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	abstract	A nuclear reactor in one embodiment includes a cylindrical body having an internal cavity, a nuclear fuel core, and a shroud disposed in the cavity. The shroud comprises an inner shell, an outer shell, and a plurality of intermediate shells disposed between the inner and outer shells. Pluralities of annular cavities are formed between the inner and outer shells which are filled with primary coolant such as demineralized water. The coolant-filled annular cavities may be sealed at the top and bottom and provide an insulating effect to the shroud. In one embodiment, the shroud may comprise a plurality of vertically-stacked self-supported shroud segments which are coupled together.
051907216	claims	1. A corrosion resistant alloy for the inner barrier liner in nuclear fuel cladding consisting essentially of; in weight percent, about 0.1 to less than 0.5 percent bismuth, about 0.1 to less than 0.5 percent niobium, and the balance substantially zirconium, the alloy having ductility and hardness comparable to sponge zirconium. 2. A corrosion resistant alloy according to claim 1 having a Vickers hardness of less than about 155 KHN. 3. A corrosion resistant alloy according to claim 1 wherein niobium is about 0.1 to 0.3 weight percent. 4. A corrosion resistant alloy according to claim 1 wherein niobium is about 0.1 to 0.2 weight percent. 5. A nuclear fuel cladding comprising an outer tube of a Zircaloy alloy, and an inner liner of an alloy consisting essentially of, in weight percent, about 0.1 to less than 0.5 percent bismuth, about 0.1 to less than 0.5 percent niobium, and the balance substantially zirconium, the liner alloy having ductility and hardness comparable to sponge zirconium. 6. A nuclear fuel cladding according to claim 5 wherein the liner alloy has a Vickers hardness of less than about 155 KHN. 7. A nuclear fuel cladding according to claim 5 wherein the niobium is about 0.1 to 0.3 weight percent. 8. A nuclear fuel cladding according to claim 5 wherein the niobium is about 0.1 to 0.2 weight percent.
	description	The present invention relates to radiographic cameras. More specifically, the present invention relates to a jacket, an attachment for a radiation shield, and a connector assembly, all for a radiographic camera. A radiographic camera 100, according to the illustrated embodiment as shown in FIGS. 1-5, has a housing 102 with openings at a front end 104 and a back end 106 where a guide cable (not shown) and control cables (not shown), respectively, may be coupled. The housing 102 has a cylindrical shape (see FIGS. 3-5) forming a cylindrical tube; however, the housing could be any shape so long as it could contain suitable camera components. A lock assembly 108 is provided at the opening in the back end 106. A connector assembly 110 is provided at the opening in the front end 104. A radiation source 112 is mounted at the end of a source cable 114, which is in a conduit 116. As shown, the conduit 116 is S-shaped, although the conduit 116 could be made in any suitable shape. The conduit 116 is enclosed inside the housing 102 and is in communication with the lock assembly 108 and the connector assembly 110. The source 112 is inside the housing 102 when the camera 100 is in a stored condition. When the camera 100 is to be used, the control cables and guide cable are attached to the lock assembly 108 and the connector assembly 110, respectively. The control cable has a wire (not shown) which pushes the source 112 from the camera oil l housing 102 into the guide cable, e.g., when a technician operates a crank at the end of the control cables. The source 112 is pushed until it reaches the end of the guide cable. The end of the guide cable is placed suitably near an object with photographic film cassettes (not shown) positioned on the other side of the object. After an exposure time has lapsed, the source 112 is withdrawn from the guide cable into the conduit 116 in the housing 102. A jacket 118 may be provided with the radiographic camera 100 as shown in FIGS. 1 and 2. The jacket 118 may provide for easy transportation of the radiographic camera 100, and a protective cover for the radiographic camera 100. Radiographic cameras 100 can weigh over thirty pounds, thus it can be advantageous to have a jacket 118 to allow for easy carrying of the device. The jacket 118 may be removable from the housing 102 of the radiographic camera 100, such that the camera 100 can be used without the jacket 118 if the camera 100 needs to be placed within a more confined area that will not accommodate the jacket 118 or if the camera 100 is to be used with another device such as a remote controlled device. The housing 102 may be slid within the jacket 118 and the jacket 118 removably secured to the housing 102 using rivets or screws (not shown). The jacket 118 is made of molded polyurethane, although the jacket 118 could be made of any suitable material or combination of materials including plastics and metals. Referring to FIGS. 6-9, another embodiment of the jacket 118 features a first end 120, a second end 122 opposite the first end 120 forming a body 124 of the jacket 118 and a handle 126 positioned between the ends 120 and 122. An opening 128 is formed by the jacket 118 from the first end 120 through the second end 122 to accommodate the radiographic camera 100. It will be understood that the first and second ends 120 and 122 of the jacket 118 may not be connected except at the handle 126. As shown, in the illustrated embodiment of the invention, the opening 128 is cylindrical to accommodate the cylindrical housing 102 of the camera 100, and the handle 126 is located above the body 124 of the jacket 118 connecting the first and second ends 120 and 122. The opening 128 can be any desired shape to accommodate any shaped housing 102, such as a square or rectangular shape. The handle 126 can be provided anywhere on the body 124, and may be any convenient shape for transporting the camera 100. FIGS. 1 and 6-9 show a partial opening 130 defined between the first and second ends 120 and 122 to expose part of the housing 102 for the camera 100. Source identification labels 131 may be