that is sized for the boiling water reactor control rod to axially pass therethrough in a direction of the central axis. A second pair of spaced pulley wheels is vertically supported from the one side of the tool base plate with one of the second pair of spaced pulley wheels comprising a follower wheel that is operably connected to the drive wheel to rotate the follower wheel when the motor is in an on state. A second of the second pair of spaced pulley wheels is oriented along a second axis extending between the follower wheel and the second of the second pair of spaced pulley wheels with the second axis being oriented at a fixed angle greater or less than zero relative to the first axis. A second band saw blade extends around the follower wheel and the second of the second pair of spaced pulley wheels with a first side of the second band saw blade extending between the follower wheel and the second of the second pair of spaced pulley wheels and around the second of the second pair of spaced pulley wheels. A second side of the second band saw blade extends between the second of the second pair of spaced pulley wheels and around the follower wheel wherein the first side of the second band saw blade extends over the first opening in the tool base plate that is sized for the boiling water reactor control rod to pass therethrough. In one embodiment, the follower wheel is connected to the drive wheel with a chain and sprocket coupling. Preferably, the drive wheel and the follower wheel respectively drive the first and second band saw blades at approximately the same speed. Desirably, the first side of the first band saw blade and the first side of the second band saw blade cross one another over the central axis of the spline when the boiling water reactor control rod is positioned in the first opening in the tool base plate. In one preferred embodiment, the first opening in the tool base plate includes guide supports to contact and guide each side of the panels of the control rod through the first opening in the tool base plate when the boiling water reactor control rod panels extend through the opening. Preferably, the guide supports extend on either side of the first opening in the tool base plate and in one embodiment the guide supports are wheels positioned on either side of each panel and supported at different elevations relative to the central axis. Desirably, the different elevations are approximately 50 millimeters apart. The tool base plate may also include an attachment interface that is connectable to a guide post or rail that extends in a direction parallel to the central axis when the boiling water reactor control rod panels extend through the first opening. Means are provided for moving the tool base plate along the guide post or rail in a direction parallel to the central axis. Preferably, the means for moving the tool base plate is an overhead crane and the guide post or rail is either supported from the bottom of the spent fuel pool or from the reactor building floor where it extends into the pool at least six meters. In another preferred embodiment, the first and second band saw blades operate to substantially simultaneously cut the boiling water reactor control rod vertically along the spline dividing the boiling water reactor control rod spline into four substantially equal sections. Desirably, when in an upper position above the boiling water reactor control rod, the tool can be rotated 180° to facilitate maintenance. In a further embodiment, the motor may be a hydraulic motor and the tool base plate preferably is outfitted with a camera, or more preferably a plurality of cameras for observing and managing the cutting process. Desirably, the fixed angle is approximately 90°. FIG. 1 shows a boiling water reactor control rod blade 13 of the type to which the present invention is applicable. As such, the control rod blade comprises an upper portion 11 having an upper handle 10 and four upper ball rollers 12; a lower portion 14 having a lower casting 15 and lower ball rollers 17; and a main blade structure 16 therebetween. The main blade structure 16 includes four panels or blades 18 arranged in a cruciform shape about a central spline 20. According to one embodiment of the invention, the lower portion 14 is removed by cutting approximately in the plane defined by lines m and n, and the upper portion 11 is removed by cutting in a transverse plane defined by lines j and k. Another alternative is to just cut around the rollers to remove them or to leave the handle 10 in place. Although it is possible to practice the invention without removing the rollers, it is desirable to do so since they typically contain cobalt and from a radiological perspective, are reactively much hotter than the other portions of the control rod blade. For the general purposes of this description, the principal components of a control rod blade are an upper portion containing the lifting handle 10 and the stellite rollers 12, a lower portion 14 containing the velocity limiter 19 and stellite rollers 17 and the central portion containing the cruciform shaped main body 16 including the blades or panels 18 and the central spline 20. To consolidate the control rod blade section 16 the upper portion 11 and the lower portion 14 are first removed in a manner consistent with existing art as part of a control rod blade volume reduction process. The cruciform shaped main body 16 is comprised of four sheathed metallic “panels” 18 of metallic tubes containing powdered boron carbide or other neutron absorbing material that are welded together and to the central spline 20 lengthwise at opposing angles to form the cruciform shape. Because of the radioactive nature of the control rod, it is necessary for the volume reduction process to be performed under water, most preferably in the spent fuel pool. To separate the control rod into practically transportable segments or segments that can be more efficiently stored in a spent fuel pool, it will be necessary to longitudinally segment the main body portion 16 so that the panels 18 can be stacked or further, laterally segmented so they can fit into casks for transport. However, under water lateral segmentation of the panels 18 will rupture both the sheathing and the tubes contained within the sheathing of the panels 18 thereby exposing the spent fuel pool to unwanted debris in the form of sheathing material, tubes and boron carbide. Embrittlement of the control rod blades caused by the extended neutron exposure that they will have experienced within the reactor compounds the difficulty of the segmentation process. One prior art method employed to reduce the volume of the control rod blades for storage includes the mechanical longitudinal segmentation of the control rod blade cruciform shape main body 16 through the center spline 20 resulting in two chevron shaped sections as described in U.S. Pat. No. 5,055,236. Segmentation in this fashion substantially improves the in-pool storage efficiency, but does not lend the chevrons to a practical form for transportation to a remote site for storage or for lateral segmentation. One aspect of the device described herein is to further longitudinally segment each chevron along the remaining portion of the spline 20 thereby resulting in four separate detached panels 18. This subsequent segmentation will improve in-pool storage efficiency, and substantially facilitate the lateral panel segmentation process that will facilitate containerization and optimal radiological characterization for purpose of shipment and disposal. The embodiment described herein provides a double bladed band saw for efficiently dividing the main body portion 16 into four separate panels 18 that do not require further processing after a long longitudinal cut is made through the spline 20 in a single pass. Also, only one four meter long cut is required. The apparatus described hereafter to segment the cruciform blades into four, four-meter long flat panels 18 will facilitate a large space reduction for further backend handling and storage. Cutting and handling time on site will be reduced significantly with this device. A precise cut through the spline 20 of the control rod with the two band saw blades is made so that the boron (or other neutron absorbing material) content of the control rod blades stays intact without leakage to the spent fuel pool water. In accordance with this embodiment, the control rod to be cut is positioned (with the on-site refueling machine) in a submerged cutting position (in the spent fuel pool or reactor internals pool). The bottom part of the control rod, the velocity limiter 19 with the stellite rollers 17 and the stellite rollers 12 at the top of the control rod are preferably first removed. The main blade structure 16 and what remains of the upper portion 11 is then preferably supported from the bottom of the pool. Two cuts, 90° apart are then substantially simultaneous made down the center of the spline to separate the control rod blade into four panels 18. As shown in FIGS. 2 and 3, which illustrates one preferred embodiment of this invention, a new band saw 21 is provided which can be used to obtain the simultaneous cut of the spline 20, previously described. The band saw 21 comprises a base plate 22 that is attached to a hoist rail 23 (shown in phantom in FIG. 3). The attachment of the tool base plate to the rail 23 can take any one of several forms, but as shown in FIG. 3 it includes a vertically oriented attachment plate 37 which is affixed at right angles to the tool base plate 22 and reinforced by gussets 38. The attachment plate 37 is connected, e.g., bolted, to a travel carriage 42 which rides on the guide rail 23. The guide rail 23, in the cutting position extends from either the containment floor to about six meters down into the spent fuel pool or from the bottom of the spent fuel pool to a height of at least four meters. The hoist which can be an overhead crane, feeds the band saw 21 downwards along the hoist rail 23 during the cutting operation. At the uppermost position, the band saw 21 can be rotated 180° to facilitate maintenance work. The band saw 21 has two blades 33 and 34, with the teeth on each blade oriented in the downward direction, and has two wheels or pulleys associated with each band saw blade; a drive wheel 24 and first adjustable guide wheel 25 associated with the band saw blade 33 and a follower wheel 26 and second adjustable guide wheel 27 associated with the band saw blade 34. Band saw blade 33 is wrapped around the drive wheel 24 and extends between the drive wheel 24 and the first guide wheel 25, while band saw blade 34 is wrapped around the follower wheel 26 and extends between the follower wheel 26 and the second guide wheel or pulley 27. Each set of pulley wheels, i.e., 24 and 25, and 26 and 27, is located at a different height level above the base plate 22 (approximately 50 millimeters apart). The hydraulic motor 28 is located under the tool base plate 22, with a drive shaft that extends through the base plate and is mechanically connected, either directly or indirectly, to drive the drive wheel 24 and, thus, the blade 33. A chain 29 on gear wheel or sprocket 35 on the drive shaft of the motor 28 connects to the follower wheel 26 and creates propulsion for the other blade 34. The blades are preferably located 90° apart from each other and as shown in FIG. 8 and rotate at the same speed. Top guide rollers 30 on the upper surface of the band saw base plate 22 guide the control rod blades 18 through the precision cut across the center of the spline 20 of the control rod 13. Similarly, lower control rod guides 39, which are shown in FIG. 7 and in greater detail in FIG. 6, guide and positively support the control rod blades as they are fed through the cruciform opening 31 in the base plate 22. A spring tensioned roller ball 41 on each of the four lower guides positively grips the control rod blades 18 as they are fed through the opening 31 in the base plate 22. The band saw blades 33 and 34 cross over the opening 31 in the base plate 22 through which the control rod 13 passes and makes two orthogonal cuts in the spline centered between adjacent panels to separate the spline into four substantially equal, separate pieces, with each piece connected to a panel 18 as shown in FIG. 9. As can be appreciated from FIG. 4 the saw band guides 36, through which the saw blades extend, as can best be seen in FIGS. 2 and 8, assure the blades are properly centered over the spline 20 and cameras 32 provide the option of viewing the operation remotely. As shown in FIG. 5, tensioners 40 on the underside of the base plate 22 place a positive radial outward force on the shafts on which the first and second adjustable pulley wheels 25 and 27 turn, to assure adequate tension is maintained on the saw bands 33 and 34. Accordingly, after the control rod 13 is secured at the bottom of the pool the double bladed band saw 21 is attached to the vertical rail 23 and a feeding system, such as an overhead hoist, moves the double bladed band saw downwards as the motor 28 rotates the blades 33 and 34. The lower control rod guides 39 (as shown in FIG. 7) guide the top of the control rod 13 to the right position and the spring tensioned roller ball 41 positively grip the blades 18 to align and feed the blades through the opening 31. The double bladed band saw 21 is lowered until the lowest blade 34 reaches the control rod top handle, where the handle has not been previously cut off, as mentioned above. The handle 10, or the top of the spline 20, as the case may be, is first cut by the bottom blade 34 and secondly by the top blade 33. The double bladed band saw band guides 36 guide the cut to be performed exactly at the center of the control rod. The vertical feeding along the rail 23 moves the double bladed band saw 21 downwards until the control rod center cut is complete. The upper roller guides 30 hold the control rod blades 18 firmly so no vibration occurs during the sawing process. The double bladed band saw provides for significantly lower cutting and handling times on site and simplifies handling of the cut control rod blades. Additionally, the doubled bladed band saw keeps a clean environment in the pool and provides for precise segmentation which increases the packing efficiency in the expensive storage containers. Furthermore, this tool provides full control of the process that can be easily monitored with submerged cameras 32 for plant safety. 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 general concepts disclosed and any and all equivalents thereof. |
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046831029 | description | DETAILED DESCRIPTION FIG. 1a shows the lower part of the first control shaft 2 arranged inside a leakproof enclosure 1 fixed, integrally to the cover of the nuclear reactor vessel, (not shown), and communicating with the internal volume of this vessel. The second control shaft 3 is arranged inside the tubular control shaft 20 coaxially with the latter and with regard to the enclosure 1, as can be seen in FIGS. 1a and 1b. The control shaft 2 is joined at its lower end to the pommel 4 of the control rod through the intermediary of a device 5, while the second control shaft 3 is joined to the pommel 6 of the cluster of fertile elements through the intermediary of a device 7. The fixing devices 5 and 7 have been described in U.S. Pat. No. 4,544,521. The tubular control shaft 2 comprises a reduced diameter zone 10 of very short length relative to the overall length of the control shaft 2. This reduced diameter part 10 is separated from the part of the internal cylindrical space of the first control shaft which is situated above it by a frusto-conical surface 10a. This reduced diameter zone 10 has a length which is close to 15 cm while the control shaft 2 has a length greater than 4 meters. This zone 10 is situated in the lower part of the control shaft 2 whose outer surface is machined to produce successive annular grooves 12 spaced equally over this control shaft. In a conventional manner, the leakproof enclosure 1 carries an electromagnetic unit 14 comprising three windings and two ratchet units 15 and 16 intended to cooperate by means of their teeth with the grooves of the first control shaft for moving the latter in the vertical direction. In its upper part, the first control shaft 2 carries pivoting fingers 18 for hooking the second control shaft 3. A mantle 19 enables these pivoting fingers to be actuated for their opening when the control shaft 2 comes into a high overrun position inside the leakproof enclosure 1. The mantle 19 then comes to rest on a shoulder 20 in the upper part of this leakproof enclosure to be actuated and for the opening maneuver of the fingers 18. The second control shaft 3 comprises a widened part 22 carrying sealing segments 23 and forming a piston for the withdrawal by upward movement of the cluster of fertile elements fixed to the lower part of the second control shaft 3. The leakproof enclosure is joined at its upper part to a low-pressure circuit 24 comprising a control valve 25. In FIGS. 1a and 1b, the control shafts 2 and 3 are shown in their low position, the second control shaft 3 remaining in this low position during the entire first phase of the operating cycle of the reactor. At the end of the first phase of the reactor cycle, all the shafts 2 joined to the control rods in the reactor are brought into high position in the corresponding leakproof enclosures 1. At the end of this upward movement of the control shaft 2, the mantle 19 comes to rest against the shoulder 20 and the upper part of the control shaft 2 above the mantle 19 engages in the upper channel 27 of the leakproof enclosure. In this position, the low-pressure circuit 24 communicates directly with the inner cylindrical space of the control shaft 2. The grooves in the control shaft 2 are designed so that it is still possible for the control shaft 2 to execute a slight upward overrun with an amplitude of a few steps. In the course of this high overrun of the control shaft 2, the mantle 19 actuates the fingers 18 in the opening direction. The position of the reduced diameter zone 10 of the control shaft 2 is chosen so that this reduced diameter zone comes into a position around the piston 22 of the control shaft 3 which is still in a low position, during the high overrun of the control shaft 2. The segments 23, which are radially expandable segments whose diameter in an unstressed state is close to the internal diameter of the zone 10 of the control shaft 2, then ensure an insulation between the part of the inner cylindrical space of the control shaft 2 situated above the piston 22 and the part of this inner cylindrical space situated below the piston 22. The operating device is now ready for the lifting of the control shaft 3 and of the cluster of fertile elements. For this purpose, the valve 25 is opened, producing a significant pressure reduction in the channel 27 and in the inner cylindrical space of the control shaft 2 above the piston 22. This pressure reduction is not produced below the piston 22 because the segments 23 provide a seal or at least a considerable pressure drop in the inner cylindrical space of the control shaft 2. The difference in pressure on either side of the piston 22 causes the lifting of the control shaft 3 inside the control shaft 2, the segments 23 having sufficient radial expansion to permit them to be applied against the inner surface of the cylindrical space of the control shaft 2 when they leave the reduced diameter zone 10 after the leaktight sealing has been initiated by introducing these joints into the reduced diameter zone. We shall describe hereinbelow how these segments 23 can be produced to ensure sealing both in the reduced diameter zone and in the large diameter zone of the inner space of the control shaft 2. The control shaft 3 rises inside the control shaft 2 until an end stop permits it to stop so that a groove machined in the control shaft 3 for engaging the fingers 18 is in a position of facing the fingers 18. A slight downward movement of the control shaft 2 then permits the fingers to close and to unite the shafts 2 and 3. During the movements of the control rod which is united with the control shaft 2, when the second control shaft 3 is in a low position as shown in FIG. 1a and 1b, the piston 22 and the joints 23 remain in the region of the large dimaeter zone of the internal space of the control shaft 2. The clearance between the segments 23 and the inner surface of the control rod 2 makes it possible to effect movements of the control rod without any rubbing between the segments 23 and the inner surface of the control shaft 2. This clearance is of the same order of magnitude as the difference between the diameter of the large diameter part or running part of the inner space of the control shaft 2 and the inner diameter of the reduced diameter zone 10. This clearance of this difference in diameter can be between a few tenths of a millimeter and three millimeters, and is preferably between 5/10 of a millimeter and 3 mm. The diameter of the segments 23 in an unstressed state can be very slightly greater than the diameter of the zone 10, the entry of these joints 23 into the zone 10 at the end of the upward movement of the control shaft 2 then taking place with a slight rubbing and a slight contraction of the segments 23 which then ensure a very good seal on either side of the piston 22. These segments 23 can also have a diameter which is slightly smaller than the diameter of the zone 10, and the pressure difference on either side of the piston 22 will then be provided by the high pressure drop in the space between the segments 3 and the inner surface of the zone 10. In all cases, the radial expansion of the joints by a pressure differences may have been initiated by the piston 22 crossing into the zone 10. The movements of the control rod will take place without wear of the segments 23 and without the control shaft 3 being dragged by the control shaft 2. A wearing component 29 which protects the segments 23 against radial impacts is arranged at the periphery of the piston 22, above the upper segment 23b. A description will now be given, with reference to FIGS. 2 to 7, of radial expansion joints which can be employed to ensure the leaktight sealing of a piston of an operating device according to the invention. FIGS. 2a, 2b and 2c show three types of section produced in a conventional manner on radial expansion segments consisting of a ring with a square or rectangular cross-section, which is not closed and has some elasticity. When the segment is in an unstressed state, the two ends of the section are not in contact. A segment comprising a single ring having a section 30 with a straight edge as shown in FIG. 2a produces considerable leakage. The section 31 shown in FIG. 2b which has an overlap produces a smaller leakage, and that shown in FIG. 2c produces a very low leakage but the production of such joints 32 is much more difficult. The joints of the kind shown in FIGS. 2a, 2b and 2c can be employed to form radial expansion joints 23 associated with a piston 22 of an operating device according to the invention. FIGS. 3a, 3b and 3c show an embodiment of a piston 22 according to the invention, this piston comprising an annular groove 34 in which is inserted a complex segment 35 consisting of an assembly of two segments 35a and 35b of the type shown in FIG. 2b, comprising sections 36a and 36b with an overlap which are arranged at 180.degree. from each other as shown in FIG. 3c, the two segments 35a and 35b being arranged coaxially and facing each other. The outer diameter of the segment 35b in an unstressed state is substantially equal to the inner diameter of the segment 35a in an unstressed state. A pin 37 permits the two segments 35 to be held in a constant relative angular position. A spring 38 is arranged between the lower surface of the annular groove 34 and the lower surface of the segment 35 so as to apply this segment 35 against the upper surface of the groove 34. It may be noted that, when the piston 22 is in position inside the reduced diameter part 10 of the shaft 2, as shown in FIG. 3b, the segments 35 are in contact with the internal surface of this zone 10, their diameter in an unstressed state being slightly greater than the internal diameter of the zone 10. If a pressure reduction is applied above the piston 22 in its position 3b, the pressure difference will be applied both to the lower surface of the segment 35 and to the internal cylindrical surface of this joint so that, on the one hand, the segment 35 is applied against the upper surface of the annular groove 34 and, on the other hand, this segment 35 undergoes a radial expansion which continues during the rise of the piston 22 into the large diameter zone, through separation of the lips of the sections 36a and 36b of the joints 35, until the time when the outer cylindrical surface of the segment 35 comes into contact with the inner surface of the control shaft 2. The arrangement of the two sections 36 at 180.degree. makes it possible to limit considerably the leakage between the interior and the exterior of the segment 35. The piston 22 also comprises, above the segments 35, a protection ring 39 with a diameter between the outer diameter of the segments 35 and the diameter of the inner space of the control shaft outside the zone 10. This ring 39 makes it possible to avoid any contact between the segment 35 and the inner surface of the control shaft 2 during the movements of this shaft in operating the control rods, a slight axial imbalance being liable to occur during these movements. In this event it is the protection ring 39 which comes into contact with the inner surface of the control shaft 2 and which allows the relative recentering of the control shafts 2 and 3, without contact with the segments 35. The spring 38 holding the segments 35 against the upper surface of the annular groove 34 is not essential because, when the piston 22 is introduced into the reduced diameter zone 10 by the relative movement of the control shafts 2 and 3, these segments are moved by sliding against the upper part of the groove 34, if their diameter in an unstressed state is slightly greater than the diameter of the zone 10. If, on the other hand, their diameter were slightly smaller than the diameter of the zone 10, the spring 38 would be essential to avoid a leakage between the upper surface of the segments 35 and the upper surface of the groove 34. FIGS. 4a, 4b and 4c show a second type of sealing segment of a piston 22 which is practically identical to the piston shown in FIGS. 3. The sealing segment 45 consists of three elementary segments 45a, 45b and 45c which are all segments having a straight section such as shown in FIG. 2a. Segment 45a has an outer diameter in an unstressed state which is substantially identical to the inner diameter of the segments 45b and 45c which are identical and are arranged above one another. The height of the segment 45a is equal to twice the height of the segments 45b and 45c. As can be seen in FIG. 4c, the straight sections 46a, 46b and 46c of the segments 45a, 45b and 45c respectively are arranged at 120.degree. from each other, assuming a rotation around the axis of the joint 45. As in the case of the first embodiment described with reference to FIG. 3, a spring 48 enables the segment 45 to be held against the upper surface of the groove 44 provided in the piston 22, and a protection ring 49 is arranged above the joint 45. FIG. 5a and 5b show a sealing segment 55 arranged inside an annular groove 54 machined in a piston 22 of an operating device according to the invention. The segment 55 consists of an inner radial expansion segment 55a and an outer segment 55b, also radially expandable. The inner segment 55a consists of three toric parts joined along sections 56 with an overlap, as shown in FIG. 2b. The outer segment 55b also consists of three toric parts with a rectangular cross-section joined along sections 57 with an overlap, as shown in FIG. 2b. The three sections 56 and the three sections 57 which are arranged at 120.degree. on the segments 55a and 55b respectively are themselves arranged at 60.degree. from each other, assuming a rotation around the axis of the joint. An inner cylindrical wave spring 58 makes it possible to apply outward forces against the three parts of the inner segment 55a, while an outer spring 59 makes it possible to apply inward forces to the three parts of the segment 55b. The spring 59 is arranged inside a groove 60 provided in the outer cylindrical surface of the outer joint 55b. When the piston 22 is introduced into the reduced diameter zone 10, the inner spring 58 is compressed and the outer spring, which is slightly prestressed, relaxes. When a pressure difference is produced on either side of the piston 22 and when the shaft 3 rises, the inner spring 58 relaxes and the outer spring expands. The force exerted outwards by the inner spring 58 (curve A) and the force exerted inwards by the outer spring 59 (curve B) are shown as a function of the radial deformation R of the segment 55. The curve C corresponds to the resultant force exerted in the sealing segment 55. The point I relates to the segment 55 in its state of maximum contraction inside the zone 10 of the control shaft 2, the point E to the normal state of the spring without an external stress, and the point F to the state of maximum radial expansion of the segment under the effect of the pressure, when this segment is in the widened diameter zone of the control shaft 2. The springs 58 and 59 are chosen so that their characteristic curves intersect at N whose abscissa corresponds to R of the sealing segment in the normal state. The segment is thus in a state of zero stress. The balancing of the two springs thus permits the diameter of the segment in the normal state to be adjusted with a high degree of accuracy, while the choices of the characteristics of the two springs permit highly accurate adjustment of the radial expansion of the segment as a function of the difference in pressure on either side of this segment. FIG. 5c shows an alternative form of the segment 55 shown in FIGS. 5a and 5b where the outer toric parts 55b of the segment 55 comprise two grooves 60a and 60b in their lower and higher parts, respectively, in which are arranged two outer springs 59a and 59b, respectively, retaining these parts of the torus forming the outer segment 55b. FIGS. 6a and 6b show an alternative embodiment of the piston 22 which is assembled by screwing a threaded part 62 into a widened and internally tapped part of the shaft 3. The body of the piston 22 comprises a frusto-conical bearing 22a separating an upper large diameter part of the piston 22 from a lower cylindrical part 22b with a smaller diameter. An actuating ring 63 comprising a frusto-conical bearing 63a is fitted onto the lower part 22b of the piston 22 with a sliding friction. A toric segment 64 is inserted between the frusto-conical surfaces 22a and 63a, this segment 64 comprising on its inner surface two corresponding frusto-conical bearings in contact with the frusto-conical surfaces 22a and 63a. On the lower part 22b of the cylinder 22 there is also fitted with a sliding friction an actuating ring 66 comprising a frusto-conical surface 66a on its outer surface. A spring 70 enables some separation to be maintained between the rings 63 and 66. A segment 68 which is practically identical to the segment 64 bears with one of its frusto-conical bearing surfaces against the surface 66a, and with its other frusto-conical bearing surface against the bearing surface 67a of an actuating ring 67 which is also fitted over the lower cylindrical part 22b of the piston 22. This ring 67 comprises a first bore 67b and a second bore 67c whose diameters are different and correspond to the diameters of the two successive zones 22b and 22c of the piston 22. The machining of the surfaces 67b and 67c and of the piston 22 in the zones 22b and 22c is such that the ring 67 can slide on the piston and that a good seal is ensured between the bore 67c and the part 22c of the piston 22. Between the bore 67b, the bores of the rings 63 and 66, on the one hand, and the part 22b of the piston, on the other hand, the fluid filling the enclosure 1 can nevertheless circulate and equilibrate in pressure. For this purpose, longitudinal grooves can be machined in the part 22b of the piston 22. The segments 64 and 68 are radial expansion segments whose diameter in the unstressed state is slightly greater than the internal diameter of the zone 10 of the control shaft 2. When the piston 22 is moved to coincide with the zone 10, as shown in FIG. 6b, the bringing of the outer surfaces of the segments 64 and 68 in contact with the inner surface of the zone 10 produces a slight movement of the actuating rings 63 and 66 relative to the ring 67. A pressure difference is produced on either side of the segments 64 and 68, and when the piston 22 moves upward, this pressure difference acts on a circular cross-section included between the bore 67c and the diameter of the zone 10 to produce, through the intermediary of the frusto-conical bearing 67a, the expansion of the segment 68, the upward movement of the actuating ring 66 and of the actuating ring 63 through the intermediary of the spring 70, which causes the expansion of the segment 64. This solution has the advantage of increasing the force which is exerted on the piston during its rise by increasing the cross-section to which pressure is applied by virtue of using an actuating ring with a frusto-conical bearing. There is also a possibility of an additional control by adjusting the angle of the frusto-conical part for actuating the ring. FIGS. 7a and 7b show a different and highly simplified embodiment of a sealing segment of a piston 22 employed in an operating device according to the invention. This sealing segment consists of a profiled elastic joint arranged in a groove 74 whose U-shaped or V-shaped meridian cross-section 73 has two branches 73a and 73b whose separation can vary through elastic deformation of the joint. The open part of the joint is directed towards the zone where the pressure is higher when the absorber cluster is operated, namely, downwards. This elastic deformation can be obtained, for example, when the piston 22 enters the reduced diameter zone 10, as can be seen in FIG. 7b. The branches 73a and 73b are then brought toward each other if the external diameter of the segment is slightly greater than the internal diameter of the zone 10. When a pressure difference is established on either side of the segment 73, the forces acting on the interior of this segment produce an increased separation of the branches 73a and 73b, with the result that the branch 73a can come into contact with the inner surface of the large diameter part of the control shaft 2, when the piston 22 rises inside the shaft 2 under the effect of the pressure difference. The segments employed in the device according to the invention can be made of various materials, for example carbon, graphite, a wear-resistant alloy of cobalt or an alloy with a high nickel content, cast iron with chromized segments or having undergone a hard chromium plating or of an elastic steel which has been chromized or has undergone a process of hard chromium plating or chemical nickel plating. The main advantages of the invention, as shown in the description given above, are to allow placing the sealing segments of the activating piston of the second control shaft in contact with the inner surface of the first control shaft only at the time when the operating device for the lifting of the cluster of absorbing material is brought into action. In particular, untimely wear of these sealing segments, and risks of the second control shaft rising in the first, during the movement of the reactor control rods, are avoided. The initiation of the leaktightness of the segments is produced automatically, since the relative positions of the first and of the second control shafts are perfectly determined at the time when the rise of the absorber clusters is commanded. The position of the high overrun of the first control shaft is, in fact, perfectly determined, as well as the low position of the second control shaft, when the absorber clusters are completely inserted. The position of the actuating piston and of the sealing segments in the reduced diameter zone of the first control shaft can thus be obtained in a completely reliable manner. The invention is not limited to the embodiments which have been described but, on the contrary, comprises all the alternative forms. Thus, the actuating pistons which have been described usually comprise only one sealing segment, but it is possible to associate several sealing segments arranged above each other. For example, two sealing segments can be employed, permitting a good centering of the piston in the internal cylindrical space of the first control shaft. It is also possible to conceive of other shapes of radial expansion segments than those which have been described. It is possible to employ a reduced diameter zone occupying the whole low part of the first control shaft or, on the contrary, a zone occupying a length which is only very slightly greater than the length of the actuating piston (10 to 15 cm). Finally, the operating device according to the invention is applicable in all cases where a reactor with spectral shift control comprises absorber clusters or control rods introduced into the same assemblies. |
description | While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers"" specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The present invention will now be described with reference to the attached figures. Although the various regions and structures are depicted in the drawings as having very precise, sharp configurations and profiles, those skilled in the art recognize that, in reality, these regions and structures are not as precise as indicated in the drawings. Additionally, the relative sizes of the various features depicted in the drawings may be exaggerated or reduced as compared to the size of those features or regions on fabricated devices. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present invention. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase. FIG. 3 is a cross-sectional view of an illustrative reticle 20 that may be manufactured and used in accordance with various embodiments of the present invention. The reticle 20 is comprised of a substrate 22 and an opaque layer 24. A layer of photoresist 26 is positioned above the opaque layer 24. The substrate 22 may be comprised of a variety of transparent materials, such as glass or quartz. The substrate 22 may have a thickness that ranges from 0.09-0.25 inches. The opaque layer 24 may also be comprised of a variety of materials, such as a metal, e.g., chromium or a chromium alloy. The opaque layer 24 may have a thickness that ranges from approximately 50-150 nm. The layer of photoresist 26 may be a positive or negative resist, and it may be formed above the opaque layer 24 by a variety of known techniques. As will be understood by those skilled in the art after a complete reading of the present application, the present invention is not limited in its use to any particular type of reticle or the materials used to manufacture the reticle. Moreover, the present invention may be employed when using positive or negative photoresist materials, and in defining patterns in the opaque layer 24 of any size, shape or configuration. Thus, the present invention should not be considered as limited to the materials of construction of the reticle 20 or the pattern formed in the reticle 20 unless such limitations are expressly recited in the appended claims. FIG. 4 is a schematic view of an illustrative reticle exposure tool 30 that may be used to expose selective portions of the layer of photoresist 26 above the reticle 20. As shown in FIG. 4, the reticle exposure tool 30 is comprised of a housing 32, a controller 34 and an electron beam source 36. Many features of the reticle exposure tool 30 are not depicted in FIG. 4 so as not to obscure the present invention. For example, an actual reticle exposure tool 30 would include, among other things, a power supply, various optical lenses, means for securing the reticle 20 in place during the writing process, etc. The reticle exposure tool 30 is intended to be illustrative in nature in that it may represent any of a variety of tools used to produce reticles. For example, in one illustrative embodiment, the reticle exposure tool 10 is an EBM 3000 electron beam tool with a variable shaped electron beam sold by Toshiba Machine. Of course, as will be apparent to those skilled in the art after a complete reading of the present application, the present invention may be employed with a variety of different types of reticle writing tools, such as those manufactured by Joel, Hitachi and Etec. In general, the electron beam source 36, such as an electron beam gun, will be used to direct a stream of electrons, as indicated by the arrow 37, to the desired areas of the layer of photoresist 26 in a predetermined writing pattern. The controller 34 controls the writing pattern of the electron beam source 36 and the energy level used in the reticle writing process. For modern reticle writing tools, this energy level may be approximately 50 keV. FIG. 5 is a plan view of a reticle 40 with a plurality of features 42 formed in the reticle 30 in accordance with one illustrative embodiment of the present invention. FIG. 5 may be compared with FIG. 2 for purposes of explaining the writing strategy of the present invention. In general, as shown in FIG. 5, the data corresponding to the feature 42 is fragmented into three segments 1-3 as compared to the four segments 1-4 for the features 10 generated in accordance with a prior art reticle writing method as depicted in FIG. 2. Moreover, in contrast to prior art methodologies, the reticle writing strategy of the present invention allows the segments 1-3 to overlap in the areas 44 indicated in FIGS. 5 and 6. In the depicted embodiment, the overlap regions 44 have a width dimension 44W and a length dimension 44L as indicated in the drawings. Of course, the overlap regions 44 need not be rectangular or symmetrical for every reticle writing strategy. FIG. 6 is an enlarged view of an illustrative feature 42 depicting an illustrative overlap regions 44 allowed by the present invention. The size of the overlap regions 44 may vary depending upon a variety of factors, such as the pattern being written, the location of the overlap regions 44, the precision in forming the corresponding feature in the integrated circuit device, etc. In the overlap regions 44, the layer of photoresist 26 will be subjected to an exposure process twice. Nevertheless, the present invention may be very useful in many situations to reduce the overall reticle writing time. FIGS. 7A-7C are plan views depicting a reticle writing plan for a more complex reticle pattern. More specifically, FIG. 7A is a plan view of a portion of a pattern 50 to be created on a reticle (not shown). FIG. 7B is a depiction of a reticle writing strategy according to one illustrative prior art technique, whereas FIG. 7C is a depiction of a reticle writing plan in accordance with one embodiment of the present invention. As shown in FIG. 7B, a prior art reticle writing methodology would involve fracturing the desired pattern 50 into 13 fragmented fields 51 in which each of the fields 1-13 do not overlap with one another. In contrast, FIG. 7C is a plan view depicting a reticle writing plan in which overlap of the fractured fields 51 is allowed. As shown therein, the number of fragmented fields 51 is reduced to seven when practicing the reticle writing methodology of the present invention. That is, all other things being equal, the reticle writing time may be reduced by over 50% by using the present invention. Again, the size and extent of the overlap regions 44 may vary with each application. Traditionally, a semiconductor manufacturer will provide a reticle manufacturer with digital information that reflects the overall desired reticle pattern. The reticle manufacturer may then fragment the digital data for the overall reticle pattern to produce a writing plan for writing the desired pattern on the reticle. In accordance with one illustrative embodiment of the present invention, the reticle pattern information is provided to the reticle manufacturer as separate data packages. That is, for example, with reference to FIG. 5, the reticle manufacturer may be provided with a first set of data that corresponds to the sections labeled xe2x80x9c2xe2x80x9d in FIG. 5, and a second set of data that corresponds to the sections labeled xe2x80x9c1xe2x80x9d and xe2x80x9c3.xe2x80x9d Upon receipt of this information, the controller 34 for the reticle exposure tool 30 may perform a first reticle writing process in which all of the number xe2x80x9c2xe2x80x9d sections are exposed in the layer of photoresist 26. Thereafter, the controller 34 may perform a second reticle writing process in which all of the regions xe2x80x9c1xe2x80x9d and xe2x80x9c3xe2x80x9d are exposed. Thus, by providing the data that corresponds to areas to be exposed in at least two separate data fields, the reticle exposure tool 30 may perform its exposure processes without regard for any overlap regions 44 in the combined fields. Similarly, the digital data for the overall reticle pattern shown in FIG. 7A may be provided as two sets of data. The first set of data for the desired reticle pattern may include data for all of the odd number fields 1, 3, 5, 7, etc. Upon receipt of this first set of data, the controller 34 may direct a writing process in which only these fields are exposed. Thereafter, a second set of data is provided to the controller 34 for the even numbered fields, e.g., 2, 4, 6, etc. The controller 34 may then direct a writing operation wherein only the even numbered fields are subjected to the exposure process. This second writing operation is performed independent of the first writing process using the first set of data. Using the present methodology, the data for the overall reticle pattern may be provided to the reticle exposure tool 30 in such a manner that the location and size of the overlap regions 44 in the pattern may be controlled. Moreover, the data for the overall reticle pattern may be divided into more than two data packages depending upon the particular application and the complexity of the reticle pattern. For example, the digital data corresponding to the overall reticle pattern may be separated into three separate groups, and first, second and third writing patterns may be performed to create a reticle. Thereafter, multiple reticle writing processes may be performed in accordance with the present invention wherein overlap regions 44 are allowed in the reticle writing processes. Lastly, the present invention may be employed in combination with prior art reticle writing strategies. For example, only selected portions of an overall reticle pattern may be written in accordance with the techniques described herein. The reticle writing strategies disclosed herein are essentially independent of the process bias normally taken into account when the writing pattern for a reticle is determined. That is, since the present invention allows for the overlap of portions of the areas exposed during the multiple writing processes, process bias becomes less important in designing the reticle writing strategy. Simply put, the overlap regions 44 allowed by the present invention can be used to compensate for changes in process bias. FIG. 8 is a schematic depiction of a system that may be employed in accordance with one illustrative embodiment of the present invention. As shown therein, a wafer exposure tool 60 uses a reticle 20, the pattern of which was written in accordance with the techniques disclosed herein, to expose selected portions of a layer of photoresist 62 formed above a process layer 64 that is formed above a semiconducting substrate 66. In general, the wafer exposure tool 60 is comprised of a housing 68, a light source 70 and a wafer stage 72. Radiant energy, typically ultraviolet light, as illustratively indicated by the arrow 74, is directed through the reticle 20 and projected onto a portion of the layer of photoresist 62. The wafer exposure tool 60 also includes a relatively complex collection of optical lenses and associated equipment to perform this task, although such equipment is not depicted in FIG. 8 so as not to obscure the present invention. The exposure tool 40 may be any type of exposure tool commonly found in semiconductor manufacturing operations. Typically, the exposure tool 40 is a so-called stepper in which portions of the layer of photoresist 62 are exposed on a flash-by-flash basis as the wafer is stepped, or moved, incrementally after each flash. This process is continued until such time as all desired regions of the layer of photoresist has been exposed. The layer of photoresist 62 may be either a positive or negative photoresist material. Moreover, the process layer 64 may be comprised of a variety of materials, e.g., a metal, an insulating layer, polysilicon, etc. In one aspect, the present invention is generally directed to various reticle writing methodologies to reduce write time, and a system for performing same. In one illustrative embodiment, the method comprises exposing a layer of photoresist in accordance with a first writing pattern in a first area of the layer of photoresist and exposing the layer of photoresist in accordance with a second writing pattern in a second area of the layer of photoresist, the first and second areas of the layer of photoresist overlapping one another in at least one region. In further embodiments, the method further comprises creating the first and second writing patterns by separating digital data corresponding to a desired pattern for a reticle into at least two separate groups of data, a first of the data groups being used to define the first writing pattern and a second of the data groups being used to define the second writing pattern. In another illustrative embodiment, the method comprises creating a collection of digital data corresponding to a desired pattern for a reticle and separating the collection of digital data into at least two separate groups of data, a first of the data groups being used to define a first writing pattern for the reticle, a second of the data groups being used to define a second writing pattern for the reticle, wherein the first and second writing patterns overlap one another in at least one region. In further embodiments, the method may further comprise separating the collection of digital data into at least three separate groups of data, a third of the data groups being used to define a third writing pattern for the reticle, wherein the third reticle writing pattern overlaps at least one of the first and second writing patterns in at least one region. The present invention may also be employed in the context of forming features for an integrated circuit device. That is, the writing methodologies disclosed herein may be applied to expose a layer of photoresist (positive or negative) that is used in forming features on production integrated circuit devices. Such features may include, but should not be considered as limited to, the formation of features such as gate electrode structures, trenches in a layer of insulating material, shallow trench isolation structures, etc. For example, the techniques described herein may be employed to expose a layer of photoresist formed above a layer of polysilicon. Thereafter, the layer of photoresist may be developed using traditional photoresist development processes. One or more etching processes may then be performed while using the patterned layer of photoresist as a mask to define a plurality of features, e.g., gate electrode structures, in the layer of polysilicon. In this embodiment of the invention, the desired pattern to be formed in the layer of photoresist may be determined based upon the particular product or feature under construction. The desired pattern for the layer of photoresist may typically be represented by a collection of digital information. Thereafter, this collection of digital data may, in one embodiment, be separated into separate data packages in a similar manner to that described previously with respect to the use of the present invention in forming a reticle. In short, the digital information corresponding to the desired pattern to be formed in the layer of photoresist may be separated into at least two separate data fields. In this embodiment of the present invention, electrons from an electron beam source, such as the source 36 depicted in the exposure tool 30 shown in FIG. 4, may be used to expose the desired portions of the layer of photoresist. The writing pattern for the electron beam source 36 to expose the layer of photoresist may be provided to an exposure tool in a manner similar to that described above with respect to the writing pattern for the reticle. That is, the writing pattern for the layer of photoresist may be separated into at least a first set of data and a second set of data, each of which correspond to desired areas of exposure of the layer of photoresist. Thereafter, the layer of photoresist may be exposed by performing multiple writing or exposure processes in the manner described above with respect to the writing strategies employed in forming the reticle. A variety of methods are disclosed herein wherein the present invention may be employed to expose a layer of photoresist in the context of manufacturing production integrated circuit devices. In one illustrative embodiment, the method comprises forming a layer of photoresist above at least one of a semiconducting substrate and a process layer, exposing the layer of photoresist in accordance with a first writing pattern in a first area of the layer of photoresist, and exposing the layer of photoresist in accordance with a second writing pattern in a second area of the layer of photoresist, the first and second areas overlapping one another in at least one region. The substrate may be comprised of a variety of semiconducting materials, e.g., silicon, germanium, etc. The process layer may be comprised of any material employed in manufacturing integrated circuit products, e.g., a layer of insulating material, a layer comprised of a metal, polysilicon, etc. After the layer of photoresist is exposed in accordance with the present techniques, it may be developed using a variety of known development techniques and processes. Thereafter, the patterned layer of photoresist may be used as a mask layer in one or more subsequent etching processes. In another illustrative embodiment, the method comprises forming a layer of photoresist above at least one of a semiconducting substrate and a process layer, creating a collection of digital data corresponding to a desired pattern for the layer of photoresist, and separating the collection of digital data into at least two separate groups of data, a first of the data groups being used to define a first writing pattern for the layer of photoresist, a second of the data groups being used to define a second writing pattern for the layer of photoresist, wherein the first and second writing patterns overlap one another in at least one region. In yet another illustrative embodiment, there is provided an exposure system that comprises an electron beam source and a controller that is adapted to direct electrons emitted by the electron beam source so as to expose a layer of photoresist in accordance with a first writing pattern in a first area of a layer of photoresist and expose the layer of photoresist in accordance with a second writing pattern in a second area of the layer of photoresist, the first and second areas of the layer of photoresist overlapping one another in at least one region. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. |
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description | The present invention relates to a method of removing a particle of a photomask by applying an atomic force microscope technology. A micromachining technology of a nanometer order is requested for high function formation and high integration formation, and research and development of a machining technology of local anodic oxidation or microscratch machining using a scanning probe microscope (SPM) are intensely carried out. Not only a pursuit for a possibility of micromachining but also a pursuit for machining of an accurate shape or with high accuracy have been requested. For example, recently, in an apparatus on the basis of an atomic force microscope (AFM), high accuracy correction of a micropattern surplus defect of a photomask is carried out by microscratch machining in which scanning is carried out with exerting a high press force (high load) on a stylus harder than a material to be machined and physical removal is carried accordingly for machining (Nonpatent Reference 1). In accordance with a progress in miniaturization of lithography, a size of a particle to be removed on a silicon wafer becomes small, a and sufficient resolution cannot be obtained an optical microscope so that the particle is now observed by a scanning electron microscope or an atomic force microscope. Although removal of a particle is heretofore dependent on removal by cleaning, in the case of a small number of particles, the silicon wafer may conversely be contaminated at a cleaning step, and a method of effectively removing a small number of particles has been requested. Recently, there is also reported a method of applying an atomic force microscope technology used for observation as a method of removing a small number of fine particles on a silicon wafer (Nonpatent Reference 2). Similar to the silicon wafer, also in the case of a photomask, with increased miniaturization of lithography, a size of a particle to be removed becomes small and a method of removing a particle which cannot be removed by cleaning is requested. When a particle is present at a photomask before being pasted with a pellicle, even when the number of particles is small, defects are produced in all of patterns to be transcribed and therefore, the particles need to be removed completely. There are various kinds of particles on a photomask such as a metal, a glass bump, a resist residue and the like and in order to ensure an optical property, there has been requested a method of removing a particle without damaging a quartz or glass substrate of a matrix as much as possible. In order to remove a particle, it is necessary to know the kind of the particle since a method of removing a particle differs by the kind of the particle. There has been known a method of pressing a diamond stylus having a sharp tip to a particle and predicting Young's modulus of the particle from bending of a cantilever or a depth of an impression produced by the pressing and predicting a material of the particle from a value of Young's modulus as an indentation method. Recently, there has been carried out a nanoindentation method for executing an indentation method by attaching a diamond stylus having a tip diameter equal to or smaller than 100 nm to an atomic force microscope as a new application of the atomic force microscope as a method of predicting a material by calculating a hardness of a small region. The method provides a function of predicting a material of even a small object of a particle or the like. [Nonpatent Reference 1] T. Amanao, M. Nishiguch, H. Hashimoto, Y. Morikawa, N. Hayashi, R. White, R. Bozak, and L. Terrill, Proc. of SPIE 5256 538–545 (2003) [Nonpatent Reference 2] Junichi Muramoto, Hitoshi Kuniyasu, Tsuyoshi Hattori, Proceeding of 51st Conference of Applied Physics No. 2, 31p-B-2, p856 (2004) It is an object of the invention to reduce damage on a quartz or glass substrate in removing a small particle on a photomask using an atomic force microscope technology. With regard to a particle on a photomask which is not removed by cleaning, a kind of the particle is determined by pressing a hard atomic force microscope stylus having a spring constant of a spring constant equal to or larger than 300 N/m to the particle and detecting bending relative to a press force, or accurately measuring a depth of an impression produced when pressed with a constant load by a stylus which is slender and is provided with a high aspect ratio, and a kind of a stylus used for removing the particle is changed in accordance with the kind of the particle. When a particle is softer than a quartz or glass substrate, the particle is moved or physically removed by an atomic force microscope stylus harder than the particle and softer than the quartz or glass substrate. When a particle is equal to or harder than the quartz or glass substrate, the particle is physically removed by scanning the hard stylus having the spring constant equal to or larger than 300 N/m used for pressing the particle with a high load. A hardness of the particle to be removed is known by detecting bending relative to the press force or accurately measuring the depth of the impression produced when pressed with a constant load by the stylus which is slender and provided with the high aspect ratio and therefore, the kind of the particle to be removed can be determined from the hardness. With regard to a soft particle, the particle is moved or physically removed by the atomic force microscope stylus softer than the quartz or glass substrate and therefore, the quartz or glass substrate is not damaged. Only in the case of a particle equivalent to or harder than the quartz or glass substrate, the particle is physically removed by the hard stylus such as diamond and therefore, a case having a possibility of damaging the substrate can be reduced. An embodiment of the invention will be explained in reference to the drawings as follows. FIGS. 1A–1C are a schematic sectional views showing a method of removing a particle by determining a kind of the particle. A photomask having light blocking film pattern 2 in which photomask a particle is found by a defect inspection apparatus is introduced into an atomic force microscope apparatus and an XY stage is moved such that a position of the particle 3 found by the defect inspection apparatus is brought into a field of view of the atomic force microscope apparatus. The position of the particle 3 is confirmed by observing a region including the particle 3 by a low load or intermittent contact mode such that the region including the particle 3 is not damaged. A hard atomic force microscope needle 4 of diamond or the like having a spring constant equal to or larger than 300 N/m is brought to right above the particle 3 as shown by FIG. 1A and the hard stylus 4 is pressed from above the particle. Information of hardness is acquired by detecting bending relative to the press force, and a kind of the particle is determined from the hardness information. In the case of the spring constant of 300 N/m, the stylus 4 can be pressed to a comparatively hard object of a quartz or a glass substrate. There are particles of different materials such as metal, a resist residue, an MoSi residue, or a projection of glass. Since the material differs, the hardness naturally differs. There are kinds of particles of a metal, a resist residue, an MoSi residue, projection of glass and the like and the kind of the particle can be determined from the hardness. In determining the kind of the particle at the above-described step, when the particle 3 to be removed is a metal particle or a residue of a resist softer than the quartz or a glass substrate 1, as shown by FIG. 1B, the hard stylus is replaced by an atomic force microscope stylus 5 comprising a material harder than a particle of silicon and softer than the quartz or glass substrate, and the particle is moved or physically removed by scanning the stylus 5 while pressing the particle at a side face of the stylus 5. The particle 3 can be removed without damaging the quartz or glass substrate 1 since the atomic force microscope stylus 5 harder than the particle 3 and softer than the quartz or glass substrate is used. When the particle 3 to be removed is a glass bump having a hardness equivalent to that of the quartz or glass substrate 1, in FIG. 1A, the stylus 4 pressed into the particle is temporarily pulled up and as shown by FIG. 1C, the particle 3 is physically removed by scanning only a region of the particle 3 with a load higher than a load of using the hard atomic force microscope stylus 4 in observation as it is without replacing the atomic force microscope stylus. FIGS. 2A–2B are schematic sectional views showing another method of determining a kind of a particle. First, as shown by FIG. 2A, the hard atomic force microscope stylus 4 is pressed with a constant load. Next, as shown by FIG. 2B, the atomic force microscope stylus 4 is replaced by a stylus 6 which is slender and provided with a high aspect ratio such as a carbon nanotube and an impression 7 produced by pressing the stylus 4 is scanned and a depth thereof is measured. By accurately measuring the depth of the impression 7, the hardness of the particle 3 is predicted and the kind of the particle 3 is determined from the predicted hardness information. When the kind of the particle 3 is determined, the particle is removed similar to the embodiment of FIGS. 1A–1C. That is, with regard to the particle 3 softer than the quartz or glass substrate, the stylus is replaced by a stylus 5 harder than the particle and softer than the quartz or glass substrate such that the quartz or glass substrate 1 is not impaired and the particle 3 is moved or removed by the scan with the stylus. With regard to the hard particle, the stylus is replaced by the hard stylus 4 and the particle 3 is physically removed by the scanning of the stylus 4 with a high load. |
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046684441 | summary | BACKGROUND OF THE INVENTION The invention is directed to a process the production of substantially isotropic, spherical fuel or absorber elements of higher strength for high temperature reactors by pressing a mixture of graphite molding powder containing binder resin with coated nuclear fuel or absorber particles to form a spherical nucleus, pressing a shell made of the same graphite molding powder, carbonizing the binder resin and vacuum calcining up to about 2000.degree. C. Spherical fuel or absorber elements for high temperature reactors consist of a spherical ball nucleus, in which the nuclear fuel or the absorber material is present in the form of coated nuclear fuel or absorber particles, embedded in a graphitic matrix, as well as an outer fuel or absorber free shell which encloses these spherical nuclei and is made of the same material as this graphitic matix. The elements are produced by molding as is described e.g. in German Pat. No. 1909871 whereby first the spherical nucleus is preliminarily molded from a mixture of so-called graphite molding powder and the coated particles and subsequently using this graphite molding powder the fuel or absorber free shell is molded on this nucleus. Subsequently the binder of the graphite molding powder is carbonized. It is required of spherical fuel or absorber elements that the physical or mechanical properties of the matrix graphite are substantially isotropic. As a measure for a possible anisotropy there is defined customarily the quotient of the thermal coefficient of expansion measured parallel and perpendicular to specific preferred directions. Such anisotropy is produced because graphite normally is a highly anisotropic material because of its crystal structure, which only shows macroscopic isotropic properties if there is produced a random statistical distribution of the graphite granules of the crystallites. Insofar as they are not carried out most substantially isostatically, molding processes represent particularly techniques which can lead to a preferred orientation of the graphite granules corresponding to the preferred direction of the molding process and thus to a significant anisotropy of the molded body produced. This state of affairs, anisotropic properties of the graphite particles on the one hand and the requirement of isotropic properties of the elements produced from these graphite granules on the other hand has led to the molding of spherical fuel or absorber the elements today exclusively by nearly isostatic molding procedures. Thereby the spherical nucleus if preliminarily pressed in an elastic mold, as a rule made of silicone rubber material, likewise the shell is molded in a mold which likewise normally consists of silicone rubber. Through their elasticity these molds cause a preeminently radial distribution of pressure and therefore in the molding lead to the desired statistical distribution of the graphite granules so that the resulting molded article exhibits the most nearly isotropic properties. On the other hand, the use of those molded shapes constrains the molding process to be carried out a lower temperatures, as a rule at room temperature because of insufficient temperature resistance, through which high molding pressure are required. In order to prevent the danger of the decomposition of the coated particles arising at high molding pressures there are necessary expensive encasing processes such as described e.g. in German Pat. No. 1909871 or specially constructed molding compositions such as described, e.g. in German Pat. No. 2348282 (and related Huschka U.S. Pat. No. 3,978,177, the entire disclosure of which is hereby incorporated by reference and relied upon). Furthermore, the high molding pressure limits the life of the compression mold. Independent of these problems related to the molding pressures it is necessary to shape the surface of the spherical nucleus in order that there is formed a sufficient bond between the spherical nucleus and the pressed on spherical shell which prevents the spherical shell from spalling from the spherical nucleus either during the necessary concluding heat treatment step of the fuel or absorber element, i.e., the necessary coking of the binder and a subsequent purification and degassing, or during the mechanical stress in the reactor operation. This shaping of the spherical nucleus surface, however, requires complicated molding tools. Therefore, it was the problem of the present invention to develop a process for the production of substantially isotropic, spherical fuel or absorber elements of high strength for high temperature reactors by molding a mixture of graphite molding powder containing a binder resin with coated nuclear fuel-or absorber particles to form a spherical nucleus, pressing on a shell made of the same graphite molding powder, carbonizing the binder resin and vacuum calcining up to about 2000.degree. C. whereby there should be eliminated elastic compression molds, a special shaping of the spherical nucleus should be unnecessary and should be preliminary molded at higher temperatures. SUMMARY OF THE INVENTION This problem was solved according to the invention by using as the graphite molding powder a mixture of graphitized coke granules having substantially isotropic properties and a hardenable resin binder, that first from thus molding powder there is preliminarily pressed at 80.degree. to 120.degree. C. two ellipsoid shaped shell halves successively in a first cylindrical steel molding die having a smooth ellipsoidal hollowing of the lower die and a smooth ellipsoidal shaped front surface of the upper die adjusted to it, that subsequently there is preliminarily pressed from this mixture of the graphite molding powder and coated particles likewise at 80.degree. to 120.degree. C. in a second steel molding die which also has smooth surfaces an related to the shell halves appropriately elliposida shaped spherical nucleus whereby the density of the graphite matrix in the preliminarily pressed nucleus and in the preliminarily pressed shell halves must be between 1.0 and 1.4 grams/cm.sup.3, that then the nucleus and the two shell halves are put together to form an ellipsoidally shaped body and that finally this body is finally molded in the plastic temperature range of the resin binder to the final composition in known manner in a third steel molding die having hemispherically shaped hollowed and upper and lower dies. Preferably, there is used as graphite powder soft coal secondary pitch coke and it is preliminarily pressed so that the density of the preliminary pressed portions is between 1.1 and 1.3 g/cm.sup.3. Furthermore, it is advantageous to so regulate the temperature in the final molding process to the final composition that the resin binder is hardened in the molding die and the final molded sphere or ball can be ejected at the molding temperature. Besides it has proven good to preheat the preliminarily pressed portions to a temperature slightly below the final molding temperature and to insert it into the likewise preheated compression mold, whereby the final molding is carried out advantageously with a floating matrix. It has been surprisingly found that by using isotropic graphite raw material such as e.g. soft coal secondary pitch coke the molding process can be controlled in such manner that it is not necessary to shape the surface of the spherical nucleus but that exclusively smooth molding tools can be used if the density of the preliminary pressed portions is within the mentioned range between 1.0 and 1.4 g/cm.sup.3. Furthermore, it has been found that by using this graphite molding powder elements of sufficient isotropy can also then be attained if the molding process is carried out anisotropic dimensionally in steel dies. A particularly simple temperature guide for the molding process results from the use of hardenable resin binders. A temperature in the plastic range of the resin binder (about 100.degree. C.) thin is sufficient to reduce the molding pressure to such an extent that there can be eliminated an encasing of the particles as in German Pat. No. 1909871 or special molding compositions as in German Pat. No. 23482821 or the related Huschka U.S. Pat. No. 3,978,177 to prevent damages to the coated particles brought about by the molding process. The pressing in steel dies having smooth surfaces furthermore offers the advantage that there can be eliminated an otherwise customary mechanical subsequent treatment of the elements to produce an exact spherical shape. |
abstract | An improved fusion reactor design with provision for supplying plasma fuel inside a model reactor without consuming additional power in the process. Embodiments provide free choice of useful fuels from the full range of fusible isotopes. Other embodiments provide means of selectively extracting up-scattered electrons from the plasma, followed by replacing them with electrons of corrected energy. Computer simulations show fusion reactors constructed with these inventive improvements will demonstrate increased net-power compared to other fusion reactors of similar size. The Specification of the invention leads immediately to staged reactor development, starting from small-scale model-reactors, moving on to larger and larger scale models, culminating with commercial power plants. |
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045044392 | claims | 1. A gas cooled nuclear reactor comprising: a reactor core, at least one closed circuit having a heat absorbing member for receiving cooling gas from said reactor core, a hot gas conduit and a cold gas conduit connecting said heat absorbing member to said reactor core and means for mixing at least a portion of a cooled cooling gas from an outlet side of said heat absorbing member with hot gas downstream of said reactor core and in said hot gas conduit, said means comprising at least one adjustable valve, a conduit connecting said valve with said cold gas conduit and a plurality of tubes projecting into said hot gas conduit, and a distributor head having a plurality of orifices mounted on each of said tubes for dispersing cold gas into said hot gas conduit thereby controlling the temperature of said cooling gas. 2. The gas cooled nuclear reactor of claim 1, wherein said plurality of tubes project into said hot gas conduit against the flow of hot gas in said hot gas conduit. 3. The gas cooled nuclear reactor of claim 2, wherein said hot gas conduits divert the flow of hot gas by means of an apertured plate obliquely positioned in said conduit at a point of diversion of said cooling gas. 4. The gas cooled nuclear reactor of claim 1, wherein said valve is controlled by a regulator. 5. The gas cooled nuclear reactor of claim 14 wherein said heat absorbing member comprises a heat exchanger. 6. The gas cooled nuclear reactor of claim 5, further including an apertured plate which defines a point of diversion of said cooling gas wherein said plurality of tubes project into said hot gas conduit at a point between said reactor core and said apertured plate and at said point of diversion. 7. The gas cooled nuclear reactor of claim 5, further including an apertured plate mounted in said hot gas conduit wherein said plurality of tubes project into said hot gas conduit and through said apertured plate. 8. A process for controlling the temperature in a circuit of a high temperature gas cooled nuclear reactor comprising: flowing hot gas from a reactor core through a hot gas conduit and then into a heat absorbing member where it is cooled, and then flowing cooled gas through a cold gas conduit and back to a reactor core; diverting at least a portion of said cooled gas flowing through said cold gas conduit to a gas mixing device; introducing said diverted cooled gas from said gas mixing device into said hot gas from said reactor through a plurality of tubes extending into said hot gas conduit before entry of the hot gas into said heat absorbing member, said cooled gas being introduced through a plurality of multiple orifice distributor heads respectively mounted on said plurality of tubes, said portion of cooled gas being controlled by an adjustable valve member. 9. The process of claim 8, wherein a plurality of circuits receive hot gas from a reactor core and said adjustable valve member is operable to control the temperature of the cooling gas, said temperature control being independent in each circuit. 10. The process of claim 8 or 9, wherein said introducing comprises introducing said cooled gas in a direction countercurrent to the flow of hot gas in said hot gas conduit. 11. The process of claim 8 or 9, wherein said introducing comprises introducing said cooled gas essentially perpendicular to the flow of hot gas in said hot gas conduit. 12. The process of claim 8 or 9, further including the step of diverting said hot gas flow at a first point upstream of said heat absorbing member wherein said introducing comprises introducing said cooled gas into said hot gas conduit at a second point downstream of said first point. |
048083690 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been developed on the basis of the results of the discussion of the characteristics of the conventional emergency core cooling apparatus shown in the "Hitachi Review" referred to in the previous paragraph. The contents of this discussion are as follows. FIG. 1 is a schematic system diagram of the emergency core cooling apparatus taken from the "Hitachi Review", page 300. The conventional emergency core cooling apparatus has two systems of HPCS 40A, 40B, one system of HPCI 41, and three systems of LPFL 42A, 42B, 42C. Each of HPCS and LPFL has a motor-driven pump. The HPCI has a turbine-driven pump. Each of LPFL has a heat exchanger (cooler) 43 functioning as a residual heat removal apparatus (RHR apparatus). A core spray header 21 is provided at the upper portion of the interior of a core shroud 8 disposed in a reactor pressure vessel 7 and surrounding a core 9. This core spray header 21 is connected to HPCS's 40A, 40B. When HPCS's 40A, 40B are driven, the cooling water 4 in a suppression chamber 3 is sprayed to the core 9 by the core spray header 21. When LPFL's 42A, 42B are driven, the cooling water 4 is injected into the portion of the interior of the reactor pressure vessel 7 which is on the out side of a core shroud 8. When LPFL 42C and HPCI 41 are driven, the cooling water 4 is supplied to the interior of the reactor pressure vessel 7 via feed water pipes 13A, 13B. The conventional emergency core cooling apparatus has three diesel-engine generators as emergency power sources used when a normally-driven power source fails. The pump in each of HPCS's and LPFL's is driven by these diesel-engine generators. The conventional emergency core cooling structure is divided into three sections, i.e. section I having HPCS 40A and LPFL 42A, section II having HPCS 40B and LPFL 42B and section III having HPCI 41 and LPFL 42C. One diesel-engine generator is alloted to each section. Since an emergency core cooling apparatus requires to have a high reliability, it is necessary that the highest effect to be produced with a required minimum capacity thereof. Especially, the economical efficiency and the improvement of performance of the structure have earnestly been studied. The present inventors discussed the properties of the conventional emergency core cooling apparatus to discover that, if the breakage of a HPCS pipe (a pipe for a HPCS) should have occurred, there was the possibility that the water level in the nuclear reactor become slightly lower than the top of effective heat generating portion. The contents of the above discussion are as follows. The transients, which would occur if the breakage of a HPCS pipe takes place in the conventional emergency core cooling structure, in the water level in the nuclear reactor are shown by a broken line in FIG. 5. When a HPCS pipe is broken, the nuclear reactor is automatically scrammed and isolated but the cooling water in the reactor pressure vessel 7 blow down from a brak pipe, so that the water level in the nuclear reactor begins to decrease. When the water level in the nuclear reactor begins to decrease, the high-pressure emergency core cooling systems are operated automatically (HPCI 48 operates) in advance of any other means. When a pipe for HPCS 40A in the section I is broken under the diesel-engine generator in the section II failing, HPCI 41 is left as an operable high-pressure emergency core cooling system. Accordingly, only one high-pressure emergency core cooling system is operated (HPCI 48 operates), and an automatic depressurization system (ADS) is then operated (ADS 49 operates). As a result, the cooling water level in the reactor pressure vessel 7 is recovery to temporarily because of flushing by depressurization. However, the water level in the nuclear reactor vessel thereafter decreases again. When the pressure in the reactor pressure vessel 7 has decreased to a predetermined level due to the operation 49 of ADS, LPFL of the low-pressure emergency core cooling systems are then operated (LPFL 20 operate). Consequently, the water level in the nuclear reactor increases. The operable low-pressure emergency core cooling systems in this case are two systems, i.e. LPFL 42A, 42B in the sections I and III. The water level in the nuclear reactor becomes the lowest when these two LPFL's are in operation (two LPFL 51 operate), and is slightly lower than the top of effective heat generating portion of the core 9. However, the integration of the nuclear reactor is not adversely affected at all. The broken line in FIG. 6 shows the transient of the nuclear reactor water level in the conventional core cooling systems in the case where a pipe for a LPFL, a low-pressure emergency core cooling system is broken. When a pipe for a LPFL system is broken, the nuclear reactor is automatically scrammed and isolated, and the cooling water in the reactor pressure vessel 7 blow down from a brak pipe. The elevation of a water injection ports, which are in the interior of the reactor pressure vessel 7, of HPCS's is lower than that of the injection ports therein of LPFL's. Therefore, the time during which the water level in the nuclear reactor becomes to lower than the elevation of the water injection port of the broken LPFL pipe decreases, so that this water injection port of the LPFL is exposed to the vapor earlier. Accordingly, the start of depressurization in the reactor pressure vessel 7 is occurred earlier. This causes an increase in the water level in the nuclear reactor due to the flushing by depressurization of the cooling water to start earlier, and the decrease of the water level in the nuclear reactor to start later. Since the water level in the nuclear reactor starts decreasing later, the starting time of the operations (HPCS 50 operates) of HPCS is also delayed. However, since the pressure in the reactor pressure vessel 7 decreases early, the flow rate of the cooling water injected into the reactor pressure vessel 7 after the starting of the operations of HPCS becomes increase. After all, the water level in the nuclear reactor is kept higher than that therein at the case of occurrence of the breakage of a pipe for a HPCS shown in FIG. 5. As is understood from FIGS. 5 and 6, the water level in the nuclear reactor at the case of occurrence of the HPCS pipe break in the conventional emergency core cooling structure is more decrease than the case of LPFL pipe break, and there is the possibility that the case of HPCS pipe break becomes the severest accident on the nuclear reactor. The conventional emergency core cooling apparatus has the highest safety-retaining performance amount the currently-available nuclear power plants, and is capable of maintaining the integration of a nuclear power plant. The characteristics of the conventional emergency core cooling apparatus reside in that a high-pressure emergency core cooling system is provided in each section thereof with two systems of HPCS provided, which furnish the high-pressure emergency core cooling systems with the core-spraying functions so that the cooling of the core can be done securely, while the core is uncovered, in all operational regions from an operational region in which the pressure in the reactor pressure vessel 7 is high to an operational region in which the pressure in the reactor pressure vessel 7 is low. As mentioned above, the conventional emergency core cooling apparatus secures the safety of a nuclear power plant sufficiently. However, it is most desirable that such a nuclear power plant be developed that is capable of preventing the water level in the nuclear reactor from decreasing below the top of effective heat generating portion of the core no matter what kind of accident occurs in the plant. The present inventors made a study of an emergency core cooling apparatus, which is capable of solving the above-mentioned newly-discovered problems, from various aspects to complete an emergency cooling apparatus capable of securing perfect safety, and having excellent core cooling capability and the first characteristics mentioned above. The present inventors discovered new problems, which will be described as follows, of a conventional apparatus of this kind. In the conventional emergency core cooling apparatus, the heat exchangers 43 provided in the low-pressure emergency core cooling systems, i.e. LPFL's 42A-42C function as residual heat removing systems. In order to cool the core when the nuclear reactor is stopped under normal conditions, the cooling water in the portion of the interior of the pressure vessel which is on the outer side of the core shroud is supplied to the heat exchangers 43 to cool the same, and the cooling water is thereafter returned to the same portion of the interior of the pressure vessel. However, the ports, from which the cooling water supplied to the heat exchangers 43, is taken out, of the pressure vessel, and the ports, from which the cooling water discharged from the heat exchangers is returned to the pressure vessel, thereof are provided close to each other. In order to improve the cooling water-cooling efficiency, large-capacity heat exchangers 43 are used. The reduction of the capacity of this heat exchanger serves to miniaturize the emergency core cooling apparatus. The present inventors' discussion about an apparatus of this kind from this point of view led the invention of the emergency core cooling apparatus having the second characteristics mentioned above. An embodiment of the present invention, which was made on the basis of the results of this discussion, will now be described. A preferred embodiment of the emergency core cooling apparatus according to the present invention applied to a boiling water reactor will now be described with reference to FIGS. 2, 3 and 4. First, the construction of the inner side of a reactor containment vessel will be described. A reactor containment vessel 1 has a drywell 2 and a pressure suppression chamber 3 filled with cooling water 4. A reactor pressure vessel 7 is provided in the drywell 2 and set on a pedestal 5. The pressure suppression chamber 3 surrounds the circumference of the pedestal 5. A vent passage 6 is provided in the pedestal 5. The upper end of the vent passage 6 is opened in the drywell 2, and the lower end portion of the vent passage 6 in the cooling water 4 in the pressure suppression chamber 3. A core 9 is set within a core shroud 8 provided in a reactor pressure vessel 7. An internal pump 10 for supplying cooling water to the core 9 is provided on the lower portion of the reactor pressure vessel 1. When the internal pump 10 is driven, the cooling water in an upper plenum 11, which is formed in the portion of the interior of the reactor pressure vessel 7 which is on the outer side of the core shroud 8, is supplied to the core 9. This cooling water is heated by the core 9 to turn into steam. The steam is sent from the reactor pressure vessel 7 to a turbine (not shown) through a main steam pipe 12. The steam discharged from the turbine is condensed in a condenser (not shown) to turn into water, and this water is supplied to the upper plenum 11 in the reactor pressure vessel 7 through feed water pipes 13A, 13B. The main steam pipe 12 is provided in the portion thereof which is within the drywell 2 with a main steam isolating valve 65. The boiling water reactor constructed as mentioned above has as emergency core cooling systems two systems of high-pressure core flooding apparatus (which will hereinafter be referred to as HPFL's) 14A, 14B, two systems of low-pressure core spray apparatus (which will hereinafter be referred to as LPCS's) 17A, 17B, one system of HPCI 27, and one system of LPFL 30. HPFL's 14A, 14B and HPCI 27 are high-pressure emergency core cooling systems, and LPCS's 17A, 17B and LPFL 30 low-pressure emergency core cooling systems. HPFL 14A has a HPFL pipe 15A by which the pressure suppression chamber 3 and the reactor pressure vessel 7 are connected, and a HPFL pump 16A provided in the HPFL pipe 15A. HPFL 14B also has a HPFL pipe 15A and a HPFL pump 16A as HPFL 14A. The HPFL pipes 15A, 15B are opened in the upper plenum 11. LPCS 17A consists of a LPCS pipe 18A by which the pressure suppression unit 3 and a core spray header 21 provided in the reactor pressure vessel 7 are connected, a LPCS pump 19A provided in the LPCS pipe 18A, and a heat exchanger 20A provided in the portion of the LPCS pipe 18A which is on the downstream side of the LPCS pump 19A. The core spray header 21 is provided at the portion of the interior of the core shroud 8 which is above the core 9. The LPCS pipe 18A extends through the wall of the reactor pressure vessel 7 and core shroud 8 to be joined to the core spray header 21. LPCS 17B consists of a LPCS pipe 18B, a LPCS pump 19B and a heat exchanger 20B as LPCS 17A. The heat exchangers 20A, 20B are coolers. The suction pipes 26A, 26B are connected via valves 33A, 33B to the portions of the LPCS pipes 18A, 18B which are on the upstream side of the LPCS pumps 19A, 19B. The spray headers 22A, 22B are provided at the upper portions of the interior of the pressure suppression chamber 3. The spray headers 22A, 22B are connected via pipes 23A, 23B to the portions of the LPCS pipes 18A, 18B which are on the downstream side of the heat exchangers 20A, 20B. The valves 63A, 63B are provided in the pipes 23A, 23B, respectively. The spray headers 24A, 24B provided at the upper portion of the interior of the drywell 2 are connected to the LPCS pipes 18A, 18B via pipes 25A, 25B. The valves 64A, 64B are provided in the pipes 25A, 25B, respectively. HPCI 27 has a HPCI pipe 28 by which the pressure suppression chamber 3 and feed water pipe 13B are connected to each other, and a HPCI pump 29 provided in the HPCI pipe 28. This HPCI pump is connected to a turbine which is driven by the steam introduced from the reactor pressure vessel 7. LPFL 30 has a LPFL pipe 35 by which the pressure suppression chamber 3 and feed water pipe 13A are connected to each other, a LPFL pump 31 provided in the LPFL pipe 35, and a heat exchanger 32 provided in the portion of the LPFL pipe 35 which is on the downstream side of the LPFL pump 31. The heat exchanger 32 is a cooler. The positions of the cooling water discharge ports, which are in the upper plenum 11, of the HPFL pipes 15A, 15B are set higher than that of the core spray header 21, i.e. the positions of the cooling water discharge ports, which are in the reactor pressure vessel 7 of LPCS's 17A, 17B. The position of a feed water header, i.e. the position of a cooling water discharge port, which is in the reactor pressure vessel 7, of HPCI 27 is also set higher than that of the core spray header 21. The emergency core cooling apparatus has three diesel-engine generators 37A, 37B, 37C as emergency power sources so that, even when the driving power source in normally use fails, the structure can continue to display its performance normally. The pumps 16A, 19A in HPFL 14A and LPCS 17A are connected to the diesel generator 37A by an electric cable 68A so that these pumps 16A, 19A are driven by the diesel generator 37A in an emergency. The diesel generator 37B is connected to the motors (not shown) for the pumps 16B, 19B in the HPFL 14B and LPCS 17B by an electric cable 68B, and constitutes an emergency power source for driving these pumps. The pump 31 in LPFL 30 is connected to an electric cable 68C and driven by the remaining diesel generator 37C in an emergency. The pumps 16A, 16B, 19A, 19B, 31 are motor-driven pumps. The pump 29 is a turbine-driven pump. When a valve 66 is opened, steam is supplied to a turbine 29A, which is connected to the pump 29, via a pipe 67. The pipe 67 is connected to the portion of the main steam pipe 12 which is on the upstream side of the main steam isolation valve 65. While the pump 29 is driven, the main steam isolation valve 65. The emergency core cooling apparatus is divided into three sections relatively to the three emergency diesel-engine generators as shown in FIG. 3. A section I includes HPFL 14A and LPCS 17A, a section II HPFL 14B and LPCS 17B, and a section III HPCI 27 and LPFL 30. Each section includes one system of high-pressure emergency core cooling apparatus and one system of low-pressure emergency core cooling apparatus. The discharge pipe and ADS will now be described in detail with reference to FIG. 4. The discharge pipe 60 is connected to the main steam pipe 12 via a relief valve 61. The other end of the discharge pipe 60 is opened in the cooling water 4 in the pressure suppression chamber 3. A pressure gauge 38 for measuring the pressure P (in the reactor containment vessel 1) in the drywell 2 is provided on the reactor containment vessel 1. A water level gauge 39 for measuring the water level L in the reactor in the reactor pressure vessel 7 is provided therein. A controller 62 is adapted to receive output signals P and L from the pressure gauge 38 and water level gauge 39, and open a relief valve 61 when the pressure P and water level L have exceeded predetermined levels. The ADS consists of the pressure gauge 38, water level gauge 39, controller 62 and relief valve 61. The relief valve 61 is provided with a spring. It is adapted to be opened in accordance with an output signal from the controller 62, and also like a safety valve when the pressure in the reactor pressure vessel has exceeded a predetermined level. When the breakage of a pipe occurs, HPFL's 14A, 14B are operated at a point in time, at which the pressure in the reactor pressure vessel 7 is high, immediately after the occurrence of the accident, with the HPFL pumps 16A, 16B driven to thereby inject the cooling water 4 from the pressure suppression chamber 3 into the upper plenum 11. During this time, HPCI 27 and LPFL 30 are also operated with the HPCI pump 29 and LPFL pump 31 driven to thereby inject the cooling water from the pressure suppression chamber 3 into the upper plenum 11 via the feed water pipes 13B, 13A. The cooling water 4 injected by these systems into the upper plenum 11 flows down in a clearance between the wall of the pressure vessel 7 and core shroud 8 to reach a lower plenum 36 below the core 9. The cooling water is collected in the lower plenum 36, and the core 9 is then flooded. In an emergency in which the breakage occurs in a pipe connected to the reactor pressure vessel 7, the LPCS's 17A, 17B are operated with the LPCS pumps 19A, 19B driven after the pressure in the reactor pressure vessel 7 has decreased to a predetermined level after the starting of the HPFL's 14A, 14B, to supply the cooling water in the pressure suppression chamber 3 to the core spray header 21 via the LPCS pipes 18A, 18B. The cooling water thus introduced into the spray header 21 through the LPCS pipes 18A, 18B is discharged in the core shroud 8 from a spray nozzle (not shown) provided in the header 21 toward the core 9. During this time, the valves 34A, 34B are open, while the valves 33A, 33B are closed. The cooling water 4 is cooled by the heat exchangers 20A, 20B while it flows in the LPCS pipes 18A, 18B. The cooling water cooled by the heat exchangers 20A, 20B is sprayed in such an emergency as mentioned above from the core spray header 21 into the core 9. Consequently, the cooling of the core 9 is promoted after the pressure decrease in the reactor pressure vessel 7. The cooling water discharged from the heat exchangers 20A, 20B can be sprayed as necessary from the spray headers 22A, 22B into the suppression chamber 3 and also from the spray headers 24A, 24B into the drywell 2 by opening the valves 63A, 63B, 64A, 64B. In an emergency in which a pipe is broken to cause the high-pressure and low-pressure emergency core cooling systems to be operated, the nuclear reactor is scrammed. When the breakage of a pipe occurs, HPFL and HPCI are operated from the time at which the pressure in the reactor pressure vessel is high, and LPCS and LPFL at the time at which the pressure in the reactor pressure vessel 7 has decreased to a level which is lower than a certain low level. LPCS's 17A, 17B function not only in such an emergency as mentioned above but also when the nuclear reactor is stopped (while the nuclear reactor is stopped) under normal conditions for carrying out the maintenance and inspection of the nuclear power plant and the replacement of the fuel. When the nuclear reactor is stopped under normal conditions, the valves 33A, 33B are opened, while the valves 34A, 34B and the valves 63A, 63B, 64A, 64B provided in the pipes 23A, 23B, 25A, 25B are closed. The LPCS pumps 19A, 19B are driven with these valves in the mentioned state. The high-temperature cooling water in the upper plenum 11 is supplied to the heat exchanger 20A via the suction pipe 26A and LPCS pipe 18A, and into the heat exchanger 20B via the suction pipe 26B and LPCS pipe 18B, to be cooled by these heat exchangers. The cooling water cooled by the heat exchangers 20A, 20B is introduced into the core spray header 21 by the LPCS pipes 18A, 18B and discharged therefrom into the portion of the interior of the shroud 8 which is above the core 9. The low-temperature cooling water thus discharged flows down as it cools the core 9. While the cooling water flows down through the core 9, the temperature thereof increases. The cooling water having such an increased temperature flows up through an annular clearance (a part of the upper plenum 11) formed between the wall of the pressure vessel 7 and core shroud, via the lower plenum 36, and enter the suction pipes 26A, 26B. During this time, the valves 63A, 63B, 64A, 64B are closed. As described above, while the nuclear reactor is stopped under normal conditions, the cooling water in the reactor pressure vessel 7 is circulated in a closed loop which connects together the upper plenum 11, suction pipe 26A, LPCS pump 19A, heat exchanger 20A, core spray header 21, core 9, lower plenum 36 and upper plenum 11 (and upper plenum 11, suction pipe 26B, LPCS pump 19B, heat exchanger 20B, core spray header 21, core 9, lower plenum 26 and upper plenum 11). Therefore, the cooling water cooled by the heat exchangers 20A, 20B is necessarily introduced into the core 9, and the cooling water, which has passed through the core 9, into the heat exchangers 20A, 20B. Accordingly, the core 9 can be cooled efficiently for a long period of time after the nuclear reactor is stopped under normal conditions. Moreover, since the high-temperature cooling water discharged from the core 9 is introduced into the heat exchangers 20A, 20B, the cooling efficiency of the heat exchangers 20A, 20B can be improved, and each of the heat exchangers can be made compact. The suction pipes 26A, 26B may be connected to the bottom portion of the reactor pressure vessel 7 so as to be directly communicated with not the upper plenum 11 but the lower plenum 36. When the HPFL pipe 15A in the section I is broken with the diesel-engine generator in the section II failing, HPCI 27 is left as an operable high-pressure core cooling system. The variations in the water level in the nuclear reactor after the occurrence of the breakage of the HPFL pipe 15A under such conditions are shown by a solid line in FIG. 6. FIG. 6 shows comparatively by a broken line the variations in the water level in a nuclear reactor, which are recorded after the breakage of a pipe in the LPFL system in the above-mentioned conventional emergency core cooling apparatus of this kind occurred. The water level (solid line) in the nuclear reactor, to which this embodiment is applied, in an emergency in which the breakage of a pipe in LPFL occurs is restored to a normal level earlier under the above-mentioned conditions as compared with the water level (broken line) in a nuclear reactor to which the conventional emergency core cooling apparatus is applied, for the following reasons. The number of the high-pressure emergency core cooling system to be operated in the present invention is less than that in the conventional emergency core cooling apparatus (Conventional apparatus: 2 systems, Embodiment of the present invention: 1 system). Therefore, in the present invention, the ADS, which is adapted to be operated at a water level in the nuclear reactor, which is lower than the water level at which the high-pressure emergency core cooling system is operated, is operated (ADS 52 operates), and two (one system in the conventional structure) low-pressure emergency core cooling systems (LPCS 17A and LPFL 30) are operated early (LPCS and LPFL 53 operate). The variations in the water level in the nuclear reactor, which are recorded after the breakage of the LPCS pipe 18A in this embodiment occurred, are shown by a solid line in FIG. 5. If in this case the LPCS pipe 18A in the section I is broken with the diesel-engine generator in the section II failing, HPFL 14A and HPCI 27 are left as operable high-pressure emergency core cooling systems, and LPFL 30 alone as an operable low-pressure emergency core cooling system. FIG. 5 shows comparatively by a broken line the variations in the water level in a nuclear reactor, which are recorded after the breakage of the pipe 13 in the HPCS system in the above-mentioned conventional emergency core cooling apparatus of this kind occurred. A decrease in the water level (solid line) in the nuclear reactor in the embodiment of the present invention is suppressed under the above-mentioned conditions as compared with that (broken line), which is recorded after the breakage of the pipe in HPCS occurs in the nuclear reactor to which the conventional emergency core cooling structure is applied, since two high-pressure emergency core cooling systems in the present invention are operated (HPCI 48 and HPFL 54 operate) immediately after the occurrence of the breakage of a pipe. Consequently, the lowest water level in the nuclear reactor in this embodiment becomes not lower than the top of effective heat generating portion (TAF) of the core. According to this embodiment, the following effects can be obtained. (1) HPFL's are used as high-pressure emergency core cooling systems, and LPCS's as low-pressure emergency core cooling systems. Accordingly, the position of the cooling water injection ports, which are in the reactor pressure vessel, of the high-pressure emergency core cooling systems can be set higher than that of the cooling water injection ports, which are in the pressure vessel of LPCS's. This enables the following advantages to be obtained. (a) Even when the breakage of a pipe in a high-pressure emergency core cooling system occurs, which causes the severest conditions for restoring a normal water level to create in the conventional nuclear plant, the quantity of the cooling water discharged from the reactor pressure vessel can be minimized since the position of the cooling water injection ports of HPFL's is high. Moreover, since the water injection rate increases due to the early depressurization in the pressure vessel, the core cooling capability of the core cooling apparatus at the time of occurrence of breakage of a pipe improves greatly. (b) When a pipe in a low-pressure core cooling apparatus (LPCS) is broken, the position of the cooling water injection ports of LPCS's becomes low but, in this case, two high-pressure emergency core cooling systems start being operated. Accordingly, a satisfactory cooling water injection rate can be secured from a point in time which is immediately after the breakage of the pipe with the pressure in the reactor pressure vessel in a high level. Accordingly, the core cooling capability of the core cooling apparatus at the time of occurrence of breakage of a pipe improves greatly. (2) When the high-pressure emergency core cooling systems are used as high-pressure injection systems at the time occurrence of a nuclear reactor isolation phenomenon, not HPCS's but HPFL's are used. Therefore, the thermal fatigue of the core spray sparger can be avoided, and the safety of the nuclear reactor can be improved. (3) It is effective to use HPCS's for cooling the core in uncovered state. However, when HPCS's are used to cool the core in covered state, the injection of cooling water is to be done into the upper portion of the core against the flow of the core cooling water, so that the natural circulation cooling capability lowers. However, if HPFL's are used, the cold water is injected into the space on the outer side of the core shroud when the temperature and pressure in the pressure vessel are high. This causes the flow rate of the naturally-circulated cooling water and the sub-cooling degree to increase, and the core-cooling effect to be improved. According to this embodiment described above, the safety of the nuclear reactor can be greatly improved by merely changing the connection of the pipes in the emergency core cooling apparatus without changing at all the parts and construction of the conventional core, pressure vessel and emergency core cooling apparatus. (4) As previously mentioned, the core-cooling efficiency during the stoppage of the nuclear reactor under normal conditions can be improved, and the capacity (dimensions) of the heat exchangers (coolers) in the low-pressure emergency core cooling systems can be reduced. (5) Each of the three sections of this embodiment is provided with one emergency diesel-engine generator as mentioned previously, and also one system of high-pressure emergency core cooling apparatus and one system of low-pressure core cooling apparatus. This enables the safety of the nuclear reactor to be improved. (6) Each of the low-pressure emergency core cooling apparatuses in this embodiment has a cooler. Accordingly, even when the pressure in the reactor pressure vessel is low, in which occasion the low-pressure emergency core cooling apparatus is operated, i.e., even when the temperature in the reactor vessel is low, the core can be cooled efficiently with the low-temperature cooling water supplied from the cooler in the same cooling apparatus. The temperature in the pressure vessel is low since the pressure therein is low. Therefore, the thermal impact which the core spray header 21 receives, which is provided above the core, can be reduced greatly even when the low-temperature cooling water is supplied from the above-mentioned cooler to this spray header as compared with the thermal impact similarly occurring in the conventional apparatus of this kind in which the cooling water is supplied to the core spray header 21, which is in a high-temperature, high-pressure atmosphere, by the HPCS's 40A, 40B. According to the present invention, the effective heat generating portion of the core is not exposed no matter whatever pipe in the emergency core cooling apparatus may be broken. Some other characteristics of the present invention reside in the coolers, which can be made compact, in the low-pressure emergency core cooling systems, and the improved core-cooling functions, which are fulfilled during the stoppage of the nuclear reactor under normal conditions, of the emergency core cooling apparatus. |
claims | 1. A radiography apparatus equipped with a radiation source configured to irradiate radiation toward a subject, the radiography apparatus comprising:a light source configured to illuminate an irradiation field of the radiation with visible light; anda control board configured to:control lighting of the light source;limit a lighting time of the light source; anddistinguish a type of the light source connected to a device body,wherein the control board changes the lighting time based on a result of the distinguishing. 2. The radiography apparatus as recited in claim 1, wherein the control board is configured to detect that the light source is connected to the device body. 3. The radiography apparatus as recited in claim 1, wherein the control board is dedicated to the type of the light source for lighting the light source. 4. The radiography apparatus as recited in claim 1, wherein the control board is configured to limit a lighting time of the light source to prevent the radiography apparatus from exceeding a predetermined temperature. 5. A radiography apparatus equipped with a radiation source configured to irradiate radiation toward a subject, the radiography apparatus comprising:a light source configured to illuminate an irradiation field of the radiation with visible light; anda control board configured to:control lighting of the light source;limit a lighting time of the light source; anddistinguish a type of the light source connected to a device body,wherein the control board disables the lighting time limitation when the light source is distinguished as a semiconductor light source by a result of the distinguishing. 6. The radiography apparatus as recited in claim 5,wherein the control board detects that the light source is connected to the device body. 7. The radiography apparatus as recited in claim 5,wherein the control board is dedicated to the type of the light source for lighting the light source. 8. The radiography apparatus as recited in claim 5, wherein the control board is configured to limit a lighting time of the light source to prevent the radiography apparatus from exceeding a predetermined temperature. 9. A radiography apparatus equipped with a radiation source configured to irradiate radiation toward a subject, the radiography apparatus comprising:a light source configured to illuminate an irradiation field of the radiation with visible light; anda control board configured to:control lighting of the light source;limit lighting power of the light source; anddistinguish a type of the light source connected to a device body,wherein the control board changes the lighting power based on a result of the distinguishing. 10. The radiography apparatus as recited in claim 9,wherein the control board detects that the light source is connected. 11. The radiography apparatus as recited in claim 9,wherein the control board is dedicated to the type of the light source for lighting the light source. 12. The radiography apparatus as recited in claim 9, wherein the control board is configured to limit a lighting power of the light source to prevent the radiography apparatus from exceeding a predetermined temperature. 13. A radiography apparatus equipped with a radiation source for irradiating radiation toward a subject, the radiography apparatus comprising:a light source configured to illuminate an irradiation field of radiation with visible light; anda control board configured to:control lighting of the light source;limit lighting power of the light source; anddistinguish a type of the light source connected to a device body,wherein the control board disables the lighting power limitation when the light source is distinguished as a semiconductor light source by a result of the distinguishing. 14. The radiography apparatus as recited in claim 13,wherein the control board detects that the light source is connected. 15. The radiography apparatus as recited in claim 13,wherein the control board is dedicated to the type of the light source for lighting the light source. 16. The radiography apparatus as recited in claim 13, wherein the control board is configured to limit a lighting power of the light source to prevent the radiography apparatus from exceeding a predetermined temperature. |
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047330872 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate in detail the structure of an ion beam milling apparatus which is an ion beam treating apparatus according to one embodiment of the present invention. In the ion beam milling apparatus as shown in FIG. 1, an internal gear 10 and a plurality of rotary receiving plates 8 are provided on the bottom surface inside an inner wall 1A of a vacuum vessel 1 of the ion beam milling apparatus. Cooling pipes 1C are provided under the bottom surface outside the vacuum vessel 1. The internal gear 10 is secured by bolts 10A to the bottom surface inside the vacuum vessel 1. The internal gear 10 assumes the form of a cylindrical ring and has teeth formed on the inside thereof. A gear 8A is formed along the periphery of each rotary receiving plates 8 and is engaged with the internal gear 10. A spherical hole is formed in the upper portion of the rotary receiving plate 8. A wafer holding portion 7 is provided having at its lower end a spherical portion 7A and holding a wafer 19 at the upper end thereof. The spherical portion 7A is inserted in the spherical hole of the rotary receiving plate 8. The wafer 19 is mounted by a cover 18 on the wafer holding portion 7 which is supported by a tilted link 6. As shown in FIG. 2, the tilted links 6 are coupled by a pin 5A to the stays 5 that are radially fastened to a polygonal plate 4, through an oblong hole 6A formed in the tilted link 6. The polygonal plate 4 is mounted on an upper end 3A of a stepped shaft 3 via bearing means 3C and is allowed to rotate with respect to the stepped shaft 3. The stepped shaft 3 can be slidden up and down owing to bearing means 2C by an actuator 30. An upper end of a shaft 11 of the actuator 30 such as an air cylinder secured to the lower portion outside the vacuum vessel 1 is coupled to a lower end of the stepped shaft 3 through a horizontal link 13 using a pin 11A of the shaft 11 and a pin 3D of the stepped shaft 3. A stay 14 is attached to a lower portion outside the vacuum vessel 1 on the inside of the air cylinder 30. Oblong holes 13A and 13B are formed respectively in the right and left sides of the link 13 with a pin 14A of the stay 14 as a fulcrum. The pin 11A of the shaft 11 is inserted in the oblong hole 13A formed in the horizontal link 13, and the pin 3D of the stepped shaft 3 is inserted in the oblong hole 13B of the horizontal link 13. The rotary receiving plate 8 is supported, as shown in FIG. 3, by a hole 2H formed in a rotary disc 2. A compression spring means 9 is interposed between the rotary disc 2 and the rotary receiving plate 8 so that the rotary receiving plate 8 is pressed onto the bottom surface of the vacuum vessel 1. The rotary disc 2 having a boss 2A with a small diameter is allowed to rotate relative to the stepped shaft 3 owing to the bearing means 2C. The rotary disc 2 is further allowed to rotate relative to the vacuum vessel 1 owing to the bearing means 2F. Moreover, an O-ring 2D and a collar 2E is provided respectively between the stepped shaft 3 and the rotary disc 2. Owing to a gear 15 attached to the stepped shaft 3 and a gear 16 attached to the end of shaft of a motor 17, the rotary disc 2 transmits the rotation of the motor 17 to the tilted link 6 to turn the polygonal plate 4. The gear 15 is mounted on the outerface of the rotary disc 2 through a key 15A. As shown in FIG. 3, the tilted link 6 and the wafer holding portion 7 are combined together through a hole 6B formed in the tilted link 6. A projection 6C of the tilted link 6 and a projection 2J of the rotary disc 2 are coupled together by pulling spring means 20 to prevent the wafer holding portion 7 from floating when it is tilted. The wafer holding portion 7 and the rotary receiving plate 8 are contacted to each other along a spherical portion 7A. The spherical portion 7A is formed together with the wafer holding portion 7 at lower end thereof. In the spherical portion 7A of the wafer holding portion 7 is formed a groove 7B of a width H as shown in FIG. 4. A pin 8B with an outer diameter d.sub.1 fastened to the rotary receiving plate 8 is fitted into the groove 7B. The width H of the groove 7B is slightly greater than the outer diameter d.sub.1 of the pin 8B of the rotary receiving plate 8, so that the pin 8B of the rotary receiving plate 8 is allowed to slide in the groove 7B of the spherical portion 7A. The pin 8B is inserted by a depth l.sub.1 in the groove 7B which has an maximum depth L; i.e., the pin 8B is floated by l.sub.2. A tilting mechanism of this embodiment of the present invention is comprised of the connecting mechanism for transmitting the rotation of the rotary receiving plate 8 to the wafer holding portions 7, tilted links 6 for tilting the wafer holding portions 7, the polygonal plate 4 for coupling the tilted links 6, the shaft 3 being coupled to the tilted links 6 as an unitary structure and moving in the rotary disc 2, and moving means for moving the shaft 3, so that the distances are maintained equal between an ion source and the respective wafers 19. Namely, the respective wafers 19 on the wafer holding portions 7 are disposed on same circle line surrounding of the outersurface of the stepped shaft 3. The distances between the ion source and the respective wafers 19 are maintained equal. Accordingly, the ion beam emitted from the ion source irradiates uniformly the respective wafers 19 and treats uniformly the respective wafers 19. The respective wafers 19 are irradiated with the ion beam maintaining the uniform intensity. Operation of the above embodiment of the present invention will now be described. As shown in FIG. 1, first, if the actuator 30 moves in a direction e, the stepped shaft 3 is moved in a direction f, whereby the polygonal plate 4 moves in a direction g and the wafer holding portions 7 are outwardly tilted in a direction h due to the tilted link 6. Conversely, if the actuator 30 is moved in a direction a, the stepped shaft 3 moves in a direction b and the polygonal plate 4 moves in a direction c to assume the state indicated by a two-dot chain line, whereby the wafer holding portions 7 are inwardly tilted in a direction d due to the tilted link 6. When the turn in a direction i of the gear 16 produced by the motor 17 is transmitted to the rotary disc 2 via the gear 15, the rotary receiving plates 8 revolves in a direction j with the stepped shaft 3 as a center. At the same time, the rotary receiving plates 8 rotate in a direction k while revolving in the direction j, since they are in mesh with the internal gear 10 that is secured to the vacuum vessel 1. A relationship between the rotary receiving plates 8 and the wafer holding portions 7, when the abovementioned operation is being carried out, will be explained below in conjunction with FIGS. 5, 6 and 7. FIG. 5 illustrates the state where the wafer holding portions 7 are outwardly tilted and the grooves 7B of the spherical portions 7A are located on the outermost side. Due to the rotary disc 2, the rotary receiving plates 8 starts to rotate from this position, and the wafer holding portions 7 and the rotary receiving plates 8 rotate in synchronism due to the pin 8B of the rotary receiving plates 8. Namely, the wafer holding portions 7 starts to rotate in the direction k. FIG. 6 illustrates the state where the rotary receiving plates 8 are rotated by 90 degrees from the state of FIG. 5, and FIG. 7 illustrates the state where the rotary receiving plates 8 are further rotated by 180 degrees from the state shown in FIG. 5. Thus, the wafer holding portions 7 are allowed to rotate and revolve in the vacuum vessel 1 being tilted in any direction. As shown in FIG. 1, the wafer holding portions 7 can be maintained at any angle within a range of .+-..beta. degrees (usually .+-.30 degrees). According to this embodiment of the present invention, therefore, the respective or individual wafers are tilted, and are rotated and revolved maintaining the thus tilted angle. The distances between the respective wafers on the wafer holding portions and the ion source are maintained equal by the tilting mechanism. Therefore, the surfaces of the respective or individual wafer are irradiated with the ion beam maintaining the uniform intensity, making it possible to prevent adhesion of matter by sputtering and to prevent the affect of the secondary sputtering among the respective wafers. Accordingly, thin films for semiconductors can be finely patterned maintaining high precision. |
abstract | Radiation shields and radiation shielding systems for attenuating ionizing radiation include two or more attenuating elements, such as layers. The two or more attenuating elements may include different attenuating materials. The two or more attenuating elements may be configured to attenuate ionizing radiation differently than one another. In some embodiments, different attenuating elements may be configured for use with different energies or ranges of energies of ionizing radiation. The concurrent use of two or more layers or other attenuating elements may optimize the ability of a radiation shield to attenuating ionizing radiation. Systems and methods for attenuating ionizing radiation are also disclosed. |
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061880760 | abstract | Capillary discharge extreme ultraviolet lamp sources for EUV microlithography and other applications. The invention covers operating conditions for a pulsed capillary discharge lamp for EUVL and other applications such as resist exposure tools, microscopy, interferometry, metrology, biology and pathology. Techniques and processes are described to mitigate against capillary bore erosion, pressure pulse generation, and debris formation in capillary discharge-powered lamps operating in the EUV. Additional materials are described for constructing capillary discharge devices fore EUVL and related applications. Further, lamp designs and configurations are described for lamps using gasses and metal vapors as the radiating species. |