included on the housing 102 to show through this partial opening 130 (see FIGS. 3-5). Additionally, a hole 132 may be formed in one end of the jacket 118, as shown in FIG. 6, for accommodating a finger to activate a lock slide 134 (see FIG. 19) on the lock assembly 108. In the illustrated embodiment, as shown in FIG. 9, first and second ends 120 and 122 of the jacket 118, when viewed from the front and back views, may have a first rounded bottom portion 136 or other suitable shape such that the jacket 118 may be set on a pipe having similar radius. Additionally, referring to FIG. 8, from the side views, the jacket 118 may have a second rounded bottom portion 138 or other suitable shape to accommodate pipes having a similar radius. Thus, there may be at least two different orientations for stably locating the jacket 118 on top of different sized pipes. Because the camera 100 may be heavy, a reinforcement structure 140 may be included in the handle 126 of the jacket 118 to support the handle 126, e.g., provide additional strength to the handle 126 and/or provide a safety feature such that if other portions of the handle 126 break, the reinforcement structure 140 may prevent complete failure of the handle 126. For example, if a molded polyurethane portion of the handle 126 breaks while the camera 100 is being carried, the reinforcement structure 140 may provide a back-up support, thus preventing the person carrying the camera 100 from dropping the camera 100. The reinforcement structure 140 may include a wire 142, and an additional protective element 144, such as tubing. As shown in FIGS. 10-13, in the illustrated embodiment of the invention, the wire 142 surrounds the opening at the first end 120 of the jacket 118, extends through the handle 126 and surrounds the opening at the second end 122 of the jacket 118. The wire 142 may provide additional support from under the housing 102. Referring to FIGS. 11, 12 and 13, tubing 144 surrounds the wire 142 contained within the handle 126. The tubing 144 may provide additional strength to the handle 126 and/or provide a larger surface area for the wire, e.g., to prevent the wire 142 from cutting through the jacket 118 or to more comfortably allow a person to carry the weight of the camera 100. The wire 142 may be a continuous loop, or the wire may have two ends 146 and 148. Preferably, the wire 142 is oriented in such a manner that the ends 146 and 148 of the wire 142 are located within the handle 126. Further, as shown in FIG. 13, ferrules 150 may be used to secure the ends 146 and 148 of the wire 142. In the illustrated embodiment, the wire 142 is xe2x85x9 inch preformed stainless steel aircraft cable of 7xc3x9719 construction, the tubing 144 is stainless steel, and the ferrules 150 are copper plated; although wire 142, tubing 144 or ferrules 150 of any construction or material may be used. For example, the reinforcement structure 140 may include a single cast or otherwise formed structure of any suitable material that includes two loops to support either end of the camera 100 and a portion between the loops to act as a handle or support for a handle. It will be understood that the handle 126 may be formed only of the reinforcement structure 140, such as wire 142 and/or tubing 144 without any molded plastic or other structure provided over the wire 142 or tubing 144. Referring now to FIGS. 14-16, a shield 152 of the illustrated embodiment of the radiographic camera 100 is shown attached to first and second endplates 154 and 156. As is known in the art, the shield 152 is depleted uranium, containing an S-shaped titanium conduit 116 cast into the shield 152, where the titanium conduit 116 includes the source 112 provided on an end of a source wire 114. However, the source 112 could be provided within a shield 152 in any suitable manner. As shown in FIGS. 14-16, in the illustrated embodiment the shield 152 is connected to the endplates 154 and 156. By attaching the shield 152 directly to the housing 102, shearing of the conduit 116 may be prevented and a more secure attachment may be provided. The first and second shield ends 158 and 160 are secured to the endplates 154 and 156. Referring to FIG. 17, an endplate is shown. As illustrated, the endplate 154 and 156 is round for accommodation in the opening of the housing. The endplate 154 and 156 features a first and second surface 162 and 164. Four rivnuts 166 may be provided extending from the first surface 162. They are used to mount the lock assembly 108 or connector assembly 110 onto the endplates 154 and 156 with screws 167 (see FIGS. 19 and 21). The screws may be security tamper proof screws that require a special tool to remove. Additionally, the endplates 154 and 156 may be provided with first and second outlets 168 and 170, the first outlet 168 may be used for filling the housing 102 with foam after the shield 152 having the endplates 154 and 156 is inserted into the housing, and the second outlet 170 may be used for insertion of the conduit 116 containing the oil source wire 114. A bracket 172 may be provided on the first surface 162 of the endplate. The bracket 172 is welded to the endplate 154 and 156, although the bracket 172 could be secured to the endplate 152 and 156 by any means, including by an adhesive or by molding or machining the bracket 172 into the endplates 154 and 156. Referring to the illustrated embodiment in FIG. 18, the bracket 172 includes a flat back piece 174 and two parallel extending flanges 176 and 178. The flanges 176 and 178 each have two holes 180, one hole 180 on each flange 176 and 178 is used to secure the shield end 158 and 160 to the bracket. In the illustrated embodiment, the other hole 180 is placed for symmetry in case the bracket 172 is mounted upside down on the endplate 154 and 156, but is not required. Referring to FIGS. 14-16, the first and second shield ends 158 and 160 are attached to the bracket 172 using a pin 182. Cotter pins 184 may be provided in the ends of each pin 182 to additionally secure the shield 152 to the endplate 154 and 156. The endplate 154 and 156 and the bracket 172 are made of stainless steel, although they could be made of any suitable metal or other material. As