claims | 1. A flow diverter for diverting flow between cells of a spacer in a nuclear fuel bundle into the diverter and in a first downstream flow direction relative to the spacer, the spacer having a rectilinear array of cells, comprising: a cylindrical tube for overlying a spacer cell and having an axis extending in first and second opposite axial directions, a plurality of tabs projecting laterally from said cylindrical tube adjacent a first end portion thereof and at perpendicular locations relative to one another about said axis for disposition in the spacer between diagonally adjacent cells of the rectilinear array thereof; said tabs forming with said axis acute angles opening in the second axial direction for diverting flow through the spacer into said cylindrical tube in the first axial direction and toward the axis; and a vortex generator carried by said cylindrical tube adjacent a second end portion of said tube opposite said first end portion, said vortex generator including vanes extending from said tube in said first axial direction and spaced from said tabs for swirling the flow diverted through the cylindrical tube by said tabs. 2. A flow diverter according to claim 1 wherein said tabs are integral with the cylindrical tube. claim 1 3. A flow diverter according to claim 1 wherein said tabs have tips and arcuate side edges terminating in said tips, said side edges being arcuate for substantial conformance with arcuate side edges of diagonally adjacent spacer cells. claim 1 4. A flow diverter for diverting flow between cells of a spacer in a nuclear fuel bundle into the diverter and in a downstream flow direction relative to the spacer, the spacer having a rectilinear array of cells, comprising: a cylindrical tube for overlying a spacer cell and having an axis, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis for disposition in the spacer between diagonally adjacent cells of the rectilinear array thereof; said tabs forming with said axis acute angles for diverting flow through the spacer into said cylindrical tube; a vortex generator carried by said cylindrical tube and including vanes for swirling the flow diverted through the cylindrical tube, said vortex generator comprising a cylindrical tube portion having an axis generally coincident with the axis of said flow diverter, said vanes extending integrally from said cylindrical tube portion in an axial direction and extending inwardly from walls of said tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. 5. A flow diverter according to claim 4 wherein the tips of said vanes are welded to one another. claim 4 6. A flow diverter according to claim 5 wherein said vortex generator is removably mounted on said flow diverter. claim 5 7. A flow diverter according to claim 5 wherein said vortex generator comprises a second cylindrical tube having a plurality of locking projections, the first mentioned cylindrical tube having a plurality of slots therethrough for receiving said locking projections to releasably secure said second cylindrical tube and said first cylindrical tube to one another. claim 5 8. A flow diverter according to claim 7 wherein said projections comprise spring-biased tabs of the vortex generator. claim 7 9. A flow diverter according to claim 4 wherein said cylindrical tube portion includes a second cylindrical tube, said first and second tubes having complementary threads for releasably securing the first and second tubes to one another, said vanes extending inwardly in a direction tending to tighten the threads of said second cylinder on the threads of said first cylinder in response to flow through said vortex generator. claim 4 10. A flow diverter according to claim 1 wherein said vanes are twisted, said vanes lying within peripheral confines of said vortex generator tube. claim 1 11. A flow diverter according to claim 1 wherein said tabs are twisted to impart a swirl to the flow-diverted for flow through said tube. claim 1 12. A flow diverter according to claim 11 wherein said tabs have opposite edges, one edge being longer than an opposite edge. claim 11 13. A nuclear fuel bundle comprising: a plurality of full-length nuclear fuel rods and at least one part-length rod, said fuel rods extending generally axially along the fuel bundle; a plurality of spacers axially spaced from one another along the bundle, each said spacer having generally cylindrical side-by-side cells in cell positions arranged in parallel rows and parallel columns forming a generally rectilinear array of cells having parallel axes, certain of the cells of each spacer receiving the full-length fuel rods, one of said spacers spaced from an end of the part-length rod having an open cell in axial registration with the part-length rod; a flow diverter including a cylindrical tube overlying said open cell and connected to said one spacer, said tube having an axis generally coincident with the axis of said open cell, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally adjacent cells; said tabs forming with said axis acute angles opening in an upstream direction for diverting flow through openings between the cells of the spacer into said cylindrical tube; and a vortex generator carried by said cylindrical tube downstream of said tabs for swirling the flow diverted through the cylindrical tube. 14. A nuclear fuel bundle according to claim 13 wherein each of said tabs terminates in a tip extending beyond a straight line interconnecting centers of diagonally adjacent cells between which the tab projects. claim 13 15. A nuclear fuel bundle according to claim 13 wherein said tabs are integral with the cylindrical tube. claim 13 16. A nuclear fuel bundle according to claim 13 wherein said tabs have tips and arcuate side edges terminating in said tips, said side edges being arcuate and in substantial conformance with the arcuate side edges of said diagonally adjacent cells. claim 13 17. A nuclear fuel bundle according to claim 13 including four tabs perpendicular to one another about said cylindrical tube, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally pairs of cells, a cell of each pair of diagonally adjacent cells being common to an adjacent pair of diagonally adjacent cells between which a tab extends. claim 13 18. A flow diverter/spacer combination for diverting flow between cells of a spacer in a nuclear fuel bundle for flow within the diverter and in a downstream flow direction relative to the spacer, comprising: a spacer having generally cylindrical side-by-side cells in cell positions arranged in parallel rows and parallel columns forming a generally rectilinear array of cells, the cells having parallel axes; a cylindrical tube overlying a cell of and connected to the spacer and having an axis generally coincident with the axis of the cell, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally adjacent cells; said tabs forming with said axis acute angles opening in an upstream direction for diverting flow through openings between the cells of the spacer into said cylindrical tube; and a vortex generator carried by said cylindrical tube downstream of said tabs for swirling the flow diverted through the cylindrical tube; said vortex generator including a cylindrical tube portion having integral vanes extending axially in a downstream direction and curved inwardly from walls of said cylindrical tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. 19. A flow diverter/spacer combination according to claim 18 wherein the tips of said vanes are welded to one another. claim 18 20. A flow diverter/spacer combination according to claim 13 wherein said vortex generator is removably mounted on said flow diverter. claim 13 21. A flow diverter/spacer combination according to claim 20 wherein said vortex generator comprises a second cylindrical tube having a plurality of locking projections, the first mentioned cylindrical tube having a plurality of slots therethrough for receiving said locking projections to releasably secure said second cylindrical tube and said first cylindrical tube to one another. claim 20 22. A flow diverter/spacer combination according to claim 21 wherein said projections comprise spring-biased tabs of the vortex generator. claim 21 23. A flow diverter/spacer combination according to claim 18 wherein said cylindrical tube portion includes a second cylindrical tube, said first and second tubes having complementary threads for releasably securing the first and second tubes to one another, said vanes being curved inwardly in a direction tending to tighten the threads of said second cylinder on the threads of said first cylinder in response to flow through said vortex generator. claim 18 24. A flow diverter/spacer combination according to claim 13 wherein said vortex generator includes vanes extending axially in a downstream direction and twisted inwardly so that an edge of each vane lies adjacent the axis of said cell, said tabs and said vanes being formed integrally with said first cylindrical tube. claim 13 25. A flow diverter/spacer combination according to claim 13 wherein said tabs are twisted to afford a swirl to the flow diverted by the diverter and into the cylindrical tube. claim 13 26. A nuclear fuel bundle according to claim 13 wherein said vortex generator includes vanes integral with said cylindrical tube portion and extends axially in a downstream direction, said vanes being curved inwardly from walls of said cylindrical tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. claim 13 27. A flow diverter according to claim 1 wherein said vanes extend generally in said first axial direction and are twisted such that one edge of each vane lies inboard of said tube and another edge of each vane lies generally along the circumference of the tube. claim 1 28. A flow diverter according to claim 1 wherein said cylindrical tube has apertures in lateral registration with said tabs, respectively, for receiving the diverted flow. claim 1 29. A nuclear fuel bundle according to claim 13 wherein said cylindrical tube has apertures in lateral registration with said tabs, respectively, for receiving the diverted flow for flow in a downstream direction within the cylindrical tube. claim 13 30. A nuclear fuel bundle according to claim 29 wherein said vanes extend generally in said first axial direction and are twisted such that one edge of each vane lies inboard of said tube and another edge of each vane lies generally along the circumference of the tube. claim 29 |
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abstract | A focused ion beam apparatus, including: a specimen transferring unit having a probe to which a micro-specimen extracted from a specimen, can be joined through a joining deposition film, for transferring the micro-specimen to a sample holder; and wherein, the specimen transferring unit holds the probe which is joined through the joining deposition film to the micro-specimen extracted from the specimen, and the sample stage moves so that the sample holder mounted on the holder clasp is provided into an irradiated range of the focused ion beam, and the specimen transferring unit approaches the probe to the sample holder, and the gas nozzle supplies the deposition gas so that the micro-specimen is fixed to the sample holder through a fixing deposition film, and the ion beam irradiating optical system irradiates the focused ion beam to the micro-specimen fixed to the sample holder for various procedures. |
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description | The present application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional patent application Ser. No. 63/033,915 filed on Jun. 3, 2020, the disclosure of which is incorporated herein by reference in its entirety. The present patent application is a continuation-in-part (CIP) of U.S. non-provisional patent application Ser. No. 16/285,199 filed on Feb. 26, 2019, and claims priority to said U.S. non-provisional patent application under 35 U.S.C. § 120. This U.S. non-provisional identified patent application is incorporated herein by reference in its entirety as if fully set forth below. This present U.S. non-provisional patent application is related to previous U.S. patents by the same inventor related to the disposal of nuclear waste in deep underground formations, wherein these U.S. patents are: U.S. Pat. Nos. 5,850,614, 6,238,138, and 8,933,289; wherein the disclosures and contents of which are incorporated herein by reference in their entireties as if fully set forth below. The present invention relates in general to disposing of nuclear and/or radioactive materials (waste) and more particularly, to: (a) drilling and under reaming operations to develop an array of specialized underground human-made caverns for receiving the nuclear/radioactive waste; (b) utilization of the specialized human-made caverns implemented in deep geological formations, such that, the nuclear/radioactive waste is disposed of safely, efficiently, and economically; and (c) operations of the nuclear/radioactive waste disposal. The present invention relates specifically to containment, storage, and/or disposal of nuclear and/or radioactive materials within an array of human-made subterranean cavities within deep geological formation(s) which are formed beneath a grid pattern located on the surface of the Earth. A portion of the disclosure of this patent application may contain material that is subject to copyright protection. The owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights whatsoever. Certain marks referenced herein may be common law or registered trademarks of third parties affiliated or unaffiliated with the applicant or the assignee. Use of these marks is by way of example and should not be construed as descriptive or to limit the scope of this invention to material associated only with such marks. Today (e.g., circa 2020) there is a massive quantity of highly dangerous nuclear waste accumulating across the world. In the United States (U.S.) alone there are more than 80,000 metric tons (MT) of high-level solid nuclear waste (HLW) being stored in cooling pools and in concrete casks on the surface of the Earth. These existing surface operations are very costly, typically costing hundreds of millions of dollars annually. And these existing surface operations were never intended for the long-term disposal of HLW. The HLW is generally called spent nuclear fuel (SNF) and often consists of thousands of nuclear fuel assemblies which have been removed from operating nuclear power plants. These SNF fuel assemblies are highly radioactive and also thermally active and continue to generate sensible heat which must be safely removed by maintaining these assemblies in cooling tanks at the onsite surface storage sites. There are approximately 90,000 individual fuel assemblies being stored today in the U.S. and about 2,500 MT being added annually. There is a significant need for new mechanisms and processes to safely get rid of the surface storage of this radioactive waste and to sequester this SNF waste in a safe manner. In this patent application HLW and SNF may be used interchangeably to describe the solid nuclear waste product. In the U.S., the nuclear weapons production industry has left a massive and devastating legacy when the nuclear reactors were decommissioned at the end of the Cold War. For example, the nuclear weapons manufacturing process left behind about 53 million U.S. gallons (volumetric equivalent of about 800,000 cubic meters [m3]) of high-level radioactive waste stored within 177 storage tanks. In addition, 25,000,000 cubic feet (ft3) (710,000 m3) of solid radioactive waste and a resulting contamination zone covering several square miles of contaminated groundwater beneath the site. Much of this liquid waste has been leaking into the surrounding earth creating significant health and environmental problems. There is a tremendous safety and environmental need to store and/or dispose of such radioactive materials. Some attempts have been made in the past to solve these problems of the safe and cost-effective long-term disposal of nuclear/radioactive waste materials. Most major countries with nuclear power generating systems and nuclear weapons programs, have made plans to safely sequester the nuclear waste. For example, currently, Sweden, U.S., France, Canada, Germany, and Russia are contemplating various means of nuclear waste disposal. In the past, it has been challenging, dangerous, and expensive to try to store radioactive and/or nuclear materials (such as waste materials) in underground caverns except for those cases where solid quantities of material are stored in barrels, individual capsular containers, slurry material, open pits and also within shallow mines which are generally very close to the surface of the Earth. There has not been any attempt to store radioactive materials in very deep caverns because: (a) such deeply located caverns do not generally naturally exist in rock formations at very great depths; and (b) in the past it has been impossible to fabricate or produce large diameter deep human-made caverns or to implement them in deep enough geological formations which are necessary to maintain a level of safety such that there would be no migration of radionuclides from the radioactive materials to the surface of the Earth over geologic time scales. However, underground human-made caverns have been used to store natural gas, hydrocarbon liquids, waste-water, petroleum products, and other commercial products for many decades. These caverns have generally been drilled into and/or leached from subsurface salt domes or salt formations which have been formed over geologic time by salt intrusions or depositions from regional seas or other long-gone aqueous environments. Operationally, human-made caverns, located in a given salt formation, are typically created by injecting fresh water into subterranean salt formations and leaching and withdrawing the resulting brine. This process is referred to as solution mining. Over time, numerous human-made salt caverns have been solution mined by the petroleum industry for use in storing hydrocarbons like the Strategic Petroleum Reserve which holds hundreds of millions of barrels of crude oil; and for disposing of nonhazardous oilfield wastes (NOW). To date (circa 2020), human-made caverns located in salt formations have not been used to store and/or dispose of radioactive materials due to concerns that such caverns may leak radioactive materials into surrounding rocks and, perhaps, into freshwater aquifers. Additionally, in underground gas storage operations, it has been demonstrated that over time the cyclic injection-production operations of the natural gas with the cycling of pressures inside the salt dome can create “salt creep” in which the human-made cavern within the given slat formation becomes progressively smaller in volume and eventually useless for large storage purposes. Some better, more permanent mechanisms are needed for radioactive material storage and disposal other than human-made caverns within salt formations. Today (2020) many political entities and nations are focused on the use of some sort of subterranean tunneling systems to dispose of the HLW waste. For example, Sweden, Canada, United States, and France all have at least partially developed massive HLW disposal systems that are conceived to be implemented in relatively shallow rock zones in underground mining type environments. For example, FIG. 1, FIG. 2, and FIG. 3, show three such prior art HLW disposal systems based on mining technologies and mining environments in relatively shallow underground rock zones. FIG. 1 shows an overview of a prior art underground nuclear waste disposal system as contemplated for Sweden. FIG. 2 shows an overview of a prior art underground nuclear waste disposal system as contemplated for Canada. FIG. 3 shows an overview of a prior art underground nuclear waste disposal system as contemplated for Yucca Mountain (Mt.) in the (U.S.). Sweden is the farthest along in implementing its technology as of 2020. The U.S. FIG. 3 system has been on the drawing board since 1978 and it is now “temporarily” shut down. A specific example of the prior art may be seen in the Sweden model for HLW waste disposal as shown in FIG. 1. This FIG. 1 disposal system is an estimated to cost $15.7 Billion USD to build out. This FIG. 1 disposal system is an underground mining tunneling system in which a series of approach tunnels 11, transport tunnels 11, staging areas, and deposition tunnels 14 are drilled (carved/mined out) into the disposal formation 12 with large complex mining tunneling equipment. This FIG. 1 disposal system project is estimated to occur over a 30-year time horizon. This FIG. 1 disposal system's basic design concept contemplates disposing the spent nuclear fuel (SNF and/or HLW) in graphite, copper cast-iron canisters that are emplaced in crystalline rock at depths of around 500 meters (i.e., about 1,640 feet). These graphite cast-iron canisters are supposed to have an outer layer that is 15 millimeters (mm) thick and encased in a corrosion barrier composed of copper metal. After filling these canisters with the SNF/HLW, they are sealed, and then these copper cast-iron canisters are to be emplaced individually in vertical boreholes in the floors of the deposition tunnels 14 which have been excavated off of the central delivery tunnels 11 which are implemented in the disposal system. The spaces between the copper cast-iron canisters and the walls of the boreholes are to be filled with compacted bentonite. The tunnels 14 and shafts 14 will be backfilled with bentonite material that is made of compacted granite blocks and pellets, along with ceiling plugs which are put in place to block specific transport pathways 11 from ground water and/or from radionuclides. Additionally, or alternatively, Sweden also can utilize the horizontal placement of “super” containers in their disposal system. The super containers are of a copper canister surrounded by a pre-compacted bentonite blocks in an outer metal shell. The function of the canister in both designs is to isolate SNF/HLW from the surrounding environment. The design lifetime of the Sweden canister is expected to be at least 100,000 years. In addition to the required chemical resistances, the canisters must also have sufficient mechanical strength to withstand the hydraulic pressures within the system at a depth of 700 meters (m). In order to meet these requirements, the canisters have been designed with an insert that provides mechanical strength for the SNF/HLW fuel assemblies in fixed positions. The outer copper shell provides corrosion protection for the canister. This outer shell is made of oxygen free copper to improve the creep strength and creep ductility of copper, wherein 30 to 100 parts per million (ppm) of phosphorus is added to this oxygen free conductive copper. This FIG. 1 system is complex, expensive, dangerous, and difficult to implement with operating personnel and equipment underground working with radioactive materials for several years. Most of the prior art current methods which are contemplated for the storage of HLW (and/or SNF) waste by these countries (and other similar countries) have generally comprise the following types of features. They generally have a very large surface footprint which is almost the size of a small town or massive mining type field operation, which is setup above the Earth's surface to allow the for the underground mining operations, electric power generation and distribution systems, living quarters for personnel, transport and protected temporary storage facilities for the development of the underground disposal systems. Generally, these types of massive surface developments meet strong and concerted public resistance which is difficult to overcome and which creates almost impossible problems (e.g., “not in my backyard [NIMBY]) leading to unfinished projects (e.g., the FIG. 3 Yucca Mt. project). Further, these prior art underground disposal systems usually have implemented the very long underground approach tunnels 11 to reach the disposal tunnels 14. The long approaches 11 are often spirally designed to allow the tunnels 11 to reach into the rock zones 12 without having very dangerous and steep grades or route system to allow vehicular traffic or rail traffic. In addition, these prior art underground disposal systems have large underground, protected staging or “cathedral like” areas for storage of the HLW waste material underground before final emplacement. The length and large diameters of the approach tunnels 14 and the large cathedral like staging areas are all expensive to build and maintain, and vulnerable to collapse. In addition, all these prior art underground disposal systems would involve some sort of protective canister type systems for housing the SNF/HLW, which are designed to be structurally protective and also protective of radionuclide transport over the short and long term. These storage containers are also designed with massive shielding for corrosion against also radionuclide transmission and also for structural integrity. These prior art canisters have been designed to mitigate corrosion. These prior art canisters are designed to be the first line of defense for the waste process. This type of corrosion protective approach is short sighted since corrosion over millenia is a complex and incompletely understood phenomenon. Disposal times should be measured in hundreds of thousands of years. By focusing herein on the deep formation storage/disposal approach, the primary protective system is the deeply located rock formation itself. The deep geological formation contemplated herein is closed, impermeable, massive, and remote from any corrosion producing environment processes like oxidizers, surface waters or chemical contaminants. Such deep geological formations, as contemplated herein, as radioactive waste depositories thus provide a much better solution. Finally, these prior art underground disposal systems are designed to have some sort of continual surface monitoring system designed for thousands of years, at entry points to protect the public from radiation and also to prevent pilferage of the radioactive waste materials. Pilferage of nuclear waste material from a mine may be easily done unless the mine is completely isolated by massive earthen deposits. However, given the shallowness of these prior-art systems, alternate re-entry may be established by a determined agent using well camouflaged surface operations. Whereas, in contrast, pilferage from a deep wellbore in a geologically deep disposal formation, as contemplated herein, is almost impossible, particularly after the wellbore and/or the human-made cavern have been sealed. Pilferage from a deep wellbore in a geologically deep disposal formation requires a massive, easily detectable drilling rig operating for at least several months. Finally, the chance of radiation from a radioactive waste source buried tens of thousands of feet in a closed geological formation in steel casings, as contemplated herein, is infinitesimally small or non-existent. In addition, some prior art disposal systems implement “drip” shields made of expensive titanium metal to cover in an umbrella-like fashion to protect the waste canisters from percolating rainwater from the surface or inflow from the water table. The inclusion of these titanium drip shields requires significant additional underground structural additions to the disposal infrastructure to support the shields. These support structures for shields have to be emplaced prior to inclusion of the titanium shields. In addition, operationally, the inclusion of the titanium shields may have to be done after the deposition of total repository waste has been completed. This may mean a waiting period of about 30 years before shields are implemented. Because of these problems, it would be desirable to have a HLW/SNF disposal system that does not require such drip shields. Also, siting the disposal system in a deep geological formation, as illustrated herein, precludes the need for any type drip shield because there is no surface water migration (dripping) in these deep repository zones. A need, therefore, exists for new systems and/or methods for the safe and cost-effective disposal of radioactive wastes in a controlled manner along with depositing these radioactive wastes into deeply located receiving volumes that are designed to meet the requirements of public acceptance along with regulatory guidelines. For example, and without limiting the scope of the present invention, some embodiments of the present invention may be systems and/or methods for the disposal of nuclear and/or radioactive materials by: (a) implementing an array of large human-made caverns, beneath a grid pattern on the surface of the Earth, wherein the human-made caverns are located within at least one deep geological formation; (b) preparing the nuclear and/or radioactive materials for disposal and then disposing (e.g., loading) of the nuclear and/or radioactive materials into the array of the human-made caverns; and (c) sealing these deeply located human-made caverns, that contain the nuclear and/or radioactive materials, to prevent migration and contamination of the outside environment. The grid pattern on the surface of the Earth may have a significantly smaller surface footprint than that of the footprints of the prior art, particularly in light of how much nuclear/radioactive waste may be disposed of per the size of the given surface footprint; i.e., the systems and method contemplated herein may dispose of significantly more nuclear/radioactive waste than the prior art while using a significantly smaller surface footprint (grid pattern). Further, the nuclear and/or radioactive materials may be fixed in specialized protective media environments within the given human-made caverns. Because the array of the sealed/closed human-made caverns, with the nuclear and/or radioactive materials, are located within the deep geological formation, the nuclear and/or radioactive materials are safely sequestered from people, outside environments, and the ecosphere in general. It is to these ends that the present invention has been developed. To minimize the limitations in the prior art, and to minimize other limitations that will be apparent upon reading and understanding the present specification, embodiments of the present invention may describe devices, machines, equipment, mechanisms, means, systems, methods, portions thereof, and/or combinations thereof for the storage and/or the disposal of nuclear/radioactive materials within a “close” packed array of multiple human-made subterranean cavities, wherein such human-made caverns are located within at least one deep geological formation, and wherein the array of human-made caverns are located directly below a grid pattern located on the surface of the Earth. In some embodiments, the grid pattern may comprise a plurality of grids and at least one of those grids may comprise at least one drill site, wherein it may be from such drill sites that a given human-made cavern may be located beneath. In some embodiments, “close” packing may mean a given grid selected from the grid pattern may have a dimension of about twenty (20) feet to about 100 feet. In some embodiments, adjacently located human-made caverns may be from about twenty (20) feet to about 100 feet apart. Briefly, the disposal systems and/or methods in accordance with some embodiments of this invention may achieve the intended objectives by including steps of: drilling substantially vertical pilot wells (wellbores) according to a preset grid pattern located on the surface of the Earth, wherein these substantially vertical wellbores intersect at least one deep geologic formation that is located directly below the grid pattern; and creation of an array of human-made cavern within that deep geological formation, using under reaming from distal/terminal portions of the substantially vertical wellbore. In addition, the systems and/or method may be designed to allow geometry and/or conditioning of the human-made caverns to be controlled, so that the life of the human-made caverns as a safe repository for nuclear waste can be maximized. In recent years, in the oilfield drilling industries, over 2,500,000 feet of under-reaming drilling has been successfully achieved. The reaming technology in oil well drilling is not new. Reaming patents exist as early as 1939. However, the recent technological developments in the oil filed drilling industries have made it possible to help resolve the problems involved in making human-made caverns a reality in deep geologic zones, which was previously not technically feasible. Furthermore, today (2020) oilfield drilling rigs have been modified and automated to allow a massive rig capable of lifting millions of pounds to automatically “walk” or “skid” itself across the surface of the Earth, over the ground in multiple directions, of a given oilfield. These “walking” drill rigs may be used to form the array of human-made caverns contemplated in this invention. Several patents for walking drill rigs exist today. Because of oilfield drilling operations improvements, it is now possible to resolve the problems involved in disposing of nuclear waste in deep human-made caverns in compact areas and in volumes of disposal that are realistic, need, over very short time periods, that are safe, and that are greatly less expensive than the prior art nuclear waste disposal systems. Some embodiments, may teach optimal locations of these disposal human-made caverns, such that maximum waste storage and minimum costs may be established while disposing of the nuclear/radioactive waste into the array of the deeply located human-made caverns developed below a limited surface of land (below the surface grid pattern). The ability to economically provide the array human-made caverns, under a relatively small surface footprint, of sufficient size and volume of the human-made caverns, for the safe disposal of substantial quantities of radioactive waste is taught herein. What is required is more than just the ability to store some small amounts of waste in a single wellbore, as noted, there are needs for the disposal/storage of massive quantities of nuclear/radioactive waste and the disposal/storage in limited vertical wells is not economically practical. For example, Table 1 below, shows the capacities of various sizes of human-made caverns taught herein, based on the published density of high-level waste (HLW) metal of 18.9 grams per cubic centimeter (cc). For example, in the top row, a 36-inch diameter human-made cavern that was reamed out to a depth of 1,000 feet, would hold 3,784 metric tons of 100% of HLW waste material having a density of 18.9 gm/cc, i.e., homogenous metal. It should be noted that in practice, the actual density of the packaged disposed HLW waste may be significantly less because the HLW waste is not a solid homogenous consolidated material mass. The HLW waste may contain material parts, portions, and other constituent components that decrease the overall density based on the total volume of the waste package. For example, and without limiting the scope of the present invention, a pressurized water reactor SNF (spent nuclear fuel) module has a published nominal volume of 0.186 cubic meters and a published total weight of 657.9 Kg (kilograms). A simple density calculation may provide an overall density of about 3.54 gm/cc for the composite SNF module. This indicates that if an unassembled SNF module were to be disposed of intact (unstripped down) into its component parts it would occupy 0.186 cubic meters or about 6.56 cubic feet of human-made cavern volume. The human-made caverns contemplated herein in this invention may contain several hundred thousand cubic feet of volume each. By developing an array of multiple human-made caverns (beneath a surface grid pattern) almost any quantity of produced SNF may be disposed under current technology as discussed herein in this patent application. However, regardless of the density of the final waste package, the array of human-made caverns may be designed and selected with a total volume to accommodate all of the expected quantities of HLW waste for given site. For example, consider a situation where the HLW is designed such that the gross package waste density is 5 grams/cc, i.e., less than 20% of the true HLW waste metal density of 18.9 gm/cc. Then, the volume needed for one 1,000 metric tons of HLW waste metal is now five (5) times what is needed if the disposed metal were a “full 18.9 gram/cc” metal, i.e., a 5,000 metric ton size human-made cavern. As indicated in Table 1, the volume needed for new “downgraded” 1,000 metric tons is about a 3,000 foot deep human-made cavern with a three (3) foot diameter or a 1,000 foot deep human-made cavern with a five (5) foot diameter—either of which is very readily built as taught herein. Note, the depth of such human-made caverns is how far that given human-made cavern may extend into the given deep geological formation; i.e., in other words that depth may be thought of as a height or a length of the given human-made cavern, wherein the given human-made cavern once build is in a substantially vertical orientation. TABLE 1Showing human-made cavern capacity.METRIC TONS - CAVERN CAPACITY OF HLW METAL @ 18.9 GM/CCCAVERNDIAMETER - INCHESLENGTH36486072841,0003,7846,72610,51015,13420,5992,0007,56713,45321,02030,26841,1983,00011,35120,17931,52945,40261,7984,00015,13426,90542,03960,53682,3975,00018,91833,63152,54975,670102,9966,00022,70140,35863,05990,805123,5957,00026,48547,08473,569105,939144,1948,00030,26853,81084,078121,073164,7939,00034,05260,53694,588136,207185,39310,00037,83567,263105,098151,341205,992 In light of the problems associated with the known methods of disposing of nuclear waste (including in liquid/slurry format), it may be an object of some embodiments of the present invention, to provide a method for the disposal of nuclear waste in human-made caverns which is safe, with high volumetric capacity, that is cost-effective, and that may be performed with modified oil field equipment. It may be another object of some embodiments of the present invention, to provide methods, of the type described herein, wherein a human-made cavern of substantial strength and durability, with sufficiently protective walls and volumetric capacity may be formed in a deep geologic formation being several thousand feet below the Earth's surface and wherein the human-made cavern may be several thousand feet in vertical extent with a reasonably large diameter of several feet. A human-made cavern of this size can provide close to 1,000,000 gallons of liquid radioactive waste storage. By enlarging the substantially vertical pilot wellbore to a significant diameter and continuing to vertically drill-out and under-ream the wellbore a given human-made cavern may be formed up to several thousand feet long/deep, resulting in the given permanent human-made cavern configured for the disposal/storage of radioactive waste. Another object of the present invention is to provide a nuclear and/or the radioactive materials disposal method that uses multiple deeply located human-made disposal caverns, to reduce costs, increase disposal capacity, increase effectiveness, limit areal footprint on the surface, and limit harm from a single source of failure in the nuclear and/or the radioactive materials disposal process. Another object of the present invention is to provide a nuclear and/or the radioactive materials disposal method using multiple deeply located human-made disposal caverns, that can integrate with the existing surface operations for preparing, transporting and disposing of nuclear and/or the radioactive materials, without excessive additional costs, environmental limitations, and political problems associated with current technological approaches. It is an objective of the present invention to provide disposal method(s) for the long-term disposal of nuclear and/or radioactive waste. It is another objective of the present invention to provide disposal method(s) that are effective, e.g., effective at preventing migration and/or contamination of radioactive materials and/or radionuclides out from the human-made caverns. It is another objective of the present invention to provide disposal method(s) that are relatively and/or sufficiently safe for installation and/or operating personnel. It is another objective of the present invention to provide disposal method(s) that are relatively and/or sufficiently safe to surrounding communities and/or the surrounding environment/ecosphere. It is another objective of the present invention to provide disposal method(s) that are relatively cost effective compared to prior art methods. It is another objective of the present invention to provide disposal method(s) that are relatively easy to implement in much shorter time periods compared to prior art methods. It is another objective of the present invention to provide grid patterns on the surface of the Earth, above a given deep geological formation, wherein a footprint of the given grid pattern is smaller than the surface footprint of prior art nuclear waste disposal systems. It is another objective of the present invention to dispose of nuclear and/or radioactive materials within human-made caverns that are located within and below a relatively small “areal footprint” in deep massive geological formations, compared to the extensive acreage (multiple square miles) required to implement prior art methods. It is another objective of the present invention to drill and ream out arrays of human-made caverns in deep geological formations, located below grid patterns on the surface of the Earth. It is another objective of the present invention to form human-made caverns configured for the storage/disposal of nuclear and/or radioactive waste. It is another objective of the present invention to locate, create, make, and/or form the human-made caverns within deep geological formations. It is another objective of the present invention to dispose of nuclear and/or radioactive waste within the human-made caverns that are located within the deep geological formations. It is an objective of the present invention to avoid a need for drip shields, as design and implementation of the disposal system already accounts for and minimizes risk of ground water contamination. It is another objective of the present invention to surround and protect the nuclear and/or the radioactive materials being disposed of, within a protective medium, wherein the combination of protective medium and the nuclear and/or the radioactive materials are both located within the human-made caverns, within the deep geological formations. It is yet another objective of the present invention to seal off these deep human-made cavern(s) with, the nuclear and/or the radioactive materials (and/or with the protective medium), to prevent migration and contamination of the outside environment. These and other advantages and features of the present invention are described herein with specificity so as to make the present invention understandable to one of ordinary skill in the art, both with respect to how to practice the present invention and how to make the present invention. Table 1 may show human-made cavern capacities. 9 surface 9 (of the Earth) 9a drill site 9a 10 surface facilities 10 10a ventilation shafts 10a 11 transport tunnels/facilities 11 12 rock formations 12 13 disposal formations 13 14 disposal tunnels 14 15 human-made caverns 15 16 nuclear waste material 16 16a protective blanket 16a 16b immersive protective medium 16b 17 vertical (pilot) wellbore 17 17a connector wellbore system 17a 17b perforations 17b (in connector wellbore) 17c plug 17c (in connector wellbore) 17d down hole flow-control packer 17d (in connector wellbore) 18 walking drill rig 18 18a rig control module 18a 18b rig walking leg 18b 18c horizontal rig mover device 18c 18d vertical rig mover device 18d 18e hydraulic line 18e 18f direction of rig movement 18f 19 surface operations equipment/structures 19 20 drill rig support buildings 20 51 grid pattern 51 63 disposal formations 63 800 method of disposing of waste in gridded human-made caverns 800 801 step of designing grid pattern for waste storage in human-made caverns 801 802 step of selecting drill rig apparatus 802 803 step of locating and moving drill rig to drill site 803 804 step of setting up drill rig at drill site 804 805 step of drilling wellbore 805 806 step of under-reaming wellbore to form human-made cavern 806 807 step of conditioning human-made cavern 807 808 step of determining simultaneous operations 808 809 step of moving drill rig to another drill site 809 810 step of determining if all human-made caverns made 810 811 step of loading waste in human-made cavern 811 812 step of injecting protective media and/or additives 812 813 step of sealing wellbore and/or human-made cavern 813 814 step of drilling a connector lateral wellbore system 814 815 step of injecting protective media into the disposal cavern 815 816 step of completing and stopping the media injection into the cavern 816 817 step of stopping/ending method 817 850 method of disposing of waste in gridded human-made caverns 850 In the following discussion that addresses a number of embodiments and applications of the present invention, reference is made to the accompanying drawings that form a part thereof, where depictions are made, by way of illustration, of specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and changes may be made without departing from the scope of the invention. In this patent application, the words “well,” “wellbore,” and/or the like may be used interchangeably and may refer to cylindrical elements implemented in the design and installation processes of some embodiments discussed herein. References to well and/or wellbore without use of an accompanying reference numeral may refer to any of the wellbore sections discussed herein, such as, vertical wellbore 17. In this patent application, the words “waste,” “waste form,” “waste material,” “waste product,” and/or the like may be used synonymously and/or interchangeably and may refer to various types of nuclear (radioactive) waste material 16 to be disposed of in deep geological human-made cavern 15 systems. In some embodiments, the waste to be disposed of and contemplated as being deposed of within the deep geological human-made cavern 15 systems may comprise: nuclear waste, radioactive waste, high-level nuclear waste (HLW), spent nuclear fuel (SNF), weapons grade plutonium (WGP), uranium-based waste products, depleted uranium products, depleted uranium penetrators (DUP), uranium hexafluoride (UF6), portions thereof, combinations thereof, and/or the like. In this patent application, the words “deep geological rock formation 63,” “host rock 63,” “disposal formation 63,” “host formation 63,” and/or the like may be used synonymously and/or interchangeably. In this patent application, directional language of “vertical” and “horizontal” may be with respect to a local gravitational vector of the Earth at a given grid pattern 51, i.e., “vertical” may be substantially parallel with this local gravitational vector and “horizontal” may be substantially perpendicular (orthogonal) with respect to this local gravitational vector. In other words, the directional language of “vertical” and “horizontal” may be with respect to a local surface 9 of the Earth at a given grid pattern 51, i.e., “vertical” may be substantially perpendicular (orthogonal) with this local surface 9 of the Earth and “horizontal” may be substantially parallel with respect to this local surface 9 of the Earth. FIG. 1 illustrates a prior art scheme. FIG. 1 illustrates an inclusive overview of a preferred waste system to be developed in Sweden. The FIG. 1 system derives its origin from a massive mining approach in which a large system of tunnels and emplacements are made in granite rock 13, about 1,500 feet deep below the surface 9 of the Earth. The estimated cost to construct this waste system is about $17 Billion (USD). The estimated time of construction and emplacement is about 24 years. As stated by the Swedish Regulatory Agency: “The Deep repository for spent nuclear fuel. Deposition of waste in an initial stage is planned to take place in 2008 at the earliest. The site will be determined around the turn of the century. The canisters with spent fuel will be embedded in clay, in holes in the bottom of tunnels at a depth of about 500 metres in the bedrock. The repository will hold about 8,000 tonnes of fuel, which when encapsulated will have a volume of more than 10,000 cubic metres.” Continuing discussing FIG. 1, the disposal zone 13 is bounded by rock formations 12 above and below the disposal formation 13. Included are surface facilities 10 for managing and handling the high-level waste containers. A necessary part of the installation are ventilation shafts 10a needed to allow humans to work underground during the emplacement process. It is contemplated that these ventilation shafts 10a are to be sealed after use or used for monitoring purposes. Also are transport tunnels 11 that are needed and implemented to allow entry/egress means of personnel and material to manage the process of disposal. The high-level waste 16 is sequestered in specially made containers which are stored in the emplacement or disposal tunnels 14 which are excavated off the connecting transport tunnels 11. FIG. 2 illustrates another prior art scheme. FIG. 2 illustrates an inclusive overview of a preferred waste system to be developed in Canada. The FIG. 2 system also derives its origin from a massive mining approach in which a large system of tunnels and emplacements are made in rock 13, about 1,500 feet deep below the surface 9 of the Earth. The estimated cost to construct the waste system is about $24 Billion (USD). The estimated time of construction and emplacement is several decades. As stated by the Canadian Regulatory Agency: “The long-term management of Canada's used nuclear fuel involves the construction of a large, high-technology project that will generate thousands of jobs in the host region and potentially hundreds of jobs in a host community for many decades.” Continuing FIG. 2, the disposal zone 13 is bounded by rock formations 12 above and below the disposal formation 13. Included are surface facilities 10 for managing, protecting, and handling the high-level waste containers. A miniature “city” and operations management complex of the surface facilities 10 are expected to be built to house, feed, protect, and support several thousand individuals working on disposing of the waste material at the remote disposal site. A necessary part of the installation are ventilation shafts 10a needed to allow humans to work underground during the emplacement process. It is contemplated that these ventilation shafts 10a may be sealed after use or used for monitoring purposes. Transport tunnels 11 (shafts) are needed and implemented to allow entry/egress means of personnel and material to manage the process of disposal. The high-level waste 16 is sequestered in specially made containers which are stored in the emplacement or disposal tunnels 14 which are excavated off the connecting transport tunnels 11. These disposal tunnels 14 or placement rooms 14 are designed to contain the nuclear fuel waste 16 in copper containers encased in a “borehole,” which is essentially a short shaft or basement-like void and covered with a protective material such as bentonite. The short shaft may only be between 10 to 30 feet long. The facility is expected to store about 40,000 metric tons of nuclear waste material 16. FIG. 3 illustrates another prior art disposal scheme. FIG. 3 illustrates an inclusive overview of a preferred waste system to be developed in the U.S. The FIG. 3 system also derives its origin from a massive mining approach in which a large system of tunnels and emplacements are made in rock 13, only about 400 feet deep below the surface 9 of the Earth and in close contact with the water table in the region. Today (2020), the estimated cost is $37 Billion (USD). The estimated time of construction and emplacement is more than 30 years. Local resistance and lack of political acceptance and political will have put off the system almost indefinitely. As stated by the U.S. Congress in 1992: “Based upon studies by the nation's top scientists, Congress has decided the best solution to the critical problem of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) disposal is to place it in solid rock deep underground.” However, the Regulatory Nuclear Agencies went contrary to the stated aim of Congress and decided to follow the mining and near surface approach and recommended Yucca Mt as a site (see e.g., FIG. 3) for permanent nuclear waste storage. Continuing discussing FIG. 3, the Yucca Mt. disposal zone 13 is bounded by shallow rock formations 12 above and below the disposal formation 13. Included are surface facilities 10 for managing and handling the high-level waste containers. An operations management system, complex and apparatus, of surface facilities 10, are expected to be built to house, protect, and support several hundred individuals on the surface 9 and underground, working on disposing of the waste material 16 at the remote disposal site. A necessary part of the installation are ventilation shaft 10a needed to allow humans to work underground during the emplacement process. It is contemplated that these ventilation shafts 10a may be sealed after use or used for monitoring purposes. Transport tunnels 11 (shafts) are needed and implemented to allow entry/egress means of personnel and material to manage the process of disposal. The high-level waste 16 is sequestered in specially made containers which are stored in the emplacement or disposal tunnels 14 which are excavated off the connecting transport tunnels 11 in both horizontal and vertical directions. These disposal tunnels 14 are designed to contain the nuclear fuel waste 16 in specialized containers encased in a borehole and covered with a protective material. The boreholes holding the specialized containers are essentially short shafts or basement-like voids (rooms) carved in the floor or sides of the tunnels 14. These “rooms” are small and/or shallow at less than 10 to 20 feet in extent. The contemplated protective material is a complex of extremely expensive titanium shields which is expected to protect the nuclear waste material 16 from the inevitable rainwater expected to percolate down from the surface 9 over time. The facility is expected to dispose (store) about 80,000 metric tons of nuclear waste material 16 (which is grossly inadequate). FIG. 4A may show a schematic side view of a specialized walking drilling rig 18 capable of “walking” or “skidding” in one or more directions 18f across the surface 9 of the ground. In some embodiments, walking drill rig 18 may comprise a series of operational features which may allow walking drill rig 18 to transverse surface 9 in one or more directions 18f as indicated in FIG. 4B. Continuing discussing FIG. 4A, in some embodiments, walking drill rig 18 may comprise: rig control module(s) 18a, rig walking leg(s) 18b, horizontal rig mover device(s) 18c, vertical rig mover device(s) 18d, hydraulic line(s) 18e, portions thereof, combinations thereof, and/or the like. In some embodiments, rig control module(s) 18a may control (or may allow for control of) movement of walking drill rig 18 via movement control elements, rig walking leg(s) 18b, horizontal rig mover device(s) 18c, and vertical rig mover device(s) 18d; which may further include connected hydraulic line(s) 18e. In some embodiments, on initiation, walking drill rig 18 may drill a given vertical wellbore 17 from the surface 9 at a predetermined and/or selected drill site 9a location. In some embodiments, a given substantially vertical wellbore 17 may be drilled to a depth of about 3,000 to about 25,000 feet from the given surface 9 drill site 9a (i.e., placing distal/terminal portions of the given wellbore 17 into the given deep geological formation 63). In some embodiments, a portion of wellbore 17 may be from about zero (0) degrees to about thirty (30) degrees, plus or minus five (5) degrees, off from true vertical. In some embodiments, one or more drill site 9a locations may exist within a predetermined grid pattern 51. In some embodiments, from a given drill site 9a location, walking drill rig 18 may drill a given vertical wellbore 17. In some embodiments, once a given vertical wellbore 17 has been drilled to a predetermined depth below surface 9 and to a given disposal formation 63, walking drill rig 18 may then be used to form/create a given human-made cavern 15 (see e.g., FIG. 6 for a human-made cavern 15) via under reaming operations below that given vertical wellbore 17. In some embodiments, on completion of the drilling phase at a given drill site 9a location, resulting in at least one vertical wellbore 17 and of the under reaming resulting in at least one human-made cavern 15, the rig control module(s) 18a may initiate control of the rig walking leg(s) 18b; for example, to move walking drill rig 18 to another (different) drill site 9a location. In some embodiments, rig walking leg(s) 18b may comprise sub-units horizontal rig mover device(s) 18c and/or vertical rig mover device(s) 18d; which may allow for (permit) lateral (horizontal) and/or vertical (up-down) rig walking drill rig 18 movements. Continuing discussing FIG. 4A, in some embodiments, the rig control module(s) 18a may initiate and/or control vertical rig mover device(s) 18d which may simultaneously raise the walking drill rig 18, under control of the rig control module(s) 18a; and then the devices horizontal rig mover device(s) 18c may (simultaneously) move the walking drill rig 18 laterally (horizontally/sideways/forwards/backwards) and incrementally a distance at a rate of travel. In some embodiments, the rate of travel for a given walking drill rig 18 may be about two (2) feet per minute, plus or minus thirty (30) seconds. In some embodiments, this dynamic process of walking drill rig 18 lifting and translating may be continued in eight (8) different directions 18f (e.g., forwards, backwards, sideways, portions thereof, and/or combinations thereof) on surface 9 as shown in FIG. 4B. By continued walking and drilling operations, walking drill rig 18 may traverse the full areal pattern of the selected drill sites 9a to completely develop the desired grid pattern 51 of one or more human-made caverns 15 configured for nuclear waste 16 disposal. FIG. 4B may illustrate at least some of the various lateral/horizontal directions 18f in which the walking drill rig 18 may move across the predetermined grid pattern 51 surface 9 to different drill sites 9a on the grid pattern 51. That is, in other words, FIG. 4B may be a top down schematic view of walking drill rig 18 over the given grid pattern 51 of the surface 9. The grid pattern 51 itself may not be shown in FIG. 4B; however, the grid pattern 51 may be shown in FIG. 5, FIG. 7A, and in FIG. 7B. After walking drill rig 18 drills a given vertical wellbore 17, drills a given connector wellbore 17a, and/or under-reams a given human-made cavern 15, the walking drill rig 18 may move in multiple directions to restart and continue the drilling and/or reaming operations at other drill sites 9a disposed on the given grid pattern 51. FIG. 5 may illustrate walking drill rig 18 and its accessory drilling components situated on a given grid pattern 51 of selected or predetermined drill site 9a locations on the surface 9. In some embodiments, a given walking drill rig 18 may comprise at least four (4) rig walking legs 18b. In some embodiments, within at least some one grid of a given grid pattern 51 may be at least one drill site 9a location. In some embodiments, the walking drill rig 18 may follow the grid pattern 51 on the surface 9 by moving in any of eight (8) or so different directions 18f as shown in FIG. 4B. Continuing discussing FIG. 5, in some embodiments, grid pattern 51 may be not a pattern in the sense of a symmetry. In some embodiments, the “grids” making up a given grid pattern 51 may be not be symmetrical. In some embodiments, not all “grids” making up a given grid pattern 51 may comprise/contain a given drill site 9a location. In some embodiments, the “grids” making up a given grid pattern 51 may be of different sizes and/or shapes. Continuing discussing FIG. 5, in some embodiments, a given grid selected from the grid pattern 51 may have an area that is larger than a cross-section through a given human-made cavern 15 that may be intended to be located below that given grid. For example, and without limiting the scope of the present invention, in some embodiments, a given human-made cavern 15 may have a diameter selected from a range of about twenty-four (24) inches up to about 120 inches, plus or minus six (6) inches. In some embodiments, a given grid selected from a given grid pattern 51 may have dimensions such that the given grid is wider by at least one foot in all horizontal/lateral directions compared to the human-made cavern 15 that may be located (or intended to be located) directly vertically below that given grid. For example, and without limiting the scope of the present invention, if a given human-made cavern 15 has a diameter of ten (10) feet (i.e., 120 inches), then its directly vertically above grid may have dimensions of at least eleven (11) feet in all horizontal/lateral directions of that given grid (e.g., an 11 feet by 11 feet grid). In some embodiments, adjacent grids selected from the grid pattern 51 may each include at least one single drill site 9a; and/or a human-made cavern 15 may be located directly vertically beneath each such adjacent grid. Thus, a given grid pattern 51 on surface 9 may comprise a plurality of human-made caverns 15 distributed below surface 9 and below the grid pattern 51, but that plurality of human-made caverns 15 may be distributed in a manner that mirrors and/or mimics the above grid pattern 51, i.e., with one human-made cavern 15 located per each grid what includes a drill site 9a (not all grids in the grid pattern 51 may have drill sites 9a within). In this manner, the plurality of human-made caverns 15 may be tightly, but safely, packed together below the given grid pattern 51. Continuing discussing FIG. 5, in some embodiments, grid pattern 51 may comprise at least one drill site 9a location. In some embodiments, grid pattern 51 may comprise one or more drill site 9a locations. In some embodiments, grid pattern 51 may comprise at least two drill site 9a locations. In some embodiments, grid pattern 51 may comprise a plurality of site 9a locations. In some embodiments, a given grid selected from the grid pattern 51 may comprise at least one drill site 9a location. In some embodiments, not all grid(s) selected from the grid pattern 51 may comprise a drill site 9a location. In some embodiments, a given drill site 9a location may be a location on surface 9 wherein walking drill rig 18 (or the like) may operate from, at and/or on. In some embodiments, a given drill site 9a location may be a location on surface 9 wherein drilling operations, under-reaming operations, pumping operations, loading/inserting/landing operations, retrieval operations, maintenance operations, combinations thereof, and/or the like may occur from. In some embodiments, directly (vertically) below a given drill site 9a location may be one or more of: wellbore 17, connector wellbore 17a, human-made-cavern 15, nuclear waste material 16, protective blanket 16a, wellbore casings (piping), portions thereof, combinations thereof, and/or the like. For example, and without limiting the scope of the present invention, in some embodiments, from a given drill site 9a location, a given walking drill rig 18 may: drill at least one vertical wellbore 17 and may under-ream a terminal portion of a given vertical wellbore 17 to form a given human-made cavern 15; or drill a given connector wellbore 17a (see FIG. 7B for a connector wellbore 17a). Continuing discussing FIG. 5, in some embodiments, drill rig support building(s) 20 may also exist on surface 9, either on, adjacent to, and/or proximate to the given grid pattern 51. In some embodiments, the drilling rig support building 20 may house a set of monitoring instruments, drilling systems, down-hole logging tools, readout displays and communications equipment to allow overall control of the wellsite, portions thereof, combinations there, and/or the like. In some embodiments, the drilling rig support building 20 may house drilling personnel and/or staff onsite to allow 24-hour operations of drilling activity. Note, while FIG. 5 only shows one walking drill rig 18, some embodiments of the present invention do contemplate using one or more walking drill rigs 18. FIG. 6 may illustrate a cross-section of an embodiment in which at least one nuclear waste disposal human-made cavern 15 is implemented in the given deep geological rock formation 63 (host rock 63). (In some embodiments, a given human-made cavern 15 may be referred to as a “SuperSILO™.”) In this embodiment, human-made cavern 15 may be intentionally created, formed, and drilled out from a given wellbore 17. In some embodiments, this wellbore 17 may be initially drilled vertically from the Earth's surface 9. In some embodiments, under reaming operations may be formed at terminal/distal portions of a given wellbore 17 to form a given human-made cavern 15. In some embodiments, a given human-made cavern 15 is made by under-reaming at least some portion(s) of the wellbore 17. In some embodiments, a given human-made cavern 15 may have a diameter selected from a range of about twenty-four (24) inches up to about 120 inches, plus or minus six (6) inches. Further illustrated in FIG. 6 is nuclear waste 16 which may be placed (disposed of) in the human-made cavern 15 from surface 9. In some embodiments, the internal volume of a given human-made cavern 15 may be at least partially filled with nuclear waste material 16. In some embodiments, the internal volume of a given human-made cavern 15 may collect a predetermined amount of nuclear waste material 16. Continuing discussing FIG. 6, in some embodiments, a protective blanket (material) 16a may be implemented above a top of the nuclear waste material 16 in the given human-made cavern 15. In some embodiments, protective blanket (material) 16a may be delivered to the given human-made cavern 15 via that human-made cavern 15's attached wellbore 17. In some embodiments, protective blanket (material) 16a may be selected from one or more of: bentonite, bentonite mud, bitumen, heavy oils, cement slurries, heavy oils, emulsions, nanotubes, portions thereof, combinations thereof, and/or the like. In some embodiments, the protective blanket 16a may be integral part of the physical systems which are necessary and/or desired to mitigate migration of dangerous radionuclides away from the disposal site. In some embodiments, materials like bentonite clays, heavy oils, portions thereof, combinations thereof, and/or the like may form at least a portion of protective blanket 16a. In some embodiments, protective blanket 16a may (naturally/passively) absorb the radionuclide material, the blanket behaving, like a gel, may also provide a very low permeability flow barrier such that very little if any flow occurs across the blanket zone and away from the radioactive waste source material 16, in effect trapping the radionuclides inside the waste zone 16. In some embodiments, the protective blanket 16a may effectively protect the outside environment from the radioactive materials 16 by confining the waste 16 and preventing the potential for material 16 transport away from the cavern 15 system. Continuing discussing FIG. 6, in some embodiments, the given deep geological rock formation 63 (host rock 63 or disposal formation 63) may be one or more of: impermeable sedimentary rock, very low permeability sedimentary rock, impermeable metamorphic rock, very low permeability metamorphic rock, impermeable igneous rock, very low permeability ingenious rock, portions thereof, combinations thereof, and/or the like. “Impermeable” in this context may be with respect to water migration and/or with respect to radionucleotide migration. “Impermeable” may be having permeability measurements less than 10 nanodarcy. “Very low permeability” in this context may be with respect to water migration and/or with respect to radionucleotide migration. “Very low permeability” may be having permeability measurements between 10 and 1,000 nanodarcy. In some embodiments, deep geological rock formation 63 (host rock 63 or disposal formation 63) may be subterranean (underground), located at least 2,000 feet to 30,000 feet below an Earth surface 9, plus or minus 1,000 feet. Note, deep geological rock formation 63 (host rock 63 or disposal formation 63) has very different characteristics and properties as compared to the prior art's disposal formations 13. Continuing discussing FIG. 6, upon the surface 9 may be surface operations equipment/structures 19, drill rig support buildings 20 as shown in FIG. 5; wherein surface operations equipment/structures 19 and/or drill rig support buildings 20 may be located near to, next to, adjacent to, proximate to, the given walking drill rig 18. In some embodiments, walking drill rig 18 may be substantially as drilling rigs used in oilfield operations; however, 18 may have some modifications, such as, but not limited to shielding to minimize exposure to radiation. Continuing discussing FIG. 6, in some embodiments, at least one wellbore 17 may extend into the deep geological rock formation 63 (host rock 63). In some embodiments, the at least one wellbore 17 may be configured to receive the at least one unit of nuclear waste 16. In some embodiments, the at least one well-bore 17 may be formed from walking drill rig 18 drilling operations at a given drill site 9a location. In some embodiments, the at least one wellbore 17 may be drilled from an Earth surface 9 location of a given drill site 9a. In some embodiments, the at least one wellbore 17 may be comprised of at least one substantially vertical section (generally denoted with reference numeral “17”). In some embodiments, a distal/terminal end of the at least one wellbore 17 may terminate at a beginning of the at least one substantially vertical human-made cavern 15. In some embodiments, a distal end of the at least one wellbore 17 may terminate at an entrance to at least one human-made cavern 15, wherein the at least one human-made cavern 15 may be located within the deep geological rock formation 63 (host rock 63). In some embodiments, the at least one wellbore 17 may have at least one diameter that is drilled at a particular and predetermined size. In some embodiments, wellbore 17 may have different diameters, but each different diameter may be of a fixed size. In some embodiments, a diameter of wellbore 17 may be from 10 inches to 48 inches, plus or minus 6 inches. In some embodiments, the at least one wellbore 17 may have a length from 3,000 feet to 30,000 feet, plus or minus 1,000 feet (which may place distal/terminal portions of the given substantially vertical wellbore 17 into the deep geological formation 63). In some embodiments, a distal end of away from an Earth surface 9 location of the at least one wellbore 17 may be a final depository location for some nuclear waste 16 products. In some embodiments, the at least one wellbore 17 may be a transit means (route) configured for transit of nuclear waste material 16 through the at least one wellbore 17. Continuing discussing FIG. 6, in some embodiments, the at least one human-made cavern 15 may be substantially cylindrical in shape. In some embodiments, a length of human-made cavern 15 may be substantially parallel with the substantially vertical section of wellbore 17. In some embodiments, a length of human-made cavern 15 may be substantially parallel with the substantially vertical section of wellbore 17. In some embodiments, the at least one human-made cavern 15 may have a volume that may be fixed and predetermined, wherein each human-made cavern 15 volume may be selected from the range of about 35,000 cubic feet to about 384,000 cubic feet for a given at least one human-made cavern 15, plus or minus 5,000 cubic feet. See e.g., Table 1. In some embodiments, the at least one human-made cavern 15 may be a final depository location for disposal/storage of at least some nuclear waste material 16. In some embodiments, the at least some waste material 16 (with at least some nuclear waste in some embodiments) may be received into the at least one human-made cavern 15. Continuing discussing FIG. 6, in some embodiments, each human-made cavern 15 selected from the plurality of human-made caverns 15 may have a predetermined diameter and a predetermined length (which may yield the predetermined volume). In some embodiments, the predetermined diameter for a given human-made cavern 15 may be selected from a range of twenty-four (24) inches to 120 inches, plus or minus six (6) inches; wherein the predetermined length for a given human-made cavern 15 may be selected from a range of 500 feet to 10,000 feet, plus or minus 100 feet. In some embodiments, the predetermined diameter and/or the predetermined length of one human-made cavern 15 selected from the plurality of human-made caverns 15 may be different from the predetermined diameter and/or the predetermined length of another human-made cavern 15 selected from the plurality of human-made caverns 15. In some embodiments, this may be so, to accommodate nuclear waste 16 of a particular format (e.g., slurry versus brick) into a given human-made cavern 15 (see e.g., FIG. 7A and/or FIG. 7B); and/or this may be so because of differences in geometry of the given deep geological formation 63 that is housing the plurality of human-made caverns 15. FIG. 7A may illustrate a three-dimensional (3D) cross-section of an embodiment in which at least one nuclear waste disposal human-made cavern 15 is implemented in the given deep geological rock formation 63 (host rock 63) and below the grid pattern 51. FIG. 7A may illustrate a three-dimensional (3D) cross-section of an embodiment in which at least two nuclear waste disposal human-made caverns 15 are implemented in the given deep geological rock formation 63 (host rock 63) and below the grid pattern 51. In such embodiments, human-made caverns 15 are intentionally created, formed, drilled out, and/or under reamed from given wellbores 17, below given drill sites 9a, under/within the given grid pattern 51. In some embodiments, a distal/terminal portion of a given wellbore 17, which is initially drilled vertically from the earth's surface 9 using walking drill rig 18 (or the like), may be under-reamed to form a given human-made cavern 15. In some embodiments, a human-made cavern 15 is made by under-reaming at least some portion(s) of a given wellbore 17. Further illustrated in FIG. 7A is nuclear waste 16 which may be placed within a given human-made cavern 15 from surface 9, using wellbore 17 to reach the given human-made cavern 15, and using walking drill rig 18 (or the like). In some embodiments, a series of human-made caverns 15 may be implemented in the disposal formation 63 in grid pattern 51 (or portion thereof), by drilling and under reaming operations from the surface 9 using wellbore(s) 17 to reach the given human-made cavern(s) 15, and using at least one walking drill rig 18 (or the like). In some embodiments, two or more drill sites 9a, selected from within the given grid pattern 51, may provide the surface locations from which vertical wellbores 17 may be drilled into the host formation 63 and then the terminal/distal portions under-reamed to form a grid of human-made caverns 15 below grid pattern 51. In some embodiments, walking drill rig 18 may move from one drill site 9a location to another drill site 9a location, to develop the patterned grid of human-made caverns 15 below the surface 9 and below grid pattern 51. Continuing discussing FIG. 7A, in some embodiments, the human-made caverns 15 may be implemented at different vertical depths from the surface 9 in the host formation 63. In some embodiments, these human-made caverns 15 may each be of a different size and/or volumes (capacity) depending on these human-made cavern's 15 physical dimensions (e.g., cavern length and/or diameter); which in turn may facilitate disposal of varying types and/or differing volumes of nuclear waste material 16. In some instances, because of the differing types and/or differing contents of the nuclear waste materials 16 therein, these different human-made caverns 15 may be conditioned differently and/or independently from each other, as explained below (see e.g., step 807 of method 800 in FIG. 8A). In some embodiments, FIG. 7A may show that different types of immersive protective mediums 16b may be used in the given human-made caverns 15 to immerse, cover, mix, protect, and seal the nuclear waste material 16 residing therein. In some embodiments, the immersive protective medium 16b may function differently from the protective blanket 16a which may be localized at a top of the given waste human-made cavern 15. It is contemplated that different types of immersive protective mediums 16b may be utilized for different types of waste materials 16. Examples of immersive protective mediums 16b may be one or more of: bitumen, tars, heavy oils, cement slurries, bentonite clays, bentonite gels, other radionuclide absorbing materials, portions thereof, combinations thereof, and/or the like. In some instances, if a cement-like slurry were used as an immersive protective medium 16b, such a cement slurry on setting in the given human-made cavern 15 may bind with the waste material 16 (that is also inside of the given human-made cavern 15) to form what may be essentially and/or substantially a human-made conglomerate rock mass. In some embodiments, the human-made caverns 15 shown in FIG. 7A may contain predetermined amounts of the nuclear waste materials 16. In some embodiments, reference numeral 16a may designate both a given immersive protective medium and nuclear waste materials 16. In some embodiments, the different shadings within the human-made caverns 15 of FIG. 7A may be for setting forth immersive protective mediums 16b of different types. FIG. 7B may illustrate a three-dimensional (3D) cross-section of an embodiment in which at least one nuclear waste disposal human-made cavern 15 is implemented in the given deep geological rock formation 63 (host rock 63) and below the grid pattern 51. FIG. 7B may illustrate a three-dimensional (3D) cross-section of an embodiment in which at least two nuclear waste disposal human-made caverns 15 are implemented in the given deep geological rock formation 63 (host rock 63) and below the grid pattern 51. In such embodiments, human-made caverns 15 are intentionally created, formed, drilled out, and/or under reamed from wellbores 17. In some embodiments, at least some (one) wellbores 17 may be initially drilled vertically from the earth's surface 9, using walking drill rig 18 (or the like), may allow (distal and/or terminal portions/regions of) wellbores 17 to be under-reamed to form the given human-made caverns 15. In some embodiments, a given human-made cavern 15 may be made by under-reaming at least some portion(s) of the vertical wellbore 17. Further illustrated in FIG. 7B is nuclear waste material 16 which may be placed in (located within) the human-made caverns 15 from surface 9 (e.g., by using walking drill rig 18 [or the like] and wellbores 17). Continuing discussing FIG. 7B, in some embodiments, a series (plurality) of human-made caverns 15 may be implemented in the disposal formation 63 in (and below) grid pattern 51, by drilling and reaming operations from the surface 9 (e.g., by using walking drill rig 18 [or the like] and wellbores 17). In some embodiments, each drill site 9a location on surface 9 within grid pattern 51 may provide the surface location from which a vertical wellbore 17 may be drilled into the host formation 63 and then under-reamed to form a grid of human-made caverns 15, wherein each such human-made cavern 15 may receive at least some nuclear waste material 16 for disposal/storage. In some embodiments, one or more walking drill rig(s) 18 may move from drill site 9a location to another drill site 9a location to develop grid pattern 51 of two or more human-made caverns 15 below the surface 9. Continuing discussing FIG. 7B, in some embodiments, a connector wellbore 17a may be drilled from the surface 9 (e.g., from a given drill site 9a location) to intersect at least one of the human-made caverns 15 at a location between a top and a bottom of the given human-made cavern 15 being intersected. In some embodiments, a given connector wellbore 17a may be drilled from surface 9, but outside of the grid pattern 51 and into a given human-made cavern 15 that is located below the grid pattern 51. In some embodiments, connector wellbore 17a may be drilled and cased with pipes (casings). In some embodiments, such casings (piping) may be substantially constructed from steel or the like. In some embodiments, connector wellbore 17a may have both (substantially) vertical and (substantially) horizontal (lateral) portions. In some embodiments, connector wellbore 17a may penetrate and/or intersect at least one human-made caverns 15. In some embodiments, connector wellbore 17a may penetrate and/or intersect two or more human-made caverns 15. In some embodiments, connector wellbore 17a may penetrate and/or intersect two or more adjacent human-made caverns 15. In some embodiments, connector wellbore 17a may penetrate through the walls and across several human-made caverns 15 using available geo-steering techniques for lateral drilling and downhole perforation “guns” for perforating the walls, wellbores, and/or casings. In some embodiments, a diameter of a given connector wellbore 17a may be between four (4) inches and twelve (12) inches, plus or minus one (1) inch. In some embodiments, the portion(s) of a given connector wellbore 17a that may be intersect and/or pierce a given human-made cavern 15 may be substantially lateral/horizontal. In some embodiments, a given connector wellbore 17a may intersect and/or pierce a given human-made cavern 15 at a middle of that given human-made cavern 15. In some embodiments, a given connector wellbore 17a may intersect and/or pierce a given human-made cavern 15 above a middle of that given human-made cavern 15. In some embodiments, a given connector wellbore 17a may intersect and/or pierce a given human-made cavern 15 in an upper region of that given human-made cavern 15. Continuing discussing FIG. 7B, in some embodiments, connector wellbore 17a may comprise one or more regions of perforations 17b. In some embodiments, the one or more regions of perforations 17b in a given connector wellbore 17a may be located within human-made caverns 15 that are intersected by that given connector wellbore 17a. In some embodiments, a given connector wellbore 17a may be perforated 17b at location(s) in a given human-made cavern 15 that is intersected by the given connector wellbore 17a, such that fluid connectivity may be achieved between the surface 9, the connector wellbore 17a and the specific human-made cavern 15 internal volume, into which fluid communication may be needed and/or desired. In some embodiments, this fluid connectivity feature may allow for injection (and/or withdrawal) of fluids and pumpable material(s), which may form a distributed, immersive protective medium 16b throughout the waste material 16 disposed in the given human-made cavern 15, from the surface 9 to the intersected human-made caverns 15 with perforations 17b using the given connector wellbore 17a. Continuing discussing FIG. 7B, in some embodiments, a specialized downhole packer device or “isolation” packer 17d may be installed inside the connector wellbore 17a between consecutive human-made cavern 15 locations, that have been intersected with the given connector wellbore 17a, to shut off (or open) communication (e.g., flow) between the respective human-made caverns 15 during injection operations through the given connector wellbore 17a. In some embodiments, connector wellbore 17a may comprise one or more down hole flow-control packer 17d devices. In some embodiments, within connector wellbore 17a, the one or more down hole flow-control packer 17d devices may be located between human-made caverns 15 that have been intersected by the given connector wellbore 17a. In some embodiments such specialized packer(s) 17d may be retrievable packer, i.e., the packer device 17d may be installed and removed as needed in the given connector wellbore 17a. In some embodiments, the packer 17d may be a flow-thru device which may allow fluids to flow through the device 17d when the device is in the open position. In some embodiments, the packer 17d may be a flow-control device which may allow fluids to flow through the device 17d when the device is in the open position. In some embodiments, in the closed position of a given packer 17d, no flow is allowed across and/or through the packer 17d. In some embodiments, a given packer 17d may have at least two operational configurations, open and closed; wherein in the open configuration fluid flow may be permitted through and/or across the given packer 17d; wherein in the closed configuration, fluid flow is stopped from flowing through and/or across the given packet 17d. In some embodiments, the open configuration of a given packer 17d may be variable, such as, but not limited to, high flow, medium flow, low flow, combinations thereof, and/or the like. Continuing discussing FIG. 7B, in some embodiments, a plug 17c device may be installed at a terminal end of the connector wellbore 17a. In some embodiments, connector wellbore 17a may comprise at least one plug 17c. In some embodiments, at least one plug 17c may be located at a distal/terminal end of connector wellbore 17a, disposed away from the drill site 9a wherein the given connector wellbore 17a was drilled from. In some embodiments, plug 17c may seal off (close) the given connector wellbore 17a. In some embodiments, a given plug 17c may prevent loss of fluid(s) which may be injected into the connector wellbore 17a and into the human-made caverns 15 intersected by that connector wellbore 17a. In some embodiments, FIG. 4A through FIG. 7B may shows systems and/or components of systems for nuclear waste disposal using a geologically deep array/grid of human-made caverns 15. In some embodiments, developing the deep disposal array of a plurality of human-made caverns 15 (configured for receiving nuclear waste materials 16) over the disposal area of the given grid patter 51 may be relatively inexpensive, i.e., tens of millions of dollars, as compared to the billions of dollars envisaged for development of the mining type disposal systems in the prior art. For example, and without limiting the process discussed herein, drilling and completing a single pilot wellbore 17 and human-made cavern 15 may cost between $5,000,000 and $10,000,000 depending on the size (diameter) of the human-made cavern 15 and the length (height) of the human-made cavern 15 and the depth of the host rock 63. A 5,000 feet deep system may cost less than $10,000,000. Thus, development of an array of twenty (20) human-made caverns 15 may cost only $200 million, a figure that is less than 5% of the cost projected for the smallest prior art mining solutions for nuclear disposal. This cost comparison vis-a-vis the prior art is at least one significant benefit of the new embodiments described herein. For example, and without limiting the scope of the present invention, a system for nuclear waste disposal using a geologically deep array/grid of human-made caverns 15 implemented in rock formation at 5,000 feet deep, notably, significantly deeper than any prior art mining method, and using at least one walking drill rig 18, there may be only one mobilization cost and de-mobilization cost regardless of the number of wellbores 17 and/or human-made caverns 15 drilled and completed. Thus, there is a significant decrease in overall cost for such embodiments. A further significant benefit of embodiments of the present invention maybe the greatly reduced times needed to drill and complete the human-made cavern 15 system over the design grid pattern 51 array. For example, and without limiting the scope of the present invention, drilling and completing a 5,000 foot, single well 17/cavern 15 system may be implemented in a time period between 50 and 70 days. A significant time improvement over the times of years or even decades needed to prepare the mines and tunnels for the prior art disposal methods. In some embodiments, the systems for nuclear waste disposal using a geologically deep array/grid of human-made caverns 15 and/or components thereof shown in FIG. 4A through FIG. 7B may be used to implement various methods for nuclear waste disposal using the geologically deep array/grid of human-made caverns 15, see e.g., FIG. 8A and its discussion. FIG. 8A may illustrate a flow chart of a method 800 for implementing a gridded system of deep subterranean human-made caverns 15 for the disposal of dangerous waste materials 16. FIG. 8A may depict at least some steps of method 800. In some embodiments, method 800 may be a method of designing, implementing, and/or using a grid pattern 51 on the surface 9 with a plurality of drill holes 9a from and below which, are made a plurality of human-made caverns 15 located deep in a geological formation 63 by utilization of a self-propelled walking drill rig 18, wherein the plurality of human-made caverns 15 are configured for receiving dangerous waste materials 16. In some embodiments, method 800 may be a method for nuclear waste 16 disposal using the geologically deep array/grid of human-made caverns 15. In some embodiments, method 800 may be a method for utilizing a self-propelled walking drilling rig 18 capable of lateral, horizontal, vertical, and translational movement across the surface 9 to drill at a plurality of drill sites 9a. In some embodiments, the plurality of drill sites 9a may be disposed of (located) within a surface 9 grid pattern 51. In some embodiments, the plurality of drill sites 9a may be located within at least some of the grids of the grid pattern 51. In some embodiments the walking drill rig 18 may be capable of drilling a vertical wellbore 17 and reaming out a human-made cavern 15 below the vertical wellbore 17 from any given drill site 9a. In some embodiments the walking drill rig 18 may be capable of drilling connector wellbore(s) 17a from at least some of the drill sites 9a. Continuing discussing FIG. 8A, in some embodiments, method 800 may comprise at least one step selected from steps of: 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, portions thereof, combinations thereof, and/or the like. Some embodiments of method 800 may omit one or more of these steps. Some embodiments of method 800 may be one or more decision steps (e.g., steps 808 and 810). Some embodiments of method 800 may repeat at least one of these steps (e.g., because more than one human-made cavern 15 may be formed according to method 800). In some embodiments, the order of the steps in method 800 may not occur in numerical order. Continuing discussing FIG. 8A, in some embodiments, step 801 may be a step of defining and/or analyzing operational parameters, land, geology, accessibility features, necessary to provide the design, layout, and/or physical dimensions associated with the human-made cavern 15 implementation methods and techniques. In some embodiments, outputs of this step 801, may be plans of: showing the layout of the grid pattern 51; drill sites 9a layouts/distributions; which drill sites 9a may be for wellbores 17 and/or for human-made caverns 15; which drill sites 9a may be for connector wellbores 17a; which human-made caverns 15 may be connected by a given connector wellbore 17a; quantity and types of drilling, under-reaming equipment (walking drill rig(s) 18); sequence of drill sites 9a to be worked (e.g., by a given walking drill rig 18); walking drill rig(s) 18 movement plans; quantity, types, and locations of surface operations equipment/structures 19 and/or drill rig support buildings 20; aerial distribution plans; survey results; quantity and types of personnel; portions thereof; combinations thereof; and/or the like. In some embodiments, surface 9 of a given grid pattern 51 may comprise from about 20 acres and to about 100 acres, plus or minus 5 acres. Note, even at 100 acres of a given grid pattern 51, this is significantly smaller than the acreage needed for the prior art methods. In some embodiments, grid pattern 51 may be of a quantity of predetermined acres (that may be less than 20 acres or more than 100 acres in some embodiments). In some embodiments, step 801 may be a step of forming a predetermined grid pattern 51 on a surface 9 of the Earth that may be (substantially) vertically directly above at least one deep geological formation 63, wherein the predetermined grid pattern 51 may comprise a plurality of grids, wherein a sub-set of the plurality of grids may comprise at least one drill site 9a per grid selected from the sub-set. In some embodiments, step 801 may progress into step 802. Continuing discussing FIG. 8A, in some embodiments, step 802 may be a step of selecting at least one self-propelled walking drill rig 18, with an operational and handling capacity to drill at least one vertical wellbore 17 and to then under-ream at least portion of that wellbore 17 for make at least one human-made cavern 15. In some embodiments, a selected walking drill rig 18 may also be used to drill connector wellbore(s) 17a. In some embodiments, more than one walking drill rig 18 may be selected (and used) to allow simultaneous drilling operations to be implemented at separate drill sites 9a over the grid pattern 51. In this simultaneous operation, purposely selected multiple drilling sites 9a may be drilled in a parallel time operations. In some embodiments, this parallel operation may be desired to meet operational deadlines, time requirements, or other demands on the waste disposal operation. In some embodiments, step 802 may progress to step 803. Continuing discussing FIG. 8A, in some embodiments, step 803 may be a step of locating and moving a selected walking drill rig 18 to a selected drill site 9a on the grid pattern 51. In some embodiments, step 803 may be a step of placing a first walking drill rig 18 at one of the at least one drill sites 9a. This operation may typically referred to as “mobilization” in the oil-field industry may allow more than one walking drill rig 18 to be mobilized simultaneously or sequentially. In some embodiments, step 803 may progress to step 804. Continuing discussing FIG. 8A, in some embodiments, step 804 may be a step of setting up (e.g., stabilizing and preparing to drill) the given walking drill rig 18 over the selected drill site 9a on the grid pattern 51. This operation may typically be referred to as “spudding” in the oil-field industry may allow more than one walking drill rig 18 to be “spudded” simultaneously or sequentially if the operation may utilize a plurality of walking drill rigs 18. In some embodiments, step 804 may progress to step 805. Continuing discussing FIG. 8A, in some embodiments, in step 805, vertical wellbore 17 may be drilled by the walking drill rig 18 from surface 9 (and from that given drill site 9a) to a prescribed (predetermined) depth of 2,000 to 30,000 feet, plus or minus 100 feet and to (or into) a given disposal formation 63. In some embodiments, step 805 may be a step of drilling a substantially vertical wellbore 17 from the surface 9 directly down to the deep geological formation 63 using the first walking drill rig 18, wherein the substantially vertical wellbore 17 may at least physically touch the deep geological formation 63. In some embodiments, successful completion of step 805 may then progress into step 806. Continuing discussing FIG. 8A, in some embodiments, in step 806, a section of the wellbore 17 may be drilled into host rock 63 to initiate the formation of a given human-made cavern 15. In some embodiments, in step 806 an under-reaming device may be run into a distal/terminal portion of vertical wellbore 17 where it may be desired to form the given human-made cavern 15 in host rock 63, by use of that under reaming device. In some embodiments, via such under-reaming operations of the terminal/distal portions of wellbore 17, within host rock 63, the given human-made cavern 15 may be formed into the host rock 63. Within a location in host rock 63 where it may be desired to form the given human-made cavern 15, the under-reaming device may be activated and used to form that given human-made cavern 15. For example and without limiting the scope of the present invention, this under-reaming operation may involve deploying, extending, and/or activating multiple reaming devices. One or more reaming devices (e.g., in tandem) may be utilized to form the given human-made cavern 15 in host rock 63 (from wellbore 17). In some embodiments, in step 806 the under-reaming process may continue either directly or sequentially in phases to ream out human-made caverns 15 in host rock 63 to a depth (length) from 500 feet to 10,000 feet (plus or minus 100 feet), of vertical extent downwards within host rock 63, and with diameters from about 24 inches up to 120 inches, plus or minus six (6) inches. In some embodiments, successful completion of step 806 may result in the making at least one human-made cavern 15 entirely located within the given host rock 63. In some embodiments, step 806 may be a step of under-reaming a terminal portion of the substantially vertical wellbore 17 into the deep geological formation 63 using the first walking drill rig 18 to form a human-made cavern 15 that is located within the deep geological formation 63, wherein the human-made cavern 15 formed in the step 806 is a member of the plurality of human-made caverns 15 of the array that are located below the given grid pattern 51. In some embodiments, successful completion of step 806 may then progress into step 807. Continuing discussing FIG. 8A, in some embodiments, in step 807 a given human-made cavern 15 reamed out (made) in step 806 may be conditioned internally by treating the inside surface, walls, top and/or bottom of the given human-made cavern 15 with various predetermined materials (e.g., chemicals and/or coating/sealing products). In some embodiments, the conditioning step 807 may be done to seal the cavern interior surfaces of the human-made caverns 15 against radionuclide migration. In some embodiments, conditioning of the interior human-made cavern 15 surfaces may be done by operational means from surface systems with wireline or similar oilfield practices equipment. The types of coatings for the interiors of the human-made caverns 15 may be one or more of: cements, epoxies, nanoparticles, ceramics, clays, paints, sprays, portions thereof, combinations thereof, and/or the like. The conditioned human-made cavern 15 may be in a state ready to accept the radioactive nuclear waste 16 processed on the surface 9. In some embodiments, after the step 806, the method 800/850 may further comprise step 807 of conditioning the human-made-cavern(s) 15 formed in the step 806, by treating at least most of interior surfaces of the human-made-cavern 15 formed in the step 806 with at least one protective material configured to minimize radionuclide migration. In some embodiments, step 807 of conditioning human-made cavern 15 interior surfaces may not be necessary for some types of host rock 63 which may be crystalline and having very low porosity and permeability levels; and in such situations, step 806 may progress to step 808, i.e., step 807 may be omitted from method 800. In some embodiments, successful completion of step 807 may then progress into step 808. Continuing discussing FIG. 8A, in some embodiments, step 808 may be a decision step. In some embodiments, step 808 may be a step of determining and/or deciding whether at least some of the remaining steps of method 800 may be occurring concurrently/simultaneously or whether at least some of the remaining steps of method 800 may occur in a sequential/serial fashion. In some embodiments, this step 808 may decide and/or determine whether making additional wellbores 17 and/or additional human-made caverns 15 via at least one walking drill rig 18 may occur concurrently, while loading of nuclear waste materials 16 may be done by another separate rig (e.g., another walking drill rig 18, or a smaller “workover” rig, or the like) in a different already completed wellbore 17 and human-made cavern 15. It may be necessary to implement simultaneous operations depending on the required and/or desired outcomes for the overall waste disposal process, such as, but not limited to, outcomes from step 801, and/or other operational goals/deadlines. In some applications of embodiments of the present invention, disposal operations times may be a critical factor and overall costs may be secondary. In some embodiments, step 808 may lead to step 809 or step 811. In some embodiments, step 808 may be omitted and step 806 or step 807 may progress to step 809. Continuing discussing FIG. 8A, in some embodiments, step 809 may be a step of moving (“walking”) a given walking drill rig 18 to another drill site 9a within the grid pattern 51. In some embodiments, step 809 may involve the self-propelled movement of walking drill rig 18 from its current completed and drilled well drill site 9a to a new yet to-be-drilled (new/different) well drill site 9a. In some embodiments this walking motion of the given walking drill rig 18 may be accomplished initially by rig controller module(s) 18a activating/engaging the rig walking legs 18b via the hydraulic line(s) 18e and/or horizontal rig mover devices 18c and/or vertical rig mover device 18d, as needed depending upon the terrain of surface 9. In some embodiments, the rig walking legs 18b may raise the walking drill rig 18 a required distance vertically off the ground surface 9 by activating/engaging the vertical mover devices 18d. In some embodiments, while the walking drill rig 18 may be elevated off the ground surface 9, the controller modules 18a may via the hydraulic line(s) 18e initiate lateral (horizontal) movement, (e.g., “walking” and/or “skidding”) of the walking drill rig 18 using the horizontal mover devices 18c. In some embodiments, this movement/translation action may move the walking drill rig 18 in any one of the many available directions as shown in FIG. 4B and to the new drill site 9a within the grid pattern 51. In some embodiments, the controller module(s) 18a by repeating the rig movement actions may move the walking drill rig 18 tens of feet in an hour to relocate walking drill rig 18 over a new drill site 9a. In some embodiments, step 809 may be a step of walking the first walking drill rig 18 to another of the least one drill sites 9a and repeating the steps 805 and 806 to form other of the human-made caverns 15 selected from the plurality of human-made caverns 15, wherein the step 809 executes if all of the at least one drill sites 9a do not have one of the human-made-caverns 15 located directly and vertically below. In some embodiments, successful completion of step 809 may then progress into step 810. Continuing discussing FIG. 8A, in some embodiments, step 810 may be a decision step. In some embodiments, in step 810 a determination is made if all the required well sites 9a have been drilled and reamed out to form human-made caverns 15 over the total designated grid pattern 51. If not, then the human-made cavern 15 forming processes may return method 800 to step 804 to initiate the drilling and the formation of a new human-made cavern 15. In some embodiments, step 804, step 805, step 806, (and step 807 if desired or needed), and step 809 may be repeated until all human-made caverns 15 for that drill pattern 51 are completed. In some embodiments, if all human-made caverns 15 for that drill pattern 51 are completed, then step 810 may progress to step 811 and/or step 814. In some embodiments, if all well sites 9a in the grid pattern 51 have been drilled, then method 800 may continue to step 811 and/or to step 814. In some embodiments step 810 may lead to step 804. In some embodiments step 810 may lead to step 811 and/or to step 814. Continuing discussing FIG. 8A, in some embodiments, step 811 may be a step of placing, locating, loading, pumping, injecting, inserting, landing, combinations thereof, and/or the like of predetermined amounts of nuclear waste materials 16 into a given human-made cavern 15, via the given wellbore 17 that is connected to that given human-made cavern 15 and from the surface 9. In some embodiments, step 811 may be a step of loading at least some of the radioactive waste 16 into at least one of the human-made caverns 15 selected from the plurality of human-made caverns 15 formed from the step 809. This placement process may continue until the given human-made cavern 15 is filled with a precalculated quantity of nuclear waste 16. In some embodiments, in step 811 the radioactive waste material 16 that may be placed into the given cavern 15 may be in a predetermined form. In some embodiments, before executing step 811, the nuclear waste materials 16 may be converted (processed) into the predetermined forms that may be more manageable, such as, but not limited to: substantially solidified, substantially liquified, substantially made into a gel, substantially made into pellets, substantially in a rock format, substantially in a brick format, substantially made into powder, substantially made into a slurry, substantially made into a foam, substantially treated with predetermined chemical mixtures, portions thereof, combinations thereof, and/or the like to enable easier transport and eventual sequestration into the human-made caverns 15. In some embodiments, walking drill rig 18 or the other types of rigs or other surface pumping/injecting equipment or the like, may be used to insert the nuclear waste materials 16 into the human-made caverns 15. In some embodiments, step 811 may progress into step 812. In some embodiments, the step 811 may be executed by the first walking drill rig 18, after all the at least one drill sites 9a have one of the human-made caverns 15 selected from the plurality of human-made caverns 15, located directly vertically below; i.e., this may be an example of sequential operations for the method. Continuing discussing FIG. 8A, in some embodiments, step 812 may be a step of injecting, pumping, inserting, filling, and/or landing protective materials, media, and/or additives (e.g., immersive protective medium 16b) into the given human-made cavern 15, with the nuclear waste materials 16, using the given wellbore 17 that connects to the given human-made cavern 15. This placement process may continue until human-made caverns 15 may be filled with a precalculated quantity of protective materials, media, and/or additives along with the already placed amount of nuclear waste 16. In some embodiments, the protective material inserted in step 812 into the given human-made cavern 15 may be protective blanket 16a (see e.g., FIG. 6) and/or immersive protective medium 16b. In some embodiments, protective blanket 16a may substantially cover over a top of the nuclear waste material 16 within the given human-made cavern 15. In some embodiments, protective blanket 16a may be some protective medium like a bentonite clay or a radionuclide absorber/inhibitor material that may be injected to remain above nuclear waste 16 within a given human-made cavern 15. In some embodiments, after the step 811, the method 800/850 may further comprise a step 812 of inserting (e.g., by injection and/or spray or the like) at least one protective material 16a over and on top of the at least some of the radioactive waste 16 that is located within the at least one of the human-made caverns 15. In some embodiments, the at least one protective material 16a may be selected from one or more of: bentonite, bentonite mud, bitumen, heavy oils, cement slurries, heavy oils, emulsions, nanotubes, portions thereof, combinations thereof, and/or the like. See e.g., FIG. 6 for protective blanket 16a. In some embodiments, this protective blanket 16a may behave as two-way barrier which may slow down physical migration of radioactive particles, fluid material, and other soluble compounds into or away from nuclear waste 16 mass that is stored in the given human-made caverns 15. In some embodiments, successful completion of step 812 may then progress into step 813. In some embodiments, step 813 may continue to step 817 which may be a terminal step. Continuing discussing FIG. 8A, in some embodiments, step 814 may be a step of forming a connector wellbore 17a from a given drill site 9a using a walking drill rig 18 or the like. See e.g., FIG. 7B and its discussion of connector wellbores 17a. In some embodiments, a given connector wellbore 17a may connect at least one human-made cavern 15 with surface 9. In some embodiments, a given connector wellbore 17a may connect two human-made caverns 15 together, along with connecting to surface 9. In some embodiments, either before the step 811 or before the at least some of the radioactive waste 16 that is located within the at least one of the human-made caverns 15 reaches a predetermined level within the at least one of the human-made caverns 15, the method 800/850 may further comprise step 814 of drilling a connector wellbore 17a from the surface 9 to the at least one of the human-made caverns 15, such that the connector wellbore 17 intersects and pierces into the at least one of the human-made caverns 15. In some embodiments, the method 800/850 may further comprise step 814 of directing the connector wellbore 17a to intersect and pierce at least one other human-made cavern 15 selected from the plurality of human-made caverns 15. In some embodiments, the at least two human-made caverns 15 that may be intersected and pierced by the same connector wellbore 17a, may be adjacent to each other. See also, FIG. 7B. In some embodiments, the connector wellbore 17a may comprises at least one flow-control packer 17d configured to control flow of fluids through the connector wellbore 17a. In some embodiments, the at least one flow-control packer 17d may be located between two adjacent human-made caverns 15 selected from the plurality of human-caverns 15 that are both intersected and pierced by a same connector wellbore 17a. See also, FIG. 7B. In some embodiments, a given connector wellbore 17a may comprise: at least one perforation 17b in each intersected human-made cavern 15, at least one packer 17d between a pair of intersected human-made caverns 15, and at least one plug 17c. In some embodiments, a diameter of a given connector wellbore 17a may be between four (4) inches and twelve (12) inches, plus or minus one (1) inch. In some embodiments, a diameter of connector wellbore 17a may be smaller than a diameter of wellbore 17. In some embodiments, in step 814, the connector wellbore 17a may be cased with steel (or the like) casing all the way from the surface 9 and into the lateral section and finally across the human-made caverns 15. It should be pointed out that standard steel casing strings, casing sections or drill-pipe behind the drill bit, are usually about thirty (30) feet long and as such, traversing (extending) across a relatively small human-made cavern 15 of diameter less than six (6) feet is not an operational problem for the structurally rigid steel cylinder casing/piping. Continuing discussing FIG. 8A and step 814, in some embodiments, the steel casing of the connector wellbore 17a may be perforated by perforating guns, (which are common tools in the oil drilling industry), at specific locations shown by perforations 17b in FIG. 7B. In some embodiments, the perforations 17b may be readily calculated accurately and reliability from drilling data and it is implemented at precise points along and in the connector wellbore 17a such that the perforations 17b in the casing pipe are made to be located within the human-made caverns 15 that are intersected by the given connector wellbore 17a. In some embodiments, these perforations 17b may allow injected fluids to enter or communicate from the connector wellbore 17a and into the human-made caverns 15 internal spaces. In some embodiments, in step 814 the connector wellbore 17a may be drilled and cased and perforated before the loading of waste 16 is initiated, or before the waste 16 is accumulated above a projected line of intersection of the given connector wellbore 17a within the given human-made cavern 15. In other words, it would not be beneficial to drill the connector wellbore 17a after the given human-made cavern 15 is full of waste 16 above where the connector wellbore 17a intersects that given human-made cavern 15. Drilling through nuclear waste 16 is not a good or recommended practice. Continuing discussing FIG. 8A and step 814, in some embodiments, a (retrievable in some embodiments) flow-thru (flow-control) downhole packer 17d may be implemented from the surface 9 and inserted (landed) inside the bore of the given connector wellbore 17a to limit and/or control fluid movement selectively along and through the wellbore 17a during injection of protective materials and/or additives into the respective caverns 15 through the perforations 17b. By selectively operating these specialized packers 17d, it may be possible to selectively inject any sequence of human-made caverns 15 (that are intersected by connector wellbores 17a) by injection with protective materials and/or additives. In some embodiments, step 814 may progress to step 815. Continuing discussing FIG. 8A, in some embodiments, step 815 may be a step of injecting protective materials and/or additives into a given human-made cavern 15, through perforations 17b, by use of the given connector wellbore 17a that intersects that given human-made cavern 15. In some embodiments, the method 800/850 may further comprise step 815 of injecting protective materials through perforations 17b in the connector wellbore 17a, wherein the perforations 17b may be located in at least a portion of the connector wellbore 17a that is positioned within a given human-made cavern 15 selected from the plurality of human-made caverns 15, such that protective materials that are injected through the perforations 17b are received into the given human-made cavern 15. See also, FIG. 7B. In some embodiments, use of the packers 17d may facilitate step 815. In some embodiments, these injected protective materials and/or additives, may be radionuclide absorbent/captor materials which may hold radioactive particles in place and slow down migration away from human-made caverns 15. In some embodiments, the protective materials and/or additives may provide protective measures to keep the waste material 16 from migrating away from the disposal human-made caverns 15 and polluting the environment. In some embodiments, for a given human-made cavern 15, step 815 may progress before or concurrently with step 811. In some embodiments, during step 811, pressure may be exerted at perforations 17b (e.g., via step 815) to minimize waste materials 16 from entering connector wellbore 17a. In some embodiments, use of packers 17d may also be used to minimize migration of waste materials 16 within connector wellbores 17a. In some embodiments, successful completion of step 815 may then progress into step 816. Continuing discussing FIG. 8A, in some embodiments, step 816 may be a step of stopping the injection of protective materials and/or additives through connector wellbore 17a and perforations 17b. In some embodiments, in step 816 packers 17d may be left in closed configurations. In some embodiments, in step 816 connector wellbores 17a may be sealed, capped and/or otherwise closed (e.g., by use of predetermined plugs). In some embodiments, step 816 may lead to step 813. In some embodiments, steps 814, 815, and 816 may be omitted from method 800 (see e.g., FIG. 7A). Continuing discussing FIG. 8A, in some embodiments, method 800 may comprise a step (e.g., step 813) of shutting down the disposal process in a given deep human-made cavern 15. In some embodiments, method 800 may comprise a step (e.g., step 813) of sealing a given human-made cavern 15 and its wellbore(s) 17 (and 17a if any), by using one or more of: downhole plugs, packers, cement plugs; which may plug and seal off the applicable wellbore(s) 17 (and 17a if any). In some embodiments, a means (e.g., buildings, structures, fencing, flags, signage, transponder, etc.) to safely mark the location of the sealed/closed wellbores 17 (and 17a if any) on the Earth's surface 9 may be implemented. In some embodiments, after the step 811, the method 800/850 may further comprise a step 813 of sealing and/or closing off the substantially vertical wellbore 17 that leads to the at least one of the human-made caverns 15 with the at least some of the radioactive waste 16. In some embodiments, step 813 may progress to step 817, when all such wellbores 17 and 17a may be closed and/or sealed off. Continuing discussing FIG. 8A, in some embodiments, step 817 may finally terminate and stop the operational disposal processes of method 800. FIG. 8B may depict at least of the steps for method 850. In some embodiments, method 850 may be similar to method 800, e.g., sharing the same goals and/or objectives, such as being a method of disposing of nuclear waste materials 16 within a plurality of human-made caverns 15 that are arranged in a gridded pattern beneath a grid pattern 51. In some embodiments, method 850 may also share many steps with method 800; however, at least some of the steps in method 850 may be executed in a different order. In some embodiments, method 850 may comprise the steps of: 801, 802, 803, 804, 805, 806, 807, 809, 810, 811, 812, 813, 814, 815, 816, 817, portions thereof, combinations thereof, and/or the like. In some embodiments, the steps of method 850 may occur as described above for method 800, except for the differences as noted below. Continuing discussing FIG. 8B, in method 850, steps 801 to 807 may proceed as discussed above for method 800; except in method 850 step 806 or step 807 may proceed to step 810. In some embodiments, in method 850, the “yes” pathways from step 810 may proceed as was discussed above for method 800, i.e., the “yes” pathways from step 810 may proceed to step 811 and/or to step 814. However, the “no” pathway from step 810 in method 850 may proceed to step 809 and then step 809 may proceed to step 804. Also note that while step 808 is not explicitly called out in method 850, note that “simultaneous operations” may occur in method 850 as well as in method 800. Note, in this context, “simultaneous operations” may refer to the making of new/additional human-made caverns 15 (e.g., per step 804 to step 807) within the given grid pattern 51 using at least one walking drill rig 18 (to build out the array of a plurality of human-made caverns 15); while nuclear waste 16 filling operations into already formed human-made caverns 15 (e.g., step 811 to step 816) is concurrently occurring by use of at least one other different rig (which may be another/different walking drill rig 18 or some other type of rig [e.g., a workover rig]). Note, in some embodiments, method 850 and/or method 800 may also execute without such simultaneous operations. With respect to FIG. 8A and/or FIG. 8B, in some embodiments, a path which may comprise step 811, step 812, and step 813 may be a typical load (of nuclear waste 16) and seal path for a given human-made cavern 15 under the given grid pattern 51(and in the deep geological formation 63); whereas, a different path that may comprise step 814, step 815, step 816, step 811, step 812, and step 813 may be used if at least one lateral connector wellbore 17a may be implemented to connect at least some of the deep human-made caverns 15 under the given grid pattern 51 (and in the deep geological formation 63). In some embodiments, method 800 and/or method 850 may be a method for disposing of radioactive waste 16 into a plurality of human-made caverns 15 that may be arranged in a predetermined array pattern within a deep geological formation 63, wherein the plurality of human-made caverns 15 may be located substantially vertically below grid pattern 51. In some embodiments, method 800 and/or method 850 may comprise steps 801, 803, 805, 806, 809, and 811. In some embodiments, the step 811 and the step 809 may occur simultaneously by a different rig (e.g., a rig other than the first walking drill rig 18) performing the step 811 while the first walking drill rig 18 performs the step 809. In some embodiments, the different rig may be a second walking drill rig 18 or a workover rig or the like. Such operations may be examples of simultaneous operations. In some embodiments, during the step 809 by the first walking drill rig, a second walking drill rig 18 may form others of the plurality of human-made caverns 15 by drilling other substantially vertical wellbores 17 into the deep geological formation 63 and under-reaming distal portions of those other substantially vertical wellbores 17. In some embodiments, the first and/or the second walking drill rigs 18 may be used in executing step 811 and/or other steps of method 800/850. That is, in some embodiments, method 800/850 may be carried out with two or more walking drill rigs and/or other types of drill rigs. In some embodiments, the predetermined array pattern of a distribution of the plurality of human-made caverns 15 may located (substantially) vertically directly below the predetermined grid pattern 51, with each human-made cavern 15 selected from the plurality of human-made caverns 15 being linked to the surface 9 by one of the substantially vertical wellbores 17. See e.g., FIG. 7A, FIG. 7B, FIG. 6, and FIG. 5. In some embodiments, prior to the step 811, the at least some of the radioactive waste 15, that is to be loaded within the at least one of the human-made caverns 15 in the step 811, may be formed into a “particular format” (preprocessed into a particular format). In some embodiments, this “particular format” is selected from one or more of: solid, liquid, liquified, slurry, pellet, powder, brick, spherical, ball, gel, rod, cylindrical, briquette, foam, portions thereof, combinations thereof, and/or the like. In some embodiments, each human-made cavern 15 selected from the plurality of human-made caverns 15 may be configured to receive the particular format by having a predetermined length, a predetermined diameter, and optionally by having a majority of interior surfaces treated with at least one predetermined material. See e.g., FIG. 7A and note the different texture/hash patterns of the nuclear waste material 16 within the human-made caverns 15 that denotes the nuclear waste material 16 of different particular formats. For example, and without limiting the scope of the present invention, the more flowable/liquified/slurry like particular formats of the nuclear waste material 16 may only need relatively smaller diameters of human-made cavern 15 as compared to particular formats with SNF subassemblies still at least partially intact. Systems and methods for nuclear waste disposal in gridded array/pattern of geologically deep located human-made caverns has been described. The foregoing description of the various exemplary embodiments of the invention has been presented for the purposes of illustration and disclosure. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching without departing from the spirit of the invention. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. |
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description | The present application hereby claims priority under 35 U.S.C. §119 on German patent application number DE 103 12 450.0 filed Mar. 20, 2003, the entire contents of which are hereby incorporated herein by reference. The invention generally relates to a method for the compensation of image disturbances. Preferably, the disturbances are in the course of a radiation image recording caused by a defocusing of an antiscatter grid. The grid is preferably arranged in the beam path between a beam source and a digital radiation image receiver and is focused with respect to a specific distance from the focus of the beam source. The image disturbances are preferably caused by a defocusing-dictated attenuation of the primary radiation incident on the solid-state image detector. The radiation image receiver preferably has radiation-sensitive pixels arranged in matrix form and a device for pixelwise amplification of the radiation-dependent signals. The use of antiscatter grids in radiation, in particular X-ray, diagnosis is the most widely used and recognized method for reducing the proportion of scattered radiation in the imaging radiation, the primary radiation, and for improving the contrast of the radiation image recording. The grids that are mainly used nowadays are focused linear grids. These linear grids include absorber lamellae, generally lead lamellae, embedded in a carrier material, generally paper or plastic layers. For focusing purposes, the absorber lamellae are arranged upright or inclined with respect to the vertical in such a way that the diverging primary radiation can pass through between the lamellae, but the scattered radiation is blocked (grid focusing). Each grid is focused with respect to a specific, defined distance from the focus of the beam source. The inclination of the absorber lamellae corresponds to the divergence of the primary beam cone at a specific distance with respect to which the grid is focused. Any deviation from the focusing distance leads to a dose decrease in the primary radiation primarily in the image edge regions. This is due to the fact that, in the case of a deviation from the focusing distance, the clear width between the lamellae decreases and, consequently, more primary radiation is absorbed by way of the absorber lamellae, the absorption increasing with increasing deviation from the focusing distance, that is to say with increasing defocusing. The distance tolerances which are specified for each grid and within which a defocusing still leads to acceptable, diagnostically meaningful images are based on a dose decrease of 40% at the image receiver edge as seen from the grid center (IEC/DIN 60627). In this case, the decrease is given not only by the different transmittivity of the grid in the case of nonfocusing, but also by the outwardly decreasing dose (square law of distance). The distance tolerance range used under these preconditions is primarily determined by the shaft ratio “R”, that is to say the ratio of the width of the shaft between two lamellae to the height of the lamellae. In the case of the digital radiation image receivers that are increasingly being used, e.g. in the form of solid-state detectors or flat detectors, use is made of antiscatter grids having a significantly higher number of lines (of e.g. 80 lines/cm) compared with the grids used e.g. in the case of film systems. In order to obtain the same selectivity (scattered radiation suppression) as in the case of the moving grids used in conventional film radiography (shaft ratio R=8 or 12), higher shaft ratios (e.g. R=15) are used in the case of grids having a high number of lines. It is disadvantageous when using such grids in connection with digital image detectors, however, that the distance tolerance range, that is to say the range within which a defocusing which still leads to acceptable images may be given, is significantly limited compared with the e.g. moving grids with lower shaft ratios in customary film systems. This limited distance tolerance range demands a consistent changing of the grids in the event of a changing film-focus distance, that is to say the distance of the focus of the beam source from the solid-state image detector. However, changing the grid is time-consuming and does not permit a continuous workflow in the context of examining patients. Furthermore, it is necessary to keep in each case different grids which are focused with respect to different film-focus distances, in order, by way of example, to be able to cover a customary distance range of 115 cm to 180 cm. An embodiment of the invention is thus based on the problem of specifying a method and/or an apparatus which reduces or even eliminates at least one of the problems mentioned. An embodiment of the invention provides for at least some of the signals supplied in pixelwise fashion to be amplified via the amplifying device in a manner dependent on the actual distance of the antiscatter grid from the focus. The method according to an embodiment of the invention proposes electronically compensating for the disturbance component resulting solely from the defocusing, that is to say the defocusing-dictated dose attenuation, which is manifested in correspondingly weaker pixel signals. This can be done by amplifying at least some of the signals that are attenuated in disturbance-dictated fashion by use of the amplifying device assigned to a customary radiation detector. This makes it possible, depending on what is demanded and required, to be able to compensate for the defocusing-dictated disturbance by virtue of the fact that precisely the focusing-dictated weaker signals are elevated and, consequently, electronically adapted and compensated for. This makes it possible to establish a noise which becomes somewhat stronger toward the edge of the solid-state image detector, but this is tolerable with regard to the technological gain in terms of information and work. It is thus ideally possible to be able to compensate for almost the entire defocusing-dictated signal attenuation by this device over the entire detector area or area of the pixel matrix. The compensation according to an embodiment of the invention acts in addition to the “flat field” correction which is customary in digital image detectors and is used to correct the dose attenuation resulting from the square law of distance toward the detector edge. Thus, both the customary flat field correction and the defocusing-dictated correction can be achieved using the method according to an embodiment of the invention. As a result, it is possible to use one and the same grid, focused to a specific film-focus distance, over the entire routine work range (e.g. from 100 cm to 200 cm film-focus distance). Continuous work is thus possible; the manual change activities, which are laborious and interrupt the examination flow, are thus no longer incurred. Solid-state image detectors are discussed hereinafter, but any other type of digital radiation image receiver may be used instead of such an image detector. According to a first refinement according to an embodiment of the invention, it may be provided that the pixel-related gain factors are determined computationally for the given actual distance of the antiscatter grid from the focus relative to the original focusing distance. The gain factors by which each individual pixel signal is amplified are thus calculated according to this refinement of an embodiment of the invention. Parameters required for calculating the gain factors, such as grid-specific values (shaft ratio, focusing distance of the grid, the actual film-focus distance, the detector sensitivity, etc.), are available in solid-state image detector systems, so that it is possible to have recourse to the known formulae already revealed in the abovementioned specification IEC/DIN 60627. On the basis thereof, it is possible to determine the actual defocusing-dictated signal attenuation profile with respect to a given actual distance of the grid from the focus and thus to determine the local pixel-related signal attenuation or the magnitude thereof. This in each case relative to an exposure without an examination object, that is to say if only the antiscatter grid is arranged in the beam path. On the basis of these local pixel gain factors, it is then possible to amplify each pixel signal of the actual radiation image recording of the examination object in accordance with the defocusing attenuation stemming solely from the antiscatter grid. By contrast, an alternative to the computational determination of the gain factors provides for the pixelwise gain factors to be chosen from a table assigned to the actual distance of the antiscatter grid from the focus. In this refinement of an embodiment of the invention, a plurality of correction tables are stored in the amplifying device, the correction tables having been recorded for specific distances of a focused antiscatter grid from the focus. For the recording of the correction tables, only the antiscatter grid is situated at the respectively chosen distance that deviates from the focusing distance in the beam path. This yields a signal profile over the pixel matrix which reproduces the defocusing-dictated signal attenuation. Corresponding pixel-related gain factors can then be determined therefrom and are combined in the final correction table. If the actual distance of the grid from the focus is then known, the correction table assigned to this actual distance or the correction table nearest to it (in the absence, with respect to the actual distance, of a correction table which was created in the case of precisely this distance) is chosen, and use is made of those gain factors from the table which are assigned to the pixel signals that are actually to be amplified. In this case, the respective gain factor, as can be taken from the table, may be adapted computationally in the case of a difference between the actual distance and the distance on which the table is based. Since, as described, generally only a specific number of tables have been recorded with respect to specific distances, and the actual distance does not have to correspond to the distance on which the correction table is based, it is possible in this way to effect a computational adaptation, if appropriate by suitable interpolation between the values of two nearest distance-specific tables, etc. In accordance with an expedient development of the concept of an embodiment of the invention, it may be provided that only the pixel signals of those pixels whose signals—relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid without a transillumination object situated in the beam path—lie below a predetermined threshold value are amplified. As explained above, radiation images with a dose decrease of up to at most 40% are deemed still acceptable. If it then emerges that the actual defocusing of the antiscatter grid with respect to the chosen focus distance leads to a greater attenuation than the aforementioned 40% e.g. only in narrow pixel matrix regions at the opposite detector edges, it is also the case that in the context of the compensation, only the pixel signals of these signals which are attenuated to a greater extent than by 40% are amplified. In this case, the threshold value may define a defocusing-dictated attenuation of 40%, as provided in accordance with the specification, but also less, depending on the design. A correspondingly expedient refinement of an embodiment of the invention furthermore provides for the signals to be amplified by the gain factors to a predetermined threshold value. This also makes use of the fact that still acceptable images are present in the case of a signal decrease of up to 40%. Pixel signals which are attenuated to a greater extent are now not elevated to 100%, but only for example to 60%, that is to say that effectively a signal decrease with respect to the elevated pixel of only a permissible 40% is present. This leads on the one hand to an acceptable radiation image; on the other hand, the amplification-dictated noise is within fully acceptable limits. It goes without saying that it is possible also to choose other threshold values, e.g. 70% or 80%. It is expedient in this case if the threshold value (be it the one which defines the pixel signals which are to be elevated, or the threshold value which defines the gain limit) is adjustable, that is to say can thus be chosen during operation. In addition to the method according to an embodiment of the invention, an embodiment of the invention furthermore relates to an apparatus for radiation image recording. In a particular embodiment, it relates to one suitable for carrying out the method. The apparatus of one embodiment of the invention includes a beam source, a digital radiation image detector with radiation-sensitive pixels arranged in matrix form with an assigned device for the pixelwise amplification of the pixel signals, and an antiscatter grid, which is arranged between beam source and radiation image detector and is focused with respect to a specific distance from the focus of the beam source. This apparatus is distinguished, according to an embodiment of the invention, by the fact that the device is designed for the compensation of image disturbances caused by a defocusing of the antiscatter grid, which image disturbances are caused by a defocusing-dictated attenuation of the primary radiation incident on the radiation image detector, for the pixelwise amplification of at least some of the signals supplied in a manner dependent on the actual distance of the antiscatter grid from the focus. In this case, the device may be designed for the computational determination of the pixel-related gain factors for the given actual distance of the antiscatter grid from the focus relative to the original focusing distance. This additional amplification is one in addition to the flat field correction which is to be performed in any case by the amplifying device and which serves to compensate for the attenuation governed by the square law of distance toward the edge. As an alternative to the computational determination (or in addition thereto), one or a plurality of tables with pixel-specific gain factors, said tables being assigned to one or a plurality of specific distances of the antiscatter grid from the focus, may be stored in the device, the device choosing the pixelwise gain factors from a table assigned to the actual distance of the antiscatter grid from the focus. In this case, the device may be designed for the computational adaptation of the gain factors taken from the chosen table in the case of a difference between the actual distance and the distance on which the table is based. By way of example, in the case of an antiscatter grid focused at a film-focus distance of 150 cm, correction tables are created with respect to the distances 170 cm, 190 cm and 130 cm, 110 cm, respectively. In order, then, to obtain an optimum amplification in the case of an actual distance which lies between these values, the gain factors which are taken from the nearest table and are to be processed can be adapted computationally, e.g. in a manner dependent on the difference “actual distance:table distance”, etc. Finally, the device may be designed for the amplification of the pixel signals only of those pixels whose signals—relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid without a transillumination object situated in the beam path—lie below a predetermined threshold value, it being possible for the threshold value to define a defocusing-dictated attenuation of 40% or less. It is also conceivable to design the device for the amplification of the signals to a predetermined threshold value which lies below 100% relative to the signal that has been corrected by way of the flat field correction which has been determined in the context of an earlier calibration. In this case, too, the threshold value may define a signal attenuation of 40% or less and may be adjustable like the abovementioned threshold value. The antiscatter grid itself may be a linear grid having focused absorption lamellae. Moreover, a cell grid with a carrier structure defining the focused rectangular cells with a beam passage opening with an absorption coating applied to the inner sides of the carrier structure which face the beam passage openings may also be involved. Such cell grids are formed from radiation-transparent polymer resin e.g. in a rapid prototype method using the stereolithography technique. FIG. 1 shows, in the form of a schematic sketch, an apparatus 1 according to an embodiment of the invention for radiation image recording. This apparatus includes a radiation source 2 with a focus 3, a solid-state radiation detector 4 with a multiplicity of pixels 5 (e.g. approximately 3000×3000 pixels), and also a device 6 assigned to the solid-state radiation detector 4 and serving for recording the pixel-generated signals, for processing the latter and for creating a radiation image that can be output at a monitor 7. Arranged in the beam path 8, which clearly diverges proceeding from the focus, is an antiscatter grid 9, in the form of a linear grid in the exemplary embodiment shown, having a multiplicity of absorption lamellae 10 which are oriented with respect to the focus 3. A focused linear grid is thus involved. This focused antiscatter grid 9 absorbs scattered radiation which is scattered in the course of radiating through an object 11 situated in the beam path, since the antiscatter grid essentially transmits only the primary radiation that is not scattered, that is to say runs rectilinearly from the focus to the solid-state image detector 4. The antiscatter grid 9 is focused and centered with respect to a specific distance of the focus 3 from the area of the pixel matrix 5. If the distance then changes, that is to say if the radiation source 2 is moved nearer to or away from the solid-state image detector 4, the antiscatter grid 9 is situated in a defocused position, that is to say the absorber lamellae are no longer oriented exactly with respect to the focus 3. This has the effect that, with increasing defocusing, the proportion of primary radiation which is likewise absorbed undesirably by way of the absorber lamellae 10 increases. That is to say the imaging primary radiation dose that impinges on the pixel matrix 9 is consequently reduced. The dose decrease occurs to an intensified extent toward the edge and to a significantly lesser extent in the image center, since hardly anything changes at the absorber lamellae 10, which are essentially perpendicular in the image center region, with regard to their orientation with respect to the focus even in the defocused case. FIG. 2 shows, in the form of a schematic diagram, the profile of the pixel signals over the area of the pixel matrix 5, 3000 pixels being provided here in a detector direction perpendicular to the course of the absorber lamellae of the grid. The local pixel position is plotted along the abscissa and the signal intensity is plotted along the ordinate. At 100%, no attenuation whatsoever is present. The illustration shows three curves I, II and III. Curve I, which runs near to the 100% line, is the curve obtained if the antiscatter grid 9 is arranged exactly at the focusing distance. A minimal attenuation, governed by the square law of distance, results toward the edge. This intrinsic attenuation is compensated for by way of the device 6, to be precise computationally in the context of a global gain correction, where the divergence-dictated attenuation is compensated for. For this purpose, firstly a first calibration is carried out, in the context of which only a copper filter is introduced into the beam path; the antiscatter grid 9 is not situated in the beam path. A signal curve is then recorded which exclusively shows the actually unattenuated signals and from which it is then possible to identify the dose decrease toward the edge. This dose decrease that results here is detected and compensated for in the context of the flat field correction. FIGS. 2 and 3 show the curves in each case taking account of said flat field correction and specify only the focusing-dictated attenuation. As described, curve I shows the signal profile after flat field correction with an antiscatter grid situated at the focusing distance. Curve II shows the signal profile if the distance of the focus 3 from the pixel matrix 5 is increased, that is to say the beam source 2 is moved away from the solid-state image detector 4. An ever-increasing attenuation can be seen there towards the edge regions, which attenuation, in the example shown, goes to somewhat less than 80% at the edge, in other words an attenuation of somewhat more than 20% is present at the edge. Proceeding from a focusing distance, to which the antiscatter grid 9 is focused, of e.g. 150 cm, curve II shows the exemplary case for a distance of 180 cm. Curve III then shows the signal profile when the distance is shortened, that is to say if the beam source 2, proceeding from the focusing distance, is moved toward the solid-state image detector 4, e.g. to a distance of 115 cm. In this case, the dose decrease becomes significantly greater toward the edge since the clear width of the channels between the absorber lamellae 10 decreases to a significantly greater extent than when the distance is increased. The dose decrease amounts to up to approximately 50% in the edge regions. The method according to an embodiment of the invention and also the apparatus according to an embodiment of the invention now permit this defocusing-dictated signal decrease to be compensated for as far as necessary. For this purpose—see FIG. 1—either different correction tables 12 are stored in the device 6, pixel-specific gain factors by which the signals of the exemplary curves II and III are amplified being stored in said correction tables. As an alternative to this, the device may also be designed for purely computational determination of the gain factors on the basis of the formula or the computation algorithm 13. In the first-mentioned case, two correction tables which have been determined prior to the actual image recording in calibration recordings are present in the example shown. For this purpose, no object is situated in the beam path, but rather only the antiscatter grid 9 which is positioned at specific defocused distances. The focus distance from the pixel matrix was 120 cm in the case of the table T120, and it was 180 cm in the case of the table T180. For compensation purposes, that table which is nearest to the actual distance is then chosen, depending on the actual distance present. With regard to curve II, for compensation purposes, the table T180 is chosen since the actual distance on which curve II is based corresponds to the correction table distance. In the case of curve III the table T120 is chosen, the actual distance of 115 cm not corresponding to the correction table distance in this case. The correction tables 12 store, for each pixel, the corresponding gain factor by which the pixel signal must be amplified in order to compensate the focusing-dictated signal attenuation to a desired value. Since the actual distance and the table distance correspond with respect to curve II, the gain factors of this table can be used directly. In the case of curve III and the table T120, it is necessary for the gain factors of this table to be adapted computationally somewhat in order to be able to compensate for the difference between the actual distance and the table distance (115 cm to 120 cm). Various method variants are conceivable with regard to the compensation, and these are illustrated with respect to curve III. Firstly, there is the possibility of amplifying only those pixel signals which lie below a specific threshold value or threshold value signal. A first threshold value signal S1 corresponding to 60% signal or 40% attenuation was chosen in the example shown in accordance with FIG. 2. As represented by the arrow a, only the pixel signals which lie below this threshold value S1 are elevated in the context of the signal amplification. These signals can then be amplified to any desired value; FIG. 3 illustrates the case where the pixel signals are amplified to precisely the threshold value S1, thus resulting in the curve III′ shown in FIG. 3. Moreover, it is possible, of course, for these pixel signals that are to be amplified also to be elevated further, e.g. to a second threshold value. The latter may be chosen depending on the design of the apparatus; it may also be set on site, if appropriate. Furthermore, FIG. 2 shows a second threshold value S2, which corresponds to 80% signal strength or 20% attenuation in the example shown. The arrows b show that once again only those pixel signals which are attenuated by more than 20%, that is to say lie below S2, are elevated. The resultant amplified curve II′ is likewise illustrated in FIG. 3. This amplification clearly permits sufficient compensation of the defocusing-dictated signal attenuation. If an object is then examined, a signal profile which deviates from the signal profiles without an examination object as shown in FIG. 2 and which is dependent on the object attenuation is obtained, of course, over the entire pixel matrix. It is known from the correction tables, however, how the actual defocusing-dictated attenuation, which occurs in addition to the actual object attenuation and represents a disturbance component, affects the signals. The actual object image signals are then correspondingly elevated—insofar as they are to be elevated in accordance with the correction tables—so that ultimately only signals which essentially correspond to the actual object attenuation or reproduce the latter are used for the actual image generation. The same correction may also be effected using the formula identified by 13 or said algorithm. This makes it possible, from the knowledge of the actual distance of the focus 3 from the pixel matrix 5 and also the knowledge of the relevant grid parameters, to determine the respective attenuation which occurs in defocusing-dictated fashion in the case of this actual distance and to determine the gain factors computationally without the need to store the correction tables already described. The calculation of the attenuation profile over the detector area may be effected on the basis of the following formulae: V1 = r * c * ( f0 - f1 ) f0 * f1 and ( I ) V2 = r * c * ( f2 - f0 ) f2 * f0 ( II ) The following are applicable in this case: V1, V2=attenuation r=shaft ratio c=horizontal distance from the grid center in cm (location of the attenuation to be calculated). f0=focusing distance in cm f1, f2=actual distance of the grid from the focus in cmwhere V1 denotes the attenuation in the case where the distance is shortened below the focusing distance (f1<f0) and V2 denotes the attenuation in the case where the distance is increased above the focusing distance (f2>f0). On the basis of formulae (I) and (II), it is possible to calculate the profile of the attenuation in a manner dependent on the actual distance for each relevant point in the horizontal direction. Since the central ray defines the center, in the case of a detector having an edge length of 40 cm, the value c is chosen from the interval of 0 to +/−20 cm depending on a predetermined pitch, e.g. in 1 cm steps. The actual distance of the grid from the focus, which is detected by means of a suitable position sensor system, is detected as f1 and f2, respectively. Either the formula (I) or (II) is chosen depending on whether the actual distance is greater or less than f0. If the actual attenuation at the point respectively considered is known, which attenuation has a linear profile in the case of calculation, it is possible to determine for each point considered whether or not it is to be amplified. By way of example, only those points or pixel signals which lie below the threshold value described, e.g. of 40% attenuation, are amplified. Depending on the configuration of the amplification mode, the signals to be elevated may then be amplified e.g. to a second threshold value, e.g. to the abovementioned 40%, so that overall specification-conforming image data are still present or a standard-conforming image can be generated. For this purpose, for each signal that is actually to be amplified, the relevant gain factor which enables the desired amplification is determined from the actual attenuation factor given. This is then processed together with the global gain factor. FIG. 4 shows by way of example the attenuation profile for a few selected defocusing distances. The focusing distance was assumed to be 150 cm. The illustration additionally shows the attenuation profiles for the distances f2=160 cm, 170 cm and 180 cm. c, that is to say the distance from the central ray in mm, is plotted along the abscissa, only the values for f2 at 10 mm distances being illustrated by way of example. The attenuation V2 is specified along the ordinate. The illustration shows only part of the overall attenuation profile in the “positive” c direction; the curves run with an opposite gradient for the other half of the diagram. The attenuation curves clearly have a linear profile. The attenuation curve at the focusing distance necessarily runs precisely on the abscissa, while the gradient increases as the defocusing distance increases. The same behavior results if the actual distance is shortened below the focusing distance. Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
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039649652 | summary | BACKGROUND OF THE INVENTION A pressurized-water reactor installation includes the reactor pressure vessel containing the core which heats the pressurized-water coolant circulated through the pressure vessel via a pipeline loop extending through a steam generator producing steam as useful power, and from there via a main coolant pump, back to the pressure vessel. A branch pipeline loop shunts a portion of the circulating water coolant around the main coolant pump and through a water coolant purification system, about from 10 to 20% of the circulating water coolant passing continuously through this purification system during operation of the reactor. A part of this purification system is a degassing facility wherein the water coolant is decompressed and cooled so that gases separate. These gases are mainly hydrogen, nitrogen and oxygen. However, in addition to the above three gases the separated gases include the noble gases krypton and xenon which are present in volumes that are very small as compared to the volume of the other gases but which mandatorily prevent disposal of the separated gases by discharging them to the atmosphere. The one prior art suggestion has been to store the separated gases under pressure in decay tanks for a time depending on the half-life of the radioactive noble gases and to thereafter discharge the gases to the atmosphere via a tall exhaust air stack through which is also discharged the exhaust air from the spherical steel containment vessel enclosing the entire reactor installation. However, this practice has been prevented by current, more stringent environmental protection regulations. Therefore, the operation of a pressurized-water reactor installation has presented the problem of disposing of the gases separated from the water coolant during its purification, in a manner that is economically feasible and entirely safe from the environmental pollution viewpoint. SUMMARY OF THE INVENTION The object of the present invention is to provide a solution to the above problem and this has been achieved in the following manner: Basically, the concept of the invention is that separation and isolation of the noble gases permits the other gases to be disposed of free from problems connected with radioactivity. The noble gases are included by the other gases in such small amounts that their isolation might be effected by storage in a tank or tanks which may be of small volumetric capacity while still capable of accepting all of the noble gases resulting from full reactor operation periods which may extend for as much as one year. In the case of a pressurized-water reactor installation operating as a power reactor of 1000 MWe for an operational period of one year, the noble gases can be stored in a steel bottle containing activated carbon and having a volumetric capacity of less than 1m.sup.3, a volumetric capacity of 0.1m.sup.3 or smaller being preferred. This is a very miniaturized tank as compared to the decay tanks required for storage of the gases by the prior art proposal previously referred to. In addition to the above advantage, the invention further involves combining the separated oxygen with a portion of the hydrogen and sending the balance of the hydrogen to the water coolant gas-charging system to provide the coolant with the hydrogen excess desired in the case of light-water reactors in general, and in particular, a pressurized-water reactor. Nitrogen is also added to the coolant by this gas-charging system and the separated nitrogen may be sent to this system for use there, or safely discharged to the atmosphere. |
description | The present invention relates to a water-chamber working apparatus that performs a predetermined work in a water chamber of a steam generator. As for a work in a water chamber of a steam generator provided in a nuclear plant, it is desired that the workload of workers is reduced. Therefore, conventionally, there is a technique of performing a work in a water chamber by introducing a water-chamber working apparatus into the water chamber and remote-controlling the water-chamber working apparatus. For example, Patent Literature 1 discloses a remote testing apparatus that performs flaw testing of a number of heat transfer tubes of a steam generator. Patent Literature 1: Japanese Patent Application Laid-open No. H10-227765 According to the technique disclosed in Patent Literature 1, as shown in FIG. 2 thereof, a clamp shaft is inserted into a plurality of heat transfer tubes provided in the steam generator, thereby supporting a walking guide robot on a tube plate of the stream generator. That is, according to the technique disclosed in Patent Literature 1, the walking guide robot is suspended from the tube plate. In the following explanations, a device that moves along a tube plate like the walking guide robot in the technique disclosed in Patent Literature 1 is referred to as “movable body”. In a water-chamber working apparatus in which a movable body is suspended from a tube plate, it is designed so that the movable body does not fall from the tube plate, and remote control is performed carefully so that the movable body does not fall from the tube plate. In this way, when the movable body is suspended from the tube plate, designing of the movable body may become complicated or working hours may increase for carefully performing remote control of the movable body, in order to cause the movable body to follow the tube plate stably. The present invention has been achieved in view of the above problems, and an object of the present invention is to provide a water-chamber working apparatus that can stably support a movable body on a tube plate. According to an aspect of the present invention, a water-chamber working apparatus that performs a predetermined work inside a water chamber of a steam generator includes: a movable body that is configured to move along a tube plate of the steam generator; an extendable member that includes a first portion and a second portion and that extends and retracts in a direction in which the first portion and the second portion approach each other and a direction in which theses portions move away from each other, where the first portion is attached to a portion of the water chamber that is away from the tube plate via a first joint including two rotation axes intersecting with each other, and the second portion is attached to the movable body via a second joint including two rotation axes intersecting with each other, which are different from the rotation axes of the first joint; a first force application unit that applies a force in a direction in which the first portion and the second portion move away from each other to the extendable member; and a second force application unit that applies a force of rotating the extendable member centering around the first joint, which is a force to cause the second portion to approach to the tube plate, to the extendable member. According to the above configuration, a force in a direction in which the movable body itself approaches the tube plate is transmitted to the movable body according to the present invention via the extendable member, by a force generated by the first force application unit and the second force application unit. With this configuration, the movable body according to the present invention is pressed against the tube plate. Accordingly, the movable body can move stably along the tube plate without being suspended from the tube plate. Advantageously, in the water-chamber working apparatus, the second force application unit includes an electric motor, and a counterweight mechanism including a rod-like member for weight that is extended to a direction opposite to the second portion while using the first portion as a fulcrum, and a weight provided in a portion of the rod-like member for weight that is away from the first portion. By providing both the electric motor and the counterweight mechanism, the counterweight mechanism can decrease the magnitude of a force to be applied to the extendable member by the electric motor. Furthermore, the electric motor can decrease the magnitude of a force to be applied to the extendable member by the counterweight mechanism. With this configuration, the electric motor can be further downsized in the water-chamber working apparatus according to the present invention by providing both the electric motor and the counterweight mechanism in the water-chamber working apparatus as compared to a case of providing only the electric motor, because an output required for the electric motor is reduced. Further, in the water-chamber working apparatus according to the present invention, the mass of the weight can be further decreased or a distance between the weight and the first portion can be further decreased by providing both the electric motor and the counterweight mechanism in the water-chamber working apparatus as compared to a case of providing only the counterweight mechanism. Advantageously, in the water-chamber working apparatus, the electric motor increases the force to be applied to the extendable member as a distance between the first portion and the second portion increases, and decreases the force to be applied to the extendable member as the distance between the first portion and the second portion decreases. As the distance between the first portion and the second portion increases, a force required to be generated by the second force application unit increases. Therefore, in the water-chamber working apparatus according to the present invention, as the distance between the first portion and the second portion increases, the force to be applied to the extendable member by the electric motor is increased. On the other hand, as the distance between the first portion and the second portion decreases, the force required to be generated by the second force application unit is decreased. Therefore, in the water-chamber working apparatus according to the present invention, as the distance between the first portion and the second portion decreases, the force to be applied to the extendable member by the electric motor is decreased. Consequently, the water-chamber working apparatus according to the present invention can bring a force acting on the movable body close to an appropriate value. Advantageously, in the water-chamber working apparatus, the second force application unit is a counterweight mechanism including a rod-like member for weight that is extended to a direction opposite to the second portion while using the first portion as a fulcrum, and a weight provided in a portion of the rod-like member for weight that is away from the first portion. The counterweight mechanism can apply a force to the extendable member without requiring any electricity. As a result, the water-chamber working apparatus according to the present invention can support the movable body on the tube plate stably without requiring any electricity. Advantageously, in the water-chamber working apparatus, the rod-like member for weight extends and retracts in a direction in which the first portion and the weight approach each other and a direction in which the first portion and the weight move away from each other, and the water-chamber working apparatus comprises an arm-length adjustment unit that adjusts a distance between the first portion and the weight so that the distance between the first portion and the weight increases as a distance between the first portion and the second portion increases, and adjusts a distance between the first portion and the weight so that the distance between the first portion and the weight decreases as the distance between the first portion and the second portion decreases. By the above configuration, the water-chamber working apparatus according to the present invention can adjust the distance between the first portion and the weight. As the distance between the first portion and the second portion increases, a force required to be generated by the second force application unit increases. Therefore, the water-chamber working apparatus according to the present invention increases the distance between the first portion and the weight, as the distance between the first portion and the second portion increases. With this configuration, the water-chamber working apparatus according to the present invention can increase a force to be applied to the movable body by the second force application unit, which is a force in a direction in which the movable body approaches the tube plate. On the other hand, as the distance between the first portion and the second portion decreases, the force required to be generated by the second force application unit decreases. Therefore, as the distance between the first portion and the second portion decreases, the water-chamber working apparatus according to the present invention decreases the distance between the first portion and the weight. With this configuration, the water-chamber working apparatus according to the present invention can decrease the force to be applied to the movable body by the second force application unit, which is a force in the direction in which the movable body approaches the tube plate. Therefore, the water-chamber working apparatus according to the present invention can bring a force acting on the movable body close to an appropriate value. Advantageously, in the water-chamber working apparatus, the weight moves along the rod-like member for weight in a direction in which the weight approaches the first portion and a direction in which the weight moves away from the first portion, and the water-chamber working apparatus comprises a weight movement unit that moves the weight in a direction in which the weight moves away from the first portion as a distance between the first portion and the second portion increases, and moves the weight in a direction in which the weight approaches the first portion as the distance between the first portion and the second portion decreases. By the above configuration, the water-chamber working apparatus according to the present invention can adjust the distance between the first portion and the weight. Advantageously, in the water-chamber working apparatus, the weight is configured to include a container and liquid stored in the container, and the water-chamber working apparatus comprises a liquid-amount adjustment unit that increases an amount of the liquid in the container as a distance between the first portion and the second portion increases, and decreases an amount of the liquid in the container as the distance between the first portion and the second portion decreases. By the above configuration, the water-chamber working apparatus according to the present invention increases the mass of the container containing liquid, as the distance between the first portion and the second portion increases. With this configuration, the water-chamber working apparatus according to the present invention can increase the force to be applied to the movable body by the second force application unit, which is a force in the direction in which the movable body approaches the tube plate. On the other hand, the water-chamber working apparatus according to the present invention decreases the mass of the container containing liquid, as the distance between the first portion and the second portion decreases. With this configuration, the water-chamber working apparatus according to the present invention can decrease the force to be applied to the movable body by the second force application unit, which is a force in the direction in which the movable body approaches the tube plate. Therefore, the water-chamber working apparatus according to the present invention can bring a force acting on the movable body close to an appropriate value. Advantageously, in the water-chamber working apparatus, the second force application unit is an electric motor. While the counterweight mechanism requires the rod-like member for weight, the electric motor does not require any rod-like member. Therefore, the water-chamber working apparatus according to the present invention can possibly further downsize the entire apparatus when including only the electric motor as compared to a case of including the counterweight mechanism, because the rod-like member can be omitted. Advantageously, in the water-chamber working apparatus, the first force application unit is an extension device capable of adjusting an amount of extension and retraction, and adjusts a length of the extendable member by following a movement of the movable body. For example, the extension device is a cylinder device or an actuator device. The water-chamber working apparatus according to the present invention detects a position of the movable body, and controls operations of the extension device so that the length of the extendable member becomes long, as the movable body moves away from the first portion. Furthermore, the water-chamber working apparatus controls operations of the extension device so that the length of the extendable member becomes short, as the movable body approaches the first portion. In this case, for example, when the movable body attempts to move against a force applied to the movable body by the first force application unit, the first force application unit decreases the length of the extendable member, so that the movable body can move easily. As a preferred mode of the present invention, it is desired that the movable body performs, as a predetermined work, Eddy-current testing for probing a flaw formed in a heat transfer tube provided in the steam generator. As a preferred mode of the present invention, it is desired that the movable body clamps the heat transfer tube. When the water-chamber working apparatus performs Eddy-current testing, the movable body receives a force in a direction in which the movable body itself moves away from the heat transfer tube (a reaction force) from a probe. Therefore, when the movable body does not clamp the heat transfer tube, in the water-chamber working apparatus, the second force application unit needs to create a force against the reaction force. However, when the movable body clamps the heat transfer tube, the movable body is fixed to the tube plate by the clamping the heat transfer tube. Accordingly, in the water-chamber working apparatus according to the present invention, the second force application unit does not need to create a force against the reaction force. The water-chamber working apparatus can stably support a movable body on a tube plate. The present invention is explained below in detail with reference to the accompanying drawings. The present invention is not limited to the following explanations. In addition, constituent elements in the following descriptions include those that can be easily assumed by persons skilled in the art, that are substantially equivalent, and so-called equivalents. (First Embodiment) FIG. 1 is a perspective view of an entirety of a water-chamber working apparatus according to a first embodiment. As shown in FIG. 1, a steam generator 10 has a water chamber 11. The water chamber 11 is a space enclosed by a tube plate 12 and a hemispherical wall surface 13. The tube plate 12 is arranged vertically above the hemispherical wall surface 13. The tube plate 12 is provided substantially horizontally, for example. A plurality of heat transfer tubes 14 open in the tube plate 12. A maintenance hatch 15 connecting the inside and outside of the water chamber 11 is formed on the hemispherical wall surface 13. A water-chamber working apparatus 1 according to the present embodiment shown in FIG. 1 performs a predetermined work in the water chamber 11. In the present embodiment, it is assumed that the predetermined work is Eddy-current testing (ECT) as an example. The Eddy-current testing is a work of probing a flaw formed in the heat transfer tube 14. As shown in FIG. 1, the water-chamber working apparatus 1 includes a movable-body support device 20 and a flaw detector 30. FIG. 2 is an enlarged perspective view of a vicinity of a movable body provided in the flaw detector according to the first embodiment. As shown in FIG. 2, the flaw detector 30 includes a movable body 31 and a movable-body control device 32. An example of the configuration of the movable body 31 is explained below. The movable body 31 includes a frame 33, a wheel 34, a running electric motor 35, a running-direction-changing electric motor 36, and a probe support body 37. The wheel 34 is attached to the frame 33 so as to be able to rotate on a wheel axle. The wheel 34 is supported by the frame 33 so that an angle of the wheel axle with respect to the frame 33 can be changed on a virtual plane parallel to the tube plate 12. The running electric motor 35 applies a rotative force centering around the wheel axle to the wheel 34. The running-direction-changing electric motor 36 adjusts an angle of the wheel axle with respect to the frame 33 on the virtual plane parallel to the tube plate 12. The probe support body 37 is attached to the frame 33. A probe 38 for Eddy-current testing is attached to the probe support body 37 and the probe support body 37 supports the probe 38 with respect to the frame 33. The probe 38 moves along the tube plate 12 together with the frame 33 due to the rotation of the wheel 34 in a state of contacting with the tube plate 12. The movable-body control device 32 controls operations of the movable body 31. Specifically, the movable-body control device 32 is electrically coupled with the running electric motor 35, the running-direction-changing electric motor 36, and other movable devices to control operations of these movable bodies. When performing Eddy-current testing, first, the movable-body control device 32 controls operations of the running electric motor 35 and the running-direction-changing electric motor 36 so that the heat transfer tube 14 to be subjected to the Eddy-current testing and the probe 38 face each other, and moves the frame 33. For example, the movable-body control device 32 regulates rotation of a rotor of the running electric motor 35 to regulate rotation of the wheel 34, or inserts a rod-like member coupled with the frame 33 into another heat transfer tube 14 different from the heat transfer tube 14 to be subjected to the Eddy-current testing, thereby regulating the movement of the frame 33 along the tube plate 12. In this state, the flaw detector 30 performs the Eddy-current testing. When the Eddy-current testing of the heat transfer tube 14 as a current testing target is complete, the movable-body control device 32 controls operations of the running electric motor 35 and the running-direction-changing electric motor 36 so that the heat transfer tube 14 to be subjected to the Eddy-current testing next and the probe 38 face each other, and moves the frame 33 of the movable body 31. The flaw detector 30 repeats the above operations until the Eddy-current testing is performed on all the heat transfer tubes 14. A configuration of the movable-body support device 20 is explained next. The movable-body support device 20 includes an extendable member 21, an extrusion spring 22 as a first force application unit, a first universal joint 23a as a first joint, a second universal joint 23b as a second joint, and a supporting electric motor 24 as a second force application unit. The extendable member 21 shown in FIG. 1 is a rod-like member. The extendable member 21 extends and retracts in a direction of a central axis of the rod-like member (a longitudinal direction of the rod-like member). A mechanism for extending and retracting the extendable member 21 is not particularly limited. For example, the extendable member 21 includes a hollow first rod-like member 21a, a hollow second rod-like member 21b, and a third rod-like member 21c. At least a part of the third rod-like member 21c is accommodated in a hollow part of the second rod-like member 21b, and the third rod-like member 21c can move in the direction of the central axis of the extendable member 21 with respect to the second rod-like member 21b. At least a part of the second rod-like member 21b is accommodated in a hollow part of the first rod-like member 21a, and the second rod-like member 21b can move in the direction of the central axis of the extendable member 21 with respect to the first rod-like member 21a. Accordingly, the extendable member 21 extends and retracts by an amount of increase and decrease of the part of the second rod-like member 21b protruding from the hollow part of the first rod-like member 21a. Furthermore, the extendable member 21 extends and retracts by an amount of increase and decrease of the part of the third rod-like member 21c protruding from the hollow part of the second rod-like member 21b. In the extendable member 21, a first coupling portion 21d as a first portion is coupled with the maintenance hatch 15 of the steam generator 10 via the first universal joint 23a, and a second coupling portion 21e as a second portion is coupled with the frame 33 of the movable body 31 via the second universal joint 23b. The first coupling portion 21d is a part of the first rod-like member 21a, and in the present embodiment, is an end of the first rod-like member 21a on a side of the maintenance hatch 15. The second coupling portion 21e is a part of the third rod-like member 21, and in the present embodiment, it is an end of the third rod-like member 21c on a side of the tube plate 12. The extrusion spring 22 is coupled with the first rod-like member 21a at one end, and with the third rod-like member 21c at the other end. Accordingly, the extrusion spring 22 applies a force F1 to the extendable member 21 in a direction in which the first coupling portion 21d and the second coupling portion 21e move away from each other. The first coupling portion 21d does not move with respect to the maintenance hatch 15, but the second coupling portion 21e moves with respect to the first coupling portion 21d. Accordingly, the extrusion spring 22 practically applies the force F1 to the extendable member 21 so that the extrusion spring 22 pushes the second coupling portion 21e to move away from the first coupling portion 21d. The water-chamber working apparatus 1 can be provided with an extension device that can adjust an extension amount thereof as the first force application unit instead of the extrusion spring 22. The extension device is, for example, a cylinder device or an actuator device that uses gas or liquid as a working fluid. In the case of the extrusion spring 22, the magnitude of the force F1 to be generated is changed according to the extension amount of the extendable member 21. On the other hand, in the extension device, there is an effect that the magnitude of the force F1 to be generated is less likely to be changed, even when the extension amount of the extendable member 21 changes. Furthermore, when the first force application unit is the extension device, the extension device can be controlled such that the length of the extendable member 21 is changed, following the movement of the movable body 31. Specifically, the movable-body support device 20 detects the position of the movable body 31, and controls operations of the extension device so that the length of the extendable member 21 becomes longer, as the movable body 31 moves away from the first coupling portion 21d. Further, the movable-body support device 20 controls operations of the extension device so that the length of the extendable member 21 becomes shorter, as the movable body 31 approaches the first coupling portion 21d. In this case, for example, when the movable body 31 is to move against the force F1, the extension device shortens the length of the extendable member 21. Accordingly, the movable body 31 can move more easily. However, the extrusion spring 22 generally has a small mass and is smaller than the extension device. Further, operations of the extrusion spring 22 do not need to be controlled. Accordingly, in the present embodiment, the water-chamber working apparatus 1 includes the extrusion spring 22. FIG. 3 is an enlarged perspective view of a vicinity of a maintenance hatch in the movable-body support device according to the first embodiment. As shown in FIG. 3, the first universal joint 23a has two rotation axes of a first rotation axis R1 and a second rotation axis R2. The first universal joint 23a supports the extendable member 21 with respect to the maintenance hatch 15 so that the extendable member 21 can be rotated around the first rotation axis R1. Furthermore, the first universal joint 23a supports the extendable member 21 with respect to the maintenance hatch 15 so that the extendable member 21 can be rotated around the second rotation axis R2. The first rotation axis R1 and the second rotation axis R2 intersect with each other. The first rotation axis R1 and the second rotation axis R2 can intersect with each other on one virtual plane or three-dimensionally. In the present embodiment, it is assumed that the first rotation axis R1 and the second rotation axis R2 intersect with each other on one virtual plane. Further, while the intersecting angle of the first rotation axis R1 and the second rotation axis R2 is not particularly limited, in the present embodiment, it is assumed that the intersecting angle is 90 degrees. Further, in the present embodiment, the first rotation axis R1 is, for example, parallel to the tube plate 12 shown in FIG. 1. The second universal joint 23b shown in FIG. 2 has two rotation axes of a first rotation axis R3 and a second rotation axis R4. The second universal joint 23b couples the extendable member 21 with the movable body 31 so that the extendable member 21 can be rotated around the first rotation axis R3 with respect to the movable body 31. Furthermore, the second universal joint 23b couples the extendable member 21 with the movable body 31 so that the extendable member 21 can be rotated around the second rotation axis R4. The first rotation axis R3 and the second rotation axis R4 intersect with each other. The first rotation axis R3 and the second rotation axis R4 can intersect with each other on one virtual plane or three-dimensionally. In the present embodiment, it is assumed that the first rotation axis R3 and the second rotation axis R4 intersect with each other on one virtual plane. Further, while the intersecting angle of the first rotation axis R3 and the second rotation axis R4 is not particularly limited, in the present embodiment, it is assumed that the intersecting angle is 90 degrees. Further, in the present embodiment, the first rotation axis R3 is, for example, parallel to the tube plate 12 shown in FIG. 1. The supporting electric motor 24 shown in FIGS. 1 and 3 applies a force of rotating the extendable member 21 around the first universal joint 23a as a fulcrum, which is a force in a direction in which the second coupling portion 21e of the extendable member 21 shown in FIG. 1 approaches the tube plate 12, to the extendable member 21. Specifically, in the supporting electric motor 24, as shown in FIG. 3, a rotor that rotates on the first rotation axis R1 is coupled with a member on a side of the extendable member 21 and a stator is coupled with a member on a side of the maintenance hatch 15. With this configuration, when the rotor rotates on the first rotation axis R1, the supporting electric motor 24 applies a force in a direction in which the second coupling portion 21e approaches the tube plate 12 to the extendable member 21. Accordingly, the movable-body support device 20 presses the movable body 31 coupled with the second coupling portion 21e toward the tube plate 12 via the extendable member 21. As shown in FIGS. 1 and 3, the movable-body support device 20 further includes a counterweight mechanism 25 as the second force application unit. The counterweight mechanism 25 includes a rod-like member 25a for weight and a weight 25b. The rod-like member 25a for weight is coupled with the first rod-like member 21a. The rod-like member 25a for weight is extended to a direction opposite to the second coupling portion 21e shown in FIG. 1 while using the first coupling portion 21d as a fulcrum. The weight 25b is provided at a position away from the first coupling portion 21d of a portion of the rod-like member 25a for weight. A vertically downward force acts on the weight 25b due to the gravity. With this configuration, the force of rotating the extendable member 21 around the first universal joint 23a as a fulcrum, which is a force in the direction in which the second coupling portion 21e of the extendable member 21 approaches the tube plate 12, is applied to the extendable member 21 from the rod-like member 25a for weight. The movable-body support device 20 can include at least one of the supporting electric motor 24 and the counterweight mechanism 25. That is, the movable-body support device 20 can include only the supporting electric motor 24, can include only the counterweight mechanism 25, or can include both of the supporting electric motor 24 and the counterweight mechanism 25. However, by including both of the supporting electric motor 24 and the counterweight mechanism 25, the counterweight mechanism 25 can decrease the magnitude of the force to be applied to the extendable member 21 by the supporting electric motor 24. Furthermore, the supporting electric motor 24 can decrease the magnitude of the force to be applied to the extendable member 21 by the counterweight mechanism 25. With this configuration, the supporting electric motor 24 of the movable-body support device 20 can be further downsized by including both of the supporting electric motor 24 and the counterweight mechanism 25 as compared to a case of including only the supporting electric motor 24, because an output required for the supporting electric motor 24 is decreased. Further, the movable-body support device 20 can further decrease the mass of the weight 25b or can further decrease a distance between the weight 25b and the first coupling portion 21d by including both of the supporting electric motor 24 and the counterweight mechanism 25 as compared to a case of including only the counterweight mechanism 25. FIG. 4 is a schematic explanatory diagram of a force acting on a movable body. A force F shown in FIG. 4 is the gravity acting on the movable body 31. The force F1 is generated by the extrusion spring 22 shown in FIG. 1. A force F1y is a part of the force F1 acting in a vertical direction. A force F1x is a part of the force F1 acting in a direction along the tube plate 12. A force F2 is a force transmitted to the movable body 31 via the extendable member 21 shown in FIG. 3, and is a total force of a force applied to the extendable member 21 by the supporting electric motor 24 and a force applied to the extendable member 21 by the counterweight mechanism 25. A force F2y is a part of the force F2 acting in the vertical direction. A force F2x is a part of the force F2 acting in a direction along the tube plate 12. As shown in FIG. 4, the force F1y and the force F2y act on the movable body 31. When an angle formed by the extendable member 21 and the tube plate 12 changes, the force F1y and the force F2y respectively change. In the movable-body support device 20, the force F1 and the force F2 are adjusted in advance so that the total of the forces F1y and F2y becomes larger than the force F, at any angle of assumed angles formed by the extendable member 21 and the tube plate 12. That is, in the movable-body support device 20, a spring coefficient of the extrusion spring 22 shown in FIG. 1, an output of the supporting electric motor 24, the mass of the weight 25b, and the distance between the weight 25b and the first coupling portion 21d are adjusted in advance so that the total of the forces F1y and F2y is larger than the force F at all times. A force of a difference between the force F1x and the force F2x acts on the movable body 31 as a force in a direction along the tube plate 12. The force in the direction along the tube plate 12 is not a force for supporting the movable body 31 on the tube plate 12. Therefore, the force in the direction along the tube plate 12 is an unnecessary force. Accordingly, it is desired that a difference between the force F1x and the force F2x is small. However, the movable body 31 according to the present embodiment can regulate the movement of the frame 33 along the tube plate 12. Therefore, even when the force in the direction along the tube plate 12 acts on the frame 33, the movable body 31 can regulate the movement of the frame 33 (can maintain suspending of the frame 33). The wheel 34 transmits a force larger than the force along the tube plate 12 acting on the frame 33 via the extendable member 21 to the tube plate 12, thereby enabling to move the movable body 31 in a direction opposite to a direction of application of the force along the tube plate 12 acting on the frame 33 via the extendable member 21. A force directed vertically upward (the force F1y+the force F2y) acts on the movable body 31 while the extrusion spring 22 generates the force F1 and the supporting electric motor 24 and the counterweight mechanism 25 generate the force F2. This force (the force F1y+the force F2y) is larger than the gravity acting on the movable body 31. Therefore, the movable body 31 is pressed toward the tube plate 12 vertically upward. In this state, when the wheel 34 shown in FIG. 2 rotates, the frame 33 of the movable body 31 moves along the tube plate 12 against the force F1x and the force F2x shown in FIG. 4. When the movable body 31 moves, the extendable member 21 extends or retracts to follow the movement of the movable body 31. At this time, the force directed vertically upward (the force F1y+the force F2y) acts on the movable body 31. Accordingly, the movable body 31 is pressed toward the tube plate 12 vertically upward at all times. In this manner, the movable body 31 can move along the tube plate 12 without being suspended from the tube plate 12. As described above, because the movable body 31 is not suspended from the tube plate 12, a mechanism for clamping the heat transfer tubes 14 shown in FIG. 1 does not need to be provided. Furthermore, in a mode in which the movable body is suspended from the tube plate 12, the movable body 31 needs to be operated carefully so as not to fall. On the other hand, in the present embodiment, a vertically upward force acts on the frame 33 of the movable body 31 at all times. Accordingly, the movable body 31 according to the present embodiment can stably move along the tube plate 12. As a result, if the water-chamber working apparatus includes a movable body being suspended from the tube plate 12, the water-chamber working apparatus 1 can easily operate the movable body 31. Furthermore, the water-chamber working apparatus 1 according to the present embodiment also has a feature that if the spring coefficient of the extrusion spring 22, the output of the supporting electric motor 24, the mass of the weight 25b, and the distance between the weight 25b and the first coupling portion 21d are adjusted, the water-chamber working apparatus 1 according to the present embodiment does not need to adjust these values during a work. As described above, the total force of the force F1y and the force F2y shown in FIG. 4 is set to be larger than the force F at any angle of assumed angles formed by the extendable member 21 and the tube plate 12. Therefore, even when the movable body 31 moves along the tube plate 12, the movable body 31 is pressed against the tube plate 12 at all times. Accordingly, the water-chamber working apparatus 1 does not require any controller that controls operations of the movable-body support device 20. (Second Embodiment) FIG. 5 is an enlarged perspective view of a vicinity of a movable body according to a second embodiment. In a water-chamber working apparatus 2 according to the second embodiment shown in FIG. 5, the configuration of the movable body is different from that of the water-chamber working apparatus 1 according to the first embodiment shown in FIG. 1. The configuration other than the movable body of the water-chamber working apparatus 2 is identical to that of the water-chamber working apparatus 1 according to the first embodiment. In the following explanations, a direction on a virtual plane parallel to the tube plate 12 is designated as a first direction, and a direction orthogonal to the first direction is designated as a second direction. A movable body 40 shown in FIG. 5 includes a frame 41, a first movable portion 42, a second movable portion 43, a first thruster 44, and a second thruster 45. The frame 41 is coupled with the second coupling portion 21e of the extendable member 21 via the second universal joint 23b. The first movable portion 42 is attached to the frame 41 so as to be able to move in the first direction with respect to the frame 41. The second movable portion 43 is attached to the frame 41 so as to be able to move in the second direction with respect to the frame 41. The first thruster 44 is attached to the first movable portion 42 with a longitudinal direction thereof being the vertical direction. Furthermore, the first thruster 44 is attached to the first movable portion 42 so as to be able to move vertically upward and downward. The second thruster 45 is attached to the second movable portion 43 with a longitudinal direction thereof being the vertical direction. Further, the second thruster 45 is attached to the second movable portion 43 so as to be able to move vertically upward and downward. A specific example of a moving method of the movable body 40 is explained below. It is assumed that before start to move, both of the first thruster 44 and the second thruster 45 of the movable body 40 are inserted into the heat transfer tubes 14. When the movable body 40 is going to move in the first direction, the second thruster 45 of the movable body 40 is first moved vertically downward. Accordingly, the engagement between the second thruster 45 and the heat transfer tubes 14 is released. The first movable portion 42 then attempts to move in the first direction. At this time, the first movable portion 42 cannot move in the first direction because the first thruster 44 is inserted into the heat transfer tubes 14. Therefore, the frame 41 and the second thruster 45 move in the first direction. The second thruster 45 then moves vertically upward and engages with the heat transfer tubes 14. Accordingly, the movable body 40 finishes the movement in the first direction. On the other hand, when the movable body 40 is going to move in the second direction, the first thruster 44 is first moved vertically downward. Accordingly, the engagement between the first thruster 44 and the heat transfer tubes 14 is released. The second movable portion 43 then attempts to move in the second direction. At this time, the second movable portion 43 cannot move in the second direction because the second thruster 45 is inserted into the heat transfer tubes 14. Therefore, the frame 41 and the first thruster 44 move in the second direction. The first thruster 44 then moves vertically upward and engages with the heat transfer tubes 14. Accordingly, the movable body 40 completes the movement in the second direction. The water-chamber working apparatus 2 including the movable body 40 also exhibits identical effects to those of the water-chamber working apparatus 1 according to the first embodiment shown in FIG. 1. In addition, the water-chamber working apparatus 2 according to the present embodiment shown in FIG. 5 also exhibits an effect such that positioning of the movable body 40 is easier than the movable body 31 shown in FIG. 2. In the case of the movable body 31 including the wheel 34 shown in FIG. 2, adjustment of a rotation angle of the wheel 34 and a running direction of the frame 33 needs to be accurately performed so that the probe 38 and the heat transfer tube 14 are at opposite positions. However, because the movable body 40 according to the present embodiment can perform positioning of the movable body 40 by inserting the first thruster 44 and the second thruster 45 into the heat transfer tubes 14, the probe 38 and the heat transfer tube 14 can be easily made to face each other than the movable body 31 according to the first embodiment. As a device similar to the movable body 40 according to the present embodiment, there is a device in which a first thruster and a second thruster clamp the heat transfer tubes 14. However, the movable body 40 according to the present embodiment is pressed against the tube plate 12 by the movable-body support device 20. Therefore, the first thruster 44 and the second thruster 45 of the movable body 40 do not need to clamp the heat transfer tubes 14. Accordingly, because a clamping work of the heat transfer tubes 14 by the first thruster 44 and the second thruster 45 is not required, the movable body 40 can move more quickly along the tube plate 12. However, the movable body 31 according to the first embodiment and the movable body 40 according to the second embodiment can include a mechanism for clamping the heat transfer tubes 14 (hereinafter, “clamping mechanism”). In this case, the movable-body support device exhibits a new effect. The effect is explained below. When the water-chamber working apparatus 1 performs Eddy-current testing, the movable body receives a force in a direction in which the movable body itself moves away from the heat transfer tubes 14 (a reaction force) from the probe 38. Accordingly, when the movable body does not include the clamping mechanism, at least one of the supporting electric motor 24 and the counterweight mechanism 25 of the movable-body support device needs to generate a force against the reaction force. However, when the movable body includes the clamping mechanism, the movable body is fixed to the tube plate 12 by the clamping mechanism. Therefore, at least one of the supporting electric motor 24 and the counterweight mechanism 25 of the movable-body support device do not need to generate the force against the reaction force. Accordingly, at least one of the supporting electric motor 24 and the counterweight mechanism 25 of the movable-body support device can be downsized. (Third Embodiment) FIG. 6 is an explanatory diagram of a counterweight mechanism according to a third embodiment. A movable-body support device 50 according to the third embodiment includes, as shown in FIG. 6, a counterweight mechanism 51 as the second force application unit, and a counterweight control device 52. The counterweight mechanism 51 includes a cylinder device 53 as an arm-length adjustment unit and a weight 54. The cylinder device 53 operates by using, for example, gas or liquid as a working fluid. The cylinder device 53 includes a first member 53a and a second member 53b that protrudes from the first member 53a due to pressure of the working fluid. The weight 54 is provided in the second member 53b. The counterweight control device 52 adjusts a flow rate of the working fluid conducted to the cylinder device 53 and controls a protrusion amount of the second member 53b from the first member 53a. As a result, the counterweight control device 52 adjusts the distance between the weight 54 and the first coupling portion 21d. When the distance between the weight 54 and the first coupling portion 21d changes, the magnitude of the force F2 shown in FIG. 4 changes. Specifically, when the distance between the weight 54 and the first coupling portion 21d increases, the force F2 shown in FIG. 4 increases, and when the distance between the weight 54 and the first coupling portion 21d decreases, the force F2 shown in FIG. 4 decreases. On the other hand, as the distance between the first coupling portion 21d and the second coupling portion 21e increases, that is, the length of the extendable member 21 increases, a force required for pressing the movable body 31 against the tube plate 12 increases in the movable-body support device 50. Furthermore, in the movable-body support device 50, as the length of the extendable member 21 decreases, the force required for pressing the movable body 31 against the tube plate 12 decreases. Accordingly, as the length of the extendable member 21 increases, the counterweight control device 52 increases the protrusion amount of the second member 53b from the first member 53a to increase the distance between the weight 54 and the first coupling portion 21d. With this configuration, in the movable-body support device 50, the counterweight mechanism 51 can preferably decrease a load of the supporting electric motor 24. As the length of the extendable member 21 decreases, the counterweight control device 52 decreases the protrusion amount of the second member 53b from the first member 53a to decrease the distance between the weight 54 and the first coupling portion 21d. Accordingly, the movable-body support device 50 can reduce the possibility that a vertically upward force acts on the movable body 31 more than necessary. (Fourth Embodiment) FIG. 7 is an explanatory diagram of a counterweight mechanism according to a fourth embodiment. A movable-body support device 60 according to the fourth embodiment shown in FIG. 7 is similar to the movable-body support device 50 according to the third embodiment shown in FIG. 6 in that the distance between the weight and the first coupling portion can be adjusted. The movable-body support device 60 includes a counterweight mechanism 61 as the second force application unit, and a counterweight control device 62. The counterweight mechanism 61 includes a weight movement unit and a weight 65. The weight movement unit is configured to include a screw-rotating electric motor 63, an external-thread rotating shaft 64, and a weight-rotation regulating member 66. The screw-rotating electric motor 63 rotates the external-thread rotating shaft 64 on a central axis of the external-thread rotating shaft 64. The weight 65 is a nut-like member, and an internal thread is formed on an inner periphery of a cylinder. The weight 65 is screwed together with the external-thread rotating shaft 64. The weight-rotation regulating member 66 regulates rotation of the weight 65 so that the weight 65 does not rotate together with the external-thread rotating shaft 64 when the external-thread rotating shaft 64 is rotated. In the counterweight mechanism 61, when the external-thread rotating shaft 64 is rotated, the weight 65 moves along the external-thread rotating shaft 64. The counterweight control device 62 is electrically connected to the screw-rotating electric motor 63. The counterweight control device 62 controls operations of the screw-rotating electric motor 63 to adjust a rotation direction and a rotation amount of the external-thread rotating shaft 64. As the length of the extendable member 21 increases, the counterweight control device 62 rotates the external-thread rotating shaft 64 in one direction to increase the distance between the weight 65 and the first coupling portion 21d. With this configuration, in the movable-body support device 60, the counterweight mechanism 61 can decrease a load of the supporting electric motor 24 more preferably. Furthermore, as the length of the extendable member 21 decreases, the counterweight control device 62 rotates the external-thread rotating shaft 64 in a direction opposite to the direction described above, to decrease the distance between the weight 65 and the first coupling portion 21d. Accordingly, the movable-body support device 60 can reduce the possibility that a vertically upward force acts on the movable body 31 more than necessary. (Fifth Embodiment) FIG. 8 is an explanatory diagram of a counterweight mechanism according to a fifth embodiment. A movable-body support device 70 according to the fifth embodiment shown in FIG. 8 has a feature that the mass of a weight is changed. The movable-body support device 70 includes a counterweight mechanism 71 as the second force application unit and a counterweight control device 72. The counterweight mechanism 71 includes a rod-like member 73 for weight, a container 74, and a fluid-amount adjustment unit. The fluid-amount adjustment unit is configured to include a fluid supply path 75, a pump 76, a fluid discharge path 77, a solenoid valve 78, and a tank 79. The rod-like member 73 for weight is connected to the extendable member 21. Specifically, the rod-like member 73 for weight is extended to an opposite side to the second coupling unit 21e while using the first coupling unit 21d as a fulcrum. The container 74 is provided at a portion of the rod-like member 73 for weight that is away from the first coupling unit 21d. One end of the fluid supply path 75 and of the fluid discharge path 77 respectively opens to the container 74, and the other end thereof opens to the tank 79. The pump 76 is provided in the fluid supply path 75 and guides a fluid stored in the tank 79 to the container 74. The solenoid valve 78 is provided in the fluid discharge path 77. The solenoid valve 78 guides a fluid in the container 74 to the tank 79 at the time of being opened, and stores the fluid in the container 74 at the time of being closed. In the movable-body support device 70, the mass of the container 74 containing liquid changes according to the fluid volume of the fluid in the container 74. The counterweight control device 72 is electrically connected to the pump 76 and the solenoid valve 78. The counterweight control device 72 controls operations of the pump 76 to adjust the flow rate of the liquid guided into the container 74. Furthermore, the counterweight control device 72 controls opening and closing of the solenoid valve 78 to adjust the flow rate of the liquid to be discharged from the container 74. In this manner, the counterweight control device 72 adjusts the fluid volume of the liquid in the container 74. The counterweight control device 72 increases the fluid volume of the liquid in the container 74 as the length of the extendable member 21 increases. With this configuration, a vertically upward force acting on the movable body 31 and generated by the counterweight mechanism 71 increases. Therefore, in the movable-body support device 70, the counterweight mechanism 71 can decrease a load of the supporting electric motor 24 more preferably. Furthermore, the counterweight control device 72 decreases the fluid volume of the liquid in the container 74 as the length of the extendable member 21 decreases. With this configuration, the vertically upward force acting on the movable body 31 and generated by the counterweight mechanism 71 decreases. Accordingly, the movable-body support device 70 can reduce the possibility that the vertically upward force acts on the movable body 31 more than necessary. While each of the movable-body support devices according to the third to fifth embodiments adjusts the magnitude of the force F2 generated by the counterweight mechanism, the movable-body support device can adjust the magnitude of the force F2 generated by the supporting electric motor 24. In this case, the movable-body support device includes a supporting electric-motor controller. As the distance between the first coupling unit 21d and the second coupling unit 21e increases, that is, as the length of the extendable member 21 increases, the supporting electric-motor controller increases the magnitude of the force F2 generated by the supporting electric motor 24. Furthermore, as the length of the extendable member 21 decreases, the supporting electric-motor controller decreases the magnitude of the force F2 generated by the supporting electric motor 24. Also in this mode, the movable-body support device can reduce the possibility that the vertically upward force acts on the movable body 31 more than necessary. As described above, the water-chamber working apparatus according to the present invention is useful for a technique of performing a predetermined work in a water chamber of a steam generator, and is particularly suitable for stably supporting a movable body on a tube plate. 1, 2 water-chamber working apparatus 10 steam generator 11 water chamber 12 tube plate 13 hemispherical wall surface 14 heat transfer tube 15 maintenance hatch 20, 50, 60, 70 movable-body support device 21 extendable member 21a first rod-like member 21b second rod-like member 21c third rod-like member 21d first coupling portion (first portion) 21e second coupling portion (second portion) 22 extrusion spring (first force application unit) 23a first universal joint 23b second universal joint 24 supporting electric motor (second force application unit) 25, 51, 61, 71 counterweight mechanism (second force application unit) 25a, 73 rod-like member for weight 25b, 54, 65 weight 30 flaw detector 31, 40 movable body 32 movable-body control device 33, 41 frame 34 wheel 35 running electric motor 36 running-direction-changing electric motor 37 probe support body 38 probe 42 first movable portion 43 second movable portion 44 first thruster 45 second thruster 52, 62, 72 counterweight control device 53 cylinder device (arm-length adjustment unit) 53a first member 53b second member 63 screw-rotating electric motor (weight movement unit) 64 external-thread rotating shaft (weight movement unit) 66 weight-rotation regulating member (weight movement unit) 74 container 75 fluid supply path (fluid-amount adjustment unit) 76 pump (fluid-amount adjustment unit) 77 fluid discharge path (fluid-amount adjustment unit) 78 solenoid valve (fluid-amount adjustment unit) 79 tank (fluid-amount adjustment unit) R1, R3 first rotation axis R2, R4 second rotation axis |
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abstract | A composite material is constituted by fine nano-oxide particles, a dispersant, and a transparent resin material. The dispersant includes a polymer of vinyl monomer having a binding acidic group. When φ is a dimensionless number defined by an average particle size (nm) of the fine nano-oxide particles divided by nm, the polymer has a degree of polymerization of an integer of 3 or more and 8×φ or less with the proviso that the integer is a numerical value obtained by dropping a decimal fraction. The composite material is produced through a step of obtaining a dispersant comprising a polymer by polymerizing a vinyl monomer having a binding acidic group in the presence of polyamine or in an aqueous dilute dispersion, and a step of mixing the dispersant, fine nano-oxide particles, and a transparent resin material. |
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claims | 1. A moderator temperature coefficient measurement apparatus, comprising:an input unit having at least one storage device, the input unit receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor; anda data processing unit programmed to decompose the coolant temperature signal into N time-dependent temperature components and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method,wherein the data processing unit is programmed to generate at least one selected combination by selecting a temperature component from the N time-dependent temperature components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component, andwherein the data processing unit is programmed to calculate a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the data processing unit is programmed to extract combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components, andwherein the at least one selected combination is selected from the combinations extracted by the data processing unit. 2. The moderator temperature coefficient measurement apparatus according to claim 1,wherein the data processing unit is programmed to generate temperature coefficient plot data for respective frequencies with use of auto and cross power spectral density functions obtained by applying a Fourier transformation to each of the at least one selected combination,wherein the temperature coefficient plot data includes a pair of a coherence and a moderator temperature coefficient, and calculate a moderator temperature coefficient at a coherence of 1 by extrapolating the temperature coefficient plot data. 3. The moderator temperature coefficient measurement apparatus according to claim 2, wherein the input unit receives a plurality of plant data different from each other, each of the plurality of plant data corresponds to the plant data, andwherein the data processing unit is programmedto calculate moderator temperature coefficients for the plurality of plant data, respectively, to count a number of high coherence data corresponding to the number of the temperature coefficient plot data for which the coherence is larger than a predetermined criterion andto output a reliable moderator temperature coefficient for which a number of the high coherence data is judged to be large based on a predetermined criterion, the outputted moderator temperature coefficient being selected from among the moderator temperature coefficients respectively corresponding to the plurality of plant data. 4. A void reactivity coefficient measurement apparatus, comprising:an input unit having at least one storage device, receiving plant data including a void fraction signal being time series data on a void fraction of a boiling water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the boiling water reactor; anda data processing unit programmed to decompose the void fraction signal into N time-dependent void fraction components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method,wherein the data processing unit is programmed to generate at least one selected combination by selecting a void fraction component from the N time-dependent void fraction components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected void fraction component and the selected reactivity component; andwherein the data processing unit is programmed-to calculate a void reactivity coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the data processing unit is programmed to extract combinations each of which has a strong correlation between the void fraction signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent void fraction components and the M time-dependent reactivity components, andwherein the at least one selected combination is selected from the combinations extracted by the data processing unit. 5. A moderator temperature coefficient measurement method implemented on a moderator temperature coefficient apparatus including an input unit and a data processing unit, the method comprising:by the input unit, receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor;by the data processing unit, decomposing the coolant temperature signal into N time-dependent temperature components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method;by the data processing unit, generating at least one selected combination by selecting a temperature component from the N time-dependent temperature components-and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component; andby the data processing unit, calculating a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the generating at least one selected combination includes:extracting combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components; andselecting the at least one selected combination from the extracted combinations. 6. A computer program product embodied on a computer-readable medium and comprising code that, when executed, causes a computer to perform the following: receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor;decomposing the coolant temperature signal into N time-dependent temperature components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method;generating at least one selected combination by selecting a temperature component from the N time-dependent temperature components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component; andcalculating a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the generating at least one selected combination includes:extracting combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components; andselecting the at least one selected combination from the extracted combinations. |
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048184713 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fuel assemblies for a nuclear reactor and, more particularly, is concerned with a boiling water reactor (BWR) fuel assembly having localized neutron absorber strips placed on its outer tubular channel for facilitating calibration of Local Power Range Monitor (LPRM) neutron flux detectors. 2. Description of the Prior Art Typically, large amounts of energy are released through nuclear fission in a nuclear reactor with the energy being dissipated as heat in the elongated fuel elements or rods of the reactor. The heat is commonly removed by passing a coolant in heat exchange relation to the fuel rods so that the heat can be extracted from the coolant to perform useful work. In nuclear reactors generally, a plurality of the fuel rods are grouped together to form a fuel assembly. A number of such fuel assemblies are typically arranged in a matrix to form a nuclear reactor core capable of a self-sustained, nuclear fission reaction. The core is submersed in a flowing liquid, such as light water, that serves as the coolant for removing heat from the fuel rods and as a neutron moderator. Specifically, in a BWR the fuel assemblies are typically grouped in clusters of four with one control rod associated with each four assemblies. The control rod is insertable between the fuel assemblies for controlling the reactivity of the core. Each such cluster of four fuel assemblies surrounding a control rod is commonly referred to as a fuel cell of the reactor core. A typical BWR fuel assembly in the cluster is ordinarily formed by a N by N array of the elongated fuel rods. The bundle of fuel rods are supported in laterally spaced-apart relation and encircled by an outer tubular channel having a generally rectangular cross-section. Examples of such fuel assemblies are illustrated and described in U.S. Pat. Nos. (3,349,004) to Lass et al, (3,689,358) Smith et al, (3,802,995) Fritz et al, (4,560,532) Barry et al and (4,649,021) Taleyarkhan and in a Canadian Pat. No. (1,150,423) to Anderson et al. A BWR core typically includes several LPRM strings dispersed throughout the core. These strings are located inbetween the corner locations of four fuel assemblies. Each string includes a hollow tube with four neutron detectors located at discrete axial locations. During reactor operation these detectors provide crucial local power monitoring information. However, the detectors need to be calibrated at specific time intervals with a movable tip probe that is inserted from the bottom of the core, into selected detector string tubes. This calibration is necessary for maintaining the accuracy/fidelity of the LPRM readings on the control console. In a BWR core made up of General Electric (GE-8.times.8) fuel assemblies as the tip probe is inserted in the string tube, its relative position is evaluated from the location of neutron flux dips caused by Inconel fuel rod spacers located axially along the fuel assembly. The Inconel spacers, usually seven in number, act as neutron absorbers and hence such dips occur. In reload situations where Westinghouse Electric (W-QUAD+) BWR fuel assemblies are used to replace selected General Electric BWR fuel assemblies, it is highly likely that Westinghouse fuel assemblies will end up replacing GE fuel assemblies at one of the LPRM string locations. The Westinghouse fuel assembly, designed for optimized fuel cycle cost benefits, employs an all-Zircaloy spacer design. However, these Westinghouse Zircaloy spacers will not produce local neutron flux dips like the GE Inconel spacers. Furthermore, the six Zircaloy spacers in the adjacent fuel rod subassembly of the Westinghouse fuel assembly are located at axial positions different from the axial positions of the seven Inconel spacers in the GE fuel assembly. Hence, proper positioning of the tip probe for calibration purposes becomes impossible with current plant setup. Such a situation could lead to NRC-imposed uncertainty penalties in the form of plant derates. Consequently, a need exists for an effective means of providing an indicator for locating the LPRM detectors in plants where GE BWR fuel assemblies are replaced with Westinghouse BWR fuel assemblies. SUMMARY OF THE INVENTION The present invention provides an improvement which is designed to satisfy the aforementioned needs. The technique underlying the present invention relates to providing an improvement in the form of a plurality of local neutron absorber strips, for instance made of a material containing boron, hafnium and/or silver, at axial locations on the exterior of the outer channel of the Westinghouse BWR fuel assembly which correspond to the axial positions of the Inconel spacers of the GE BWR fuel assembly. This ensures compatibility of the Westinghouse BWR fuel assembly design with the existing GE fuel assembly design in a reload core. The above technique provides effective positioning of the tip probes for calibration purposes and eliminates uncertainty-related penalties for the Westinghouse BWR fuel assembly design in reload BWR cores. An additional benefit attributed to the above technique is the assurance of proper fuel assembly orientation. That is, the corner where absorber strips are attached can be used for assuring proper orientation of the Westinghouse BWR fuel assembly in a reload BWR core. The relatively small amount of neutron absorber strips used is estimated to cause a negligible impact on nuclear fuel cycle cost. Further, structural, thermal-hydraulic and LOCA performance areas would also remain unaffected. Accordingly, the present invention is set forth in the combination of at least one Local Power Range Monitor (LPRM) string and a plurality of fuel assemblies arranged in side-by-side spaced positions about the string. The LPRM string has a hollow tube and a plurality of neutron detectors located therein at spaced axial locations and being adapted to provide local power monitoring information. The hollow tube of the string is adapted to receive a neutron flux sensitive probe for calibrating the detectors. Each of the fuel assemblies has a plurality of spaced fuel rods, an outer hollow tubular channel surrounding the fuel rods and a plurality of spacers disposed within and axially along the channel and about the fuel rods so as to maintain them in side-by-side spaced relationship. The spacers of at least one of the fuel assemblies is composed of a material incapable of producing a localized change in neutron flux. The feature of the present invention is an improvement comprising a plurality of elements attached to the at least one fuel assembly and located axially at different known positions therealong and adjacent to the hollow tube of the string. Each of the elements is composed of a material capable of producing a localized change in neutron flux such that, upon passage of the probe through the hollow tube of the string and past the elements, the probe will sense the neutron flux change being produced by each of the elements and thereby the position of the probe can be tracked as it is moved through the string tube. More particularly, the elements are attached to the exterior of the at least one fuel assembly channel at the different known positions therealong. Preferably, each element is in the form of a strip of the material. Further, the fuel assembly channel is rectangular in cross-section and has a corner located adjacent to the string tube. Each of the plurality of elements is attached about the corner of the fuel assembly channel. These and other advantages and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings . |
description | The present invention relates to a container for storing nuclear waste, more particularly spent nuclear fuel. Within the scope of irradiated fuel management, after it is used in a reactor the latter undergoes a cooling step in a pool in a building known as a fuel building, generally located next to the reactor building. On completion of this cooling step, the irradiated fuel is removed from the pool, and then evacuated to a storage location to wait for definitive discharge which can be either reprocessing or geologic stockpiling. The cooling step in the pool has limited duration due to the reduced capacity of cooling ponds. In this context, it is planned to condition the irradiated fuel in containers forming the first confinement barrier, each container in turn being arranged in a container forming a second confinement barrier and ensuring the mechanical performance of the assembly. This container is intended for transport of the container to its provisional storage location. Next, the container is removed from the container stored in an adapted structure. The container comprises a cylindrical body of circular cross-section, a base welded at one end of the body. After the fuel is placed in the container, a plug is welded onto the free end of the body, this plug ensuring tight closing of the container and also forming gripping means for moving the container. The welding of the plug on the body is done by adding wire. Also, a relatively complex welding device needs to be used since it has to assume a particular orientation to ensure that a weld is made between the periphery of the plug and the body of the container. Also, the weld must be sufficient to lift the container loaded by the plug. It is consequently an aim of the present invention to provide a container designed to contain spent fuel, having improved closing. The above aim is attained by a container comprising a cylindrical body of circular cross-section, a base sealing a first longitudinal end of said body and a cover designed to block a second longitudinal end of said body, said second longitudinal end comprising a flange projecting from the inner surface of the body and bordering the second end and designed to form a support for the cover, the cover being designed to be welded on the flange. Thanks to the invention, immobilisation of the plug on the body is not achieved by direct welding of the plug on the body, but of the plug on the flange, the welding zone is offset radially towards the axis of the body, the welding device no longer needing to have a complex orientation, since the welding zone is easily accessible. In other terms, the invention provides for radially offsetting the welding zone of the plug towards the interior of the container so as to make this zone more accessible to welding means, improving the making of the weld and simplifying the welding means. It is provided advantageously that the inner surface of the flange comprises a form of step corresponding to a peripheral external profile of the plug. Thus, the plug rests on the flange, and adding material for the weld is not required. Advantageously, a second plug mainly forming handling means of the container can be used, the first plug forming the sealed barrier. For this, the first plug is arranged set back inside the body, relative to the open end of the body, the second plug being attached to the body to cover the first plug. The subject-matter of the present invention is mainly a container for confining spent nuclear fuel, comprising a sleeve of longitudinal axis closed at a first longitudinal end by a base and a second longitudinal free end via which the container is designed to be loaded, a plug designed to close the second longitudinal free end tightly by means of a weld made at the level of a welding zone, said welding zone being offset radially towards the interior of the container, relative to the inner face of the sleeve, said container comprising a flange projecting from the inner face of the sleeve to the side of the second longitudinal free end, the plug having at least one external diameter substantially equal to at least one internal diameter of the flange, said plug being designed to be welded on said flange. The flange is advantageously welded on the inner face of the sleeve. Radial offset can be obtained by means of a flange fixed on the inner face of the sleeve to the side of the second longitudinal free end, the plug having at least one external diameter substantially equal to at least one internal diameter of the flange, said plug being designed to be welded on said flange. The flange advantageously comprises a first section of larger internal diameter and a second section of smaller internal diameter connected by an annular surface forming a shoulder substantially orthogonal to the longitudinal axis, the plug comprising an external profile corresponding to the internal profile of the flange, such that the plug rests on the shoulder. It can be provided advantageously that the container comprises handling means of the container distinct from the plug, said means being fixed to the sleeve at the level of the longitudinal free end of the sleeve, the flange being fixed in the sleeve set back from the longitudinal free end of the sleeve. The handling means are for example formed by a cover fitted in its centre with a gripping element. The cover can advantageously comprise a rim of thickness close to the thickness of the longitudinal free end of the sleeve so as to enable welding of the cover on the sleeve without adding wire. Advantageously, the container according to the invention can comprise loading wedging means, said wedging means being connected inside the container. In the case where the container is circular in cross-section, the wedging means can be formed by a casing whereof the length is substantially equal to the internal length of the container and whereof the transversal cross-section is a square, the length of the diagonals of said square being substantially equal to the internal diameter of the container. The casing can also comprise means for evacuating the heat emitted by loading. The evacuation means of the heat comprise for example fins extending longitudinally at least on part of the outer faces of the casing in the direction of the largest dimension. The plug comprises advantageously a first and a second connector for the draining of the container, sweeping with air from the interior of the latter and its pressurising. A discharge pipe arranged inside the container can be provided, said pipe comprising a first free end arranged in the base of the container and a second end connected to one of the connectors for suctioning water contained in the container. Another subject-matter of the present invention is a process for loading and closing a container according to the present invention, comprising the steps of: placing the loading inside the container, placing the plug in the flange, welding the plug on the flange without adding material. The process of loading and closing can also comprise the subsequent step of placing gripping means on the free end of the sleeve and welding the latter on the sleeve. FIG. 1 shows an embodiment of a container according to the present invention comprising a cylindrical sleeve 2 of circular cross-section of axis X, made for example of stainless steel. The sleeve 2 comprises first 4 and second 6 longitudinal ends. The first end 4 of the sleeve 2 is closed by a plate 8 forming the base of the container. This plate 8 is fixed on the sleeve 2 for example by welding. The plate 8 and the sleeve 2 can also be made in a single piece, for example by flowturning. The second longitudinal end 6 forms the loading end of the container and is designed to be tightly closed by a plug 10, the plug 10 being put in place when the container is loaded. According to the present invention, an intercalary flange 12 is provided at the level of the second end 6 of the sleeve 2 on which the plug 10 is fixed. The intercalary flange 12 is in the form of a ring fixed on the inner face of the sleeve 2 at the level of the second longitudinal end 6. The flange 12 is more particularly visible in FIGS. 2A and 2B. The flange 12 is welded to the inner face of the sleeve 2. Advantageously, the flange 12 comprises an internal profile 14 in the form of a step formed by a first portion of larger internal diameter and a second portion of smaller internal diameter, said portions being connected by an annular surface 16 orthogonal to the axis X, oriented towards the exterior of the container and designed to former a support for the plug. The outer periphery of the plug 10 comprises an external profile corresponding to that of the flange 12. The outer periphery therefore comprises a first portion of larger external diameter and a second portion of smaller external diameter connected by an annular surface 18 forming a shoulder designed to rest on the annular surface 16. The diameter of the portion of larger external diameter of the plug is substantially equal to that of the portion of larger internal diameter of the flange, and the diameter of the portion of smaller external diameter of the plug is substantially equal to that of the portion of smaller internal diameter of the flange. According to the present invention, during closing of the container, the plug 10 is welded on the flange 12 at the level of the contact between the external contours of the portions of larger internal and external diameter of the flange 12 and of the plug 10 respectively. Thanks to the present invention, the welding means 23 to be used (shown in dotted lines in FIG. 2B) are simpler. In fact, they do not need to assume complex orientations to attain the welding zone. Also, the weld can be made without adding extra material, simplifying the welding process and the device designed for welding. The weld is formed by fusion of the materials making up the contours of the flange 12 and of the plug 10. It should be noted that the flange is welded on the sleeve prior to loading of the fuel; consequently its welding on the sleeve is much simpler. The plug 10 forms a tight barrier and confines the spent fuel in the volume V delimited by the sleeve 2, the base and the plug. For safety reasons the container with the spent fuel can be loaded under water in a pool, the plug being welded on the flange 12 under water. This loading process involves the volume V being filled with water to be discharged, therefore this volume and the fuel it contains must also be dried. As is evident in FIG. 2A, a tube 21 designed to discharge water can be placed in the container, this tube comprising a first suction end terminating in the base of the container and a second discharge end terminating towards the plug 10, this end being designed to be connected to a first discharge connector 22 carried by the plug, the connector being attached to a connector 24 passing through the plug 10. This connector can also help to dry out the container. The plug 10 also comprises a second connector 26 for discharge of air during drying of the container and pressurisation of the container, if required. Finally, when the different steps for closing the container are completed, these first 22, 24 and second 26 connectors measure the humidity inside the container, which verifies the performance of the container over time. In a particularly advantageous manner and as shown in FIGS. 1 and 2B, the container comprises means 28 for handling the container without handling the plug 10. The means 28 form a cover fixed on the sleeve, by welding directly onto the latter, this cover covering the plug 10. For this, the plug 10 is fixed in the sleeve 2 set sufficiently back from the free end of the sleeve 2, this longitudinal free end receiving the cover 28. The main function of the cover 28 is not to seal the container, but to enable handling of the container, for example by a device suspended from an overhead crane. For this, the cover 28 comprises a gripping system 30 projecting towards the exterior. In the example illustrated, this gripping system 30 is a piece projecting at the centre of the cover. The gripping system could also be made in the form of a recess. In this advantageous example, the sealing and handling functions are distinct. Consequently, tight fixing of the plug 1 on the sleeve via the flange 12 does not need to offer major mechanical resistance to traction, and mechanical fixing of the cover 28 on the sleeve 2 is provided to deal with traction forces during lifting of the container and is not designed to be tight. This separation of functions simplifies the making and monitoring the container. It is understood that to further improve the level of safety of the confinement offered by the container, the fixing of the cover 28 on the sleeve 2 could be sealed. It should be noted that since the cover is fixed at the longitudinal free end of the sleeve, its fixing by welding to the sleeve does not encounter the same difficulties as for fixing the plug 10 on the sleeve. But to simplify the overall process, the cover can be attached to the sleeve identically to that used for the plug by welding without wire. For this, and as it can be seen in FIG. 2C, the radially external periphery of the cover is formed by a ring 28.1 of thickness substantially equal to that of the end of the sleeve, which allows the making of a wireless welding. The cover 28 also comprises an annular shoulder 28.2 resting on an annular support surface 29 arranged in the inner face of the sleeve. Due to this cover design, the welding process of the plug on the flange and the welding process of the cover on the sleeve are identical and need no change in equipment, as the whole process is faster. As a variant, the flange is made in a single piece with the sleeve, avoiding a welding step. As shown in FIGS. 3A and 3B, the container also comprises particularly advantageously means 32 for keeping the loading arranged in the container substantially at the centre of the latter. These wedging means 32 are formed in the example shown by a casing 33 of square cross-section whereof the dimension of the diagonals is substantially equal to the internal diameter of the container, ensuring immobilisation of the casing 33 in the container. The spent fuel is arranged inside the casing 33 which holds it laterally. The casing has a length substantially equal to that of the internal volume of the container. In a particularly advantageous manner, the casing 33 comprises, projecting from its outer faces, cooling fins 34 facilitating evacuation of heat released by the fuel to the exterior of the container. In FIG. 3A, the fins 34 extend over the entire length of the casing 33. In FIG. 3B, showing a variant of the wedging means, the casing 33 is equipped at each of its longitudinal ends with four fins 34′ of reduced size, extending only over a limited part of the length of the casing 33. This casing 33 is for example formed by four sheets 33a to 33b. A number of fins 34 could also be distributed over the entire length of the casing 33. FIG. 4 shows the casing 33 in the container. It is understood that the casing can have different cross-section, for example an octagonal cross-section. These wedging means are advantageously removable. They are put in place as needed, especially as a function of the shape of the containers. The loading and closing steps of the container according to the present invention will now be described. The container according to the present invention is loaded with spent nuclear fuel. The plug 10 is then put in place in the flange 12. Welding means (shown in dotted lines in FIG. 2B) are then brought close to the plug and the flange and weld the plug and the flange. Due to the invention, the welding means can be brought substantially parallel to the longitudinal axis X of the container, since the welding zone is easily accessible. In the case where a handling cover 28 is provided, the latter is brought to the longitudinal free end of the container and the latter is welded, for example by the same means. The container is then ready for handling. Due to the invention, a container is made which can be tightly closed. It is understood that a container whereof the plug also serves as gripping means does not depart from the scope of the present invention. |
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051679124 | summary | FIELD OF THE INVENTION The instant invention relates generally to the field of neutron reflective/scattering devices adapted to collect neutrons from a neutron source, such as a nuclear reactor core, and guide said neutrons to remote locations for use in, inter alia, testing and research facilities. The instant invention is more particularly related to the field of improved, neutron reflecting, multilayered supermirror structures characterized by average neutron reflectivities of greater than 97% at incident angles of at least two times the critical angle of standard neutron reflectors, such as nickel. BACKGROUND OF THE INVENTION Neutron scattering experimentation has been conducted both in the United States and throughout the world since the early 1950's. The fundamental breakthroughs in neutron research are the result of the expenditure of hundreds of millions of dollars in the development and construction of research and analytical facilities. Neutron research has found its greatest utility in applications such as elemental analysis, determination of atomic arrangement, the magnitude and direction of atomic magnetic moments, and the examination of macroscopic bodies for structural flaws. In fact, neutron experimentation/analysis is often the only source of essential analytical information, which is otherwise unattainable by other spectroscopic or diffraction techniques. Neutron research is also critical to the development of advanced synthetic materials for use in a host of "next generation" products and applications. The basic principles of neutron reflection are reported on in a paper by G. P. Felcher entitled "Principles of Neutron Reflection" SPIE Vol 983, Thin-Film Neutron Optical Devices (1988). Several laboratories (including many of the United States national labs) have proposed improving the quality and quantity of neutron experimentation by channelling neutrons to remotely located experimental stations via neutron reflecting guidetubes. The advantages of this approach have been demonstrated by research facilities in Europe and Japan. Heretofore, the only method for collecting and transporting neutrons (particularly those neutrons having the most utility, and characterized by wavelengths of greater than about 0.4 nm, also known as "cold neutrons") was to employ guidetubes having 100 nm thick nickel plated glass plates disposed therein. Nickel has, until recently, been a preferred reflective element for use in neutron guidetubes due to the fact that nickel has the maximum reflection angle of any single element. In fact, nickel's maximum reflection angle is approximately equal to the critical reflection angle for a neutron wavelength of 0.4 nm (i.e. approximately 0.4 degrees theta). This critical angle is important since it defines the angular acceptance of the guidetube, and since the neutron flux from a guidetube is typically measured in "counts per minute" (as opposed to x-ray fluxes in excess of 1000 counts per second) enhanced guidetube acceptance is highly desirable. Recently, much interest has been shown to the area of multilayered neutron reflecting supermirrors for improving neutron acceptance and throughput beyond that of pure Ni films. These supermirrors typically take the form of layered films of titanium and nickel having a distribution of bilayer thicknesses designed to yield overlapping Bragg diffraction peaks to occur from the region just above the cutoff angle characteristic of Ni to some increased angle of acceptance. It is also important that reflectivity of the supermirror remains high as the reflection angle is extended, otherwise the cumulative reduction from each reflection along the guidetube would result in an unacceptable loss of neutron flux. Heretofore, titanium and nickel have been the preferred choices for non-polarizing supermirrors owing to their high characteristic effective neutron scattering. Experimental Ni-Ti supermirror guidetubes have found limited use in Japan and Europe as was demonstrated by Ebisawa, et al in a publication entitled "Nickel Mirror and Supermirror Neutron Guides at the Kyoto University Research Reactor" SPIE Proc., v. 983, pp 54-58, (1988); and Schoupf, "Recent Advances with Supermirror Polarizers," AIP Proc., No. 89, pp 182-189 (1982). Other progress has been reported in a publication by Rossback, et al entitled "The Use of Focusing Supermirror Neutron Guides to Enhance Cold Neutron Fluence Rates" Nuclear Instruments and Methods in Physics Research B 35 (1988) 181-190. Rossbach, et al report improved neutron reflecting characteristics in carefully deposited Ti-Ni supermirror structures on certain glass substrates having a measured roughness of 18.5 angstroms. These supermirror structures have been used in neutron reflecting applications requiring reflectivity lower than standard guidetubes: hence reflectivity is approximately 65%. Rossback, et al indicates that layer imperfections resulting from crystal growth are the primary reason for less than optimum reflectivity. While Ti-Ni supermirrors have to date proven effective for use in neutron reflecting applications, routineers skilled in the supermirror art have reported observing distortions in the layer structure. The result is a loss (often serious) in the reflectivity of the supermirror, and hence a significant increase in the effective cost of neutron experimentation. It is believed that the layer distortions are the result of, inter alia, crystal growth in the layers, materials interactions, film stresses of the layered structures and/or interdiffusion of Ti and Ni at the layer interfaces which prevent the attainment of the high degrees of layer flatness required in order to achieve the desired high reflectivity. In fact, the instant inventors have found that a lack of layer flatness is the primary cause for reduction in reflectivity. Attempts to enhance supermirror performance so as to achieve neutron reflection of greater than three times the critical angle of nickel alone have been reported in a number of publications. Prior to the invention of the novel supermirror structures described hereinbelow, no supermirrors have achieved the performance levels needed for practical neutron guidetube applications. Numerous reasons for the poor performance of supermirrors have been advanced, as in, for example, a publication by Keem, et al entitled "Neutron, X-Ray Scattering and TEM Studies of Ni-Ti Multilayers" published in SPIE Vol. 983 Thin-Film Neutron Optical Devices (1988) which identifies cusp formation in the Ni-Ti bilayers as the principle factor preventing supermirror performance at acceptable levels. Progress has, however, been reported in the development and fabrication of polarizing (i.e. supermirrors which more effectively reflect one polarization of neutron spin) supermirrors. Mook and Hayter report in "Transmission Optical Device to Produce Intense Polarized Neutron Beams" Appl. Phys. Lett. 53 (8), 22 Aug. 1988, p. 648 a highly effective polarizing neutron mirror making use of a crystalline silicon layer for polarizing reflected neutrons. However, improvements in the field of polarizing neutron mirrors are only marginally applicable in the fabrication of non-polarizing supermirrors. Accordingly, there exists a need for an improved neutron reflecting supermirror structure characterized by neutron reflectivities in excess of 97% and a critical angle of at least two times the critical angle of standard neutron reflectors such as nickel or Ti-Ni alloys. These improved supermirror structures will, of course, have to overcome the reflectivity problems resulting from a number of technical problems, including but not limited to, lack of layer flatness caused by, for example, crystal growth. THE BRIEF SUMMARY OF THE INVENTION There is disclosed herein an improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of high and low neutron scattering materials. The high and low neutron scattering materials are deposited upon a substrate, wherein one layer of each of said sets of bilayers consists of titanium and the second layer of each of said sets of bilayers consists of an alloy including nickel and a microstructural enhancing element. The microstructure enhancing element may have a high neutron scattering potential, and be adapted to enhance the microstructure by reducing the crystal grain size of the nickel layer. In a first preferred embodiment of the instant invention the microstructure enhancing element is carbon and is present interstitially in the nickel alloy layer so as to modify the nickel crystal grain size. While not wishing to be bound by theory, it is believed that the microstructure enhancing element reduces the nickel crystal grain size, hence reducing layer stresses and promoting layer flatness. The percentage of carbon present in the nickel alloy layer is preferably between five and fifty percent and more preferably between twelve and thirty-five percent. In one embodiment of the instant invention, the nickel alloy layer has a nominal composition of Ni.sub.72 C.sub.28 and in a second embodiment of the instant invention the nickel alloy layer has a nominal composition of Ni.sub.86 C.sub.14. It is important to note, however, that the instant invention contemplates nickel alloy layers having nominal compositions of between Ni.sub.95 C.sub.5 and Ni.sub.50 C.sub.50. The improved neutron reflecting supermirror structure described herein is typically deposited upon a substrate selected from group consisting of float glass, pyrex glass and silicon. As indicated hereinabove the improved neutron reflecting supermirror structure comprises a plurality of stacked sets of bilayers, the number of said bilayers being preferably between two and one thousand and most preferably between twenty and five hundred sets of stacked bilayers. It is to be noted that the thickness of each set of bilayers may be altered so that a layer or layers will be adapted to change the characteristic acceptance/reflection of the neutrons incident thereupon. Indeed, as will be discussed in greater detail hereinbelow, the thickness of each set of bilayers is graded in a continuous fashion to achieve the optimum in reflectivity and angular range. The layer thickness of each set of bilayers is between approximately two and four hundred nm and most preferably between eight and forty nm. The improved neutron reflecting supermirror structure may further include a layer of nickel deposited either directly upon the substrate and immediately subjacent the first set of bilayers or atop the last or uppermost set of bilayers. Alternatively, the nickel may be substituted with a nickel alloy or carbon. |
abstract | A modulator for use in a radiation system with directional radiation beams respectively collimated into radiation fields, including a plurality of displaceable radiation attenuating elements arranged in at least one row, the radiation attenuating elements being configured to attenuate portions of a radiation beam inside the radiation field according the position of the radiation attenuating elements, and wherein each radiation attenuating element is respectively attached to a substantially radiolucent member, and a driver operable to store motion profiles and to respectively drive the radiation attenuating elements in directions generally perpendicular to the radiation beam via the substantially radiolucent members, wherein the respective motions of the radiation attenuating elements are according to corresponding motion profiles, and wherein a motion profile relates position and/or velocity of the radiation attenuating elements to time and/or irradiation level. |
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claims | 1. A radiotherapy apparatus, comprising:a radiation source configured to radiate a radiation ray;a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray; anda drive unit configured to move at least one of the leaves with an ultrasonic wave. 2. The radiotherapy apparatus according to claim 1, wherein the drive unit comprises:a metal material contacting a contact edge of the leaf in a contact pressure;a piezoelectric transducer which is placed on an opposite side to the contact edge of the metal material; anda signal generation unit configured to supply an electric signal to the piezoelectric transducer. 3. The radiotherapy apparatus according to claim 2, wherein the signal generation unit comprises:a first drive circuit which is provided to each leaf of a first band of leaves among the plurality of leaves; anda second drive circuit which is provided to each leaf of a second band of leaves among the plurality of leaves. 4. The radiotherapy apparatus according to claim 3, further comprising:a switch circuit, connected to the second drive unit, configured to select at least one leaf to be moved by the second drive unit among the second band of leaves. 5. The radiotherapy apparatus according to claim 4, wherein:the first band of leaves are positioned on an inner side to an isocentre; andthe second band of leaves are positioned on an outer side to the isocentre than the first band of leaves. 6. The radiotherapy apparatus according to claim 2, wherein the piezoelectric transducer is placed on a side edge of the leaf. 7. The radiotherapy apparatus according to claim 2,wherein the piezoelectric transducer and the metal material are placed on farther positions from an isocentre than a maximum radiation range. 8. A radiotherapy apparatus, comprising:a radiation source configured to radiate a radiation ray;a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray; andmeans for moving at least one of the leaves with an ultrasonic wave. 9. The radiotherapy apparatus according to claim 8, wherein the means for moving comprises:a metal material contacting a contact edge of the leaf in a contact pressure;a piezoelectric transducer which is placed on an opposite side to the contact edge of the metal material; anda signal generation unit configured to supply an electric signal to the piezoelectric transducer. 10. The radiotherapy apparatus according to claim 9, wherein the signal generation unit comprises:a first drive circuit which is provided to each leaf of a first band of leaves among the plurality of leaves; anda second drive circuit which is provided to each leaf of a second band of leaves among the plurality of leaves. 11. The radiotherapy apparatus according to claim 10, further comprising:a switch circuit, connected to the second drive unit, configured to select at least one leaf to be moved by the second drive unit among the second band of leaves. 12. The radiotherapy apparatus according to claim 11, wherein:the first band of leaves are positioned on an inner side to an isocentre; andthe second band of leaves are positioned on an outer side to the isocentre than the first band of leaves. 13. The radiotherapy apparatus according to claim 9, wherein the piezoelectric transducer is placed on a side edge of the leaf. 14. The radiotherapy apparatus according to claim 9,wherein the piezoelectric transducer and the metal material are placed on farther positions from an isocentre than a maximum radiation range. 15. A method for controlling a radiotherapy apparatus, comprising:radiating a radiation ray;limiting a radiation range of the radiation ray with a plurality of leaves; andmoving at least one of the leaves with an ultrasonic wave. |
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abstract | A system of Structural Members that interconnect or attach to each other to create an Outer Structural Shell to strengthen and protect against failure of Reactor Containment/Shield Buildings and other concrete structures or supports such as pillars, columns and piers. When interconnected, the Structural Members are tensioned to create a protective Outer Structural Shell to contain and restrict degraded or cracked concrete from further cracking and eventual delamination, by applying a supportive compression force to outer concrete wall(s) and surfaces. |
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039322122 | claims | 1. Method for depressurizing, degassing and affording decay of weakly radioactive condensates in a steam nuclear power plant of the type having a turbine with higher and lower pressure stages and a main condenser for condensing exhaust steam from the turbine to a main condensate, and at least one feed-water preheater heatable by bleeder steam fed thereto from a higher pressure stage of the turbine, the condensate of said bleeder steam constituting a secondary condensate, which comprises the steps of: feeding the secondary condensaate at a higher temperature and higher pressure than the main condensate into the main condensate so that the secondary condensate vaporizes in the main condensate with simultaneous degassing of the main condensate by the vaporizing of the secondary condensate, and thereafter passing both main and secondary condensates through a flow path of sufficient length to permit the radioactivity to decay. 2. The method of claim 1 including the step of first feeding the secondary condensate to a pressure relief chamber while still maintaining said secondary condensate at a higher pressure than said main condensate. 3. Method according to claim 2 which includes conducting the feed-water through a flow path that bypasses the preheater, heating the bypassing feed-water by means of bleeder steam from a higher pressure stage of the turbine thereby to produce additional secondary condensate, feeding the additional secondary condensate to another pressure relief chamber and feeding the additional secondary condensate from the other standpipe into the main condensate wherein the additional secondary condensate vaporizes. 4. Apparatus for depressurizing, degassing and affording decay of weakly radioactive condensates in a steam nuclear power plant of the type having a turbine, a main condenser for condensing exhaust steam from the turbine to a main condensate, a tank for collecting the main condensate below the level of the turbine, and at least one feed water preheater heatable by bleeder steam fed thereto from a higher pressure stage of the turbine, the condensate of said bleeder steam constituting a secondary condensate that is at higher temperature and higher pressure than the main condensate because of the origin thereof from said higher pressure stage of the turbine, comprising: a plurality of degassing channels each provided with a lateral overflow, said channels being provided in the upper part of the collecting tank for filling with the main condensate up to the level of the overflows, horizontal feed pipes arranged in said channels below the overflows, at least one pressure relieving standpipe for receiving said secondary condensate, said horizontal feed pipes communicating with said standpipe and having openings at a lower portion thereof, said collecting tank having a lower part provided with partitions having cutouts which are staggered relative to one another thereby to provide a flow path of sufficient length to permit the radioactivity of the condensates to decay, and a run-off sheet communicating between the upper and said lower part of said collecting tank. 5. Apparatus according to claim 4, comprising air cooler units for the main condensate which cause the main condensate to become oxygen-enriched, run-off baffles arranged to conduct the oxygen-enriched main condensate to certain ones of said degassing channels, means for conducting the remaining main condensate to other ones of said degassing channels, whereby a mixing of the oxygen-enriched main condensate and the remaining main condensate takes place on the run-off sheet. 6. Means for the depressurizing, degassing and decay of weakly radioactive condensates in nuclear power plants of the type having a turbine, and a main condenser for the exhaust steam of the turbine whereby the exhaust steam condensed in the main condenser forms a main condensate and a collecting tank for the condensate is situated below the condenser and a source of secondary condensate: comprising a plurality of horizontal degassing channels which have a lateral overflow arranged in the upper part of said condensate collecting tank and adapted to be filled with the main condensate up to the level of the overflow, horizontal feed pipes extending in said channels below the overflow height of the degassing channels, said feed pipes being provided on their underside, with discharge openings for the bubbling of the secondary condensate into the main condensate. 7. Apparatus as in claim 6 wherein said condensate collecting tank has partitions which are provided with mutually displaced partitions in order to provide an adequately long path for the decay of the main and secondary condensates, the condensate which is discharged from the condensate collecting tank being returnable into the cycle as feed-water. |