illustrated, an additional spacer 186 may be provided between the bracket 172 and the shield 152. The spacer 186 is made of copper. The spacer 186 could be made of other suitable metals or other materials, and preferably the spacer 186 is not made of steel. The spacer 186 may assist in preventing the occurrence of a possible reaction between the stainless steel and the depleted uranium that could weaken the steel. The reaction typically can occur at higher temperatures. Although brackets 172 are used in the illustrative embodiment to attach the shield ends 158 and 160 may be attached to the endplates 154 and 156 using any suitable structure(s), such as a ring-shaped collar that is attached to the endplates 154 and 156 and into which the shield ends 158 and 160 are inserted and secured, and so on. Once the endplates 154 and 156 are attached to the shield 152, then the shield assembly 188 can be inserted within the housing 102 as illustrated in FIGS. 1-5. The construction of the shield assembly 188 may give the shield assembly 188 some flexibility, which assists in inserting the shield assembly 188 into the housing 102. The endplates 154 and 156 may be secured to the housing 102 by welding around their periphery or any other suitable manner. As in the embodiment illustrated in FIG. 2, after the endplates 154 and 156 are welded to the housing 102, an expandable foam 190 is inserted into the first outlets 168 in the endplates 154 and 156 to fill at least some of the remaining space inside the housing 102, after which the first outlets 168 are then sealed. The foam 190 may be a polyurethane foam or any other suitable material. The locking assembly 108 provided on the second endplate 156 is similar to the locking assembly described in U.S. Pat. No. 5,065,033 with differences that are discussed below. Referring to the illustrated embodiment in FIG. 19, a lock mount 192 is provided above the lock cover 194 that has two holes 196 and 198. The holes 196 and 198 are provided to accommodate pins (not shown) of a cap 200 on the lock cover 194. When the cap 200 is removed, the cap 200 can be stored safely and out of the way by inserting the pins of the cap 200 into the holes 196 and 198 of the lock mount 192. The holes 196 and 198 may have rubber sleeves that grip the pins of the cap 200 to additionally secure the cap 200 to the lock mount 192. The lock mount 192 and lock cover 194 are provided on a rear plate 202, and a selector ring 204 with the lock slide 134 are located between the rear plate 202 and the lock cover 194. Additionally, referring to FIG. 19A, the sleeve 206 inside the lock assembly 108 may be made of tungsten to further protect the user from possible radiation exposure from the source 112. Referring to the illustrated embodiment of the invention in FIG. 20, an exploded view of the connector assembly 110 provided on the first endplate 154 of the camera 100 is shown. In this illustrative embodiment of the invention, the connector assembly 110 includes a shield protector that blocks an opening of the camera 100 through which the radiation source may move, e.g., to image an object. The shield protector may be normally locked in place to cover the opening and unlocked so that the shield protector may be moved to unblock the opening. The shield protector may be unlocked for movement by activation of a key associated with a guide cable that is attached to the connector assembly 110. For example, a fitting that is attached to an end of the guide cable may act as a key so that when the fitting is engaged with the connector assembly 110, the shield protector is unlocked for movement. Thus, in this illustrative embodiment, the shield protector may only be unlocked and moved to allow the radiation source to move into the guide cable when the guide cable is attached to the connector assembly 110. This may provide a safety feature whereby radiation from a source in the camera 100 may only be released when a key, e.g., a key associated with guide cable, is activated. Although in this illustrative embodiment, the guide cable fitting acts as a key, other elements attached to the guide cable or otherwise associated with the guide cable or other components needed for operation of the camera 100 may act as a key to unlock the shield protector. For example, a key attached by a wire to the guide cable end may be arranged so that the key (which may look and operate like a conventional lock key) may only be used to unlock the shield protector when the guide cable is attached to the connector assembly 10. In this illustrative embodiment, the connector assembly 110 includes a front plate 208 connected to the first endplate 154. Screws 167 may be used to connect the front plate to the endplate, or any other suitable means such as welding. The screws 167 may be tamper proof, such that a special tool is needed to remove the front plate 208 from the endplate 154. The screws 167 are inserted into screw holes 209 in the front plate 208 and the rivnuts 166 on the endplate 154. As shown in FIGS. 22-24, the front plate 208 has an external surface 210 and an internal surface 212. The front plate 208 includes an first opening 214 and a second opening 216. The first opening 214 is aligned with the second outlet or port outlet 170 in the endplate 154. Referring to the embodiment illustrated in FIGS. 20-21A, the external surface 210 may be provided with a knob 218 rotatably mounted on the front plate 208 by a shaft 220 and a roll pin 222. The knob 218 includes a knob hole 224 that receives the shaft 220, as does second opening 216, to rotatably secure the knob 218 to the front plate 208. The knob 218 is rotatably positioned to cover and uncover the first opening 214 in the front plate 208. For example, rotating the knob 21890xc2x0 may fully expose the first opening 214, but not rotate a shield protector and uncover the port outlet 170. According to an illustrative embodiment of the invention, a shield protector 226 selectively blocks and unblocks the port outlet 170 to assist in preventing radiation exposure through the port outlet 170. The first opening 214 is adapted to receive a fitting 254 (see FIGS. 28-30) connected to the guide cable that allows