claims | 1. A reactor power output measurement device measuring a neutron flux with a traversing incore probe (TIP) traversing in a vertical direction in a core of a reactor, and calibrating a detection sensitivity of a local power range monitor based on a measured neutron flux distribution in the axial direction inside said reactor, said device comprising: a detector drive system for said TIP; a drive control unit including a drive control device and a drive unit operation/monitor means for operating and monitoring the drive control device for controlling said detector drive system; and a TIP integrated control unit connected to said drive control device and including an integrated unit operation/monitor means for operating and monitoring said drive control device; wherein operation is switched to said integrated unit operation/monitoring means when said drive unit operation/monitor means suffers a failure. 2. A reactor power output measurement device according to claim 1 , wherein an operation command is output from said integrated unit operation/monitor means to said drive control device in response to an operation authorization signal output from said detector drive system of said TIP. claim 1 3. A reactor power output measurement device measuring a neutron flux with a traversing incore probe (TIP) traversing in a vertical direction in a core of a reactor, and calibrating a detection sensitivity of a local power range monitor based on a measured neutron flux distribution in the axial direction inside said reactor, said device comprising: a detector drive system for said TIP; a drive control unit including a drive control device for controlling said detector drive system, and a drive unit operation/monitor means for operating and monitoring said drive control devices; a TIP integrated control unit including an integrated control means for signal processing said measured neutron flux; an integrated unit operation/monitor means for monitoring processing of measured neutron flux in said integrated control means and for communicating with the detector drive system via the integrated control means, said integrated unit operation/monitor means also being connected to said drive control unit for operating and monitoring the drive controlling said detector drive system; and an integrated unit input/output means for inputting/outputting a neutron flux measured by said TIP; a data processing terminal and a printer connected to said TIP integrated control unit; wherein said reactor power measurement and display device displays and records said measured neutron flux and said neutron flux distribution in the axial direction inside said reactor. 4. A reactor power output measurement device according to claim 3 , wherein said reactor power output measurement device includes a memory means for memorizing and storing said measured neutron flux. claim 3 5. Apparatus for calibrating detection sensitivity of a reactor power output measurement device having a local power range monitor for measuring neutron flux within said reactor, said apparatus comprising: a plurality of traversing incore probes (TIP""s) which traverse a core of said reactor, for measuring neutron flux within said core; a plurality of detector drive systems for moving said TIPS, one detector drive system being provided for each TIP; a plurality of drive control units, one drive control unit being associated with each detector drive system, each of said drive control units including a drive control device and a drive unit operation/monitoring means for operating and monitoring said drive control device; and a unified central control unit, including a unified central control device for providing control data to each of said drive control devices and a unified central unit operation/monitor means for operating and monitoring the unified central control device; wherein, in response to a failure of the drive unit operation/monitoring means in a drive control unit, operation and monitoring of the drive control device of the said drive control unit is switchable to said unified central unit operation/monitor device. |
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048184748 | claims | 1. Process for the control of the core of a pressurized water reactor, formed from dismantlable assemblies, each having a group of rods containing fissile material pellets, characterized in that it comprises initially placing in the core at least one first type of assembly, whereof the rods contain uranium oxide pellets and a second type of assembly (10) whose rods (C.sub.1, C.sub.2, C.sub.3) contain mixed uranium and plutonium oxide pellets, the rods of the assemblies of said second type being distributed in accordance with at least two concentric zones (12,14,16) containing mixed oxide pellets having different plutonium concentrations, said concentrations decreasing towards the outside of the assemblies from a central zone (12) towards a peripheral zone (16), making these assemblies (10) undergo successive irradiation cycles and periodically transferring, following each of these irradiation cycles, the rods (C.sub.1, C.sub.2) of each zone (12, 14) of the assemblies of the second type into the adjacent zone (14, 16) towards the outside of said assemblies, the rods (C.sub.3) located in the periheral zone (16) being discharged and new rods (C.sub.4) containing the mixed oxide pellets with a plutonium concentration equal to the plutonium concentration of the pellets contained in the rods (C.sub.1) initially placed in the central zone (12) being loaded into said central zone. 2. Process according to claim 1, characterized in that the same number of rods (C.sub.1, C.sub.2, C.sub.3, C.sub.4) is placed in each of the zones (12,14,16) of the assemblies (10) of the second type. 3. Process according to claim 1, characterized in that the rods of the assemblies (10) of the second type are distributed in three concentric zones (12,14,16). 4. Process according to claim 1, characterized in that each of the assemblies has a dismantlable structure supporting the rods and the structures of the assemblies (10) of the second type are changed after a number of irradiation cycles which is independent of the number of irradiation cycles undergone by the rods (C.sub.1, C.sub.2, C.sub.3, C.sub.4) of said assemblies. 5. Process according to claim 1, characterized in that the assembiles of the first type are replaced after a given number of irradiation cycles, the number of zones (12,14,16) of assemblies of the second type being equal to said number of cycles. |
summary | ||
summary | ||
060569298 | claims | 1. A method of removing .sup.125 I from the interior of a decay chamber in which said .sup.125 I is formed by decay of .sup.125 Xe, said decay chamber comprising an elongate housing having a valved closure at one end thereof and from which xexon is absent which comprises: attaching a needle to said valved closure, immersing said needle in a body of degassed aqueous sodium hydroxide solution, opening said valved closure and permitting agueous sodium hydroxide solution to pass through the opened valved closure in the interior of the housing, closing said valved closure, effecting reflux of said aqueous sodium hydroxide solution within said chamber with said elongate housing in a generally vertical orientation to evaporate water for a pool of said aqueous sodium hydroxide solution at a lower end of said elongate housing to condense evaporated water vapor on the internal walls of the chamber to dissolve .sup.125 I from the internal walls of said chamber and to flow condense back into said pool of aqueous sodium hydroxide solution to form an aqueous solution of .sup.125 I within said chamber, and thereafter opening said valved closure and permitting said aqueous solution of .sup.125 I to flow by gravity through said needle to a storage vessel, thereby removing said solution of .sup.125 I from said chamber. 2. The method of claim 1, wherein said body of degassed aqueous sodium hydroxide solution is housed in an evacuated fill vessel, said aqueous sodium hydroxide solution is permitted to flow downwardly by gravity through said needle extending in a vertically upward direction into said chamber, and following said closing of said valved closure, inverting said elongate housing, whereby said needle extends in a vertically downward direction and said pool of aqueous sodium hydroxide is formed adjacent the valved closure. 3. The method of claim 2 wherein said storage vessel is an evacuated vial with a self sealing septum, said needle is penetrated through the septum before the opening of the valved closure to permit the aqueous solution of .sup.125 I to flow into the storage vessel, said valved closure thereafter is closed and the needle withdrawn from the self-sealing septum. 4. The method of claim 3, wherein said elongate housing is cooled following said refluxing step and prior to said recovery step to condense water vapor present in the housing. |
abstract | Slip joint clamps are installed against guide ears of diffusers at jet pump slip joints. Clamps may prevent vibration and/or movement in the slip joint while not being rigidly attached to the diffuser. Clamps include a compression flipper pressing against a guide ear of the diffuser in a substantially radial direction, a biasing member between the compression member and guide ear that presses the flipper against the guide ear, and supporting structures that hold the flipper and biasing member to the inlet mixer about the guide ear. Systems of slip joint clamps are installed against several guide ears of a single diffuser. Each clamp may radially stabilize the diffuser and inlet mixer while permitting upward relative movement of the inlet mixer. Placement and tensioning of clamps in such systems may be varied so as to prevent or reduce vibrations and/or oscillations between an inlet mixer and diffuser. |
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claims | 1. A focus/detector system of an X-ray apparatus for generating at least one of projective and tomographic phase contrast recordings, comprising:a beam source, including a focus and a focus-side source grating, arranged in the beam path to generate a field of ray-wise coherent X-rays; anda grating/detector arrangement including a phase grating with grating lines arranged parallel to the source grating for generating an interference pattern and a detector including a multiplicity of detector elements arranged in a plane for measuring the radiation intensity behind the phase grating, wherein the detector elements are formed by a multiplicity of elongate detection strips aligned parallel to the grating lines of the phase grating. 2. The focus/detector system as claimed in claim 1, wherein the grating/detector arrangement is designed and arranged so that it satisfies the following geometrical conditions: p 2 = k × p DS p 0 = p 2 × l d , p 1 = 2 × p 0 × p 2 p 0 + p 2 d = l × d ≡ l - d ≡ with d ≡ = 1 2 × ( p 1 2 4 λ ) , h 1 = λ 2 ( n - 1 ) , where:p0=grating period of the source grating G0,p1=grating period of the phase grating G1,p2=large period of the detection strips Ds, spacing of the interference lines after the analysis grating,pDS=small period of the detection strips Ds, distance from midline to midline of neighboring detection strips,d=distance from the phase grating G1 to the analysis grating G2 or to the detection strips DSx in fan beam geometry,d≡=distance from the phase grating G1 to the analysis grating G2 or to the detection strips DSx with parallel beam geometry,k=2,3,4,5, . . . ,l=distance from the source grating G0 to the phase grating G1,λ=selected wavelength of the radiation,h1=bar height of the phase grating G1 in the beam direction,n=refractive index of the grating material of the phase grating. 3. The focus/detector system as claimed in claim 1, wherein the detection strips are designed as directly converting detection strips. 4. The focus/detector system as claimed in claim 1, wherein the n detection strips of at least one detector element are connected at least one of alternately and groupwise to readout electronics via m electronics paths for reading out the radiation intensity in steps of m, where 2=m<<n. 5. The focus/detector system as claimed in claim 4, wherein precisely two electronics paths are provided. 6. The focus/detector system as claimed in claim 4, wherein at least one of precisely three electronics paths and precisely four electronics paths are provided. 7. An X-ray system for generating projective phase contrast recordings comprising at least one focus/detector system as claimed in claim 1. 8. An X-ray C-arc system for generating projective and tomographic phase contrast recordings comprising at least one focus/detector system as claimed in claim 1, arranged on a C-arc rotatable about a subject. 9. An X-ray CT system for generating tomographic phase contrast recordings comprising at least one focus/detector system as claimed in claim 1, arranged on a gantry rotatable about a subject. 10. The X-ray system as claimed in claim 7, further comprising a computation unit to control the offset of the detection strips and to calculate the phase shift from a plurality of intensity measurements of the same ray with differently offset detection strips. 11. The focus/detector system as claimed in claim 2, wherein the detection strips are designed as directly converting detection strips. 12. The focus/detector system as claimed in claim 2, wherein the n detection strips of at least one detector element are connected at least one of alternately and groupwise to readout electronics via m electronics paths for reading out the radiation intensity in steps of m, where 2=m<<n. 13. An X-ray system for generating projective phase contrast recordings comprising at least one focus/detector system as claimed in claim 2. 14. An X-ray C-arc system for generating projective and tomographic phase contrast recordings comprising at least one focus/detector system as claimed in claim 2, arranged on a C-arc rotatable about a subject. 15. An X-ray CT system for generating tomographic phase contrast recordings comprising at least one focus/detector system as claimed in claim 2, arranged on a gantry rotatable about a subject. 16. The X-ray system as claimed in claim 8, further comprising a computation unit to control the offset of the detection strips and to calculate the phase shift from a plurality of intensity measurements of the same ray with differently offset detection strips. 17. The X-ray system as claimed in claim 9, further comprising a computation unit to control the offset of the detection strips and to calculate the phase shift from a plurality of intensity measurements of the same ray with differently offset detection strips. 18. A method for generating projective X-ray recordings of a subject with a focus/detector system of an X-ray apparatus, the focus/detector system including a beam source and a grating/detector arrangement including a phase grating and a detector including a multiplicity of detector elements, wherein the detector elements are formed by a multiplicity of elongate detection strips aligned parallel to grating lines of the phase grating, the method comprising:irradiating the subject by a beam of rays, each ray in space being defined with respect to direction and extent by the focus-detector element connecting line and the extent of the detector element;measuring the average phase shift of each ray wherein, for each ray, the intensity of the radiation is measured with the aid of fine structured detection strips at detection strips connected groupwise and arranged offset with respect to one another or positioned offset from one another; andcompiling phase contrast recordings, the pixel values of which represent the average phase shift per ray, from the measured average phase shifts. 19. The method as claimed in claim 18, wherein the detection strips of a detector element are connected alternately to two measurement paths and, without an intermediate detector offset, at least two intensity measurements are carried out on the two groups of detection strips via the two measurement paths of a detector element, a spatial offset of the groups of detection strips subsequently takes place at least once, and two further measurements are carried out for the same geometrical ray. 20. The method as claimed in claim 18, wherein the spatial offset of the groups of detection strips is performed by circuit technology. 21. The method as claimed in claim 18, wherein the spatial offset of the groups of detection strips is performed physically. 22. The method as claimed in claim 18, wherein the detection strips of a detector element are connected alternately to at least three measurement paths and, without an intermediate detector offset, at least three intensity measurements are carried out on the three groups of detection strips via the three measurement paths of a detector element for a ray. 23. An X-ray system for generating projective phase contrast recordings comprising a computation and control unit including program code to carry out, when executed, the method as claimed in claim 18 during operation. 24. A storage medium at least one of for an X-ray system and of an X-ray system, the storage medium containing program code to carry out, when executed by the X-ray system, the method as claimed in claim 18 during operation of the X-ray system. 25. A computer readable medium including program segments for, when executed on a computer device of an X-ray system, causing the X-ray system to implement the method of claim 18. |
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description | This application is related to U.S. patent application Ser. No. 10/479,272, filed Aug. 29, 2002, entitled “Antiproton Production and Delivery for Imaging and Termination of Undesirable Cells,” which is incorporated herein by reference in its entirety. 1. Field of the Invention The invention relates to the use of radiation to treat medical conditions and, more specifically, to devices, procedures, and systems that controllably deliver antiprotons into a patient for the targeted termination of undesirable cells, such as cancerous cells, within the patient. 2. Background of the Invention Numerous medical conditions are caused by the existence and/or proliferation of unwanted or undesirable cells within a patient. Such conditions include cardiovascular ailments, such as atrial fibrillation and in-stent restenosis of coronary arteries, arteriovenous vascular malformations (AVMs), cardiac arrhythmias, Parkinson's disease, orthopedic ailments, such as post-op ossification, degenerative and inflammatory arthritis and bone spurs, wet macular degeneration, endocrine disorders, such as insulinomas and pituitary adenomas, herniated or inflamed discs, ovary-related conditions, Graves opthalmoplegia, dermatological ailments, such as furunclosis, telangiectasia, Kaposi's sarcoma, genito-urinary conditions, and cancer. More specifically, cancer is caused by the altered regulation of cell proliferation, resulting in the abnormal and deadly formation of cancer cells and spread of tumors. Cells are the basic building blocks and fundamental functioning units of animals, such as human beings. Each cell is composed of a nucleus, which contains chromosomes, surrounded by cytoplasm contained within a cell membrane. Most cells divide by a process called mitosis. While normal cells have functioning restraints that limit the timing and extent of cell division, cancerous cells do not have such functioning restraints and keep dividing to an extent beyond that which is necessary for proper cell repair or replacement. This cell proliferation eventually produces a detectable lump or mass herein referred to as a tumor. If not successfully treated, it can kill the animal host. Cancer that initiates in a single cell, and causes a tumor localized in a specific region, can spread to other parts of the body by direct extension or through the blood stream or lymphatic vessels, which drain the tumor-bearing areas of the body and converge into regional sites containing nests of lymph nodes. The ability of cancer cells to invade into adjacent tissue and spread to distant sites (metastasize) is dependent upon having access to a blood supply. As such, tumors larger than 2 mm have a network of blood vessels growing into them, which can be highly fragile and susceptible to breakage. Several general categories of cancer exist. Carcinomas are cancers arising from epithelial (squamous cell carcinoma) or secretory surfaces (adenocarcinomas); sarcomas are cancers arising within supporting structures such as bone, muscle, cartilage, fat or fibrous tissue; hematological malignancies are cancers arising from blood cell elements such as leukemia lymphoma and myeloma. Other cancers include brain cancers, nerve cancers, melanomas, and germ cell cancers (testicular and ovarian cancers). Carcinomas are the most common types of cancers and include lung, breast, prostate, gastrointestinal, skin, cervix, oral, kidney and bladder cancer. The most frequently diagnosed cancer in men is prostate cancer; in women it is breast cancer. The lifetime risk of a person developing cancer is about 2 in 5 with the risk of death from cancer being about 1 in 5. Diagnosing cancer often involves the detection of an unusual mass within the body, usually through some imaging process such as X-ray, Magnetic Resonance Imaging (MRI), or Computed Tomography (CT) scanning, followed by the surgical removal of a specimen of that mass (biopsy) and examination by a pathologist who examines the specimen to determine if it is cancer and, if so, the type of cancer. Positron Emission Tomography (PET) can be used to non-invasively detect abnormally high glucose metabolic activity in tissue areas and thereby assist in the detection of some cancers. The cancer is then assigned a stage that refers to the extent of the cancer. Each cancer has a staging protocol designated by organ. Conventionally, Stage I indicates the existence of a detectable tumor under a specified size, depending on cancer type. Stage II indicates that the cancer has spread into adjacent tissue or lymph nodes. Stage III indicates that the cancer has spread beyond its own region or has grown to a minimum size qualifying it for Stage III status, and Stage IV indicates that the cancer involves another organ(s) at a distant site. Stages are typically assigned by physical examination, radiographic imaging, clinical laboratory data, or sometimes by exploratory surgery. Once diagnosed and identified in terms of characteristics, location, and stage, the cancer is treated using one, or a combination of several, methods, including surgery, chemotherapy, and radiation. Other less commonly used treatment approaches do exist, including immunotherapy. The cancer is treated with one or several basic goals in mind: cure, prevention of spread, prolongation of survival, and/or palliation (symptom relief). Surgery is currently a preferred treatment approach where the cancer is localized, in an early stage, and present in only one place. Preferably, the cancer is within a substantial margin of normal tissue and can be excised without unacceptable morbidity or incurring the risk of death. Moreover, for surgery to be successful, the cancer should have little potential to spread to other parts of the body. Surgery needs to be followed up by diagnostic imaging to determine if the cancer has been removed and, in many cases, subsequent adjuvant radiation and/or chemotherapy is administered. Chemotherapy, usually employing medicines that are toxic to cancer cells, is given by injection into the blood stream or by pill. With certain limitations, the chemotherapeutic agents travel to all parts of the body and can treat cancer in any location by interfering with cell division. Although affecting cancer cells to a greater extent, chemotherapeutic agents do interfere with normal cell division as well, causing severe side effects and adverse health consequences to patients, such as kidney failure, severe diarrheas, or respiratory problems. Certain agents are highly toxic to the heart, reproductive organs, and/or nerves. Almost all are toxic to the bone marrow, which is responsible for the production of the white and the red blood cells and platelets. Because white blood cells such as granulocytes, monocytes and lymphocytes, are primarily responsible for fighting infections and platelets are essential for clotting, chemotherapeutic agents often cause patients to be highly susceptible to infections and spontaneous bleeding. Other side effects include nausea and ulcerations. The course of chemotherapy requires a number of dosage cycles to attack cancer cells, permit healthy cells to recover, and then again attack the target cancer cells. Depending on the patient's response, a decision is made to either stop treatment or continue with some sort of maintenance dosage. Radiation therapy is the exposing of cancerous cells to ionizing radiation with the objective of terminating those cells over one or several division cycles. Conventionally, radiation is delivered by sending an energy beam, typically x-rays, through a pathway containing healthy tissue and into the target cancerous region. Because energy is being driven through healthy tissue, medical practitioners must determine the best way to deliver sufficient energy to kill a plurality of cancerous cells without generating unacceptable levels of collateral damage to adjacent normal tissue. Several factors should be taken into account, including, for example: 1) the energy deposition profile, which determines what amount of energy a particular radiation beam, having a particular energy level, will deliver to the pathway relative to the target cancer cells, 2) the amount of energy needed to terminate cancerous cells, which determines the threshold level of energy that needs to be delivered to the target site and, consequently, what amount of collateral damage may have to be tolerated in order to do so, and 3) the size, shape, and location of the tumor, which is used to calculate the requisite radiation dosage and determine the appropriate configurations by which radiation beams can be delivered to the target site. Conventional radiation therapies are frequently unable to deliver sufficiently high levels of radiation to a target region without generating unacceptably high levels of collateral damage. The most common radiation therapy, x-ray (or photon), has a linear energy transfer (LET) profile that varies with depth. The LET of photon radiation increases initially and then decreases with depth, often depositing more energy in intervening tissue than in the target tumor site for deeply buried targets. Photons also continue traveling through the body, once they pass the target region, further depositing energy in healthy tissue. Photons are therefore unable to precisely target a tumor region without endangering surrounding normal tissues. As such, x-ray radiation treatment sequentially delivers small doses of radiation (fractions) capable of terminating cancerous cells without inflicting too much damage on normal cells. Dividing cells are more susceptible to radiation damage; non-dividing (i.e. resting cells) are less susceptible. X-ray radiation is very often delivered using multiple fields that are required to avoid repeatedly exposing a single healthy tissue pathway to lethal radiation. For example, a typical treatment regimen may require 20-25 exposures in which 200 RADS (Radiation Adsorbed Dose) are delivered per day, 5 days per week for 5 weeks, resulting in a total dose of 5,000 RADS, or 50 Grays, where several of those exposures occur through different pathways having the same target region, an isocenter, in common. Frequent radiation treatments (fractionation of dose) need to occur over a large portion of the replication cycle of a particular cancer, explaining the basis for why a series of treatments over several weeks is required to treat cancer with photon radiation therapy. It should be noted that, even with treatment fractionation and using multiple dose delivery pathways, the collateral damage causes substantial adverse health consequences, from nausea and pain to the permanent disruption of mucosal linings surfaces and adjacent supporting structures. Proton therapy is another form of radiation therapy currently being used to treat cancer. Relative to other conventional approaches, protons have improved physical properties for radiation therapy because, as a radiation source, they are amenable to control, and thus the radiation oncologist can more precisely shape dose distribution inside a patient's body. Therefore, the dose delivered by a proton beam may be better localized in space relative to conventional radiation therapies, both in the lateral direction and in depth, causing more destruction at a target site with correspondingly less collateral damage. As shown in FIG. 1, where the target tumor site is at a depth of 25 cm, a mono-energetic proton beam 110 deposits the same energy dosage as a beam of photon energy 105 at the target point. However, the collateral damage, represented by the difference 115, 120 in the areas under the curves between the energy dosages of the two respective beams 110, 105 (measured in areas outside the target region 125), is far greater for the photon beam 105. As a result, the proton beam 110 delivers the same termination power at the tumor site with correspondingly less collateral damage. A substantial amount of investment has been made in researching proton therapies and building and deploying a proton therapy infrastructure, including proton accelerators, proton delivery devices, such as proton gantries, and specialized medical facilities. Despite this substantial investment, proton therapy still has several significant disadvantages. Most significantly, while the energy deposition profile in proton radiation represents an improvement over conventional approaches, it still does not deliver sufficient amount of termination power at a tumor site relative to the collateral damage it causes. Another cancer therapy, heavy ion therapy, uses a heavy ion, namely an atom (e.g., a carbon atom) that has been stripped of its electrons, to deliver cancer cell terminating energy to a target region. Like proton beam therapy, heavy ion therapy has the ability to deposit energy directly into the cancerous tumor in three dimensions, hence the dose delivered by the heavy ion beam may also be better localized in space relative to conventional radiation therapies both in lateral direction and in depth. Heavy ions deposit more energy into a tumor than do protons and hence have more cancer cell killing capability than do protons. Heavy ions do have the capability of killing resting cells, but while the killing power deposited on the tumor for ion therapy is dramatically greater, the collateral damage to healthy intervening tissue (that issue between the skin surface and the tumor) is likewise greater even greater collateral damage than for conventional radiation. In fact, collateral damage inflicted by heavy ion therapy can be even greater than the direct damage to the tumor with proton therapy. Additionally, in certain heavy ion therapy applications, treatment imaging is enabled by the fragmentation of the heavy ion, such as 12C, as it approaches a patient in-beam and as it strikes cells while traveling through a patient. The heavy ion fragments into isotopes that may be imaged through conventional PET detection, that being 11C in the case of 12C heavy ion therapy. This imaging process is not, however, real-time in that imaging is delayed until the radioisotope decays and is substantially complicated by the migration of the isotope within the tumor A system for treating target cells with both positive and negative ions comprises a bi-polar beam delivery system configured to create and deliver both positive ion beams and negative ion beams. The bi-polar beam delivery system comprises a bi-polar accelerator configured to accelerate positive and negative ions in the same direction making such a bi-polar beam delivery system practical. In one aspect, the bi-polar accelerator comprises arced sections, possibly several straight sections, and a plurality of bending magnets configured to direct the positive and negative ions around the arced sections. In another aspect, the bi-polar beam delivery system also comprises a configurable power supply coupled with the plurality of bending magnets, the configurable power supply configured to supply a reversible current to the bending magnets so as to reverse the polarity of the magnetic field generated by the bending magnets as required to accelerate both positive and negative ions in the same direction. These and other features, aspects, and embodiments of the invention are described below in the section entitled “Detailed Description.” The embodiments disclosed herein are related to methods and systems for the use of antiprotons for the termination of cells, including, but not limited to use for the treatment of medical conditions caused by existing or proliferating unwanted or undesirable cells, such as cancer, and the accompanying devices, systems, and processes to conduct such treatments. Such conditions include cardiovascular ailments, such as atial fibrillation and in-stent restenosis of coronary arteries, arteriovenous vascular malformations (AVMs), cardiac arrhythmias, Parkinson's disease, orthopedic ailments, such as post-op ossification, degenerative and inflammatory arthritis and bone spurs, wet macular degeneration, endocrine disorders, such as insulinomas and pituitary adenomas, herniated or inflamed discs, ovary-related conditions, Graves opthalmoplegia, dermatological ailments, such as furunclosis, telangiectasia, Kaposi's sarcoma, genito-urinary conditions, and cancer. While the detailed description provided herein primarily discusses the application of certain example systems and methods to the termination of cancerous cells, one of ordinary skill in the art will appreciate that the methods and systems can be applied to the termination of any type of unwanted or undesirable cell. The specific use of cancer in the present description should not be interpreted to limit the application of the methods and systems to the treatment of cancer. Furthermore, unwanted and undesirable shall be used interchangeably to describe the cells which are the preferred targets of the antiprotons as described herein. Antiprotons have been identified as a preferential radiation source for the treatment of cancer for several reasons. First, as discussed herein, antiproton production and distribution are now technically and economically feasible, making antiprotons a viable radiation source for medical treatments. Second, as antiprotons travel through a substance, such as human tissue, they transfer energy in a manner similar to other charged particles. As with protons, antiprotons lose kinetic energy as they pass through a substance, causing collateral damage to the healthy tissue pathway. The theory of energy loss for a charged particle can be described by the following equation, where the stopping power (dE/dx) in MeV is approximated using ρ (g/cm3) as the density of the medium, β is the velocity (v/c) of the moving particle, f(β)=In(2 mc2β2/(1−(β2))=β2, m is the mass of the electron (0.51 MeV/c2), and Zi, Ai, Ci and Ii (MeV) are the atomic number, weight, concentration, and excitation potential of the ith element, respectively. - 1 ρ ⅆ E ⅆ X = 0.30708 β 2 · ∑ Z i · C i A i { f ( β ) - ln I i } As the velocity of a charged particle decreases, the stopping power increases rapidly because of the inverse proportional dependence on particle velocity (β2). The result is a very large energy deposition toward the end point which, in the case of cancer therapy, is in the tumor itself. The large final energy deposition causes a sharp Bragg Peak, as shown in FIG. 1 for proton therapy. Unlike protons, however, antiprotons undergo a highly energetic annihilation event, releasing a plurality of charged and neutral particles and causing a much greater amount of damage in the target region, once they slow down in the target area and become captured in a nucleus or as they pass through the target area. Referring to FIG. 1a, when an antiproton 105a comes to rest with a nucleus, it generates an annihilation event 110A, in which several by-products are generated, including gamma radiation 115A, mesons (both charged and neutral pions) 120A, and heavy charged particles 125A. The heavy charged particles are highly destructive to nuclei adjacent to the annihilation site and, therefore, propagate the damage incurred from the initial antiproton annihilation to adjacent cells, thereby terminating more cells in the course of a single antiproton exposure. This unique annihilation event allows for the targeted, localized delivery of larger amounts of cell-terminating radiation with substantially similar amounts of collateral damage, thereby permitting cancer treatment regimens that do not require fractionated treatment protocols. The nature of this annihilation event is an important element in the proper determination of dosage and to the real-time imaging process, as later discussed herein. Referring to FIG. 2, the relative doses (arbitrary units) of various radiation sources are shown in relation to depth of energy deposition in tissue. A target tumor site 203 is identified at a particular depth, such as 11-12 cm. A mono-energetic proton beam 210 delivers a relative biological dose of 1, as compared to a beam of photon energy 205, which delivers a relative biological dose of approximately 0.65. An antiproton beam 220 substantially overlays with the proton beam 210, but has a greater relative dose at greater than 1.2, the difference being represented by 225. Despite the greater relative dose, the antiproton beam 220 has substantially similar amounts of collateral damage compared to the proton beam 210 and far less collateral damage compared to the photon beam 205, the collateral damage being caused by the deposition of energy over the region 230 between the skin surface and tumor site. As a result, the antiproton beam 220 delivers the greater termination power at the tumor site 203 with correspondingly less collateral damage (the difference in collateral damage determined by taking the difference between the integrated areas under beam curve 210 and beam curve 220 calculated over region 230). From a different perspective, for the same collateral damage, the antiproton beam can deliver far greater termination power at the tumor site relative to proton and photon radiation sources. One example embodiment, as diagrammed in FIG. 3, comprises the production of antiprotons 305, the collection and then deceleration of antiprotons to a desired energy level 310, the storage and cooling of antiprotons 312, the storage of antiprotons in a cooling ring or delivery synchrotron 313, the formation of antiprotons into an administrable beam 315, the measurement of antiprotons to determine the actual number being delivered 320, the delivery of that measured beam via an antiproton delivery and imaging device to a prepared patent 325, optionally though preferably the dose measurement and imaging of the resultant radiation event and comparison of that image to previously recorded images of the target area 330, and, optionally, though preferably, the adjustment of dosage characteristics to insure the impacted area, as imaged, aligns with the desired target area 335. Prior to the delivery step, a patient had been prepared, optionally, though preferably, by imaging the target area 340 using imaging technologies, to confirm the size, location, and configurational characteristics of the target tumor, and determining an appropriate treatment regimen in light of the tumor characteristics 345. A patient is then securely positioned relative to the antiproton delivery and image device. The treatment regimen data informs the extent of deceleration 310 (i.e. the predetermined delivery energy of the antiprotons useful for treatment), antiproton delivery methodology 325, and the dose measurement and imaging of the resultant radiation event and comparison of that image to previously recorded images of the target area 330. Another embodiment, as diagrammed in FIG. 4, comprises the production of antiprotons 405, the collection, deceleration and cooling of antiprotons 410, the trapping of cooled and slowed antiprotons into a trap device 412, the transport of the trap device to a medical facility 413, the reception and acceleration (i.e. to a suitable energy) of antiprotons at the medical facility 414, the cooling and formation of antiprotons into an administrable beam 415, the measurement of antiprotons to determine the actual number being delivered 420, the delivery of that measured beam via an antiproton delivery and imaging device to a prepared patient 425, optionally though preferably the dose measurement and imaging of the resultant radiation event and comparison of that image to previously recorded images of the target area 430, and, optionally though preferably, the adjustment of dosage characteristics to insure the impacted area, as imaged, aligns with the desired target area 435. Prior to the delivery step, a patient had been prepared, optionally though preferably, by imaging the target area 440 using imaging technologies, to confirm the size, location, and configurational characteristics of the target tumor, and determining an appropriate treatment regimen in light of the tumor characteristics 445. A patient is then securely positioned relative to the antiproton delivery and image device. The treatment regimen data informs the extent of antiproton acceleration (i.e. the delivery energy of the antiprotons needed for treatment) 414, antiproton delivery methodology 425, and the dose measurement and imaging of the resultant radiation event and comparison of that image to previously recorded images of the target area 430. These embodiments, along with other embodiments, shall be discussed in greater detail in each of the subsequent sections. 1. Antiproton Production Antiprotons for use in the systems and methods disclosed herein can be generated by any method. The antiproton generation process is described herein using a circular accelerator, such as the one found at Fermi National Laboratory in Batavia, Ill. It should be noted, however, that the Fermi accelerator has been designed to generate antiprotons having far greater energies than that which are generally preferred for use in connection with the systems and methods disclosed herein. Although such antiprotons may be effectively altered to suit the methods, as discussed below. Different accelerators, such as a circular accelerator that accelerates particles to energies lower than those achieved by Fermi National Accelerator Laboratory, can also be effectively used in the context of the methods and systems described herein. In one example embodiment, antiproton production comprises a six-stage process, culminating in the deceleration of antiprotons for medical application or storage and trapping, as discussed in the subsequent sections. Referring now to FIG. 5, a device (not shown), an exemplary embodiment of which is a Cockroft-Walton is used to add electrons to hydrogen atoms delivered from a source 510, resulting in negative ions consisting of two electrons and one proton. The device applies a positive voltage to the negative ions, thereby accelerating them. In one embodiment, the negative ions are accelerated to an energy of approximately 750 keV. In the embodiment of FIG. 5, the negative ions are transferred from the Cockroft-Walton device and enter into a linear accelerator (or a Linear Injector) 505, referred to as a Linac, which comprises a plurality of tanks filled with tubes spaced varying distances apart. An electric field is applied to the tubes, repeatedly reversing in direction, causing the negative ions to alternately hide in tubes when the electric field, as applied, will slow them down, and emerge into gaps between the tubes when the field is of a direction that accelerates them. The Linac 505 further increases the energy of the ions to approximately 400 MeV. The negative ions are passed through a carbon foil, thereby removing the electrons and leaving protons, which are then passed into a booster synchrotron 515. The booster synchrotron 515 is a circular accelerator, a rapid cycling synchrotron that forces the positively charged particles to travel in a circular path through the application of magnetic fields. Through each revolution, the protons experience the repeated application of accelerating electric fields and therefore increase in energy. In one embodiment, the booster 515 raises the energy level of protons to about 8 GeV, cycles approximately 12 times in rapid succession, and introduces about 12 proton packets (pulses) into the main accelerator ring 520, which is a synchrotron that further accelerates the protons to about 150 GeV. In the embodiment, the accelerator 520 is approximately four miles in circumference with a tunnel ten feet in diameter and housing approximately 1,000 copper-coiled magnets to bend and focus the protons. In another embodiment, the booster 515 introduces proton packets into a 14 GeV main accelerator ring 520. In this embodiment, antiprotons are produced by extracting bunches of approximately 120 GeV protons from this synchrotron ring 520, transporting them via a beamline 523 to a production target 525, and focusing them on the target 525. In other embodiments, the protons can be at other energies as would be recognized by those skilled in the art. The proton collisions with the target 525 produce a number of particles, including antiprotons. The produced antiprotons are selected, as shown in FIG. 6, and transported to a ring 530 where they are debunched and then cooled, e.g., by a process referred to as stochastic cooling. In this context, beam cooling is the technique where both the physical size and energy spread of a particle beam circulating in a cooling/storage ring are reduced with little accompanying beam loss, as further discussed below. Subsequently, the antiprotons are transferred to another ring 535 for deceleration or acceleration to appropriate energies for delivery to a specialized antiproton trap 540, to a treatment system 545 or for accumulation and/or storage. Antiprotons are created by the interaction of high-energy protons with nuclei in the target area. Referring now to FIG. 6, a schematic diagram of antiproton production is provided. Protons 605 having an energy level are focused on, and impact, a target 610. The target is preferably comprised of a metallic material that is relatively easy to remove heat from, such as copper, nickel, or iridium. In approximately one collision per million, an antiproton-proton pair is formed. In one operation, approximately 10 trillion protons impinge on the target per minute, generating 10 million antiprotons. Using magnets 615, antiprotons are separated from the positively charged protons and directed toward a system and process for cooling the antiproton beam. As previously stated, antiprotons can be created in a number of different ways. In another embodiment, protons are accelerated in a linear accelerator, a booster, and then a synchrotron up to about 27 GeV. The protons are focused onto a target, such as the materials mentioned above, and, in the interaction of the protons with the target nuclei, produce many particle-antiparticle pairs, including proton-antiproton pairs. One of ordinary skill in the art will appreciate that the systems and methods described herein is not limited to the above-described antiproton generation methods. For example, other methods and systems for generating negative hydrogen ions, not simply a Cockroft-Walton device may be used. Additionally, while specific energy levels have been described, other methods can be effectively performed by generating antiprotons from protons accelerated to any appropriate range, such as approximately 12 GeV/c, 11 GeV/c, 10 GeV/c, 13 GeV/c, among other values. In certain embodiment, a circular accelerator with a smaller circumference is used to generate protons and antiprotons at lower energy levels, thereby allowing for a more cost-effective antiproton production method. The process of producing antiprotons results in a plurality of antiprotons moving at high momentum, with varying energies (referred to as energy spreads) and directions (referred to as transverse oscillations). To commercially deploy antiprotons, however, such energy spreads and transverse oscillations are preferably reduced. The term “cooling” refers to the reduction of the beam's transverse dimensions and energy spread. Electric fields are preferably applied to antiprotons, as they travel through a vacuum pipe ring structure. Within the radio frequency cavities, as antiprotons decelerate, the size of their transverse oscillations increase. If not managed properly, a substantial number of antiprotons can be lost in this process. Among the cooling methods that may be used to avoid excessive antiproton loss are stochastic cooling and electron cooling. Electron cooling uses an electron beam merged with the antiproton beam to act as a heat exchanger and is more effective at low energy. In stochastic cooling, the beam is positionally sampled by a monitor and an error signal generated in a monitor is fed back, via a corrector, to the beam sample that created it. This process eventually centers the sample's characteristics towards an average value, after a large number of passages through the apparatus. In certain embodiments, generated antiprotons are decelerated to an energy level suitable for the particular medical treatment methodology being employed. More specifically, where a medical facility is located proximate to the antiproton generation location, generated antiprotons are preferably slowed from their generation energies to a medically beneficial energy level, such as between 1 MeV and 300 MeV, preferably around 250 MeV, and delivered directly to a patient, as further discussed below. To do so, a deceleration, cooling, and collection process is performed. Antiprotons are decelerated to a low energy level, for example between 1.5 and 3 GeV/c, or alternatively, they are generated at that energy. In one embodiment, the deceleration process is performed using the aforementioned cooling techniques in a separate, dedicated deceleration ring. In another embodiment, this first deceleration step is unnecessary because a low-energy antiproton production method is used and consequently generates low energy antiprotons, such as in the 1.5-3 GeV/c range. It should be noted that the 1.5-3 GeV/c energy range is not meant to be restrictive of the low energy range. Once in the 1.5 GeV/c range, antiprotons are collected and further decelerated to a medically beneficial energy level, such as about 250 MeV. In one example embodiment, this collection and second deceleration stage is conducted by employing the aforementioned cooling and deceleration techniques in a dedicated cooling and deceleration ring. The antiprotons can be stored either in the cooling ring or in the delivery synchrotron. As discussed below, the antiprotons, once a medically beneficial energy level, are introduced via a beam line to a patient, a controlled, adjustable energy level, through a number of alternative antiproton delivery devices. Alternatively, where a medical facility is not proximate to an antiproton production location, preferably antiprotons are produced, stored, and transported to facility sites. Antiprotons are therefore similarly decelerated down to an appropriate level, after which the antiprotons are squeezed out in groups, referred to as bunches, and ejected through the application of a kicker magnet which leads the ejected antiprotons through a separate line into an accumulator, collector, or some other storage device. A person familiar with high-energy physics will understand how to produce, collect, cool, decelerate and extract antiprotons through the application of vacuums pumps, magnets, radiofrequency cavities, high voltage instruments and electronic circuits. Antiprotons circulate inside vacuum pipes in order to avoid contact with matter with which they annihilate. The vacuum should be as high as possible and therefore several vacuum pumps, which extract air, are placed around the pipe. The magnets used include dipoles, which serve to change the direction of antiproton movement and insure they stay within the circular track, and quadrupoles, which are used as lenses or focusing magnets to insure that antiproton beam size is smaller than the vacuum pipe size. Electric fields are used to modify antiproton energy levels and are provided for by radio-frequency cavities that produce high voltages synchronized with the rotation of antiprotons around the ring. Antiprotons may either be stored in a ring for future use or in traps for distribution to antiproton medical facilities. In one embodiment, antiprotons are stored in traps, such as those disclosed in U.S. Pat. Nos. 6,160,263 and 5,977,554 which are incorporated herein by reference. The trapped antiprotons are inserted into a linear accelerator or synchrotron, accelerated to appropriate energy levels, and then formed into a beam for use in treatment. Operationally, the trap is attached to an inlet port that interfaces with a Linac or RFQ. The electric field used to trap the voltage is decreased while an attracting field is generated in the accelerator, causing the antiprotons to drift into the accelerator structure. Antiprotons therefore drift from the trap at very low energies, on the order of about 10-20 KeV. Once the antiprotons are positioned inside the accelerator, they are accelerated to an appropriate energy level. The delivery synchrotron is preferably designed to be stable at 1 MeV-300 MeV energy levels and will result in antiprotons being delivered at certain minimum energies, which can be accelerated by using a small Linac or an RFQ. An exemplary cyclotron will preferably be designed for the production of an antiproton beam, i.e. 1.5 mAproton current at 590 MeV. Whether obtaining the antiprotons from a decelerator attached to the main antiproton production source or obtaining antiprotons from a trapped state and accelerating them, a main antiproton beam is generated. The beam is stored and conditioned in a delivery synchrotron. The stored antiprotons can then be adjusted to an appropriate energy level while in the delivery synchrotron. Adjustment of the energy can be readily achieved such as by using the rapid-cycling energy characteristic of the delivery synchrotron or by using a set of carbon or copper degrader blocks, or a combination of the two methods. In a combination mode, the energy of the beam can be adjusted by changing the arrangement of the degrader blocks to provide variable degrader thicknesses to the beam and by tuning the beam line to the appropriate delivery momentum. In one example embodiment, no degrader blocks are used to adjust the beam energy, as the degrader processes may produce spurious particle emissions such as undesired neutrons. Spurious particle emission is generally avoided if the delivery synchrotron is adjusted to provide particles of the desired target energy level directly. A calculated number of antiprotons at the correct energy is then split off the stored beam using an electrostatic splitter for delivery to a patient. For medical applications, the target energy level may vary between about 1 MeV and 300 MeV, preferably about 250 MeV and including 5 MeV, 10 MeV, 15 MeV, 20 MeV, 25 MeV, 30 MeV, 35 MeV, 40 MeV, 45 MeV, 50 MeV, 55 MeV, 60 MeV, 65 MeV, 70 MeV, 75 MeV, 80 MeV, 85 MeV, 90 MeV, 95 MeV, 100 MeV, 105 MeV, 110 MeV, 115 MeV, 120 MeV, 125 MeV, 130 MeV, 135 MeV, 140 MeV, 145 MeV, 150 MeV, 155 MeV, 160 MeV, 165 MeV, 170 MeV, 175 MeV, 180 MeV, 185 MeV, 190 MeV, 195 MeV, 200 MeV, 205 MeV, 210 MeV, 220 MeV, 225 MeV, 230 MeV, 235 MeV, 240 MeV, 245 MeV, 250 MeV, 255 MeV, 260 MeV, 265 MeV, 270 MeV, 275 MeV, 280 MeV, 285 MeV, 290 MeV, 295 MeV, and 300 MeV. The specific energy used at any time depends upon the particle penetration depth for the specific treatment being performed. The particle beam is preferably analyzed in momentum and phase space using beam profile monitors to insure the resultant beam is appropriately shaped and is substantially monochromatic in order to couple the beam into the delivery device. The delivery synchrotron can provide substantially monochromatic particles directly by the intrinsic nature of the synchrotron acceleration process. The shape characteristic of the particle beam can be adjustable by means of a pair of magnetic quadrupole focusing elements positioned along the delivery beam pipe. In treatments requiring high spatial resolution, the beam will be focused into a small spot size using the magnetic quadrupole focusing elements. Other treatments can use a broader, less highly focused beam. A continuous range of beam geometries between broad and sharply focused can be achieved using the magnetic quadrupole focusing elements, without affecting the monochromatic nature of the beam. The beam is then introduced into a beam line, a vacuum pipe, that is directed into the antiproton radiating and imaging device. 2. Antiproton Radiating and Imaging Device The beam line is directed through an antiproton radiating and imaging device in order to administer antiproton radiation to a patient. In one embodiment, a gantry is used to deliver antiprotons to a patient, or a proton therapy gantry is retrofitted to accept and deliver antiprotons instead of protons. Referring to FIG. 7, an antiproton gantry is shown. The antiproton gantry comprises a delivery pipe 1005 passing through a shielded support structure 1010 and into a gantry head 1015 through which the antiprotons are directed into a patient 1020. Although not required, the delivery pipe 1005 bends as it extends out from an accelerator (not shown), through the structure 1010, and into the gantry head 1015 through the application of magnets 1030. More specifically, in the illustrated embodiment, the antiproton beam (not shown) enters into the structure 1010 via the vacuum pipe 1005 and is deflected by two 35 degrees bending magnets 1030 that are parallel to the rotation axis of the gantry head 1015. Once in the gantry head 1015, the beam is directed, through the use of a magnet 1030, through a nozzle 1035 having a monitor and range shifter system (not shown), and into the patient 1020. In addition to the plurality of magnets 1030, there are preferably also focusing quadrupole magnets (not shown). Preferably the support structure 1010 is designed to provide maximum rigidity to the beam line. The weight of the entire gantry generally is dominated by the bending magnets 1030 and appropriate balancing weights should be provided in the structure 1010 to insure the gantry does not fall, tip, or otherwise become unstable. Operationally, the antiproton beam is deposited in the patient as a sequence of sequential, directed applications. Referring to FIG. 8, the number of antiprotons delivered in a single, directed application is measured by the beam monitor system 1140 positioned in the nozzle 1135. In one embodiment, the beam monitoring system comprises two monitoring subsystems providing two independent beam flux measurements. The first subsystem comprises two parallel plane ionization chambers. The first chamber covers the size of the full swept beam. The external high-voltage planes are preferably made of thin Mylar foils, approximately 25 microns, coated with aluminum. The signal plane in the middle of the chamber is generally open to air and operates at about 2 kV. The gap between the signal and high voltage foils is approximately 5 mm on each side of the signal plane, allowing for a fast collection time of less than 100 microseconds. The second chamber is a similar ionization chamber with a larger gap, i.e. 1 cm, and a lower electric field, i.e. 2 kV of applied voltage. The reaction time of the second monitor is slower. The second subsystem comprises of a position sensitive monitor made of kapton foils coated with 4 mm wide aluminum strips. The ionization charge created in the gap of the chamber is collected on the different strips, providing the information on the position and shape of the antiproton beam. In certain embodiments, This information is monitored continuously during treatment by reading the content of scalers at the end of each spot. Preferably, two strip planes are used, one for the direction perpendicular to the sweeper displacement and the other parallel to it. It should be further noted that other methods and systems can be used to monitor the beam. For example, measuring antiproton delivery rates can be achieved by calculating the difference between how many antiprotons are left in a storage device, cooling ring, or other source after a pulse of antiprotons has been delivered to the synchrotron relative to how many antiprotons were present in the source prior to the pulse. Once the target number of antiprotons has been reached, the beam is switched off using a fast kicker-magnet (not shown) located in the beam line ahead of the gantry head 1115. In one embodiment, the fast kicker magnet is a 20 cm long, laminated C-magnet with a 5 cm pole gap, and the vacuum chamber is an elliptical pipe comprised of a material capable of enabling the generation and maintenance of a sufficiently high vacuum level. The lamination of the magnet and the material of the beam pipe are chosen to avoid eddy current effects during switching of the kicker magnet. In one embodiment, Ferrite Philips 8C11 may be used for the yoke of the kicker magnet to minimize eddy currents and aid compatibility with the ultra-high vacuum environment. The kicker magnet is operated at 50 amps to deflect the beam in the vertical direction. With this device, the beam can be switched on and off in less than 50 microseconds. The depth of the dose deposition is measured by a range shifter system 1145. The range shifter is placed in the nozzle, behind the monitoring system, and, in one embodiment, consists of 40 degrader plates, which cover the full swept beam. Pneumatic valves can be used to move individual plates into the beam path. The mechanical movement of the beam takes approximately 30 ms per plate. Using a single command, removing all plates from the beam path can occur in approximately 200 ms. Of the 40 plates, 36 are made of polyethylene and have a thickness equal to an antiproton range of 4.7 mm in water. One plate has only half that thickness to allow for a more precise depth scanning at low energy. Three plates are made of thin lead foil and can be used to enlarge the spot size, if desired. The projected dead time contribution from the range shifter system is 35-40 seconds, 30 seconds to move plates into the beam path and 5-10 seconds to remove the full stack. Additional devices can be used to contour the beam, including specially designed metal alloys. These devices may be used at the outlet of the nozzle (not shown) and can conform the beam to the cross-sectional size and shape of the target area within the patient. In some embodiments, a beam is formed and delivered without the use of degraders or other devices to physically contour the beam. The inclusion of barriers, structures, or other materials within the beam line can cause the unwanted generation of particles, such as pions, neutrons and gamma rays, that will dose the patient without any beneficial medical purpose. To vary dosage levels, it can be preferred, depending on the embodiment, to use a variable energy synchrotron whose energy level can be modified as needed to deliver antiprotons to the requisite depth. In another embodiment, shown in FIG. 9, a delivery pipe 940 is directed through a series of magnets 919, 915, 917, 910 and positioned relative to a patient table 930. The delivery pipe 940 bends as it extends out from an accelerator (not shown), through a shielded support structure 905, and into the plurality of delivery heads 935 through the application of magnets 919, 910, 917, 915. Operationally, the fixed delivery mechanism can deliver an antiproton beam 920 from multiple directions without requiring a rotatable gantry. The present embodiment can therefore direct multiple antiproton beams 920 to target a single isocenter without requiring the more complex gantry structure. While the present embodiment is shown having three delivery points from which fixed beams 920 are emitted in the direction of the patient table 930, one of ordinary skill in the art will appreciate that, using the appropriate number and type of bending magnets, the beam line can be designed to deliver any number of fixed beam configurations directed toward the patient table. More specifically, in the illustrated embodiment, the antiproton beam (not shown) enters into the structure 905 via the vacuum pipe 940. The vacuum pipe extends through one 135 degree bending magnet 910, present in line with the delivery pipe 940, and into a nozzle head 935. When activated by a control system (not shown), the bending magnet 910 operates to redirect the antiproton beam into a second vacuum pipe section 940a, into a first 90 degree bending magnet 915, and through a second nozzle head 935, if the 90 degree bending magnet 915 is activated by a control system (not shown). If the 90 degree bending magnet 915 is unactivated, a first 45 degree bending magnet 917 is activated to redirect the antiproton beam into and through a third vacuum pipe section 940b, into a second 135 degree bending magnet 919, and through a third nozzle head 935. The first 45 degree bending magnet 917 and first 90 degree bending magnet 915 are shown in FIG. 9 as being co-located in the same area. Preferably the support structure 905 is designed to provide maximum rigidity to the beam line. The weight of the entire gantry is generally dominated by the bending magnets 919, 910, 915, 917 and appropriate balancing weights should be provided in the structure 905 to insure the gantry does not fall, tip, or otherwise become unstable. Operationally, the antiproton beam is deposited in the patient preferably as a sequence of sequential pulses, directed from one, or a combination of several, delivery points defined by nozzles 935. For example, in operation, the 135 degree bending magnet 910 can be inactivated by a control system (not shown) to allow an antiproton beam to travel into and through a nozzle head 935 having a monitor and range shifter system (not shown), and into the patient (not shown). Where a second beam impingement path is desired, e.g. through a second delivery point, the 135 degree bending magnet 910 can be activated by a control system (not shown) to allow an antiproton beam to be redirected into the first 90 degree bending magnet and, if activated, through a nozzle head 935 having a monitor and range shifter system (not shown) and into the patient (not shown). Where a third beam impingement path is desired, the first 45 degree bending magnet 917 can be activated by a control system (not shown) to allow an antiproton beam to be redirected into the second 135 degree bending magnet and, if activated, through a nozzle head 935 having a monitor and range shifter system (not shown) and into the patient (not shown). A beam impingement path is the pathway through the patient that is traveled by an antiproton beam to reach a target region. As previously discussed, the number of antiprotons delivered in a single, directed application is preferably measured by a beam monitor system positioned in the nozzle 935. In one embodiment, the beam monitoring system comprises two monitoring subsystems providing two independent beam flux measurements. The two monitoring subsystems are substantially similar to those described in relation to the gantry configuration. Similarly, other methods and systems can be used to monitor the beam. Once the target number of antiprotons has been delivered into a patient through a delivery point, the beam is switched off preferably using a fast kicker-magnet (not shown) located in the beam line 940. The fast kicker magnet and associated support structures are substantially similar to those described in relation to the gantry configuration. While a range shifter system and other additional devices can be used to control and contour the beam, as discussed in relation to the gantry configuration, in certain embodiments a beam is formed and delivered without the use of degraders or other devices to physically contour the beam. The inclusion of barriers, structures, or other materials within the beam line can cause the unwanted generation of particles, such as pions, neutrons and gamma rays, that will dose the patient without any beneficial medical purpose. To vary dosage levels, it is preferred to use a variable energy synchrotron whose energy level can be modified as needed to deliver antiprotons to the requisite depth. In both the gantry and fixed beam configurations, the patient table can be fixed or moveable. Where moveable, the patient table can be moved linearly along all three coordinate planes, x, y, and z, and rotationally across one or more coordinate planes, as needed. In one example embodiment, the patient table comprises an elongated rectangular bedding, preferably of sufficient firmness to maintain the patient on an even plane surface, that is affixed to a table frame that preferably has at least four legs connected, at their bases, to wheels. The frame is preferably a metallic structure capable of being tilted to modify the planar position of the bedding without requiring the concurrent repositioning of the patient. One of ordinary skill in the art will appreciate that numerous table designs can be with in various embodiments, including the one described by U.S. Pat. No. 6,152,599 incorporated herein by reference, without departing from the scope of the invention. As further discussed below, a plurality of variables are monitored and modified to insure that the proper dosage is being delivered to the proper area within the patient. The position and quantity of each dose is determined by the application of an antiproton treatment protocol and cancer diagnostic procedure pursuant to one example embodiment. Through the diagnosis and protocol procedures, dose distributions of various shapes, from uniform to complex, can be constructed and delivered by modifying the beam impingement path and location on the patient, the number of antiprotons delivered, and the energy of the antiprotons. The antiproton beam, as delivered, is rapidly focused on the target area using magnetic fields in the form of a highly directed pencil beam positioned in three-dimensional space to insure the dose distribution substantially matches the distribution determined theoretically by Bragg Peak calculations. In one embodiment, the gantry head can be rotated circumferentially relative to the patient to allow for the radial movement of the nozzle around the patient. The radial movement preferably covers a 180 degree arc above the patient table. Additionally, the patient table can preferably be rotated, both vertically and horizontally, to establish an appropriate beam delivery angle relative to the gantry head. In operation, singular doses can be delivered, through specific tissue pathways, and then terminated. If necessary, the gantry head and/or patient table can then be moved to position the patient for a subsequent exposure to an antiproton beam via a different tissue pathway. The patient table is preferably not repeatedly rotated in the course of a treatment to reposition a patient in order to avoid creating discomfort to the patient and because such table adjustments often use far greater time and technician assistance. Where a target volume is being treated for which multiple doses delivered adjacent to one another may be needed it is preferred to use a sweeper magnet to move the beam, thereby speeding up adjustment time and obtaining greater precision relative to mechanical reconfigurations. One example sweeper magnet is a 40 cm long H-type laminated magnet with a 5 cm pole gap having a vacuum pipe made of insulator material to avoid eddy effects. Using this type of sweeper effect, the beam spot can be moved by about 10 cm. The current in the coils can be chosen at any desired value, preferably in the range of +/−500 amps, which corresponds to a magnetic field range of +/−0.8 Tesla. The sweeper magnet is used to perform the most frequent displacements of the antiproton beam. For adjacent irradiations requiring only a small change of current in the sweeper magnet, the time required to switch the beam off and adjust position should be below about 5 ms. For example, where a treatment requires 10,000 adjacent spots delivered to a single target area, total dead time may be limited to under one minute. In another embodiment, the dose distributions of various shapes, from uniform to complex, can be constructed and delivered by transmitting a beam of antiprotons from a plurality of different delivery points fixed in space. Referring back to FIG. 9, a single isocenter 980, for example a tumor located in the brain of a patient, can be targeted via three different beam pathways using the three delivery points. Additionally, the patient table can be rotated, both vertically and horizontally, to establish an appropriate beam delivery angle relative to the delivery points. In operation, singular doses can be delivered, through specific tissue pathways, and then terminated. The patient table is preferably not repeatedly rotated in the course of a treatment. In certain antiproton device configurations, an operator workstation comprising a data processor, data storage device, and display is in data communication with the delivery synchrotron, magnets, and delivery structures, such as the motorized drive gears attached to the gantry head and/or to the base of the patient table. The workstation is programmed to implement the antiproton treatment protocol developed for the patient. An operator initiates the workstation and indicates, through an interface, that the patent is positioned in an initial reference position. By positioning the patient in an initial reference position, the workstation can be informed as to where the patient sits in space and, therefore, move the gantry head and/or patient table into the proper position relative to the patient, for delivering the antiproton beam. Several methods may be used for positioning, including, but not limited to those which follow. The initial reference position can be established, for example, by placing the patient in a specific position relative to the table utilizing spine implanted radio-opaque fiducials which may be implanted in the patient's spinal column permitting accurate repositioning of the patient to +/−1.7 mm. The initial reference position can also be established by placing the patient in a specific position relative to the patient table or by covering the patient with a sheet comprised of a grid of electronic contacts, each of said contacts being placed in a specific position relative to the patient's body. More specifically, in one embodiment, the grid of electronic contacts is interconnected by a conductive material and culminates in a single wire contact extending into a grid reader. The grid reader sends a signal into and through the contacts, receives responses from the contacts, reconstructs the grid structure in space, and transmits the grid configuration to the workstation. Operating on assumptions as to how that grid structure is positioned relative to the patient's body, the workstation can identify specific points on the patient's body. Beginning with the patient in an initial reference position, the workstation transmits a signal to the motorized drive gears of the gantry head and/or patient table informing the drive gears to move the gantry head and/or patient table into a specific position based upon the angle and path by which an initial antiproton dose will be delivered into the patient. Where a fixed beam line configuration is being used, only the patient table is manipulated to achieve a specific position based upon the angle and path by which an initial antiproton dose will be delivered into the patient. With the patient position positioned, the workstation transmits a signal to the beam monitor system informing it what amount of antiprotons are to be delivered and also transmits a signal to the range shifter system informing it of the dosage depth prior to activating the delivery synchrotron to accelerate (or decelerate) and deliver antiprotons of the desired energy level to the system. In one embodiment, the delivery system is activated and antiprotons are delivered to an appropriate depth and in an appropriate number, as measured and monitored by the range shifter and beam monitoring systems respectively. Preferably a plurality of procedures is used in parallel to monitor the quantity and depth of dose delivery. For example, a first procedure can comprise the workstation actively communicating scanning parameters to the ranger shifter and beam monitoring systems. Concurrently, a second procedure can be implemented in which the workstation passively monitors the activities of the ranger shifter and beam monitoring systems. Passive monitoring can be achieved by detecting the number and location of antiproton annihilations within the patient, as further discussed below, and deriving the associated energy level and number of antiprotons delivered. The data generated from the second procedure can be compared to the parameters of the first procedure to cross check the accuracy of the monitoring and shut down systems. If a discrepancy is identified, an automatic shutdown procedure can be effectuated, where the antiproton source is turned off, the fast kicker magnet is activated, and/or a solid beam shutter is deployed. In another embodiment, the workstation transmits a signal to the beam monitoring system informing it what amount of antiprotons are to be delivered and also transmits a signal to the delivery synchrotron to accelerate and deliver antiprotons at a specific, predefined energy level, thereby eliminating the need for degraders, range-shifters or other such mechanism that may generate unwanted particles, such as pions, neutrons and gamma rays. In one embodiment, the delivery system is activated and antiprotons are delivered to an appropriate depth and in an appropriate number, as measured and monitored by the beam monitoring system. Similar parallel procedures as discussed above can be used to monitor the quantity and depth of dose delivery. After the initial antiproton irradiation is completed, the parameters for the position of beam scan can be modified to enable the irradiation of an entire target area. Beam repositioning can be performed with the beam switched off. As previously discussed, beam repositioning can be effectuated by gantry head movement, table movement, or the use of a deflecting magnet (such as a sweeper magnet), depending on the antiproton delivery device being used. In a gantry configuration, to insure beam focus on the designated target area, referred to as the isocenter, the shape of the poles of the 90 degrees bending magnet and of the sweeper magnet can be designed to produce a displacement of the swept beam which is substantially exactly parallel to its direction and to maintain the focusing of the beam at the isocentric plane independently of the setting of the sweeper magnet. The shape of the scanned beam can be sweeper invariant. The precision of the beam is measured at better than 1 mm for beam parallelism during scanning (independent of sweeper position), change of beam shape during scanning (independent of sweeper position), isocenter stability (independent of gantry angle), and beam position reproducibility after a change of the beam energy. In addition to the above controls, for both the fixed beam and gantry configurations, certain embodiments additionally comprise a plurality of backup controls to shut down or otherwise block the undesired antiproton irradiation of a patient. Antiproton beams are automatically controlled by a fast kicker magnet. In case the kicker magnet fails to activate, another form of beam shut down should be immediately deployed, such as the switching off of the antiproton accelerator. Alternatively or in combination, a mechanical beam shutter can be used to block the patient from antiproton exposure. In one example embodiment of the antiproton gantry device, shown in FIG. 10a, the gantry 1050a is combined with a plurality of detectors 1060a that enable the imaging of certain patient tissue areas subjected to antiproton radiation. A patient (not shown) is positioned on a patient table 1065a. Antiproton beam 1070a enters gantry 1050a and is directed toward a target volume 1075a. As previously discussed, a plurality of different configurations can be used to direct beam 1070a toward volume 1075a, and the configuration shown in FIG. 10a is merely an exemplary embodiment. The detectors 1060a are arrayed in a configuration that avoids obstructing beam 1070a while concurrently exposing the detector array 1060a to antiproton annihilation emissions that can be used to conduct real-time imaging, as further discussed below. Similarly, in another example embodiment of the fixed beam device, shown in FIG. 10b, the fixed beam system 1050b can be combined with a plurality of detectors 1060b, 1062b that enable the imaging of certain patient tissue areas subjected to antiproton radiation. A patient (not shown) is positioned on a rotatable patient table 1065b. An antiproton beam line (not shown) enters gantry 1050b and is directed by action of a plurality of beam magnets toward a target volume 1075b. As previously discussed, a plurality of different configurations 1070b can be used to direct an incoming beam toward volume 1075b, and the configuration shown in FIG. 10b is merely an exemplary embodiment. The detectors 1060b, 1062b are arrayed in a substantially spherical upper detector configuration 1060b and substantially spherical lower detector configuration 1062b that avoids obstructing the plurality of beams 1070b while concurrently exposing the detector array 1060b, 1062b to antiproton annihilation emissions that can be used to conduct real-time imaging, as further discussed below. The detectors can be made of a high atomic number, high-density material capable of interacting with gamma rays to create an electromagnetic shower. The shower energy is substantially contained inside a volume, each having a radius of two times the Moliere radius and having a length of approximately 20 X0 radiation lengths. In one embodiment, the detector assembly is supported by a carriage, which can be rotated around the target axis running on a bent, nearly semicircular track. The detector may also be moved radially by a screw arrangement to a specified range of distance from the target to the crystal face. In specialized high-energy physics experimentation, energetic charged particles and gamma rays, which are produced when an antiproton annihilates at rest on a proton and which then move radially away from that annihilation site, are detected and tracked back to a common point, referred to as the vertex. The process of tracking the energetic charged particles and gamma rays back to their common point of origination is referred to as vertex reconstruction. To effectively perform vertex reconstruction, the detectors used can be designed to detect particles and/or radiation that have the highest likelihood of escaping a patient's body with the least amount of scattering or other perturbations that can complicate determinations of where the particle and/or radiation had originated. Assuming an antiproton beam penetrates and stops at the center of a sphere of water having a 15 centimeter (cm) radius and annihilates, only those particles having energy greater than given by the stopping range of 15 cm of water will escape the sphere and be capable of being detected. Relative to charged kaons, neutral kaons (short), and neutral kaons (long), muons and charged pions have the highest probability of escaping the 15 cm sphere. Neutral pions decay in less than 0.025 microns from the point of annihilation into a pair of gamma rays that escape with energy carried by the pion. Charged pions escaping material undergo substantial amounts of scattering, thereby increasing the complexity of vertex reconstruction. When being emitted out of 15 cm of water, charged pions having momenta less than about 160 MeV/c stop in the water and are not detected, while charged pions having momenta in excess of about 150 MeV/c scatter laterally, relative to the direction of the linearly formed track, by a root mean square of approximately 7 millimeters. The change of direction is dependent upon the particle's momentum, the particle's charge, and the material through which the particle is passing. Although lateral displacement improves as particle momentum increases, even at the higher momenta, pion lateral scattering is at or around 1.5 mm, thereby limiting imaging precision to plus or minus 1.5 mm. This limitation decreases as the site of annihilation approaches the surface. In one example embodiment, vertex reconstruction is performed using neutral pion decay gamma radiation. Unlike charged pions, gamma rays have a high probability of escaping a material body without undergoing substantial interactions which cause scattering and skew vertex reconstruction calculations. Further, the pair of gamma rays emitted can be traced back to the point where the neutral pion decayed and, because neutral pions decay within 0.025 microns of the annihilation point, can provide a more accurate representation of where the annihilation occurred. In a typical annihilation event, the mean number of gammas emitted for each antiproton annihilation event is four (two for each neutral pion), and can be as high as 10. Operationally, vertex reconstruction is performed by relying on the detection of multiple points along the shower axis and the use of those multiple points to generate a vector localizing a common origination area. It can be preferred that any heavy inorganic scintillators used to detect gamma rays have one or more of certain desired characteristics, including, high stopping power to maximize the probability of complete absorption of the incident energy, high timing resolution, high energy resolution, minimum dead time, wavelengths of emission that match with the spectral response of the photodetectors, mechanical ruggedness, radiation hardness, chemical stability in normal atmospheric conditions, and reasonable cost. Existing heavy scintillators meet certain of these criteria, including high luminous efficiency measured in photons/MeV (NaI(TI) and CsI(TI)), high density/high atomic number (BGO), short Moliere radius (BGO and CeF3), high initial photon intensity measured in photons/MeV/ns with high timing resolution (BaF2), and high luminous efficiency and wavelength suitable for silicon photodiodes (CsI(TI) and CdWO4). Proper selection of a detector provides for a further benefit of gamma ray shower detection over charged particle detection is speed. Shower detection can be done using a fast scintillator, less than 15 nanoseconds, thereby allowing a faster response than charged particle tracking. Tungsten (W), sodium iodide doped with thallium (NaI(TI)), and lead tungstate (PbWO4) are three materials that can be used for shower detection. Sodium iodide activated by thallium is a well-known material used for scintillation applications. NaI(TI) has a high luminescence efficiency and spectroscopic performance with minimal significant self absorption of the scintillated light. Lead tungstate is a highly efficient and fast scintillator with one of the shortest radiation lengths and Moliere radii among the known scintillators, satisfactory light yield for this energy range, and high radiation stability. Radiation lengths for NaI(TI), CsI(Ti), PbWO4, BGO, Tungsten (W), and Iridium (Ir) are 2.59 cm, 1.86 cm, 0.89 cm, 1.12 cm, 0.323 cm, and 0.27 cm, respectively. The Moliere Radius for NaI(TI), PbWO4, and W are 4.5 cm, 2.2 cm, and 0.8 cm respectively. The density for NaI(TI), CsI(TI), PbWO4, BGO, Tungsten (W), and Iridium (Ir) are 3.67, 4.53, 8.28, 7.13, 19.4, and 22.4, respectively. The decay time for NaI(TI) is 250 ns while for PbWO4 it is between 5 and 15 ns. For BGO and CsI(TI), the decay times are 300 ns and 0.9/7.0 μS. The light output for NaI(TI), CsI(TI), PbWO4, and BGO are 1.0, 0.85, 0.01, and 0.15, respectively. Another material usable for the present application includes uranium, which has the requisite Moliere radius and material density. However, because it is not actively sensitive to the shower, it will have to be combined with an active scintillator. Using layers of tungsten, for example, in combination with uranium can provide a satisfactory detector device. When using tungsten, one can employ the sensing element in a matrix, such as a 3.23×3.23×3.23 mm3 matrix, or in a crossed 3.23×3.23×200 mm3 hodoscope plastic scintillator to sample the shower's charged particles passing between sandwich plates. Locating the vertex with a precision on the order of 500 microns is possible using these techniques. When using lead tungstate, one can use a 9×9×9 mm3 matrix or a crossed 9×9×200 mm3 hodoscope sensor array. The radiation length of lead tungstate is 2.7 times greater than tungsten. Although the chosen approach is dependent upon a plurality of technical, as well as economic considerations, one consideration favoring the smaller shower localization of tungsten over lead tungstate is its ability to separate the gamma pair of the neutral pion decay. As the momenta of neutral pions increase, lead tungstate loses efficiency at separating decay gammas relative to a tungsten shower detector. The detectors can be surrounded by a shielding structure to isolate the detectors from the surrounding environment. In one implementation, NaI(TI) crystals are surrounded by an active plastic shield, a passive LiH shield, and a low activity thick lead shield which, in combination, have a cosmic rejection efficiency around 98%. Further, the detectors can be supported by a carriage structure to enable efficient rotation around a target axis. Referring to FIGS. 10c through 10r, a plurality of detector configurations is shown particular to each calorimeter imager material used. Imagers for NaI and BGO are not shown because NaI is similar to CsI and BGO is similar to PbWO4. FIGS. 10c and 10d show example detector configurations for brain imaging using PbWO4 as the calorimeter imager material. In FIGS. 10c and 10d, a beam pipe 1083d delivers an antiproton beam to a predesignated area within the patient's brain 1085d. The beam direction and imager 1086d are fixed relative to each other. The patient is positioned on a table 1084d. In use, a patient will first be positioned between detector elements, as shown in FIGS. 10a and 10b, and then the elements are assembled into a portion of a spherical shell sharing the center with the annihilation region, appropriately accounting for straggling and multiple straggling limits. Sufficient resolution can be achieved by having the calorimeter elements point approximately to the annihilation site. When annihilation occurs, a plurality of gamma rays 1087d are emitted, due to the decay of neutral pions generated in the course of the annihilation, which extend from the target region 1085d with an opening angle of approximately 30 degrees taken from the point of annihilation. The gamma radiation may have an opening angle less than 30 degrees, but not more than 30 degrees relative to each other. In one embodiment, the imager length (20 radiation lengths) is 17.8 cm. The inner radius size is 0.89 cm×0.89 cm with the outer radius size being 1.8 cm×1.8 cm. The maximum mass is approximately 1556 kg. FIGS. 10g and 10h, 10k and 10l, and 10o and 10p show a similar detector configuration using CsI(TI), Ir, and W as calorimeter elements, respectively. A beam pipe 1083h, 1083l, 1083p delivers an antiproton beam to a predesignated area within the patient's brain 1085h, 1085l, 1085p. The beam direction and imager 1086h, 1086l, 1086p are fixed relative to each other at least during detection. The patient is positioned on a table 1084h, 1084l, 1084p. In use, a patient will first be positioned between detector elements, as shown in FIGS. 10a and 10b, and then the elements assembled into a portion of a spherical shell sharing the center with the annihilation region, appropriately accounting for straggling and multiple straggling limits. Sufficient resolution can be achieved by having the calorimeter elements point approximately to the annihilation site. When annihilation occurs, a plurality of gamma rays 1087h, 1087l, 1087p are emitted, due to the decay of neutral pions generated in the course of the annihilation, which extend from the target region 1085h, 1085l, 1085p with an opening angle of approximately 30 degrees taken from the point of annihilation. The gamma radiation may have an opening angle less than 30 degrees, but not more than 30 degrees relative to each other. In one embodiment, or CsI(TI), the imager length (20 radiation lengths) is 37.2 cm, the inner radius size is 1.86 cm×1.86 cm, the outer radius size is 5.7 cm×5.7 cm and the maximum mass is approximately 3172 kg; for Ir, the imager length (20 radiation lengths) is 10.8 cm, the inner radius size is 2.7 cm×2.7 cm, and the maximum mass is approximately 1073 kg; for W, the imager length (20 radiation lengths) is 12.92 cm, the inner radius size is 0.32 cm×0.32 cm, the outer radius size is 5.7 cm×5.7 cm, and the maximum mass is approximately 1137 kg; and for BGO (not shown), the imager length (20 radiation lengths) is 22.4 cm and the inner radius size is 1.12 cm×1.12 cm. For non scintillators, such as Ir and W, preferably approximately 50% of the space in the length is dedicated to a plastic scintillator read out of the shower in a hodoscope's geometry. FIGS. 10e and 10f show detector configurations for torso imaging using PbWO4 as the calorimeter imager material. A beam pipe 1083f delivers an antiproton beam to a predesignated area within the patient's torso 1085f. The beam direction and imager 1086f can be fixed relative to each other. The patient is positioned on a table 1084f. As previously stated, in use, a patient will first be positioned between detector elements, as shown in FIGS. 10a and 10b, and then the elements are assembled into a portion of a spherical shell sharing the center with the annihilation region, appropriately accounting for straggling and multiple straggling limits. Sufficient resolution may be achieved when the calorimeter elements point approximately to the annihilation site. When annihilation occurs, a plurality of gamma rays 1087f are emitted, due to the decay of neutral pions generated in the course of the annihilation, which extend from the target region 1085f with an opening angle of approximately 30 degrees taken from the point of annihilation. The gamma radiation may have an opening angle less than 30 degrees, but not more than 30 degrees relative to each other. In one embodiment, the imager length (20 radiation lengths) is 17.8 cm, the inner radius size is 0.89 cm×0.89 cm, the outer radius size is 1.8 cm×1.8 cm, and the maximum mass is approximately 3618 kg. FIGS. 10i and 10j, 10m and 10n, and 10q and 10r show a similar detector configuration using CsI(TI), Ir, and W as calorimeter elements, respectively. A beam pipe 1083j, 1083n, 1083r delivers an antiproton beam to a predesignated area within the patient's torso 1085j, 1085n, 1085r. The beam direction and imager 1086j, 1086n, 1086r are fixed relative to each other. The patient is positioned on a table 1084j, 1084n, 1084r. In use, a patient will first be positioned between detector elements, as shown in FIGS. 10a and 10b, and then the elements are assembled into a portion of a spherical shell sharing the center with the annihilation region, appropriately accounting for straggling and multiple straggling limits. Sufficient resolution may be achieved when the calorimeter elements point approximately to the annihilation site. When annihilation occurs, a plurality of gamma rays 1087j, 1087n, 1087r are emitted, due to the decay of neutral pions generated in the course of the annihilation, which extend from the target region 1085j, 1085n, 1085r with an opening angle of approximately 30 degrees taken from the point of annihilation. The gamma radiation may have an opening angle less than 30 degrees, but not more than 30 degrees relative to each other. In one embodiment for CsI(TI), the imager length (20 radiation lengths) is 37.2 cm, the inner radius size is 1.86 cm×1.86 cm, the outer radius size is 3.8 cm×3.8 cm and the maximum mass is approximately 6328 kg; for Ir, the imager length (20 radiation lengths) is 10.8 cm, the inner radius size is 2.7 cm×2.7 cm, and the maximum mass is approximately 2500 kg; for W, the imager length (20 radiation lengths) is 12.92 cm, the inner radius size is 0.32 cm×0.32 cm, and the maximum mass is approximately 2618 kg. For non scintillators, such as Ir and W, approximately 50% of the space in the length is dedicated to a plastic scintillator read out of the shower in a hodoscope's geometry. With respect to performance, the angular acceptance achieved in the crystal barrel spectrometer is approximately 6 degrees (100 mrad). Without adjacent cell interpolation, the calorimeter imager materials, operating in the aforementioned brain imager and torso imager configurations, have the following degrees of angular acceptance: for brain imager configurations, the angular acceptance of CsI(TI), PbWO4, BGO, W, and Ir is 103 mrad, 49 mrad, 62 mrad, 18 mrad, and 15 mrad respectively. For torso imager configurations, the angular acceptance of CsI(TI), PbWO4, BGO, W, and Ir is 53 mrad, 25 mrad, 32 mrad, 9.2 mrad, and 7.2 mrad respectively. If interpolation is implemented, a 300% gain in resolution may be achieved for certain calorimeter imager materials operating in certain configurations, upwards of a 1000% gain in resolution for materials such as PbWO4. The highest angular resolution can be achieved with W or Ir, although Ir may be expensive to use. 3. Diagnosis and Treatment Strategy Cancer is diagnosed using a variety of methods, a few of which are discussed herein. A patient suspected to have cancer maybe imaged using x-ray, CT, MRI, radioactively labeled tracer uptake, thermography, ultra sound and PET scanning. A medical practitioner skilled in the art of cancer diagnosis will understand how to use these technologies to yield an image that can indicate the presence of an unusual mass, and possibly, cancer. In one example embodiment, a patient is treated in a medical facility in which antiproton radiation therapy can be delivered. A schematic plan layout of an exemplary medical facility is provided in FIG. 11. The exemplary medical facility 1100 comprises a plurality of areas dedicated to standard medical facility functions, including examination rooms, maintenance areas, reception areas, waiting rooms, janitorial rooms, utilities, staircases 1187, elevators 1180, a lobby 1190, and staff areas, such as staff offices, meeting rooms, lunch areas, patient record keeping. Sizeable rooms internal to the facility 1185 are used for staff offices and/or examination rooms, rooms adjacent to the treatment area 1160 are used for patient preparation and changing, larger rooms 1170 are used for meeting or waiting areas, the smaller rooms 1175 are used for utilities or janitorial purposes, and the other rooms 1165 are used for storing patient records, secretarial functions, lunch rooms, smaller staff offices, and at least one dosimetry room and health physics room. The illustrated medical facility 1100 further comprises areas specialized for the delivery of antiproton therapy. A plurality of treatment rooms 1103 surrounded by heavy shielding 1135 is located in the back of the facility 1100. A control room 1130 is integrally provided with each treatment room 1103. In one room 1003 a MRI 1145 is provided proximate to a CT simulator 1155. In a set of second rooms 1103, a patient table 1120 is situated proximate to a delivery point 1115 integrally attached to a delivery device, such as a fixed beam or gantry device. Additionally, a treatment chair 1140 and an array of detectors (not shown) can also be situated proximate to the delivery point 1115 and patient table 1120. In a third room 1103, a calibration system 1125 is provided that enables an operator to calibrate the operation of the beam transport system 1105 and delivery synchrotron (not shown). Operationally, an antiproton beam is caused to travel through the beam transport system 1105 and bend by force of a plurality of bending magnets 1110, which are housed in a support structure. Depending upon a centralized schedule of operation, one of the plurality of beam lines directed into specific treatment rooms 1103 will be active and delivering a predesignated dose of antiprotons to a patient 1124 positioned on a patent table 1120. Antiprotons traveling through the beam transport 1105 will be directed into the appropriate beam pipe that feeds a particular treatment room 1103. The beam pipe as shown terminates in a gantry or vertical/horizontal beamline. Referring to FIG. 11a, an exemplary beam line 1105a integrated with a medical facility 1100a is shown in the context of delivering an antiproton beam to a fixed beam antiproton delivery device. Two fixed beams 1125a are generated, focused on a target volume 1130a, by action of a plurality of bending magnets selectively bending antiprotons traveling through a beam pipe 1140a. A person familiar with high-energy physics will understand how to produce, collect, cool, decelerate and extract antiprotons through the application of vacuums pumps, magnets, radiofrequency cavities, high voltage instruments and electronic circuits. Antiprotons circulate inside vacuum pipes in order to avoid contact with matter with which they annihilate. The vacuum should be optimal, therefore several vacuum pumps, which extract air, are placed around the pipe. The magnets used include dipoles, which serve to change the direction of antiproton movement and insure they stay within the circular track, and quadrupoles, which are used as lenses or focusing magnets to insure that antiproton beam size is smaller than the vacuum pipe size. Electric fields are used to modify antiproton energy levels and are provided for by radiofrequency cavities that produce high voltages synchronized with the rotation of antiprotons around the ring. While the medical facility 1100, 1100a has been described in relation to a specific design and layout, one of ordinary skill in the art will appreciate that other space configurations can be used, depending upon the particular conditions of the location and the needs of the facility. A patient is positioned in a diagnosis area that can have one of, or a combination of, several diagnostic devices. One diagnostic device can include a magnetic resonance imaging (MRI) scan in which a patient is subjected to an external, uniform magnetic field and radiofrequency energy that excites protons in the patient's body and subsequently produces signals with amplitudes dependent on relaxation characteristics and spin density. Abnormalities can be detected by identifying unusual signals that indicate a particular region has a different proton density than normally expected. Another diagnostic device that can reveal tissue structure and therefore identify unusual masses is computer tomography (CT) scanning. CT scans are performed by passing x-rays through a patient, at a large number of angles, by rotating the x-ray source around the patient. A plurality of detector arrays, located opposite the x-ray source, collect the transmission projection data in the form of various data points. The data points are synthesized into a tomographic image, or imaged slice, of a patient. The variation in transmission data is indicative of tissue density and can be used to identify unusual masses-in the body. A third possible diagnostic device is a positron emission tomography (PET) scan in which the patient is administered, through an intravenous injection, a positron-emitting radioactive substance comprising a form of glucose that reacts with tissues in the body, in proportion to metabolic activity. By measuring the different amounts of positrons released by healthy and cancerous tissues, a computer creates an image reflective of the biological activity occurring within the patient. Because cells from many cancers have a higher affinity for certain positron-emitting radioactive substances, such as F18 labeled glucose, the tumor area may be imaged. PET scans can be combined with x-ray based scans and MRI scans to confirm that an unusual structure may, in fact, be cancerous. More specifically, PET scans can be overlaid onto, or combined with, MRI or CT images to generate an integrated image that shows tissue structure associated with metabolic activity. Output from one or more of the aforementioned diagnostic devices can be used by a medical practitioner, including technicians, nurses, radiologists, oncologists, and other medical professionals, to determine whether the patient has cancer and, if so, the location, extent, and stage of the cancer. In one example embodiment, shown in FIG. 12, at least one of the diagnostic scans from the PET scan 1305, MRI scan 1310, and/or CT scan 1315, is stored in an operator workstation 1320, transmitted to an antiproton treatment protocol station 1325, and used to assist in the development of an antiproton based treatment regimen. Alternatively, only the data representing key treatment parameters may be transmitted to the antiproton treatment protocol station. Referring back to FIG. 11, the patient, once imaged, is taken to an antiproton treatment protocol station. The station can be co-located with the diagnostic machinery, placed in a separate office within the same building, or located in a completely separate facility. The schematic representation in FIG. 11 is provided for example purposes only. Having identified and quantified the tumor location, a treatment protocol using antiproton radiation is developed. In one example approach, data representing the tumor size and location is transmitted from imaging technologies, as previously described, to an antiproton treatment protocol station. The treatment protocol station applies a set of analyses to determine the amount of antiprotons, antiproton energy sufficient for treatment, and preferred delivery pathways and communicates that protocol to an antiproton radiating and imaging station, as previously described. The antiproton treatment protocol station is in data communication with the imaging station used or, alternatively, is capable of receiving data stored on media, such as a disk or CD-ROM. In one embodiment, shown FIG. 12, the treatment protocol station comprises a display 1350, print-out device 1355 storage device 1360, modem or network control card 1365, and processor 1370 capable of communicating with the display (any type of monitor), print out device (any type of printer), storage device, and modem/network controller and of implementing a plurality of instruction sets for determining the amount of antiprotons, antiproton energy sufficient for treatment, and preferred delivery pathways given a tumor size and location. The amount of antiproton radiation needed to terminate a mass is calculated, along with the amount of energy needed to deliver an antiproton to the mass depth. Using equations to determine the amount of energy deposited in collateral tissue and the residual energy plus annihilation event radiation effects, such as caused by the emission of particles like alpha particles, the energy deposited in the mass, along with the lateral spreads and Bragg Peak contours, can be determined. Once done, an energy deposition profile can be generated that covers the entire mass with sufficient antiproton induced radiation by summing multiple Bragg Peaks, assuming a plurality of spot scans performed at varying depths within the tumor region. The amount and energy level of antiprotons, for each location to be irradiated, defines the protocol, which is then sent to the antiproton radiation and imaging device, as previously discussed. During operation, a beam monitoring system and range shifter or a delivery synchrotron can be used to measure the actual dosage being delivered to insure it correlates with the desired calculated dosage. To the extent a range shifter is used, antiproton losses, caused by the degradation process, need to be calculated and incorporated into all beam monitoring calculations to insure accurate determination of actual antiprotons delivered to the patient. As an example, a patient is diagnosed with a 1 cubic centimeter (cc) tumor located 10 centimeters below the skin surface. The diagnosis occurs through a combination of MRI and PET scans, which indicates a mass having a high metabolic rate in the patient's chest cavity. Using the location and tumor size data, the amount of antiprotons to be used to annihilate the target region is determined. One example method of determining the amount of antiprotons needed is by assuming the density of tissue to be around 1 gram per cc, assuming 500 rads will be sufficient to terminate the cancerous cells, and equating the relative biological effect (RBE) of antiproton radiation in the target volume to that of heavy ions having a 30 MeV recoil (RBE=5). This reflects the fact that at least one 30 MeV recoil heavy ion is produced for each antiproton annihilation event. Because 500 rads is approximately equivalent to 30×109 MeV per gram, the total number of antiprotons needed to deliver 500 rads is 109. It should be noted that, if the RBE of the chosen radiation were lower, as with photons, a greater amount of radiation, as measured in rads, will have to be delivered to the same target region in order to terminate the cancerous cells. For example, photon radiation has a RBE of 1, thereby requiring 2500 rads to have the same cell terminating effect as antiprotons, which, when equated to heavy ions, has a RBE of 5. To determine the amount of energy 109 antiprotons should have in order to reach 10 cm below a surface, one can use a TRIM calculation, as found in Zeigler J. F., Biersack J. P., and Littmark U., “Stopping and Range of Ions in Solids,”, Vol. 1, 1985 (Pergamon Press, NY). Applying a TRIM calculation demonstrates that an antiproton beam energy of approximately 108 MeV will achieve an end-of-range position that is 10 cm below the surface in a patient. Given that, like protons, antiprotons are low linear energy transfer particles and that only a small portion of antiprotons annihilate prior to reaching the target region, approximately 30 MeV of the 108 MeV is deposited in the target region, while 78 MeV is deposited in collateral tissue. Assuming the volume of collateral tissue between the skin and target area is 9 cc (1 cm×1 cm×9 cm), the damage inflicted by traveling antiprotons can be defined by a RBE of 1.2 (20% greater than protons), and damage is uniformly spread across the collateral tissue, the collateral damage is equal to approximately 168 rads ((1.2×78 MeV/antiproton×109 antiprotons)/9 cc), which is tolerable and therefore does not require a multiple pathway dosage profile (although it may be done if desired). Therefore, combined the protocol produces a recommended treatment plan: one exposure of 109 antiprotons having an energy of 108 MeV. In dealing with tumors having a volume greater than 1 cc, multiple doses, spread across a region, can be preferred to minimize collateral tissue damage in any single location. For example, some lung and prostate cancers are intermediate sized tumors and can range, on average, around 150 cc and 35 cc with average surface depths of 12 and 6 cm, respectively. Head and neck tumors may be irregularly shaped and in some embodiments, multiple doses may be utilized to cover the target region. In either case, the high degree of localization provided by antiproton radiation therapy can allow for one or more of the following: (1) the termination of cancer cells with minimal fractionation requirements; (2) producing tumor cell injury by causing numerous double strand DNA breaks and by inducing cell membrane injury of trans-membranal surface proteins, i.e. by interfering with EGFR (epidermal growth factor receptor) and VEGF (vascular endothelial growth factor receptor) transduction signaling; (3) sparing injury to tumor-adjacent antigen serving macrophage dendritic cells, which facilitate tumor lysis by T-cells in the tumor microenvironment; (4) avoiding injury in the tumor microenvironment to lymphokine activated killer (LAK) T-cells, which become effector cells causing tumor lysis when served with tumor antigens by dendritic cells, an important immunologic activity in facilitating the body's natural defenses against tumor growth; (5) permitting the progeny of tumor sensitized effector LAK T-cells to provide cell lysis of distant microscopic tumor metastatic implants; and (6) causing less hematopoietic injury, which is common in photon regimens, since the bone marrow will be spared the effects of radiation exit dose and dose fall off. This is of particular importance with the increasing use of simultaneous chemotherapy-photon radiation therapy protocols in a variety of cancers, which often lead to blood count depressions that necessitate interruption of treatment. The highly conformal nature of antiproton radiation will avoid this adverse result. In one example embodiment, the treatment protocol station will have a computer-implemented software program capable of taking the requisite input data, namely tumor size and location, and, as shown in FIG. 13, outputting impact graphs superimposed on the scanned images of the patient's tumor, as generated from conventional therapies. A tumor body 1305 is identified and located relative to a patient's anatomy. The tumor body 1305 is positioned in an area within the patient's brain 1310. A plurality of delineated antiproton dosage regions 1315 are defined relative to the tumor body 1305. The dose regions 1315 can be defined in numerous ways, including by percent dosage relative to calculated dose requirements or by absolute dosage amounts, with higher dose regions generally being centered within the plurality of dose regions 1315 and lower dose regions extending to the periphery. It should be noted that, because of the ability to precisely deliver high amounts of energy into an area without high accompanying collateral damage, a medical practitioner does not need to cover an entire mass with antiproton radiation, but rather, can selectively target highly sensitive areas within a tumor volume to achieve tumor mass destruction with minimal radiation. For example, because tumors rely on fragile blood vessel networks to fuel their rapid growth, it may be possible to kill an entire tumor mass through the directed application of antiproton radiation on areas responsible for providing primary blood supply. By irradiating critical blood vessels one can induce angiolysis, thereby shutting down essential blood supply to a tumor. Similarly, tumors may be killed using antiproton radiation by causing blood vessel swelling such as in AVM's (arteriovenous malformations) which will result in the eventual cut off of a tumor's blood supply. Tumors may also be killed by biologically isolating them through the application of antiproton radiation circumferentially and sparing normal structures interior to the tumor, such as the urethra coursing through a malignant prostate gland. Circumferential antiproton radiation may also induce fibrosis around a tumor mass isolating the tumor and causing it to necrose. It should further be noted that a substantial number of repeated treatments is not required. Treatment fractionation is required in conventional therapies because of the inability to drive high enough radiation levels to target tissue without causing high collateral damage. Lower target radiation levels, though sufficient to kill dividing cells, are not sufficient to kill resting cells. As a result, multiple treatments have to be applied in order to kill the target cancer cells, and because of the rapid dividing nature of cancer cells, they are more impacted than the collateral cells which have time to repair after radiation exposure. The systems and methods disclosed herein enable the delivery of high radiation levels in target tissue, thereby killing both resting and dividing cancer cells, without causing unacceptable levels of damage to healthy tissue. Optionally, a patient may also be imaged using a PET scan after the antiproton radiation exposure is completed. Typically, to perform PET scanning, a patient is administered a glucose-tagged radioactive substance that decays inside the body and, in the process, releases positrons which, when detected, can be used to generate an image. Conventional PET scans are limited by the need to have the patient, PET imaging station, and radioactive isotope source (the radiopharmaceutical of appropriate activity) all proximate to each other. Specifically, PET applications rely on the use of biologically active radiopharmaceuticals where radioactive isotopes in the radiopharmaceutical emit positrons. These isotopes are typically generated through the use of synchrotrons, such as the RDS cyclotron, manufactured by Siemens, which is a frequently used PET device. It incorporates a computer terminal to control the flow of production, and a biosynthesizer unit to carry out the chemical synthesis of radiopharmaceuticals. Using the synchrotron, a stream of charged particles, such as protons or deuterons, bombard a collection of stable, sometimes enriched, isotopes and interact with a subset of those isotopes. Three nuclear reactions are commonly used for the production of C-11 and F-18, the most common PET isotopes. These reactions are: 14N(p,α)11C, in which the interaction of 14N with a proton is then followed by the emission of an alpha particle, resulting in 11C, 18O(p,n)18F, in which the interaction of 18O with a proton is then followed by the emission of a neutron, resulting in 18F, and 20Ne(d, α)18F, in which the interaction of 20Ne with a deuteron is then followed by the emission of an alpha particle, resulting in 18F. Radiopharmaceuticals, made from these radioactive isotopes, are then introduced into a patient's body where the decay of the isotope is monitored. While many radioactive isotopes can be produced in the cyclotron, the isotopes produced are preferably amenable to human PET use and, therefore; (1) are capable of emitting positrons when they undergo radioactive decay and transform from an unstable isotope into a stable one. (2) Because such isotopes tend to emit positrons relatively quickly, the isotope half-life is preferably long enough to allow for a patient to be administered the substance and placed in a position to be scanned. Furthermore, it can be preferred that the isotopes are readily incorporated into a useful radio-pharmaceutical by chemical synthesis. The most commonly generated isotopes include carbon-11 (half-life 20 minutes), nitrogen-13 (half-life 10 minutes), oxygen-15 (half-life 2 minutes), and fluorine-18 (half-life 110 minutes). Because of these short half-lives, some PET installations have cyclotrons proximate to the PET machine. For example, at the University of Iowa, a compact medical cyclotron is used to generate high energy protons or deuterons by forcing the particles to traverse the cyclotron several hundred times and, during each orbit, receive about 90 keV of energy. When the energies are high enough, the particles are removed through electrostatic deflection and are made to impinge upon small volume hollow metallic cylinders filled with a non-radioactive gas or liquid, causing nuclear reactions to take place within the cylinder and generating the appropriate isotopes. For certain applications, some of the systems and methods disclosed herein complement the use of PET-specific cyclotron and biosynthesizing stations to perform a PET scan. Conventional PET systems are used to measure and study biological functions, such as glucose uptake. In one embodiment, PET administration is used in combination with certain systems and methods disclosed herein to conduct PET scans. A patient is administered a PET-isotope labeled glucose molecule in order to identify enhanced glucose uptake areas in the body. The detector array incorporated into the antiproton delivery device can be used to monitor resulting decay, thereby repurposing detectors used for antiproton annihilation tracking and measurement for PET scanning. When treating with antiprotons, a medical practitioner can then directly compare PET scanning results with antiproton treatment results. One of ordinary skill in the art will appreciate that, in addition to the aforementioned characteristics, the antiproton delivery detector system for this embodiment should be sufficiently sensitive to differentiate between the decay generated by increased uptake areas of the radiopharmaceutical and the decay generated by the general uptake of the radiopharmaceutical throughout the body. Additionally, in one example embodiment the in-situ generation of PET isotopes is enabled. The exposure of human tissue to antiproton radiation generates a plurality of unstable isotopes, including, for example, oxygen-15, that are radioactive and emit a positron as a decay product. More specifically, when introduced into a target region, antiproton interactions generate oxygen-15, nitrogen-13, and carbon-11 as by-products. After the appropriate period of time (depending on the half life of the isotope), the generated isotopes decay, emitting positrons. The positrons travel a short distance in the target area before striking an electron. When this collision occurs, two gamma rays are simultaneously produced and travel away from each other at 180 degrees, toward the detector assembly already present for tracking gamma radiation generated from neutral pion decay. Each time two detectors detect a gamma ray simultaneously, the annihilation is recorded and the vertex, or point of gamma production, is determined. One of ordinary skill in the art will appreciate that, by reconstructing the location of the plurality of vertices, one can determine where the highest concentrations of isotope generation occurred, where the highest concentrations of tissue existed, and, by extrapolation, where cancerous tissue was located, assuming correlations between isotope generation, tissue density and cancerous tissue. Further, because those radioactive by-products are generated through antiproton annihilations in the region of interest, they better image only the region of interest. A difference between conventional PET imaging and the PET imaging aspect of the embodiments disclosed herein is that the conventional PET image reveals regions of enhanced glucose uptake, whereas the image in embodiment disclosed herein reveals a region where antiproton annihilations have occurred. Conventional PET scanning is dependent upon the uptake, by tissue, of radioactively tagged glucose, which may or may not be confined to a particular region of interest. As a result, a substantial amount of gamma radiation is emitted by positron-electron annihilations that are outside the region of interest and the result of the uptake of tagged glucose by healthy tissue elsewhere in the patient. These various emissions represent noise in the form of an undesired background signal relative to the gamma emissions from the areas of interest. In one example embodiment, the signal to noise ratio is greatly enhanced by the elimination of extraneous radiation emissions from areas outside the target region. It should be noted, however, that the intrinsic resolution of the conventional PET image and the resolution of the PET image produced by the embodiments disclosed herein are similar and that both images are degraded in absolute resolution due to diffusion and migration of the PET isotopes in tissue before the radioactive decay occurs that emits the positrons. Another advantage of the PET imaging aspect of embodiments disclosed herein is that standard PET cameras can be used to collect the image and the same detectors used for conventional PET imaging can be used to detect antiproton-generated PET. As the radioactive decay of the PET isotope does not occur promptly with respect to the antiproton annihilations, computer modeling of the diffusion and migration of the PET isotopes in tissue should be done in order to reconstruct where the annihilation took place. A higher resolution image, relative to PET images, is obtainable by imaging the higher-energy gamma ray emissions that are associated with the decay of the neutral pions that are created in the antiproton annihilation event, as the neutral pions decay nearly instantaneously after the neutral pion is created. It should be noted that, as previously discussed, the detection of the gamma rays from neutral pion decays generally uses a different type of detector than the gamma ray detectors used in a standard PET camera. In another aspect, the use of the low background noise characteristic of antiproton-produced radioisotopes, coupled with the short half lives of the radioisotopes, to image flow and/or diffusion characteristics within vessels or through tissue is enabled. Antiproton annihilations in blood or other fluids create short-lived radioisotopes within the blood or fluids. The most common radioisotopes that are produced in human fluids are 11C, 13N, and 15O, which have half lives of 20, 10, and 2 minutes, respectively. Circulatory blockages or hemorrhages can be imaged using standard PET imaging equipment to follow the diffusion of small volumes of blood or fluid that is initially irradiated with a low-intensity, highly localized pulse of antiprotons. A low-intensity pulse of antiprotons creates a small volume of radioisotopes that will flow with the blood or fluid in the local region. The path of the flow is readily imaged from the emitted radiation because the background intensity is negligible, as described above, and the resulting signal-to-noise is high. The short half lives of the radioisotope species result in large signals relative to background levels for ease of detection and short total lifetimes for low residual effects. 