the shield protector 226 to unblock the port outlet 170 and expose the source 112. When the fitting 254 is engaged at the first opening 214, the shield protector 226 is unlocked and may be moved to unblock the port outlet 170. Referring to the illustrated embodiment in FIGS. 20 and 25, on the internal surface 212 of the front plate 208 the shield protector 226 is a rotor 226 that is rotatably secured to the front plate 208. As seen more clearly in FIGS. 25-27, a first rotor hole 228 is provided on the rotor 226 and has a port shield 230 secured within the hole 228. The first rotor hole 228 and port shield 230 may be aligned with the port outlet 170 and the first opening 214 in the front plate 208. Thus, when the first rotor hole 228 is aligned with the port outlet 170, the port shield 230 covers access to the port outlet 170 through the first opening 214 and may help prevent radiation from escaping through the port outlet 170. The port shield 230 is made of tungsten, although any suitable material could be used. The rotor 226 includes a second rotor hole 232 adapted to align with the port outlet 170 upon rotation of the rotor 226. When the second rotor hole 232 is aligned with the port outlet 170, the radiation source may pass through the port outlet 170 into a guide cable. The rotor 226 has a third rotor hole 234 which receives the shaft 220 to rotatably secure the rotor 226 to the front plate 208 using roll pins 236, washers 238, a first compression spring 240, a pivot disk 242, and socket head cap screws 244, and set screw 246 (shown in FIG. 20). The first compression spring 240 is held in place by a roll pin 236 and provides constant tension when the knob 218 is pulled which allows the knob 218 to be turned a first amount, for example 90xc2x0, without turning the rotor 226 to expose the first opening 214. The first compression spring 240 also assists in urging the rotor 226 toward the outside of the connector assembly 110. When the rotor 226 is unlocked, the knob 218 can be rotated an additional amount, for example 50xc2x0, to rotate the rotor 226 and align the second rotor hole 232 with the port outlet 170 and the first opening 214. In the illustrated embodiment, the rotor 226 features a flange 248, upon which rests a slider 250 and a second compression spring 252. The slider 250, which acts as a lock for the rotor 226, may prevent the rotor 226 from rotating. When the slider 250 is moved, the rotor 226 is allowed to rotate and align the second rotor hole 232 with the port outlet 170. A tube fitting 254, as shown in FIGS. 28-30, provided on the guide cable (not shown) may move the slider 250 when the fitting 254 is engaged with the first opening 214. In the illustrated embodiment, the top 256 of the tube fitting 254 can be inserted into the first opening 214 of the front plate 208. The tube fitting 254 may have at least one ear 258, or other suitable feature(s), which, when the tube fitting is rotated, moves the slider 250 to unlock the rotor 226 and to allow the rotor 226 to rotate. The use of a shield protector 226 to uncover the port outlet 170 upon insertion of the tube fitting 254 provides additional protection to the user from radiation exposure. The various locations of the rotor 226 and knob 218 of the illustrated embodiment of the invention are shown in FIGS. 31A-D. For example, in FIG. 31A, the shipping position is shown where the port outlet 170 is covered and shielded by the port shield 230 and the knob 218. FIG. 31B shows the locked position where the knob 218 is lifted and rotated, e.g., 90xc2x0, to expose the first opening 214, but the port outlet 170 is still shielded by the port shield 230 in the first rotor hole 228. Referring to FIG. 31C, the connect position is shown, the tube fitting 254 is inserted into the first opening 214 and rotated to move the slider 250 and unlock the rotor 226. The port outlet 170 is still shielded. FIG. 31D shows the exposed position where the knob 218 is rotated, e.g., 50xc2x0, and turns the rotor 226 such that the second rotor hole 232 is aligned with the port outlet 170, thus exposing the port outlet 170 through the second rotor hole 232 and the first opening 214 in the front plate 208. Although the present invention is described with reference to certain preferred embodiments, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. For example, the connector assembly may be provided without a knob, and another mechanism may be used for rotating the rotor, e.g., engagement of a fitting on the guide cable with the connector assembly and/or operation of another type of key may operate to both unlock and rotate the rotor to expose the port outlet. In addition, the element that blocks and unblocks the port outlet (the rotor 226 in the embodiment described above) need not move in a rotary fashion, but instead may slide linearly or in any other suitable way. A lock may also be provided to prevent disengagement of the guide cable from the camera unless the port outlet is blocked. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.
052672875	claims	1. In a method for fabricating an end fitting for a nuclear fuel assembly, wherein the end fitting includes at least one spring member having an active external surface for contacting rigid core support structure in the nuclear reactor, the improvement comprising: applying a coating to the active surface of said spring member, said coating selected from the group consisting of nitrides, Cr, TiC, CrC, ZrC and NiTaB. 2. The method of claim 1, wherein the spring member is Inconel and the coating is one of ZrN or TiN. 3. The method of claim 1, wherein the coating is applied by vacuum are plasma deposition. 4. The method of claim 1, wherein the coating is one of ZrN or TiN. 5. The method of claim 1, wherein the coating is applied to substantially the entire external surface of said spring member. 6. The method of claim 1, wherein each spring member is formed by nesting a plurality of spring elements so that the spring elements are in contact with each other and the method includes applying said coating to each of the spring elements where they contact each other. 