4. A Bi-Polar Accelerator System Referring back at FIG. 7, delivery pipe 1005 is configured to deliver an anti-proton beam to the anti-proton radiating and imaging device illustrated in FIG. 7. Often, as described above, a periodic accelerator is used to accelerate the anti-proton beam for delivery to the anti-proton radiating and imaging device via delivery pipe 1005. For example, a periodic accelerator such as a cyclotron, synchrotron, synchrocyclotron, or a Fixed-Field Alternating Gradient (FFAG), accelerator can be used to accelerate an anti-proton beam for delivery to the radiating and imaging device illustrated in FIG. 7. Linear accelerators such as Linacs, Radio Frequency Quadrupoles (RFQs) and pulse-forming systems using Blumlein Technology to repetitively form an electrostatic accelerating potential, e.g., a dielectric wall accelerator, can also be used for the same purpose. The same type of accelerators can also be used to accelerate protons for delivery to a proton radiating and imaging device. Existing accelerator systems, however, are designed to accelerate positively charged ions in one direction in the accelerator system and negatively charged ions in the opposite direction to the accelerator system. In other words, conventional accelerators are not capable of accelerating both negative and positive ions in the same direction. For example, accelerator systems have been built and used to create, cool, and store anti-particles, such as anti-protons. Such systems are included in large physics facilities in Europe (CERN), Japan (KEK), and the United States (FermiLab). Each of these facilities has an accelerator and a collection and cooling system, and some of these accelerators include both positive and negatively charged ions, and/or electrons, in the same accelerator. But the oppositely charged particles travel in opposite directions through the accelerator systems. In certain instances, it can be beneficial for a single system to be able to deliver either a negatively charged, or positively charged beam. Using conventional technology, however, this would require the inclusion of two different accelerators and beam delivery units, one to accelerate positively charged ions in one direction and one to accelerate negatively charged ions in the other direction. Since these devices and the facilities designed to house them are quite large, it is impractical to have two separate systems to deliver both positively and negatively charged ion beams in the same direction. In the embodiments described below, however, a single accelerator can be used to accelerate either positively or negatively charged ions in the same direction. For example, in certain embodiments, a system as described herein can deliver either positively charged or negatively charged ions for treatment of a patient as described above. In order to provide a beam of either positively or negatively charged ions using a single accelerator, a configurable power source for supplying a current to bending magnets in the accelerator is included in the system. The power source must be configurable so that the direction of the current supplied can be changed in order to change the polarity of the bending magnets. This allows a single accelerator to accelerate positive and negatively charged ions in the same direction. Further, a controllable injection port for injecting either negative or positively charged ions into the accelerator should also be included in the system. For example, the injection port can be controlled via magnets so as to select either positively or negatively charged ions for injection into the accelerator. As mentioned above, the accelerator can either be a cyclotron, synchrotron, synchrocyclotron, or a FFAG. In other embodiments, the accelerator can be a linear accelerator such as a Linac, or a RFQs, or a pulsed-forming system using Blumlein Technology. FIG. 14 is a diagram illustrating a synchrotron 1400 for use in a bipolar accelerator system that can provide either positively charged or negatively charged ions in the same direction. It will be understood, however, that the synchrotron depicted, and described in relation to FIG. 14 is by way of example only and should not be seen as limiting the systems and methods described herein to any particular type of synchrotron or to any particular type of accelerator. In fact, it will be understood that the systems and methods described herein can be extended to other types of accelerators, such as cyclotrons, synchrocyclotrons, and FFAG's. Synchrotron 1400 generally consists of two straight sections 30 and two 180 degree arc sections 32. Each straight section 30 can include five half-cells 34, without bending magnets, and each arc section 32 can include seven half-cells 36 with combined function magnets (FODO magnets). The straight sections 30 accommodate the functions of injection, extraction, and acceleration. The primary physical and optical parameters for the synchrotron are listed in Table 1. TABLE 1Circumference, C [m]30.65Number of FODO cells in the arcs7Half-cell length in the arc [m]1.1Maximum distance between quadrupoles [m]1.8Bend magnetic length [m]0.760Quadrupole magnetic length [m]0.14Injection pulse length, Δt [ns] 25-100Injection pulse current [mA]0.06-2.72Normalized rms emittance, e [μm]0.15Momentum width at injection (rms), σp/p0.001Total momentum width at injection, Δp/p+/−0.0023Total kinetic energy width at injection, ΔK [keV]+/−32 Horizontal tune, Qx3.38Vertical tune, Qy3.36Average phase advance per cell, Horizontal (Arcs)108[deg]Average phase advance per cell, Vertical (Arcs) [deg]92.16Max. horizontal beta function, βxmax [m]5.79Max. vertical beta function, βymax [m]6.23Max. dispersion function, ηmax [m]2.01Natural horizontal chromaticity, ξx−1.48Natural vertical chromaticity, ξy−4.14Transition gamma, T2.72 The half-cell magnets 34 used in the straight sections can be short quadrupole magnets for beam focusing. The combined function main magnets 36 can be the sole optical component of the arcs. As will be discussed in further detail below, the combined function magnets both bend the beam and focus/defocus the beam. In particular, the combined function magnets 36 can be bent in a chevron shape, with respect to a magnet center of curvature, for bending the proton beam. These magnets can be further designed in either a focusing (F) or defocusing (D) style that differ only slightly in the 2-D cross section of the magnet laminations. The optical lattice can also include a modest number of dipole correctors 38 and Beam Position Monitors (BPMs) 40. Each BPM is integrated into a vacuum pipe near the RCMS quadrupoles 34. In certain embodiments, only one type of each of these magnets (and diagnostics) is used, simplifying the design and reducing the required number of spares. In certain embodiments, one half-cell in one of the straight sections 30 is occupied by a radio frequency cavity 42. Moreover, each straight section 30 further includes a fast kicker 44a and 44b and a septum magnet 46a and 46b separated by one half-cell. Variation of the extraction energy can be achieved by adjusting a trigger based on the RF frequency to control the extraction time. This avoids the necessity for energy degraders, delivering a high quality beam with good energy resolution and few losses. Although the excitation of the transport line magnets needs to change in proportion to the extraction momentum, the transport lines are designed to be insensitive to momentum matching errors and magnet settling effects, since they are achromatic and (mostly) dispersionless. The dispersion at the entrance and exit points of the arcs 32 is zero, so the straight sections 30 are dispersion free. The dispersion matching in the arcs 32 can be performed by choosing suitable values for the quadrupole components of the two different kinds of combined function magnet 36. The quadrupole components of the combined function magnet 36 can also been chosen to make the beam size as small as possible. Since the half cells 34 in the straight sections 30 are longer than those in the arcs 32, it can be necessary to match the beta functions between the arcs and the straight sections. Table 3 lists the expected beams sizes and other parameters at 3 times corresponding to injection, minimum extraction energy, and maximum extraction energy, using the beam parameters from Table 2. TABLE 2In-jectionminimummaximumKinetic energy, K [MeV]7.060.0250.0Momentum, p [MeV/c]114.8340.87729.1Lorentz1.00751.06391.2664Lorentz0.1220.34150.614Revolution frequency, Frev [MHz]1.1883.3406.002Revolution period, Trev [μs]0.8420.3000.166Rigidity, Bρ [Tm]0.3831.1372.432Dipole field, B [T]0.2260.6711.436Normalized rms emittance [μm]0.150.150.15Unnormalized RMS emittance εu [μm]1.220.4130.193Max vertical rms beam size [mm]2.761.601.10Max horizontal rms beam size [mm]2.661.551.06Max dispersive (horz) size, HWFM6.502.670.97[mm] A single resonant power supply can be configured to drive all of the synchrotron bending magnets in series, combining a sinusoidal alternating current of amplitude IAC with a constant direct current IDC, so that the total bending magnet current is:I(t)=IDC−IAC cos(2πfrept) Injection occurs at t=0 when the current I=IDC−IAC is at its minimum. Extraction can occur at any time between t=7 ms and t=16.7 ms, when the kinetic energy K is in the range 20 to 300 MeV, for example in the range 60 to 250 MeV. The magnetic field B in the bending magnets, and the beam momentum P are both proportional to the main magnet current (except for small saturation effects). The energy for the beam acceleration is supplied by a single Radio Frequency (RF) cavity 42, with a voltage that varies sinusoidally during the acceleration half of the magnetic cycle. The RF system and beam performance in longitudinal phase space are discussed at greater length below Beam injector module 35 can be a conventional tandem Van de Graaf injector. While the incoming beam from injector 35 into the synchrotron 1400 is always in the same horizontal plane as the circulating beam, the horizontal angle and displacement between the two must be reduced to zero. This is the function of the electrostatic injection inflector 46a and the injection kicker 44a, shown in FIG. 14. The electrostatic injection inflector 46a generates a constant electrostatic field and, at the end of the inflector both beams are in the same beam pipe for the first time. The injection kicker 44a, which is a pulsed magnet, completes the task of injection. Example key parameters of the electrostatic inflector 46a and the injection kicker 44a are summarized in Table 3. TABLE 3Electrostatic inflectorBend angle, Φ6.5°Radius of curvature, ρ [m]11.5Active length, D + d [m]1.4Septum thickness [mm]1Gap, g| [mm]18Voltage, V [kV]22Electric field [kV/cm]12Injection KickerKick angle, ΦK [mrad]5.3Magnetic length [m]0.2Magnetic field, B [G]100Gap, gK [mm]30Current, N| [A]240Rise time [ms]<16Flat top [ns]>100Fall time [ns]<600(Revolution, Period [ns]840) Turning to the extraction side of the synchrotron 1400, the fast kicker magnet on this side is termed an extraction kicker 44b and the septum magnet is termed an extraction septum 46b. The injection and extraction interfaces of the synchrotron 1400 are similar in many ways. The extraction kicker 44b begins the extraction process by quickly turning on a vertical magnetic field during a selected turn number, thereby selecting the energy of the extracted beam. The angle is sufficient to move the beam horizontally across a current sheet at the upstream end of the extraction septum magnet 46b, which also bends the beam horizontally. The positions of the extraction kicker 44b and the extraction septum 46b are shown schematically in FIG. 14. Example parameters of the extraction kicker 44b and the septum magnet 46b are summarized in Table 4. TABLE 4Extraction KickerBend Angle [mrad]5.48Magnetic strength [Gm]133Magnetic length [m]0.8Magnetic field [G]167Gap [mm]30Current [A]398Rise time [ns]<100Flat top [ns]>70Fall time [ms]<16(Revolution Period [ns]167)Septum MagnetBend angle6.5°Radius of curvature [m]12.268Length [m]1.481Magnetic field [G]1983Gap [mm]12Septum (Cu) thickness [mm]4Current [A]1893Half-sine pulse length [μs]10Ripple<2% In order for, e.g., synchrotron 1400 to accelerate both positively charged and negatively charged ions, e.g., protons and anti-protons, in the same direction, the magnetic field for bending magnets 36 must be reversed. It will be understood that for linear accelerators, where the ions are accelerated in a straight line, accelerating both positively charged and negatively charged ions is not such an issue, since the ions are being accelerated by an electromagnetic wave. Accordingly, positive ions will be accelerator in one direction, e.g., in the crest of the wave, while negative ions can be accelerated in the same direction in the trough of the wave. But if the ions must travel around a bend, e.g. sections 32 of synchrotron 1400, then the magnetic field polarity of, e.g., magnets 36 should be reversed for negative ions versus positive ions. This can be achieved by reversing the current supplied by the main magnet power supply. FIG. 15 is a diagram illustrating a an example beam delivery system 1500 comprising a synchrotron 1400 and a configurable power supply 1502 in accordance with one embodiment. In system 1500, the current supplied by main magnet power supply 1502 can be reversed, which can cause the polarity of the magnetic field generated by bending magnets 36 to be reversed. Thus, synchrotron 1400 can accelerate both positively charged and negatively charged particles in the same direction. It should be noted that the magnetic fields generated by bending magnets 36 can, in certain embodiments, also be re-phased for optimum performance. Further, in certain embodiments, the polarity of the magnetic field produced by magnets 34 can also be reversed, and the field re-phased, in unison with that of magnets 36. Configurable power supply 1502 can be controlled by an input form a control system interfaced with system 1500. For example, a computerized control system, such as the treatment protocol station illustrated in FIG. 12, can be interfaced with system 1500 and configured to cause power supply 1500 to reverse the direction of the current provided as required to accelerate either positive or negative ions. Alternatively, power supply 1502 can be configured for manual configuration. In embodiments that use both positive and negative ions, the treatment protocol station can be configured to determine the amount of negative ion radiation and/or positive ion radiation needed to terminate the target mass in a similar manner as described above for antiproton treatments. Thus, the protocol treatment facility can be configured to use equations, this time for positive and/or negative ions as required, to determine the amount of energy deposited in collateral tissue and the residual energy plus annihilation event radiation effects, such as caused by the emission of particles like alpha particles. The energy deposited in the mass, along with the lateral spreads and Bragg Peak contours, can also be determined. Once done, an energy deposition profile can be generated that covers the entire mass with sufficient positive ion and/or negative ion induced radiation by summing multiple Bragg Peaks, assuming a plurality of spot scans performed at varying depths within the tumor region. The amount and energy level of ions, positive and/or negative, for each location to be irradiated, defines the protocol, which can then be sent to the antiproton radiation and imaging device, as previously discussed. During operation, a beam monitoring system and range shifter can be used to measure the actual dosage of negative ions being delivered to insure it correlates with the desired calculated dosage. To the extent a range shifter is used, negative ion losses, caused by the degradation process, need to be calculated and incorporated into all beam monitoring calculations to insure accurate determination of actual negative ions delivered to the patient. More conventional techniques can be used for real-time imaging and dosage analysis for the positive ions. An example main magnet power supply system 1600 that can be configured to perform the functions required for controllable power supply 1502 is illustrated in FIG. 16. In this example embodiment, power supply system 1600 comprises a single 30 Hz series resonant power supply that drives, e.g., the 14 combined function magnets 36 in series. Such systems are extremely reliable because of their simplicity. Besides their simplicity, resonant power supplies have the major advantage of continuously exchanging stored energy between the magnets and capacitors, with the power supply providing only the losses. This makes them very economical to operate. It also greatly reduces the power line swing, when compared to a rapid cycling programmable power supply. The large variations in reactive power flow that otherwise occur cause voltage flicker problems, which can be very costly to solve. The power supply generates a current of the form:Im(t)=Idc−Iac, cos(27πft), where a direct current bias of Idc=1480 Amps is added to the sinusoidal alternating current (Iac=1090 Amps) to ensure that the minimum current matches the required field at injection. The beam can be injected into the ring at t=0 when I=390 Amps. The beam can be extracted sometime before t=16.66 ms when Im(t)=2570 Amps. Except for iron saturation effects, the beam momentum is directly proportional to the plain magnet current. Referring to FIG. 17 power supply system 1600 can comprise two capacitor banks with DC bypass chokes are used in series with the magnets of the synchrotron. The resonant circuit can be driven by one programmable excitation power supply. In a series resonant topology, the excitation power supply can deliver the full magnet current, but at a significantly reduced voltage when compared to a non-resonant system. The chokes can be designed with secondary windings, which can be connected to provide coupling between the individual resonant circuits. Table 5 shows example parameters for one embodiment of the main magnet power supply system 1600. TABLE 5Repetition Rate, frep [Hz]30TopologySeries ResonantNumber of excitation power supplies1Excitation power supply voltage [V]+/−250Maximum power supply current [A]3000Nominal peak current2700Injection current [A]390Direct current, IDC [A]1480Alternating current, IAC [A]1090Number of capacitance banks2Number of bypass chokes2Number of main magnets14Capacitance per bank [mF]10.58Inductance of choke [mH]5.32Inductance of main magnet [mH]0.76Resistance of choke [mΩ]10DC resistance per main magnet [mΩ]1Quality factor28Magnet stored energy [kJ]39.0Capacitor stored energy [kJ]12.8Choke stored energy [kJ]26.2Maximum reactive power [MW]4.5Capacitor losses [kW]7.4Choke losses [kW]98Magnet losses (total) [kW]53TOTAL losses [kW]163 Referring back to FIG. 14, ions can be injected into synchrotron 1400 via injection port 35. FIG. 17 is a diagram illustrating a dual function injection port 1700 configured to inject both positive and negative ions in accordance with one embodiment. Dual function injection port 1700 comprises a positive ion, e.g., proton, pathway 1706 configured to supply positive ions 1708 to injection port 35. Dual function injection port 1700 also comprises a negative ion, e.g., anti-proton, pathway 1704 configured to supply negative ions 1710 to injection port 35. A magnet, or magnets 1712 can be included and configured to control whether positive or negative ions are supplied to injection port 35. In other words, the polarity of the magnetic filed produced by magnet(s) 1712 can be controlled so as to allow positive ions 1708 to flow from path 1706 to injection port 35, while blocking negative ions 1710, when synchrotron 1400 is configured to accelerate positive ions. Conversely, when synchrotron 1400 is configured to accelerate negative ions, then the polarity of the magnetic field produced by magnet(s) 1712 can be controlled in manner designed to block positive ions 1708, while allowing negative ions 1710 to flow to injection port 35. In certain embodiments, magnet(s) 1712 can be supplied by the same power supply, e.g., power supply 1502 that is configured to supply power to bending magnets 36. In other embodiments, magnet(s) 1712 can be supplied by a separate, controllable power supply. Such a separate controllable power supply can be controlled either by a control system or manually, depending on the embodiment. Further, the magnetic field produced by magnet(s) 1712 may need to be re-phased when switching between positive and negative ions, depending on the requirements of a particular embodiment. The positive and negative ions can be supplied from a storage container, such as a magnetic containment bottle. Examples of containers for antiprotons are described in U.S. Pat. No. 5,977,554 entitled “Container for Transporting Antiprotons,” filed Nov. 2, 1999, U.S. Pat. No. 6,160,263 entitled “Container for Transporting Antiprotons,” filed Dec. 12, 2000, U.S. Pat. No. 6,414,331 entitled “Container for Transporting Antiprotons and Reaction Trap,” filed Jul. 22, 2002, and U.S. Pat. No. 6,576,9161 entitled “Container for Transporting Antiprotons and Reaction Trap,” filed Jun. 10, 2003, each of which is incorporated herein by reference as if set forth in full. Thus for example, antiprotons can be produced using the system illustrated in FIG. 5. The antiprotons can then be accumulated and stored in a container, such as described in the above patents. As described above, the trapped antiprotons are inserted into, e.g., a linear accelerator or synchrotron, accelerated to appropriate energy levels, and then formed into a beam for use in treatment. In other embodiments, the antiprotons produced by the system in FIG. 3 can be directly input to injector port 1700. In still other embodiments, ions can be supplied by some other system such, or including a small cyclotron or synchrotron. Referring back to FIG. 7, the ions can then be supplied via delivery pipe 1005 to a gantry. As explained, the gantry may include magnets 1030 configured to guide the antiproton beam through bends in the gantry and ultimately to nozzle 1035. In certain embodiments that gantry can also be configured to supply both positive and negative ions. Accordingly, the polarity of the magnetic field produced by magnets 1030 can also be reversed as required to accelerate either positive or negative ions. In certain embodiments, magnets 1030 can be supplied by power supply 1502. In other embodiments, magnets 1030 can be supplied by a separate controllable power supply. Such a separate controllable power supply can be controlled either by a control system or manually, depending on the embodiment. Further, the magnetic field produced by magnets 1030 may need to be re-phased when switching between positive and negative ions, depending on the requirements of a particular embodiment. It will be understood that the gantry or delivery system can comprise other magnets configured to guide the positive or negative ion around bends. It will be further understood that the polarity of the magnetic fields produced by any such magnets may need to be reversed based on whether a positive or negative ion beam is being generated in the system. In fact, the beam can be delivered to multiple treatment rooms, such as treatment rooms 1103 illustrated in FIG. 11. In which case, bending magnets 1110 may need to be controlled so as to direct positive or negative ions as required. FIG. 18 is a diagram illustrating an example treatment facility 1800 that comprises a medical facility 1806 that includes multiple treatment rooms 1103. Treatment rooms 1103 can include gantries or other devices configured to deliver positive or negative ion treatments. Treatment facility 1800 can also comprise an ion beam generation facility 1802, comprising, e.g., a synchrotron 1400, adjacent to medical facility 1806. Synchrotron 1400 can be configured to provide positive or negative ion beams for use in treatment rooms 1103 as required. Treatment facility 1800 can also comprise an ion production facility adjacent to beam generation facility 1802. ion production facility can be configured to produce positive or negative ions, which can then be provided to beam generation facility 1804. As described above, the ions produced in ion production facility 1804 can be directly interfaced, e.g., with synchrotron 1400, or they can be trapped and stored in a container for transport to beam generation facility 1802. While certain embodiments of the inventions have been described above, it will be understood that the embodiments described are by way of example only. Accordingly, the inventions should not be limited based on the described embodiments. Rather, the scope of the inventions described herein should only be limited in light of the claims that follow when taken in conjunction with the above description and accompanying drawings. |
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051165678 | summary | BACKGROUND OF THE INVENTION This invention relates to nuclear reactors and, more particularly, to fuel arrangements in a reactor core. A major objective of the present invention is to provide for more thorough fuel burnups to enhance fuel utilization and minimize active waste products. Fission reactors rely on fissioning of fissile atoms such as uranium isotopes (U233, U235) and plutonium isotopes (Pu239, Pu241). Upon absorption of a neutron, a fissile atom can disintegrate, yielding atoms of lower atomic weight and high kinetic energy along with several high-energy neutrons. The kinetic energy of the fission products is quickly dissipated as heat, which is the primary energy product of nuclear reactors. Some of the neutrons released during disintegration can be absorbed by other fissile atoms, causing a chain reaction of disintegration and heat generation. The fissile atoms in nuclear reactors are arranged so that the chain reaction can be self-sustaining. To facilitate handling, fissile fuel is typically maintained in modular units. These units can be bundles of vertically extending fuel rods. Each rod has a cladding which encloses a stack of fissile fuel pellets. Generally, each rod includes a space or "plenum" for accumulating gaseous byproducts of fission reactions which might otherwise unacceptably pressurize the rod and lead to its rupture. The bundles are arranged in a two-dimensional array in the reactor. Neutron-absorbing control rods are inserted between or within fuel bundles to control the reactivity of the core. The reactivity of the core can be adjusted by incremental insertions and withdrawals of the control rods. Both economic and safety considerations favor improved fuel utilization, which can mean less frequent refuelings and less exposure to radiation from a reactor interior. In addition, improved fuel utilization generally implies more complete fuel "burnups". A major obstacle to obtaining long fuel element lifetimes and complete fuel burnups is the inhomogeneities of the neutron flux throughout the core. For example, fuel bundles near the center of the core are surrounded by other fuel elements. Accordingly, the neutron flux at these central fuel bundles exceeds the neutron flux at peripheral fuel bundles which have one or more sides facing away from the rest of the fuel elements. Therefore, peripheral fuel bundles tend to burn up more slowly than do the more central fuel bundles. The problem of flux density variations with radial core position has been addressed by repositioning fuel bundles between central and peripheral positions. This results in extended fuel bundle lifetimes at the expense of additional refueling operations. Variations in neutron flux density occur in the axial direction as well as the radial direction. For example, fuel near the top or bottom of a fuel bundle is subjected to less neutron flux than is fuel located midway up a fuel bundle. These axial variations are not effectively addressed by radial redistribution of fuel elements. In addition to the variations in neutron flux density, variations in spectral distribution affect burnup. For example, in a boiling-water reactor (BWR), neutrons released during fissioning move too quickly and have too high an energy to readily induce the further fissioning required to sustain a chain reaction. These high energy neutrons are known as "fast" neutrons. Slower neutrons, referred to as "thermal neutrons", most readily induce fission. In BWRs, thermal neutrons are formerly fast neutrons that have been slowed primarily through collisions with hydrogen atoms in the water used as the heat transfer medium. Between the energy levels of thermal and fast neutrons are "epi-thermal" neutrons. Epithermal neutrons exceed the desired energy for inducing fission but promote resonance absorption by many actinide series isotopes, converting some "fertile" isotopes to "fissile" (fissionable) isotopes. For example, epithermal neutrons are effective at converting fertile U238 to fissile Pu239. Within a core, the percentages of thermal, epithermal and fast neutrons vary over the axial extent of the core. Axial variations in neutron spectra are caused in part by variations in the density or void fraction of the water flowing up the core. In a boiling-water reactor (BWR), water entering the bottom of a core is essentially completely in the liquid phase. Water flowing up through the core boils so most of the volume of water exiting the top of the core is in the vapor phase, i.e., steam. Steam is less effective than liquid water as a neutron moderator due to the lower density of the vapor phase. Therefore, from the point of view of neutron moderation, core volumes occupied by steam are considered "voids"; the amount of steam at any spatial region in the core can be characterized by a "void fraction". Within a fuel bundle, the void fraction can vary from about zero at the base to about 0.7 near the top. Continuing the example for the BWR, near the bottom of a fuel bundle, neutron generation and density are relatively low, but the percentage of thermal neutrons is high because of the moderation provided by the low void fraction water at that level. Higher up, neutron density reaches its maximum, while void fraction continues to climb. Thus, the density of thermal neutrons peaks somewhere near the lower-middle level of the bundle. Above this level, neutron density remains roughly stable while the percentages of epithermal and fast neutrons increase. Near the top of the bundle, neutron density decreases across the spectrum since there are no neutrons being generated just above the top of the bundle. The inhomogeneities induced by this spectral distribution can cause a variety of related problems. Focusing on the upper-middle section, problems of inadequate burnup and increased production of high-level waste are of concern. Since the upper-middle section has a relatively low percentage of thermal neutrons, a higher concentration of fissile fuel is sometimes used to support a chain reaction. If the fuel bundle has a uniform fuel distribution, this section could fall below criticality (the level required to sustain a chain reaction) before the other bundle sections. The fuel bundle would have to be replaced long before the fissile fuel in all sections of the bundle were depleted, wasting fuel. The problem with waste disposal is further aggravated at this upper-middle section since the relatively high level of epithermal neutrons results in increased production of actinide-series elements such as neptunium, plutonium, americium, and curium, which end up as high level-waste. One method of dealing with axial spectral variations is using a control rod. For the BWR, control rods typically extend into the core from below and contain neutron-absorbing material which robs the adjacent fuel of thermal neutrons which would otherwise be available for fissioning. Thus, control rods can be used to modify the distribution of thermal neutrons over axial position to achieve more complete burnups. However, control rods provide only a gross level of control over spectral density. More precise compensation for spectral variations can be implemented using enrichment variation and burnable poisons. Enrichment variation using, for example, U235 enriched uranium, can be used near the top of a fuel bundle to partially compensate for a localized lack of thermal neutrons. Similarly, burnable poisons such as gadolinium oxide (Gd.sub.2 O.sub.3), can balance the exposure of bundle sections receiving a high thermal neutron flux. Over time, the burnable poisons are converted to isotopes which are not poisons so that more thermal neutrons become available for fissioning as the amount of fissile material decreases. In this way, fissioning can remain more constant over time in a section of the fuel bundle. By varying the amount of enrichment and burnable poisons by axial position along a bundle, longer and more complete burnups can be achieved. In addition, the enrichment and poison profiles can be varied by radial position to compensate for radial variations in thermal neutron density. Nonetheless, taken together, the use of control rods, radial positional exchange of bundles, selective enrichment and distribution of burnable poisons still leave problems with axial variations in burn rates and neutron spectra. Furthermore, none of these employed methods effectively address the problem of the high level of fissile material produced and left in the upper-middle sections of the bundle due to the high level of epithermal neutrons and the low level of thermal neutrons. What is needed is a system that deals more effectively with axial spectral variations in neutron flux so that higher fuel burnups are provided and the so that high-level waste is minimized. SUMMARY OF THE INVENTION In accordance with the present invention, a nuclear reactor with a recirculating heat transfer fluid has a bi-level core which provides enhanced flexibility in fuel arrangement. The bi-level core includes two sets of fuel units, one set arranged on a first level, the other set arranged on a second level. Preferably, fuel units of the second level are arranged in vertical alignment with fuel units of the first level. This permits a fuel unit of the first level to be accessed by removing only the adjacent fuel unit of the second level. During refueling operations, fuel units can be shifted from one level to the other, providing additional flexibility in arranging units at various stages of burnup. Preferably, fuel units of the first level are inverted relative to the fuel units of the second level. The inversion provides for placing plenum sections of fuel rods in different levels away from each other so that the plenums do not introduce a discontinuity in neutron generation. In the context of a boiling-water reactor, fuel bundles are arranged into upper and lower matrices. The fuel bundles share a common form factor so that each fuel bundle can be placed in any position in either matrix. During refueling operations net transfers are as follows: spent bundles are removed from the lower matrix, partially spent bundles from the upper matrix are inserted into the lower matrix, and fresh bundles are inserted into the upper matrix. This fuel bundle "flow" is an average flow and does not exclude the possibilities that some elements are retired from the upper matrix, some fresh fuel bundles are inserted into the lower matrix, and that some partially spent fuel bundles are transferred from the lower matrix to the upper matrix. The fuel bundles can contain multiple fuel rods. Each fuel rod can include a plenum at one end where gaseous fission byproducts can accumulate. The plenum ends are preferably directed away from the interface between the upper and lower matrices. In other words, the plenums are up in the upper matrix and down in the lower matrix. Otherwise, at least one plenum would be positioned between the fuel in the same rod and the fuel in the corresponding rod in the other matrix. This would introduce discontinuities in neutron generation and temperature. Separation of fuel in the upper and lower matrices is minimized by inverting the fuel bundles when they are moved from one matrix to the other. Moreover, channel and core stability are enhanced using this inverted fuel bundle arrangement. Stable thermal hydraulic operation, that is, the propensity to damp stochastic disturbances in flow and void fraction, is promoted more effectively where there is a liquid water phase adjacent to the fuel rod plenums than where there is a combination of liquid and vapor phases. Relative to one-level cores in which all plenums are near the top, the present invention provides greater stability since at least part of the plenum volume is at the core entrance where there are no steam voids and the overall two-phase flow pressure drop is reduced. Due to heating by the core, the void fraction of the water increases at higher levels so that the steam void fraction is greater at the level of the upper matrix than it is at the level of the lower matrix. Accordingly, neutron moderation is more effective at the lower level than at the upper level. Because of the difference in moderation, fuel bundles in the upper matrix are subjected to a harder neutron spectrum than are the fuel bundles in the lower matrix. The harder neutron spectrum can be taken advantage of by the fresher fuel bundles in the upper matrix. The harder neutron spectrum contains a higher percentage of fast and epithermal neutrons, while the thermal neutron spectrum contains a higher percentage of slower thermal neutrons. Thermal neutrons are more effective than faster neutrons at causing fission. The faster neutrons are more likely to be subjected to resonance absorption, which is likely to result in a non-fissioning neutron absorption. Non-fissioning neutron absorption results in isotopic enhancement. In other words, the hard neutron spectrum breeds fissile fuel from fertile material. The primary reaction is the absorption of a fast neutron by fertile U238 to yield fissile Pu239. Neutron absorption by Pu239 can result in fission or in the formation of the next plutonium isotope, fertile Pu240. Neutron absorption by fertile Pu240 results in a fissile Pu241 isotope. The net effect of the hard neutron spectrum is production of additional fissile material as the original fissile material is partially spent. Thus, the relatively hard neutron spectrum of the upper fuel matrix can be used to breed fissile fuel, enhancing the operational lifetime of a fuel bundle. The harder neutron spectrum in the upper matrix is less effective in inducing fission. This is not a problem where relatively fresh fuel bundles in the upper matrix contain relatively high concentrations of fissile fuel, typically, U235. As the U235 is depleted faster than additional fissile fuel is created, the hard neutron spectrum would eventually be unable to support a chain reaction. Prior to this point, the no-longer-fresh fuel bundle can be transferred from the upper matrix to the lower matrix, which is exposed to a more thermal neutron spectrum. Since thermal neutrons are most effective at inducing fission, fuel in the lower matrix can be more fully utilized. This provides advantages in fuel economics as well as waste disposal. Since the fuel in the lower matrix is subjected to a thermal spectrum, there is less resonance absorption, resulting in less high-level waste. In addition, the thermal neutron spectrum at the lower matrix is less prone to breed additional fissile material. Thus, isotopic enhancement, which might otherwise contribute to higher levels of radioactivity in the spent fuel elements, is minimized by the soft neutron spectrum of the lower matrix. In summary, the present invention provides for enhanced fuel arrangement flexibility which can take advantage of axial neutron spectral shifts through the core. As a result, fuel lifetimes are increased and the quantity of high-level nuclear waste is minimized. These and other features and advantages of the present invention are apparent in the following description with references to the drawings below. |
description | This application claims the benefit of U.S. provisional application Ser. No. 61/015,392 filed Dec. 20, 2007, which is incorporated herein by reference. The present application relates to computed tomography imaging. It finds particular application in connection with an attenuation system for variably filtering a beam of radiation so that in irradiating a subject, radiation which contributes little to a reconstruction of the imaging subject is attenuated. In a typical computed tomography (CT) imaging apparatus, an x-ray tube is mounted on a rotating gantry that defines an examination region inside which an imaging subject is disposed. The x-ray tube rotates about the subject on the rotating gantry and projects a wedge-, fan-, cone-, or otherwise-shaped x-ray beam through the examination region. A two-dimensional x-ray detector disposed on the rotating gantry across the examination region from the x-ray tube receives the x-ray beam after passing through the examination region. Suitable electronics estimate x-ray absorption data based on the detected x-ray intensities, and an image reconstruction processor reconstructs an image representation based on the absorption data. In cone-beam reconstruction methods, multiple rays (pi partners) eligible for backprojection through the same voxel are weighted according to their cone angle. Oblique rays are downweighted more strongly than less oblique rays. This leads to a mismatch in dose utility between these rays. The irradiated subject is thus unnecessarily fully exposed to rays that have little contribution to the final image. The present application provides a new and improved apparatus and method which overcome the above-referenced problems and others. In accordance with one aspect, a computed tomography apparatus includes spaced radiation sources which each propagate a cone-beam of radiation into an examination region. A detector detects radiation which has passed through the examination region. An attenuation system is interposed between the radiation sources and the examination region for cone-angle dependent filtering of the cone beams. In accordance with another aspect, a method of computed tomography imaging includes projecting first and second cone beams of radiation towards an examination region and, prior to the examination region, attenuating the first and second cone beams to form attenuated first and second cone-beams, the attenuation being dependent on a cone angle. Radiation data from the examination region is acquired. In accordance with another aspect, an imaging apparatus includes a radiation source which propagates a cone-beam of radiation into an examination region. A detector detects radiation which has passed through the examination region. A filter, formed of a material which attenuates the radiation, is interposed between the radiation source and the examination region, the filter providing cone-angle dependent filtering of the cone beam, whereby more obliquely angled rays are filtered more than less obliquely angled rays. One advantage is that a patient receives less exposure to x-rays that have little contribution to the final image. Another advantage is that the radiation from a stereo x-ray tube is more evenly spread across the field of view in the scanning direction. Still further advantages of the present invention will be appreciated by those of ordinary skill in the art upon reading and understand the following detailed description. With reference to FIG. 1, a computed tomography imaging scanner 10 includes a subject support 12 for moving a subject such as a medical patient, an item of luggage undergoing a security scan, or the like into or within an examination region 14 defined by a rotating gantry 16. A source of radiation, such as an x-ray tube 20 arranged on the gantry 16 projects at least one conically-shaped x-ray beam (a “cone beam”) into the examination region 14 where it interacts with the imaging subject. Some portion of the x-rays are absorbed by the imaging subject to produce a generally spatially varying attenuation of the cone beam. A two-dimensional x-ray detector 22 disposed on the gantry 16 across the examination region 14 from the x-ray tube 20 measures the spatially-varying intensity of the x-ray beam after the x-ray beam passes through the examination region 14. Typically, the x-ray detector 22 is mounted on the rotating gantry 16. The detector 22 thus moves relative to the subject during imaging. In another suitable arrangement, the detector is arranged circumferentially on a stationary gantry surrounding the rotating gantry. In helical computed tomography imaging, the gantry 16 rotates simultaneously with a linear motion of the subject support 12 in the z direction to effect a helical trajectory of the x-ray tube 20 about the examination region 14. For this application, a drive system 24 includes a rotation controller 26 for controlling gantry rotation and a linear advancement controller 28 for controlling the linear advancement. In axial computed tomography imaging, the gantry 16 rotates while the subject support 12 remains stationary to effect a circular trajectory of the x-ray tube 20 about the examination region 14. In volumetric axial imaging, the subject support 12 is repeatedly stepped linearly with an axial scan performed for each step to acquire multiple image slices along the axial direction. Acquired imaging projection data with an index of the apex of the cone and of the trajectory within the cone is transmitted from the detector 22 and stored in a digital data memory 30. A reconstruction processor 32 reconstructs the acquired projection data, using filtered backprojection or another reconstruction method, to generate a three-dimensional image representation of the subject or of a selected portion thereof, which is stored in an image memory 34. The image representation is rendered or otherwise manipulated by a video processor 36 to produce a human-viewable image that is displayed on a graphical user interface 38 or another display device, printing device, or the like for viewing by an operator. In one embodiment, the graphical user interface 38 is programmed to interface a radiologist with the computed tomography scanner 10 to allow the radiologist to execute and control computed tomographic imaging sessions. In a cone beam 40, as illustrated schematically in cross sectional view in FIG. 2, the rays emanate from a focal point 42. The rays have a maximum beam angle α such that the rays pass through a subject 44 in a generally circular area 46 which has a central axis with a dimension in the z direction. The value of the maximum beam angle α determines the dimension of this area. FIG. 2 illustrates a dual beam arrangement in which first and second cone beams 40, 50 emanate from focal spots 42, 52 which are spaced, in the z direction by a distance d of, for example, about 10-20 cm, e.g., 12 cm. The two cone beams 40, 50 irradiate the same general area of the subject. As can be seen, the two beams 40, 50 overlap in coverage within a field of view 54 of the detector 22. In one embodiment, the beams 40, 50 are alternately pulsed such that the subject 44 and the detector 22 receive radiation from only one of the two beams 40, 50 at a given time. The pulse rate may be higher than the rotation speed of the gantry, for example, at least about 20,000 cycles/second. In one embodiment, the beam, and thus the focal spot is changed for each sampling period. An advantage of a dual beam scanning system 10 as illustrated in FIG. 2 is that a larger amount of data can be acquired in each circular arc. This is particularly advantageous, for example, in cardiac scanning where the rhythmical beating of the heart muscles causes positions of features being scanned to change rhythmically during scanning. Another advantage of such a system is that a second pass cone beam artifact correction scheme may be employed. The exemplary detector 22 has a radius of curvature equivalent to the distance to the two focal spots 42, 52 (both being equally spaced from the detector) and includes a plurality of segments. Each segment includes a plurality of detector elements which deliver a measurement value for pairs of rays (pi-partners) of the two radiation beams incident thereon. The accumulated measurement values, optionally after an initial preprocessing, form the data that is sent to the reconstruction processor 32. With continued reference to FIG. 2, an attenuation system 55 is interposed between the focal spots 42, 52 and the examination region 14 for cone-angle dependent filtering of the cone beams 40, 50. In general, a method of computed tomography imaging which may be performed using the attenuation system 55 described herein includes projecting the first and second cone beams 40, 50 of radiation towards the examination region 14. Prior to reaching the examination region, the first and second cone beams are attenuated to form attenuated first and second cone-beams. The extent of attenuation is dependent on the cone angle. Radiation data is acquired from the examination region and an image is reconstructed, based on the radiation data. With continued reference to FIG. 2, in one embodiment, the attenuation system 55 includes first and second filters 56, 58. The filters 56, 58 are formed of any suitable material capable of attenuating x-rays without significantly impacting the spectrum or angle of travel of the rays. Exemplary materials for forming the filters 56, 58 include aluminum, graphite, and perfluorinated polymers, such as Teflon®. The exemplary filters are physical (hardware) filters which variably attenuate radiation by virtue of their varying thickness (rather than software filters). The illustrated cone beams 40, 50 are mirror images of each other and the exemplary filters 56, 58 are likewise mirror images of each other. Each of the filters 56, 58 provides cone-angle dependent filtering of the respective beam 40, 50. Specifically, the filter 56, 58 attenuates the beam in the z-direction (linear scanning direction) progressively more as the cone angle of the ray increases. The cone angle is the angle of a given ray within the beam as determined from a plane in which the focal spot lies that is oriented normal (90° to the z direction. The attenuation by the filter 56, 58 is lowest for rays R1, which approach the subject from the least oblique angle of the beam and highest for rays R2, which approach the subject at the most oblique angle of the beam. In FIG. 2, the least oblique angle is at 0°, i.e., normal to the z direction and the most oblique angle is the maximum beam angle α from normal to the z direction. Attenuation refers to the extent to which the intensity of the x-ray beam is reduced as it passes through the filter 56, 58. Thus, when the filter attenuation is lowest, the intensity of the radiation transmitted is a maximum, Imax. A maximum attenuation of the filter 56, 58 of the x-rays entering the field of view 54 corresponds to the minimum intensity of the transmitted radiation, Imin. The minimum attenuation (at Imax) provided by the filter 56, 58 for those x-rays entering the field of view may be about 0% (substantially no attenuation, thus Imax=I0, the intensity of the radiation incident on the filter). The maximum attenuation, at Imin provided by the filter 56, 58 for those x-rays entering the field of view may be up to 100% (full attenuation, no x-rays transmitted). In one embodiment, suitable for full 360° scanning, the attenuation at Imin is 0% Imax. In other embodiments, suitable for partial scanning, Imin is >0% of Imax, e.g., at least about 20% and in some embodiments, up to about 80% of Imax, e.g., about 50% Imax. Between the two extremes, the attenuation may vary linearly with the obliqueness of angle, as illustrated, for example, in FIG. 3. For example, if the maximum cone angle α is 15°, the intensity I at normal (0° is 100% (Imax), and at the full angle α of 15° is about 50% Imax (Imin), then at 7.5° it is about 75% of Imax. In other embodiments, the transmission varies non-linearly, e.g., logarithmically, between the upper and lower values Imax and Imin, as illustrated, for example, in FIG. 4. While FIG. 2 illustrates two spaced filters 56, 58, it is to be appreciated that a single combination filter 60 may alternatively be used, as illustrated in FIG. 5, which combines the functionality of the two filters 56, 58 described above. The combination filter 60 includes first and second filters 62, 64 which are joined together as one piece and perform in the same manner as the separate filters 56, 58. In general, the attenuation provided by the filter 56, 58, 62, 64 is a function of the thickness t of the filter (as experienced by the rays passing through, i.e., in a direction which intersects the respective cone beam). Accordingly, in the exemplary embodiment, the thickness t of the filter changes in the z direction, with the greatest thickness occurring closest to the oblique rays and the least thickness, which may be at or close to zero, closest to the least oblique rays. In another embodiment, the concentration of an attenuating substance in the filter may be varied with the cone angle and thus the filter thickness need not change in the z direction. As illustrated in FIG. 6, in perspective view, the cone-angle dependent filter 56, 58 is wedge shaped, with upper and lower surfaces 66, 68 that meet at a common edge 70 and a side surface 72, which extends between the upper and lower surfaces 66, 68 opposite the edge 70. The illustrated surfaces 66, 68 are curved, i.e., concave towards the focal spot, although in other embodiments, one or both surfaces 66, 68 are planar. The filter 56, 58 has a cross section which is uniform along its length/(i.e., in a direction extending perpendicular to the z direction). The combined filter 60 of FIG. 2 may be similarly configured, except that the two filters 62, 64 meet and thus have no side surface. In another embodiment, shown in FIG. 7, a cone-angle dependent and bowtie combined filter 74 combines the combination filter 60 with a bowtie filter such that the combined filter 74 varies in thickness in both the z direction and xy plane. In this way, a subject to be irradiated, such as a human patient, whose cross section varies in the xy plane, may receive a dose which is more closely related to the cross sectional thickness of the subject. In another embodiment, the scanning apparatus 10 includes a bowtie filter that is separate from the cone-angle dependent filters 56, 58. In the embodiment of FIG. 5, the dual beams 40, 50 are provided by a single, stereo x-ray tube 20. The stereo x-ray tube 20 tube includes a pair of commonly driven rotating tungsten anodes 82, 84. The illustrated anodes 82, 84 are mounted on the same rotatable shaft 86. It is also contemplated that the anodes may be mounted on separate shafts and may be separately driven within the x-ray tube 80. A cathode filament 88, 90, one for each anode 82, 84, is biased negatively with respect to the anode. A cathode cup 92, 94 partially surrounds the filament 88, 90 and is biased negatively to focus the electrons into an electron beam. Electrons generated at the cathode filament 88, 90 by thermionic emission are accelerated by the voltage difference and strike the respective rotating anode 82, 84, producing a beam of x-rays. The x-rays pass through each window 96 in a housing 98 of the x-ray tube 80 tube as a cone beam 40, 50. While FIG. 5 illustrates a double window 96, in one embodiment there is a common window, each beam 40, 50 having its own collimator. In the illustrated embodiment, the electrons from the opposed filaments 88, 90 are pulsed alternately, by alternately actuating a respective gate 100, 102, for example, by applying a voltage between electrodes mounted to the cathode cup 92, 94, which houses the respective filament 88, 90. The gates 100, 102, and/or filament power supplies 104, 106 (FIG. 1), are under the control of a common pulse controller 108. As will be appreciated, in other embodiments, the two beams 40, 50 may be projected from focal spots 42, 52 which are in separate x-ray tubes, an anode of the first tube generating the first cone beam 40 and an anode of a second tube generating the second cone beam 50. In this embodiment, as in the stereo tube embodiment, the focal spots 42, 52 of the two anodes are aligned in the z direction. In the embodiment of FIG. 5, the filters 62, 64 (or alternatively, filters 58, 60, or 74) are positioned exteriorly of the housing 98 to filter the respective beam 40, 50. The filters maintain a fixed orientation to the beam as the beam rotates around the subject. In one embodiment, the filters are fixedly mounted to the housing 98 or to another part of the x-ray tube 20 to minimize any relative motion between the focal spot 42, 52 and the respective filter 62, 64. In another embodiment, the filters 56, 58, 62, 64 are mounted to the gantry carrying the x-ray tube 20. In one embodiment, the position or orientation of the filter to the respective cone beam 40, 50 is adjustable to provide a different cone beam angle dependent filtering (e.g., a higher or lower maximum and/or minimum transmission). For example, in the embodiment of FIG. 2, filters 56, 58 may be movable perpendicular and/or parallel to the beam to vary the thickness experienced by the beam. In yet another embodiment, the filters may be replaceable with differently shaped filters, depending on desired maximum and/or minimum transmissions. For example, in the embodiment of FIG. 6, the height of the wall 72 may vary. In general each filter 56, 58, 62, 64 only receives rays that are within a respective one of the cone beams 40, 50. Each filter 56, 58, 62, 64 thus serves to attenuate rays in only one of the beams 40, 50. For example, as shown in FIGS. 2 and 5, the filters 56, 58, 62, 64 are positioned intermediate the focal point 42, 52 of the respective beam and a point 110 at which the two beams 40, 50 begin to overlap one another. As illustrated in FIG. 8, in a stereo cone-beam CT apparatus which lacks an attenuation system as described herein, multiple rays (pi-partners) are eligible for backprojection through the same voxel 112. The reconstruction processor weights the rays according to their angle. The oblique rays, such as ray R2, are downweighted more strongly than less oblique rays, such as ray R1. Both rays R1, R2 have the same intensity, although in the software reconstruction, the oblique ray R2 will be virtually discarded due to its large cone angle. In the exemplary embodiment, the predictable fixed cone angle ranges of the stereo tube 20 that every voxel in the reconstruction grid is seen under facilitate the use of stationary hardware filters 56, 58, 62, 64 for ray intensity optimization. As illustrated in FIG. 9, the filters 56, 58 attenuate the rays R1, R2 according to their cone angle. The oblique ray R2 receives more filtering than the less oblique ray R1. The exemplary attenuation system 55 disclosed herein thus allows a reduction in the overall x-ray dose that a subject receives, while providing little or no adverse impact on the quality of the images generated during reconstruction, since the rays which are most attenuated in their intensity by the filters are those which tend to be downweighted in the software reconstruction. In one embodiment, the maximum attenuation Tmax of the filter is a function of the coverage of the scan. For example, for a full 360° scan, the maximum attenuation may be higher than for a partial scan (less than 360°, e.g., 180°. This is because the dose distribution is not the same for a full scan and partial scan. In a full 360 degree scan, illustrated in FIG. 10, regions labeled A are x-rayed by just one of the anodes, regions B are partially x-rayed by two anodes and regions C are x-rayed by two anodes for the full 360°. As can be seen from FIG. 2, in a partial scan, the region of the field of view in which the two beams overlap receives a higher dose than the two adjacent regions which are only x-rayed by one beam. To reduce the impact of noise, therefore, for a partial scan of 180°, a maximum filter attenuation may be, for example, about 50%. With reference again to FIG. 1, the imaging projection data acquired by the detector 22 for each cone beam pulse is processed by the reconstruction processor 32. In the exemplary embodiment, first and second data sets 120, 122, one corresponding to each cone beam 40, 50, are processed separately prior to reconstructing the image. The exemplary reconstruction processor 32 includes a calibration component 124 which allows baseline data acquired without a subject to be used in calibrating the imaging projection data. A digital filtering component 126 processes the imaging projection data to filter (e.g., downweight) the data for a voxel in the reconstruction grid according to the determined cone angle of the ray from which the data is derived. Since the calibration component 124 causes the scanner to measure the ratio of outgoing intensity Iout (with subject) to incoming intensity Iin (without subject), the influence of the cone-angle dependent filter is cancelled out and the line integrals that are used in the reconstruction algorithm are the same with or without the filter (other than in the extent of any noise). Accordingly, the reconstruction algorithm used to process the data need be no different from that which would be used without the attenuation system 55. While the exemplary embodiment is discussed in terms of two cone beams 40, 50, it is to be appreciated that a single cone beam may be used. In other embodiments, more than two cone beams may irradiate the subject from respective focal spots which are linearly spaced in the z direction. Each of the plurality of cone beams may have its own associated cone-angle dependent filter. While the exemplary embodiment is discussed in terms of a single detector 22, in another embodiment, a plurality of detectors, spaced in the z direction, e.g., one for each cone beam, may be employed. The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. |
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description | The present invention relates to an exposure apparatus which draws a pattern on a substrate using electron beams and a device manufacturing method using the same. A lithography technique for reducing and transferring various patterns formed on a mask onto a wafer with light beams is used to manufacture devices such as a semiconductor device and the like. A mask pattern for use in lithography is required to have an extremely high degree of accuracy. Hence, to form a mask pattern, an electron beam exposure apparatus is employed. An electron beam exposure apparatus is also employed to directly draw a pattern on a wafer without any masks. Electron beam exposure apparatuses include, e.g., a point-beam type apparatus which uses spot-like beams and a variable rectangular beam type apparatus which uses beams each having a variable-size rectangular cross section. A general electron beam exposure apparatus of either type comprises an electron gun which generates electron beams, an electron optical system for guiding electron beams emitted from the electron gun onto a sample, a stage system for performing scan driving for the sample to draw a pattern on the entire sample with electron beams, and an objective deflector for positioning electron beams on the sample at high accuracy. A region in which the objective deflector can position electron beams is designed to have a width of about several mm in order to minimize any aberration in the electron optical system. When a silicon wafer is employed as the sample, its diameter is about 200 to 300 mmφ. On the other hand, when a glass substrate to be used as a mask is employed, its size is about 150 mm square. For this reason, the electron beam exposure apparatus has a stage which can perform scan driving for the sample to draw a pattern on the entire sample with electron beams. The stage is arranged in a vacuum chamber. The stage is required not to cause any variation in magnetic field, which may affect the positioning of electron beams. For this reason, a contact actuator such as a ball screw actuator is used in a conventional stage. Conventionally, an increase in speed has been demanded for lithography. For example, Japanese Patent Laid-Open No. 9-330867 discloses a multi electron beam exposure apparatus which irradiates the surface of a sample with a plurality of electron beams in accordance with design coordinates and scans the sample surface while deflecting the plurality of electron beams in accordance with the design coordinates and individually turning on/off the plurality of electron beams in accordance with a pattern to be drawn. A multi electron beam exposure apparatus can draw a pattern with a plurality of electron beams and thus can increase the throughput. FIG. 6 is a view showing the outline of a multi electron beam exposure apparatus. Electron guns 501a, 501b, and 501c can individually turn on/off electron beams. A reduction electron optical system 502 reduces and projects a plurality of electron beams from the electron guns 501a, 501b, and 501c onto a wafer 503. A deflector 504 scans the plurality of electron beams to be reduced and projected onto the wafer 503. FIG. 7 shows how the multi electron beam exposure apparatus in FIG. 6 scans a wafer with a plurality of electron beams. White circles represent beam reference positions (BS1, BS2, and BS3) at which each electron beam comes incident on the wafer when it is not deflected by the deflector 504. The beam reference positions are plotted along a design orthogonal coordinate system (Xs,Ys). The respective electron beams scan exposure fields (EF1, EF2, and EF3) for the respective electron beams in accordance with the design orthogonal coordinate system (Xs,Ys) with reference to the beam reference positions. The exposure fields are arranged adjacent to each other, so that a larger pattern can be drawn. The positioning responsiveness of electron beams is extremely high. For this reason, instead of an arrangement for improving the mechanical control characteristics of a stage, there is generally employed an arrangement for adjusting the incident positions of electron beams with respect to a wafer by measuring the posture and positional shift amount of the stage and controlling a deflector for scanning the electron beams on the basis of the measurement result, as disclosed in, e.g., Japanese Patent Laid-Open No. 5-89815. This method, however, is based on the premise that the positional relationship between a wafer to be exposed and a measuring mirror used to measure the posture and positional shift amount of the stage remains unchanged. For example, if a structure is distorted by an external force to cause fluctuations in relative position between the measuring mirror and wafer, a pattern error may occur. In a conventional single-beam exposure apparatus, a focus error (fluctuations in posture) in a stage causes no serious problem. On the other hand, in a multi electron beam exposure apparatus which uses a plurality of electron beams, Z-direction adjustment and posture adjustment (a tilt mechanism) are required to position each electron beam within a predetermined focus tolerance. An increase in the number of degrees of freedom in adjustment increases the number of actuators. The use of an actuator having high rigidity such as a contact actuator is highly disadvantageous in that a structure is distorted by a driving reaction force. An electromagnetic actuator can implement a non-contact arrangement having no rigidity and can solve problems of a driving reaction force and dust. In electron beam exposure, any fluctuations in magnetic field are not allowed even if they are small. Fluctuations in magnetic field can be reduced by arranging an electromagnetic actuator at a position remote from a substrate-bearing surface and providing a multiple shield in the electromagnetic actuator. Therefore, the use of an electromagnetic actuator presently attracts attention. If an electromagnetic actuator is to be employed as an actuator for stage driving in an electron beam exposure apparatus, the electromagnetic actuator must be arranged at a position remote from a substrate-bearing surface, as described above. For this reason, if position measurement for stage control is performed using a mirror arranged on the substrate-bearing surface, vibrations having various natural frequencies occur in a control system. The control gain cannot be set to a high value, thus resulting in difficulty in high-speed and stable control of a stage. Conventionally, this makes it difficult to draw a pattern on a substrate at high speed and high accuracy. The present invention has been made in consideration of the above-mentioned background, and has as its object to, e.g., draw a pattern on a substrate at high speed and high accuracy or stably control a substrate stage in addition to this. According to the present invention, there is provided an exposure apparatus which draws a pattern on a substrate with electron beams, comprising a substrate stage which supports the substrate, a transfer stage which moves with the substrate stage on board, an electromagnetic actuator which moves the substrate stage relative to the transfer stage, a first measurement system which measures a position of the transfer stage, a second measurement system which measures a position of the substrate stage, a controller which controls the electromagnetic actuator on the basis of measurement results obtained by the first and second measurement systems, a deflector which deflects electron beams with which the substrate is irradiated, and a filter which performs filtering for a measurement result obtained by the second measurement system and supplies the filtered measurement result to the deflector. According to a preferred embodiment of the present invention, preferably, the second measurement system measures rotation of the substrate stage in addition to the position of the substrate stage, and the deflector adjusts deviations of electron beams on the basis of the position and rotation of the substrate stage obtained by the second measurement system. According to a preferred embodiment of the present invention, preferably, the second measurement system includes a first sensor which measures a position of the substrate stage with reference to a predetermined reference position, and a second sensor which measures a position of the substrate stage relative to the transfer stage, the controller controls the electromagnetic actuator on the basis of measurement results obtained by the first measurement system and the second sensor, and the filter performs filtering for a measurement result obtained by the first sensor to supply the filtered measurement result to the deflector. According to a preferred embodiment of the present invention, the second sensor is preferably arranged to measure a relative position of the substrate stage in the vicinity of the electromagnetic actuator. According to a preferred embodiment of the present invention, preferably, the substrate stage has a substrate holder on the substrate stage, and the electromagnetic actuator and the substrate are arranged on opposite sides of a barycenter of the transfer stage in a Z-axis direction. According to a preferred embodiment of the present invention, the filter preferably includes a band-limiting filter (e.g., a low-pass filter) which blocks a predetermined band. According to a preferred embodiment of the present invention, the electromagnetic actuator preferably includes an electromagnet as a driving source. Alternatively, the electromagnetic actuator preferably includes a linear motor. According to a preferred embodiment of the present invention, the electromagnetic actuator is preferably coated with an electromagnetic shield. According to the present invention, there is provided a device manufacturing method comprising a step of drawing a pattern on a substrate coated with a photosensitive agent using the above-mentioned exposure apparatus, and a step of developing the substrate. Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. Preferred embodiments of the present invention will be described with reference to the accompanying drawings. [First Embodiment] FIG. 1 is a schematic view showing the main part of an electron beam exposure apparatus according to a preferred embodiment of the present invention. Referring to FIG. 1, an electron gun 1 comprises a cathode 1a, a grid 1b, and an anode 1c. Electrons emitted from the cathode la form a crossover image between the grid 1b and anode 1c (this crossover image will be referred to as an electron source hereinafter). Electrons emitted from the electron source form a substantially parallel electron beam through a condenser lens 2, whose front focal position is located at the electron source position. The substantially parallel electron beam comes incident on an element electron optical system array 3. The element electron optical system array 3 is formed by arranging a plurality of element electron optical systems, each comprising a blanking electrode, an aperture, and an electron lens, in a plane perpendicular to the Z-axis (an electron optical axis). The element electron optical system array 3 forms a plurality of intermediate images of the electron source. The respective intermediate images are reduced and projected onto a wafer 5 by a reduction electron optical system 4, to form electron source images on the wafer 5. The respective element electron optical systems of the element electron optical system array 3 are set such that the spacing between adjacent electron source images on the wafer 5 is an integer multiple of the size of each electron source image. Additionally, the element electron optical system array 3 is arranged to differently adjust the position of each intermediate image in the direction of the electron optical axis, in accordance with the curvature of field of the reduction electron optical system 4, and to correct, in advance, an aberration that occurs when each intermediate image is reduced and projected onto the wafer 5 by the reduction electron optical system 4. The reduction electron optical system 4 comprises a symmetric magnetic doublet including a first projection lens 41 and a second projection lens 42 and a symmetric magnetic doublet including a first projection lens 43 and a second projection lens 44. The distance between the two lenses 41 (43) and 42 (44) is f1+f2 where f1 is the focal length of the first projection lens 41 (43) and f2 is the focal length of the second projection lens 42 (44). The object point on the electron optical axis is at the focal position of the first projection lens 41 (43), and the image point on the electron optical axis is formed on the focal point of the second projection lens 42 (44). This image is reduced to −f2/f1 through these two lenses. The two lens magnetic fields are determined to act in the opposite directions. Hence, theoretically, Seidel aberrations other than five aberrations, i.e., spherical aberration, isotropic astigmatism, isotropic coma, curvature of field, and longitudinal chromatic aberration, and chromatic aberrations concerning rotation and magnification are cancelled. A deflector 6 collectively deflects a plurality of electron beams from the element electron optical system array 3 to displace a plurality of electron source images on the wafer 5 by substantially the same displacement amount in the X- and Y-axis directions. The deflector 6 includes a main deflector which is used when a deflection width is large and a subdeflector which is used when the deflection width is small (both not shown). The main deflector is an electromagnetic defector, while the subdeflector is an electrostatic deflector. A dynamic focus coil 7 corrects the focal position shift of an electron source image formed by the deflection aberration that occurs when the deflector 6 is actuated. A dynamic stigmatic coil 8 corrects deflection aberration caused by deflection, i.e., astigmatism, in the same manner as the dynamic focus coil 7. A fine adjustment stage 11 serving as a substrate stage has a wafer 5 on it and is so arranged as to be movable by a predetermined amount in the direction of the electron optical axis (Z-axis), the rotation direction (θ) about the Z-axis, and the tilt directions (the rotation directions about the X- and Y-axes), and a direction of the plane perpendicular to the Z-axis (X-Y direction). That is, the fine adjustment stage 11 has six degrees of freedom. A center slider 12 serving as an X-Y transfer stage (or coarse adjustment stage) has the fine adjustment stage 11 on it and is so arranged as to be movable in the X-Y direction perpendicular to the electron optical axis (Z-axis). An X-Y transfer stage as shown in FIG. 5 is preferably used as the center slider 12. The center slider 12 shown in FIG. 5 comprises a vacuum air guide and linear motor. Referring to FIG. 5, the center slider 12 comprises a bottom plate 12b and a column member 12s. Below the bottom plate 12b, bearings are arranged on a stage base 15 to face each other. Inside the column member 12s, an X movable guide 14x and a Y movable guide 14y are sandwiched by similar bearings. The X movable guide 14x and Y movable guide 14y are arranged in the shape of a cross. The center slider 12 can move smoothly along the side surface of the Y movable guide 14y and the upper surface of the stage base 15 in the X direction by moving the X movable guide 14x in the X direction by an X-direction linear motor 301x. The center slider 12 can move smoothly along the side surface of the X movable guide 14x and the upper surface of the stage base 15 in the Y direction by moving the Y movable guide 14y in the Y direction by a Y-direction linear motor 301y. The fine adjustment stage 11 will be described in detail with reference to FIGS. 1 to 3. The fine adjustment stage 11 has a cage structure surrounding the center slider 12 and has apertures 111x and 111y, through which the X movable guide 14x and Y movable guide 14y extend in a non-contact manner. Six electromagnet I cores 120 (120x, 120y, 120y, 120z, 120z, and 120z) are fixed at the distal end (lower end) of the fine adjustment stage 11. Electromagnet E cores 120′ (120x′, 120y′, 120y′, 120z′, 120z′, and 120z′) are fixed on the bottom plate 12b to correspond to the electromagnet I cores 120, respectively. The fine adjustment stage 11 is driven with six degrees of freedom by six electromagnetic actuators each comprising the electromagnet I core 120 and electromagnet E core 120′. More specifically, the three sets of electromagnetic actuator components 120z and 120z′ generate a driving force in the Z direction, the two sets of electromagnetic actuator components 120y and 120y′ generate a driving force in the Y and θ directions, and the one set of electromagnetic actuator components 120x and 120x′ generate a driving force in the X direction. An arrangement for driving the fine adjustment stage 11 with six degrees of freedom is not limited to this arrangement. Various arrangements may be adopted instead. A linear motor or the like may be adopted as an electromagnetic actuator in place of an electromagnet. The adoption of a non-contact electromagnetic actuator as described above for use in driving the fine adjustment stage 11 prevents a driving reaction force from appearing upon driving of the fine adjustment stage 11, and contributes to solving a problem of dust generation. The non-energized I cores 120 are attached to the fine adjustment stage 11, and the E cores 120′ each including a coil are attached to the center slider 12. This arrangement has the advantage in that heat transfer to the fine adjustment stage 11 is remarkably reduced and that the fine adjustment stage 11 has no trailing wires. Such an electromagnetic actuator is excellent in that it generates a relatively large thrust, consumes relative little power, and generates no leakage magnetic field in a non-energized state. The electromagnets 120 and 120′ are coated with multiple electromagnetic shields of, e.g., permalloy to avoid any variation in magnetic field. In addition, the electromagnets 120 and 120′ are spaced apart from the reduction electron optical system 4 by a sufficient distance to avoid being affected by the leakage magnetic field from the reduction electron optical system 4. More specifically, the electromagnets 120 and 120′ are desirably located on the opposite sides of the barycenter of the center slider 12 (or the driving center in the Z direction) in the Z direction. A substrate holder 105 for holding the wafer 5 and reflection mirrors 101x and 101y for position measurement are mounted on the upper surface of the fine adjustment stage 11. The reflection mirrors 101x and 101y are irradiated with laser light beams 102x and 102y from substrate surface laser interferometers 103 (103x, 103y, 103y′, 103xp, and 103yp; only 103x is shown in FIG. 1 for illustrative convenience), thereby measuring the X and Y positions of the fine adjustment stage 11 with reference to, e.g., the inner wall of a chamber 100. The substrate surface laser interferometers 103 are fixed on, e.g., the sample chamber 100. The reflection mirrors 10x and 101y are also irradiated with laser light beams 102y′, 102xp, and 102yp from the substrate surface laser interferometers 103 (103y′, 103xp, and 103yp), thereby measuring rotation in the θ (rotation about the Z-axis) and tilt (rotation about the X- and Y-axes) directions. Measurement points (the irradiation positions of the laser light beams) are desirably located in the vicinity of the surface on which the wafer is mounted. The position, in the Z direction, of the fine adjustment stage 11 can be measured by an optical sensor 190 which uses non-photosensitive light. Measurement values (of rotation in the θ direction (rotation about the Z-axis) and, as needed, rotation about X- and Y-axes) obtained by the substrate surface laser interferometers 103 are supplied to the deflector 6 for electron beams, and the tracks (irradiation positions) of electron beams are corrected in accordance with the position and posture of the wafer 5 on the basis of the supplied measurement values. If high-frequency vibrations occur in the fine adjustment stage 11, measurement values from the substrate surface laser interferometers 103 are preferably supplied to the deflector 6 through a band-limiting filter (e.g., a low-pass filter) 150 to prevent measurement values including vibration components from being supplied to the deflector 6. In addition to the correction by the deflector 6, at least one of rotation in the θ0 direction (rotation about the Z-axis), rotation about the X-axis, and rotation about the Y-axis of the fine adjustment stage 11 can be corrected by controlling the electromagnetic actuator components 120 and 120′ on the basis of measurement results from the substrate surface laser interferometers 103. Moreover, if no high-frequency vibrations occur in the fine adjustment stage 11, measurement values may selectively bypass the filter. Reflection mirrors 201x and 201y are arranged on the side surface of the bottom plate 12b of the center slider 12, and the X and Y positions of the center slider 12 (coarse adjustment stage) are measured by coarse adjustment system laser interferometers 203 (203x and 203y; only 203x is shown in FIG. 1 for illustrative convenience). Reference numerals 202x and 202y denote measurement axes (the optical paths of laser light beams) of the coarse adjustment system laser interferometers 203x and 203y, respectively. If the center slider 12 may greatly move about the Z-axis, a measurement axis 202y′ (and a corresponding coarse adjustment system laser interferometer 203y′) may be added for measurement in the θ direction. Measurement values obtained by the coarse adjustment system laser interferometers 203 are supplied to a fine adjustment stage controller 20. Displacement sensors 220 (220x, 220y, and 220y′; only 202x is shown in FIG. 1 for illustrative convenience) are provided to measure a relative movement, in the X, Y, and θ directions, between the center slider 12 and the fine adjustment stage 11. Each displacement sensor 220 preferably comprises an electrostatic capacitance sensor, encoder, or the like. However, a sensor of any other type may be employed. The displacement sensors 220 are desirably arranged in the vicinity of the electromagnets 120x and 120y so as to correctly measure the gaps between the electromagnets 120 and 120′ without any phase delay. The controller 20 sends command values to the electromagnet E cores 120′ each constituting an electromagnetic actuator for driving the fine adjustment stage 11 and sends command values to the linear motors 301x and 301y which drive the center slider 12, on the basis of measurement values obtained by the coarse adjustment system laser interferometers 203 and displacement sensors 220. With this operation, the fine adjustment stage 11 is controlled in the X and Y directions (and θ direction, as needed). The controller 20 determines a command value in, e.g., the following manner. (1) The controller 20 determines command values to be sent to the linear motors 301x and 301y to drive the center slider 12, on the basis of measurement values from the coarse adjustment system laser interferometers 203. (2) The controller 20 determines command values to be sent to the electromagnet E cores 120′ each constituting an electromagnetic actuator for driving the fine adjustment stage 11, on the basis of measurement values (X- and Y-direction positions) from the coarse adjustment system laser interferometers 203 and measurement values (X- and Y-direction positions and, as needed, θ-direction position) from the displacement sensors 202 (e.g., on the basis of the sums of the measurement values). (3) The controller 20 corrects the non-linearity of a control system (e.g., electromagnetic actuator components 120 and 120′) on the basis of a measurement value from the displacement sensors 202. To control the fine adjustment stage 11, various other methods are available. With the above-mentioned method, the fine adjustment stage 11 is so controlled as not to be affected by the coarse adjustment stage (center slider) 12 and as to compensate for the non-linearity of the control system (particularly, an electromagnetic actuator). More specifically, in this embodiment, command values to be sent to the electromagnet E cores 120′ each constituting an electromagnetic actuator for driving the fine adjustment stage 11 are determined on the basis of measurement values from the coarse adjustment system laser interferometers 203 and measurement values from the displacement sensors 202 (e.g., on the basis of the sums of the measurement values). Measurement values from the coarse adjustment system laser interferometers 203 and measurement values from the displacement sensors 202 are obtained using points in the vicinity of the electromagnetic actuator components 120 and 120′ as measurement points. For this reason, the control gain of the control system can be set to a high value, and thus the fine adjustment stage 11 can stably and quickly be controlled. This makes it possible to draw a pattern on the wafer at high speed and high accuracy. Even if weak vibrations occur on the substrate surface (the surface on which the wafer 5 is arranged), the deflector 6 compensates for the positional shifts of respective electron beams caused by the vibrations on the basis of measurement values from the substrate surface laser interferometers 103. Therefore, a pattern can be drawn on the wafer at high accuracy. As opposed to the above-mentioned method, assume that the electromagnetic actuator components 120 and 120′ are controlled in accordance with measurement results from the substrate surface laser interferometers 103. In this case, a long distance between measurement points of the respective substrate surface laser interferometers 103 and the electromagnetic actuator components 120 and 120′ induces vibrations having various natural frequencies in the control system. For this reason, the fine adjustment stage 11 cannot stably be controlled. [Second Embodiment] In this embodiment, displacement gauges 202 are omitted. Command values to be sent to electromagnet E cores 120′ each constituting an electromagnetic actuator for driving a fine adjustment stage 11 are determined on the basis of measurement values obtained by coarse adjustment system laser interferometers 203 and measurement values obtained by substrate surface laser interferometers 103. FIG. 4 is a schematic view showing the main part of an electron beam exposure apparatus according to the second embodiment of the present invention. Note that the same reference numerals as those in the first embodiment (FIG. 1) denote the same parts. In this embodiment, a controller 20 receives measurement values (X- and Y-direction positions) obtained by the substrate surface laser interferometers 103 and measurement values (X- and Y-direction positions) obtained by the coarse adjustment system laser interferometers 203 and calculates by a computing device 21 differences between them (i.e., X- and Y-direction deviations from the measurement values from the substrate surface laser interferometers 103 and the measurement values from the coarse adjustment system laser interferometers 203). A filtering block 22 performs filtering for the calculation result so as to cancel the characteristics of a structure comprising electromagnetic actuator components 120 and 120′, the fine adjustment stage 11, reflection mirrors 101, and the like. Command values to be sent to the electromagnet E cores 120′ are corrected on the basis of the filtering result. With this operation, the gain of the control system of the fine adjustment stage 11 can be increased, and the fine adjustment stage 11 can stably be controlled at high speed. The filtering block 22 of the controller 20 has, e.g., at least one band-limiting filter whose band to be limited is variable. By adjusting the band to be limited by the filter on the basis of simulation results or experimental results, the filtering block 22 of the controller 20 can stabilize the control of the fine adjustment stage 11. If high-frequency vibrations occur in the fine adjustment stage 11, the positional relationship between the reflection mirrors 101 and the wafer (substrate) 5 cannot be guaranteed to be constant. Under the circumstances, measurement values from the substrate surface laser interferometers 103 are preferably supplied to a deflector 6 through a band-limiting filter (e.g., a low-pass filter) 150 in order to prevent measurement values including vibration components from being supplied to the deflector 6. Additionally, if no high-frequency vibrations occur in the fine adjustment stage 11, measurement values may selectively bypass the filter. [Application Example] The manufacturing process of a semiconductor device using the above-mentioned electron beam exposure apparatuses will be described next. FIG. 8 shows the flow of the whole manufacturing process of the semiconductor device. In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (exposure control data creation), exposure control data for exposure control (e.g., the on/off control of electron beams) is created on the basis of the designed circuit pattern. In step 3 (wafer manufacture), a wafer is manufactured by using a material such as silicon. In step 4 (wafer process), called a preprocess, an actual circuit is formed on the wafer by lithography using the above-mentioned electron beam exposure apparatuses in the exposure step. Step 5 (assembly), called a post-process, is the step of forming a semiconductor chip by using the wafer formed in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. After these steps, the semiconductor device is completed and shipped (step 7). FIG. 9 shows the detailed flow of the above-mentioned wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern is drawn on the wafer using the above-mentioned electron beam exposure apparatuses. In step 17 (development), the exposed wafer is developed. In step 18 (etching), the resist is etched except for the developed resist image. In step 19 (resist removal), an unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer. According to the present invention, for example, a pattern can be drawn on a substrate at high speed and high accuracy or a substrate stage can stably be controlled in addition to this. As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims. |
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049884751 | summary | FIELD OF THE INVENTION The invention relates to a device and a method for checking the axial retention force on a peripheral rod of a fuel assembly of a nuclear reactor. BACKGROUND OF THE INVENTION The fuel assemblies of water-cooled nuclear reactors, such as pressurized-water nuclear reactors, comprise a framework in which fuel rod of great length are disposed in order to form a bundle. The framework comprises spacer grids which are spaced relative to one another along the length of the assembly and connected together by guide tubes. Each of the spacer grids comprises an assembly of cells each intended to receive a fuel rod and disposed in a uniform network, generally with squared mesh. At the level of each of the cells intended to receive a fuel rod, the spacer grids comprise means for gripping the pencil, while also ensuring both transverse retention and longitudinal retention of this rod. These gripping means generally consist of bosses projecting inwards relative to the walls of the cell of the grid and of springs consisting of resilient elements formed in the metal of certain walls of the cells of the grid or, alternatively, connected to these walls. When a new fuel assembly is charged in the nuclear reactor, it has mechanical and physical characteristics which are in accordance with the manufacturing and design standards which are defined or calculated so that the assembly can fulfill its function under the operating conditions of the reactor without suffering any excessive damage during a specific number of operating cycles. Bearing in mind the irradiation of the materials, the mechanical characteristics of the constituents of the reactor evolve but remain within specific limits ensuring safety of operation. In particular, with regard to the fuel assemblies, the spring and boss assemblies distributed in a uniform manner in the cells of the grids must retain mechanical characteristics and, in particular, strength and resilience characteristics which are sufficient to ensure effective retention of the fuel rods during a long operating period of the reactor. However, in order to improve safety and performance in nuclear reactors, it has been considered that it was desirable to check, periodically, the efficiency of the means for gripping the fuel rods in the assemblies in the core of the reactor. This checking must be performed during a discharging and refueling operation of the nuclear reactor, the assemblies being placed in a storage pool under a certain depth of water which makes it possible to ensure the biological protection of the operators responsible for the checking. A purely visual examination performed, for example, using video means, does not make it possible to detect those fuel rods whose gripping has become insufficient and, in particular, those rods on which is exerted an axial retention force which no longer makes it possible to ensure effective retention of the rod during operation of the reactor. In fact, in this case, the rod may be caused to vibrate by the passage of the cooling fluid of the reactor, such that the rod which has been caused to vibrate is liable to suffer breakage. In this case, the pellets of uranium disposed in the sheath of the rod are dispersed in the primary shell of the nuclear reactor and cause high levels of contamination in this primary shell. A device described in U.S. Pat. No. 4,265,010 is known, which makes it possible to replace, in correct position, those fuel rods which have undergone a certain axial slide. This device comprises two parallel plates, the gap between which may be varied by means of a displacement control device. One of the plates rests on an end joining piece of the assembly and the other plate, comprising a centering dish, rests under the end of the rod whose upward displacement inside the assembly is to be ensured in order to replace it in correct position. However, such a device does not make it possible to measure the gripping and longitudinal retention force on the rod in order to determine whether there is a risk of displacement of and damage to the rod during refueling of the assembly in the nuclear reactor. Patent EP-A-0,l46,804 describes a remotely controlled device for lifting fuel rods. The fuel rods are displaced so as to cause the support points of the sheath to pass over the gripping means above the grid of the assembly in order to inspect possible defects in the sheath by video means. This device does not make it possible directly to measure the axial retention force on the fuel rod. Moreover, the device, which is awkward to use, can be used only at the level of the lower joining piece of the assembly and does not make it possible to lower the rods back into their initial position. Moreover, it is desirable to be able to perform checks on the assemblies without having to remove their end joining pieces; this operation is possible only in respect of specially designed assemblies and, in any case, requires a complicated work tool and procedure. It is thus necessary to limit checking to the peripheral rods of the assembly which are the most stressed and the most likely to have gripping defects after a certain residence time in the operating reactor. In particular, devices are known which comprise a means for axial pushing on an end of a rod and means for measuring the pushing force on the rod which may be operated and activated remotely. However, such devices are not designed to perform precise measurements. SUMMARY OF THE INVENTION The invention is a device for checking the axial retention force on a peripheral rod of a fuel assembly of a nuclear reactor inside the framework of the assembly, comprising a plurality of spacer grids retaining the fuel rods in a uniform network in transverse directions and in the axial direction of the rod by virtue of gripping means associated with the cells of the grid in which the rods are inserted, checking being performed remotely and under a certain depth of water in a fuel assembly storage pool, by virtue of the device which comprises: a rod of great length on which is mounted a means for support and displacement which is movable in an axial direction of the rod and in two directions perpendicular to this axial direction, PA1 a device for pushing axially on a longitudinal end of the rod carried by the means for support and displacement, consisting of a fork comprising an end notch for its engagement on a shoulder of an end plug of the rod, which fork is fixed on an element which is movable in the vertical direction in a guide means fixed on the means for support and displacement, and of at least one support fork on a face of a corresponding end joining piece of the fuel assembly, which fork is fixed on the means for support and displacement, the vertical displacement of the movable element being provided by a remote control means, PA1 means for measuring the axial pushing force on the rod and the amplitude of the axial displacement of the rod under the effect of the pushing action, disposed at the upper level of the storage pool, and PA1 at least one video camera carried by the means for support and displacement in order to provide an image of a zone in the vicinity of the end of the rod on which a pushing action is being exerted, this device being relatively simple to use and making it possible remotely to obtain a precise measurement of the axial retention force on the fuel rod. To this end, the movable element consists of a sliding shaft on which is machined a rack of vertical direction, the remote control means consisting of a ball remote control whose flexible movable element is connected to the end of a rack engaging with a drive pinion driving the displacement of the rack and the movable element by means of at least one pinion. The invention also relates to a checking method implementing the device according to the invention. |
claims | 1. A sample cross section observation method, where a gas ion beam emitted from an ion source capable of generating at least two or more kinds of gas ions with different mass numbers is irradiated onto a sample, comprising the steps of:irradiating a gas ion having a relatively large mass number among at least the two or more kinds of gas ions, so as to form a roughly vertical cross section to the surface of a sample; andirradiating a gas ion having a relatively small mass number onto the cross section to be observed. 2. The method of claim 1, wherein, for cross sectional observation, the ion with a relatively small mass number is irradiated at a lower current than a maximum current used for irradiating the ion with a relatively large mass number. 3. The method of claim 1, further comprising the steps of:simultaneously generating at least two kinds of gas ions by the ion source;mass-separating at least the two kinds of gas ions with different mass number from each other and irradiating a gas ion beam having a relatively large mass number onto a sample to process a roughly vertical cross section to the sample surface; andchanging mass-separating conditions to irradiate a gas ion beam having a relatively small mass number onto the cross section to be observed. 4. The method of claim 1, wherein the ion having a relatively large mass number is a gas ion containing at least any one of argon, xenon, krypton, neon, oxygen, and nitrogen, while the ion having a relatively small mass number is either a hydrogen gas ion or a helium gas ion, or a mixed gas ion. 5. An ion beam machining and observation method, where a gas ion beam emitted from a gas field ion source having a vacuum chamber and a gas supply mechanism to introduce gas into the vacuum chamber and generating gas ions in the vacuum chamber is irradiated onto a sample, and where the gas supply mechanism includes at least two gas introduction systems, each system having a gas cylinder, a gas volume control valve, and a stop valve, and a gas switching control unit, comprising:switching, by the gas switching control unit, a kind of gas introduced into the vacuum chamber by the stop valve of each system and setting gas pressure conditions for the vacuum chamber by the gas volume control valve of each system; andforming a pyramid structure of atoms at an apex of an emitter tip of the gas field ion source when the gas switching control unit switches a kind of gas being introduced into the vacuum chamber by the stop valve of each system. 6. The ion beam machining and observation method according to claim 5,wherein the gas switching control unit can switch between a gas ion beam used for machining the sample and a gas ion beam used for observing the sample, and the gas ion beam of neon, argon, krypton or xenon is used for machining the sample. 7. The ion beam machining and observation method according to claim 5,wherein the gas switching control unit can switch between the kind of a gas ion beam used for machining the sample and the kind of a gas ion beam used for observing the sample, and the gas ion beam of neon, argon, krypton or xenon is used for machining the sample. 8. The ion beam machining and observation method according to claim 7,wherein the gas switching control unit switches to a hydrogen or helium ion beam on observing the sample. 9. The ion beam machining and observation method according to claim 5, further comprising:setting conditions of the amount of gas volume introduced into the vacuum chamber by a needle valve of each system; andregulating, by a needle valve of the gas introduction system, an amount of gas volume flowing into the vacuum chamber. 10. The ion beam machining and observation method according to claim 9, wherein the gas supply mechanism includes a first gas introduction system which has a first gas tube connected between the vacuum chamber and a first needle valve and which introduces the kind of gas ion beam used for machining the sample, and a second gas introduction system which has a second gas tube connected between the vacuum chamber and a second needle valve and which introduces the kind of gas ion beam used for observing the sample. 11. An ion beam machining and observation method, where a gas ion beam emitted from a gas field ion source having a vacuum chamber and a gas supply mechanism to introduce gas into the vacuum chamber and generate gas ions in the vacuum chamber is irradiated onto a sample, and where the gas supply mechanism includes at least two gas introduction systems, each system having a gas cylinder, a gas volume control valve, and a stop valve, and a gas switching control unit, comprising:forming a pyramid structure of atoms at an apex of an emitter tip of the gas field ion source; andevaporating the pyramid structure at the apex of the emitter tip of the gas field ion source when the gas switching control unit switches the kind of gas being introduced into the vacuum chamber by the stop valve of each system. |
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050948008 | abstract | A press for compressing elongated radioactive structural elements, with the ress having a horizontal press shaft and a removable counterpunch in place of which a transfer shaft can receive a finished pressed object. The press is remotely operable, has a minimum overall length, and assures that during compression as well as insertion of the pressed object into the transfer shaft, no small particles can escape from the press line and that the unavoidable swelling of the pressed object in the axial direction has no impact upon removal of the counterpunch and insertion of the pressed object into the transfer shaft. The press ram includes several insertable press ram sections, and the cover is divided into several cover portions. The horizontal press shaft is movably disposed in the pressing direction on a mounting base between two crosspieces interconnected by tie rods. Via a displacement drive, the press shaft is brought to rest against the counterpunch for the compression process, and against the transfer shaft for the ejection process. To insert the counterpunch and remove a loaded transfer shaft, the press shaft is retracted far enough to provide a free space. |
abstract | The diagnostic device that detects a failure of a sensor. The sensor includes memory for repeatedly recording pairs of two absolute pressure values, the absolute pressure values being related to absolute pressures in the first and the second impulse lines, respectively. A processor repeatedly computes, from a prescribable number of pairs of the two absolute pressure values, a correlation value representative of the correlation between the two absolute pressure values. The processor can also compare correlation values to at least one correlation threshold value, and generate a diagnostic output depending on the result of the comparison. It is possible to derive the absolute pressure values from one differential pressure measurement and one absolute pressure measurement. |
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claims | 1. A transmission electron microscope comprising:a spin-polarized electron source;a spin rotator for rotating spin polarization of an electron beam emitted from the spin-polarized electron source;an optical system for irradiating a sample with the electron beam emitted from the spin-polarized electron source;a detector for detecting an electron that has passed through the sample; anda biprism disposed between the sample and the detector. 2. The transmission electron microscope according to claim 1, wherein the spin-polarized electron source is a photo cathode. 3. The transmission electron microscope according to claim 1, wherein the spin rotator includes two spin rotators, and at least one of the two spin rotators is a Wien filter type spin rotator. 4. The transmission electron microscope according to claim 1, further comprising an image processing/analysis system which receives an output signal of the detector and analyzes molecular structure or magnetization direction of the sample. 5. The transmission electron microscope according to claim 1, further comprising control means for adjusting the spin-polarized electron beam, the optical system, or the biprism, based on an output signal of the detector. 6. The transmission electron microscope according to claim 1, further comprising:a screen used as the detector; andmeans for adjusting a position of the sample and an angle with respect to an irradiating electron beam, based on a luminance signal obtained on the screen. 7. The transmission electron microscope according to claim 1, wherein Fourier transform is used to analyze an output signal of the detector. 8. The transmission electron microscope according to claim 1, further comprising:adjustment means for adjusting strength of the spin rotator; andan image processing/analysis system for analyzing molecular structure direction or magnetization direction of the sample by processing an output signal of the detector, the output signal being obtained by changing the strength of the spin rotator to change direction of the spin polarization of the electron beam and irradiating the sample with the electron beam. |
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summary | ||
abstract | The invention relates to a method of generating a two-level pattern for lithographic processing by multiple beamlets. In the method, first a pattern in vector format is provided. The vector format pattern is then converted into a pattern in pixmap format. Finally, a two-level pattern is formed by application of error diffusion on the pixmap format pattern. |
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description | This patent application is a continuation of international application no. PCT/US2011/052440, filed Sep. 21, 2011, which application claims the benefit of U.S. provisional patent application Ser. No. 61/477,699, filed on Apr. 21, 2011. The entire disclosure of the applications are incorporated herein by reference as if set forth in their entireties. This disclosure generally relates to separating debris from water and, more particularly, to filters or traps for collecting debris in the flow stream of an Emergency Core Cooling System of a nuclear power plant. Emergency Core Cooling Systems (ECCS) of nuclear power plants typically include strainers (e.g., screens or other coarse filters) designed for preventing large debris generated by a Loss of Coolant Accident (LOCA) from reaching the ECCS pumps and/or components located downstream of the ECCS pumps. For some ECCS strainers, the holes in the strainer's surface material may range from 0.035 inch diameter holes up to 0.125 inch diameter holes, depending on plant-specific conditions. Although most debris may be stopped by an ECCS strainer, there may be “fine” debris that is small enough to flow through the ECCS strainer, even after a debris bed is formed on the surface of the ECCS strainer. If there is an excess of the fine debris and/or if the debris is of the wrong size and/or type, the debris could damage the ECCS pumps and/or increase the head loss of the system, which could cause insufficient flow of cooling water inside the reactor. This is not allowed to happen for safe operation of a nuclear power plant. More specifically, a nuclear reactor is typically contained in a containment building, and if a LOCA in the form of a high energy pipe explosion were to occur, the generated debris would fall or be washed down to the basement of the containment building where a pool of water would form. Some of the fine debris in the pool of water may be in the form of fibrous insulation that falls off of piping and other components within the containment building during the LOCA. The pool supplies the ECCS pumps with the water needed to keep the reactor cool and to operate water sprays that condense the steam inside the containment's closed atmosphere. As the ECCS pumps receive water from the pool, water in the pool is drawn through the ECCS strainers. Some of the fine debris that is suspended in the water will flow through the ECCS strainers and reach components downstream of the ECCS strainers, such as valves, pumps, spray nozzles, the reactor vessel, etc. Damage to the downstream components and/or blockage of recirculation in the reactor vessel may occur if too much fine debris passes through the ECCS strainers. In accordance with one aspect of this disclosure, there is a desire to collect a sufficient quantity of fine debris (e.g., fibrous debris) that would otherwise flow through the ECCS strainers, while at the same time limiting any head loss for the ECCS pumps. One aspect of this disclosure is the provision of a debris trap in which filter media is arranged to at least partially define both filtration and bypass flowpaths that are in fluid communication with one another. At least initially, each of the filtration and bypass flowpaths are open, and the filtration and bypass flowpaths have relatively low and relatively high head loss, respectively. In one example, the debris trap is operative so that flow through the debris trap may passively, and typically gradually, transition from the filtration flowpaths to the bypass flowpath in response to the filter media collecting increasing amounts of debris. More specifically, initially substantially all of the flow may be through the filtration flowpaths, and thereafter the filtration flowpaths may become substantially obstructed so that substantially all of the flow is through the bypass flowpath. In accordance with one aspect of this disclosure, a plurality of filtration flowpaths are at least partially defined by the filtration media of the debris trap. For each filtration flowpath of a substantial number of the plurality of filtration flowpaths, the filtration flowpath extends through both first and second portions of the filtration media, so that the first and second portions of the filtration media are arranged in series in the filtration flowpath. The bypass flowpath extends between the first and second portions of the filtration media, and along each of the first and second portions of the filtration media. The debris trap is operative for automatically, passively decreasing flow through the plurality of filtration flowpaths and increasing flow through the bypass flowpath in response to the filtration media collecting increasing amounts of the debris. In one aspect, the debris trap may include first and second filtration partitions that are in opposing face-to-face configuration with respect to one another, wherein the first filtration partition comprises the first portion of the filtration media, and the second filtration partition comprises the second portion of the filtration media. Additional filtration partitions may also be included. In one example, one or more of the debris traps may be used in an ECCS of a nuclear power plant, so that the water in the ECCS would initially flow at least primarily through the filtration flowpaths, and the filter media may collect debris from the water. In response to the head loss in the filtration flowpaths increasing because of the debris accumulating on and/or in the filter media, an increased proportion of the water in the ECCS would flow through the bypass flowpath(s) in a manner that seeks to assure that there is not too much head loss for the ECCS pumps. The debris trap may be positioned upstream of one or more strainers in the flowpath of the ECCS, and the debris trap may extend at least partially around the strainer(s). The debris trap may be in the form of, or otherwise include, a plurality of debris trap modules that extends at least partially around the strainer(s). Alternatively, the debris trap(s) may be in any other suitable position, or they may be put to any other suitable use. One aspect of this disclosure is the provision of a method of separating debris from water in an ECCS flowpath of a nuclear power plant. In this regard, a debris trap may be positioned in the ECCS flowpath, so that the ECCS flowpath is simultaneously in fluid communication with both a bypass flowpath and a plurality of filtration flowpaths. The plurality of filtration flowpaths may be at least partially defined by filtration media of the debris trap. For each filtration flowpath of the plurality of filtration flowpaths, the filtration flowpath may extend from upstream of the filtration media to downstream of the filtration media. For each filtration flowpath of a substantial number of the plurality of filtration flowpaths, the filtration flowpath may extend through both first and second portions of the filtration media, so that the first and second portions of the filtration media are arranged in series in the filtration flowpath. The bypass flowpath may be at least partially defined by the filtration media. The bypass flowpath may extend between the first and second portions of the filtration media, and along each of the first and second portions of the filtration media. The water may be caused to flow along the ECCS flowpath and through the debris trap so that the plurality of filtration flowpaths initially have a lower head loss than the bypass flowpath, and the filtration media collects increasing amounts of the debris. In response to the filtration media collecting increasing amounts of the debris, flow through the plurality of filtration flowpaths is automatically, passively, gradually decreased, and flow through the bypass flowpath is automatically, passively, gradually increased. In accordance with one aspect of this disclosure, since the flow through the debris trap may gradually transition from being primarily through the filtration flowpaths to being primarily through the bypass flowpath, the debris trap may be characterized as operating in numerous different modes and thereby providing multimodal debris trapping or filtration. The foregoing presents a simplified summary of some aspects of this disclosure in order to provide a basic understanding. The foregoing summary is not an extensive summary of the disclosure and is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The purpose of the foregoing summary is to present some concepts of this disclosure in a simplified form as a prelude to the more detailed description that is presented later. Other aspects of this disclosure will become apparent from the following. Exemplary embodiments of this disclosure are described below and illustrated in the accompanying figures, in which like numerals refer to like parts throughout the several views. The embodiments described provide examples and should not be interpreted as limiting the scope of the invention. FIGS. 1-3 schematically illustrate a debris trap 10, and in FIG. 1 the debris trap is shown in combination with conventional components of an ECCS of a nuclear power plant, in accordance with a first embodiment of this disclosure. In the following, a discussion of conventional ECCS features of the first embodiment will be followed by a discussion of the debris trap 10 of the first embodiment. The ECCS includes a conventional pipe collector or sump chamber 12 defined in and/or below a conventional basement floor 14 of a containment building. Although the sump chamber 12 is shown in the form of a sump pit in FIGS. 1 and 4, the sump chamber may be replaced by a suction pipe or any other suitable connection to the ECCS pumps. A conventional, plate-like, sump top cover 16 is be mounted to the floor 14 and closes the top of the sump chamber 12, except that a central drain hole 18 extends through the sump cover and is in fluid communication with the sump chamber. A strainer 22, such as a conventional ECCS strainer, is mounted in a conventional manner to the sump top cover 16 and/or to any other suitable structure, so that the interior of the strainer is in fluid communication with the drain hole 18. Water may flow from the outside of the strainer 22, through the filtration media of the strainer, and then downwardly through the drain hole 18. According to some embodiments, when the pool of fluid is of sufficient depth to allow, the strainer 22 may be supported above the pool floor on a filter box 20 mounted to the sump top cover 16 so that the interior of the filter box is in fluid communication with the drain hole 18. As schematically illustrated by four arrows in FIGS. 1 and 4, water may flow from the outside of the filter box 20, through the filtration media of the filter box, and then downwardly through the drain hole 18. The filter box 20 may be omitted. As shown in FIG. 1, the strainer 22 may be a stacked-disk type of strainer, the filter box 20 may be characterized as being the bottom disk of the stacked-disk strainer, and a core, or the like, of the stacked-disk strainer may be in fluid communication with the drain hole 18. The strainer 22 may be any suitable conventional strainer, and examples of conventional strainers are disclosed in U.S. Pat. No. 5,759,399, U.S. Pat. No. 5,935,439, U.S. Pat. No. 6,491,818 and US 2088/0223779. The strainer 22 may be more generally referred to as a filter, and it may be more specifically referred to as a course filter, as discussed in greater detail below. The drain hole 18, filter box 20 and strainer 22 may be concentrically arranged with respect to another, although other arrangements are also within the scope of this disclosure. Multiple strainers 22 may be placed on top of one filter box 20. The outer surface of the strainer 22 may be defined by perforated metal sheets, wire screens, or any other suitable structure. The holes in the structures defining the outer surface of the strainer 22 may range from 0.035 inch diameter holes up to 0.125 inch diameter holes, depending on the plant-specific conditions. The strainer 22 may be any suitable conventional strainer or strainer array, or the like. As one example, the strainer 22 may be a Sure-Flow® Brand strainer available from Performance Contracting, Inc. of Lenexa, Kans. When present, the filter box 20 may be in the form of a fine filter, such that its outer/upstream surface is for capturing debris 40 that is finer (i.e., smaller) than the debris captured by the more course filter/strainer 22. The filter box 20 includes an unobstructed opening or passage through which the strainer 22 out-flow communicates freely with the sump. As mentioned above, it is conventional, in the event of a LOCA, for debris to fall or be washed down to the basement floor 14 of a reactor containment building, where a pool 24 of water forms. The filter box 20 and/or strainer 22 may be characterized as being a filter assembly through which water from the pool 24 is drawn in response to operation of one or more ECCS pumps (not shown) that are downstream from and take suction from the sump chamber 12. As discussed above, although most debris may be stopped by the strainer 22, there may be “fine” debris that is small enough to flow through the strainer 22, even after a debris bed is formed on the surface of the strainer. In accordance with the first embodiment of this disclosure, the debris trap 10 is mounted upstream of both the strainer 22 and the optional filter box 20, and the debris trap is operative in a manner that seeks to both: collect any fine debris in the water that flows toward the strainer 22, and assure that there is not too much head loss for the ECCS pump(s), as will be discussed in greater detail below. In the following, a discussion of the structure of the debris trap 10 is followed by a discussion of how the debris trap may operate, all in accordance with the first embodiment. Thereafter, examples of variations to the first embodiment are discussed. The debris trap 10 includes a substantially horizontally extending, upper filtration partition 26; and outer, intermediate and inner filtration partitions 28, 30, 32 that are each upright and tubular. More specifically, the upper filtration partition 26 is substantially in the form of a planar disk, and the outer, intermediate and inner filtration partitions 28, 30, 32 are substantially in the form of concentric cylinders, although different configurations are within the scope of this disclosure, as discussed below. Generally described and as will be discussed in greater detail below in accordance with one mode of operation, each of the filtration partitions 26, 28, 30, 32 is for separating debris from the water that is in the pool 24 and flowing toward the strainer 22, including for separating and capturing debris that is finer (i.e., smaller), and preferably, but not necessarily, substantially finer, than the debris that can be captured by the strainer 22. Each filtration partition 26, 28, 30, 32 may include or be in the form of any suitable filtration media for this purpose. That is, the filtration partitions 26, 28, 30, 32 may be broadly characterized as being filtration media. More specifically, each filtration partition 26, 28, 30, 32 may include or be in the form of perforated sheet metal, wire screens, mesh, steel wool, filtration grills, filtration panels and/or any other suitable filter media. For example, the holes in the structures defining the outer surfaces of the filtration partitions 26, 28, 30, 32 may have diameters of less than about 0.125 inches, or less than about 0.035 inches, depending on the plant-specific conditions. The filtration media of the filtration partitions 26, 28, 30, 32 may be self-supporting and/or each of the filtration partitions may include a frame, framework, lattice and/or any other suitable structures for supporting and/or reinforcing the filtration partition. For example and in accordance with the first embodiment, the filtration partitions 26, 28, 30, 32 would be adapted so that they would withstand a LOCA in the form of a high energy pipe explosion, and thereafter function as intended. In some situations the filtration partitions 26, 28, 30, 32 may be adapted so as to intrinsically have the needed strength and/or the filtration partitions may be associated with other reinforcing or protective structures so that the filtration partitions in combination with the other structures have sufficient strength. When present, the filter box 20 may be constructed of the same or similar materials as the filtration partitions 26, 28, 30, 32. In accordance with the first embodiment, the debris trap 10 is upstream of the filter box 20 and strainer 22, although in some alternate embodiments, the positions may be reversed, and, in still other alternate embodiments (for example, where screening out large debris is not required), the debris trap 10 may be utilized independently of the filter box 20 and/or strainer 22. More specifically, the outer, intermediate and inner filtration partitions 28, 30, 32 extend around the filter box 20 and strainer 22; and the upper filtration partition 26 is positioned above the drain hole 18, filter box 20, strainer 22, intermediate filtration partition 30 and inner filtration partition 32. Even more specifically, the filtration partitions 26, 28, 30, 32 may be concentrically arranged with respect to the drain hole 18, filter box 20 and strainer 22. The tubular outer and inner filtration partitions 28, 32 are substantially downwardly closed by virtue of the lower ends or edges thereof being in substantially close proximity to the sump cover 16 or floor 14. More specifically, the lower ends or edges of the outer and inner filtration partitions 28, 32 may be mounted to or otherwise abutting the sump cover 16 or floor 14. The outer and inner filtration partitions 28, 32 are spaced apart from one another so that a downwardly closed (e.g., substantially closed) and upwardly open tubular cavity 34 is defined between the outer and inner filtration partitions. Referring to FIG. 3, the tubular cavity 34 may be cylindrical. The intermediate filtration partition 30 is axially offset/only partially overlapping with respect to the outer and inner filtration partitions 28, 32. More specifically, the intermediate filtration partition 30 extends into the tubular cavity 34 that is between the outer and inner filtration partitions 28, 32. The tubular intermediate filtration partition 30 is downwardly open by virtue of its lower end or edge being spaced apart from, and positioned above, the sump cover 16 or floor 14. The tubular intermediate filtration partition 30 protrudes outwardly, upwardly from the tubular cavity 34. The upper end of the tubular intermediate filtration partition 30 is obstructed by the upper filtration partition 26. For example, the periphery of the upper filtration partition 26 may be fixedly connected to, or otherwise abutting, the annular upper end or edge of the intermediate filtration partition 30. Referring to FIG. 3, each of the outer, intermediate and inner filtration partitions 28, 30, 32 are spaced apart from one another so that a horizontal, radial distance D1 is defined between adjacent ones of the outer, intermediate and inner filtration partitions. In the first embodiment, each of the radial distances D1 may be about four inches, and the inner filtration partition 32 may be similarly spaced apart from the filter box 20 and strainer 22 by about four inches. Referring to FIG. 1, the lower end or edge of the intermediate filtration partition 30 is spaced apart from the sump cover 16 or floor 14 so that an upright, or more specifically vertical, distance D2 is defined therebetween. In the first embodiment, the distance D2 may be about eight inches. Different dimensions are within the scope of this disclosure. For example, the dimensions may depend on the plant-specific conditions. The filtration partitions 26, 28, 30, 32 may be mounted in any suitable manner, such as by using structural members, fasteners, welding and/or any other suitable features or techniques. For example, structural members (not shown) may be mounted to and extend downwardly from the lower end or edge of the intermediate filtration partition 30, and these structural members may extend to the sump cover 16 and/or floor 14, for supporting the intermediate filtration partition 30. Notwithstanding, a majority, such as a vast majority, of the space between the lower end or edge of the intermediate filtration partition 30 and the adjacent sump cover 16 and/or floor 14 is open, such as by not being obstructed by any of the supporting structural members, so that a midstream segment of a bypass flowpath 36 extends around the lower end or edge of the intermediate filtration partition. In accordance with the first embodiment, the bypass flowpath 36 is an open flowpath that is intended to always remain open. The bypass flowpath 36 is schematically illustrated in each of FIGS. 1 and 4 by a pair of arrows with shanks formed with alternating long and short dashes. As shown, the bypass flowpath 36 extends around, or at least past, the upper ends or edges of the outer and inner filtration partitions 28, 32; along each of the outer, intermediate and inner filtration partitions 28, 30, 32; and around the lower end or edge of the intermediate filtration partition 30. At least a portion of an upstream segment of the bypass flowpath 36 may be characterized as consisting essentially of a cylindrical area that is defined between an upper cylindrical portion of the inner surface of the outer filtration partition 28 and a lower cylindrical portion of the outer surface of the intermediate filtration partition 30 that are in opposing face-to-face relation with one another. At least a portion of a midstream segment of the bypass flowpath 36 may be characterized as consisting essentially of a cylindrical area that is defined between a lower cylindrical portion of the inner surface of the outer filtration 28 partition and a lower cylindrical portion of the outer surface of the inner filtration partition 32 that are in opposing face-to-face relation with one another. In addition, the midstream segment of the bypass flowpath 36 may be characterized as being partially defined by the sump cover 16 or floor 14. At least a portion of a downstream segment of the bypass flowpath 36 may be characterized as consisting essentially of a cylindrical area that is defined between a lower cylindrical portion of the inner surface of the intermediate filtration partition 30 and an upper cylindrical portion of the outer surface of the inner filtration partition 32 that are in opposing face-to-face relation with one another. In addition, the downstream segment of the bypass flowpath 36 may be characterized as being partially defined by the upper filtration partition 26. In addition to at least partially defining the bypass flowpath 36, each of the filtration partitions 26, 28, 30, 32 may be characterized as at least partially defining filtration flowpaths 38 of the debris trap 10. Segments of the filtration flowpaths 38 are schematically illustrated in each of FIGS. 1 and 4 by numerous relatively small arrows that each have a curved shank, and the segments of the filtration flowpaths respectively extend through the holes in the filtration partitions 26, 28, 30, 32. For example, the upper filtration partition 26 defines generally axial filtration flowpaths 38 that extend generally axially downwardly through the upward filtration partition. In contrast, the outer, intermediate and inner filtration partitions 28, 30, 32 each define at least segments of generally radial filtration flowpaths 38 that extend generally radially inwardly through one or more of the outer, intermediate and inner filtration partitions. As more specific examples regarding flow through the debris trap 10: each of the generally radial filtration flowpaths 38 that is located at an elevation above the upper ends or edges of the outer and inner filtration partitions 28, 32 may extend solely through the intermediate filtration partition 30; each of the generally radial filtration flowpaths 38 that is located at an elevation below the lower end or edge of the intermediate filtration partition 30 may extend through both of the outer and inner filtration partitions 28, 32; and each of the generally radial filtration flowpaths 38 that is located at elevations between the upper ends or edges of the outer and inner filtration partitions 28, 32 and the lower end or edge of the intermediate filtration partition 30 may extend through each of the outer, intermediate and inner filtration partitions 28, 30, 32. Further regarding flow through the debris trap 10, each filtration flowpath 38 extending through only one of the filtration partitions 26, 28, 30, 32 may be characterized as providing a single stage of filtration, each filtration flowpath 38 extending through two of the filtration partitions may be characterized as providing two stages of filtration, and each filtration flowpath 38 extending through three of the filtration partitions may be characterized as providing three stages of filtration. A greater or lesser number of filtration partitions and stages of filtration may be provided, as discussed in greater detail below. In accordance with the first embodiment, the debris trap 10 is configured so that, at least initially, each of the bypass and filtration flowpaths 36, 38 is open, and, as compared to one another, the bypass and filtration flowpaths have relatively high and low head loss, respectively. For example the sizes of the holes in the filtration partitions 26, 28, 30, 32 and the spacing between the filtration partitions and other components of the ECCS are discussed above. The head loss is also a function of the volume of the flow through the debris trap 10. The differences between head loss in the bypass and filtration flowpaths 36, 38, and the manner of providing the differences, may vary depending on the plant-specific conditions. An example of aspects of operating the debris trap 10 after a LOCA will be described in the following, with reference to FIG. 1 and in accordance with the first embodiment of this disclosure. After a sufficient pool 24 of water forms, one or more operating ECCS pumps receive water from the sump chamber 12 so that water flows through the debris trap 10 toward the filter box 20 and strainer 22. Typically, the filtration partitions 26, 28, 30, 32 are initially substantially clear of debris, such that the bypass and filtration flowpaths 36, 38 have relatively high and relatively low head loss, respectively. As a result, a majority or substantially all of the flow through the debris trap 10 is by way of the filtration flowpaths 38. As a result of the flow of water through the filtration flowpaths 38, any debris 40 that is in the water and larger than a predetermined size is respectively collected by the outer/upstream surfaces of the filtration partitions 26, 28, 30, 32. The collected debris 40 is schematically illustrated by stippling in FIG. 1. As the filtration partitions 26, 28, 30, 32 continue to collect debris 40, namely more and more relatively small debris over time, the head loss through the filtration flowpaths 38 increases. As a result and over time, the volume of flow through the filtration flowpaths 38 decreases, and the volume of flow through the bypass flowpath 36 increases. This transition of flow from the filtration flowpaths 38 to the bypass flowpath 36 typically occurs gradually over time in response to the filtration partitions 26, 28, 30, 32 accumulating more and more debris 40 over time. In accordance with the first embodiment, the filtration partitions 26, 28, 30, 32 collect the debris in a manner that reduces the quantity of debris that bypasses the ECCS strainer 22. The outer, intermediate and inner filtration partitions 28, 30, 32 are spaced apart from one another and adjacent components of the ECCS in a manner that seeks to ensure that the bypass flowpath 36 remains open continually. In contrast, the accumulating debris collected by the filtration partitions 26, 28, 30, 32 continues to reduce the volume of flow through the filtration flowpaths 38 by increasingly obstructing the filtration flowpaths and, thereby, increasing the head loss through the filtration flowpaths. In response to the head loss in the filtration flowpaths 38 increasing because of the debris 40 accumulating on and/or in the filter media of the filtration partitions, the proportion of the water in the ECCS flowing through the bypass flowpath 36 increases in a manner that seeks to assure that there is not too much head loss for the ECCS pumps. In accordance with one aspect of this disclosure, the typically gradual transition of flow from the filtration flowpaths 38 to the bypass flowpath 36 may be characterized as being passive since, for example, it occurs automatically without requiring that any conventional valves, dampers and/or the like be operated. In accordance with one aspect of this disclosure and for at least a substantial period of time, the bypass and filtration flowpaths 36, 38 remain in fluid communication with one another in a manner that facilitates the gradual, passive transition of flow from the filtration flowpaths to the bypass flowpath. On the other hand, in some scenarios the filtration partitions 26, 28, 30, 32 may each eventually become fully clogged, obstructed or closed by the debris 40 in a manner such that the filtration flowpaths 38 may be characterized as being nonexistent, such that the bypass flowpath 36 eventually is not in fluid communication with the filtration flowpaths, since they are nonexistent. In accordance with one aspect of this disclosure, since the flow through the debris trap 10 may gradually transition from being primarily through the filtration flowpaths 38 to being primarily through the bypass flowpath 36, the debris trap may be characterized as operating in numerous different modes and thereby providing multimodal debris trapping or filtration. For example, the capturing of the debris 40 by the filtration partitions 26, 28, 30, 32 may be staggered, such that the rate at which the inner filtration partition 32 accumulates debris may initially be relatively low as compared to the other filtration partitions 26, 28, 30. The rate at which the inner filtration partition 32 accumulates debris may increase after the other filtration partitions 26, 28, 30 become sufficiently obstructed so that water flows through the upstream and intermediate segments of the bypass flowpath 36, and at least some of the water flowing through the upstream and intermediate segments of the bypass flowpath flows through the inner filtration partition rather than continuing through the downstream segment of the bypass flowpath. Whereas only a few of the modes of flow through the debris trap 10 have been described very specifically in the foregoing, those of ordinary skill in the art will understand that there may be numerous different modes and, thereby, multimodal debris trapping or filtration. On the other hand, in some scenarios the debris trap 10 may not be required to accumulate very much fine debris 40, such that there may not be such a gradual transition of flow from the filtration flowpaths 38 to the bypass flowpath 36. At least partially reiterating from above, the debris trap 10 is operative to passively collect and hold a finite amount of the debris 40. Water is drawn through the filtration partitions 26, 28, 30, 32 of the debris trap 10 in response to operation of one or more of the ECCS pumps which are downstream of the ECCS strainer 22. Initially, the water flows toward the debris trap 10 from all directions, and the water meets very low or no flow resistance through the filtration flowpaths 38 while they are free of the debris 40. As the filtration partitions 26, 28, 30, 32 trap more and more suspended debris 40, the flow resistance increases through the filtration flowpaths 38, depending upon the flow rates and quantities and types of debris trapped in the filtration partitions. As flow resistance through the filtration flowpaths 38 increases, the resistance to flow through the filtration partitions 26, 28, 30, 32 will be higher than the flow resistance required to force the water through the open bypass flowpath 36. In accordance with the first embodiment, the debris trap 10 seeks to avoid causing a high resistance (head loss) in the flow to, or block flow to, the ECCS strainer 22 by leaving open the bypass flowpath 36. In accordance with one aspect of this disclosure, the debris trap 10 is not necessarily intended to stop all debris 40 from reaching the ECCS strainer 22; rather, the debris trap seeks to capture enough of the debris to attain an acceptable overall performance of the ECCS. The filter media of the filtration partitions 26, 28, 30, 32 may vary depending upon design conditions and filtering efficiencies. For example, the surfaces of the filtration partitions 26, 28, 30, 32 (e.g., the surfaces of the filtration media of the filtration partitions) may vary from relatively flat surfaces of a single material to complex corrugations, brushes, composite materials and/or panels. The distance between opposing filtration partitions 28, 30, 32 is a variable that may be used to control how much flow resistance is acceptable as a maximum in the event that flow through the filtration partitions 28, 30, 32 becomes totally blocked. That is, the debris 40 is captured by opposing filter media (i.e., by opposite ones of the filtration partitions 28, 30, 32) due to flow therethrough until such time the flow resistance forces the water to flow along the bypass flowpath 36 between the opposing filter media rather than through the opposing filter media. In accordance with one aspect of this disclosure, the bypass flowpath 36 is an alternate, unfiltered, free flowpath that is used when the head loss becomes too great for flow through the filtration flowpaths 38. Simultaneously with the operation of the debris trap 10 (i.e., flow through the filtration flowpaths 38 and/or flow through the bypass flowpath 36), the filter box 20 and strainer 22 function to collect debris that is of predetermined size(s) and passes through the debris trap, such as by way of the bypass flowpath 36. Arrows shown extending into the filter box, and downwardly from the drain hole 18 schematically illustrate some of the flow. As mentioned above, the filter box 20, when present, may be constructed of the same materials as the filtration partitions 26, 28, 30, 32, such that the filter box functions to provide another stage of filtration for collecting the debris 40. The quantity and/or effective surface area of filter boxes 40 may be increased to increase the overall efficiency in trapping the debris 40 before the debris reaches the ECCS strainer 22. This may be beneficial when there is a finite quantity of the debris 40 such that the addition of filter boxes may mean the difference between meeting the overall performance criteria or not. Similarly, there may be more than one of the strainers 22 within the debris trap 10. Alternatively, in some alternate embodiments, the positions of the debris trap 10 and the combination of the filter box 20 and strainer 22 may be reversed, so that the debris trap is downstream of the filter box 20 and strainer 22. Additionally, in some alternate embodiments (for example, where screening out large debris is not required), the debris trap 10 may optionally be used without the filter box 20 and/or strainer 22. Other variations are also within the scope of this disclosure. For example, each of the disk-shaped filtration partition 26 and tubular filtration partitions 28, 30, 32 may be in a variety of different shapes, such as, for example and not limitation, in the shape of a polygon, a polygon with rounded corners, or any other suitable shape in a top plan view thereof. For example, numerous details of the debris trap 10 may depend upon plant-specific conditions. As another example, the debris trap 10 may include a lesser or greater number of the filtration partitions 26, 28, 30, 32, and the filtration partitions may be in a variety of different configurations. For example, the inner filtration partition 32 may be omitted and/or the upper filtration partition 26 may be larger so that an additional filtration partition may extend downwardly from the upper filtration partition and around the outer filtration partition 28. In one example where there are filtration partitions arranged in series in a filtration flowpath, the heights of the filtration partitions may decrease in the upstream direction in the filtration flowpath. As another example, the upper filtration partition 26 could be omitted or replaced with a solid metal plate in some possible scenarios. As a more specific example, FIG. 4 is like FIG. 1, except for showing the pool 24′ having a lower depth, and with such a sustained lower level of water it may be inconsequential for the upper filtration partition 26 to be omitted or replaced with a solid metal plate. A wide variety of depths of the pools 24, 24′ are within the scope of this disclosure. In accordance with one aspect of the first embodiment, it may be preferred for the pools 24, 24′ to remain full enough so that the water may flow over the upper ends or edges of the outer and inner filtration partitions 28, 32 in the event that the filtration flowpaths 38 through one or both of the outer and inner filtration partitions are closed off by the debris 40. Other variations are also with the scope of this disclosure. For example, the debris trap 10 may be characterized as being a module, and a number of the modules may be arranged in series or parallel. As a more specific example, a second embodiment of this disclosure is like the first embodiment, except for variations noted and variations that will be apparent to those of ordinary skill in the art. Due to the similarity, components of the second embodiment that are identical, similar and/or function in at least some ways similarly to corresponding components of the first embodiment have reference numbers incremented by one hundred. A group of debris trap modules 110 of the second embodiment is shown in FIGS. 5 and 6, and discussed in the following. Whereas the bypass flowpath 36 (FIGS. 1 and 4) of the first embodiment has vertical segments that are arranged in series and alternate between upward and downward flow, each of the bypass flowpaths 136 of the second embodiment has horizontal segments that are arranged in series and alternate back and forth. Alternatively, a debris trap or group of debris trap modules could include both of the vertical and horizontal types of bypass flowpaths. As another example, the bypass flowpaths may extend obliquely or be in any other suitable configuration. The group of debris trap modules 110 extends at least partially around, or substantially around, the filter box 120 and strainer 122 that are above the sump top cover 116 and upstream of the pipe collector or sump chamber 112 defined in and/or below the basement floor 114. As shown in FIGS. 5 and 6, there is a pair of front debris trap modules 110 that are arranged side by side, opposite side debris trap modules that may each extend along the entire length of the group of debris trap modules, and a pair of rear debris trap modules 110 that are arranged side by side. In FIG. 6, the portions of the debris trap modules 110 that are hidden from view (below the portion of the upper filtration partition 126 that is not cut away) are schematically illustrated with dashed lines. In accordance with the second embodiment, all of the debris trap modules 110 share the same upper filtration partition 126, and the single upper filtration partition closes the upper end of a convolute tubular structure that is formed by the group of debris trap modules 110. Alternatively, each of the debris trap modules 110 may be fitted with a separate, dedicated upper filtration partition. For each of the debris trap modules 110, each of its outer, intermediate and inner filtration partitions 128, 130, 132 is upright and generally planar, or more specifically substantially planar, although each may have corrugations or any other suitable shapes. In accordance with the second embodiment, each of the outer, intermediate and inner filtration partitions 128, 130, 132 has opposite upper and lower ends or edges, and opposite side ends or edges that respectively extend between the upper and lower ends or edges. For each of the outer, intermediate and inner filtration partitions 128, 130, 132, its lower end or edge is in substantially close proximity to the sump cover 116 or floor 114. More specifically, the lower ends or edges of each of the outer, intermediate and inner filtration partitions 128, 130, 132 may be mounted to, or otherwise abut, the sump cover 116 or floor 114. For each of the outer, intermediate and inner filtration partitions 128, 130, 132, its upper end or edge is in substantially close proximity to the upper filtration partition 126. More specifically, the upper ends or edges of each of the outer, intermediate and inner filtration partitions 128, 130, 132 may be mounted to, or otherwise abut, the upper filtration partition 126. The group of debris trap modules 110 includes upright structural members 160 that each have a lower end or edge that is in substantially close proximity to the sump cover 116 or floor 114. More specifically, the lower ends or edges of each of the structural members 160 may be mounted to, or otherwise abut, the sump cover 116 or floor 114. For each of the structural members 160, its upper end or edge is in substantially close proximity to the upper filtration partition 126. More specifically, the upper ends or edges of each of the structural members 160 may be mounted to, or otherwise abut, the upper filtration partition 126. For each of the outer, intermediate and inner filtration partitions 128, 130, 132, each of its opposite side ends or edges is in substantially close proximity to a respective structural member 160. More specifically, the opposite side ends or edges of the outer, intermediate and inner filtration partitions 128, 130, 132 may be mounted to, or otherwise abut, the respective structural member 160. For each of the debris trap modules 110 of the second embodiment, its outer and inner filtration partitions 128, 132 are spaced apart from one another and mounted to opposite ends of the same structural member 160 so that an upwardly and downwardly closed (e.g., substantially closed) and laterally open cavity is defined between the outer and inner filtration partitions. For each of the debris trap modules 110, the intermediate filtration partition 130 is offset/only partially overlapping with respect to the outer and inner filtration partitions 128, 132. More specifically, the intermediate filtration partition 130 extends into the laterally open cavity and protrudes laterally, outwardly from the laterally open cavity. Referring to the lower right portion of FIG. 6 for example, for each of the debris trap modules 110, each of the outer, intermediate and inner filtration partitions 128, 130, 132 are spaced apart from one another so that a horizontal distance D3 is defined between adjacent ones of the outer, intermediate and inner filtration partitions. Also, for each of the debris trap modules 110, the side ends of the intermediate filtration partition 130 are offset from the side ends of the outer and inner filtration partitions 128, 132 by about the same horizontal distance D3. In the second embodiment, each of the horizontal distances D3 may be about four inches, and the inner filtration partition 132 may be similarly spaced apart from the filter box 120 and strainer 122 by about four inches. Different dimensions are within the scope of this disclosure. For example, the dimensions may depend on the plant-specific conditions. Similarly to the first embodiment, the bypass flowpath 136 of each debris trap module 110 is an open flowpath that is intended to always remain open. Two of the bypass flowpaths 136 are schematically illustrated in FIG. 6 by a pair of arrows with shanks formed with alternating long and short dashes, and segments of these two bypass flowpaths are schematically illustrated in FIG. 5. Also similarly to the first embodiment, each of the filtration partitions 126, 128, 130, 132 may be characterized as at least partially defining filtration flowpaths 138 of the debris trap modules 110. Some of the filtration flowpaths 138 are schematically illustrated in FIG. 6, and upstream segments of those same filtration flowpaths are schematically illustrated in FIG. 5, by numerous relatively small arrows that each have a curved shank. The segments of the filtration flowpaths respectively extend through the holes in the filtration partitions 126, 128, 130, 132. For example, the upper filtration partition 126 defines generally downwardly extending filtration flowpaths (not shown, but see FIGS. 1 and 4 for example), and the outer, intermediate and inner filtration partitions 128, 130, 132 each define at least segments of generally horizontal, inwardly extending filtration flowpaths 138. In accordance with the second embodiment, the group of debris trap modules 110 is configured so that, at least initially, each of the bypass and filtration flowpaths 136, 138 is open, and, as compared to one another, the bypass and filtration flowpaths have relatively high and low head loss, respectively. Referring to FIG. 6, as a result of the flow of water through the filtration flowpaths 138, any debris 140 that is in the water and larger than a predetermined size is collected by the outer/upstream surfaces of the filtration partitions 126, 128, 130, 132. The collected debris 140 is schematically illustrated by stippling in FIG. 6. As the filtration partitions 126, 128, 130, 132 continue to collect debris 140, namely more and more relatively small debris over time, the head loss through the filtration flowpaths 138 increases. As a result and over time, the volume of flow through the filtration flowpaths 138 decreases, and the volume of flow through the bypass flowpaths 136 increases. This transition of flow from the filtration flowpaths 138 to the bypass flowpaths 136 typically occurs gradually over time in response to the filtration partitions 126, 128, 130, 132 accumulating more and more debris 140 over time. As with the ECCS example in the first embodiment, over time, an increased portion of the water flows through the bypass flowpaths 136 in a manner that seeks to assure that there is not too much head loss for the ECCS pumps. Alternatively, in some alternate embodiments, the positions of the group of debris trap modules 110 and the combination of the filter box 120 and strainer 122 may be reversed, so that the group of debris trap modules is downstream of the filter box 120 and strainer 122. Additionally, in some alternate embodiments (for example, where screening out large debris is not required), the group of debris trap modules 110 may optionally be used without the filter box 120 and/or strainer 22. Other variations are also within the scope of this disclosure. For example, numerous details of the debris trap modules 110 may depend upon plant-specific conditions. In accordance with one aspect of this disclosure, provisions are made for balancing between any addition of flow resistance (or head loss) to an ECCS system and removal of fine debris from the water in the ECCS. Whereas debris traps of this disclosure have often been discussed in the context of separating debris from water in a flow stream of an ECCS of a nuclear power plant, the debris traps of this disclosure are not limited to such usage and may be put to other uses. The above examples are in no way intended to limit the scope of the present invention. It will be understood by those skilled in the art that while the present disclosure has been discussed above with reference to exemplary embodiments, various additions, modifications and changes can be made thereto without departing from the spirit and scope of the invention as set forth in the claims. |
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053512774 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. Referring to FIG. 2, after setting a cylindrical liner 11, temporary posts 14 and temporary trusses 15 are placed and a top slab liner 10 is laid on the temporary trusses 15, followed by setting of a sleeve 17 of the nuclear reactor container. Then, the cylindrical liner 11 and the top slab liner 10 are welded along a welding line 12. Subsequently, the top slab liner 10 and a sleeve 17 of the nuclear reactor container are welded together along a welding line 13. Meanwhile, a top slab steel reinforcement structure 8 (see FIG. 1) is prefabricated on the ground together with an auxiliary plate 19. The prefabricated top slab steel reinforcement structure 8 is lifted and set on the top slab liner 10. Then, a flange 16 and the sleeve 17 are welded together along a welding line 18. This welding is conducted simultaneously with the placement of concrete in the space on the outer diameter side of the auxiliary plate. After examination of the welding at the welding line 18, concrete is placed in the space defined by the integrated flange 16 and the sleeve 17, and the auxiliary plate 19. In an embodiment in which the top slab steel reinforcement structure 8 is integrated with the top slab liner 10, the top slab liner 10 serves as a reinforcer, so that the temporary trusses 15 shown in FIG. 2 can be eliminated. A further improvement in the efficiency of the construction work can be attained by integrating the top slab steel reinforcement structure 8, top slab liner 10 and the sleeve 17 of the nuclear reactor container, in advance of the installation. An embodiment which uses such an integrated structure is shown in FIG. 4. Referring to FIG. 4, H-shaped steel bars 20 are laid on the upper surface of the top slab liner 10 and are fixed to the same by welding. Then, the steel reinforcement structure 8 is assembled on the H-shaped steel bars 20 and the lower end of the steel reinforcement structure 8 is welded to the upper surfaces of the H-shaped steel bars 20, whereby the steel reinforcement structure is integrated with the top slab liner 10. The sleeve 17 and the top slab liner 10 have been welded together along a welding line 13. In this embodiment, the top slab liner 10 functions as a reinforcer, so that the temporary trusses 15 shown in FIG. 2 can be eliminated. Although each of the described embodiments employs an auxiliary plate 19 which is assembled together with the top slab steel reinforcement structure, the use of the auxiliary plate 19 is not essential. Without the auxiliary plate, the flange and the container sleeve must be welded before any concrete is poured. The use of the auxiliary plate 19, however, is preferred because the auxiliary plate stiffens the steel reinforcement structure so as to prevent deformation of this structure when the same is lifted for installation. The auxiliary plate also contributes to strengthening of the built-up nuclear reactor container. Additionally, the auxiliary plate acting as a barrier makes it possible to divide the placement of concrete whereby welding the flange and the container sleeve can be conducted on the inner diameter side of the auxiliary plate while pouring concrete into a space on the outer diameter side as shown schematically in FIG. 8. As will be understood from the foregoing description, according to the invention, the flange is formed separately from the sleeve and is joined to the latter by welding. Therefore, construction of a nuclear reactor container having a flange of a diameter greater than the inside diameter of doughnut-shaped steel reinforcement structure can be conducted without difficulty by welding the flange to the sleeve after installation of the steel reinforcement structure, thus shortening the term of the construction work. In the embodiment in which the top slab steel reinforcement structure, top slab liner and the sleeve are integrated beforehand, the efficiency of the construction work is further improved because the temporary trusses can be omitted. The installation of the above-mentioned integral structure can be facilitated by splitting the sleeve portion and the flange portion. The cylindrical auxiliary plate prevents the welding line between the sleeve and the flange from being hidden by concrete so as to make it possible to simultaneously conduct the welding and the placement of concrete on the opposite side of the auxiliary plate. The auxiliary plate also strengthens the steel reinforcement structure so as to prevent deformation of this structure when the same is lifted for installation and also contributes to strengthening of the built-up nuclear reactor container. |
042119286 | abstract | A storage unit for a quantity of radioactive material in a capsule attached to a leader by which the capsule can be moved, the unit having a straight passage through a body of radiation-shielding material within which the radioactive material can be stored, and a shutter for one end of the passage that is operable between two limits in one of which it closes the passage and in the other of which it locates a hole in register with the passage. A spring-biased tube in the passage fits in a recess around the hole for retaining the shutter in the "open" position, and this tube can be pulled back from the shutter by a fitting attached to the capsule when the capsule is stored, releasing the shutter to return to the first limit. An interlock is provided to prevent accidental opening of the shutter. |
050680820 | claims | 1. A fuel assembly for a nuclear reactor of the type in which a number of fuel rods, each constructed by filling a clad with a fuel material, are arranged in a bundle, comprising: a plurality of first fuel rods having a partial effective fuel area filled with a fuel material and having a portion in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, positioned on an axial level including a portion at which subcriticality becomes small at a period in which maintenance of reactor shut-down margin is small during a reactor operation period; and a plurality of second fuel rods having a total effective fuel area filled with a fuel material throughout an entire axial length of the clad of the fuel rod, wherein said first fuel rods are disposed in straight lines inside the bundle so as to horizontally separate said second fuel rods into a plurality of sub-bundles. a plurality of first fuel rods having a partial effective fuel area filled with a fuel material and having a portion in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, positioned on an axial level including a first section at which subcriticality becomes small at a period in which maintenance of reactor shut-down margin is small during a reactor operation period and a second section located between said first section and a lower end of the effective fuel area; and a plurality of second fuel rods having at least one partial interposed zone in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, positioned at said second section, wherein said first fuel rods are disposed inside the bundle so as to horizontally separate said second fuel rods into a plurality of sub-bundles. a plurality of first fuel rods having a partial effective fuel area filled with a fuel material and having a portion in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, positioned on an axial level including a first section at which subcriticality becomes small at a period in which maintenance of reactor shut-down margin is small during a reactor operation period and a second section located between said first portion and a lower end of the effective fuel area; a plurality of second fuel rods having at least one partial interposed zone in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, positioned at said second section; and a tube through which a moderator passes disposed in the fuel assembly, wherein said second fuel rods are arranged adjacent to the tube. 2. The fuel assembly according to claim 1, wherein said portion in which enrichment of a fissile nuclide in the clad of the fuel rod is significantly reduced, or the fissile nuclide does not exist at all, comprises an interposed zone in which enrichment of the fissile nuclide is significantly reduced or the fissile nuclide does not exist at all. 3. The fuel assembly according to claim 2 wherein said interposed zone has an axial length substantially equal to or longer than a thermal neutron diffusion length during a reactor power operation period. 4. The fuel assembly according to claim 3 wherein the axial length of said interposed zone is shorter than one-third of an axial length of the effective fuel area of said second fuel rod. 5. The fuel assembly according to claim 2, wherein said interposed zone is located at a position on an axial level so that at least a portion of said interposed zone is at distance between two-thirds and five-sixths of the length of said total effective fuel area measured from the lower end of said total effective fuel area. 6. The fuel assembly according to claim 2 wherein said interposed zone is occupied with a solid moderating material. 7. The fuel assembly according to claim 2 wherein said interposed zone is occupied with a liquid moderating material. 8. The fuel assembly according to claim 7 wherein said liquid material is water. 9. The fuel assembly according to claim 2 wherein a gas plenum is formed in said interposed zone. 10. The fuel assembly according to claim 2 wherein a depleted uranium is charged in said interposed zone. 11. The fuel assembly according to claim 2 wherein a natural uranium is charged into said interposed zone. 12. The fuel assembly according to claim 2 wherein a ceramic material suppressing neutron absorption characteristics at a final stage of a reactor operation cycle is inserted into said interposed zone. 13. The fuel assembly according to claim 12 wherein said ceramic material is a porous heat-proof ceramic. 14. The fuel assembly according to claim 2, wherein a burnable poison having a concentration of an extent such that said burnable poison will vanish at a final stage of a reactor operation cycle is contained in said interposed zone. 15. The fuel assembly according to claim 2 wherein fuel materials disposed adjacent to said interposed zone contain a burnable poison having a concentration to an extent such that said burnable poison will vanish at the final stage of the reactor operation cycle. 16. The fuel assembly according to claim 2, wherein said first fuel rods having the interposed zone are arranged in a linearly crossing pattern. 17. The fuel assembly according to claim 1 wherein said first fuel rod comprises a short fuel rod having an axial length shorter than that of said second fuel rod, said short fuel rod being constructed by removing a portion of the fuel rod existing on an axial level including a portion at which subcriticality becomes small at a period in which maintenance of reactor shut-down margin is small during a reactor operation period. 18. The fuel assembly according to claim 17 wherein a plural number of said short fuel rods are provided with an effective fuel area having an axial length ranging between one-half to five-sixth of the length of said total effective fuel area said second fuel rod. 19. The fuel assembly according to claim 17 wherein a plural number of said short fuel rods are arranged in a linearly crossing pattern. 20. The fuel assembly according to claim 17 wherein the lower end portion of said short fuel rods are arranged substantially in the same plane as the lower end portion of said second fuel rod is arranged. 21. The fuel assembly according to claim 17 wherein a power spike suppressing material is disposed above the fuel material filled in said short fuel rod. 22. The fuel assembly according to claim 1 wherein a plurality of tubes through which a moderator passes are disposed in the fuel assembly and at least one of said first fuel rods is located at an area positioned between said tubes. 23. The fuel assembly according to claim 22 wherein said lubes comprise water rods. 24. A fuel assembly for a nuclear reactor of the type in which a number of fuel rods, each constructed by filling a clad with a fuel material, are arranged in a bundle, comprising: 25. The fuel assembly according to claim 24 wherein said first section exists in an area including at least a portion ranging between two-thirds and five-sixth of the length of the effective fuel area measured upwardly from the lower end portion of the effective fuel area. 26. The fuel assembly according to claim 24 wherein an interposed member made of a material which has a significantly reduced enrichment of a fissile nuclide or in which the fissile nuclide does not exist at all is inserted into said first fuel rod at the portion in which enrichment of a fissile nuclide is significantly reduced or the fissile nuclide does not exist at all. 27. The fuel assembly according to claim 26 wherein said interposed member has an axial length substantially equal to or longer than a thermal neutron diffusion length during a reactor output power operation period. 28. The fuel assembly according to claim 27 wherein the axial length of said interposed member is shorter than one-third of an axial length of the effective fuel area of said second fuel rod. 29. The fuel assembly according to claim 26 wherein said interposed member is occupied with a solid moderator. 30. The fuel assembly according to claim 26 wherein said interposed member is occupied with a liquid moderator. 31. The fuel assembly according to claim 30 wherein said liquid moderator is water. 32. The fuel assembly according to claim 26 wherein a gas plenum is formed in said interposed member. 33. The fuel assembly according to claim 26 wherein said interposed member is occupied with a depleted uranium. 34. The fuel assembly according to claim 26 wherein said interposed member is occupied with a natural uranium. 35. The fuel assembly according to claim 26 wherein said interposed member is occupied with a ceramic material suppressing neutron absorption characteristics at a final stage of a reactor operation cycle. 36. The fuel assembly according to claim 35 wherein said ceramic material is a porous heat-proof ceramic. 37. The fuel assembly according to claim 26 wherein a burnable poison having a concentration to an extent such that said burnable poison will vanish at a final stage of a reactor operation cycle is contained in said interposed member. 38. The fuel assembly according to claim 26 wherein fuel materials disposed adjacent to said interposed member contained a burnable poison having a concentration to an extent such that said burnable poison will vanish at the final stage of the reactor operation cycle. 39. The fuel assembly according to claim 26 wherein a plural number of said first fuel rods provided with the interposed member are arranged linearly. 40. The fuel assembly according to claim 26 wherein a plural number of said first fuel rods provided with the interposed member are arranged in a linearly crossing pattern. 41. The fuel assembly according to claim 24 wherein said first fuel rod is a short fuel rod having an axial length shorter than said second of the fuel rod provided with the interposed zone and comprises a fuel rod which is provided with a removed portion on an axial level including a portion at which subcriticality is made small at a period in which maintenance of reactor shut-down margin is made difficult during the reactor operation period. 42. The fuel assembly according to claim 41 wherein a plural number of said short fuel rods are arranged linearly. 43. The fuel assembly according to claim 41 wherein a plural number of said short fuel rods are arranged in a linearly crossing pattern. 44. The fuel assembly according to claim 41 wherein the lower end of said short fuel rod lies substantially in the same plane as the lower end of said second fuel rod provided with the interposed zone lies. 45. The fuel assembly according to claim 41 wherein a power spike suppressing member is disposed above a top portion of a fuel material filled in said short fuel rod. 46. The fuel assembly according to claim 2, wherein said interposed zone comprises an output power spike suppressing member comprising at least one of depleted uranium, natural uranium, a burnable poison, and a non-burnable oxide material. 47. The fuel assembly according to claim 46, wherein said interposed zone comprises a burnable poison. 48. The fuel assembly according to claim 46, wherein said interposed zone comprises a non-burnable oxide material. 49. The fuel assembly according to claim 24, wherein said interposed zone comprises an output power spike suppressing member selected from the group consisting of depleted uranium, natural uranium, a burnable poison, and a non-burnable oxide material. 50. The fuel assembly according to claim 49, wherein said interposed zone comprises a burnable poison. 51. The fuel assembly according to claim 49, wherein said interposed zone comprises a non-burnable oxide material. 52. A fuel assembly for a nuclear reactor of the type in which a number of fuel rods, each constructed by filling a clad with a fuel material, are arranged in a bundle, comprising: 53. The fuel assembly according to claim 1, further comprising a tube through which a moderator passes, said tube disposed in a center portion of the bundle. 54. The fuel assembly according to claim 16, further comprising a tube through which a moderator passes, said tube disposed at the intersection of said linearly crossing shape. 55. The fuel assembly according to claim 24, further comprising a tube through which a moderator passes, said tube disposed in a center portion of the bundle. 56. The fuel assembly according to claim 40, further comprising a tube through which a moderator passes, said tube disposed at the intersection of said linearly crossing shape. 57. The fuel assembly according to claim 55, wherein said tube comprises a water rod. 58. The fuel assembly according to claim 52, wherein said tube comprises a water rod. 59. The fuel assembly according to claim 2, wherein the central portion of said interposed zone is located at a distance of about three-fourths of the length of said total effective fuel area from the lower end of said total effective fuel area. |
claims | 1. A method for operating a pressurized water reactor operation, comprising: preparing a fuel assembly including a fresh fuel rods that operate for a preset first operation time and once-used fuel rods that operate for a second operation time longer than the first operation time; creating an operation schedule of the pressurized water reactor based upon the first operation time of the fresh fuel rods and the second operation time of the once-used fuel rods; and operating the pressurized water reactor by repeating the operation schedule,wherein the operating the pressurized water reactor by repeating the operation schedule includes: operating the pressurized water reactor for a first cycle of a predetermined period of time by using a fuel assembly including a first set of the fresh fuel rods in a first region and a first set of the once-used fuel rods in a second region; after the first cycle operation is completed, discharging the first set of the once-used fuel rods to the outside of the pressurized water reactor; loading, after the first cycle operation is completed, a first portion of the first set of the fresh fuel rods into the second region in the fuel assembly; discharging a second portion of the first set of fresh fuel rods to the outside of the pressurized water reactor; loading a second set of the fresh fuel rods into the first region and operating the pressurized water reactor for a second cycle of a preset period of time; loading, after the second cycle operation is completed, a second set of fresh fuel rods into the second region; and a third set of the fresh fuel rods into the first region and operating the pressurized water reactor for a third cycle of a preset period of time. 2. The method of claim 1, wherein the second fuel rods have uranium enrichment that allows a long period of operation of 24 months. 3. The method of claim 2, wherein the uranium enrichment ranges from 4.7 to 4.95 wt. %. 4. The method of claim 1, wherein the first cycle and the second cycle are 24 months, and the third cycle is 18 months. 5. The method of claim 1, wherein the first cycle, the second cycle, and the third cycle form one operation schedule, and the pressurized water reactor operates by repeating the one operation schedule. |
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summary | ||
claims | 1. A radiation detector comprising:a scintillator panel having a scintillator layer; anda photoelectric conversion panel having a support substrate, a light receiving element, and a switching element,wherein:the light receiving element faces the scintillator layer,the photoelectric conversion panel has flexibility,the scintillator layer is sealed with a moisture-proof material,the moisture-proof material includes a first moisture-proof layer and a second moisture-proof layer,the first moisture-proof layer is provided on a surface of the scintillator panel which is opposite to a surface of the scintillator panel facing the photoelectric conversion panel, anda rigid plate is provided on a surface of the photoelectric conversion panel which is opposite to a surface of the photoelectric conversion panel facing the scintillator panel, the rigid plate functioning as the second moisture-proof layer. 2. The radiation detector according to claim 1, wherein at least one of the first moisture-proof layer and the second moisture-proof layer is an electrically conductive layer. 3. The radiation detector according to claim 1, wherein the rigid plate is a bottom plate of a housing which houses the radiation detector. 4. A radiation detector comprising:a scintillator panel having a scintillator layer; anda photoelectric conversion panel having a support substrate, a light receiving element, and a switching element,wherein:the light receiving element faces the scintillator layer,the photoelectric conversion panel has flexibility,the scintillator layer is sealed with a moisture-proof material,the moisture-proof material includes a first moisture-proof layer and a second moisture-proof layer,a rigid plate is provided on a surface of the scintillator panel which is opposite to a surface of the scintillator panel facing the photoelectric conversion panel, the rigid plate functioning as the first moisture-proof layer, andthe second moisture-proof layer is provided on a surface of the photoelectric conversion panel which is opposite to a surface of the photoelectric conversion panel facing the scintillator panel. 5. The radiation detector according to claim 4, wherein at least one of the first moisture-proof layer and the second moisture-proof layer is an electrically conductive layer. 6. The radiation detector according to claim 4, wherein the rigid plate is a top plate of a housing which houses the radiation detector. |
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054105765 | claims | 1. A new and improved container for disposing of low level radioactive waste and its detection comprising, in combination: a container having a cylindrical side wall of an enlarged diameter and an enlarged height, the container having a base plate with its exterior periphery coupled to the lower edge of the side wall, the container also having an aperture through the center of the base plate with an upwardly extending cylindrical support of a reduced diameter and shortened height extending upwardly from the aperture of the base plate; a liner formed of a flexible material, the liner being configured to fit interiorly of the side wall with its upper edges extending over the upper edge thereof, the liner having a lower face adapted to be positioned on the interior face of the base plate, the liner also having an upwardly extending cylindrical extension adapted to be positioned over the upwardly extending interior cylinder of the container; a holder having a base, side wall and a cut-out in the exterior wall of the holder, and being positioned on the exterior surface of the cylindrical side wall of the container adjacent the lower extent thereof for holding a meter, the meter being of the type having a probe for radioactive material positionable upwardly through the aperture of the base plate into the interior cylinder; and a lid in a circular configuration with a downwardly extending flange positionable over the exterior periphery of the container at its upper edge. a container having a cylindrical side wall of an enlarged diameter and an enlarged height, the container having a bottom wall with its exterior periphery coupled to the lower edge of the side wall, the container also having an aperture through the center of the bottom wall with an upwardly extending cylindrical support of a reduced diameter and shortened height extending upwardly from the aperture of the bottom wall; and a liner formed of a flexible material, the liner being configured to fit interiorly of the side wall with its upper edges extending over the upper edge thereof, the liner having a lower face adapted to be positioned on the interior face of the bottom wall, the liner also having an upwardly extending cylindrical extension adapted to be positioned over the upwardly extending interior cylinder of the container. a lid in a circular configuration with a downwardly extending flange positionable over the exterior periphery of the container at its upper edge. a holder having a base, side wall on the exterior surface of the cylindrical side wall of the container adjacent the lower extent thereof for holding a meter, the meter being of the type having a probe for radioactive material positionable upwardly through the aperture of the base plate into the interior cylinder. a cut-out in the exterior side wall of the holder for viewing the meter when supported in the holder. 2. A container for disposing of low level radioactive waste and its detection comprising: 3. The container as set forth in claim 2 and further including: 4. The container as set forth in claim 2 and further including: 5. The container as set forth in claim 4 and further including: |
061335770 | claims | 1. A method for producing extreme ultra-violet light, the method comprising: flowing a gas at a supersonic velocity by flowing the gas through a converging-diverging nozzle; directing a radiated energy beam into the flowing gas to stimulate emission of extreme ultra violet light from the gas; and capturing a substantial portion of the gas so as to mitigate contamination caused by the gas. providing a vacuum chamber; flowing a gas through a converging-diverging nozzle at a supersonic velocity into the vacuum chamber; directing a radiated energy beam into the flowing gas to stimulate emission of extreme ultra violet light from the gas; collecting the extreme ultra-violet light and focusing the extreme ultra-violet light so as to facilitate photolithography with the extreme ultra-violet light; capturing a substantial portion of the gas so as to mitigate contamination of the collecting and focusing optics thereby, the gas being captured by a diffuser which reduces a velocity of the gas and increases a pressure thereof; and recycling the gas captured by the diffuser to the nozzle such that the captured gas is repeatedly flowed at supersonic velocity and stimulated into emitting extreme ultra-violet light. a converging-diverging nozzle for accelerating a gas to form a supersonic jet of gas; and a radiated energy source for providing a radiated energy beam, the radiated energy beam being incident upon the supersoric jet of gas and stimulating extreme ultra-violet light emission from the jet of gas; and a diffuser into which the supersonic jet of gas is directed, the diffuser inlet comprising a diffuser configured to reduce the velocity of the gas and to increase the pressure thereof; wherein the nozzle and the diffuser inlet are configured to utilize gas dynamics properties of the supersonic jet of gas to direct debris formed during interaction of the electron beam and the gas jet into the inlet and thus mitigate contamination of system optical components thereby. a compressor for compressing gas captured by the diffuser; a heat exchanger for cooling the gas captured by the diffuser; and wherein compressing and cooling the gas captured by the diffuser facilitates recycling of the gas. a vacuum chamber; a nozzle for flowing a gas at a supersonic velocity into the vacuum chamber; a source of radiated energy for directing a radiated energy beam into the flowing gas to stimulate emission of extreme ultra-violet light from the gas; collecting and focusing optics for collecting the extreme ultra-violet light and for focusing the extreme ultra-violet light; a diffuser for capturing a substantial portion of the gas so as to mitigate contamination of the collecting and focusing optics; and a recycling system for providing gas captured by the diffuser to the nozzle, such that the gas is repeatedly used to generate extreme ultra-violet light. 2. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing a gas at a supersonic velocity through a converging-diverging nozzle having a generally rectangular cross-section. 3. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing a gas at a supersonic velocity through a converging-diverging nozzle having a generally rectangular cross-section and also having a length substantially greater than a width of the cross-section. 4. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing a gas at a supersonic velocity through a converging-diverging nozzle having an aspect ratio of approximately 10 to 1. 5. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises expanding the gas so as to substantially decrease a temperature of the gas, and thus substantially increase a density of the gas, so as to enhance the emission of extreme ultra-violet light from the gas. 6. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing a noble gas at a supersonic velocity. 7. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing, in part, at least an argon gas, helium gas, or xenon gas at a supersonic velocity. 8. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing the gas at a velocity of approximately Mach 3. 9. The method as recited in claim 1 wherein the step of flowing a gas at a supersonic velocity comprises flowing the gas through a vacuum. 10. The method as recited in claim 1 wherein the steps of flowing a gas at a supersonic velocity, directing a radiated energy beam into the flowing gas, and capturing a substantial portion of the gas are performed substanially within a vacuum. 11. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing an electron beam into the flowing gas. 12. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing a laser beam into the flowing gas. 13. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing a microwave beam into the flowing gas. 14. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing the radiated energy beam proximate the converging-diverging nozzle. 15. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing the radiated energy beam through the flowing gas in a manner which mitigates absorption of the extreme ultra-violet light back into the flowing gas. 16. The method as recited in claim 1 wherein the step of directing a radiated energy beam into the flowing gas comprises directing the radiated energy beam through the flowing gas proximate a surface of the flowing gas so as to reduce a distance that the extreme ultra-violet light must travel through the flowing gas, thus mitigating absorption of the extreme ultra-violet light. 17. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises receiving the substantial portion of the gas within a diffuser, the diffuser being configured to reduce the velocity of the gas and to increase the pressure of the gas. 18. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises receiving the substantial portion of the gas within a diffuser having a cross-section approximate to the cross-section of the converging-diverging nozzle. 19. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises receiving the substantial portion of the gas within a diffuser, and pumping a substantial portion of the gas, which is not received within the diffuser, via a vacuum pump, so as to facilitate recycling of the gas. 20. The method as recited in claim 1 further comprising the step of recycling the gas, such that captured gas is repeatedly flowed at a supersonic velocity and stimulated into emitting extreme ultra-violet light. 21. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises converting a substantial portion of a kinetic energy of the gas into pressure, so as to facilitate recycling of the gas. 22. The method as recited in claim 1 further comprising the steps of compressing the portion of gas captured and removing heat from the gas catured, so as to facilitate recycling of the gas. 23. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises flowing the gas over at least one knife edge to reduce the velocity of the gas. 24. The method as recited in claim 1 wherein the step of capturing a substantial portion of the gas comprises flowing the gas over a plurality of concentric, generally rectangular knife edges. 25. The method as recited in claim 1 wherein the method for producing extreme ultra-violet light is used in the production of a semiconductor component. 26. A method for producing extreme ultra-violet light in a photolithography system for production of semiconductor components, the method comprising: 27. The method as recited in claim 26, wherein the semiconductor component comprises a transistor. 28. A recycling gas target jet for producing extreme ultra-violet light comprising: 29. The recycling gas target jet as recited in claim 28 wherein the converging-diverging nozzle has a generally rectangular cross-section and an aspect ratio of approximately 10 to 1. 30. The recycling gas target jet as recited in claim 28 wherein the converging-diverging nozzle is configured so as to expand the gas so as to substantially decrease a temperature of the gas, and thus substantially increase a density of the gas, so as to enhance the emission of extreme ultra-violet light from the gas. 31. The recycling gas target jet as recited in claim 28 wherein the gas comprises a noble gas. 32. The recycling gas target jet as recited in claim 28, wherein the gas comprises at least an argon gas, helium gas, or xenon gas. 33. The recycling gas target jet as recited in claim 28 wherein the converging-diverging nozzle comprises a converging-diverging nozzle configured to flow the gas at a velocity at approximately Mach 3. 34. The recycling gas target jet as recited in claim 28 further comprising a vacuum chamber within which the gas flows. 35. The recycling gas target jet as recited in claim 28 wherein the radiated energy source comprises an electron beam source. 36. The recycling gas target jet as recited in claim 28 wherein the radiated energy source comprises a laser. 37. The recycling gas target jet as recited in claim 28 wherein the radiated energy source comprises a microwave source. 38. The recycling gas target jet as recited in claim 28 wherein the radiated energy source is configured to direct the radiated energy beam proximate the converging-diverging nozzle. 39. The recycling gas target jet as recited in claim 28 wherein the radiated energy source is configured to direct the radiated energy beam through the gas in a manner which mitigates absorption of the extreme ultra-violet light back into the flowing gas. 40. The recycling gas target jet as recited in claim 28 wherein the radiated energy source is configured to direct the radiated energy beam through the flowing gas proximate a surface of the flowing gas so as to reduce a distance that extreme ultra-violet light must travel through the gas, thus mitigating absorption of the extreme ultra-violet light. 41. The recycling gas target jet as recited in claim 28 further comprising a diffuser for substantially capturing the gas. 42. The recycling gas target jet as recited in claim 28 further comprising a vacuum pump for pumping a substantial portion of the gas not received within the diffuser back to the nozzle, so as to facilitate recycling of the gas. 43. The recycling gas target jet as recited in claim 28 further comprising: 44. The recycling gas target jet as recited in claim 28 further comprising a plurality of knife edges formed proximate a diffuser to reduce the velocity of the gas and increase the pressure of the gas. 45. An extreme ultra-violet system comprising: |
claims | 1. An apparatus for determining crystalline and polycrystalline materials of an item in objects, comprising a diffraction apparatus with a collimator/detector arrangement; an X-ray source that emits a primary beam directed towards the collimation/detector arrangement; first adjustment elements for mounting the collimation/detector arrangement for adjustment both laterally and height-wise relative to the X-ray source; second adjustment elements for mounting the X-ray source for lateral adjustment; and a computer for controlling the first and second adjustment elements to move the x-ray source and collimation/detector arrangement in synchronism. 2. The apparatus according to claim 1 , wherein the collimation/detector arrangement comprises a detector, and a collimator disposed between a detector and the X-ray source, with the collimator having a conically-expanding round slot, which defines a predetermined angle and with the round slot being oriented toward the detector. claim 1 3. The apparatus according to claim 2 , wherein the collimator has a central, blind-bore-like opening, which is closed in a direction toward the detector and in which first and second detection devices are located and spaced one behind the other. claim 2 4. The apparatus according to claim 3 , wherein the first detection device detects relatively lower X-ray energies, and the second detection device detects relatively higher X-ray energies. claim 3 5. The apparatus according to claim 2 , wherein the collimator/detector arrangement is oriented such that the central bore of the collimator is directed toward the primary beam of the X-ray source. claim 2 6. The apparatus of claim 1 , wherein the object is luggage, and the x-ray source and collimator/detector arrangement are disposed on opposite sides of a conveyor for the luggage. claim 1 |
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claims | 1. A lithographic projection apparatus, comprising:a radiation system constructed and arranged to provide a beam of radiation;a support constructed and arranged to support a patterning device, the patterning device constructed and arranged to pattern the beam according to a desired pattern;a substrate table constructed and arranged to hold a substrate;a projection system constructed and arranged to project the patterned beam onto a target portion of the substrate;a base to which the support and the substrate table are mounted; anda reference frame compliantly mounted to the base, wherein the projection system comprises at least one optical element mounted on a projection frame that is compliantly mounted to the reference frame, wherein the project on system is compliantly mounted to the reference frame by at least one compliant mount, the compliant mount comprisinga T-shaped member with one of the projection system and the reference frame attach to both ends of a first elongate member of the T-shaped member and the other of the projection system and the reference frame is attached to an end of a second elongate member of the T-shaped member. 2. A lithographic projection apparatus according to claim 1, wherein an eigenfrequency of the projection frame compliantly mounted to the reference frame is between about 10 and 30 Hz. 3. A lithographic projection apparatus according to claim 1, wherein an eigenfrequency of the reference frame compliantly mounted to the base is about 0.5 Hz. 4. A lithographic projection apparatus according to claim 1, wherein the projection system is compliantly mounted to the reference frame by at least three compliant mounts. 5. A lithographic projection apparatus according to claim 1, wherein the projection system is mounted to the reference frame on nodal axes of a dominant mode of bending vibration of the reference frame or a torsional vibration of the reference frame. 6. A lithographic projection apparatus according to claim 1, where the T-shaped member has an internal first eigenfrequency that is greater than 1000 Hz. 7. A lithographic projection apparatus according to claim 1, wherein motion of the projection system relative to the reference frame is damped. 8. A lithographic projection apparatus according to claim 7, wherein the motion of the projection system relative to the reference frame is actively damped by piezoelectric actuators or Lorentz-force actuators. 9. A device manufacturing method, comprising:projecting a patterned beam of radiation onto a target portion of a layer of radiation-sensitive material at least partially covering a substrate using a projection system;supporting a reference frame, a support constructed and arranged to support a patterning device, and a substrate table constructed and arranged to hold the substrate, on a base, wherein the reference frame is compliantly mounted to the base and the projection system is mounted to the reference frame; andcompliantly mounting the projection system to the reference frame while projecting the patterned beam of radiation onto the target portion, wherein the projection system is compliantly mounted to the reference frame by at least one compliant mount, the compliant mount comprisinga T-shaped member with one of the projection system and the reference frame attached to both ends of a first elongate member of the T-shaped member and the other of the projection system and the reference frame is attached to an end of a second elongate member of the T-shaped member. 10. A method according to claim 9, wherein the projection system comprises at least one optical element mounted on a projection frame that is compliantly mounted to the reference frame and an eigenfrequency of the projection frame compliantly mounted to the reference frame is between about 10 and 30 Hz. 11. A method according to claim 9, wherein an eigenfrequency of the reference frame compliantly mounted to the base is about 0.5 Hz. 12. A method according to claim 9, wherein the projection system is compliantly mounted to the reference frame by at least three compliant mounts. 13. A method according to claim 9, wherein the projection system is compliantly mounted to the reference frame on nodal axes of a dominant mode of bending vibration of the reference frame or a torsional vibration of the reference frame. 14. A method according to claim 9, wherein the T-shaped member has an internal first eigenfrequency that is greater than 1000 Hz. 15. A method according to claim 9, wherein motion of the projection system relative to the reference frame is damped. 16. A method according to claim 15, wherein the motion of the projection system relative to the reference frame is actively damped by piezoelectric actuators or Lorentz-force actuators. |
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053032730 | description | DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 to 4 depict an apparatus for assembling a nuclear fuel assembly in accordance with an embodiment of the present invention. The apparatus, generally designated at 31, comprises a main device 32, a maintaining device or means 33 disposed adjacent to the main device 32, and a moving device or means 34 attached to the main device 32. Referring to FIGS. 1 and 2, the main device 32 includes holding means 32A having a tray 42 for holding a grid 5 thereon, and a deflecting device or means 32B for deflecting the springs 15 away from the dimple 16 opposing thereto. Roughly, the deflecting device 32B includes a frame 41, a pair of right and left guide rods 43, a rod support or a first support member 44, a tool support or a second support member 45, and drive means in the form of a hydraulic cylinder 46. The frame 41 includes an upper frame 41a, a pair of right and left side flames 41b and a pair of right and left bottom flames 41c. The tray 42 of the holding means is disposed at a central portion of the main device 32, i.e., between the right and left side flames 41b, and is supported on a top portion 51a of a vertically extending shaft 51 which is, as will be described later, constructed so as to be rotatable about its axis. Positioning members 52 are securely mounted on the corners of the upper surface of the tray 42 for positioning the grid 5 in place. In addition, a pair of horizontally-extending rail guides 53 are securely fixed to the side frames 41b at their inner faces, while a pair of sliding rails 54 are securely fixed to the side plates of the tray 42, respectively. Thus, the tray 42 is constructed so as to be movable with its rails 54 being slidably supported on the rail guides 53, respectively. Furthermore, a pair of stopper members 55 each carrying a protruding member threaded thereinto are securely fixed to the side frames 41b. These stopper members 55 are arranged so that when the tray 42 is transferred from a position adjacent to the main device 32 into a prescribed position between the frames 41c, the protruding members are respectively brought into fitting engagement with holes 56 formed in the side plates of the tray 42, to thereby stop the tray 42 in place. Furthermore, the pair of vertically extending guide rods 43 are arranged adjacent to the side frames 41b, respectively. The upper end of each guide rod 43 is fixedly secured to the upper frame 41a through a supporting sleeve 61, while the lower end of the guide rod 43 is fixedly secured to a bracket 62 which is fixed to a respective side frame 41b. The rod support 44, which is composed of an elongated rectangular plate, is arranged on the guide rods 43 for sliding vertical movement therealong. More specifically, a pair of through apertures 63 are formed in the rod support 44 at positions adjacent to the right and left ends, and each guide rod 43 is slidably inserted into a respective aperture 63 through a cylindrical sleeve 64 interposed therebetween. Furthermore, the hydraulic cylinder 46 is securely mounted on the center of the upper frame 41a with its piston rod 65a being directed downwards, and the piston rod 65a is connected at its free end to the center of the upper surface of the rod support 44. The rod support 44 carries at its lower surface a plurality of vertically downwardly extending rod members 66 arranged in line along the support 44, and each rod member 66, which has a conical-shaped lower end, is arranged so that its axis is aligned with the axis of a respective grid cell 13 in the grid 5. Thus, the rod support 44 is adapted to be moved up and down by the actuation of the hydraulic cylinder 46, and hence the rod members 66 are caused to move up and down. Additionally, the rod support 44 is provided with a pair of guide members 67 mounted on the right and left ends on the upper surface thereof. The function of these guide members will be later described. Furthermore, under the rod support 44, the tool support 45 which is comprised of a elongated rectangular plate similar to the rod support 44, is supported on the guide rods 43 for sliding vertical movement therealong. As is the case with the rod support 44, a pair of through apertures 71 are formed in the tool support 45 at positions adjacent to the right and left ends, and each guide rod 43 is slidably inserted into a respective aperture 71 through a cylindrical sleeve 72 interposed therebetween. Formed in the tool support 44 are a plurality of rod-accommodating holes 73 which have a diameter slightly larger than that of the rod member 66 and are disposed in line at such positions as to be coaxial with the axes of the grid cells 13 of the grid 5. In addition, the tool support 44 carries at its lower surface a plurality of tools or tubular members 74 arranged in line along the support 44 so as to correspond to the rod members 66. Each tool 74 is securely fixed to the lower open end of a respective hole 73 through a suitable connecting sleeve, and arranged so that its axis is aligned with the axis of a respective grid cell 13 in the grid 5. Each tool 74 has two sleeve pieces or leaves divided circumferentially thereof, and is constructed such that when the rod member 66 is inserted thereinto, the divided sleeve pieces are enlarged or spread outwards. Furthermore, attached to the rod support 44 and the tool support 45 are linkage means which associates the movement of the tool support 45 with the movement of the rod support 44 and dissociates the movement of the tool support 45 therefrom. More specifically, the linkage means includes an upwardly extending connecting rod or suspender 75, and stopper means disposed adjacent to the rod support 44 and the tool support 45 for stopping the tool support 45 in association with the movement of the rod support 44. The suspender 75 is extended through the rod support 44 to protrude upwardly therefrom, and engaging bolts 76 are threaded on the protruded end. The lower end of the suspender 75 is immovably secured to the tool support 45. Thus, when the rod support 44 is elevated by a prescribed distance from the tool support 45, the engaging bolts 76 of the suspender 75 are brought into engagement with the upper surface of the rod support 44. Therefore, when the rod support 44 is further moved upwards, the tool support 45 is also moved upwards following the movement of the rod support 44. Furthermore, the supporting bracket 62 arranged under the shaft 43 has an upper surface defining a stopping face 77 adapted to receive the lower surface of the tool support 45 to thereby prevent the tool support 45 from further moving downwardly. In the position in which the tool support 45 is stopped by the stopping face 77, the lower ends of the tools 74 carried on the tool support 45 are extended through the grid cell 13 and protruded therefrom. In addition, the rod support 44, which is caused to stop on the tool support 45, is situated so that the lower ends of the rod members 66 carried thereon are also extended through the grid cell 13 and protruded therefrom. The stopper means of the linkage means shown in FIG. 4 includes a pair of swing roller assemblies 81 each mounted on a respective side frame 41b and positioned above the stopping face 77 of the bracket 62. Each swing roller assembly 81 has an arm 82 mounted on the side frame 41b so as to be pivotable about its center in a vertical plane, and a pair of rollers 83 and 84 mounted on the upper and lower ends of the arm 82 and disposed in vertically spaced relation from each other. The swing roller assembly 81 is of such a construction that the pivotal movement of the arm 82 permits either one of the two rollers 83 and 84 to approach the rod support 44 or the tool support 45. Thus, when the upper roller 83 of the swing roller assembly 81 is brought into rolling contact with a surface 67a of the guide member 67, the swing roller assembly 81 is caused to pivot counterclockwise in FIG. 4, and the lower roller 84 is brought into contact with the end portion 45a of the tool support 45, whereby the upward movement of the tool support 45 is prevented. The maintaining device 33 shown in FIGS. 1 and 3 is provided adjacent to the holding means for maintaining the springs 15 deflected, and comprises a plurality of key members 21 each adapted to be releasably inserted in the grid cell 13 of the grid 5 for maintaining the springs 15 deflected, a key-inserting device 33a or means provided for inserting the key member 21 into a prescribed position in the grid cells of the grid 5. The key-inserting device 33a includes a key-supplying mechanism 91 or means for supplying the key member 21 into a prescribed insertion position adjacent to the grid 5, and a key-transfer mechanism or means 92 for moving the key member 21 placed in the insertion position into a prescribed position in the grid 5. The key-supplying mechanism 91 includes a cylindrical key cartridge 93 for releasably holding a plurality of key members 21, and a rotating mechanism attached to the cartridge 93 for rotating the key cartridge 93 about its axis to bring one of the key members 21 into the insertion position. The key cartridge 93 is constructed so as to be capable of holding a plurality of, e.g., thirty two key members 21 parallel to the axis of the cartridge 93. The key-transfer mechanism 92 shown in FIG. 1 comprises an actuating cylinder 94 for pushing the key member 21 held at the insertion position in the key-cartridge 93 towards the grid 5 on the holding means, a pair of push-out rollers 95 provided for moving the pushed key member 21 a predetermined distance towards the grid 5, a forwarding mechanism 100 for further moving the key-cartridge 93 towards the grid 5 to complete the insertion of the key member 21, and a pair of key-rotating mechanisms 97 provided adjacent the grid 5 for rotating the key member 21 while holding the same. The actuating cylinder 94 is provided with a generally L-shaped push-out member 94a mounted on its piston rod. The push-out member 94a is slidably supported at its one end on a shaft extending parallel to the actuating cylinder 94, and an auxiliary cylinder 94b for moving the shaft up and down is connected to the shaft, whereby when the auxiliary cylinder 94b is actuated, the push-out member 94a is pivoted about the rod of the cylinder 94 so that the other end of the push-out member 94a is moved into and out the key-cartridge 93. An actuator, not shown, is operably connected to the push-out rollers 95 through a suitable belt and pulley transmission 95a to rotate the rollers 95. The forwarding mechanism 100 comprises a sliding table 100a slidably placed on a base 100b so as to be movable towards and away from the grid 5 on the holding means, and a drive mechanism, not shown, connected to the sliding table for moving the table 100a forwards and backwards. Each of the key-rotating mechanisms 97 includes a holding member or portion 96 for holding the key member, a motor 97a for rotating the holding member through a suitable belt and pulley transmission to rotate the key member, and a suitable cylinder for moving the holding member towards and away from the grid. The holding member 96 of the key-rotating mechanism 97 disposed on the left side in FIG. 1 serves as a stopper for confirming that the insertion of the key member 21 into the prescribed position in the grid 5 is completed. Moreover, the key-rotating mechanism 97 disposed on the right side in FIG. 1 is provided with a cylinder (not shown) for moving the holding member 96 upwards and downwards. Furthermore, the moving device 34 in FIG. 1 is provided adjacent to the holding means for moving the holding means into a shifted position, to thereby allow the maintaining device 33 to insert another key member 21 in another grid cell 13 of the grid 5 to maintain other springs 15 deflected. The moving device 34 includes a sliding block 34a supported on a rail for sliding movement therealong, a suitable table 34b fixedly secured to the sliding block 34a, and a suitable drive mechanism 34c for driving the sliding block 34a to move. Furthermore, the shaft 51 fixed to the holding tray 42 is constructed so as to be rotatable about its axis by a suitable drive means accommodated in the housing on the table 34b. Thus, the holding tray 42 is rotatable or indexable by 90 degrees, to thereby permit the insertion of the key members 21 perpendicular to the aforesaid direction. Referring to FIGS. 5a to 5f, the procedures for deflecting the springs 15 in the grid cell 13 and inserting the key members 21 into prescribed positions using the aforesaid assembling apparatus will hereinafter be described. (1) First, the piston rod 65 in FIG. 1 of the hydraulic cylinder 46 is caused to move upwards to thereby move the rod support 44 to an upper position of the main device 32. In addition, the grid 5 is received on the tray 42, and is moved to the position below the tool support 45 and the rod support 44. Thus, the tool support 45 is connected to the rod support 44 through the suspender 75, and is stopped at the upper position in the main device 32. In this condition, the rod members 66 of the rod support 44 are all inserted into the upper portions of the tools 74 on the tool support 45. However, nothing is inserted in the grid cell 13 of the grid 5 yet at this stage (see FIG. 5a). (2) Then, the hydraulic cylinder 46 is actuated to cause the piston rod 65 to move downwardly to move the rod support 44 downwardly. With this procedure, the tool support 45, which is connected to the rod support 44 by the suspender 75, is caused to move downwardly by its own weight. As a result, the plurality of tools 74 on the tool support 45 are received into the grid cells 13 of the grid 5 on the tray 42 (see FIG. 5b). (3) Thereafter, the rod support 44 is further moved downwards to cause the rod members 66 to be inserted further into the tools 74 as shown in two-dot chain lines in FIG. 4. When each rod member 66 is inserted in the interior of the grid cell 13, the tool 74 accommodated in the cell 13 is enlarged, so that the springs 15 are deflected by the divided sleeve pieces of the tool 74 (FIG. 5c). (4) Subsequently, the push-out member 94a is pivoted by the actuation of the cylinder 94b so that its prescribed end is brought into a position adjacent to the key member 21 at the insertion position in the key-cartridge 93, and then the cylinder 94 is actuated, so that the key member 21 is pushed out by the push-out member 94a towards the grid 5. The key member 21 is caused to further move forwards by the actuation of the rollers 95 and the forwarding mechanism 100 until the key member 21 is stopped by the stopper 96. In this condition, the key-cartridge 93 is moved to the position indicated by the two-dot chain line in FIG. 1. With these procedures, the key member 21 is inserted in a prescribed position in the grid 5 as shown in FIG. 5d. Then, the key member 21 is rotated and moved axially by the key-rotating mechanisms 97, to thereby bring the hooks 22 of the key member 21 into engagement with the ribs 23 (see FIG. 5e). More specifically, when the key-cartridge 93 is moved to its forward position, the key-rotating mechanism 97 disposed on the right side in FIG. 1 is situated at its lower position. After the key-cartridge 93 is moved back to its rearward position, the right key-rotating mechanism 97 is moved upwards and shifted towards the other key-rotating mechanism 97, whereby the key member 21 is held at its rearward end by the holding member 96. Then, the motors 97 of both of the key-rotating mechanisms are actuated to rotate the key member 21, and the cylinder is activated to shift the key member 21 in its axial direction. (5) The hydraulic cylinder 46 is then driven to cause to the piston rod 65 to move upwards, so that the rod support 44 is elevated above the grid 5. In this situation, the upper roller 83 of the swing roller assembly 81 is brought into abutment with the surface 67a of the guide member 67 on the rod support 44, and therefore the lower roller 84 is held in abutment with the end 45a of the tool support 45 to press the same downwardly. Thus, the tool support 45 is prevented to move upwardly until the upper roller 83 is disengaged from the guide member 67. (6) When the rod members 66 are withdrawn from the grid 5, the tools 74 accommodated in the grid 5 are disengaged from the springs 15 since their sleeve pieces are restored to their original positions away from the springs 15. (7) When the rod support 44 and the tool support 45 are caused to move upwardly by a prescribed distance, the rod support 44 and the engaging bolts 76 of the suspender 75 are brought into engagement with each other to cause the tool support 45 to move upwardly, and hence the tools 74 are withdrawn from the grid 5. (8) Thereafter, the moving device 34 is operated to move the tray 42 a prescribed distance to shift the grid 5 in a direction perpendicular to the supports 44 and 45 into a next position. Then, by the actuation of the hydraulic cylinder 46, the deflecting device is again operated in a manner similar to the foregoing, to thereby deflect the springs 15, and the key cartridge 93 is rotated about its axis by a prescribed angle, to thereby move another key member 21 to the insertion position. Then, the aforesaid operations are repeatedly carried out to insert another key member 21 into the grid 5 and rotate the same to maintain the springs 15 deflected, following which the deflecting tools and the rod members are removed from the grid cells 13 in a manner similar to the foregoing. By repeating the aforesaid operations, all of the key members 21 are thus inserted in the grid 5. (9) Further, when the insertion of the key members 21 into the grid 5 from one side is completed, the holding means is actuated to rotate the tray 42 ninety degrees, and by repeating the aforesaid procedures, other key members 21 are inserted in the grid 5 in a direction perpendicular to the key members that have already been inserted. Thus, as shown in FIG. 5f, all of the springs 15 in the grid 5 are maintained deflected in a direction away from the dimples 16 opposing thereto. (10) Then, the fuel rods 6 are inserted into the respective grid cells 13, following which the key members 21 are removed from the grid 5. Thus, the fuel rods 6 are securely fixed by being urged by the springs 15 towards the dimples 16 opposing thereto. As described above, in the assembling apparatus 31 in accordance with the invention, the deflecting device comprises tools 74, rod members 66 releasably inserted in the tools 74 for sliding movement therealong, and drive means for moving the rod members to bring the same into urging engagement with the tubular member. Accordingly, the springs 15 are deflected in their proper acting direction, so that the deflecting operation can be carried out without causing any twisting or shifting to the springs 15. Furthermore, since the deflecting device includes a linkage means for associating and dissociating the movement of the rod support 44 and that of the tool support 45, the assembling apparatus is very simple in construction. Moreover, the apparatus includes the maintaining device and the moving device in addition to the deflecting device, and hence all of the operations including the insertion of the key members 21 and the indexing of the grid 5 can be automatically carried out, thereby achieving substantial reduction in working time and cost. Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. |
063242591 | abstract | A scattered-ray grid has a carrier with absorption elements arranged thereon in spaced rows which proceed essentially spoke-like relative to a grid center. Except for one or more rows which originate at the grid center, the individual rows of the scattered-ray grid, or of substantially identical grid sectors of the scattered-ray grid each originate from respectively different radii. The origin of each row is situated in an angle section, which is determined on the basis of at least two points lying on a circle, or an arc of circle, with a predetermined radius and which is divided in a predefined ratio for determining the position of the origin. The predetermined radius is incremented in a stepwise manner to define respective origins for all of the rows. |
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abstract | The invention concerns a vessel for processing, transfer, accumulation and/or transfer of material containing civilian or military origin plutonium, in the form of plutonium oxide, carbide and/or nitride. The plutonium is preferably present in a concentration not higher than a guaranteed maximum between 20 and 50% wt. in said material, possibly with other actinides such as americium, neptunium, or curium. Said material is preferably in form of powder, granulate and/or tablets. The vessel comprises a volume of 20 to 70 liters for containing said material, demarcated at least by two substantially parallel walls, these two walls being separated by a distance e between 8 and 15 cm. The invention concerns also an enclosure comprising analogous geometrically safe criticality-preventing means (bottom-catcher), a fuel production plant comprising a set of such vessels, preferably installed in a set of said enclosures, as well as a nuclear fuel production process carried out in a set of such vessels, preferably installed in a set of said enclosures. |
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claims | 1. A method for determining a charged particle beam state, comprising the steps of:extracting positively charged particles from a synchrotron;transporting the positively charged particles from said synchrotron through a nozzle and at least into a patient;imaging first photons to form a first signal, the first photons resultant from the positively charged particles transmitting through a first light emitting element on a first sheet;imaging second photons to form a second signal, the second photons emitted from a second light emitting element upon the positively charged particles traversing through the second light emitting element on a second sheet, said second sheet parallel to said first sheet and not intersecting said first sheet;determining a first vector of the positively charged particle beam path using the first signal and the second signal. 2. The method of claim 1, further comprising the steps of:positioning the first light emitting element in a beam path of the positively charged particles after the patient;positioning the second light emitting element in the beam path of the positively charged particles after the patient, said first light emitting element separated from said second light emitting element by at least one centimeter; andusing the first vector to determine an exit point of the positively charged particles from the patient. 3. The method of claim 1, further comprising the steps of:positioning the first light emitting element in a beam path of the positively charged particles prior to the patient;positioning the second light emitting element in the beam path of the positively charged particles prior to the patient, said first light emitting element separated from said second light emitting element by at least one centimeter; andusing the first vector to determine an entrance point of the positively charged particles into the patient. 4. The method of claim 2, further comprising the step of:using the first vector, during a tumor therapy session, to confirm a position of a tumor of the patient. 5. The method of claim 2, further comprising the step of:after positioning the patient relative to said nozzle in a treatment room:(1) changing a treatment plan of irradiation of a tumor of the patient using the first vector; and(2) resuming treatment of a tumor of the patient prior to the patient leaving the treatment room using said synchrotron. 6. The method of claim 2, further comprising the steps of:imaging third photons to form a third signal, the third photons emitted from a third light emitting element upon the positively charged particles passing through said third light emitting element, said third light emitting element positioned between said nozzle and the patient. 7. The method of claim 6, further comprising the steps of:imaging fourth photons to form a fourth signal, the fourth photons emitted from a fourth light emitting element upon the positively charged particles passing through said fourth light emitting element, said fourth light emitting element positioned between said nozzle and the patient;determining a second vector of the positively charged particle beam path using said third signal and said fourth signal; andusing the second vector to determine an entrance point of the positively charged particles into the patient. 8. The method of claim 7, further comprising the step of:calculating a probable path of the positively charged particles through the patient using the entrance point and the exit point. 9. The method of claim 6, further comprising the steps of:determining a position of the positively charged particles through: (1) positioning the positively charged particles along a first axis using a first pair of magnets and (2) positioning the positively charged particles along a second axis using a second pair of magnets, the first axis perpendicular to the second axis;determining a second vector of the positively charged particle beam path using the position and the third signal; andusing the second vector to determine an entrance point of the positively charged particles into the patient. 10. The method of claim 6, further comprising the step of:using a scintillation plate of a tomography detector to determine a fourth signal of a position of the positively charged particle beam in said scintillation plate; andusing said third signal and said fourth signal to determine a second measure of the exit point of the positively charged particles from the patient. 11. The method of claim 1, said step of imaging first photons further comprising the step of:determining a first measure of an intensity of the positively charged particles using a magnitude of the first signal, said first signal comprising a measure to the first photons resultant from the positively charged particles transmitting through said first light emitting element. 12. The method of claim 1, further comprising the step of:using the magnitude of the first signal related to the first photons to determine a dosage per unit time of the positively charged particles. 13. The method of claim 12, the step of imaging second photons further comprising the step of:determining a second measure of the intensity of the positively charged particles using an amplitude of the second signal, said second signal comprising a measure to the second photons resultant from the positively charged particles transmitting through said second light emitting element. 14. The method of claim 12, further comprising the step of:determining a first measure of an energy of the positively charged particles using a peak-to-peak period of a radio-frequency field applied to the positively charged particles in said synchrotron at time of extraction. 15. The method of claim 14, further comprising the step of:determining a second measure of an energy of the positively charged particles using a scintillation detector positioned in a path of the positively charged particles after the patient. 16. The method of claim 2, said first light emitting element comprising a fluorophore. 17. An apparatus for determining a charged particle beam state, comprising:a synchrotron configured to extract positively charged particles;a nozzle, the positively charged particles transported from said synchrotron through said nozzle and at least into a patient;a first detector imaging first photons to form a first signal, the first photons resultant from the positively charged particles transmitting through a first light emitting element on a first sheet;a second detector imaging second photons to form a second signal, the second photons emitted from a second light emitting element upon the positively charged particles traversing through the second light emitting element on a second sheet, said first sheet parallel to said second sheet, said first sheet not intersecting said second sheet;a controller determining a first vector of the positively charged particle beam path using the first signal and the second signal. 18. The apparatus of claim 17, said nozzle further comprising:an insert comprising an aperture to form a cross-sectional shape the positively charged particles. |
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description | This application claims the benefit of U.S. Provisional Application No. 61/625,448 filed Apr. 17, 2012. U.S. Provisional Application No. 61/625,448 filed Apr. 17, 2012 is hereby incorporated by reference in its entirety. The following relates to the nuclear power reactor arts and related arts. With reference to FIGS. 1 and 2, the lower portion of a nuclear power plant of the pressurized water configuration, commonly called a pressurized water reactor (PWR) design, is shown. A nuclear reactor core 10 comprises an assembly of vertically oriented fuel rods containing fissile material, typically 235U. The reactor core 10 is disposed at or near the bottom of a pressure vessel 12 that contains primary coolant water serving as a moderator to moderate the chain reaction and as coolant to cool the reactor core 10. The primary coolant further acts as a heat transfer medium conveying heat generated in the reactor core 10 to a steam generator. At the steam generator, heat from the primary coolant transfers to a secondary coolant loop to convert the secondary coolant into steam that is used for a useful purpose, such as driving a turbine of an electrical power generation facility. A conventional PWR design includes one or (typically) more steam generators that are external to the pressure vessel containing the nuclear reactor core. Large-diameter piping carries primary coolant from the pressure vessel to the external steam generator and back from the steam generator to the pressure vessel to complete a primary coolant flow loop. In some designs the external steam generator is replaced by an internal steam generator located inside the pressure vessel, which has the advantage of eliminating the large diameter piping (replaced by secondary coolant feedwater and steam outlet lines that are typically of lower diameter and that do not carry the primary coolant that flows through the reactor core). Note that FIG. 1 is a diagrammatic view of the lower reactor core region and does not include features relating to the steam generator or ancillary components. The vertical fuel rods of the reactor core 10 are organized into fuel assemblies 14. Illustrative FIG. 1 shows a side view of a 9×9 array of fuel assemblies 14, although arrays of other sizes and/or dimensions can be employed. In turn, each fuel assembly 14 comprises an array of vertically oriented fuel rods, such as a 18×18 array of fuel rods, or a 14×14 array, or so forth. The fuel assemblies further include a lower end fitting, upper end fitting, vertical guide tubes connecting the end fittings, and a number of spacer grids connected to the guide tubes, instrument tubes and fuel rods. The spacer grids fit around the guide tubes to precisely define the spacing between fuel rods and to add stiffness to the fuel assembly 14. The spacer grids may or may not be welded to the guide tubes. (Note, FIGS. 1 and 2 represent the fuel rods of each fuel assembly 14 are shown diagrammatically with vertical lines which are not to scale respective to size or quantity, and the spacer grids, guide tubes, and other features are not shown). It is noted that the dimensions of the array of fuel assemblies 14 may in general be different from the dimensions of the array of fuel rods within the fuel assembly 14. The fuel assemblies may employ rectangular fuel rod packing and have a square cross section, or may employ hexagonal fuel rod packing and have a hexagonal cross section, or so forth). The reactor core 10 comprising fuel assemblies 14 is disposed in a core basket 16 that is mounted inside the pressure vessel 12. The lower end fitting of each fuel assembly 14 includes features 18 that engage with a core plate. (The core plate, basket mounting, and other details are not shown in diagrammatic FIG. 1). The reactor control system typically includes a control rod assembly (CRA) operated by a control rod drive mechanism (CRDM) (not shown in FIGS. 1 and 2). The CRA includes vertically oriented control rods 20 containing neutron poison. A given control rod is controllably inserted into one fuel assembly 14 through a designated vertical guide tube of the fuel assembly 14. Typically, all the control rods for a given fuel assembly 14 are connected at their top ends to a common termination structure 22, sometimes called a spider, and a connecting rod 24 connects at its lower end with the spider 22 and at its upper portion with the CRDM (upper end not shown). The CRA for a single fuel assembly 14 thus comprises the control rods 20, the spider 22, and the connecting rod 24, and this CRA moves as a single translating unit. In the PWR design, the CRA is located above the reactor core 10 and moves upward in order to withdraw the control rods 20 from the fuel assembly 14 (and thereby increase reactivity) or downward in order to insert the control rods 20 into the fuel assembly 14 (and thereby decrease reactivity). The CRDM is typically designed to release the control rods so as to fall into the reactor core 10 and quickly quench the chain reaction in the event of a power failure or other abnormal event. Because the reactor control system is a safety-related feature, applicable nuclear safety regulations (for example, promulgated by the Nuclear Regulatory Commission, NRC, in the United States) pertain to its reliability, and typically dictate that the translation of the CRA be reliable and not prone to jamming. The translation of the CRA should be guided to ensure the control rods move vertically without undue bowing or lateral motion. Toward this end, each CRA is supported by a control rod guide structure 30 which comprises horizontal guide plates 32 mounted in a spaced-apart fashion on vertical frame elements 34. Each guide plate 32 includes openings or passages or other camming surfaces (not visible in the side view of diagrammatic FIGS. 1 and 2) that constrain the CRA so that the rods 20, 24 are limited to vertical movement without bowing or lateral movement. With continuing reference to FIGS. 1 and 2, the CRA guide assemblies 30 have substantial weight indicated by downward arrow FG,weight in FIG. 2, and are supported by a weight-bearing upper core plate 40. The fuel assemblies 14 are also relatively heavy. However, in a conventional PWR the primary coolant circulation rises through the fuel assemblies 14, producing a net lifting force on the fuel assemblies 14 indicated by upward arrow FFA,lift. Accordingly, the fuel assemblies 14 while typically resting on the bottom of the core basket 16, are susceptible to being lifted upward by the lift force FFA,lift and press against the upper core plate 40. The lift force FFA,lift is thus also borne by the upper core plate 40. The upper core plate 40 thus is a spacer element disposed between and spacing apart the lower end of the CRA guide assembly 30 and the upper end of the corresponding fuel assembly 14. To avoid damaging the fuel rods, each fuel assembly 14 typically includes a hold-down spring sub-assembly 42 that preloads the fuel assembly 14 against the upper core plate 40 and prevents lift-off of the fuel assembly 14 during normal operation. The hold-down spring 42 is thus also disposed between the lower end of the CRA guide assembly 30 and the upper end of the corresponding fuel assembly 14. Additionally, alignment features 44, 46 are provided on the upper end of the fuel assembly 14 and the lower end of the CRA guide structure 30, respectively, to assist alignment. A PWR such as that of FIGS. 1 and 2 is typically designed to provide electrical power of around 500-1600 megawatts. The fuel assemblies 14 for these reactors are typically between 12 and 14 feet long (i.e., vertical height) and vary in array size from 14×14 fuel rods per fuel assembly to 18×18 fuel rods per fuel assembly. The fuel assemblies for such PWR systems are typically designed to operate between 12- and 24-month cycles before being shuffled in the reactor core. The fuel assemblies are typically operated for three cycles before being moved to a spent fuel pool. The fuel rods typically comprise uranium dioxide (UO2) pellets or mixed UO2/gadolinium oxide (UO2—Gd2O3) pellets, of enrichment chosen based on the desired core power. In one aspect of the disclosure, a pressurized water reactor (PWR) comprises: a pressure vessel containing primary coolant water; a nuclear reactor core disposed in the pressure vessel and including a plurality of fuel assemblies wherein each fuel assembly includes a plurality of fuel rods containing a fissile material; a control system including a plurality of control rod assemblies wherein each control rod assembly is guided by a corresponding control rod assembly guide structure; and a support element disposed above the control rod assembly guide structures wherein the support element supports the control rod assembly guide structures. In some embodiments the pressure vessel is a cylindrical pressure vessel and the support element comprises a support plate having a circular periphery supported by the cylindrical pressure vessel. In some embodiments the control rod assembly guide structures hang downward from the support plate. In some embodiments the lower end of each control rod assembly guide structure includes alignment features that engage corresponding alignment features of the upper end of the corresponding fuel assembly. In another aspect of the disclosure, a method comprises: operating a pressurized water reactor (PWR) wherein the operating includes circulating primary coolant in a pressure vessel upward through a nuclear reactor core that includes a plurality of fuel assemblies wherein each fuel assembly includes a plurality of fuel rods containing a fissile material; and during the operating, suspending control rod drive assembly guide structures disposed in the pressure vessel from suspension anchors disposed above the control rod drive assembly guide structures. In some such method embodiments, a downward force (other than gravity) is not applied against the fuel assemblies during the operating. In some such method embodiments, upward strain of the fuel assemblies and downward strain of the suspended control rod drive assembly guide structures is accommodated during the operating by a gap between the tops of the fuel assemblies and the bottoms of the suspended control rod drive assembly guide structures. In another aspect of the disclosure, a pressurized water reactor (PWR) comprises: a pressure vessel containing primary coolant water; a nuclear reactor core disposed in the pressure vessel and including a plurality of fuel assemblies wherein each fuel assembly includes a plurality of fuel rods containing a fissile material; a control system including a plurality of control rod assemblies wherein each control rod assembly includes control rods selectively inserted into the nuclear reactor core and wherein each control rod assembly is guided by a corresponding control rod assembly guide structure; wherein there is a gap between the bottoms of the control rod assembly guide structures and the top of the nuclear reactor core and wherein no spacer element or spring is disposed in the gap. In some embodiments the control rod assembly guide structures are not supported from below the control rod assembly guide structures. In some embodiments there is a one-to-one correspondence between the control rod assembly guide structures and the fuel assemblies of the nuclear reactor core, and the lower end of each control rod assembly guide structure includes alignment features that engage corresponding alignment features of the upper end of the corresponding fuel assembly. In some embodiments the PWR further includes a support element disposed above the control rod assembly guide structures and anchoring the tops of the control rod assembly guide structures such that the control rod assembly guide structures are suspended from the support element. In some embodiments flow of primary coolant water in the pressure vessel in the operational state of the PWR is not sufficient to lift the fuel assemblies upward. In another aspect of the disclosure, a nuclear reactor fuel assembly is configured for installation and use in a pressurized water nuclear reactor (PWR). The nuclear reactor fuel assembly includes a bundle of fuel rods containing a fissile material, and alignment features disposed at an upper end of the nuclear reactor fuel assembly. The upper end of the nuclear reactor fuel assembly is not configured as a load bearing structure. In some embodiments the upper end of the nuclear reactor fuel assembly does not include any hold-down springs. In some embodiments the alignment features disposed at the upper end of the nuclear reactor fuel assembly are configured to mate with corresponding alignment features of a control rod assembly guide structure. With reference to FIGS. 3 and 4, a pressurized water reactor (PWR) is shown which is designed to operate as a small modular reactor (SMR). The SMR preferably outputs 300 megawatts (electrical) or less, although it is contemplated for the SMR to output at higher power. The PWR of FIGS. 3 and 4 is designed to operate at a relatively low primary coolant flow rate, which is feasible because of the relatively low SMR output power. The PWR of FIGS. 3 and 4 includes a number of components that have counterparts in the PWR of FIGS. 1 and 2, including: a reactor pressure vessel 12; a reactor core 10 comprising fuel assemblies 14 in a core basket 16; a control rod assembly (CRA) for each fuel assembly that includes control rods 20 mounted on a spider 22 connected to the lower end of a connecting rod 24; and a CRA guide structure 30 for each CRA comprising horizontal guide plates 32 mounted in a spaced-apart fashion on vertical frame elements 34. Although these components have counterparts in the conventional PWR of FIGS. 1 and 2, it is to be understood that the sizing or other aspects of the components in the PWR of FIGS. 3 and 4 may be optimized for the SMR operational regime. For example, a PWR designed to operate at 150 megawatts electrical may have fuel assemblies 14 that are 8 feet long and use a 17×17 bundle of fuel rods per fuel assembly 14 with 24 guide tubes spaced on a 0.496-inch pitch. The PWR of FIGS. 3 and 4 omits the upper core plate 40 of the embodiment of FIGS. 1 and 2. Omitting this weight-bearing plate 40 has substantial advantages. It reduces the total amount of material thus lowering manufacturing cost. Additionally, the upper core plate 40 presents substantial frontal area generating flow resistance. Although this can be mitigated to some extent by including flow passages in the plate 40, the frontal area occupied by the control rods 20, the lower end plates of the CRA guide assemblies 30, and the upper end fittings of the fuel assemblies 14, limits the amount of remaining frontal area that can be removed. The load-bearing nature of the upper core plate 40 also limits the amount of material that can be safely removed to introduce flow passages through the plate 40, since removing material to provide flow passages reduces the load-bearing capacity of the plate 40. However, omitting the load-bearing upper core plate 40 introduces substantial new issues. In the embodiment of FIGS. 1 and 2, the plate 40 performs the functions of supporting the weight of the CRA guide assemblies 30 and providing the upper stop against which the lift force FFA,lift on the fuel assemblies 14 operates to stabilize the positions of the fuel assemblies 14. Moreover, the upper core plate 40 provides a common anchor point for aligning the fuel assemblies 14 with their respective CRA guide assemblies 30. These issues are addressed in the embodiment of FIGS. 3 and 4 as follows. In the embodiment of FIGS. 3 and 4, the CRA guide assemblies 30 are suspended from above by a support element 50 disposed above the CRA guide assemblies 30. In embodiments in which the pressure vessel 12 is a cylindrical pressure vessel (where it is to be understood that “cylindrical” in this context allows for some deviation from a mathematically perfect cylinder, for example to allow for tapering of the upper end of the pressure vessel 12, adding various vessel penetrations or recesses, or so forth), the support element 50 is suitably a support plate 50 having a circular periphery supported by the cylindrical pressure vessel (for example supported by an annular ledge, or by welding the periphery of the plate 50 to an inner cylindrical wall of the cylindrical pressure vessel, or so forth). In some embodiments the CRA guide assemblies 30 are not supported from below. This arrangement is feasible because in the SMR design the reduced height of the fuel assemblies 14 reduces the requisite travel for the CRA and hence reduces the requisite height for the CRA guide assemblies 30 in the SMR of FIGS. 3 and 4 as compared with the higher power PWR of FIGS. 1 and 2. The support element 50 is located in a less congested area of the pressure vessel 12 as compared with the upper core plate 40 of the PWR of FIGS. 1 and 2. The area above the CRA support structures 30 includes the upper ends of the CRA assemblies 30 and the connecting rods 24, but not the fuel assemblies. Accordingly, there is more “unused” frontal area of the support plate 50, which allows for forming relatively more and/or larger flow passages into the support element 50. The support element 50 is also further away from the reactor core 10 than the upper core plate 40 of the PWR of FIGS. 1 and 2, which makes any spatial variation in the flow resistance that may be introduced by the frontage of the support element 50 less problematic as compared with the upper core plate 40. The load-bearing provided by the upper core plate 40 respective to the upward lift force FFA,lift is not needed in the SMR of FIGS. 3 and 4, because the flow rate sufficient to provide SMR output of 300 megawatts (electrical) is generally not sufficient to generate a lift force capable of overcoming the weight of the fuel assemblies 14. Thus, in the SMR embodiment of FIGS. 3 and 4 the fuel assemblies 14 have a net force FFA,weight which is the weight of the fuel assembly 14 minus the lifting force generated by the relatively low primary coolant flow rate. As a consequence, the fuel assemblies 14 remain supported from below by the core basket 16 (or by a core plate component inside of or forming the bottom of the core basket 16). Thus, in the embodiment of FIGS. 3 and 4 the upper end of the fuel assembly 14 is not configured as a load-bearing structure, and both the upper core plate 40 and the hold-down springs 42 are omitted in the SMR embodiment of FIGS. 3 and 4. With continuing reference to FIGS. 3 and 4 and with further reference to FIG. 5, relative alignment between corresponding CRA guide structure 30 and fuel assembly 14 is achieved by engagement of mating features 60 on the top end of the fuel assembly 14 and corresponding mating features 62 on the bottom end of the CRA guide structure 30. The features 60, 62 ensure lateral alignment. In the illustrative embodiment the mating features 60 on the top of the fuel assembly 14 are protrusions, e.g. pins, and the mating features 62 on the bottom of the CRA guide structure 30 are mating recesses; however, other mating feature configurations are contemplated. In some embodiments the mating pins 60 on the top of the fuel assembly 14 also serve as anchor points for lifting the fuel assembly 14 out of the PWR during refueling or other maintenance operations, as described in Walton et al., “Nuclear Reactor Refueling Methods and Apparatuses”, U.S. Ser. No. 13/213,389 filed Aug. 19, 2011, which is incorporated herein by reference in its entirety. With particular reference to FIGS. 4 and 5, vertical alignment is an additional issue. The fuel assembly 14 and the CRA guide structure 30 are subject to respective strains SG,thermal and SFA,thermal as the components 14, 30 increase from ambient temperature to operational temperature. In the embodiment of FIGS. 3-5, the upper end of the CRA guide structure 30 and the lower end of the fuel assembly 14 are both anchored. Thus, the thermal expansion causes the upper end of the fuel assembly 14 and the lower end of the CRA guide structure 30 to come closer together. This is accommodated by a gap G between the lower end of the CRA guide structure 30 and the upper end of the corresponding fuel assembly 14. The gap G is chosen to accommodate thermal expansion at least up to temperatures credibly expected to be attained during operation or credible malfunction scenarios. The mating features 60, 62 are designed to span the gap G in order to provide the lateral alignment between the CRA guide structure 30 and corresponding fuel assembly 14. It will be noted that there is no spacer element or spring in the gap G. (The control rods 20 do pass through the gap G when inserted into the fuel assembly 14; however, the control rods 20 are not spacer elements that space apart the CRA guide structure 30 and fuel assembly 14, and are also not springs. Similarly, primary coolant water fills the gap G but is also neither a spacer element nor a spring). The embodiment of FIGS. 3-5 employs the CRA guide structure 30 which comprises the spaced apart horizontal guide plates 32 mounted on the vertical frame elements 34. This is a conventional CRA guide structure design, and is commonly used in conjunction with external control rod drive mechanism (CRDM) units (not shown in FIGS. 3-5) disposed outside of and above the pressure vessel 12 of the PWR. In some embodiments, it is contemplated to employ internal CRDM disposed inside the pressure vessel 12. With reference to FIG. 6, it is also contemplated to employ a continuous CRA guide structure 30C which provides continuous support/guidance of the CRA over the entire length of the continuous CRA guide structure 30C. The embodiment of FIG. 6 also employs a heavy terminating element 22H in place of the conventional spider to provide the common termination structure at which the top ends of the control rods 20 are connected. The heavy terminating element 22H advantageously adds substantial weight to the translating CRA 20, 22H, 24 as compared with the conventional CRA 20, 22, 24 of the PWR of FIGS. 3-5. This additional weight reduces SCRAM time and effectively compensates for the otherwise reduced weight of the SMR CRA which is shortened as compared with the CRA of a higher-power PWR. The “Inset” of FIG. 6 shows a perspective view of the heavy terminal element 22H, while “Section A-A” of FIG. 6 shows a cross-section of the continuous CRA guide structure 30C. As seen in Section A-A, the CRA guide structure 30C includes camming surfaces 70 that guide the control rods 20, and a larger contoured central opening 72 that guides the heavy terminal element 22H. Additionally, the CRA guide structure 30C includes flow passages 74 to allow primary coolant water to egress from the internal volume 70, 72 quickly as the CRA falls during a SCRAM. Additional aspects of the continuous CRA guide structure 30C and the heavy terminal element 22H are set forth in Shargots et al., “Support Structure For A Control Rod Assembly Of A Nuclear Reactor”, U.S. Ser. No. 12/909,252 filed Oct. 21, 2010, which is incorporated herein by reference in its entirety. With reference to FIG. 7, the fuel assembly 14, CRA guide structure 30C, and connecting rod 24 are suitably shipped as components. Because the upper end of the nuclear reactor fuel assembly is not configured as a load-bearing structure and does not include the hold-down spring sub-assembly 42 (cf. FIG. 2), shipping weight is reduced, and the possibility of collision or entanglement of the hold-down springs with surrounding objects during shipping is eliminated. As seen in FIG. 7, the shipping configuration for the fuel assembly 14 includes the control rods 20 fully inserted into the fuel assembly 14. Optionally, the heavy terminal element 22H (or, alternatively, the spider 22 in embodiments employing it) is connected to the top ends of the control rods 20 that are inserted into the fuel assembly 14 during shipping. The continuous CRA guide structure 30C can be shipped as a single pre-assembled unit, as shown in FIG. 7, or alternatively may be constructed as stacked segments that are shipped in pieces and welded together at the PWR site. The connecting rod 24 is suitably shipped as a separate element that is detached from the spider or heavy terminal element 22, 22H. The lower end of the connecting rod 24 optionally includes a J-lock fitting or other coupling 80 via which the lower end may be connected to the spider or heavy terminal element 22, 22H during installation into the PWR. Alternatively, the lower end may be directly welded to the spider or heavy terminal element 22, 22H. The preferred embodiments have been illustrated and described. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. |
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summary | ||
044850670 | summary | BACKGROUND OF THE INVENTION This invention relates to a fuel transfer manipulator for liquid metal cooled fast breeder nuclear reactors (LMFBR). The function of the manipulator is to transfer fuel assemblies from a fuel chute arising from the reactor vessel to and from a fuel chute arising from a fuel storage pit to facilitate passage of fuel assemblies therebetween during reactor refueling operations. The fuel assemblies of LMFBRs are immersed in a liquid metal coolant, usually liquid sodium, which can burn if exposed to environmental oxygen. Consequently, the systems for removing and replacing the fuel assemblies from the reactor must do so while maintaining the assembly in a sealed and protected environment. The usual method is to hoist the assemblies to and from the nuclear reactor vessel and to and from the fuel storage pit via two fuel chutes. The chutes terminate at one end in a transfer chamber where the fuel assembly must be transferred from one chute to the other. The transfer chamber is normally filled with an inert gas such as Argon. Because the transfer chamber is open to the reactor and to the fuel storage pit during fuel transfers, the transfer chamber is considered to be a high radiation and high temperature area to which human access is restricted. The transfer chamber must be a small size because of the gaseous inerting requirement and because of space limitations imposed by the proximity of other equipment. The transfer manipulator might be a hoist mounted on a bridge trolley, but this solution does not easily match the required motion because the lifting of the hoist must be remotely coordinated with trolley movement. The manipulator might be a pendulum mounted hoist but this solution suggests a tall structure. Consequently, it is desired to provide a transfer manipulator which is simple in operation and construction, suitable for long term use in high temperature, high radiation areas, and small in size. SUMMARY OF THE INVENTION The invention is a fuel transfer manipulator termed a shifting-beam carriage. Four legs support a hoist box to which each leg is rotatably fixed at one end by pin attachments. Each leg is rotatably fixed at the other end to a base by pin attachments. The hoist is shiftable between two extreme positions which correspond to respective alignment configurations between the hoist and a reactor vessel fuel chute and between the hoist and a fuel pit fuel chute. |