7. A nuclear reactor having a substantially horizontally oriented core support plate and a plurality of substantially vertical nuclear fuel assemblies, each resiliently supported by at least one spring member having a bearing surface projecting from an end fitting on the assembly against the support plate, wherein the improvement comprises said spring members including a metallic coating to lubricate the bearing surface of the spring element against the support plate. 8. The nuclear reactor of claim 7, wherein each spring member includes a plurality of nested spring elements which have contact surfaces that rub against each other as the spring member resiliently bears against the support plate, and each spring member includes a nitride coating at least on said contact surfaces that rub against each other. wherein the metallic coating is a nitride. 9. The nuclear reactor of claim 7, 10. The nuclear reactor of claim 9, wherein the metallic coating is one of ZrN or TiN. 11. The nuclear reactor of claim 9, wherein the metallic coating is selected from the group consisting of CrN, HfN, TiAlVN, TaN and TiCN. 12. The nuclear reactor of claim 7, wherein the coating is selected from the group consisting of Cr, TiC, CrC, ZrC and NiTaB. 13. The nuclear reactor of claim 7, wherein substantially the entire external surface of each spring member is coated. 14. The nuclear reactor of claim 7, wherein the spring member is Inconel and the support plate is stainless steel. 15. The nuclear reactor of claim 8 wherein the spring elements are Inconel and the support plate is stainless steel. 16. In an upper end fitting for a nuclear fuel assembly of the type having upwardly projecting spring members for interacting with a core upper support plate, the improvement comprising said spring members being coated with a lubricity-enhancing material. 17. The end fitting of claim 16, wherein the spring member is Inconel and the coating material is a metal nitride.
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	description	1. Field of the Invention The present invention relates to a new design of an optical head capable of providing a subwavelength beam. 2. Description of the Related Art Optical lithographic technology has been broadly used in various researches due to its convenience since 1665. Besides, since the middle of 20th century, the related applications are deeply extended to various high technology industries, for example, semiconductor and optical storage industries (e.g. CD, DVD etc.) However, owning to the diffraction limit, various optical applications confront with same difficulties when an optical resolution smaller than one wavelength is required. Optical Lithography Under the push of Moore's law of the semiconductor industry, the optical etching linewidth has been shrunk from 5 micrometers in the late 1960 to 90 nanometers nowadays. The optical etching linewidth is still persistently shrunk. Since the visible light optical etching fulfills advantages of high yield and low cost, it is always a primary etch technique in semiconductor processes. Because the dimension of the diffraction limit is equivalent to the wavelength, it is difficult to further shrink the optical etching linewidth when the linewidth reaches up to the order of the wavelength. For the sake of persistently shrinking the etching dimension, the development of short wavelength light sources has become an important field to study. The light source has been varied from 436 nm visible wavelength to 248 nm deep ultraviolet wavelength and till 157 nm nowadays. The light source with the shorter wavelength, even more X-ray range, is still developed. The shrinkage of the exposing wavelength reduces the size of a focusing optical spot. However, the optical elements suitable for the visible light range are not light transmitted in the short wavelength range. Only fused silica and less material are suitable for the ultraviolet range. The flexibility of selection of the optical materials is significantly reduced. Moreover, the refractive index of the above materials in the short wavelength range is not high. It is quite difficult to design an appropriate lens with high numerical aperture and low aberration. The requirement of the accuracy of a phase mask used during exposing is getting stricter because the exposing wavelength becomes shorter. Besides, owing to the property of wave propagation of laser light in free space, the depth of focus and focusing optical spot have the same dimension. As a result, when the focusing optical spot approximates to a sub-micrometer size, the depth of focus would approximate to surface roughness of a general test sample. Therefore, it is necessary to add a fast automatic focusing system to correct the optical path to avoid the defocusing phenomenon that arises an unexpected optical spot, when performing etching. To summarize the foregoing, the optical mechanism becomes more complicated when performing etching as the wavelength shrinks, and the cost is increased more and more. On the other hand, although the current non-optical etching method can provide a higher space resolution, it cannot provide the property of high yield of the optical etching method. To give an example by the electron beam lithographic technique, which utilizes electron beams composed of accelerated electrons to impact the material, resulting in chemical or physical reactions to attain the effect of etching patterns. Since the material wavelength of the electron is far smaller than the wavelength of light, its diffraction limit is smaller and the resolution can attain several nanometers. However, the equipment is very expensive and needs to operate in vacuum, and the yield thereof is also limited. Hence, the equipment is not suitable for being as a parent machine for manufacturing products in large quantities. The non-optical etching method is mostly used in the preparation of original masks. In addition, there is a new lithographic technique as called atomic force microscopy lithography developed in recent years. The atomic force microscopy lithography utilizes a probe of the atomic force microscope to generate electric field to cause an inducing selective chemical reaction, for example etching or deposition. The atomic force microscopy