claims | 1. A rod position indicator system comprising:a drive rod operably coupled to a control rod, wherein the control rod is configured to be both withdrawn from and inserted into a reactor core;a number of sensing devices arranged along a path of the drive rod, wherein an end of the drive rod passes by one or more of the sensing devices in response to movement of the control rod with respect to the reactor core, wherein the sensing devices are arranged into a plurality of groups, each group comprising two or more of the sensing devices electrically coupled together and each positioned at different vertical locations along the path of the drive rod; anda control rod monitoring device electrically and separately coupled to each group of sensing devices by a separate set of routing wires. 2. The rod position indicator system of claim 1, wherein a total number of the routing wires connected to the groups of sensing devices that are routed out of the containment vessel is less than half of the number of sensing devices. 3. The rod position indicator system of claim 2, including multiple groups of the sensing devices each connected by a first terminal through a separate routing wire to the control rod monitoring device and connected by a second terminal through a same bus to the control rod monitoring device. 4. The rod position indicator system of claim 1, wherein the sensing devices in a first one of the plurality of groups are located in alternating positions in-between the sensing devices in a second one of the plurality of groups. 5. A rod position indicator system comprising:a drive rod operably coupled to a control rod, wherein the control rod is configured to be both withdrawn from and inserted into a reactor core;a number of sensing devices arranged along a path of the drive rod, wherein an end of the drive rod passes by one or more of the sensing devices in response to movement of the control rod with respect to the reactor core, and wherein the sensing devices are arranged into a plurality of groups, each group comprising two or more of the sensing devices electrically coupled together; anda control rod monitoring device electrically coupled to each group of sensing devices by a routing wire, wherein the groups of sensing devices comprise sensing coils configured with first and second terminals that electrically couple the sensing coils in series, wherein a first terminal of a first sensing coil is electrically coupled to the control rod monitoring device via the routing wire, wherein a second terminal of the first sensing coil is electrically coupled to a first terminal of a second sensing coil, and wherein a second terminal of the second sensing coil is electrically coupled to a first terminal of a third sensing coil. 6. The rod position indicator system of claim 5, further comprising one or more buses, wherein a second terminal of the third sensing coil is electrically coupled to at least one of the one or more buses, and wherein a total number of routing wires associated with the groups of sensing devices that are routed to the control rod monitoring device is approximately one third of the number of sensing devices. 7. The rod position indicator system of claim 1, wherein the control rod monitoring device comprises:a first circuit component electrically coupled to a first group of sensing devices comprising a first sensing device electrically coupled to a third sensing device in series;a second circuit component electrically coupled to a second group of sensing devices comprising a second sensing device electrically coupled to a fourth sensing device in series; anda comparator configured to compare a first electrical property associated with the first circuit component to a second electrical property associated with the second circuit component to determine a position of the drive rod relative to the number of sensing devices. 8. The rod position indicator system of claim 7, wherein the second sensing device of the second group of sensing devices is linearly arranged between the first sensing device and the third sensing device of the first group of sensing devices, and wherein the third sensing device of the first group of sensing devices is linearly arranged between the second sensing device and the fourth sensing device of the second group of sensing devices. 9. The rod position indicator system of claim 7, wherein the first circuit component comprises a first resistor, wherein the second circuit component comprises a second resistor, and wherein the first resistor and the second resistor are electrically coupled together in series. 10. The rod position indicator system of claim 7, wherein the comparator comprises an encoder configured to determine root mean squared (RMS) values of the first and second electrical properties. 11. A rod position indicator system comprising:a drive rod operably coupled to a control rod, wherein the control rod is configured to be both withdrawn from and inserted into a reactor core;a number of sensing devices arranged along a path of the drive rod, wherein an end of the drive rod passes by one or more of the sensing devices in response to movement of the control rod with respect to the reactor core, and wherein the sensing devices are arranged into a plurality of groups, each group comprising two or more of the sensing devices electrically coupled together;multiple buses each separately coupled to a different one of the groups of sensing devices;multiple routing wires each separately coupled to a different one of the groups of sensing devices; anda control rod monitoring device separately coupled to the multiple buses and routing wires coupled to each of the groups of sensing devices. 12. The rod position indicator system of claim 11, wherein at least some of the sensing devices in some of the groups are separately coupled together in series and each positioned at different vertical locations along the path of the drive rod. 13. The rod position indicator system of claim 12, wherein the sensing devices in at least some of the groups are separately coupled together in series between one of the multiple buses and one of the routing wires. 14. The rod position indicator system of claim 12, wherein the multiple buses are each coupled to two or more of the different groups of sensing devices. 15. The rod position indicator system of claim 11, wherein the sensing devices in a first one of the groups are located in alternating positions in-between the sensing devices in a second one of the groups. |
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063174774 | claims | 1. A seal assembly for sealing an annular space between two adjacent annular surfaces, comprising: an inflatable annular seal; and an annular support structure connected to and supporting said inflatable seal, said annular support structure having a generally rigid structure that straddles the annular space to be sealed and engages the surfaces on both sides of the annular space, whereby said annular support structure provides a structure for handling said inflatable seal during installation and removal and provides a leak limiting structure in the event the inflatable seal fails, wherein said annular support structure has a generally inverted U-shaped cross-section. an inflatable annular seal; and an annular support structure connected to and supporting said inflatable seal, said annular support structure having a generally rigid structure that straddles the annular space to be sealed and engages the surfaces on both sides of the annular space, whereby said annular support structure provides a structure for handling said inflatable seal during installation and removal and provides a leak limiting structure in the event the inflatable seal fails, wherein said inflatable seal comprises an upper wedge portion and a lower tubular portion, said lower tubular portion being expandable when pressurized to engage lower edges of said annular surfaces to form a secondary seal, said upper wedge portion being drawn into engagement with upper edges of said annular surfaces to form a primary seal when said tubular portion is further pressurized. an inflatable annular seal; and an annular support structure connected to and supporting said inflatable seal, said annular support structure having a generally rigid structure that straddles the annular space to be sealed and engages the surfaces on both sides of the annular space, whereby said annular support structure provides a structure for handling said inflatable seal during installation and removal and provides a leak limiting structure in the event the inflatable seal fails, wherein an inner one of said annular surfaces is associated with a reactor vessel annular flange in a nuclear reactor, and an outer one of said annular surfaces is associated with a closure plate secured to a surrounding ledge of a refueling canal. an annular closure plate having an outer portion secured to the surrounding ledge and an inner portion supporting a first sealing surface, said first sealing surface being disposed adjacent to a second sealing surface associated with the annular flange, and an annular space being formed between said first and second sealing surfaces; an inflatable seal disposed in said annular space for engaging said first and second sealing surfaces; and an annular support structure straddling said annular space, said inflatable seal being secured to said support structure and supported by said support structure during installation and removal. an inflatable annular seal; and an annular support structure connected to and supporting said inflatable seal, said annular support structure having a generally rigid structure that straddles the annular space to be sealed and engages the surfaces on both sides of the annular space, whereby said annular support structure provides a structure for handling said inflatable seal during installation and removal and provides a leak limiting structure in the event the inflatable seal fails, wherein said annular support structure has first and second legs that straddle said annular space, and elastomer seals associated with each of said legs to seal the interfaces between the legs and the respective annular surfaces. 2. A seal assembly for sealing an annular space between two adjacent annular surfaces, comprising: 3. A seal assembly for sealing an annular space between two adjacent annular surfaces, comprising: 4. The seal assembly according to claim 3, wherein said closure plate comprises a plurality of access openings extending therethrough, and a plurality of removable covers secured to said closure plate and covering said access openings. 5. A seal assembly for sealing a space between an annular flange on a nuclear reactor vessel and a surrounding ledge of a refueling canal to provide a temporary water barrier between the refueling canal and the reactor vessel, comprising: 6. The seal assembly according to claim 5, wherein said inflatable seal is movable vertically and transversely relative to said annular support structure to conform to irregularities in the first and second sealing surfaces. 7. The seal assembly according to claim 5, wherein said closure plate comprises a plurality of access openings and a plurality of removable covers secured to said closure plate and covering said access openings. 8. The seal assembly according to claim 5, wherein said annular support structure has an outer side engaging said closure plate, an inner side engaging a ledge ring associated with said annular flange, and a structure extending between said first and second sides for supporting said inflatable seal, said annular support structure providing a leak limiting structure in the event the inflatable seal fails. 9. A seal assembly for sealing an annular space between two adjacent annular surfaces, comprising: 10. The seal assembly according to claim 9, wherein said inflatable seal is movable vertically and transversely relative to said annular support structure to facilitate self alignment of said inflatable seal within said annular space. 11. The seal assembly according to claim 10, wherein said inflatable seal comprises a plurality of threaded inserts embedded in an upper surface thereof, and said annular support structure is connected to said inflatable seal using shoulder bolts threaded into said inserts. 12. The seal assembly according to claim 11, wherein said annular support structure has a plurality of slotted openings through which said bolts extend to connect said annular support structure to said inflatable seal. 13. The seal assembly according to claim 11, wherein said annular support structure has a bolt retainer secured to an underside of said annular support structure, and said bolts are retained by said bolt retainer in a manner that allows said inflatable seal to move vertically and transversely relative to said annular support structure. |
description | 1. Field of the Invention This present invention relates generally to a method and apparatus for repairing a riser brace assembly that lends lateral support to a jet pump of a boiling water reactor. 2. Description of the Related Art A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically-shaped shroud. FIG. 1 is a schematic, partial cross sectional view, with parts cut away, of a reactor pressure vessel (RPV) 20 for a boiling water reactor. RPV 20 has a generally cylindrical-shape and is closed at one end by a bottom head and at its other end by removable top head (not shown). A top guide (not shown) is situated above a core plate 22 within RPV 20. A shroud 24 surrounds core plate 22 and is supported by a shroud support structure 26. A downcomer annulus 28 is formed between shroud 24 and sidewall 30 of RPV 20. An annulet nozzle 32 extends through sidewall 30 of RPV 20 and is coupled to a jet pump assembly 34, hereafter “jet pump 34”. Jet pump 34 may include a thermal sleeve 36 which extends through nozzle 32, a lower elbow (only partially visible in FIG. 1), and a riser pipe 38. Thermal sleeve 36 is secured at a first end (not shown) to a second end of the lower elbow. The first end of thermal sleeve 36 is welded to the second end of the lower elbow. A first end of the lower elbow similarly secured, or welded, to one end of riser pipe 38. Riser pipe 38 extends between and substantially parallel to shroud 24 and sidewall 30. A jet pump riser brace assembly 40 (hereafter “riser brace assembly 40”) stabilizes riser pipe 38 within RPV 20. The riser brace assembly 40 may be fabricated of type 304 stainless steel which, after periods of use, may be susceptible to cracking at welded joints. The riser brace assembly 40 is fixedly connected between shroud 24 and sidewall 30, and primarily provides lateral support to the jet pump 34 via riser pipe 38, as shown in FIG. 1. Additionally the riser brace assembly 40 is designed to accommodate for differential thermal expansion resulting from reactor start-up and heat-up, and flow induced vibration that is incumbent in the reactor water recirculation system (not shown). FIG. 2 illustrates the riser brace assembly 40 of FIG. 1 in further detail. In FIG. 2, the riser pipe 38 has been removed for reasons of clarity. Riser brace assembly 40 primarily provides lateral support to the jet pump 34 via riser pipe 38, and includes a riser brace yoke 49 that is welded to the riser pipe 38. Riser brace yoke 49 may typically be a plate that is between about 3-4 inches thick. Riser brace yoke 49 is connected via welds to two pairs of riser brace leaves, an upper riser brace leaf (shown as 41a, 41b) and a lower riser brace leaf (shown as 42a and 42b). Leaves 41a/b and 42a/b are welded to a reactor vessel riser brace pad 130 (hereafter “reactor vessel pad 130”) which in turn is affixed to RPV sidewall 30. In an example, the reactor vessel pad 130 may be embodied as a weld buildup on the surface of RPV sidewall 30. Thus, riser brace assembly 40 includes four riser brace leaves 41,a, 42a, 41b and 42b, which are welded at one end, shown as riser brace leaf attachment welds 143-146, to reactor vessel pads 130 provided on the RPV sidewall 30. Welds 143-146 may be commonly referred to as “RB-1” welds, for example. In the event that the structural integrity of the welds 143-146 joining the riser brace assembly 40 and the pads 130 should become degraded, a means of reinforcing or replacing the subject weld 143-146 is desired. For example, weld failure due to vibration fatigue, and/or weld cracking due to intergranular stress corrosion cracking (IGSCC) could cause one of the welds 143-146 to fail. Separation of the riser brace assembly 40 near this weld area could adversely impact safety in BWRs. Potentially, should a riser brace assembly 40 break away from RPV 20 (e.g., at RPV sidewall 30), the riser pipe 38 becomes unstabilized, and the jet pump 34 could be adversely affected. If just one jet pump 34 is damaged, a substantial amount of piping must either be replaced or repaired. In recent years, riser brace clamps have been fabricated and installed in a domestic BWR. These clamps are designed to provide structural support between the riser brace and an adjoining “block” structure in the riser brace assemblies of a select few BWRs. Such an exemplary clamp apparatus is described in U.S. Pat. No. 6,857,814 to the inventor, entitled “METHOD AND APPARATUS FOR REPAIRING A RISER BRACE IN NUCLEAR REACTOR”, the relevant portions of which are incorporated in their entirety by reference herein. An exemplary embodiment of the present invention is directed to a clamp apparatus for repairing a riser brace assembly in a nuclear reactor. The riser brace assembly may include upper and lower riser brace leaves, which are connected to a reactor pressure vessel pad on a wall of the nuclear reactor. The clamp apparatus may include a first clamp component including a central extension portion, and a second clamp component including a slot portion. The central extension and slot portions may be engaged to provide alignment between the first and second clamp components between the upper and lower riser brace leaves of the riser brace assembly. Another exemplary embodiment of the present invention is directed to a method of installing a clamp apparatus at an interface of a reactor vessel pad on a wall of a nuclear reactor with a riser brace assembly supporting a jet pump in a nuclear reactor. The riser brace assembly may include upper and lower riser brace leaves. In the method, a central extension portion of a first clamp component may be engaged within a slot portion of a second clamp component to provide alignment between the first and second clamp components between the upper and lower riser brace leaves. Clamping forces may be applied to secure the first and second clamp components to the reactor vessel pad and to one of the upper and lower riser brace leaves. A first plate may be attached to the first and second clamp components so as to bear on a top surface of the upper riser brace leaf, and a second plate may be attached to the first and second clamp components so as to bear on an underside surface of the first and second clamp components. Another exemplary embodiment of the present invention is directed to a clamp apparatus for structurally replacing a defective weld used to attach one of an upper and a lower riser brace leaf of a riser brace assembly to a reactor vessel pad in a nuclear reactor. The clamp apparatus may include a first clamp component including a central extension portion, and a second clamp component including a slot portion, where the central extension portion may be engaged within the slot portion. The first and second clamp components are fixedly secured to only one of the upper and lower riser brace leaves to replace the defective weld. FIGS. 3 and 4 are isometric views of a clamp apparatus in accordance with an exemplary embodiment of the present invention. FIG. 3 is a view showing the side of the clamp apparatus which engages a riser brace leaf, and FIG. 4 is a view showing the side of the clamp apparatus 50 which is in contact with reactor vessel pad 130. The riser brace clamp apparatus 50 as shown in FIGS. 3 and 4 may include four primary structural components with associated mechanical fasteners and locking devices. The primary components of the clamp assembly 50 may include an outboard clamp component 60 (‘first clamp component’), an inboard clamp component 70 (‘second clamp component’), a primary bearing plate 80 (‘first plate’, and a secondary bearing plate 90 (‘second plate’). The riser brace clamp apparatus 50 may be applicable to any one of the four possible reactor weld locations 143-146 as shown in FIG. 2. Similar reactor vessel pads 130 and associated welds 143-146 exist for each jet pump riser brace assembly 40. Accordingly, the clamp apparatus 50 is fixedly secured to only one riser brace leaf so as to structurally replace the corresponding weld at the interface of that least with the reactor vessel pad 130. FIG. 5 is a plan view of the clamp apparatus shown in FIGS. 3 and 4 arranged within a reactor pressure vessel such as RPV 20 so as to replace a defective weld at a single riser brace leaf to reactor vessel riser brace pad 130 interface, in accordance with an exemplary embodiment of the present invention. For descriptive purposes, the riser brace clamp apparatus 50 is shown installed at the upper left weld 144 location of leaf 41a in FIG. 5. FIG. 6 is an enlarged perspective view illustrating the riser brace leaf 41a to reactor vessel pad 130 connection to describe machined features for receiving the exemplary clamp apparatus 50 of the present invention. In order to attach to the RPV 20 and thereby transfer mechanical loads from the riser brace leaf 41a to the RPV 20, modifications may be made to the reactor vessel pad 130. These alterations as shown in FIG. 6 may be accomplished by electric discharge machining (EDM), for example, although other known techniques of machining may be employed as is evident to one skilled in the art. For example, two half-dovetail features 150 may be machined vertically into opposite sides of the reactor vessel pad 130. In addition, four horizontal surfaces 160 may be machined at each of the four corners of the reactor vessel pad 130, as shown in FIG. 6. Additionally, two crescent-shaped features 170 may be provided on a top surface of the riser brace leaf 41a (it being understood that features 150,160 and 170 may be included similarly on other leaf pairs 41/42 of other riser brace assemblies 40. If the clamp apparatus 50 installation is to be made on a lower riser brace leaf 42a or 42b (at welds 145,146), then the crescent-shaped features 170 may be machined into the bottom surface of the respective leaf 42a or 42b. This follows from the fact that the clamp apparatus 50 would be oriented “up-side down” from the reference orientation shown in FIG. 5. If the desired clamping location were to be associated with the upper right weld location 143, then the clamp assembly 50 would therefore need to be what is commonly referred to as an “opposite hand” clamp assembly 50. This is necessitated by the curvature of internal surface of RPV 20, identical clamp assembly 50 hardware would be installed on the upper left 41a and lower right 42b riser brace leaves. Likewise, an opposite hand clamp assembly 50 would be installed on the upper right 41b and lower left 42a riser brace leaves. FIG. 7 is an exploded view of the clamp apparatus in accordance with an exemplary embodiment of the present invention. FIG. 7 more clearly illustrates the primary structural components of the clamp assembly 50: outboard clamp component 60, inboard clamp component 70, primary bearing plate 80 and secondary bearing plate 90. These clamp apparatus 50 components may be adapted to evenly distribute stress on surfaces of the riser brace assembly, and may be fixedly secured to the riser brace assembly 50 with mechanical fasteners adapted to provide clamping forces. The clamp apparatus 50 components with mechanical fasteners (i.e., associated bolts, nuts, and locking devices) are shown in the exploded view of FIG. 7. The outboard clamp component 60 and inboard clamp component 70 interface with the reactor vessel pad 130 at the location of the half-dovetails 150, which have been machined into the reactor vessel pad 130. The outboard and inboard clamp components 60, 70 interface together by virtue of two features, a ‘hinge’ feature and a ‘central extension and slot’ feature. FIG. 9 is an enlarged view illustrating an outboard clamp of the clamp apparatus; and FIG. 10 is an enlarged view illustrating an inboard clamp of the clamp apparatus, in accordance with an exemplary embodiment of the present invention. As shown clearly in FIGS. 9 and 10, and with reference to FIG. 7, a central extension portion 62 of the outboard clamp component 60 slides into a slot portion 72 of the inboard clamp component 70. The central extension portion 62 and slot portion 72 features ensure that the outboard and inboard clamp components 60, 70 are oriented properly with respect to each other so as to provide the proper alignment necessary for clamp bolts 73, clamp bolt keepers 74 and clamp bolt nuts 63. Accordingly, engagement of the central extension and slot portions 62 and 72 permits a degree or articulation between the first and second clamp components so as to provide a hinge point for first and second clamp component movement. Movement (and alignment) may be further facilitated by a hinge relationship between clamp components 60 and 70. As shown in FIGS. 9 and 10, inboard clamp component 70 includes a cylindrical male hinge feature 172 which may engage to a cylindrical female hinge feature 162 of outboard clamp component 60. As shown best in FIG. 10, counter-bored holes 76 in the inboard clamp component 70 receive the clamp bolts 73 and clamp bolt keepers 74. Counter-bored holes 64 (FIG. 7) in the outboard clamp component 60 likewise receive the clamp bolt nuts 63. FIGS. 11A and 11B are enlarged views of a clamp bolt and clamp bolt keeper of the clamp apparatus, in accordance with an exemplary embodiment of the present invention. As shown best in FIG. 11B, mating surfaces 75 of the clamp bolt keeper 74 and inboard clamp component 70 may be spherical and the mating surfaces 65 of the clamp bolt nut 63 and outboard clamp 60 (see FIG. 7) may also be generally spherical. These spherical bearing surfaces 65 and 75 may be present at both ends (i.e., nuts 63 and keepers 74) in the vicinity of the clamp bolts 73 so as to allow a small degree of articulation between the outboard and inboard clamp components 60, 70. The use of spherical surfaces 65, 75 thus allows articulation to alleviate bending stresses in the clamp bolts 73. As a mechanical preload is applied through the clamp bolts 73, a clamping force may be generated at the interface of the reactor vessel pad half-dovetails 150 and the outboard and inboard clamp components 60, 70 as the clamp components 60, 70 pivot about their ‘hinge’ point at features 162, 172. Associated with the counter-bored features in the outboard and inboard clamp components are ‘keyways’ shown generally at 66 in FIG. 7 which receive ‘keyed’ features 67 (for clamp bolt nuts 63), and keyed features 77 of the clamp bolt keepers 74. As shown in FIG. 11B, these features 67, 77 may inhibit relative rotation of the clamp bolt nuts 63 and clamp bolt keepers 74 with the outboard clamp component 60 and inboard clamp component 70, respectively. To prevent loosening of the clamp bolts 73, ‘ratchet teeth’ 78 of the clamp bolt keepers 74 interface with ‘teeth’ 79 of the clamp bolts 73. Additionally, the top surface 71 (FIG. 10) of the inboard clamp component 70 may be machined so that the contact area with the lower (underside) surface of the riser brace leaf 41a (or 41b) is exactly opposite with the area of contact of the primary bearing plate 80 with the upper surface of the riser brace leaf 41a, 41b. This may be seen for example in FIGS. 3 or 5. This is important since the riser brace leaf 41a, 41b is typically subject to flow-induced vibration from the reactor water recirculation system, for example. Once the inboard and outboard clamp components 60, 70 are properly oriented in relation to the reactor vessel pad 130 and riser brace leaf 41/42, and a desired mechanical preload has been applied to the clamp bolts 73, features of the clamp components 60, 70 may be utilized to ‘match machine’ the crescent shaped features 170 in the upper surface of the riser brace leaf 41a, 41b. The brace bolts 81 may then be added to the clamp assembly 50 with the desired mechanical preload applied. Field measurements may then be ascertained and the primary and secondary bearing plates 80, 90 machined accordingly. Measurements may be taken from the horizontal surfaces 160 of the reactor vessel pad 130 to the top surface of the riser brace leaf 41a, 41b and the top surface of the brace bolts 81. The primary bearing plate 80 is then machined such that when installed, it will be configured horizontally in the same plane as the upper horizontal bearing surfaces of the reactor vessel pads 130 and bear on the top surface of the riser brace leaf 41a, for example, as shown in FIG. 5. Additionally, small equal-distance gaps 180 may be provided between the primary bearing plate 80 and the top surface of the brace bolts 81, as shown in FIG. 5. These gaps 180 may ensure that the primary bearing plate 80 maintains positive contact with the riser brace leaf 41a. In similar fashion, the secondary bearing plate 90 may be machined such that when installed, it will be configured horizontally in the same plane as the lower horizontal bearing surfaces of the reactor vessel pads 130 and bear on the bottom surface of the inboard and outboard clamp components 60, 70. FIG. 12A is an enlarged view of a primary bearing plate and FIG. 12B an enlarged view of a secondary bearing plate of the exemplary clamp apparatus. As shown in FIGS. 12A and 12B, both of primary and secondary 90 bearing plates 80, 90 may be provided with slotted holes 82, 92 and generally rectangular-shaped cavities 83, 93. These features 82, 83, 92, 93 may allow movement of bearing plate bolts 84, 94, bearing plate bolt keepers 85, 95 and bearing plate inserts 86, 96 (see FIG. 7) relative to the respective primary and secondary bearing plates 80, 90. The half-dovetails 150 machined into the reactor vessel pads 130 have associated machining tolerances. As a result, as the clamp bolts 73 are mechanically preloaded, the inboard and outboard clamp components 60, 70 may rotate slightly about their ‘hinge’ point. As such, a provision is made to allow the bearing plate bolts 84, 94 to move consistent with the movement of the inboard and outboard clamps 60, 70. FIG. 13 is an enlarged view of a bearing plate bolt keeper of the exemplary clamp apparatus; FIG. 14 is an enlarged view of a bearing plate insert of the exemplary clamp apparatus. FIG. 13 shows an exemplary bearing plate bolt keeper 85, it being understood that bearing plate bolt keeper 95 may be of the same construction. Similarly, FIG. 14 shows an exemplary bearing plate insert 86, it being understood that bearing plate insert 96 may be of the same construction. Occasional reference should also be made to FIG. 7. Referring to FIGS. 13 and 14, each of the bearing plate inserts 86, 96 include a counter-bored hole 186 and a keyway 188 to receive the bearing plate keepers 85, 95 and bearing plate bolts 84, 94. The ratchet teeth 88, 98 (not shown) of the bearing plate keepers 85, 95 engage the teeth of the bearing plate bolts 84, 94 in order to prevent loss of mechanical preload in the bearing plate bolts 84, 94. FIG. 8 is an enlarged, sectional top-view of the clamp apparatus in place between the reactor vessel riser brace pad and riser brace leaves. The orientation of the short bearing plate bolt 84, bearing plate keeper 85, bearing plate insert 86, and primary bearing plate 80 may be more clearly shown in FIG. 8. The exemplary clamp assembly 50 may structurally replace any of the ‘RB-1’ welds 143-146 connecting a given riser brace leaf 41a-b/42a-b and the associated reactor vessel pad 130. Unlike conventional riser brace clamps, the clamp assembly 50 does not lend structural support to the adjacent riser brace leaf weld 143-146, but is designed to structurally replace a given weld 143-146. Since the clamp assembly 50 is designed to structurally replace the attachment weld 143-146, it is not necessary that the existing weld 143-146 be accessible for visual inspection after the clamp assembly 50 has been installed. However, since the clamp assembly 50 may obscure the adjacent riser brace leaf weld 143-146, the clamp assembly 50 is designed to be removed for subsequent inspection of both degraded and adjacent riser brace leaf welds 143-146. Therefore, the installed clamp apparatus 50 structurally replaces a weld attaching upper riser brace leaf 41 and/or lower riser brace leaf 42 to reactor vessel pad 130. The riser brace assembly 40 is designed to accommodate the differential thermal expansion that results from reactor start-up and heat-up, and to accommodate the flow-induced vibration that is incumbent in the reactor water recirculation system (not shown) due to reactor recirculation pumps. The exemplary embodiments of the present invention being thus described, it will be obvious that the same may be varied in many ways. 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. |
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050230484 | description | DESCRIPTION OF PREFERRED EMBODIMENTS In order that the invention may be more celarly understood, there will now be described by way of example several embodiments of a fuel rod according to the invention intended for a fuel assembly in a pressurized water nuclear reactor. In all cases, the sheath of the fuel rod according to the invention is produced by the extrusion and then rolling in a step-by-step rolling mill of a blank constituted by a tubular core of zirconium alloy on which is mounted an outer tube having a composition corresponding to the composition of the surface or outer layer defined hereinabove. In its final state, the sheath of the fuel rod according to the invention has the following dimensional characteristics: outside diameter 9.63 mm.+-.0.04 mm, minimum total thickness of the wall of the sheath 0.605 mm, minimum thickness of the surface or outer layer 0.060 mm. EXAMPLES 1, 2 AND 3 The inner tubular layer is made from a zirconium alloy of conventional type and currently employed in the case of the manufacture of sheaths of fuel rods for assemblies intended for pressurized water nuclear reactors. Such a zirconium-base alloy, designated by the name Zircaloy 4, includes 1.2 to 1.7% tin, 0.18 to 0.24% iron, 0.07 to 0.13% chromium, 0.0080 to 0.00200% carbon, 0.0050 to 0.012% silicon and 0.0900 to 0.1600% oxygen, the indicated percentages being percentages by weight, the total of the percentages by weight of the iron and chromium components being between 0.28 and 0.37%. The balance is constituted by the zirconium apart from inevitable impurities in very low proportions. The following table indicates the compositions (in percentages by weight) of three surface layers respectively corresponding to the Examples 1, 2 and 3 of the invention, these layers having, relative to one another, certain differences in composition concerning the addition elements introduced or the percentages by weight of these elements. __________________________________________________________________________ Sn Fe Cr O Nb V Zr __________________________________________________________________________ EX. 1 0.35/0.65 0.22/0.28 -- 0.09/0.16 0.35/0.65 -- BALANCE EX. 2 0.35/0.65 0.35/0.45 -- 0.09/0.16 0.35/0.65 -- BALANCE EX. 3 0.35/0.65 0.55/0.65 -- 0.09/0.16 -- 0.25/0.35 BALANCE __________________________________________________________________________ The compositions of the surface layer of the fuel rods according to the invention are characterized by the presence of tin in a significant proportion of 0.35 to 0.65%, by the presence of iron in a proportion which may vary but which is always between 0.20 and 0.65%, by the absence of chromium which may only be present as residual impurities in a very small amount, and by the presence of niobium or vanadium in significant and well-determined proportions. In all cases, the simultaneous presence of tin and an element such as niobium or vanadium permits obtaining both very satisfactory mechanical characteristics and in particular high hardness and corrosion resistance characteristics comparable to those of zirconium alloys including vanadium and devoid of tin. The vanadium and niobium permit reducing the surface absorption of hydrogen by the sheath and therefore improve the corrosion resistance in the environment of the reactor. After its forming and heat treatment, the duplex sheath of the fuel rod according to the invention has on the whole a homogeneous crystalline structure in the form of a recrystallized phase. EXAMPLES 4, 5 AND 6 In these examples of a fuel rod according to the invention, the inner tubular layer is constituted by a zirconium-base alloy including substantially 1% niobium, to the exclusion of any other metal alloy element in a significant quantity. This inner layer has in all cases the following composition by weight: niobium 0.8 to 1.2%, oxygen 0.09 to 0.16%, the balance being constituted by the zirconium apart from inevitable impurities in very small amounts. The sheaths of the fuel rods according to Examples 4, 5 and 6 differ from one another by the composition of their surface layer. In the case of Example 4, the surface layer has the composition mentioned hereinbefore in Example 1. Likewise, the surface layer of the sheaths of the rods according to Examples 5 and 6 have the compositions mentioned hereinbefore in Examples 2 and 3, respectively. In the final state, the sheath has an entirely recrystallized structure. Tests carried out to ascertain the corrosion resistance at 400.degree. C. have shown that the composite sheaths of the rods according to the invention have characteristics which are distinctly improved over those of sheaths of Zircaloy 4. Moreover, the resistance to creep at 400.degree. C. of the sheaths of fuel rods comprising an inner layer of zirconium-niobium alloy is very much higher than the resistance to creep of homogeneous or composite sheaths of Zircaloy 4. Furthermore, according to a particular advantage of the invention, the alloy Zr-Nb markedly reduces the risk of corrosion under stress due to the interaction between the pellet and the sheath, since this alloy has a lower relative ductility loss than that of alloys of the prior art. In all cases, the hardness of the surface layer at low or high temperature is very much higher than the hardness of the corresponding surface layer of composite sheaths according to the prior art. The scope of the invention is not intended to be limited to the described examples. Thus, it is possible to employ an inner layer constituted by a zirconium alloy such as Zircaloy 2 including 1.2 to 1.7% tin, 0.07 to 0.2% iron, 0.05 to 0.15% chromium, 0.03 to 0.08% nickel and 0.07 to 0.15% oxygen, the sum of the percentages by weight of iron, chromium and nickel being between 0.18 and 0.38%. It is also possible, as concerns the surface or outer layer, to select more precise composition limits within the limits given hereinbefore. The fuel rods according to the invention may be employed both in the case of fuel assemblies for pressurized water nuclear reactors and in the case of fuel assemblies for boiling water nuclear reactors. |
claims | 1. A thermionic (TI) power cell, comprising:a layer of radioactive material that generates heat due to radioactive decay;a layer of electron emitting material disposed on the layer of radioactive material; anda layer of electron collecting material, wherein the layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material, wherein the chamber is substantially evacuated to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material, and further wherein heat generated over time by the layer of radioactive material causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material to induce an electric current to flow through the layer of electron collecting material when the layer of electron collecting material is connected to an electrical load. 2. The TI power cell of claim 1, wherein the layer of electron emitting material includes an array of spikes to concentrate the electrons emitted by the layer of electron emitting material at tips of the spikes, wherein the tips of the spikes point toward the layer of electron collecting material. 3. The TI power cell of claim 2, wherein the tips of the spikes are separated from one another by a lateral spacing of approximately 100 micrometers to approximately 1 millimeter. 4. The TI power cell of claim 2, wherein the chamber is defined by a gap of approximately 100 micrometers to approximately 1 millimeter between the tips of the spikes and the layer of electron collecting material. 5. The TI power cell of claim 2, further comprising a layer of spacer material disposed between the layer of electron emitting material and the layer of electron collecting material,wherein the layer of spacer material exposes the tips of the spikes so that the exposed tips are disposed in the chamber. 6. The TI power cell of claim 1, further comprising:a first terminal coupled to the layer of electron emitting material; anda second terminal coupled to the layer of electron collecting material to induce the electric current from the first terminal to the electrical load and from the electrical load to the second terminal. 7. The TI power cell of claim 1, further comprising a layer of insulating material disposed between the layer of radioactive material and the layer of electron emitting material. 8. The TI power cell of claim 1, wherein:the layer of electron emitting material encapsulates the layer of radioactive material; andthe layer of electron collecting material surrounds the layer of electron emitting material. 9. The TI power cell of claim 1, wherein the layer of radioactive material includes a thin plate of plutonium-238. 10. The TI power cell of claim 1, wherein the layer of radioactive material, the layer of electron emitting material, and the layer of electron collecting material are enclosed by an outer shell. 11. A method for generating an electric current, comprising:heating a layer of electron emitting material disposed on a layer of radioactive material by radioactive decay of the layer of radioactive material;emitting electrons from the layer of electron emitting material to a layer of electron collecting material by thermionic emission, wherein the layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material, wherein the chamber is substantially evacuated to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material; andinducing an electric current to flow through the layer of electron collecting material connected to an electrical load, wherein heat generated over time by the layer of radioactive material causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material. 12. The method of claim 11, wherein emitting the electrons includes emitting electrons from an array of spikes disposed on the layer of electron emitting material to concentrate the electrons emitted by the layer of electron emitting material at tips of the spikes, wherein the tips of the spikes point toward the layer of electron collecting material. 13. The method of claim 12, wherein emitting the electrons includes emitting electrons from the tips of the spikes that are separated from one another by a lateral separation of approximately 100 micrometers to approximately 1 millimeter. 14. The method of claim 12, wherein emitting the electrons includes emitting electrons from the tips of the spikes to the layer of electron collecting material that are separated by a gap of approximately 100 micrometers to approximately 1 millimeter. 15. The method of claim 12, wherein emitting the electrons includes emitting electrons from the tips of the spikes that are exposed by a layer of spacer material disposed between the layer of electron emitting material and the layer of electron collecting material to the layer of electron collecting material. 16. The method of claim 11, wherein inducing the electric current includes inducing the electric current to flow from a first terminal coupled to the layer of electron emitting material to the electrical load and from the electrical load to a second terminal coupled to the layer of electron collecting material. 17. The method of claim 11, wherein a layer of insulating material is disposed between the layer of radioactive material and the layer of electron emitting material. 18. The method of claim 11, wherein:the layer of electron emitting material encapsulates the layer of radioactive material; andthe layer of electron collecting material surrounds the layer of electron emitting material. 19. A thermionic (TI) power cell, comprising:a heat source, wherein the heat source includes an exhaust manifold;a heat conductive layer that provides heat from the heat source;a layer of electron emitting material disposed on the heat conductive layer; anda layer of electron collecting material, wherein the layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material, wherein the chamber is substantially evacuated to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material, and further wherein heat generated over time by the heat source causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material to induce an electric current to flow through the layer of electron collecting material when the layer of electron collecting material is connected to an electrical load. |
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claims | 1. A system for manufacturing a radioisotope with improved specific activity comprising:a target material;a target material holder;a proton beam; anda material holder mounting flange capable of measuring a proton beam current of the target material for beam steering;wherein,the target material comprises a target material shape or a target material area;the proton beam comprises a proton beam strike area or a proton beam strike shape; andthe target material area or the target material shape matches the proton beam strike area or the proton beam strike shape, resulting in matching of the target material and the proton beam. 2. The system of claim 1, whereinthe target material holder comprises a deionized water cooling system;the deionized water cooling system provides cooling water and removes the cooling water; orthe cooling water is deionized, having a resistivity of about 7.5 MΩ or greater than about 7.5 MΩ, preventing or reducing radioisotope contamination of the cooling water. 3. The system of claim 1, comprising:(i) polytetrafluoroethylene (PTFE) coated vessels and PTFE coated connectors;(ii) vacuum drives, pressure drives, and syringe drives resulting in a flow of chemicals through the system and enabling consistent target material recovery and radioisotope yield;(iii) a dissolution vessel comprising a PTFE gate valve for containing HCl vapor; or(iv) a dissolution vessel comprising PTFE and a cooling fin, wherein the dissolution vessel comprises a conical bottom and a PTFE spacer, wherein the PTFE spacer eliminates or prevents blockage of a fluid pathway by the target material or the target material. 4. The system of claim 1, whereinthe target material is mounted to a target material holder via an insulator;the target material comprises gold or platinum;the target material is keyed to orient the target material with the proton beam strike area, resulting in a keyed target material;the target material holder is designed to accept a keyed target material; orthe target material holder orients the target material to the proton beam strike area of the proton beam. |
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description | With an X-ray point source and a 2D-detector array, X-rays intersecting a spherical object form a cone, giving rise to the nomenclature xe2x80x9ccone-beam tomographyxe2x80x9d. The cone-beam approach is desirable for faster data collection, higher image resolution, better radiation utilization and easier hardware implementation, therefore it attracts more and more attention in material, biological, medical and other studies. Despite progress in exact cone-beam reconstruction, approximate cone-beam algorithms remain important. The advantages of approximate cone-beam reconstruction include the following. First, incomplete scanning loci can be used. The completeness condition for exact reconstruction requires that there exist at least a source position on any plane intersecting an object to be reconstructed. In many cases of X-ray CT, this condition cannot be satisfied. Second, partial detection coverage is permissible. In exact cone-beam reconstruction, the cone-beam is assumed to cover an object entirely from any source position. However, complete detection coverage is generally impossible in medial X-ray CT. Third, computational efficiency is high. Because of the partial detection, approximate reconstruction involves much less raw data. The computational structure of Feldkamp-type approximate cone-beam reconstruction is fairly straightforward, highly parallel, hardware-supported, and particularly fast for reconstruction of a small region of interest (ROI). Fourth, image noise and ringing artifacts can be less. With the 3D Fourier method, we found that exact cone-beam reconstruction produced more ringing as compared to the Feldkamp method. This type of ringing is believed to be inherent to all exact cone-beam reconstruction formulas that take the second derivative data. The system uses a novel, generalized Feldkamp algorithm. The Feldkamp algorithm [Feldkamp et al., 1984], which has been the most popular approximate cone-beam algorithm. In the present system, the Feldkamp cone-beam algorithm is generalized to allow simultaneous handling of continuous data streams from multiple X-ray sources for improved temporal resolution. The generalized Feldkamp cone-beam algorithm can be adapted into special cases, including helical/helix-like cone-beam scanning. The X-ray CT fluoroscopy (CTF) is to perform X-ray tomographic imaging in real-time to enable image guidance of interventions, synchronization of scanning with contrast bolus arrival, and motion analysis, particularly functional imaging, as well as other applications. However, filtered backprojection, the current method for CTF image reconstruction, is subject to increased image noise associated with reduced tube current, as well as motion and metal artifacts from implants, needles or other surgical instruments. The system also uses a known row-action/ordered-subset EM algorithm for CTF. Because time-dependent variation in images is localized during CTF, the row-action EM CTF algorithm converges rapidly. Also, this iterative CTF algorithm effectively suppresses image noise in both numerical simulation and real data experiments [Wang et al., 1999]. Fiber coupled CCD systems, lens coupled CCD systems, and COMS detector systems and other types of detection systems suitable for use in the 4D micro-CT scanner are preferably x-ray quantum noise limited and provide high spatial resolution, wide dynamic range, and high contrast sensitivity. A stereo-image guidance system can be included. Such a system can include, for example, two 1kxc3x971k frame-transfer CCDs, each acquiring 30 frames per second. The electronic system regulates the data flow of the multiple detectors and integrates real-time frame grabbing, image processing and display. The volumetric CT fluoroscopy (VCTF) system produces sufficient temporal, spatial and contrast resolution for small animal studies. The elements of the system include the VCTF scanner device and a Feldkamp-type software package with optimized system/algorithm parameters. The data acquisition system consists of five pairs of an x-ray tube and a 2D CCD camera or another type of 2D detection system, which is also referred to as a five-star data acquisition system. The number of x-ray sources can also be other integers, such as 3, 7, 8, and so on. Additional filtration can be added if it is needed for a scan of a specific subject. The rotation required for cone-beam CT is provided by a motorized stage. The source-to-axis distance is fixed at 90 cm in the initial prototype, and the detector-to-axis distance is adjustable from 10-60 cm through precision translation stages. This unique mechanism allows a tradeoff between the spatial resolution and the field of view in specific studies. The positions of these components are aligned under an optical collimator, as known in the art. By combination of this configuration and a Feldkamp-type reconstruction software package, the micro-CT fluoroscopy system is believed capable of a temporal resolution of about 0.1 second and a spatial resolution down to 0.14 mm. In the Feldkamp-type reconstruction framework, the cone-beam reconstruction is essentially handled as a fan-beam reconstruction problem In fan-beam geometry, two sets of complete projections are collected during a full-scan (360xc2x0). It is known that one complete set of projections is obtained over a half-scan (180xc2x0 plus two fan-angles). Hence, using our five-star data acquisition system, approximately a one-tenth of a full scan (about 40xc2x0) is needed to collect a complete set of projections for reconstruction of a volume in cone-beam geometry. It is also known in the art that the number of projections in a complete data set should be determined as a function of detector parameters. To reconstruct a volume of 2563 voxels, there should be about 200 projections in a complete data set. Therefore, each of the five CCD cameras should capture 40 frames (200/5) per one-fifth scan. Let the data acquisition system rotate 360xc2x0 every 2 seconds that is mechanically feasible with conventional techniques, a data-rate of 200 frames per second is required of the CCD camera. With these settings, a complete data set can be gathered in about 0.2 seconds, which is 2-3 times faster than prior CT fluoroscopy systems. A reconstructed image can be updated within a fraction of a half-scan in the context of CT fluoroscopy because time-dependent image variation is spatially localized. Therefore, we estimate that the temporal resolution of the proposed system would be about 0.1 second or less. The data acquisition module is based on advanced but well-known frame-transfer CCD technology or other suitable data acquisition techniques. The preferred CCD detector array acquires digital data at a rate of 60 frames per second, 1024xc3x971024 pixels per frame, or an even better performance. Using frame transfer CCD, the exposure duty cycle of the imaging system is increased by nearly 100 times as compared to conventional CCD technology. In a 4xc3x974 binning mode (256xc3x97256), the detector array acquired 240 frames per second. The module includes a CsI (T1) scintillator (Hamamatsu, Bridgewater, N.J.), a 2.5:1 optical fiber taper (Income Fiber Optics, Mass.), and a frame transfer CCD (MedOptics, Ariz.). The pixel size of the CCD is 0.024 mm, therefore in a 4xc3x974 binning mode, the spatial resolution of the detector module (on the surface of the scintillator) is about 0.24 mm (Given an optical magnification of 2.5 times, the resolution is 0.024xc3x974xc3x972.5=0.24 mm). As mentioned above, the detector-to-axis distance can be specified by a user between 10 and 60 cm, (or other preferred distance range), relative to a source-to-axis distance of 90 cm (or another preferred distance). High precision stepping motors and closed-loop control devices are utilized to move detectors and sources to adjust detector-to-axis distances, and source-to-axis distances. Slipping ring technologies and closed-loop control devices are also utilized to control the rotation of the assembly of the detectors and the sources. This unique mechanism allows a tradeoff between the spatial resolution and the field of view in specific studies. For instance, with a detector-to-axis distance of 60 cm, the spatial resolution is maximized to 0.14 mm, while the field of view is 3.7 cm in diameter. With a detector-to-axis distance of 10 cm, the field of view is maximized to 5.5 cm in diameter, while the spatial resolution is degraded to about 0.22 mm. Each detector is equipped with a thermal-electric cooler. The overall additive noise (read noise and thermal noise) at the above frame rate is less than 100 electrons. The total quantum gain of the cascaded CsI-fiber-CCD chain is about 19 electrons for each x-ray photon absorbed by the scintillator. Based on the measurement of a current fiber coupled CCD prototype using an identical CsI (T1) scintillator, the detective quantum efficiency (DQE) of the detector module is estimated to be 70. FIG. 1 is a block diagram of the data acquisition, preprocessing, transmission and storage system The system includes five CCD cameras. Each CCD camera acquires 240 frames (256xc3x97256xc3x9712 bits) per second, hence the entire system operates at 1200 frames per second, generating data at a rate of 150 MB per second. In the intended applications, the imaging duration is typically 3 to 5 seconds and repeated as many as 5 times for certain procedures, defining a storage requirement of roughly 3-5 GB per animal. The digital data from each CCD camera are read into a preprocessing chip (Far West Sensor Corp., Garden Grove, Calif.), which performs real-time pixel-wise calculations. The CCD-to-CCD uniformity and geometrical and other corrections will be made xe2x80x9con the flyxe2x80x9d using this chip. A multiplexer (MUX) selects the preprocessed frames, and routes the data to the on-board memory of a C80 board (Model: Genesis; Matrox Electronic Systems Ltd., Doval, Quebec, Canada) at a sustained rate of 400 MB per second. The board manages two concurrent data streams: one to a real-time display and the other to a host memory from where the data stream is written to the redundant array independent disks (RAID; Storage Concept, Irvine, Calif.). A cluster of five RAID devices will be utilized corresponding to each of the five CCD cameras. Each of the selected RAID devices is capable of storing 32 GB data with a sustained bandwidth of 35 MB per second. The throughput of the selected RAID systems exceeds the input data throughput, as required. The image grabbing, multiplexing and display is handled by the Matron Image Library (MIL) software utilities. The PCI board (Matrix Genesis) integrates real-time frame grabbing, preprocessing and display based on the commercially available TMS320C80 technology or other suitable technology. Filtered backprojection is a well-known image reconstruction method for CTF/CT. As used herein, the term xe2x80x9cFeldkamp-type reconstructionxe2x80x9d is intended to refer to a ID filtered backprojection mechanism for image reconstruction in cone-beam geometry. The generalized Feldkamp algorithm [Wang et al., 1993], several other practical cone-beam algorithms [Gullberg and Zeng, 1992, Yan and Leahy, 1992], as well as spiral CT algorithms [Crawford and King, 1990, Taguchi and Aradate, 1998] can be regarded as special cases of the Feldkamp-type reconstruction. In the illustrated embodiment of the invention, the Feldkamp-type reconstruction approach is used for real-time volumetric X-ray imaging. In conventional Feldkamp-type cone-beam reconstruction, a transaxial slice is reconstructed using projection data collected form a 360xc2x0 angular range (full-scan). In conventional fan-beam reconstruction, there are two complete sets of projection data over a full-scan range. These two sets are redundant, because exact reconstruction can be achieved just using projection data of 180xc2x0 plus two fan-angles (half-scan). Although projection data are insufficient for accurate and reliable construction of off-mid-plane structures using traditional Feldkamp-type algorithms, it can be intuitively appreciated that there are xe2x80x9capproximate redundancyxe2x80x9d in the data acquired along geometric rays that would be identical in the absence of any fan-beam tilting angle and any longitudinal translation between the X-ray tube and the object being scanned. In other words, the xe2x80x9credundantxe2x80x9d data are acquired along the X-ray paths having the same horizontally projected line but in opposite directions. There are many possible weight functions for half-scan fan-beam image reconstruction, such as Parker""s weight function and Gullberg and Zeng""s weight function. The illustrated embodiment of the invention utilizes our generalized Parker weight function. As shown in FIG. 2, the equiangular fan-beam geometry is assumed, where, xcex2 denotes the angular position of an X-ray source, xcex3 the angular position of a detector, and xcex94 the fan-beam angle. FIG. 3 summarizes Parker""s classic design of the single-source half-scan weighting function. In FIG. 3, the upper and lower triangles are sampled twice; hence the data in the two regions must be combined for doubly sampled Radon locations to make a unit contribution in image reconstruction. Specifically, the weighting scheme Parker proposed is described as follows: w xe2x80x83 ( α , β ) = { sin 2 xe2x80x83 ( π 4 xe2x80x83 β Δ - α ) , 0 ≤ β ≤ 2 xe2x80x83 Δ - 2 xe2x80x83 α ; sin 2 xe2x80x83 ( π 4 xe2x80x83 π + 2 xe2x80x83 Δ - β Δ + α ) , π - 2 xe2x80x83 α ≤ β ≤ π + 2 xe2x80x83 Δ ; 1 , 2 xe2x80x83 Δ - 2 xe2x80x83 α ≤ β ≤ π - 2 xe2x80x83 α . We have generalized Parker""s weighting scheme into the case of N x-ray sources and cone-beam geometry [Liu et al., 2001]. In the case of N x-ray sources that are symmetrically distributed with respect to the reconstruction system origin, for the optimal temporal resolution the minimum source angular range should be used to collect a set of complete projection data. As shown in FIGS. 4 and 5 for the case of N=5, the minimum source angular range is xcfx80/N+2xcex94. We have generalized Parker""s weighting scheme into the case of N x-ray sources: w xe2x80x83 ( α , β ; i ) = { sin 2 xe2x80x83 ( π 4 xe2x80x83 β - 2 i xe2x80x83 π / N Δ - α ) , 2 i xe2x80x83 π / N ≤ β ≤ 2 i xe2x80x83 π / N + 2 xe2x80x83 Δ - 2 xe2x80x83 α ; sin 2 xe2x80x83 ( π 4 xe2x80x83 ( 2 i + 1 ) xe2x80x83 π / N + 2 xe2x80x83 Δ - β Δ + α ) , ( 2 i + 1 ) xe2x80x83 π / N - 2 xe2x80x83 α ≤ β ≤ ( 2 i + 1 ) xe2x80x83 π / N + 2 xe2x80x83 Δ ; 0 , ( 2 i + 1 ) xe2x80x83 π / N + 2 xe2x80x83 Δ ≤ β ≤ ( 2 i + 2 ) xe2x80x83 π / N ; 1 , otherwise , where i=0, . . . ,Nxe2x88x921. It can be verified that after the N-source half-scan weighting the weight is a unit at each Radon location, and continuous at the boundaries of the redundant regions. The following five-star half-scan generalized Feldkamp-type cone-beam reconstruction formula is then obtained: g xe2x80x83 ( x , y , z ; t ) = 1 2 xe2x80x83 ∑ i = 0 4 xe2x80x83 ∫ ω xe2x80x83 ( t - t 0 ) + 2 i xe2x80x83 π / 5 ω xe2x80x83 ( t - t 0 ) + ( 2 i + 1 ) xe2x80x83 π / 5 R 2 ( R - v ) 2 xe2x80x83 ∫ - ∞ ∞ w xe2x80x83 ( α , β ; i ) xe2x80x83 D xe2x80x83 ( β , p , ζ ; i ) xe2x80x83 f xe2x80x83 ( Ru R - v - p ) xe2x80x83 R R 2 + p 2 + ς 2 ⅆ p ⅆ β , xe2x80x83 where g(x,y,z;t) represents a time-varying image volume, R the source-to-origin distance, xcex2 the angular source position, D(.) cone-beam projection data, u=x cos xcex2+y sin xcex2, xcexd=xe2x88x92x sin xcex2+y cos xcex2, xcex6=Rz/(Rxe2x88x92xcexd), f(.) is the ramp filter, xcfx89 is the speed of the X-ray source rotation, time t greater than t0=(xcfx80/N+2xcex3m)/xcfx89, xcex3m the fan-angle in the mid-plane. Clearly, the reconstructed image g(x,y,z;t) is assumed to be a function of time, and so is the projection data. If an object to be reconstructed is motionless, there would be no discontinuities among N=5 subsets/segments of consecutive projections. However, inconsistency among adjacent projections, especially among N=5 segments of projections, can be taken into account and effectively suppressed to further suppress motion artifacts. Therefore, it would be useful to: (1) make use of a complete set of projection data from a minimum time span, and (2) approximately combine overlapping projection data from different segments so that any major jumps are filtered out. Alternative reconstruction methods can be employed. After projection data are acquired in real-time over an extended period, there are two options for image reconstruction: on-line and off-line. The on-line reconstruction is important for interventional procedures that demand immediate feedback for optimal results. The off-line reconstruction is relatively less critical in terms of computational time. In either mode of image reconstruction, a fast speed is desirable. Reasonably fast off-line image reconstruction is presently contemplated. The alternative real-time image reconstruction strategy is to utilize special hardware and/or optimized methods, especially dedicated 3D backprojectors. Special cards that may be suitable are commercially available from TeraRecon Inc. (San Mateo, Calif., USA; http://www.terarecon.com) which take 15 seconds to reconstruct an image volume of 2563 voxels from 288 projections. Numerical simulations have been conducted to test the real-time volumetric CT algorithm. Using synthesized idealized objects with known contrast dynamics and geometric features, error components were numerically generated with respect to data acquisition and image reconstruction parameters. FIG. 6 shows numerical simulation that demonstrates superior temporal resolution using the five-star data acquisition system and the five-star Feldkamp-type reconstruction algorithm outlined in FIG. 7. |
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048448591 | description | DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 shows the vessel 1 of a pressurized-water nuclear reactor, inside which is arranged the reactor core 2 consisting of a set of fuel assemblies 3 arranged vertically and resting on the lower core plate 4 by means of their bottom end fittings. Located above the core 2 is the upper core plate 6 which is perforated with orifices, each level with a respective fuel assembly, and on which rest the guide tubes 8 arranged vertically above some of the core assemblies. Placed above the hemispherical cover 10 of the vessel 1 are mechanisms (not shown) for moving control rods in the form of a cluster, which are connected to the lower end of drive shafts 9 on which the action of the mechanisms for moving the control rods is exerted. The control rods can move inside the fuel assemblies 3, in tubes which replace certain fuel pencils in the network of these assemblies, in order to control the reactivity of the core 2. As can be seen in more detail in FIG. 2, the guide tubes 8 are composed of a lower part 11, hereinafter called a guide, resting on a support plate 13 parallel to the upper core plate 6 and engaged in the core plate 6, and of an upper part 12, hereinafter called a tube, fastened to the support plate 13. The support plates 6 and 13 are connected to one another by means of tubular spacers 16 perforated with orifices 17 for the circulation of cooling fluid consisting of the pressurized water filling the reactor vessel. By means of these spacers 16, the upper internal equipment forms a rigid assembly integral with the support plate 13. Arranged inside each of the guide tubes 8 and over their entire upper part are discontinuous guide devices consisting of perforated plates 18 located at a uniform distance from one another over the length of the guide 11 and in the lower part of the tube 12. The bottom part 19 of the guide 11 forms a device for the continuous guidance of the control rods, with perforations which are in the extension of the perforations of the discontinuous devices 18. The part 19 of the guide consists of sleeves occupying the entire height of the zone 19 and having vertical channels guiding the control rod. This zone 19, without a tubular casing, thus allows most of the coolants fluid which has passes through the adjacent fuel assemblies 3 to mix with the portion of coolant fluid circulating via the orifices 17, so as to be directed towards a steam generator (not shown). If the zone 19 has a tubular casing, it is obvious that lateral orifices will be made in this casing to allow the coolant fluid to be discharged. The control rods consist of a cluster of absorbent pencils which are connected in their upper part by means of a crossbrace or a spider support, itself connected to the lower part of the drive shafts of the follower 9. Arranged in the upper part of the tube 12 is a plate 20 which has a guide ring 21. As explained above, this ring 21 must be removable, so that, during maintenance operations on the equipment, it allows the passage of the end part of the follower 9 which has a larger cross-section in the region of its connection to the spider support of the clusters. Nevertheless, during operation, this ring 21 must ensure the guidance of the follower 9, to prevent the latter from experiencing substantial lateral movements which would risk causing faulty insertion of the control clusters. The ring 21 also has to perform the function of a flow restrictor, to prevent the portion of coolant present in the guide tube 8 from escaping into the space contained between the upper plate 13 and the vessel cover 10. The ring 21 must therefore be firmly locked on the plate 20 inside its orifice. FIG. 3 shows the guide ring 21 in the locked position inside the orifice 22 in the end plate 20 of a tube 12. This guide ring comprises a tubular body 25, whose lower part 25a is engaged in the orifice 22 and the upper part 25b rests on the upper face of the plate 20. In its upper part 25b, the tubular body 25 has an annular recess 27 and three ports 28 arranged at 120.degree., only one of which has been shown in FIG. 3. A closing piece 26 having an external thread is screwed into a corresponding tapping 29 machined in the inner surface of the tubular body 25. This closing piece 26, fastened rigidly to the part 25b of the tubular body, forms an integral part of the guide ring and has an internal bore 30 which ensures the guidance of the follower and restriction of the flow at the outlet of the guide tube. The piece 26 also ensures that the annular recess 27 is closed off. The lower part 26a of the closing and guide piece 26 has a frusto-conical surface which comes in contact with a corresponding frusto-conical surface machined on the inner surface of the tubular body 25, when these two parts are joined together rigidly. This ensures perfect centering of the piece 26 in the tubular body 25 and consequently in the orifice 22 in the plate 20 of the tube 12. The axis ZZ' of the guide ring then coincides with the axis of the orifice 22 which itself coincides with the axis of the guide tube and of the corresponding fuel assembly. As can be seen in FIGS. 3 and 4, the lower part 25a of the tubular body has three grooves 32 at 120.degree., which pass through its wall over its entire thickness. These grooves 32 extend towards the top of the tubular body 25, up to the upper part of the inner wall of the annular recess 27, opening into this recess 27, each opposite a port 28 passing through the outer wall of the recess 27. The grooves 32, in their lower part, each open into a cylindrical aperture 33, the axis 34 of which is inclined relative to the horizontal. The cylindrical aperture 33 opens into a rectangular slot 35 machined in the outer part of the tubular body 25 over a certain height and to a width corresponding to the diameter of the cylindrical aperture 33. When the guide ring 21 is in position in the orifice 22 in the plate 20, as illustrated in FIG. 3, the cylindrical aperture 33 opens out in the region of the lower face of the plate 20. A claw 40, such as that shown in FIG. 7, is arranged in each of the cavities consisting of a cylindrical aperture 33, a slot 35, a groove 32 and the corresponding port 28. The claw 40 takes the form of a bent lever comprising a first arm 41 ending in an enlarged portion 43 and a second arm 42 forming an angle of 90.degree. relative to the arm 41. The enlarged portion 43 comprises a cylindrical part 44, the diameter of which corresponds to the diameter of the cylindrical aperture 33 and the axis of which is inclined relative to the horizontal and relative to the arm 41 of the bent lever. This cylindrical part 44 ends in a chamfer 47 of convex surface, forming the bearing and attachment surface of the claw 40. The convex surface 47, because of its shape, interacts perfectly with the profile of the lower surface of the hole 22. It can be seen in FIG. 3 that, in the operating position, the arm 41 of the claw is engaged in a groove 32, the arm 42 passing through the corresponding port 28 and projecting on the outside of the tubular body 25 of the guide ring. The claws 40 are mounted completely freely inside the tubular body 25 and are held in place in this tubular body by means of a helical spring 45 which bears at one of its ends on the bottom of the annular recess 27 of the tubular body 25 and at its other end on the arms 42 of the claws 40 by means of a bearing ring 46. The spring 45 is pre-stressed at the time of assembly, so as to exert a vertical force directed upwards on the arms 42 of the claws 40, in order to return them into an upper position, in which the enlarged portion 43 of the claw and its surface 47 project outwards relative to the outer surface of the lower part 25a of the tubular body 25. In particular, when the guide ring is fitted in the orifice 22, as shown in FIG. 3, the spring makes it possible to lock the claw in the attachment position by means of its surface 47 on the lower edge of the orifice 22 having a frusto-conical bearing surface. In this locking position, the cylindrical part 44 of the enlarged portion 43 partially enters the slot 35, into which the cylindrical aperture 33 opens. The ring 21 can be released simply by pushing from the top downwards on the end of the arms 42 of the claws 40. The spring 45 is then compressed, and the enlarged end portion 43 of the claw 40 is moved downwards, so that the surface 47 is separated from the corresponding surface of the plate 20. As a result of a lever effect, since it bears on the ring 46 at the end of the spring 45, the claw 40 pivots in such a way that the enlarged portion 43 is moved towards the inside of the tubular body 25. This pivoting is possible as soon as the cylindrical part 44 of the enlarged portion 43 comes level with the cylindrical aperture 33. The claw can then be retracted completely within the wall 25a of the tubular body 25 inside the aperture 33 because of the presence of the frusto-conical surface 26a which allows the claw 40 to tilt by pivoting. The guide ring 21 can then be extracted from the orifice 22 in the plate 20 of the tube 12. The spring is kept compressed by means of a clamping tool introduced into a notch 48 which also allows the guide ring to be gripped in order to extract it from or reinstall it in the orifice 22. It should be noted that, in the locking position illustrated in FIG. 3, the claws 40 cannot move in the radial direction, part of the enlarged portion 43 then being engaged in the slot 35, into which opens the groove 32, the transverse dimension of which is less than the transverse dimension of the enlarged portion 43. The ring 21 can only be released by moving the claw 40 downwards counter to the force exerted by the spring 45. When the ring 21 has been released, the claws 40 are returned to their inactive upper position, in which the arms 42, under the effect of the spring 45, bear on the upper edge of the corresponding ports 28 and under the upper rim of the closing piece 26. To fit and lock the ring 21 in the orifice 22 in a plate 20, the claws 40 are previously retracted by pushing the end of the arms 42 and keeping the spring 45 compressed by means of a gripping tool introduced into the notch 48. The part 25a of the tubular body 25 is inserted into the orifice 22, and the shoulder of the part 25b of this tubular body comes up against the upper surface of the plate 20. The end of the arms 42 of the claws 40 is then set free, and the latter are pushed back upwards by the spring 45 which also causes these claws to tilt, in such a way that the enlarged end portion 43 is pushed outwards and its surface 47 comes in contact with the edge of the orifice 22. The guide ring 21 is then once again in its locking position, shown in FIG. 3. It is also possible to introduce and lock the guide ring 21 without previously retracting the claws 40. The locking ring is brought into position on the orifice 22, the lower surface of the enlarged portions 43 coming up against the upper edge of the orifice 22. A push is then exerted on the end of the arms 42 of the claws 40, so as to compress the spring 45 and move the extreme end of the claws inwards. The ring 21 is snapped in and locked in this way. The main advantages of the invention are that the device is particularly simple, its tubular body does not have any movable parts, and the locking and release operations are especially simple to carry out. The invention is not limited to the embodiment which has been described. Thus, it is possible to have claws and a tubular body of a form different from that described, and the angle of the arms of the lever forming the claw may be other than from 90.degree., and the shape of the end attachment part different from that described. Likewise, the tubular body may have slots and apertures of a different shape matching the shape of the claws used. It is possible to use a single spring common to all the claws or, on the contrary, several elastic devices, such as springs, associated with each of the claws. The number of claws may be other than three, but there must be at least two. The structure of the guide ring may differ from that described which had a closing piece 26 screwed on the tubular body 25, this piece 26 making it possible to fit the claws and the thrust spring easily inside an annular recess 27 of the tubular body 25. It would be just as useful to have a closing piece welded to the tubular body after the spring and claws have been fitted. It would also be possible to have a tubular piece having one or more recesses for springs bearing on the claws and having a form different from that of an annular recess. Finally, the guide ring according to the invention can have uses other than that relating to a guide tube of a pressurized-water nuclear reactor. |
061817724 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention relates to a new method of manufacturing an X-ray grid structure. The present invention additionally relates to a new and improved X-ray grid structure for assembly with a cassette, with the X-ray grid structure having a simplified structure and cost of manufacture. The grid structure may be a one-piece grid structure or a two-piece grid structure. One-piece Grid Structure A first embodiment is a one-piece, protective anti-scatter grid structure for protectively housing an X-ray cassette therein includes a flat top panel having a size adapted to support an X-ray cassette. From the flat top panel having a generally rectangular shape, the grid structure may be formed. An upper ledge is formed as part of the top panel. A lower ledge is vertically spaced therefrom and sized for under lapping and supporting a cassette therein. A side bar or elongated member connects the lower ledge or bottom edge to the top panel. There are three side bars, one on each of three sides of the anti-static grid structure. The anti-scatter grid structure is thoroughly described in the U.S. Pat. No. 4,706,269 to Leo J. Reina et al., the said Leo J. Reina being the inventor in this application. This application provides for the improvement based on the indicated patent in that a one- piece anti-scatter grid structure, with open corners is provided. By open corners is meant the X-ray grid structure has a portion of each corner removed. The open corners provide for ease of manufacture for the one piece X-ray grid structure, while still providing for good protection of the cassette. If the grid in the holder is ever damaged, such damage must come be from a massive blow to it, so that it will crush the X-ray grid structure itself. One of the inventive concepts here disclosed embodies the idea that the droppage impact is distributed through the holder and not the grid thereby lengthening the life of the grid compared with the prior art devices. Two-piece Grid Structure A second embodiment of this grid for an x-ray cassette is a two piece embodiment. There is a top piece of a generally rectangular shape adapted to receive the cassette. The corners of the top piece are open. That is, there is a forty-five degree angle on each corner. The top piece is solid. The lower piece has an open large surface and extended open corners. The lower piece is nestable within the upper or top piece and sandwiches the x-ray cassette therebetween. A snapping mechanism on the edge of the corners fits into the open corner of the top piece and removably locks the two pieces together sandwiching the x-ray cassette therebetween. In this fashion, the x-ray cassette can be efficiently assembled. The open corners for the assembled package provide for protection and ease of assembly. In this fashion, advantages are achieved, for protection and ease of assembly. The upper member or top piece has flanges at a right angle to the top panel. The four flanges lack a connection with its corresponding perpendicular member in order to provide for the opening in each corner. The wall portion includes an open top. The open top surface is adapted to permit the x-ray cassette to be used. The open top surface provides for a top ridge perpendicular to each of the four corners. At each of the four corners, may be an extended snap mechanism designed to be received by the open corners of the upper or top piece. The top ridge is adjacent to the open top. This structure permits cooperation with the top member. The X-ray cassette can then be held therebetween and within the grid assembly, when used in combination with the top cover. Preferably, a releasable adhesive holds the lower piece in the top piece. If the adhesive wears off, it may easily be replaced. Such adhesive provides easier manufacture than the snap mechanism. In summary, it is very important that the grid be maintained in a damage free state. These grids require real protection. This new X-ray grid structures and its new method of manufacture provide a vastly improved performance. It also has a far superior useful life over any other device of its kind. Referring now to FIG. 1, FIG. 2 and FIG. 3, a one piece X-ray grid structure 100 embodies important features of this invention. The one piece X-ray grid structure 100 is particularly constructed for assembly with an X-ray cassette 110. The one piece X-ray grid structure 100 includes a top rectangular panel 120. This flat top panel 120 has a first elongated member 122, a second elongated member 124, and a third elongated member 126 each extending from an edge of flat panel 120 to protectively encase the X-ray cassette 110 against impact forces, which may be applied to the panel 120 in a circumstance where the panel 120 might be dropped or given rough handling by an X-ray technician when being removed from storage or placed into storage. More particularly, first elongated member 122 extends from first panel edge 130 of flat top panel 120. In a like fashion, second elongated member 124 extends from second panel edge 132 of flat top panel 120. Similarly, third elongated member 126 extends from third panel edge 134 of flat panel 120. The one-piece grid structure 100 protectively encases the X-ray cassette 110 against impact forces, which may be applied to the panel 120 in a circumstance where the panel 120 might be dropped or given rough handling by an X-ray technician when being removed from storage or placed into storage. A first bottom edge 140, a second bottom edge 142 and a third bottom edge 144 provide a squared u-shaped frame around three side edges of the panel 120. First bottom edge 140 extends from first elongated member 122. Second bottom edge 142 extends from second elongated member 124. Third bottom edge 144 extends from third elongated member 126. Thus, a lower ledge is vertically spaced from panel 120 and sized for underlapping and supporting a cassette 110 therein. First elongated member 122 combines with first bottom edge 140 and top panel 120 to form first U-shaped member 150. Second elongated member 124 combines with second bottom edge 142 and top panel 120 to form second U-shaped member 152. Third elongated member 126 combines with third bottom edge 134 and top panel 120 to form third U-shaped member 154. First extended corner end 160 of first elongated member 122 is adjacent to first open corner end 162 of second elongated member 124, and define first open corner 170. Third extended corner end 164 of third elongated member 126 is adjacent to second open corner end 166 of second elongated member 124, and define second open corner 172. First open corner 170 and second open corner 172 are formed by removing or eliminating a corner from rectangular portion or top portion 120 or shaping anti-scatter grid structure 100. Likewise third open corner 174 and fourth open corner 176 are formed by removing or eliminating a corner from rectangular portion or top portion 120 or shaping anti-scatter grid structure 100. Thus, X-ray cassette 110 has all four corners exposed when in either one piece anti-scatter grid structure 100 or two piece anti-scatter grid structure 200. Referring now to FIG. 4, FIG. 5, and FIG. 6, a two piece X-ray grid structure 200 embodies important features of a second embodiment of this invention. The one piece X-ray grid structure 100 is particularly constructed for assembly with an X-ray cassette 110. The two piece X-ray grid structure 200 includes a top solid panel 220 and is also compatible with X-ray cassette 110 and the like. This top solid panel 220 has a first flange member 222, a second flange member 224, and a third flange member 226 each extending from an edge of top solid panel 220 to protectively encase the X-ray cassette 110 against impact forces, which may be applied to the two-piece grid 220 in a circumstance where the two-piece structure 200 might be dropped or given rough handling by an X-ray technician when being removed from storage or placed into storage. As an option, vinyl cover 180 may be applied to either top panel 120 of one piece X-ray grid structure 100 or to top solid panel 220 of two piece X-ray grid structure 200. Vinyl cover 180 provides protection for either grid structure. Color coding of the vinyl cover 180 can be used as a filing mechanism too. Vinyl cover 180 is attached by bonding, gluing or either suitable fashion. More particularly, first flange member 222 extends from first solid edge 230 of top solid panel 220. In a like fashion, second flange member 224 extends from second solid edge 232 of top solid panel 220. Similarly, third flange member 226 extends from third solid edge 234 of top solid panel 220. The two-piece grid structure 200 protectively encases the X-ray cassette 110 against impact forces, which may be applied to the top solid panel 220 in a circumstance of dropping or given rough handling by an X-ray technician when being removed from storage or placed into storage. Cooperating with top solid panel 220 is bottom open panel 240. Bottom open panel 240 has an open top section 242. Open top section 242 has a first open edge 244, a second open edge 246, a third open edge 248, and a fourth open edge 250, framing opening 252 of open top section 242. Opening 252 cooperates with top solid panel 220 to frame X-ray cassette 110. First extension 260 extends from first open edge 244. Second extension 262 extends from second open edge 246. Third extension 264 extends from third open edge 248. Fourth extension 266 extends from a fourth open edge 250. First corner snap 270 is positioned on open top section 242 between first extension 260 and second extension 262. Second corner snap 272 is positioned on open top section 242 between third extension 264 and second extension 262. Third corner snap 274 is positioned on open top section 242 between third extension 264 and fourth extension 266. Fourth corner snap 276 is positioned on open top section 242 between fourth extension 266 and first extension 260. First corner snap 270 snap fits between first flange member 222 and second flange member 224. Second corner snap 272 snap fits between second flange member 224 and a third flange member 226. Third corner snap 274 snap fits between third flange member 226 and fourth flange member 228. Fourth corner snap 276 snap fits between first flange member 222 and a fourth flange member 228. Of course, releasable adhesive is preferred over the snap arrangement. X-ray grid 110 appears in opening 250 as x-ray grid structure 100 is positioned between top solid panel 220 and bottom open panel 240 to protectively encase the X-ray cassette 110 against impact forces. An open corner structure results therefrom. The preferred material used to form the one piece X-ray grid structure 100 or two piece X-ray grid structure 200 is required to have both shatter proof characteristics, as well as impact resistant capability. Such a material is the material of choice because of its desirable qualities. The preferred material used to form the one piece X-ray grid structure 100 or the two piece X-ray grid structure 200 is bendable aluminum. Sheets of aluminum, which are strong enough to offer protection, but remain bendable provide for the ease of manufacture. In FIG. 7, the two piece X-ray grid structure 200 has a releasable adhesive 280 on lapping edges of top solid panel 220 and bottom open panel 240 when they are assembled into two piece X-ray grid structure 200. The releasable adhesive 280 provides holding power. This application--taken as a whole with the specification, claims, abstract, and drawings--provides sufficient information for a person having ordinary skill in the art to practice the invention disclosed and claimed herein. Any measures necessary to practice this invention are well within the skill of a person having ordinary skill in this art after that person has made a careful study of this disclosure. Because of this disclosure and solely because of this disclosure, modification of this method and apparatus can become clear to a person having ordinary skill in this particular art. Such modifications are clearly covered by this disclosure. |
abstract | An inspection system for inspecting a core shroud includes a remotely operated vehicle with a profile, scanning ability, and reliability that contribute to expanded inspection coverage and reduced inspection times. |
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053032764 | summary | CROSS REFERENCE TO RELATED APPLICATIONS This patent application is related to copending U.S. patent application Ser. No. 07/884,972 titled "A Nuclear Fuel Assembly For Increasing Utilization Of Nuclear Fuel Contained Therein" filed May 15, 1992 in the name of David R. Stucker and copending U.S. patent application Ser. No. 07/968,011 titled "Method of Making A Fuel Assembly Lattice Member And The Lattice Member Made By Such Method" filed Oct. 29, 1992 in the name of Edmund E. DeMario et al. BACKGROUND This invention generally relates to fuel assemblies and more particularly relates to a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly, which fuel assembly may be of the kind typically found in nuclear power reactor cores. Before discussing the state of the art, it is instructive first to briefly describe the structure and operation of a typical nuclear power reactor, which contains a plurality of nuclear fuel assemblies. In this regard, a nuclear power reactor is a device for producing heat by the controlled fission of nuclear fuel material contained in a plurality of adjacent fuel rods. The fuel rods are bundled together by a plurality of spaced-apart grids, each grid having open cells for receiving each fuel rod therethrough and for obtaining a predetermined distance (i.e., pitch) between the adjacent fuel rods. Moreover, hollow control rod guide thimble tubes are also received through other open cells of each grid. The thimble tubes slidably accept movable absorber or control rods capable of controlling the fission process. A first end portion and a second end portion of each thimble tube are attached to a top nozzle and a bottom nozzle, respectively, for providing rigid structural support to the fuel assembly. The combination of the fuel rods, guide thimble tubes, grids, top nozzle and bottom nozzle is typically referred to in the art as a fuel assembly. A plurality of these fuel assemblies are grouped to define a nuclear reactor pressure vessel. During operation of the nuclear reactor, a flow stream of liquid moderator coolant (e.g., demineralized water) is caused to flow through the pressure vessel and over the fuel rods for assisting the fission process and for removing the heat produced by fission of the nuclear fuel material contained in each fuel rod. The flow velocity of the coolant, which is pumped over the fuel rods by reactor coolant pumps, may be approximately 18 feet per second, in the case of the typical pressurized water nuclear power reactor, for efficiently removing the heat produced by the fission process. That is, heat due to fission of the nuclear material is transferred from each of the fuel rods, and hence from each fuel assembly, to the liquid moderator coolant flowing past the fuel rods. The heat transferred to the liquid moderator coolant is ultimately carried by the coolant from the pressure vessel to a turbine-generator for generating electricity in a manner well known in the art of electrical power generation. As discussed hereinbelow, it is important for safety reasons that the coolant efficiently removes the heat produced by each fuel rod. For this purpose, the heated surface of each fuel rod should be in contact with the coolant which has a predetermined average bulk coolant temperature. It is known that the heat flux (i.e., rate of heat transfer per unit area) transversely across the heated surface of the fuel rod will vary as a function of the temperature difference between the heated surface of the fuel rod and the bulk coolant. In order to appreciate the importance of this relationship between heat flux and temperature difference, the discussion immediately hereinbelow provides a description of the manner in which the heat flux varies as a function of the temperature difference between the heated surface of the fuel rod and the bulk coolant. That is, as the difference between the surface temperature of the fuel rod and the bulk coolant is allowed to increase during start-up of the reactor, heat will be transferred from the heated surface to the coolant by single-phase convection, thereby increasing the heat flux. As the difference between the fuel rod surface temperature and the average bulk coolant temperature further increases, the temperature of the heated surface will eventually exceed the saturation temperature (i.e., temperature of saturated steam at the existing pressure in the reactor core) and vapor bubbles will form on the heated surface to produce nucleate boiling on the heated surface in a manner that rapidly increases the heat flux. A maximum heat flux will then occur when the bubbles become dense enough that they coalesce and form a vapor film on the heated surface. However, the vapor film will act as a heat insulator because vapor inhibits heat transfer. This point of maximum heat flux where the vapor film forms on the heated surface is commonly referred to in the art as Departure from Nucleate Boiling (DNB) and is to be avoided for safety reasons. Thus, if the difference between the surface temperature and the bulk temperature is allowed to further increase by even a small amount beyond the maximum heat flux (DNB), the heat flux will rapidly substantially decrease even though the temperature of the heated surface increases. The vapor film on the fuel rod at this point becomes unstable in the sense that the vapor film alternately breaks-down and then reforms so as to produce partial film boiling. If the difference between the surface temperature and the bulk coolant temperature is allowed to increase still further, the heat flux will again increase and stable vapor film boiling will occur. However, if large heat fluxes occur simultaneously with film boiling (i.e., either partial or stable film boiling), the temperature of the heated surface of the fuel rod may become high enough to damage the fuel rod (referred to in the are as "burnout") and is to be avoided for safety reasons. Thus, it is well understood by persons having ordinary skill in the art that if the reactor is operated such that nucleate boiling occurs near DNB, a relatively small increase in the heat flux will cause a relatively rapid change to film boiling that may result in "burnout". Therefore, it is prudent to operate the nuclear reactor such that the highest heat flux is less than the maximum heat flux associated with DNB in order to obtain the highest allowable heat generation without risking damage to the fuel rod. As discussed hereinabove, a vapor bubble film may form on the heated surface of the fuel rod to produce boiling thereon; however, the vapor film will act as a heat insulator because vapor inhibits heat transfer and may lead to DNB that may in turn lead to fuel rod damage. Hence, it is desirable to maintain a film of liquid substantially single-phase coolant on the surface of the fuel rod to enhance heat transfer from the fuel rod to the coolant while avoiding DNB. Therefore, a problem in the art is to maintain a film of liquid substantially single-phase coolant on the surface of the fuel rod to enhance heat transfer from the fuel rod to the coolant while avoiding DNB. Enhancing heat transfer from the fuel rod to the coolant while avoiding DNB increases the maximum allowable heat flux obtainable from a given reactor core size. This is desirable because increasing the maximum allowable heat flux obtainable from a given reactor core size increases the maximum allowable power obtainable from the reactor core. In this regard, heat transfer from the fuel rod to the coolant may be enhanced by increasing the bulk coolant flow velocity over the fuel rods. However, increasing the flow velocity of the coolant may require larger and more costly reactor coolant pumps. Therefore, another problem in the art is to more efficiently enhance heat transfer from the fuel rod to the coolant without requiring larger and more costly reactor coolant pumps. Maintaining a film of liquid substantially single-phase coolant on the surface of the fuel rod to enhance heat transfer from the fuel rod to the coolant while avoiding DNB in a manner not requiring larger coolant pumps has assumed added importance in recent years because some current reactor core designs require the previously mentioned fuel rods to be arranged in a denser triangular pitch array rather than in the more traditional and less dense square pitch array. Thus, in some reactor core designs, the fuel assemblies containing the fuel rods may have a hexagonal transverse cross-section for suitably achieving the "dense-pack" triangular pitch array. Fuel rods arranged in a triangular pitch array obtain a higher average heat flux density from a reactor core of given size compared to fuel rods arranged in the more traditional square pitch array. Obtaining a higher average heat flux density using densely packed fuel assemblies is desirable for economic reasons because such densely packed fuel assemblies achieve more revenue-producing power per unit volume of the reactor core which in turn increases return on plant investment. However, higher heat flux tends to increase the risk of DNB and is therefore undesirable for safety reasons, as discussed hereinabove. Thus, it has become very important to adequately cool such fuel assemblies and the densely packed fuel rods contained therein such that DNB is avoided while simultaneously obtaining a higher heat flux per unit volume of the reactor core. Fuel assemblies suitable for use in nuclear reactor cores are known. One such fuel assembly is disclosed in U.S. Pat. No. 3,787,285 titled "Fuel Assembly For A Nuclear Reactor And A Nuclear Reactor Core Comprising Such Fuel Assemblies" issued Jan. 22, 1974 in the name of Jorgen Marstrand. This patent discloses a fuel assembly having guide vanes, the axes of which are parallel to the fuel rods and impart a vortical motion to the coolant flowing along the vanes to permit higher energy flux density. The fuel rods are arranged in a hexagonal pattern such that the outer contour of the fuel assembly is hexagonal. A plurality of vanes are disposed about, and tilted with respect to, a central axis to cause the fluid flow over the fuel elements to follow a generally helical path about the central axis. Although the Marstrand patent discloses a fuel assembly having an outer hexagonal contour and a plurality of guide vanes, the Marstrand patent does not appear to disclose a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly, as described and claimed hereinbelow. Another fuel assembly is disclosed in U.S. Pat. No. 3,281,327 titled "Nuclear Fuel Assemblies" issued Oct. 25, 1966 in the name of John Webb, et al. This patent discloses a spacer grid comprising a support member in the form of an outer metal sleeve of regular hexagonal cross-section. This patent also discloses that the grid has a parallel array of spacer diaphragms adapted to be penetrated by fuel elements and titled with respect to the longitudinal axis of the fuel element. According to this patent, the spacer diaphragms act as deflector vanes imparting to the main flowstream a component of flow transversely of the fuel elements. According to the Webb, et al. patent the diaphragms are advantageous from a heat transfer standpoint because they promote swirling of the coolant to reduce so-called "hot channel factors". Although the Webb, et al. patent discloses a fuel assembly having a parallel array of spacer diaphragms that promote swirling of the coolant to improve heat transfer, the Webb et al. patent does not appear to disclose a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly, as described and claimed hereinbelow. Although the above recited patents disclose fuel assemblies suitable for use in nuclear reactor cores, these patents do not appear to disclose a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly, as described and claimed hereinbelow. Therefore, what is needed is a fuel assembly including deflector vanes for suitably deflecting a component of a fluid stream flowing past such fuel assembly. SUMMARY Disclosed herein is a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly. The fuel assembly comprises a lattice member having rhombic-shaped rod cells and generally rhombic-shaped thimble cells therethrough. A plurality of parallel fuel rods extend through respective ones of the rod cells and a plurality of parallel control rod guide thimble tubes extend through respective ones of the thimble cells. A plurality of deflector vanes are associated with each rod cell and are integrally attached thereto on the upstream edge of each rod cell. Each deflector vane extends above its associated rod cell and curvilinearly protrudes partially over the rod cell for deflecting a component of the fluid stream onto the exterior surface of the fuel rod that extends through the rod cell. The deflector vane and the rhombic shape of each rod cell coact to create a vortex centered about the longitudinal axis of the fuel rod for maintaining liquid substantially single-phase fluid flow along the exterior surface of the fuel rod, such that DNB is avoided even in the presence of high heat fluxes across the exterior surface of the fuel rod. An object of the present invention is to provide a fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly. Another object of the present invention is to provide a fuel assembly containing fuel rods, on the outside surface of which is maintained a film of liquid substantially single-phase coolant to enhance heat transfer from the fuel rod to the coolant to avoid DNB. Yet another object of the present invention is to provide a fuel assembly that efficiently enhances heat transfer from the fuel rod to the coolant without requiring larger and more costly reactor coolant pumps to increase fluid flow velocity. A feature of the present invention is the provision of a lattice member defining a plurality of rhombic-shaped rod cells for receiving fuel rods therethrough and deflector vanes protruding above and partially over each rod cell, the rhombic-shape of the rod cells coacting with the deflector vanes to swirl the coolant about the longitudinal axis of each fuel rod. An advantage of the present invention is that it obtains a reactor core that produces more revenue-producing power while simultaneously avoiding damage to the fuel rods therein. Another advantage of the present invention is that it obtains liquid substantially single-phase coolant flow over the surface of each fuel rod even in the presence of high heat fluxes so that the fuel rods are not damaged during normal reactor operation. These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention. |
description | This disclosure relates generally to an apparatus, system and method for controlling the output of a particle accelerator used in radiation testing. In particular, this disclosure relates to a beam diffuser selector apparatus and system for a particle accelerator used in radiation testing and a method of use of that beam diffuser selector apparatus. Radiation testing is an important part of product testing that is required for devices that will be used in high-radiation environments. These high-radiation environments may include, for example, outer space and high-altitude flight areas, regions around nuclear reactors and particle accelerators, etc. Particle accelerators are typically used to perform radiation testing. A radiation test customers may request thousands of radiation exposures across dozens of different radiation environments for each device under test. The particle accelerator is usually set to provide a fixed known output and the actual radiation environment provided is controlled by attenuating that output by inserting a beam diffuser in front of the output of the particle accelerator. There are two other ways to control the output of a particle accelerator, by adjusting the tuning of the particle accelerator (commonly referred to as the “accelerator's tune”) and by changing the distance between the output of the particle accelerator and the device under test. However, the accurate adjustment to a new output level of the particle accelerator output may require several hours of time. This type of beam output adjustment is not practical for testing involving a number of different type of tests. Furthermore, certain testing may require radiation at levels ranging over several orders of magnitude which requires a test cell having a test track (for a movable platform to hold the device under test) which is longer than practical (e.g., on the order of one thousand feet or so). The beam diffuser used on the output of the particle accelerator is typically a metallic (e.g., aluminum or tantalum) plate of a predetermined thickness affixed directly over the output. By using a number of different plates, each having a different predetermined thickness, various different radiation environments can be provided. However, the time required to change the configuration between radiation environments can be significant, requiring several minutes for an operator to turn the particle accelerator to an off-state, break the safety interlocks on the test cell door, enter the test cell, manually replace the plate on the front end of the accelerator, reset the safety interlocks on the test cell door, exit the test cell, and turn the particle accelerator back to an on-state. The use of beam diffusers is more practical than adjusting the particle accelerator output or by changing the position of the device under test, but still can add a significant amount of time for the complete test procedure due to the time required for each plate change. Accordingly, there is a need for an apparatus and method which overcomes the problems recited above. In a first aspect a beam diffuser selector apparatus for a particle accelerator includes a movable member having a plurality of beam diffusers mounted thereon. Each of the plurality of beam diffusers has a different predetermined thickness. The beam diffuser selector apparatus also includes a driving device coupled to the movable member. The driving device is configured to selectively move the movable member such that a selected one of the plurality of beam diffusers is positioned in a test position which is adjacent to an output of the particle accelerator and between the output of the particle accelerator and a device under test. In a further embodiment, the movable member has at least one diagnostic tool mounted thereon and the driving device is configured to selectively move the movable member such that a selected one of the plurality of beam diffusers or a selected one of the at least one diagnostic tool is positioned in the test position. The diagnostic tools may be one or more of a laser apparatus, a phosphor screen, and a radiochromatic film. The movable member may have a partial ring member coupled to a hub member via a plurality of spoke members. The movable member may have a counterweight coupled to the hub member via an additional spoke member. The counterweight may be positioned opposite the partial ring member. The driving device may have a motor that drives a shaft that is connected to the movable member. The motor may be a stepper motor and the driving device may include a resolver coupled to the shaft to provide feedback about a position of the movable member. A controller is coupled to the stepper motor and the resolver. The controller is configured to cause the stepper motor to rotate to position a selected one of the plurality of beam diffusers in the test position. The driving device may be mounted on a moveable platform. A retraction device may be provided that has a pneumatic cylinder coupled to the moveable platform that selectively retracts the movable member away from the output of the particle accelerator. In a second aspect, a beam diffuser selector system for a particle accelerator has a movable member that has a plurality of beam diffusers mounted thereon. Each of the plurality of beam diffusers has a different predetermined thickness. The beam diffuser selector system also has a driving device coupled to the movable member. The driving device is configured to selectively move the movable member such that a selected one of the plurality of beam diffusers is positioned in a test position which is adjacent to an output of the particle accelerator and between the output of the particle accelerator and a device under test. The beam diffuser selector system further has a controller coupled to the driving device. The controller having a user interface for receiving commands selecting a particular one of the plurality of beam diffusers and configured to provide control signals to the driving device to cause the driving device to selectively move the movable member such that the selected one of the plurality of beam diffusers is positioned in the test position. In a further aspect, the movable member has at least one diagnostic tool mounted thereon. The driving device is configured to selectively move the movable member such that a selected one of the at least one beam diffuser or a selected one of the at least one diagnostic tool is positioned in the test position. The user interface is for receiving commands selecting a particular one of the plurality of beam diffusers or of the at least one diagnostic tool. The controller is configured to provide control signals to the driving device to cause the driving device to selectively move the movable member such that the selected particular one of the plurality of beam diffusers or of the at least one diagnostic tool is positioned in the test position. In a third aspect, a method of operating a beam diffuser selector apparatus for a particle accelerator is described. The beam diffuser selector apparatus includes a movable member having a plurality of beam diffusers mounted thereon. Each of the plurality of beam diffusers has a different predetermined thickness. The beam diffuser selector apparatus also includes a driving device coupled to the movable member. According to the method, one of the plurality of beam diffusers is selected for use in a test. Then, the driving device is caused to move the movable member such that the selected one of the plurality of beam diffusers is positioned in a test position which is adjacent to an output of the particle accelerator and between the output of the particle accelerator and a device under test. In a further embodiment, the movable member may be retracted away from the output of the particle accelerator once the test is complete. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings. In the present disclosure, like reference numbers refer to like elements throughout the drawings, which illustrate various exemplary embodiments of the present disclosure. Referring now to FIG. 1, a beam diffuser selector apparatus 100 is shown which provides a number of advantages when used with a particle accelerator to perform radiation testing. In particular, beam diffuser selector apparatus 100 both increases the capabilities of the associated particle accelerator (e.g., by allowing the selection of a different types of beam diffusers and also diagnostic tools) and increases the number of radiation exposures within the same time frame because the selection of different beam diffusers or diagnostic tools is done remotely. Since a change of beam diffusers or diagnostic tools is performed via a remote interface (discussed below), there is no need to turn the particle accelerator to an off-state, break the safety interlocks on the test cell door, enter the test cell, manually replace the plate on the front end of the accelerator, reset the safety interlocks on the test cell door, exit the test cell, and turn the particle accelerator back to an on-state as previously required. This provides a very significant time-savings when performing device testing at different radiation levels, for example, greatly reducing the downtime of the particle accelerator and providing the ability to test many more devices in a given timeframe. Furthermore, the ability to select diagnostic tools as well as beam diffusers allow an operator to verify and adjust certain particle accelerator performance characteristics (e.g., particle beam shape, position, and alignment with the device under test). Beam diffuser selector apparatus 100 includes a movable member 110 having a plurality of beam diffusers 111 mounted thereon. Each of the plurality of beam diffusers 111 has a different predetermined thickness such that a plurality of different radiation levels may be provided to a device under test depending on which beam diffuser is selected. A driving device 120 is coupled to the movable member 110. Driving device 120 selectively moves the movable member 110 so that a selected one of the plurality of beam diffusers 111 is positioned in a test position which is adjacent to an output of the particle accelerator and between the output of the particle accelerator and a device under test (as shown in FIG. 2). The beam diffusers 111 may be formed from aluminum with different thicknesses (e.g., ranging from ⅛″ to 2″). In addition, one of the beam diffusers 111 may be formed from tantalum to allow bremsstrahlung conversion (i.e., to convert the particle accelerator output into x-rays). The movable member 110 may also have diagnostic tools 112, 113, 114 mounted thereon. Diagnostic tool 112 is a laser apparatus used for alignment of the device under test. Diagnostic tool 113 is a phosphor screen used to identify the beam shape exiting the output of the particle accelerator. Diagnostic tool 114 is a radiochromatic film that is used to see beam alignment relative to the output of the of particle accelerator. Other diagnostic tools may be included as known in the art, for example a faraday cup for use in determining beam spectrum. When diagnostic tools are included on movable member 110, the driving device 120 selectively moves movable member 110 such that a selected one of the plurality of beam diffusers 111 or a selected one of the diagnostic tools 112, 113, 114 is positioned in the test position. Preferably, movable member 110 is formed with a partial ring member 115 that is coupled to a hub member 119 via a plurality of spoke members 116 although other formations may be used for movable member 110. Depending on the number of beam diffusers 111 and diagnostic tools 112, 113, 114 included on partial ring member 115, a counterweight 118 may be included that is coupled to the hub member 119 via an additional spoke member 117, with counterweight 118 positioned opposite the partial ring member 115 to provide balance to movable member 110. Beam diffuser selector apparatus 100 also includes a driving device 120. Driving device 120 has a motor 122 that drives a shaft 121 that is connected to the hub member 119 of the movable member 110. The motor 122 is preferably a stepper motor to ensure that movable member 110 is accurately and repeatably positioned with respect to the output of the particle accelerator. In addition, driving device 120 also includes a resolver 123 which is coupled to shaft 121 via a one-to-one pulley system 124 to provide feedback about the current position of the movable member 110 with respect, for example, to the output of the particle accelerator to enable more accurate positioning of movable member 110, e.g., preventing any overshoot of rotation. Shaft 121 also passes through a plate 127. Rotational limit switches 125 and 126 may be mounted on plate 127 adjacent to shaft 121 for calibration and protection purposes. Beam diffuser selector apparatus 100 may further include a movable platform 130. Driving device 120 is mounted on a track mechanism 135 that is secured to movable platform 130. A retraction device 134 is also provided on movable platform 130 which includes a pneumatic cylinder 133 having a first end coupled to the movable platform 130 and a second end coupled to the driving device 120. Retraction device 134 is selectively operated (e.g., via a switch or an external controller) to retract (when movable member 110 is in an extended position) or to extend (when movable member 110 is in a retracted position) movable member 110 away from or towards the output of the particle accelerator. Horizontal limit switches (not shown) may be included that are used to determine whether the movable member 110 is in the extended position or retracted position. The controller may use this positional information to ensure that no rotational motion of movable member 110 is allowed when movable member is in the retracted position. Referring now to FIG. 2, beam diffuser selector apparatus 100 is shown mounted on top of a particle accelerator 200, with movable member 110 positioned in the extended position. When movable member 110 is in the extended position, rotation thereof causes one of the beam diffusers 111 (or one of the diagnostic tools 112, 113, 114) is positioned adjacent to the output 210 of the particle accelerator 200. During use (i.e., testing of a device under test 230), particle accelerator 200 outputs a beam 220 that passes through one of the beam diffusers 111 (or one of the diagnostic tools 113, 114—diagnostic tool 112 is not used during operation of the particle accelerator) and then strikes a device under test 230. To the extent that additional testing is required at a different level of radiation, an operator may simply cause the associated controller (i.e., controller 420 discussed below with respect to FIG. 4) to operate driving device to rotate movable member 110 to position another of the beam diffusers 111 (which is known to provide the desired level of radiation) at the output 210 of the particle accelerator 200. Referring now to FIG. 3, beam diffuser selector apparatus 100 is shown mounted on top of a particle accelerator 200, with movable member 110 positioned in the retracted position. In this position, movable member 110 is moved away from the output 210 of particle accelerator 200 such that a beam 320 passes directly to a device under test 330. Referring back to FIG. 1, movable platform 130 may be formed of two parallel plates 131, 132, with plate 131 over plate 132, which are coupled in a manner that allows plate 131 to be rotated (and thus rotating driving device 120 and movable member 110) with respect to the position of plate 132 (which is secured to an upper surface of the particle accelerator). The ability to rotate plate 131 allows beam diffuser selector apparatus 100 to be used with particle accelerators having angled exit ports (outputs). Referring now to FIG. 4, beam diffuser selector system 400 includes a movable member 110 having a plurality of beam diffusers 111 (shown in FIG. 1) mounted thereon, each of the plurality of beam diffusers 111 having a different predetermined thickness. Beam diffuser selector system 400 also includes a driving device 120 coupled to the movable member 110 via a shaft 121. As described with respect to FIG. 1, driving device 120 selectively moves movable member 110 such that a selected one of the plurality of beam diffusers 111 (or diagnostic tools 112, 113, 114 shown in FIG. 1) is positioned in a test position which is adjacent to an output of the particle accelerator and between the output of the particle accelerator and a device under test 440. Beam diffuser selector system 400 further includes a controller 420 coupled to the driving device 120 by a connection 410. Controller 420 has a user interface 425 for receiving commands from a user selecting a particular one of the plurality of beam diffusers 111 (or diagnostic tools 112, 113, 114). Controller 420 provides control signals to the driving device 120 to cause the driving device 120 to move movable member 110 such that the selected one of the plurality of beam diffusers 111 (or diagnostic tools 112, 113, 114) is positioned in the test position between the output 210 of the particle accelerator 200 and the device under test 440. The particle accelerator 200 outputs a beam 450 that strikes the device under test 440. Preferably, controller 420 receives feedback signals from resolver 123 and from rotational limit switches 125, 126 which are used to ensure that movable member 110 is accurately positioned at the selected position. As described above, when the beam diffuser selector apparatus 100 and particle accelerator 200 are positioned within a test chamber 430 and the controller 420 is positioned outside the test chamber 430, a test procedure requiring that a device under test 440 be tested at various levels of radiation is performed much more quickly because a test operator will not need to enter the test chamber to change from one beam diffuser to another, a very time consuming process. Instead, the test operator need only enter information onto user interface 425 causing controller 420 to provide signals to driving device 120 that results in movable member rotating to a new position for the newly selected beam diffuser 111. This time savings allows many more tests to be performed within a given timeframe, a great benefit given the cost of a particle accelerator because of the limited downtime. Referring now to FIG. 5, a flowchart 500 is provided for a method of operating the beam diffuser selector apparatus 100 for a particle accelerator 200. As shown in FIG. 1, beam diffuser selector apparatus 100 includes a movable member 110 having a plurality of beam diffusers 111 mounted thereon. Each of the plurality of beam diffusers 111 has a different predetermined thickness. Beam diffuser selector apparatus 100 also includes a driving device 120 coupled to the movable member 110. First, at step 510, one of the plurality of beam diffusers 111 is selected for use in a test. Next, at step 520, the driving device 120 is caused to move the movable member such that the selected one of the plurality of beam diffusers 111 is positioned in a test position which is adjacent to an output 210 of the particle accelerator 200 and between the output 210 of the particle accelerator 200 and a device under test 230. Finally, at step 530 the movable member 110 may optionally be retracted away from the output of the particle accelerator once the test is complete. Although the present disclosure has been particularly shown and described with reference to the preferred embodiments and various aspects thereof, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure. It is intended that the appended claims be interpreted as including the embodiments described herein, the alternatives mentioned above, and all equivalents thereto. |