lithography provides a high resolution of ten-nanometer order, but its etching area is too small and the etching speed is too slow. To summarize the foregoing, the optical lithography is still un-replaceable for the manufacturing process with high yield. Optical Storage As a non-contact property of the optical method, the optical storage provides the following advantages: 1. non-destructive by abrasion; 2. long life time; and 3. non-influence by dust when reading. Moreover, the optical storage device has a high optical storage density. The application of the optical storage is widespread. For example, CD (Compact Disc) and DVD (Digital Video Disc) have become indispensable data storage media in modern life. As the rapid advancement of network, multimedia and software, it is a trend to develop a data storage media with a higher capacity and a smaller volume. The present commercialized optical storage devices include CD, DVD and MO (Magnetic Optical device). Since DVD-ROM (Digital Video Disc-Read Only memory) provides a higher capacity and a capability for reading CD-ROM, it has replaced CD-ROM in recent years. Although MO is directed to a storage system with a high capacity and high speed, it cannot become a main stream in the marketing due to its highly cost. The optical storage device usually writes data in a compact disc, and its recording method is through indentations with different lengths between the tracks of the compact disc. The intensity of the light reflected from the indentations is weaker and the intensity of the light reflected from the tracks is stronger. Thus, by way of detecting the intensity of the light reflected from the compact disc to read data recorded therein. The compact discs of CD-ROM (Compact Disc-Read Only Memory) and DVD-ROM (Digital Video Disc-Read Only Memory) are produced in large quantities by copying the data recorded in the mold by pre-pressing. Nevertheless, CD-R and DVD-R utilize a laser source with a short wavelength to break the long chain of dye molecules to change the refractive indexes so as to form low-reflective indentations to write data. Phase change material is applied to CD-RW, DVD-RW and DVD-RAM, and which uses a high-power laser with short pulses to write data, by which the phase change material is rapidly cooled to form an amorphous state, which has a lower reflective index than that of the crystalline state formed by annealing with a long-pulse laser, thus to form indentations. The tracks of the compact disc are formed of a saw-teethed structure having peak and valley portions so as to conveniently write into data along the tracks. Except for the DVD-RAM capable of recording data in both of the peak and valley portions for improving data density, remaining optical storage devices record data in the valley portions. For the optical pickup head, a laser spot is focused unto a surface of the compact disc through an objective, and reflected from the surface of the compact disc to image on a light detector through the objective. The resolution of the optical pickup head is confined by the size of the optical spot. When focusing the light source, the size of the optical spot is mainly relied upon a result gotten by dividing the wavelength λ of the light source by the numerical aperture of the objective. The size of the optical spot on the surface of the compact disc is determined by the multiplication of the thickness d of a substrate of the compact disc and the numerical aperture. Making a comparison, the pitch of the tracks of DVD is 0.74 μm, the shortest length of the indentations of DVD is 0.43 μm, a laser light with λ 650 nm and NA (Numerical Aperture) 0.6 can be used to access the compact disc of DVD; the pitch of the tracks of CD-ROM is 1.6 μm, the shortest length of the indentations of CD-ROM is 0.83 μm, a laser light with λ 780 nm and NA (Numerical Aperture) 0.45 can be used to access the compact disc of CD-ROM. In order to obtain high storage density, it had better have a unit storage area as small as possible. However, due to the diffraction limit, the size of the focusing optical spot of the optical pickup head at the best can approximate to the wavelength of the light source. As a consequence, the unit storage area cannot be further shrunk. It is currently a trend to shrink the wavelength of the light source. There are many difficulties exiting in the technology using a light source with a short wavelength. Meanwhile, the depth of focus become shallower and requirement of stability of the compact disc is improved, resulting in a significant increase of the cost. Optical Imaging and Probing The resolution of the far-field optical measuring system is confined by the principle of the diffraction. Waves with too high space frequency become evanescent waves, and cannot propagate to far field. Thus, the optical spot cannot be focused to a spot less than the wavelength order, and the resolution only can reach up to about the wavelength. Near-field optical microscope is a kind of surface monitoring instrument that can break through the diffraction limit of the conventional optical microscope. The near-field optical microscope generally associates with a voltage actuator or an air bearing to form a system to perform the height-feedback control. Therefore, the optical probe can be accurately controlled over the surface of the sample to be monitored at a height about several to hundreds nanometers. When performing three-dimensional feedback-controllable near-field scanning, surface topography and optical image can be obtained, and the resolution can reach up to about 30 nm to 100 nm. The optical fiber probe is often used as the probe, and the diameter of its tip is between 50 nm and 100 nm. Synge in the United Kingdom in 1928 and O'keefe in the United States in 1956, respectively propose the basic principle of the near-field optical microscope, which utilizes a distance far less than a wavelength to perform optical measurement to break through the diffraction limit. E. A. Ash and G. Nicholls of the UCL university of the United kingdom firstly completes the experimental verification of the near-field optical microscope, which utilizes microwave with a 3 cm wavelength to pass