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description | 1. Field of the Invention The present invention relates to systems and methods used in radiation imaging; and more particularly, to collimators utilized in cooperation with radiation detectors that permit only desired radiation to strike the detector thereby producing a more accurate image-of-interest, typically of an internal portion of a patient when medical and diagnostic applications are considered. 2. Description of the Background Art In conventional radiation imaging arrangements, collimators are used in a wide variety of equipment in which it is desired to permit only beams of radiation emanating along a particular path to pass a selected point or plane. Collimators are frequently used in radiation imagers to ensure that only radiation beams passing along a direct path from the known radiation source strike the detector thereby minimizing detection of beams of scattered or secondary radiation. Particularly in radiation imagers used for medical diagnostic analysis or for non-destructive evaluation procedures, it is important that only radiation emanating from a known source and passing along a direct path from that source be detected and processed by the imaging equipment. If the detector is struck by undesired radiation such as that passing along non-direct paths to the detector, performance of the imaging system can be degraded. Collimators are positioned to substantially absorb the undesired radiation before it reaches the detector. The collimator includes (or is manufactured from) a relatively high atomic number material and the collimator is positioned so that undesired radiation strikes the body of the collimator and is absorbed before being able to strike the detector. In a typical detector system the collimator includes barriers associated with the detector and located in the direction of the radiation source. An example exists in radiation imaging systems used for medical diagnosis which use a small point source of radiation to expose the patient under examination. The radiation passes through the patient and strikes a radiation detector that is oppositely positioned. Another diagnostic technology that incorporates collimators is the gamma camera typically utilized in Single Photon Emission Computed Tomography (SPECT) scanning, which is a nuclear medicine procedure in which gamma camera(s) have traditionally rotated around the patient taking pictures from many angles. From these images, a computer is employed to form a tomographic (cross-sectional) image of the internal area-of-interest within the patient using a calculation process that is similar to that used in X-ray Computed Tomography (CT) and in Positron Emission computed Tomography (PET). In the instance of SPECT scanning, a subject (patient) is infused with a radioactive substance that emits gamma rays. Conventionally, a gamma camera includes a transducer to receive the gamma rays and record an image therefrom. In order for the image to be a true representation of the subject being investigated, a collimator having collimating apertures is positioned between the transducer and the subject to screen out all of the gamma rays except those directed along a straight line through the collimating apertures between a particular part of the subject and a corresponding particular part of the transducer. Traditionally, the collimator is made of a radiation opaque material such as lead, and collimating apertures have been formed therein by various means such as drilling, casting, or lamination of corrugated strips of lead foil. In conventional SPECT system designs, the gamma cameras have been supported on gantries that rotate the camera heads through a specific angular range around the patient, usually covering one hundred eighty or three hundred and sixty degrees. One drawback associated with this requirement however, is that such gantry systems are relatively expensive subsystems of the diagnostic tool because they must be capable of providing rapid rotation is of the large and heavy camera heads through very precise orbits about the patient. As a result, the object of the present invention is to accommodate the use of lower cost, simplified gantries, without sacrificing image quality, or driving the cost of related subsystems higher. In an effort to remedy the deficiencies outlined above with respect to SPECT scanning, the present invention, at least in one aspect, is directed toward a method and arrangement for affecting collimation that allows the required angular views for SPECT scanning to be obtained using only one-dimensional relative linear motion between the camera and the patient. This type of operation is important because, among other reasons, the systems utilized in the ever increasingly popular whole body scanning technologies predominantly already utilize such relative linear motion between the scanning device and the patient, in addition to the camera's rotation. In fact, such whole body studies are a mainstay in clinical nuclear medicine and therefore their efficiency is of paramount importance. The present invention relies on a collimator in which the angle of view varies across the collimator. With this type of collimator, SPECT systems based on substantially complete angular sampling can be devised for single and multiple headed camera systems that require as few as a single pass of the camera along the patient, without relative rotation between the patient and camera, while also minimizing the length of the translational pass required of the camera. Important advantages will be seen in cost savings for the gantry, simplification of setup and operation, and for some configurations, significantly smaller space requirements for the incorporating systems. To this end, one embodiment of the invention takes the form of a system utilizing slant-angle collimation for SPECT radiation sampling. The system comprises (includes, but is not necessarily limited to) a collimator positioned between a radiating mass and a radiation detector. The collimator is spaced apart from a translational path of the radiating mass at a predetermined distance that defines a patient accommodation space. Apertures extend through the collimator and form passageways for gamma (radiation) rays emanating from the radiating mass to strike the radiation detector. In summary, the provision and utilization of collimators configured according to the teachings above facilitate enhanced radiological imaging quality, while at the same time simplifying and reducing the cost of the support structures required to carry the necessary instruments and which affect relative, longitudinal motion between those instruments and the patient. Among other benefits, the method and arrangement of the present invention permits the utilization of exclusively longitudinal relative motion between the patient and imaging instruments compared to the orbital motion about the patient which has been previously required when conducting such procedures as full body scanning. When considering full angular gamma camera sampling utilizing SPECT parallel projection views, or their equivalents, the image samples should be obtained over one hundred and eighty or three hundred and sixty degrees. According to the present invention, a system (10) is provided that includes a collimator (13) adapted with apertures (27) that serve as openings for slant-angle passageways (28) which accommodate views of a radiating area or object-of-interest (61), such as the heart of a patient (19), from a specific slant-angle. Referring to FIG. 1, the specific angle at which the slotted passageway (28) is canted within the collimator (13) is dependent on the relative position (x) of the passageway (28) in the collimator (13). In the instance of FIG. 1, the radiation source is the radiating mass (19) shown as the radioactively infused heart (19) of a patient. For each row of passageways (28) through the collimator (13), the associated collimated (gamma) rays travel along lines that establish planes perpendicular to a representative or central plane (16) of the collimator (13). From the top to the bottom of the collimator (assuming a vertical orientation of the collimator (13) as shown in FIG. 1), the slant-to-the-side-angle of the passageways (28) in each row can vary, with a preferential range of variability spanning between plus/minus forty-five degrees. As previously described, FIG. 1 illustrates one example of a system (10) for providing multi-angular SPECT sampling of gamma rays (radiation) emanating from at least a part of a patient using a collimator with side-slant-angles which vary from row-to-row up the face of the collimator (13). As shown, the collimator (13) is positioned between the radiation source (19) and a radiation detector (21). The collimator (13) is spaced apart from the path (25) of the radiation source (19) at a predetermined distance (24) that generally defines a patient accommodation space (26). The plurality of apertures extend through the collimator (13), and each forms a passageway (28) for radiation rays (20) emanating from the radiation source (19) and allows those rays (20) to strike the radiation detector (21). The passageways (28) are composed of a series of adjacent and parallel elongate apertures. Because the collimator (13) has a thickness, these passageways (28) are channel-like and each has a longitudinal axis (29) that is substantially aligned with the collimated radiation rays (20) that are permitted to pass through that particular channel (29). In order to effect a desired alignment between each channel (28) and respective rays (20) that must pass therethrough, the longitudinal axis (29) of the channels (28) is obliquely oriented with respect to a central plane (16) of the collimator (13). Collectively, the several figures depict several configurations and methods for implementing a system (10) for providing multi-angular SPECT radiation sampling utilizing slant-angle collimation according to the present invention. The system (10) comprises a collimator (13) positioned between a radiating mass (19) within a patient (60) and a radiation detector (21). The collimator (13) is spaced apart from a translational path (25) of the radiating mass (19) at a predefined distance (24) that defines a patient accommodation space (26). A plurality of apertures (27) extend through the collimator (13), and each forms a passageway (28) for radiation rays (20) emanating from the radiating mass (19) in a direction substantially aligned with a longitudinal axis (29) of the respective passageway (29) and in this manner enables the aligned radiation rays (20) to strike the radiation detector (21). The plurality of passageways (28) include a first group (30) of passageways adjacently aligned in a first row (32) and arranged so that the longitudinal axes (29) of the first group (30) of passageways (32) are substantially contained in a first plane (34) oriented substantially perpendicularly to a central plane (16) of the collimator (13). Each of the parallel longitudinal axes (29) of the first row (32) of passageways is obliquely oriented with respect to the central plane (16) of the collimator (13) with an included angle (36) therebetween. On this row (32), each of the included angles, when measured clockwise from the central plane (16) or face of the collimator (13) to a respective longitudinal axis, is an acute angle. As may be best appreciated in FIGS. 1-2c, the system (10) preferably further includes a second group (40) of passageways (28) adjacently aligned in a second row (42) and arranged so that the longitudinal axes (29) of the second group (40) of passageways (28) are substantially contained in a second plane (44) oriented substantially perpendicularly to a central plane (16) of the collimator (13). A second group (40) of passageways (28) are adjacently aligned in a second row (42) and arranged so that the longitudinal axes (29) of that group are substantially contained in a second plane (44) which is also oriented substantially perpendicularly to the central plane (16) of the collimator (13). The second row (42) of passageways is spaced apart from the first row of passageways at a predefined distance, L, which essentially defines the length or height of the collimator (13). Each of the parallel longitudinal axes (29) of the second row (42) of passageways (28) is obliquely oriented with respect to the central plane (16) of the collimator (13) with an included angle, each of which when measured clockwise from the central plane (16) of the collimator (13) to a respective longitudinal axis (29), is obtuse. As illustrated in FIGS. 1-4, a third row (52, 52b) of passageways (28) is also provided and which is spaced apart from the first row (32) of passageways (28) at a predefined distance (X). Each of the parallel longitudinal axes (29) of the third row (42) of passageways (28) is substantially perpendicularly oriented with respect to the central plane (16) of the collimator (13). As is illustrated in FIG. 3, however, there may be multiple additional rows (52a, 52b, 52c) of passageways (28), each of which is located at a different spacing distance from first row (32) of passageways (28). In this case, the side slant-angle of the passageways (28) of the row (52a, 52b, or 52c) is based on the predefined spacing distance (X) of the particular row (52a, 52b, or 52c) from the first row (32) of passageways (28). As before, the predefined distance between the extreme first row (32) of passageways (28) and the second row (42) of passageways (28) is defined by the effective collimator length (L). A difference between the measurement of the obtuse included angle (46) and the measurement of the acute included angle (36) define a sweep angle or range of angles of the passageways (28) of the different rows (32-52). In the embodiment of FIG. 3, regarding each interstitial row (52a, 52b, or 52c), the parallel longitudinal axes of that row (52a, 52b, or 52c) of passageways (28) is obliquely oriented with respect to the central plane (16) of the collimator (13) with an included angle therebetween. Each of the included angles, when measured clockwise from the central plane of the collimator to a respective longitudinal axis, is defined as a proportion of the sweep angle. Preferably, the proportion is defined by the distance, X, of the particular row (52a, 52b, or 52c) from the first row (32) of passageways (28) divided by the distance, L, of the first row (32) of passageways from the second row (42) of passageways (28). It should be appreciated that for purposes of clarity each of the several apertures (27) in any given row in the collimator (13) have been shown with a certain amount of space therebetween. In actuality, however, each row of passageways contains a sufficient number of passageways arranged close together to effectively form an elongate slot through the collimator along that row. As may be best appreciated in FIGS. 4a-4c, the obtuse 46) included angles (FIG. 4c) associated with the second row (42) of passageways (28) are approximately one hundred and thirty-five degrees as measured clockwise from the central plane (16) of the collimator (13) to a respective passageway's (28) longitudinal axis (29). The acute (36) included angles (FIG. 4a) associated with the first row (32) of passageways (28) are approximately forty-five degrees as measured clockwise from the central plane (16) of the collimator (13) to a respective passageway's (28) longitudinal axis (29). As may be best appreciated in FIGS. 4a-c, the predefined distance at which the collimator (13) is positioned from the translational path (25) of the radiating mass (19) is selected so that approximately one-half of a translating radiating mass (19) is multi-angularly, SPECT radiation sampled through the collimator (13) in a single translational pass of the radiating mass (19) relative to the radiation detector (21). As may be gleaned from FIG. 5, in a preferred embodiment the collimator (13) is mounted on an instrument support assembly and the instrument support assembly is associated with a motive means for affecting longitudinal relative motion between the instrument support assembly and a patient (60) for taking the multi-angular SPECT radiation sampling of the radiating mass (19) in the patient (60) utilizing the variously slant-angled passageways (28) and without requiring relative rotation between the patient (60) and the instrument support assembly. In a preferred embodiment, the collimator (13) and the detector (21) are each mounted on an instrument support assembly in fixed orientation with one another. The instrument support assembly is associated with a motive means for affecting longitudinal relative motion between the instrument support assembly and a patient (60) for obtaining the necessary slant-angular sampling of an area-of-interest (61) in the patient without requiring relative rotation between the patient and instrument support assembly. From the image data obtain for each longitudinal scan position, projection sinograms can be formed for each slice of the object. From the sinograms transverse tomographic slices of the object can be reconstructed. As illustrated in FIGS. 5-7, a preferred utilization of such a collimator (13) is depicted as a component in a gamma camera (66, 72). The camera arrangement (66, 72) then moves along the length of the patient (60). Alternatively, the patient (60) may be moved with respect to one or more of the stationary cameras (66, 72). From this, projection views of transverse slices of the patient (60) are sensed for each row of passageways (28) at slant angles that sweep across the angular range of the collimator (i.e., plus/minus forty-five degrees). As a result, multi-angular sampling is facilitated without camera rotation about the patient. These varied angular views, with appropriate scaling, can be used for the reconstruction of three-dimensional SPECT images of the scanned patient region (organ) (61) in question. For full angular sampling, SPECT can be implemented using two heads (66, 72) as illustrated in FIGS. 5 and 6. Alternatively, a single head (66) and two or more linear scans over the area-of-interest (61) in the patient (organ) (60) can be made as depicted in FIG. 7, and where for each scan there is a specified fixed tilt angle of the camera head (66). The illustrated implementation is as a cardiac SPECT camera. Because the cameras (66, 72) move up and down lengthwise along the patient (60), or alternatively, the patient (60) rises up and down relative to the cameras (66, 72), a relatively small equipment footprint is required and thereby constitutes a space-saving diagnostic instrument. In the examples, two rectangular cameras (66, 72), each have a plus/minus forty-five degree varying slant collimator, are fixedly mounted, orthogonally and staggered with respect to one another. Using the example of FIG. 5, in order to obtain comprehensive views of the heart or other area-of-interest (61) in the patient (60), that part (61) of the patient (60) is initially located so that an upper portion of the heart (61) is at the lower edge of the field-of-view for the lower camera (66). The patient (60) can then be moved upward until the bottom of the heart (61) is positioned above the upper edge of the field-of-view for the upper camera (72). With this linear scan, angular, projection views for each cross-section of the heart are obtained (61) covering approximately one hundred and eighty degrees (or one-half) from each camera and which allows substantially full, high-quality SPECT reconstruction. Referring to FIG. 5 in which the patient (60) is moved relative to the cameras (66, 72) in the direction indicated by arrow 64, the institution of such motion requires, for example, a vertically driven platform. In an arrangement of this nature, it has been found to be useful for keeping the patient immobile and stable to affix two thin, rigid vertical walls to the platform. The chest of the patient is then snugly pressed and secured against the walls with, for example, tape or straps, if necessary. Preferably, these walls are constructed of low attenuation material for gamma rays. As a further enhancement, it is contemplated that the walls can be adapted with a window over the heart region thereby more completely avoiding interference caused by the walls' presence. In this example, faces of the cameras (66, 72) glide over outer surfaces of the walls as the platform is raised. Thus, during the entire scan, the heart (61) will be very close to the detectors (21) of the gamma cameras (66, 72), which is beneficial for achieving good spatial resolution. In a preferred embodiment, a system (10) of this configuration can be sized to fit within a floor space of three feet by three feet. FIG. 6 shows a non-rotating, dual-head, whole body SPECT system having two camera heads that are again orthogonally fix-mounted as depicted in FIG. 5. The cameras (66, 72) and/or patient bed (63) are capable of moving in a horizontal straight line for whole body scanning. As shown, the patient (60) is lying on a pallet with one camera (66) facing or aimed at the front of the patient (60) and the other camera (72) facing the patient's side. Linear scan motion from the patient's head to feet provides the necessary angular views for complete whole body SPECT reconstruction. In this configuration, the perpendicular cross-sectional projections produce orthogonal views (e.g. anterior and lateral). Because conjugate views, which differ by one hundred and eighty degrees, generally have significant differences due to attenuation, it can be desirable to make a second scan pass of the patient. The present invention also contemplates utilization of a single head camera (66) that can be tilted about pivot point 69 and has linear whole body scan capability to perform transaxial SPECT. This is depicted in FIG. 7 where a two-pass linear scan is used. The camera head (66) has a plus/minus forty-five degree varying slant angle collimator. During the first linear scan pass, the camera (66) has a fixed tilt angle, shown as zero degrees, downward. In this configuration, the collimator (13) and radiation detector (21) are incorporated components in a first gamma camera (66) that is aimed at the patient accommodation space (26). As described before, the first camera (66) is mounted on an instrument support assembly configured for longitudinal relative motion with respect to the patient accommodation space (26) for developing a first one pass, cross-angled radiation sampling of the area-of-interest (61) in the patient (60) without requiring relative rotation between the first camera and the patient accommodation space (26). The first gamma camera (66) is adjustably mounted for reconfiguration with respect to the patient accommodation space (27) thereby enabling the development of a second, different perspective, one pass, angular sampling of the area-of-interest (61) in the patient (60). For the purpose of automatic data registration, it is advantageous to use fixed-point source markers attached to the patient, the patient pallet, or the walls of the cardiac configuration. For varying slant angle SPECT, the use of markers and their registration fulfills the same function as would center-of-rotation correction in conventional rotating camera SPECT. Namely, fixed points of the object must be back-projected at the proper angle and linear offset so as to be reconstructed as points. It is known that slant collimation introduces a potential for resolution loss due to the thickness of the scintillation crystal. This effect is referred to as the parallax component of resolution, and can be regarded as a degradation of intrinsic resolution. This, however, is commonly taken into account in the design of the collimator so that system resolution specifications are achieved, perhaps with some tradeoff of sensitivity. In many cases, the resolution may be improved because the patient is more easily positioned closer to the detector for linear scanning than for rotational scanning. While the invention has been described in detail above, the invention is not intended to be limited to the specific embodiments as described. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts. |
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046817271 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred sequence for practicing the process for producing Astatine-211 (At-211), according to the invention, includes the following steps. First, a suitable target of alpha-particle irradiated bismuth is provided, coated to a predetermined thickness on a suitable thermally conductive backing member. Next, a vapor-producing still is provided, operably connected with a condenser that has a condensate collector therein. Finally, an effluent gas filter is provided, which is operably connected to receive effluent gas from the condenser when it is operated according to the preferred process of the invention. A more detailed description of certain novel preferred embodiments of apparatus useful in practicing the process of the invention is given below. Also, desired arrangements of these various pieces of apparatus, as best used in the preferred process of the invention, will be more fully explained later. Another characterizing step in the preferred process of the invention is to heat the target of irradiated bismuth in the still, at a suitable temperature, and for a predetermined period of time that is sufficient to evolve At-211 vapor from the target. In practicing the process of the invention it has been found that such a suitable temperature is in the range of about 630.degree. to 680.degree. C., and that the predetermined heating time period should be in the range of 50 to 80 minutes. Most preferably, the target is heated at about 650.degree. C. for one hour in practicing the process of the invention. In order to carry the At-211 vapor from the still to the condenser that is connected in series with the still, in a suitable manner, such as that more fully explained below, a dry carrier gas is provided, and suitable gas conduit means are arranged with the still for passing the carrier gas through the still and the condenser. Effluent carrier gas leaving the condenser is routed through an effluent filter that is disposed in a suitable further conduit means, which is connected to the output of the condenser, in a suitable manner explained more fully in conjunction with the description of a preferred apparatus used in practicing the process, as described below. After the target-heating and distillation step of the process is completed, a suitably controlled small volume of eluent is used for eluting At-211 from the condensate collector. The eluent is selected from a desired range of solvents to be compatible with a given desired radiopharmaceutical procedure in which the At-211 activity is to be used. The concluding step of the process is to collect the At-211 in the small controlled volume of eluent, so it is ready for use in the given desired radiopharmaceutical procedure. In addition to the basic preferred process steps described above, in the best mode of practicing the process of the invention, a gas dryer apparatus is provided comprising a suitable conventional trap that is kept at about -50.degree. C. by means of a mixture of dry ice and isopropyl alcohol, or other conventional coolant. A carrier gas mixture of about 50% oxygen (O.sub.2) and 50% nitrogen (N.sub.2) is provided through suitable conventionally valved conduit means, from sources (not shown), and is passed through the gas dryer apparatus that is immersed in the dry ice and isopropyl alcohol mixture, as shown in FIG. 2, before the carrier gas is passed through the heated still in the process steps explained above. It will be recognized that other suitable means may be used for drying the carrier gas, and other suitable carrier gases, such as various mixtures of oxygen with nitrogen, argon, helium or other gases, can be used in practicing other arrangements of the process of the invention. Similarly, it will be understood that in selecting the predetermined solvents to be used in eluting At-211 from the condensate collector of the condenser a number of different solvents can be used successfully. We have found in practicing the process that a solution comprising 0.5M NaOH and 0.1M NaHSO.sub.3, used in a controlled volume of eluent that is in the range of about 0.45 to 0.65 milliliters, is effective to elute about 90% of the At-211 activity from the condensate collector, responsive to being passed through the collector only once. Accordingly, in the preferred practice of the invention only one portion of the eluent is used to elute the desired At-211 fraction from the condensate collector. In a modification of the most preferred process, such a solution of eluent was divided into a first portion and a second portion of about equal volumes (each portion being about 0.6 ml), and it was found that the first portion was effective to elute about 90% of the At-211 from the collector, while the second portion eluted a further 8% of the At-211 from the condenser. In still further tests, when additional portions of the same eluent, in about equal size volumes, were passed through the condensate collector it was found that less than 1% more of the At-211 activity was eluted from the collector with the third portion of eluent, and application of a fourth portion of eluent only removed additional traces of the At-211. Thus, it can be seen that in practicing the process of the invention with only two portions of eluent being used, about 98% of the At-211 condensed in the condensate collector can be eluted from it. Now that the general operation of the process of the invention for isolating At-211 has been described, it will help to again mention the filtering function of the apparatus shown in FIG. 2. As mentioned earlier, in order to prevent the traces of At-211 that are not isolated in the condensate collector from being undesirably discharged from the system and into the atmosphere, while the carrier gas is being used in the process as described above, effluent gas confining conduit means are connected to the output of the condenser. A suitable effluent filter is provided in that conduit means, in a suitable conventional trap arrangement, that is effective to extract any traces of At-211 from the effluent carrier gas that passes from the condenser and into the effluent filter. In the preferred embodiment of the process of the invention, porous charcoal is mounted as the effluent filter in a generally U-shaped, tubular trap through which the effluent carrier gas is passed after leaving the condenser. It will be recognized that the effluent gas filtering means, shown in FIG. 2 down stream from the condensate collector, are not an essential part of the At-211 isolating process, but rather are provided as a safety measure to prevent traces of At-211 from entering the atmosphere. In the most preferred arrangement of the process of the invention, the target of irradiated bismuth is made by first providing an aluminum backing member and forming a generally circular depression in a surface of it, for containing and confining molten bismuth. Instead of using aluminum, any thermally conductive material that can be suitably wetted with Bi can be used to make the backing member. The aluminum backing member is then heated to above the melting temperature of bismuth, i.e., to about 300.degree. C. and shavings or other suitable particles of very high purity Bi, i.e. at least 99.999 percent pure Bi, is placed in the depression formed on the surface of the heated aluminum member, in order to melt the bismuth particles. The very high purity Bi is desirable, in the preferred practice of the invention, to reduce the co-production of Po-211, which seriously interferes with radiopharmaceutical quality of the At-211 isolated by the process, as well as increasing the problems associated with radioactive waste disposal. It will be understood that the basic process of the invention can be practiced with reagent grade Bi, recognizing the foregoing problems will be encountered and should be appropriately dealt with. After the bismuth is melted, the surface of the depression on the aluminum is scratched to facilitate the wetting and uniform distribution of that surface by the molten bismuth. Subsequently, the aluminum member is cooled and the bismuth coating is machined to a smooth surface in order to form the bismuth coating in a layer of generally uniform thickness that has about 100 milligrams of bismuth per square centimeter of coated backing member area, in order to make full use of the beam of irradiating alpha particles that will be applied to it. It will be understood that the process will not be rendered inoperable if a thinner coating of Bi is used, but the yields of At-211 activity on the target will be lowered by using thinner Bi coatings. Next, the target is mounted in operating relationship to receive accelerated alpha particles from a cyclotron, or from other suitable conventional particle accelerating apparatus, in order to irradiate the target for a time period in the range of 1 to 4 hours with a beam of accelerated alpha particles having a current intensity or beam flux, in the range of 6 to 10 microamperes. In performing the irradiating step of the process, we have found that a suitable target is formed when it is irradiated with a 26.5.+-.0.5 MeV accelerating voltage alpha particle bombardment. A further desirable process step used in irradiating the target is to cool the coating of bismuth on the target by passing a flow of helium gas, at about one atmosphere pressure, over the machined surface of the bismuth target while it is being irradiated by alpha particles from the cyclotron, or other suitable accelerators. Now that a preferred sequence of the process steps of the invention has been described, along with some modifications that optimize the process for certain applications, reference is be made to FIGS. 1 and 2 of the drawings, in connection with a description of a unique preferred apparatus that is arranged in a suitable distillation and collection system for practicing the process of the invention. There is illustrated in FIG. 1, mounted in operative relationship to the output beam pipe 1 of an accelerator, such as a cyclotron, a target assembly 2, which includes a target 3 comprising a bismuth coating mounted on a suitably shaped aluminum disk, in a manner that will be more fully described. As background for that description, reference is first made to FIG. 1A to more fully explain the preferred form of the target, which the applicants used in practicing the best mode of the process of the invention. As shown, the target 3 depicted in FIG. 1A comprises an aluminum backing member 3A having a depression 3A' formed in one of its major surfaces. The depression is approximately 0.3 millimeters in depth and is formed as a circular pattern on the upper surface of the backing member. The aluminum backing member is made about 1.5 millimeters thick and is about 3.8 centimeters in diameter in order to suitably cooperate with the other elements of the target assembly 3. Of course, other suitable dimensions for the target 3 can be used in making other embodiments of a target for use in different applications. The bismuth coating 4 that is melted into the depression 3A', after the aluminum backing member 3A is suitably heated, as explained above, has its upper or outer surface machined to a smooth finish after the molten bismuth coating has cooled sufficiently to enable such machining. Referring again to FIG. 1, it can be seen that the target assembly 2 includes an isolated water-cooled 1.3 centimeter collimater 5, that is directly connected to the output of the cyclotron beampipe 1, and that has a suitable foil 6, such as a foil of Dural metal, mounted in spaced relation to it with a suitable apertured insulator 7 positioned between the collimater 5 and the Dural foil 6. A second water-cooled collimater 8, which has a 1.9 centimeter aperture, is used to conduct heat from an aluminum absorber 9. The absorber 9 is used as a degrader of alpha particle energy, of about 45 to about 27 MeV, and is positioned between the 1.9 centimeter collimater and a helium cooled chamber 10. As can be seen, the assembly 2 also includes a larger chamber 11, positioned between the Dural foil 6 and the 1.9 centimeter collimater 8. An annular collar 12 is secured to the target 3 to hold it tightly in place in its operative position, for bombardment with alpha particle the assembly 2. Helium gas from a suitable source (not shown) is passed by associated conduit means through the chamber 10 and over the face of the bismuth coating 4 on the target 3 (also see FIG. 1A), while the target is being irradiated with alpha particles from the cyclotron beampipe 1. A combined Faraday cup and target holder 13, which is also water cooled, completes the target assembly 2. It should be understood that a suitable source of cooling water (not shown) is connected by conduit means to the two collimaters 5 and 8 and to the combined Faraday cup and target holder 13 to cool these members when the target 3 is being irradiated. The arrows in FIG. 1, next to these components (5, 8 and 13) indicate the flow of such a coolant. By separating the aluminum absorber 9 from the target 3, two advantages are realized. First, the heat generated by the absorber is conducted by the 1.9 cm collimater 8 from the assembly rather than being applied to the target 3. Second, as the beam of alpha particles from the cyclotron straggles through the aluminum absorber 9, the beam is further defocused and thus prevents the formation of hot spots on the bismuth coating 4 of target 3. As noted above, in making a suitable target 3, for practicing the process of the invention, an assembly such as the target assembly 2 shown in FIG. 1 is irradiated by alpha particles from a suitable source, such as the 60 inch cyclotron that is in operation at Brookhaven National Laboratory. Of course, other suitable alpha particle accelerators or accelerating means can be used to achieve the desired irradiation of a target for use in practicing the process of the invention. In order to best practice the novel one-step distillation and astatine-211 collection procedure of the process of the invention, the novel apparatus shown in FIG. 2 was developed and assembled into the illustrated systems. This novel apparatus comprises a two-part still 20 which includes a quartz glass, generally cylindrically shaped lower part 20A and a quartz glass, partially conically shaped, upper part 20B. The parts (20A, 20B) are provided with smooth ground surfaces 20A', and 20B' at their respective abutting peripheries, to provide a joint that allows for expansion of the heated lower part 20A, relative to the upper part 20B, as the still is heated. In operation, the two parts 20A and 20B of the still are clamped together with suitable conventional ball-joint clamps (not shown), or by other suitable means. The irradiated Bi target 3 is mounted within the still 20 by placing it on a thin disk of quartz 21, which is effective to prevent the aluminum of the target 3 from attacking the glass of the bottom part of still 20A. The risk of having the still 20 cracked by such an attack is thus avoided. Suitable conventional sources of oxygen and nitrogen (not shown in detail), as indicated by the arrows 22 and 23 are fed through a suitable conduit 24 into a glass trap 25, which is immersed in a mixture of dry ice particles 25A and a solution of isopropyl alcohol 25B to maintain a temperature of approximately -50.degree. C. in the trap 25. That temperature is effective to condense moisture from, and thus dry, the carrier gas before it is passed, into discharge tube 26, that is connected through a suitable conventional connector means 27, to an inlet tube integral with the upper portion 20B of the still 20. It will be recognized that various desirable mixtures of oxygen 22 and nitrogen 23 can thus be used to supply the desired carrier gas to the still 20 in this arrangement of the apparatus used in practicing the process of the invention. The O.sub.2 concentration in the carrier gas should be sufficient to result in formation of BiO.sub.2, such that Bi metal does not vaporize along with the At-211. As explained above, in the preferred process of the invention a mixture of 50% oxygen and 50% nitrogen is used as the dry carrier gas in practicing the most preferred steps of the process of the invention. To suitably heat the still 20 for its use in the process, various furnace arrangements can be used. However, the applicants found that commercially available glove boxes are limited in volume to about 1/2 cubic meter, so if they were to be used with commercially available hot plates, which are generally relatively high powered, the hot plates would cause the inside temperature of such glove boxes to exceed safe limits. In that respect, it should be understood that, due to the biological activity of Astatine, the desired distillation procedure used in practicing the disclosed process must be carried out in an enclosure similar to a glove box. To overcome these problems, a small furnace 30 was constructed, with about 300 centimeters of Nichrome wire 30A wrapped around a spiral shaped quartz rod 30B. The Nichrome wire was made of 80% nickel and about 20% chromium, and was 24 gauge, having about 1.5.times.10.sup.-4 ohms per centimeter resistance. The Nichrome wire filament 30A was immersed in an asbestos compound 31 disposed in a shallow quartz dish 32. A suitable conventional Variac 33 was connected in a well known manner to a suitable source of 110 volt electric power (not shown in detail), to accurately control the temperature generated by the furnace 30. A quartz disk cover 30C was positioned over the quartz dish 32 to support a suitable stainless steel heating block 34 that has a chromium-aluminum thermocouple 35 mounted within it, as shown. The thermocouple is connected to a suitable conventional temperature indicating means 36, which enables an operator to accurately measure and control the temperature of the still 20 by suitably adjusting the furnace Variac 33. For convenience, the furnace 30 was mounted on an adjustable table 37, which was covered by a suitable insulator plate 38 that protects it from the heat of the furnace. It will be understood that in operation of the distillation step of the subject process, the lower part 20A of the still 20 should be positioned within the recess 34R formed in the heat block 34. Returning now to the description of the distillation and collection apparatus shown in FIG. 2, there is illustrated a quartz glass condenser 40, which in this preferred form is a column condenser. About a 2 millimeter inside diameter is provided in the column of condenser 40, and it has a cooling water inlet port 40A and outlet port 40B, which are operably connected to a suitable source of water and associated water discharge means (neither are shown, except by the depicted arrows). Condenser 40 is coupled in operating relationship to the still 20 by a suitably formed quartz glass connector tube 41, which has ground surfaces at its opposite ends to form fluid tight seals with the upper end of the discharge port 20B' of the still, as well as with the lower inlet port of the column condenser 40, respectively. A suitable condensate collector 42 is positioned within the column condenser. In a preferred form the condensate collector 42 comprises silica gel in the form of a 60 to 100 mesh (up to 200 mesh has also been found suitable) that is commercially available. The silica gel mesh is washed with concentrated nitric acid, then flushed with triple distilled water and dried at 110.degree. C., before it is used in the process of the invention. The condensate collector 42 is held in position within the condenser 40 by pads of quartz wool 43 and 43A, which are, respectively, mounted adjacent to the inlet and outlet ports of condenser 40. Similarly, another pad of quartz wool 29 is positioned in the neck of the port 20B' of still 20, as shown in FIG. 2. This works as a filter to remove any Bi target metal which may be volatized by the still. A second commercially available connection tube 44, having ground inlet and outlet surfaces for effecting fluid type seals, respectively, with the outlet end of condenser 40 and the inlet end of an effluent discharge conduit means 45, is positioned in the system, in the location shown, to connect the condenser 40 to the effluent gas discharge conduit means. In order to ensure complete removal of essentially all astatine radio activity from the carrier gas effluent leaving the condenser 40, an effluent filter 46, which in the preferred apparatus used in the system shown in FIG. 2 comprises a body of porous charcoal mounted in a generally U-shaped tubular quartz glass trap 46A, is connected to the effluent discharge conduit means 45. Pads of glass wool 47, or other suitable filter material, are used to hold the particles of porous charcoal in position within the trap 46A. Finally, an absolute filter 48 of suitable conventional design, is positioned in the discharge port connected to the end of the trap 46A, as shown, to further assure the removal of all astatine activity from the effluent gas that is discharged from the system. It will be recognized that other effluent gas filtering arrangements can be used, but we have found that only a small fraction, i.e. substantially less that 1%, of the astatine activity escapes from the silica gel condensate collector 42 with the apparatus shown in FIG. 2; thus, the charcoal filter 46 and absolute filter 48 have proven effective to assure essentially the complete removal of all remaining astatine activity from the effluent discharge. As pointed out above, the filters 46 and 48 are not necessary to the effective practice of the invention. Those filters are used in the disclosed embodiment, only as a safety precaution. In using the apparatus shown in FIG. 2 to practice the preferred process of the invention, all of the quartz glassware components, including the still 20 and column condenser 40, are preferably washed with hot nitric acid, then with chromic acid, then with distilled and redistilled water, and are then dried for several hours by baking them at about 110.degree. C. The component parts of the apparatus are then assembled into the system shown in FIG. 2 and are preferably baked in that assembled state at about 660.degree. C. for 8 to 12 hours. During a portion of that latter baking period, the target 3 is being suitably irradiated by being operably mounted, as explained above, to be bombarded with alpha particles from a suitable accelerator, such as a cyclotron. About two hours before the scheduled end of the irradiation step, the assembled apparatus shown in FIG. 2 is removed from the baking furnace and allowed to cool to room temperature. Next, cooling water is connected to the ports 40A and 40B of the condenser 40, and the irradiated target 3 is placed on the quartz disk 21 within the still 20. The still parts 20A and 20B are clamped together and Nitrogen gas 23 is then passed through the apparatus to flush the system. The ratio of oxygen to nitrogen in the dry gas supply is then adjusted to about 50% oxygen and 50% nitrogen, using the conventional needle valves shown schematically down stream from the inlet gas-indicating arrows (but not numbered) in FIG. 2. Next, the Variac 33 is then adjusted to bring the furnace 30 up to a desired temperature within the range of 630.degree. to 680.degree. C. In several production runs with the process, excellent production of At-211 was attained when the furnace was maintained at about 650.degree. C. during the distillation procedure. After the furnace has operated for about 1 to 4 hours to effect the desired distillation of At-211 from the target 3, the furnace 30 is turned off and removed so that the still 20 can cool down for about 10 minutes. The cooling water to the condenser 40 is turned off and the supplies of carrier gas 22 and 23 are also turned off. Subsequently, the column condenser 40 is removed from its connection with the connector tubes 41 and 44 and a controlled small volume, such as about 0.5 milliliters, of eluent containing a choice of predetermined solvents, such as the solution of 0.5M NaOH and 0.1M NaHSO.sub.3, described above, is used to elute about 90% of the At-211 activity from the silica gel condensate collector 42. FIG. 3 shows a typical elution curve for At-211 activity, as achieved in practicing the process of invention. From the curve shown in FIG. 3, it can be seen that about 90% of the At-211 activity is eluted with the application of a first portion of about 0.6 milliliters of eluent when it is passed through the condensate collector 42. When a second, approximately equal controlled volume of eluent is passed through the condensate collector, it is seen that an additional approximately 8% of the astatine activity is eluted from the collector. Finally, when successive third and fourth portions of about equal controlled volumes of eluent are passed through the condensate collector, about an additional 1% of the activity is removed with the third portion and only a trace of remaining activity is removed with the fourth portion of eluent. The effect of variations in the duration of the distillation step of the process of the invention, i.e., as it effects recovery of At-211, is shown in FIG. 4. Curve A in FIG. 4 shows that about 80% of the astatine activities are distilled in the first hour of operation of the heated still 20, when the still is heated to a temperature in the range of 630.degree. to 670.degree. C. Further, it is seen that after the first hour, the rate of distillation increases slowly with time but, due to the decay of At-211, which has a half life of 7.21 hours, the overall yield actually decreases with time, as shown by curve B in FIG. 4. Thus, it will be recognized that in a preferred distillation procedure for the process of the invention the distillation step is effected in approximately one hour, although longer distillation periods, e.g. up to three hours have been used with only minor loss in overall yield, as indicated by the curve B in FIG. 4. SAMPLE RESULTS Numerous production runs with the process of the invention have been conducted by the applicants to determine the effects of variations in target irradiation dosages on the percentage recoveries of At-211 that are achievable with it. The following Table I summarizes data from ten of those runs. In conducting those runs the 60 inch cyclotron at Brookhaven National Laboratory was used as the source of alpha particle irradiation for an aluminum-backed Bi target in which the Bi coating was about 1.0 millimeter thick and was manufactured according to the preferred process steps described above. An acceleration voltage of 44 MeV at the extraction beam pipe of the cyclotron was maintained on the irradiating beam. An aluminum absorber (as shown in FIG. 1), averaging 110.4 mg/cm.sup.2, was used in the target assembly, mounted in series with a 1.25 mil thick Dural metal foil, in the manner explained above in connection with the preferred target assembly irradiation process steps. The aluminum absorber is effective to degrade the incident beam energy from about 44 MeV to about 26.5.+-.0.5 MeV. Similarly, the distillation temperature and duration, as well as the dry carrier gas (50/50 mixture of O.sub.2 and N.sub.2), and eluent solution (0.5M NaOH and 0.1M NaHSO.sub.3) gas used, were maintained in the preferred ranges set forth in the foregoing description of the process, and a small controlled volume of eluent (0.45 to 0.65 ml) was used as a single portion application in each of the runs summarized in Table I. TABLE I __________________________________________________________________________ Recovery of At-211 in Actual Production Runs (.mu.A-hr.)DoseIrradiation (hr.)IrradiationDuration of (.mu.A)Flux IAverage (mCi)YieldAt-211 ##STR1## (%)RecoveryAt-211 __________________________________________________________________________ ProcessBefore RecoveryTarget Dosage 1.0011.001 0.14010.1396 7.157.17 0.4120.422 ##STR2## 100 __________________________________________________________________________ Processed Targets Run No. __________________________________________________________________________ 1 31.7 3.5 9.1 4.56 1.8 41 2 10.0 1.3 7.9 2.80 3.1 71 3 10.9 1.6 6.7 2.60 2.7 62 4 29.0 3.0 9.7 5.86 2.4 55 5 24.5 3.2 7.6 4.59 2.3 53 6 14.5 1.8 8.2 3.15 2.4 55 7 27.0 2.9 9.3 5.00 2.2 50 8 36.7 3.9 9.4 7.14 2.4 55 9 28.0 3.0 9.2 4.82 2.1 48 10 38.0 3.95 9.6 8.91 2.9 66 __________________________________________________________________________ Avg. 56 .+-. 13 __________________________________________________________________________ In Table I it should be understood that the top two horizontal lines of data (shown above the double line and below the column headings) relate to the target dosage before the target was used in the process runs (1-10) listed in the lower portion of the Table. An average saturation yield of At-211/per I(.mu.Amp) for two such runs was used as a 100% value for At-211 recovery. As shown by the column headings, the irradiation doses in microampere-hours, (Col. 2) equals the product of the values shown for the duration of irradiation (Col. 3) and the average irradiation current or flux density (Col. 4). The At-211 activity yields, measured in millicuries for the respective runs, is shown in the fifth column. Col. 6 shows the quotient obtained by dividing the Astatine saturation yield for each target by the related average flux (I, Col. 4) for each run. Finally, the seventh column shows the percentage recoveries of At-211 realized from the respective runs, using the average target dosage value 4.37, shown above the double line at the top of Col. 6. Thus, the respective recovery percentages shown in Col. 7 are determined by dividing the Col. 6 figure, in each run, by 4.37. The production data for the process runs summarized in Table I show that the process of the invention was proven effective to recover an average of 56%.+-.13% (bottom of Col. 7) At-211 for those runs. This high level of recovery is believed to constitute a substantial improvement over any other practical known process for producing At-211 in small controlled, readily usable, volumes. An important feature of the process of the invention is that its practice does not require the use of any other chemicals in order to isolate the desired At-211, thus, the risk of introducing contaminants such as those frequently present in other chemicals, is completely avoided. It will be apparent that in light of the teaching of the invention disclosed herein various modifications and further alternative sequences of the disclosed process steps can be readily developed by those skilled in the art. Accordingly, it is out intention to encompass the true limits and scope of the invention within the following claim. |
051587386 | claims | 1. Method of controlling a pressurized water nuclear reactor comprising a nuclear reactor and plurality of control bars adapted to be selectively and individually positioned in the reactor core for controlling the reactivity of the core, the negative reactivity provided by said control bars when fully inserted in the core being sufficient for compensating all reactivity variations which may intervene during normal operation of the reactor and upon an incident which requires that the reactor be rendered sub-critical while the pressurized water is at the normal temperature for operation of the reactor, said method comprising the steps of: (a) determining: the current value of an operating parameter indicative of the power developped by the reactor core; the current positions of the control bars; and the axial power distribution offset in the core; (b) when the difference between said current value of the operating parameter and a set value exceeds a predetermined deadband interval, computing the amount by which the reactivity of the core should be modified; (c) determining, through a simulation process on a model of said reactor, which ones of the control bars may be moved and predicted amounts of displacement to be given to said ones of the bars for bringing back said difference within said deadband without modifying said axial power distribution offset out of a reference range and while minimizing a core enthalpy increase factor; and (d) moving said ones of said bars by said amounts of movement. comprising the steps of: (a) measuring the current value of an operating parameter indicative of the power developped by the reactor core, the current positions of the control bars and the axial power distribution offset in the core, (b) when the difference between said current value of the operating parameter and a set value exceeds a predetermined deadband interval, computing the amount by which the reactivity of the core should be modified and the change in the negative reactivity provided by said control bars which is necessary for decreasing said difference to zero, (c) randomly selecting at least one bar within the core or within a sector of the core and simulating changes in negative reactivity to be expected from a plurality of assumed amounts of movement of said at least one bar, said assumed amounts of movement having an average value substantially equal to the amount of movement which would result in the necessary negative reactivity change, (d) computing the predicted variation of the axial power distribution offset which would result from each of said assumed movements and determining whether said predicted variation results in an axial power distribution offset exceeding a predetermined reference value, (e) if said predetermined reference value is exceeded, repeating steps (c) and (d) until the variation of axial power distribution offset does not result in a power axial offset exceeding said predetermined reference value, (f) computing the variation of an enthalpy elevation factor of the core resulting from the simulated amount of movement, (g) storing the simulated amount of movement of said at least one bar if said simulated amount of movement decreases the enthalpy factor, while storing or omitting to store said simulated amount of movement with a probability which is responsive to the degree of said variation if said simulated amount of movement increases the enthalpy factor, (h) repeating steps (b)-(g) until the accumulated negative reactivity change due to the stored amount of movement is equal to the necessary change, with a permissible deviation, and (i) moving said at least one bar by said stored amounts of movement. kT is a constant value which is greater than the maximum value of .DELTA. (F.DELTA.H) by at least one order of magnitude. comprising the steps of: (a) determining: the current value of an operating parameter indicative of the power developped by the reactor core; the current positions of the control clusters; and the axial power distribution offset in the core; (b) when the difference between said current value of the operating parameter and a set value exceeds a predetermined deadband interval computing the amount by which the reactivity of the core should be modified; (c) determining, through a simulation process on a model of said reactor, which ones of the control clusters may be moved and predicted amounts of displacement to be given to said ones of the bars for bringing back said difference within said deadband while minimizing a core enthalpy increase factor; (d) after determining each said predicted amount of displacement computing the resulting axial offset, verifying that the predicted amount of displacement does not cause the axial offset difference to move out of a predetermined reference range, discarding the predicted displacement if it exceeds in the affirmative and retaining the predicted amount of displacement in the negative; and (e) moving said ones of said clusters by said amounts of movement. 2. Method of controlling a pressurized water nuclear reactor comprising a nuclear reactor and a plurality of control bars adapted to be selectively and individually positioned in the reactor core for controlling the reactivity of the core, 3. Method according to claim 2, wherein the variation in the axial power distribution offset is computed after said at least one bar and the amount of displacement to be given to said at least one bar have been stored. 4. Method according to claim 2, wherein said probability is computed as: EQU P=exp[.DELTA.(F.DELTA.H)/kT] 5. Method according to claim 4, wherein kT is initially given a value which leads to a probability which is close to 1 and is progressively decreased as long as the probability retains an average value which is higher than a predetermined value. 6. Method according to claim 2, further comprising fractionating said core into a plurality of virtual angular sectors all having the same arrangement, wherein all control bars having the same positions in all sectors are simultaneously moved by the same extent. 7. Method according to claim 6, wherein said bars having the same positions in the different angular sectors are moved by the same extent. 8. Method according to claim 6, wherein said bars having the same positions in the different angular sectors are moved by different extents and the different extents are selected by applying a correction about an average value which compensates for radial power offsets. 9. Method according to claim 2, wherein the reactor is maintained in sub-critical condition after it has been shut-down with additional bars each having a neutron absorption which is approximately double that of a control bar. 10. Method according to claim 2, comprising the additional step of modifying the neutron energy spectrum by progressively removing bars which contain burnable poison from the core. 11. Method according to claim 2, wherein said control bars are distributed in pairs, the two bars of a same pair being at a same location in the core. 12. Method of controlling a pressurized water nuclear reactor comprising a nuclear reactor and a plurality of control clusters adapted to be selectively and individually positioned in the reactor core for controlling the reactivity of the core, the negative reactivity provided by said control clusters when fully inserted in the core being sufficient for compensating all reactivity variations which may intervene in normal operation of the reactor and upon an incident which requires that the reactor be rendered sub-critical while the pressurized water is at the normal temperature for operation of the reactor, |
abstract | The invention describes a method for stripping alumina which is particularly suitable for removal of fluoride from alumina and comprises washing said alumina with an aqueous acid or alkali at elevated temperature. The method may be used for removal of unreacted radiofluoride such as [18F]fluoride from alumina following a radiofluorination reaction. Automated synthesis apparatus and cassettes therefor, which are adapted to perform the method are also claimed. |
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039403149 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a nuclear reactor fuel element which consists of a multiplicity of fuel rods, disposed or held in spaced relation by spacers arranged in several planes, and fastened to at least one support plate. Each fuel rod has a tubular casing which contains the nuclear fuel, for instance, in the form of pellets. Next to the fuel rods, these spacers constitute the most essential structural units within the fuel elements because by means of these spacers the fuel rods are maintained in a predetermined spacial relation. This is necessary so that over the entire life of the nuclear reactor, a completely uniform cooling of the fuel rods and the fuel elements is achieved by the reactor coolant. The reactor coolant may be either a gas or a liquid. 2. Description of the Prior Art It is known that spacers automatically interact with the fuel rods and the latter, in turn, interact with the tubular casings. For this reason, the type of material and the wall thicknesses of the parts in contact with each other must be matched to each other, taking into consideration the mechanical forces which may occur. Thus, the wall thicknesses of the tubular casing should be so large that mechanical damage to the tubular casings cannot occur. On the other hand, the total amount of structural material within the active zones of the reactor core should be kept as low as possible for reasons of neutron efficiency. In addition, the problems of heat removal and creep at the operating temperature of the reactor are important considerations. SUMMARY OF THE INVENTION The object of this invention is to find the optimum fuel element design which meets the foregoing requirements. According to the invention, this is achieved by designing the wall thickness of the tubular casings for the fuel rods without regard to the mechanical stress produced by the spacers and enlarging it according to the height of the spacers. Using this design criteria, it is possible to achieve the optimum design of the wall thickness of the tubular casing only on the basis of the operating conditions of the nuclear reactor, such as pressure, temperature, operational cycles and fuel expansion, as a function of fission gas pressure, swelling of the fuel, creep behavior of the material, etc. The mechanical stresses produced by the spacers are only taken into consideration at the contact points between the spacers and the tubular casings at the height of the spacers. At these points, the wall thickness of the tubular casings is larger. By using fuel elements of this design, instead of conventional fuel elements, substantially less tubular-casing material, such as Zircaloy, needs to be built into the nuclear reactor. As a result, losses caused by this material through neutron absorption can be reduced. This design criteria applies to practically all types of nuclear reactors. To illustrate this further, a fuel element for a heavy-water cooled nuclear reactor will be described in more detail. Such a fuel element has a circular cross section and is used in the reactor core within so-called separation tubes. The idea of the invention shown here can, of course, also be applied to fuel elements of other cross sections and geometry. So-called guide ducts are sometimes attached to the tubular casings of the fuel rods at the height of the spacers. Attachment of such guide ducts by means of soldering or welding always involves a heat treatment, which may in some cases bring with it the danger of premature defects in the material of the tubular casing due to metallurgical changes. The present invention provides a way of avoiding such defects and other influences on the structure of the tubular casings when such guide ducts are attached. The spacers can be brought into contact directly at the fuel rods, i.e., at their reinforced points, which facilitates a relatively simple design. Likewise, mechanical stress on the tubular casings when the fuel rods are inserted into or moved in the spacers is practically eliminated. |
abstract | An anti-scatter grid for radiography includes a plurality of generally radiation absorbing elements and a plurality of generally non-radiation absorbing elements in which the generally non-radiation absorbing elements include a plurality of voids. Desirably, the non-radiation absorbing elements include an epoxy or polymeric material and a plurality of hollow microspheres. Disclosed is also an apparatus for forming an anti-scatter grid in which the apparatus includes a pivoting arm and surface for use in aligning a plurality of spaced-apart generally radiation absorbing elements relative to a radiation source. |
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claims | 1. A method for extracting a primary diffuse radiation spectrum from a diffusion spectrum of diffuse radiation, according to a diffusion angle, coming from a material exposed to incident radiation through a surface, the method comprising:application of a spectral response function corresponding to a multiple diffuse radiation spectrum when a photon with a given energy belonging to the primary diffuse spectrum is detected,wherein the spectral response function comprises a correlation matrix (M) of which each value aij corresponds to a number of detected photons, with energy Ei, constituting the multiple diffuse radiation, when a photon of the primary diffuse spectrum is detected with energy Ej. 2. The method according to claim 1, wherein the spectral response function supplies a discretized spectrum over a finite number of energy ranges. 3. The method according to claim 1 further comprising an iterative process in which each step includes an estimation of the multiple diffusion spectrum to create an estimated multiple diffusion spectrum following a preceding estimation of the primary diffuse radiation spectrum and a new estimation of the primary diffuse radiation spectrum, by subtracting the estimated multiple diffusion spectrum from the diffusion spectrum, wherein the iterative process is continued until satisfaction of a convergence criterion related to successive estimated primary diffusion spectra. 4. The method according to claim 1, wherein the spectral response function comprises a result of interpolating a plurality of spectral response functions to monochromatic exposure of different materials for a given depth considering only the density of the different materials. 5. The method according to claim 1, wherein the spectral response function comprises a result of interpolating a plurality of spectral response functions to monochromatic exposure of the material for different depths. 6. The method according to claim 1, wherein the spectral response function is obtained beforehand by experimental acquisition of a response to monochromatic exposure of the material for a given depth. 7. The method according to claim 1 further comprising a preliminary estimation of a first estimated primary diffuse spectrum, carried out by multiplying a measured total diffusion spectrum by a multiplication coefficient dependent of the inspection depth. 8. The method according to claim 1, wherein the radiation comprises X rays. 9. A device for extracting a primary diffuse radiation spectrum from a diffusion spectrum of a diffuse radiation through a material to be analyzed, the device comprising:a source of incident radiation configured to irradiate a surface of the material;a detector configured to detect the radiation diffused by the material according to at least one preselected diffusion angle; andmeans for applying a spectral response function corresponding to a multiple diffuse radiation spectrum when a photon is detected with given energy belonging to the primary diffuse radiation spectrum, wherein the spectral response function comprises a correlation matrix (M) of which each value aij corresponds with a number of detected photons, with energy Ei, constituting the multiple diffuse radiation, when a photon of the primary diffuse radiation is detected with energy Ej. 10. The device according to claim 9, wherein the radiation source and the detector are both strongly collimated. 11. The device according to claim 9, wherein the detector resides in a same half-space as the radiation source opposite the irradiated surface of the material. 12. A device for spectrometry analysis comprising a device for extracting a spectrum of primary diffuse radiation according to claim 9. 13. A non-transitory computer readable media including a sequence of instructions that, when executed by a microprocessor, implement the method according to claim 1. |
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abstract | A core catcher includes a holding surface that catches and holds corium and that introduces a surrounding coolant into the core catcher and cool the core catcher by heat exchange with the introduced coolant. The holding surface and the cooling unit are constructed by arranging blocks which each include a polyhedron having at least one pair of parallel surfaces and having an opening portion formed in a surface located in a lateral direction when a first surface that is one of the parallel surfaces is arranged as a bottom surface and are configured such that the polyhedrons communicate with each other via the opening portion when the polyhedrons are arranged adjacent in the lateral direction. The core catcher can achieve easier installation of the blocks without an increase in installation cost. |
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abstract | A scintillator panel includes a substrate, a resin protective layer formed on the substrate and made of an organic material, a barrier layer formed on the resin protective layer and including thallium iodide as a main component, and a scintillator layer formed on the barrier layer and including cesium iodide with thallium added thereto as a main component. According to this scintillator panel, moisture resistance can be improved due to the barrier layer provided therein. |
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052672751 | description | DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The numeral 10 generally designates an apparatus for sealing a joint between a base surface 12 and a sealing device or hollow body 14 having mating end surface 16 with a packing ring or compression gasket means 18. The apparatus 10 is located in a positive pressure environment P.sub.1 such as a boiling water nuclear reactor vessel, and includes a preloading force element 20 for use in response to pressure P.sub.1 against the end 22 of the hollow body 14 opposite its mating end surface 16 and packing ring 18. The apparatus 10 provides a means for establishing, through use of the single element 20, a variable spring preload over the joint area around a leak path 24 to be sealed which will maintain the gasket means 18 under a compressive load sufficient to establish a leak tight or leak limiting joint. As fully taught in U.S. Pat. No. 4,826,217, establishing seals on inclined and/or non-planar surfaces in the bottom of a boiling water nuclear reactor may require a non-uniform or non-symmetric preloading of the sealing gasket 18 over the base surface 12. In FIG. 1, for example, the base surface 12, which is the inside of a boiling water reactor vessel bottom, and the mating end surface 16 are both inclined at an angle (x) to the preload force direction (vertical) for sealing by means of a face seal compression gasket 18. If the application prohibits positive guiding of the hollow body or sealing device 14, it will be necessary to exert a greater percentage of the preload on the downhill side. This is required to limit tendency of the hollow body 14 from slipping downhill and to resist a pressure force (resulting from different uphill and downhill surface areas) that will rotate the sealing device toward the uphill side. The asymmetric preloading force element 20 is a ring of substantial axial depth into which a plurality of circumferentially directed and radially directed through wall slots e.sub.1 to e.sub.3 of varying heights, lengths or angles are machined. The slots can be formed in a stacked pattern and spaced in any variable pattern to achieve an element with the required preload as a function of location. Designing the preloading force element 20 is performed by modeling the element using curved beams loaded normal to the plane of curvature which represents springs in series and series-parallel combinations. By adjusting the size of slots e.sub.1 to e.sub.3 and properly spacing them geometrically and circumferentially, an asymmetric preloading force on the end of hollow body 14 can be obtained in register and alignment with gasket 18. FIG. 3 shows what a typical force schematic drawing showing relative preload force vectors for the apparatus 10 with a spring constant varying from a high to a low value around the circumference of the preloading force element 20, showing the relative asymmetric preloading on the inclined surfaces 12 and 16, and gasket means 18. The left side of FIG. 3 corresponds to the left side of FIGS. 1 and 2. The asymmetric preloading force element 20 of the invention offers several advantages over devices of the prior art such as Belleville washers or springs. Its main advantage is that it offers more flexibility of design in establishing varying spring rates as a function of circumferential location. It also has an improved reliability in that a majority of the intended design preload can be maintained even with through wall failure of a single (or small number of) the slotted elements. |
052232069 | summary | FIELD OF THE INVENTION This invention relates to an improvement in the manufacture of composite constructed nuclear fuel containers for service in water cooled nuclear fission reactors, such as, for example, the fuel elements disclosed in U.S. Pat. No. 4,200,492, issued Apr. 29, 1980; and U.S. Pat. No. 4,372,817, issued Feb. 8, 1983, and related disclosures cited therein and available in the fuel area of the nuclear literature. BACKGROUND OF THE INVENTION Nuclear fuel containers are subject to leakage failures attributable to corrosion, in particular a phenomenon defined in this technology as stress corrosion cracking, an occurrence which is primarily induced or accelerated by abrupt or rapid reactor power increases. Composite nuclear fuel containers, or fuel elements, have been introduced and frequently employed in power generating, commercial water cooled nuclear fission reactor plants to cope with this shortcoming of stress corrosion cracking. Composite nuclear fuel containers comprise a generally conventional tubular container, constructed of a zirconium alloy, stainless steel, aluminum, or other suitable alloy of the art, provided with an internal lining which functions as a protective barrier, and is composed of a metal having increased resistance to intergranular stress corrosion cracking, or other forms of destructive attack. The barrier linings of the art comprise a variety of metals and alloys, including zirconium metal of substantial purity, for example less than about 5000 parts per million impurities, copper, molybdenum, tungsten, rhenium, niobium and alloys thereof. Examples of such protective metal barrier linings for nuclear fuel tubular containers comprise U.S. Pat. No. 4,200,492, issued Apr. 29, 1980; U.S. Pat. No. 4,372,817, issued Feb. 8, 1983; U.S. Pat. No. 4,390,497, issued Jun. 28, 1983; U.S. Pat. No. 4,445,942, issued May 1, 1984; U.S. Pat. No. 4,659,540, issued Apr. 21, 1987; U.S. Pat. No. 4,942,016, issued Jul. 17, 1990; and U.S. Pat. No. 4,986,957, issued Jan. 22, 1991. Typical composite fuel containers of the art, comprising a tubular containing having a metal liner providing an internal barrier layer metallurgically bonded to its inner surface, are produced by inserting a section of a large diameter, hollow liner stock unit in close fitting intersurface contact into and through the length of a section of a large diameter tube stock. This composite assembly of large diameter section of tube stock with inserted liner stock is then subjected to a series of circumference reductions with each reduction accompanied by a following heat annealing to reduce the hardness imposed by the cold work distortion of the diameter reduction. Various methods can be used to metallurgically unite the tube and liner components, including explosive bonding, heating under compressive loading to cause diffusion bonding, and extension of the assembly. Detailed examples of methods for producing such composite constructed nuclear fuel containers are given in U.S. Pat. No. 4,390,497, issued Jun. 28, 1983; U.S. Pat. No. 4,200,492, issued Apr. 29, 1980; and U.S. Pat. No. 4,372,817, issued Feb. 8, 1983. In addition t the conventional annealing heat treatments for the purpose of relieving reduction compression induced stresses in the metal of the reduced composite tube and liner unit, it has become a common practice in this field to subject such nuclear fuel containers to specific modifying heat treatments to enhance or optimize a critical property thereof such as corrosion resistance or ductibility as a means for improving the fuel elements continuing durability. For instance, it is well known to heat treat zirconium metal and its alloys, or components formed thereof, up to a temperature of above the alpha microcrystalline phase of the particular metal composition, or to the alpha plus beta or beta microcrystalline phase, followed by rapid cooling to preserve significnat or critical aspects of the resulting heat induced microstructure state. Such heat treatments are disclosed in detail in the prior art, for example U.S. Pat. No. 2,894,866, issued Jul. 14, 1959; U.S. Pat. No. 4,390,497, issued Jun. 28, 1983; U.S. Pat. No. 4,238,251, issued Dec. 9, 1980; and U.S. Pat. No. 4,576,654, issued Mar. 18, 1986. Temperatures for producing the various potential microstructure changes and accompanying property modifications disclosed in the literature typically depend upon the exact composition of the metal or alloy, and are essentially a unique condition for each different metal or combination of alloying ingredients. Thus if the temperature conditions to achieve or optimize a particular characteristic in a specific composition is no readily available in the literature, it can be ascertained empirically, note for example U.S. Pat. No. 2,894,866, issued Jul. 14, 1959; and U.S. Pat. No. 4,238, 251, issued Dec. 9, 1980. The disclosures and contents of all the aforesaid U.S. Letters Patent, and the references cited therein, are incorporated herein by reference. SUMMARY OF THE INVENTION This invention comprises an improved method for producing composite constructed nuclear fuel containers for service in water cooled nuclear reactors which enables optimizing desired available characteristics of the respective metal components of the composite fuel containers or elements. The invention includes heat treatment procedures that provides for introducing or enhancing distinctive or unique properties such as corrosion resistance or ductility in each of the several metal components of a composite nuclear fuel element. |
063109387 | claims | 1. A method for determining tracking control parameters for positioning an x-ray beam of a computed tomography imaging system, the imaging system including a movable collimator positionable in steps and a detector array including a plurality of rows of detector elements, said method comprising the steps of: obtaining detector samples at a plurality of collimator step positions while determining a position of a focal spot of the x-ray beam; determining a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray beam, collimator, and detector array; determining a detector element differential error according to ratios of successive collimator step positions; and selecting a target beam position for an isocenter element in accordance with the determined element differential errors. determining a collimator z-axis position offset from the detector array centerline at a point at which outer detector row signals are reduced to a full width at a half maximum; and determining a focal spot position as a function of the determined collimator z-axis position and the geometric parameters of the x-ray beam, collimator, and detector array. weighting the detector element differential error by a reconstruction error sensitivity function; determining a step position at which the weighted detector element differential error exceeds a predetermined limit; and setting a tracking beam position for the isocenter detector element at a distance from the determined step position preceding a step that exceeds a predetermined artifact limit by an amount that exceeds a tracking loop positioning error. b(i)=an artifact threshold (% differential error) for a double detector element error; and ##EQU4## obtaining detector samples at a plurality of collimator step positions while determining a position of a focal spot of the x-ray fan beam; determining a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray fan beam, collimator, and detector array; and determining a beam position transfer function for a ratio of an average of detector outer row signals to detector inner row signals for a set of detector elements at an extreme end of the x-ray fan beam in accordance with a selected approximation over a selected ratio range between a minimum and a maximum ratio for the plurality of collimator step positions. obtain detector samples at a plurality of collimator step positions while determining a position of a focal spot of the x-ray beam; determine a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray beam, collimator, and detector array; determine a detector element differential error according to ratios of successive collimator step positions; and select a target beam position for an isocenter element in accordance with the determined element differential errors. determine a collimator z-axis position offset from the detector array centerline at a point at which outer detector row signals are reduced to a full width at a half maximum; and determine a focal spot position as a function of the determined collimator z-axis position and the geometric parameters of the x-ray beam, collimator, and detector array. weight the detector element differential error by a reconstruction error sensitivity function; determine a step position at which the weighted detector element differential error exceeds a predetermined limit; and set a tracking beam position for the isocenter detector element at a distance from the determined step position preceding a step that exceeds a predetermined artifact limit by an amount that exceeds a tracking loop positioning error. b(i)=an artifact threshold (% differential error) for a double detector element error; and ##EQU5## obtain detector samples at a plurality of collimator step positions while determining a position of a focal spot of the x-ray fan beam; determine a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray fan beam, collimator, and detector array; and determine a beam position transfer function for a ratio of an average of detector outer row signals to detector inner row signals for a set of detector elements at an extreme end of the x-ray fan beam in accordance with a selected approximation over a selected ratio range between a minimum and a maximum ratio for the plurality of collimator step positions. 2. A method in accordance with claim 1 wherein the plurality of detector rows are z-axis detector rows, and the detector array has a centerline perpendicular to the z-axis, an outer detector row, and an inner detector row: said determining a position of a focal spot of the x-ray beam comprises the steps of: 3. A method in accordance with claim 1 further comprising the step of offset-correcting and view-averaging the obtained detector samples at a plurality of collimator step positions to obtain a set of detector samples for each collimator step position used in said step of determining a beam position and said step of determining a differential error for selection of the target beam position. 4. A method in accordance with claim 1 wherein selecting a target beam position for an isocenter detector element in accordance with the determined element differential errors comprises the steps of: 5. A method in accordance with claim 4 wherein the reconstruction error sensitivity function is detector element dependent. 6. A method in accordance with claim 5 wherein the reconstruction error sensitivity varies according to a distance of the detector element from an isocenter element. 7. A method in accordance with claim 4 wherein the detector rows have at least 214 elements on each side of an isochannel element, and the reconstruction error sensitivity function is: EQU w(i)=0.18/b(i); 8. A method for determining tracking control parameters for positioning an x-ray fan beam of a computed tomography imaging system, the imaging system including a movable collimator positionable in steps and a detector array including a plurality of rows of detector elements including at least an inner row and an outer row, said method comprising the steps of: 9. A method in accordance with claim 8 wherein determining a beam position transfer function comprises the steps of fitting, to a polynomial function, the determined beam positions at each step as a function of the ratio of an average of detector outer row signals to detector inner row signals. 10. A method in accordance with claim 9 wherein the polynomial function is a fourth degree polynomial. 11. A method in accordance with claim 8 further comprising the step of determining a valid measurement range of the transfer function as end limits of the plurality of collimator step positions for which an error between beam positions computed using the transfer function and an actual beam position is less than a predetermined limit. 12. A method in accordance with claim 11 wherein the predetermined limit is between 0.1 millimeters and 0.6 mm. 13. A method in accordance with claim 11 wherein the predetermined limit is 0.2 millimeters. 14. A computed tomography imaging system comprising an x-ray source, a detector array including a plurality of rows of detector elements, and a movable collimator positionable in steps and configured to collimate and position an x-ray beam produced by said x-ray source on said detector array, said system configured to: 15. A system in accordance with claim 14 wherein the plurality of detector rows are z-axis detector rows, and the detector array has a centerline perpendicular to the z-axis, an outer detector row, and an inner detector row; and said system being configured to determine a position of a focal spot of the x-ray beam comprises said system being configured to: 16. A system in accordance with claim 14 further configured to offset-correct and view-average the obtained detector samples at a plurality of collimator step positions to obtain a set of detector samples for each collimator step position used in determining said beam position and in determining said differential error for selection of said target beam position. 17. A system in accordance with claim 14 wherein said system being configured to select a target beam position for an isocenter detector element in accordance with the determined element differential errors comprises said system being configured to: 18. A system in accordance with claim 17 wherein the reconstruction error sensitivity function is detector element dependent. 19. A system in accordance with claim 18 wherein the reconstruction error sensitivity varies according to a distance of the detector element from an isocenter element. 20. A system in accordance with claim 17 wherein the detector rows have at least 214 elements on each side of an isochannel element, and the reconstruction error sensitivity function is: EQU w(i)=0.18/b(i); 21. A computed tomography imaging system comprising an x-ray source, a detector array including a plurality of rows of detector elements, and a movable collimator positionable in steps and configured to collimate and position an x-ray beam produced by said x-ray source on said detector array, said system configured to: 22. A system in accordance with claim 21 wherein said system being configured to determine a beam position transfer function comprises the steps of fitting, to a polynomial function, the determined beam positions at each step as a function of the ratio of an average of detector outer row signals to detector inner row signals. 23. A system in accordance with claim 22 wherein the polynomial function is a fourth degree polynomial. 24. A system in accordance with claim 21 further configured to determine a valid measurement range of the transfer function as end limits of the plurality of collimator step positions for which an error between beam positions computed using the transfer function and an actual beam position is less than a predetermined limit. 25. A system in accordance with claim 24 in which the predetermined limit is between 0.1 and 0.6 millimeters. 26. A system in accordance with claim 24 in which the predetermined limit is 0.2 millimeters. |
claims | 1. A top nozzle for a pressurized water nuclear reactor, the top nozzle comprising:a horizontal plate portion having a peripheral portion;a hub portion spaced from the plate portion;a plurality of support portions extending from the plate portion to the hub portion; andat least one deflector portion extending continuously inwardly and upwardly from the peripheral portion at an acute angle with respect to the plate portion,wherein the at least one deflector portion is spaced from each of the hub portion and the plurality of support portions, and is cantilevered from the peripheral portion,wherein the top nozzle is made of a single piece of material, andwherein, when the top nozzle is viewed from a top plan view, the at least one deflector portion is substantially triangular shaped. 2. The top nozzle of claim 1 wherein the peripheral portion comprises a plurality of edge portions; and wherein the at least one deflector portion comprises a plurality of deflector portions each extending from one of the plurality of edge portions. 3. The top nozzle of claim 2 wherein each of the plurality of edge portions has a midpoint; and wherein each of the plurality of deflector portions extends radially inwardly from a corresponding midpoint of a corresponding one of the plurality of edge portions. 4. The top nozzle of claim 2 wherein the peripheral portion further comprises a plurality of corner portions; wherein each of the plurality of support portions extends from a corresponding one of the plurality of corner portions; wherein each of the plurality of edge portions extends between a corresponding pair of the plurality of corner portions; and wherein each of the deflector portions is spaced from each of the plurality of corner portions. 5. The top nozzle of claim 2 wherein the plate portion is hexagonal-shaped; wherein the plurality of edge portions comprises six edge portions; and wherein the plurality of deflector portions comprises six deflector portions each extending from a corresponding one of the six edge portions. 6. The top nozzle of claim 1 wherein the at least one deflector portion has a distal portion disposed opposite and distal the peripheral portion; and wherein the at least one deflector portion continuously narrows from the peripheral portion to the distal portion. 7. The top nozzle of claim 1 wherein the plate portion further has a plurality of ribs disposed internal with respect to the peripheral portion; and wherein the top nozzle further comprises at least one deflector support portion extending from a corresponding one of the plurality of ribs to the at least one deflector portion. 8. The top nozzle of claim 7 wherein the at least one deflector support portion is disposed perpendicular to the corresponding one of the plurality of ribs. 9. The top nozzle of claim 7 wherein the at least one deflector portion has a center line coinciding with the at least one deflector support portion. 10. The top nozzle of claim 7 wherein the at least one deflector portion has a first half portion, a second half portion, and a center line separating the first half portion and the second half portion; wherein the at least one deflector support portion comprises a first deflector support portion and a second, separate deflector support portion; wherein the first deflector support portion extends from the first half portion; and wherein the second deflector support portion extends from the second half portion. 11. A top nozzle for a pressurized water nuclear reactor, the top nozzle comprising:a plate portion having a peripheral portion;a hub portion spaced from the plate portion;a plurality of support portions extending from the plate portion to the hub portion; andat least one deflector portion spaced from the hub portion and extending inwardly from the peripheral portion at an acute angle with respect to the plate portion,wherein the plate portion further has a plurality of ribs disposed internal with respect to the peripheral portion; and wherein the top nozzle further comprises at least one deflector support portion extending from a corresponding one of the plurality of ribs to the at least one deflector portion. 12. The top nozzle of claim 1 wherein the at least one deflector portion comprises a distal portion; and wherein, when viewed from a top plan view, the distal portion is disposed between the peripheral portion and the hub portion. 13. A pressurized water nuclear reactor comprising:a pressure vessel;a plurality of fuel assemblies housed by the pressure vessel, each fuel assembly comprising:a bottom nozzle, anda top nozzle comprising:a horizontal plate portion having a peripheral portion,a hub portion spaced from the plate portion,a plurality of support portions extending from the plate portion to the hub portion, andat least one deflector portion extending continuously inwardly and upwardly from the peripheral portion at an acute angle with respect to the plate portion; anda plurality of fuel rods disposed intermediate the top nozzle and the bottom nozzle,wherein the at least one deflector portion is spaced from each of the hub portion and the plurality of support portions, and is cantilevered from the peripheral portion,wherein the top nozzle is made of a single piece of material, andwherein, when the top nozzle is viewed from a top plan view, the at least one deflector portion is substantially triangular shaped. 14. The pressurized water nuclear reactor of claim 13 wherein the peripheral portion comprises a plurality of corner portions and a plurality of edge portions; wherein each of the plurality of edge portions extends between a corresponding pair of the plurality of corner portions; wherein each of the plurality of edge portions has a midpoint; wherein the at least one deflector portion comprises a plurality of deflector portions each extending radially inwardly from a corresponding midpoint of a corresponding one of the plurality of edge portions; wherein each of the plurality of support portions extends from a corresponding one of the plurality of corner portions; and wherein each of the plurality of deflector portions is spaced from each of the plurality of corner portions. 15. The pressurized water nuclear reactor of claim 13 wherein the plate portion is hexagonal-shaped; wherein the peripheral portion comprises six edge portions; and wherein the at least one deflector portion comprises six deflector portions each extending from a corresponding one of the six edge portions. 16. The pressurized water nuclear reactor of claim 13 wherein the at least one deflector portion comprises a base portion and an extension portion; wherein the base portion extends inwardly from the peripheral portion at the acute angle; and wherein the extension portion extends inwardly from the base portion at a second angle between 150 degrees and 170 degrees with respect to the base portion. 17. The pressurized water nuclear reactor of claim 13 wherein the at least one deflector portion has a distal portion disposed opposite and distal the peripheral portion; and wherein the at least one deflector portion narrows from the peripheral portion to the distal portion. 18. The top nozzle of claim 11 wherein the at least one deflector portion comprises a first deflector portion, a second deflector portion disposed opposite and distal the first deflector portion, a third deflector portion, a fourth deflector portion disposed opposite and distal the third deflector portion, a fifth deflector portion, and a sixth deflector portion disposed opposite and distal the fifth deflector portion; wherein the first deflector portion and the second deflector portion each have a center line; wherein the third deflector portion, the fourth deflector portion, the fifth deflector portion, and the sixth deflector portion each have a first half portion, a second half portion, and a center line separating the first half portion and the second half portion; wherein the at least one deflector support portion comprises ten additional support portions; wherein two of the ten deflector support portions each coincide with a corresponding center line of a corresponding one of the first deflector portion and the second deflector portion; wherein four of the deflector support portions each extend from a corresponding first half portion of a corresponding one of the third deflector portion, the fourth deflector portion, the fifth deflector portion, and the sixth deflector portion; and wherein another four of the deflector support portions each extend from a corresponding second half portion of a corresponding one of the third deflector portion, the fourth deflector portion, the fifth deflector portion, and the sixth deflector portion. 19. The top nozzle of claim 11 wherein the at least one deflector portion comprises a first deflector portion having a first half portion, a second half portion, and a center line separating the first half portion and the second half portion; and wherein the at least one deflector support portion comprises a first deflector support portion extending from the first half portion and a second deflector support portion extending from the second half portion. 20. The top nozzle of claim 11 wherein the at least one deflector portion comprises a first deflector portion having a center line; and wherein the at least one deflector support portion comprises a first deflector support portion coinciding with the center line. |
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046719229 | abstract | The invention relates to a nuclear reactor cooled by a liquid metal comprising a vessel (12) containing the reactor core (24), a vessel shaft (18) and a sealing slab (14).. The bottom (12a) of the vessel rests on the bottom (52) of the vessel shaft via supports (54) defining between the said two bottoms a space (56) in which circulates a cooling fluid such as air. A skirt (74) surrounds vessel (12) and rests on the vessel shaft bottom (52) for supporting slab (14).. Application to the construction of simpler and less expensive fast neutron reactors than those hitherto known. |
050013548 | description | DESCRIPTION OF SPECIFIC EMBODIMENTS In accordance with the present invention, it has been found that particles having a high specific gravity can be maintained substantially uniformly in suspension in a natural rubber latex free of air bubbles in order to afford the production of radiation resistant surgical gloves therefrom free of pin holes. The gloves are formed from one or a multiplicity of layers comprising dried natural rubber latex wherein at least one of the layers includes high specific gravity particles uniformly distributed therethrough. As used herein, the term "high specific gravity particles" refers to metal or metal compound particles having a specific gravity of at least 11.0. Representative suitable high specific gravity particles include tungsten, tantalum, tungsten carbide, tungsten oxide, or mixtures thereof. The high specific gravity particles have an average size of less than about 5 microns and preferably less than about 1 micron. A suspension of the high specific gravity particles in the natural rubber latex is produced by agitating a mixture of the particles and the latex under conditions to prevent the particles from precipitating to the bottom of the mixture while avoiding entrapment of air within the latex-particle mixture. Referring to FIG. 1, in one embodiment of the present invention, the natural rubber latex and high specific gravity particles are added to a container 10 having a top 12 which floats on top of the latex-particle mixture. The top 12 has hinges 14 so that top section 16 can be opened by means of handle 18 in order to permit dipping of a glove form (not shown) into the latex-particle suspension immediately after ceasing agitation thereby to prevent air entrapment. After dipping, the hinged top section 16 is closed and agitation is resumed. The top 12 is provided with a hole 20 through which an agitator 21 can be extended to effect the agitation of the suspension. A suitable agitator can comprise a rod having attached at one end a propellor which is located at or near the bottom of the container 10. The rate of agitation of the agitator is controlled so that cavitation of the top surface of the suspension is not effected. By causing the top 12 to float on top of the suspension, the possibility of cavitation of the suspension at the top surface is vastly reduced or eliminated. Thus, in this manner, the particles can be retained in suspension substantially uniformly within the natural rubber latex while avoiding entrapment of air within the suspension. Entrapment of air within the suspension is to be avoided since rubber gloves produced therefrom will have pin holes or larger holes upon curing due to the presence of air. Referring to FIG. 2, an alternative embodiment is shown for effecting agitation of the suspension while avoiding entrapment of air. A container 22 is provided having an open top 24 so that the top surface 26 of the latex-particle suspension is exposed to the atmosphere. The container 22 has a conical shaped bottom having walls 28 positioned at an angle to the vertical axis of the container between about 15.degree. and about 45.degree. , preferably between about 30.degree. and about 20.degree. . The walls 28 extend to a bottom opening 32 which is connected to a conduit 34 and a low shear pump 36. The suspension is recirculated through a conduit 38 to a point between about 1/2 and about 2 inches below the top surface 26. A screen or filter 39 optionally can be positioned at the end of conduit 38. The pump 36 is a low shear pump which prevents coalescence of the latex caused by shearing forces on the latex. Representative suitable low shear pumps are peristaltic pumps, diaphragm pumps or double diaphragm pumps. The pump rate is higher than the free fall particle rate in the latex. This free fall particle rate can be easily determined by measuring the drop rate of the particles in the latex in a separate container prior to forming the desired suspension. However, the pump rate must not be so high as to entrap air bubbles in the suspension. The actual pump rate will vary depending upon the type of natural rubber latex utilized, the specific particles utilized and the sixe of the container. Generally, the pump rates will vary between about 0.5 gallons per minute and 3 gallons per minute, for one-form dipping vats, usually between about 0.7 and 1.5 gallons per minute. The latex particle suspension is reintroduced into container 22 from conduit 38 in a direction essentially parallel to the plane of the top surface of the suspension in container 22. In addition, the suspension is introduced into container 22 at an angle relative to the inner surface on container 22 so that direct impingment on the inner surface is avoided. That is, the angle relative to the inner surface at which the suspension is initially introduced from conduit 38 and nozzle 41 should be as parallel to the inner surface as possible. When using either embodiment shown in FIG. 1 or in FIG. 2, make up suspension is periodically added to the container in order to prevent entrapment of air during mixing. The latex-particle suspension is formed from natural rubber particles in a liquid suspending medium, typically water. The high specific gravity particles comprise between about 3 and about 20 volume percent, preferably between 5 and 10 volume percent based upon the volume of the latex-particle suspension. The latex also can include conventional dispersing agents such as sulphonated naphthalene or stabilizing agents such as polyethylene oxide condensation products. When forming gloves, a conventional glove form having the general shape of a human hand is dipped into the latex-suspension which is then allowed to dry on the form thereby to form a continuous glove layer on the glove form. The latex may be utilized in conjunction with a conventional latex coagulant such as calcium nitrate in a mixture of water and ethanol. The glove can be formed by any one of a plurality of dipping steps. In one procedure, a glove form is first dipped into pure natural rubber latex without filler, removed therefrom and dried to a hazy appearance. Thereafter, the glove form is dipped into the latex-high specific gravity particle suspension, removed therefrom and dried as set forth above. Lastly, the glove form is dipped into the pure natural rubber latex free of filler, and then is oven-cured at about 170.degree. F. to 210.degree. F. for about 30 to 60 minutes. FIG. 3 is a side view showing a glove 100 formed in accordance with the present invention. FIG. 4 is a schematic sectional view showing the cross-section of the glove 100, the glove having inner and outer latex layers without high specific gravity particles, and a middle latex layer containing high specific gravity particles. It is to be appreciated that FIG. 4 is schematic in nature, and is not intended to suggest either relative layer thicknesses or relative particle size. In a second procedure, the glove form is dipped into the coagulant solution, dried for about 2 to 5 minutes and then dipped into the latex-high specific gravity particle suspension and dried for about 2 to 5 minutes. Thereafter, the glove is leached in hot water for about 30-60 minutes to wash away excess coagulant and then is oven-cured at about 170.degree. F. to 210.degree. F. for about 30 to 60 minutes. It is preferred that the coagulant utilized herein include water as the solvent. It has been found that water generally evaporates at a slower rate than hydrocarbon suspending agent normally employed. When the gloves are dried with the fingers and thumb up and water is utilized as the suspending agent, there is some migration of coagulant away from the tips of the finger and thumb on the glove form which results in these areas being thinner than the remaining areas of the glove. This further results in improved tactile sense for the user in the working areas of the hand while at the same time providing the desired protection against radiation. The gloves of this invention generally have a thickness of between about 6 and about 20 thousandths of an inch, preferably between about 10 and about 15 thousandths of an inch. These gloves provide improved protection and retain the tactile sense necessary in surgical procedures. The gloves of this invention are capable of absorbing generally between about 50 and about 80 percent of incident radiation as compared with the currently available lead oxide-polyurethane glove which absorbs only between about 10 and about 30 percent of incident radiation of between about 60 to 100 KVP. The following examples illustrate the present invention and are not intended to limit the same. EXAMPLE 1 Using the apparatus as shown in FIG. 1, a double impeller two inch blade was utilized at 1200 rpm. The blade was positioned immediately adjacent the bottom inner surface of the container. Tungsten particles (17.5 lb.) having an average particle size of 0.8 microns were mixed in a container with 1850 ml water containing 0.9 wt. percent sulfonated naphthalene, Rohm and Haas (Tamol 731) based on solids for about 30 minutes in order to coat the particles with the Tamol dispersing agent and to form a creamy, homogeneous dispersion. The dispersion was added to a natural rubber latex in the container shown in FIG. 1. The latex comprised 55 vol.% solids and the final mixture comprised 13 vol.% tungsten particles. Agitation was initiated and maintained until a uniform, air-free latex-particle suspension was formed. Immediately after agitation was stopped, the container lid was opened and a glove form was dipped into the latex-particles suspension for 20-30 seconds. The forms were removed slowly to form a thin latex layer on the forms. The container lid was then closed and agitation was resumed. The form was then inverted back and forth for 5 minutes to cause the latex to gel. The form was then inserted into a coagulant comprising 30% calcium nitrate in 90 vol. % water and 10 vol. %ethanol for 30 seconds. After inverting the form for 5 minutes the form was again dipped in the latex-particle suspension after agitation was stopped. The form was again removed slowly, the lid closed and agitation restarted. Thereafter the latex gloves on the forms were dipped in hot water for 45 minutes to wash out any water washable compositions in the gloves. The gloves were then oven cured for 30 minutes at 190.degree. F. The gloves were free of pinholes and absorbed 65% of incident radiation at 60 KVP. EXAMPLE 2 Using the apparatus shown in FIG. 2, the included angle between the conical walls 28 was 60.degree. and the hole 32 had a 3/4 inch diameter. A peristaltic pump was used at a recirculation rate of 0.9 gallons per minute. The tube 38 had an inside diameter of 1/2 inch. The nozzle 41 had a 45.degree. elbow and was positioned to flow effluent therefrom substantially parallel to the plane of the top surface of the latex suspension in the container 22. Tungsten particles having an average particle size of 0.8 microns were mixed in a container with 0.2% Rohm and Haas sulfonated naphthalene (Tamol 731) in distilled water for about 60 minutes in order to coat the particles with dispersing agent. The homogenous dispersion created was added to a natural rubber latex in the container shown in FIG. 2. The latex comprised 60 vol. % solids and the final mixture comprised 10 vol. % tungsten particles. Pumping was initiated and maintained until a uniform, air-free latex-particle suspension was formed. A glove form was dipped into a 27% aqueous solution of calcium nitrate and then dried inverted for 10 minutes. While pumping, a glove form was dipped into the latex-particle suspension for 20 seconds. The form was removed slowly to form a thin latex layer on the form. The form was then inverted back and forth for 5 minutes to cause the latex to gel. Thereafter the latex glove on the form was dipped in hot water for 45 minutes to wash out water washable compositions in the glove. The glove was then oven cured for 30 minutes at 190.degree. F. The glove was free of pinholes and absorbed 70% of incident radiation at 70 KVP. |
claims | 1. A nail lamp comprising:an upper housing, wherein the upper housing comprises at least a portion having a translucent material;a lower housing, coupled to the upper housing, wherein an enclosed space is between the upper and lower housings;a display panel, wherein the display is capable of displaying at least two digits;a first printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to a plurality of buttons, accessible from an exterior of the nail lamp, and the display, andby way of the buttons, a user can select a curing time, which will be displayed on the display panel;a second printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board, andlight emitted by the interior-illuminating light emitting diodes is directed through apertures formed in the lower housing into a treatment chamber of the nail lamp;a plurality of exterior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp;a battery compartment formed by the lower housing, wherein the battery compartment is sized to hold a rechargeable battery pack, the battery compartment comprises a slot opening at an end of the battery compartment, and the slot opening is accessible from a bottom side of the nail lamp;the rechargeable battery pack, contained within the battery compartment, wherein the rechargeable battery pack is coupled to the first printed circuit board, and the rechargeable battery pack is removable from the battery compartment through the slot opening without decoupling the lower housing from the upper housing; andan exterior power connector, coupled to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes, and to recharge the rechargeable battery pack, andwhen power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes are powered by the rechargeable battery pack. 2. The nail lamp of claim 1 comprising:detection sensors, coupled to the control circuit, wherein after the user has selected a curing time, the hand detection sensors detect the presence of a hand in the treatment chamber and cause the control circuit to turn on the interior-illuminating light emitting diodes, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber. 3. The nail lamp of claim 2 wherein when the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the hand detection sensors detect the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed. 4. The nail lamp of claim 1 comprising:detection sensors, coupled to the control circuit, wherein after the user has selected a curing time, the selected curing time is displayed on the display panel, the hand detection sensors detect the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes,while the interior-illuminating light emitting diodes are on, the display panel shows a time remaining for the interior-illuminating light emitting diodes to be on, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber. 5. The nail lamp of claim 1 wherein by way of the buttons, the user can select a predetermined curing time of 15 seconds, 30 seconds, or 60 seconds. 6. The nail lamp of claim 1 wherein the buttons comprise at least three buttons. 7. The nail lamp of claim 1 wherein while the interior-illuminating light emitting diodes are on, emitting ultraviolet light, the exterior-illuminating light emitting diodes are on, emitting visible, non-ultraviolet light. 8. The nail lamp of claim 1 wherein the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is opposite of the second direction. 9. The nail lamp of claim 1 wherein the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber. 10. The nail lamp of claim 1 wherein each of the interior-illuminating light emitting diodes is in a recessed opening of the lower housing. 11. The nail lamp of claim 1 wherein the interior-illuminating light emitting diodes comprise 1-watt light emitting diodes. 12. The nail lamp of claim 1 wherein the interior-illuminating light emitting diodes comprise a combination of 1-watt and 2-watt light emitting diodes. 13. The nail lamp of claim 1 wherein the exterior-illuminating light emitting diodes emit light having a different wavelength range from the interior-illuminating light emitting diodes. 14. The nail lamp of claim 1 wherein the interior-illuminating light emitting diodes emit ultraviolet light in a range from about 340 nanometers to about 410 nanometers, while the exterior-illuminating light emitting diodes do not emit ultraviolet light. 15. A nail lamp comprising:an upper housing, wherein the upper housing comprises at least a portion having a translucent material;a lower housing, coupled to the upper housing, wherein an enclosed space is between the upper and lower housings;a display panel, wherein the display is capable of displaying at least two digits;a first printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to a plurality of buttons, accessible from an exterior of the nail lamp, and the display, andby way of the buttons, a user can select a curing time, which will be displayed on the display panel;a second printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board, andlight emitted by the interior-illuminating light emitting diodes is directed through apertures formed in the lower housing into a treatment chamber of the nail lamp;a plurality of exterior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp,the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber, andwhen on, the interior-illuminating light emitting diodes emit ultraviolet light, and when on, the exterior-illuminating light emitting diodes emit non-ultraviolet light;detection sensors, coupled to the control circuit, wherein after the user has selected a curing time, the selected curing time is displayed on the display panel, the hand detection sensors detect the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes,while the interior-illuminating light emitting diodes are on, the display panel shows a time remaining for the interior-illuminating light emitting diodes to be on, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber;a battery compartment formed by the lower housing, wherein the battery compartment is sized to hold a rechargeable battery pack, the battery compartment comprises a slot opening at an end of the battery compartment, and the slot opening is accessible from the exterior of the nail lamp;the rechargeable battery pack, contained within the battery compartment, wherein the rechargeable battery pack is coupled to the first printed circuit board, and the rechargeable battery pack is removable from the battery compartment through the slot opening without decoupling the lower housing from the upper housing; andan exterior power connector, coupled to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes, and to recharge the rechargeable battery pack, andwhen power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes are powered by the rechargeable battery pack. 16. The nail lamp of claim 15 wherein the interior-illuminating light emitting diodes comprise 1-watt light emitting diodes. 17. The nail lamp of claim 15 wherein the interior-illuminating light emitting diodes are in recessed openings of the lower housing. 18. The nail lamp of claim 15 wherein the curing time selected by the user can be a predetermined curing time of 15 seconds, 30 seconds, or 60 seconds. 19. The nail lamp of claim 15 wherein when the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the hand detection sensors detect the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed. 20. A nail lamp comprising:an upper housing;a lower housing, coupled to the upper housing, wherein an enclosed space is between the upper and lower housings;a display panel, wherein the display is capable of displaying at least two digits;a first printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to one or more buttons, accessible from an exterior of the nail lamp, and the display, andby way of the one or more buttons, a user can select a curing time, which will be displayed on the display panel;a second printed circuit board, coupled to the lower housing and positioned in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board,light emitted by the interior-illuminating light emitting diodes is directed through apertures formed in the lower housing into a treatment chamber of the nail lamp, andwhen on, the interior-illuminating light emitting diodes emit ultraviolet light;detection sensors, coupled to the control circuit, wherein after the user has selected a curing time, the selected curing time is displayed on the display panel, the hand detection sensors detect the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes,while the interior-illuminating light emitting diodes are on, the display panel shows a time remaining for the interior-illuminating light emitting diodes to be on, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber;a battery compartment formed by the lower housing, wherein the battery compartment is sized to hold a rechargeable battery pack, the battery compartment comprises a slot opening at an end of the battery compartment, and the slot opening is accessible from the exterior of the nail lamp;the rechargeable battery pack, contained within the battery compartment, wherein the rechargeable battery pack is coupled to the first printed circuit board, and the rechargeable battery pack is removable from the battery compartment through the slot opening without decoupling the lower housing from the upper housing; andan exterior power connector, coupled to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board and interior-illuminating light emitting diodes, and to recharge the rechargeable battery pack, andwhen power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board and interior-illuminating light emitting diodes are powered by the rechargeable battery pack. 21. The nail lamp of claim 20 wherein the upper housing comprises at least a portion having a translucent material, and the nail lamp comprises:a plurality of exterior-illuminating light emitting diodes, coupled to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp,when on, the exterior-illuminating light emitting diodes emit non-ultraviolet lightthe interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber. 22. The nail lamp of claim 20 wherein the curing time selected by the user can be a predetermined curing time of 15 seconds, 30 seconds, or 60 seconds. 23. The nail lamp of claim 20 wherein the buttons comprise at least three buttons. 24. The nail lamp of claim 20 wherein the interior-illuminating light emitting diodes are in recessed openings of the lower housing. 25. The nail lamp of claim 20 wherein the interior-illuminating light emitting diodes comprise at least one 1-watt light emitting diode. 26. The nail lamp of claim 20 wherein the interior-illuminating light emitting diodes emit ultraviolet light in a range from about 340 nanometers to about 410 nanometers. 27. The nail lamp of claim 20 wherein when the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the hand detection sensors detect the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed. |
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054066026 | summary | FIELD OF THE INVENTION The present invention relates generally to liquid metal-cooled nuclear reactors and to air cooling thereof. In particular, the invention relates to the passive removal of reactor decay and sensible heat from a liquid metal reactor and the transport of the heat to a heat sink (i.e., atmospheric air) by the inherent heat transfer processes of conduction, radiation, convection and natural convection of fluids. BACKGROUND OF THE INVENTION In the Advanced Liquid Metal Reactors (ALMR), a reactor core of fissionable fuel is submerged in a hot liquid metal, such as liquid sodium, within a reactor vessel. The liquid metal is used for cooling the reactor core, with the heat absorbed thereby being used to produce power in a conventional manner. A known version of an ALMR plant (shown in FIG. 1) has a concrete silo 8 which is annular or circular. The silo is preferably disposed underground and contains concentrically therein an annular containment vessel 2 in which is concentrically disposed a reactor vessel 1 having a nuclear reactor core 12 submerged in a liquid metal coolant such as liquid sodium. The annular space between the reactor and containment vessels is filled with an inert gas such as argon. The reactor and containment vessels are supported or suspended vertically downward from an upper frame 16, which in turn is supported on the concrete silo 8 by a plurality of conventional seismic isolators 18 to maintain the structural integrity of the containment and reactor vessels during earthquakes and allow uncoupled movement between those vessels and the surrounding silo. Operation of the reactor is controlled by neutron-absorbing control rods 15 which are selectively inserted into or withdrawn from the reactor core. During operation of the reactor, it may be necessary to shut down the fission reaction of the fuel for the purpose of responding to an emergency condition or performing routine maintenance. The reactor is shut down by inserting the control rods into the core of fissionable fuel to deprive the fuel of the needed fission-producing neutrons. However, residual decay heat continues to be generated from the core for a certain time. This heat must be dissipated from the shut-down reactor. The heat capacity of the liquid metal coolant and adjacent reactor structure aid in dissipating the residual heat. For instance, heat is transferred by thermal radiation from the reactor vessel to the containment vessel. As a result, the containment vessel experiences an increase in temperature. Heat from the containment vessel will also radiate outwardly toward a concrete silo spaced outwardly therefrom. These structures may not be able to withstand prolonged high temperatures. For example, the concrete making up the walls of the typical silo may splay and crack when subjected to high temperatures. To prevent excessive heating of these components, a system for heat removal is provided. One of the heat removal systems incorporated in the ALMR is entirely passive and operates continuously by the inherent processes of natural convection in fluids, conduction, convection, and thermal radiation. This safety-related system, referred to as the reactor vessel auxiliary cooling system (RVACS), is shown schematically in FIG. 1. Heat is transported from the reactor core to the reactor vessel 1 by natural convection of liquid sodium. The heat is then conducted through the reactor vessel wall. Heat transfer from the reactor vessel outside surface to the colder containment vessel 2 across the argon-filled gap 3 is almost entirely by thermal radiation. An imperforate heat collector cylinder 5 is disposed concentrically between the containment vessel 2 and the silo 8 to define a hot air riser 4 between the containment vessel and the inner surface of the heat collector cylinder, and a cold air downcomer 7 between the silo and the outer surface of the heat collector cylinder. Heat is transferred from the containment vessel 2 to the air in the hot air riser 4. The inner surface of heat collector cylinder 5 receives thermal radiation from the containment vessel, with the heat therefrom being transferred by natural convection into the rising air for upward flow to remove the heat via air outlets 9. Heat transfer from the containment vessel outer surface is approximately 50% by natural convection to the naturally convecting air in the hot air riser 4 and 50% by radiation to the heat collector cylinder 5. Heating of the air in the riser 4 by the two surrounding hot steel surfaces induces natural air draft in the system with atmospheric air entering through four air inlets 6 above ground level. The air is ducted to the cold air downcomer 7, then to the bottom of the concrete silo 8, where it turns and enters the hot air riser 4. The hot air is ducted to the four air outlets 9 above ground level. The outer surface of heat collector cylinder 5 is covered with thermal insulation 5a (see FIG. 2) to reduce transfer of heat from heat collector cylinder 5 into silo 8 and into the air flowing downward in cold air downcomer 7. The greater the differential in temperature between the relatively cold downcomer air and the relatively hot air within the riser, the greater will be the degree of natural circulation for driving the air cooling passively, e.g., without motor-driven pumps. The above description applies to normal reactor operation and shutdown heat removal when the sodium within the reactor vessel is at its normal level 10. In accordance with the foregoing ALMR concept, the reactor vessel and its closure function as the primary coolant boundary. A steel dome located above the reactor closure functions as the primary containment above the closure elevation. Below the reactor closure elevation, the containment vessel functions both as a guard vessel (for leak protection) and as the containment. The ALMR containment has been shown to be effective against all design basis events and most beyond design basis (BDB) events and is considered to meet and exceed present U.S. licensing requirements. However, it is possible for significant radiological releases to occur under a postulated BDB event in which both the reactor and containment vessels fail. If leaks should develop in both the reactor vessel 1 and the containment vessel 2, the sodium level may drop as low as the double vessel leak level 11 (see FIG. 1). Under such conditions, atmospheric air can come in direct contact with radioactive sodium. Thus, there is the potential for major sodium fires and the escape of radioactive products directly to the atmosphere through the RVACS air inlet and outlet ducts. In addition, the RVACS will be rendered inoperative. This loss of cooling capability would result in heat-up and a slow (five-day) sodium boil-off followed by a core melt-through, which in turn would be followed by a more severe radiological release. These are the major disadvantages with the known ALMR concept. SUMMARY OF THE INVENTION The present invention is an improvement which seeks to eliminate the aforementioned disadvantages of the prior art passive air cooling system while retaining the basic ALMR configuration. The invention utilizes a novel passive and inherent shutdown heat removal method with a backup air flow path which allows decay heat removal following a postulated double vessel leak event. The improved reactor design incorporates the following features: (1) isolation capability of the reactor cavity environment in the event that simultaneous leaks develop in both the reactor and containment vessels; (2) a reactor silo liner tank which insulates the concrete silo from the leaked sodium, thereby preserving the silo's structural integrity; and (3) a second, independent air cooling flow path via tubes submerged in the leaked sodium which will maintain shutdown heat removal after the normal flow path has been isolated. This disclosure describes a modified passive cooling concept in which the simplicity and reliability advantages of passive cooling are combined with the capability for isolating the reactor cavity environment from the outside air environment should a double vessel leak occur, while maintaining passive air cooling. Thus, this concept provides an additional level of defense against the extremely low probability event described above. The main advantage of the invention is that it allows use of the highly reliable redundant passive shutdown cooling system in combination with closable and more conventional containments. Such a design approach is expected to have reduced public risk as compared to the current ALMR design because in addition to the highly reliable active and passive "protective" systems, additional severe accident mitigating capability is provided for BDB events such as the postulated double vessel leak event. |
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