the microscope formed of a probe with a 1.5 mm aperture, and a 0.5 mm resolution is readily obtained. And, a space resolution about 1/60 wavelength can be obtained in the near field. Bell laboratory utilizes optical fiber as a probe by a shear-feedback control method in 1992 to complete a first near-field optical microscope. By way of shrinking the aperture of the probe and the distance between the probe and surface of the object to be monitored to obtain a smaller focusing optical spot and information of evanescent waves unavailable by the far-field optical microscope, thus breaking through the diffraction limit. The near-field optical microscope provides a quite high space resolution in measuring a testing object, providing another definite and practicable method for measuring a micro object. However, there are many limitations existing for the near-field optical microscope: for detecting evanescent waves, an approximating zero working distance between the probe and the surface of the testing object is required, and to obtain the approximating zero working distance, a precise feedback control technology and an expensive air-bearing machine are required. On the other hand, since the light transmittance is too small, it is not easy to obtain a good signal to noise ratio. If the intensity of the incident light is to be increased, the tip of the probe is easily destroyed since the temperature is over high. Extraordinary Transmittance Phenomenon Caused by a Surface Subwavelength Structure Dr. Ebbesen proposed an extraordinary transmittance phenomenon caused by a surface subwavelength structure in Nature in 1998, which cannot be explained by the conventional diffraction phenomenon. The light transmittance measured by experiments is far higher than the result calculated by the micro-hole diffraction theory proposed by Bethe in 1944, and arising many discussions and studies. FIG. 1 shows important parts of a series of studies made by the team of Dr. Ebbesen, in which it is discovered that the light transmittance through the subwavelength hole arrays perforated a metal layer and a underlying substrate is far higher than that calculated by the conventional diffraction theory. A subsequent study indicates that the extraordinary transmittance phenomenon still happens if there is a periodic structure formed on the surface of the metal layer as an auxiliary, and it is not necessary for the hole-arrayed structure to perforate the metal layer and substrate. Besides, it is discovered that a structure of concentric circles with a central perforated hole can improve the light transmittance. Dr. ebbesen et al. publish another important article in August, 2002 that a subwavelength structure is formed on each face of a metal thin layer, and improving the light transmittance and the divergence angle of the transmitting light is far smaller than that predicated by the diffraction theory. For example, in case that groove period=500 nm, groove depth=60 nm, hole diameter=250 nm, film thickness=300 nm, it is discovered that the energy of the light beam (λpeak=660 nm) transmitting the hole-arrayed structure is confined within 3 degree. It shows that the hole-arrayed structure makes the transmitting light beam have directionality, which is totally contrary to the perception of the conventional optics that when the light beam is incident in a hole smaller than the wavelength of the light beam, the transmitting light beam would provide isotropous divergence, i.e. viewing the hole approximating to a point light and the outward propagating waves as spherical waves. The present invention implements the surface subwavelength element to modulate the transmitted optical field so as to provide a subwavelength-scale optical spot, which breaks through the conventional diffraction limit. The material of the surface subwavelength element depends upon the wavelength of the incident light, and is not limited to metal materials. This implementation can be introduced in the optical head of the present various optic architectures to improve various technologies such as optical lithography, optical storage as well as optical imaging and probing. Explanation of Principle Diffraction Limit of Far Field Optics The size of a conventional focusing optical spot is confined by the diffraction limit. In a given wavelength, no matter how to improve performance of an optical system, the focusing optical spot cannot be shrunk to be smaller than a limit, which is proposed by Ernst Abbe in 1884. This limit is based on the principle of diffraction, and called “diffraction limit”. The principle of diffraction is briefly described as follows: spatial optical waves can be decomposed to a combination of plane waves in various directions by the fourier optics method. In a specific wavelength, the space frequencies of the plane waves are the same and the difference among them is merely the directions thereof, which can be represented by the equation (1): k x 2 + k y 2 + k z 2 = k 2 = ( 2 ⁢ ⁢ π λ ) 2 ( 1 ) Wherein, kx, ky and kz respectively are components of space frequency in X, Y and Z axis. Considering a distribution of electric field existing at a plane in the direction of Z=0, if the space frequencies kx, and ky are too high, letkz2=k2−kx2+ky2<0 It is inferred that kz must be an imaginary number, and electromagnetic waves propagate evanescently in Z direction. That is to say, the intensity of the electromagnetic waves is exponentially decayed in Z direction. As a result, the component with the space frequency higher than k cannot propagate toward far field. Hence, one pattern with a space frequency higher than k cannot be produced by way of the far field technology such as lens focusing. In view of space domain, the focusing limit is equivalent to the wavelength, which is the meaning of diffraction limit. Modulation of Optical Field by a Metal Subwavelength Element Dr. Ebbesen publishes a series of literatures beginning in 1998, providing that producing a surface structure nearby one single hole whose size smaller than a subwavelength to modulate the transmitted optical field, the light transmittance of the hole would increase two to three orders in comparison with that without the surface structure formed nearby, as shown in FIG. 2. This phenomenon is related to the ratio of the optical wavelength to the period of the grating structure and the height to width ratio. Meanwhile, the scattering angle of the modulated optical field behind the hole is very smaller, its full width at half maximum (FWHM) is merely within about 3 degrees, totally contrary to the known diffraction phenomenon. With regard to the extraordinary transmittance phenomenon, there is no consensus for its physical mechanism. Basically, there are two explanations for this extraordinary transmittance phenomenon. One utilizes the result of the coupling resonance of the surface plasma waves and light to delivery energy to the other side of the grating; the other utilizes the concept of a waveguide, to explain the optical waves delivery energy in the hole and emit light at one another side. The former explanation is currently accepted by most of people working in this field. Surface plasma wave is an electromagnetic wave occurred at the interface between the metal and dielectric, and the electric field thereof in the metal and dielectric region is exponentially decayed. The surface charge density harmonically oscillates and propagates in the interface between the metal and dielectric in a form of surface charge cloud. In view of wave propagation vector, the wave propagation vectors of the surface plasma wave and interior of the bulk material can be respectively represented as follows: K sp = K o ⁢ ( ɛ m ⁢ ɛ b ) ( ɛ m + ɛ b ) ( 3 ) K b = K o ⁢ ɛ b ( 4 ) Wherein, K0 represents the wave propagation vector in vacuum, Ksp and Kb respectively represent the propagation vectors of the surface plasma wave and the interior of the bulk material. When Ksp=Kb, namely the wave propagation vectors are matched, the light incident in the interior of the bulk material can stimulate surface plasma waves, and thereby introducing energy into the interface. FIG. 3 is a diagram showing a curve of dispersion relationship of the surface plasma, the linear line K//represents the light propagating in air without crossing with the curve of the dispersion relationship of the surface plasma. It shows that the light in air incident in the metal does not excite the surface plasma wave. There are two ways to excite the surface plasma. One is to provide incident light in the form of evanescent waves to decrease the slope of the linear line to cross the curve of the dispersion relationship of the surface plasma wave; and the other is to provide a periodic structure in the surface of the interface to provide additional momentum in X direction, giving one opportunity for crossing the linear line and the curve. When the linear line and the curve are crossed, the resonance condition of the surface plasma is satisfied, and the photons would deliver energy to the surface plasmon by resonance. Using gratings to provide additional momentum on the surface to make crossing of the optical waves and the curve of the dispersion relationship of the surface plasma wave, the optical waves would couple with the surface plasma waves in accordance with the conservations of energy and momentum. If the thickness of the structure is appropriate, upper surface plasma waves would couple with lower surface plasma waves to delivery energy to one another side, and then the surface plasma waves couple with optical waves again to convert energy to optical waves to propagate outwardly. It can be inferred in view of the foregoing discussion that the wavelength of the incident light satisfies the resonance condition, namely the following equation (5) is sustained, and surface plasma wave is excited efficiently.λMax(i,j)=a0(i2+j2)−1/2(εmεb/(εm+εb))1/2 (5) Wherein a0 is structure period, εm and εb respectively are the dielectric constants of the metal and the incident interface. Besides, due to the surface plasma wave existing on the surface structure, if appropriately selecting the structure dimension, the surface field and radiated electromagnetic field would go through destructive interference, to further eliminate the electromagnetic fields that should be divergent at two sides. As a result, the divergence of the modulated optical wave behind the hole is decreased. Diffraction Theroy of Electromagnectic Waves of Levine and Schwinger The behavior of the effective cross section of the subwavelength surface structure on the metallic thin film larger than 1 can be explained by the electromagnetic diffraction of one single nanometer aperture proposed by Levine and Schwinger in the Journal of Electromagnetic Wave in 1950. The theory thereof is explored following. For a metallic thin film being infinitely large and thin as well as being a perfect conductor, when the electromagnetic waves are incident from Z direction in the metallic thin film, and passing through the hole of the metallic thin film, the diffraction behavior would be occurred in Z direction. To calculate the diffraction intensity of the hole, the boundary conditions of the metallic thin film should be firstly derived. Considering the symmetry of the incident plane of the electromagnetic waves and the diffraction plane, the boundary conditions are obtained:z≦0E(r)=E0(r)+E1(r); H(r)=H0(r)+H1(r)z≧0E(r)=E2(r); H(r)=H2(r) (6) Following, the problems of the electric and magnetic fields under the boundary conditions are treated by Green's Function. When one area is provided with electric current and electric charges, following relation (7) can be obtained by Maxwell equations: ∇ × ( ∇ × E ) - k 2 ⁢ E = 4 ⁢ ⁢ πⅈ ⁢ ⁢ k c ⁢ J - 4 ⁢ ⁢ π c ⁢ ∇ × J * ⁢ ⁢ ∇ × ( ∇ × H ) - k 2 ⁢ H = 4 ⁢ ⁢ π ⁢ ⁢ ⅈ ⁢ ⁢ k c ⁢ J * + 4 ⁢ ⁢ π c ⁢ ∇ × J ( 7 ) Wherein J is current density and J* is symmetric magnetizing current. The full-field Green's function and its solution derived from the relation (7) are as equation (6.3). The relation (7) obeys the boundary condition G=0 as r is infinitely far: ∇ × ( ∇ × Γ 0 ) - k 2 ⁢ Γ 0 = ɛ ⁢ ⁢ δ ⁡ ( r - r ′ ) ⁢ ⁢ Γ 0 ⁡ ( r , r ′ ) = ( ɛ - 1 k 2 ⁢ ∇ ∇ ′ ) ⁢ exp ⁢ ⁢ ( ⅈ ⁢ ⁢ k ⁢  r - r ′  ) 4 ⁢ ⁢ π ⁢  r - r ′  ( 8 ) Further establishing a half-field Green's Function by a method of image, and introducing Green's second vector identity and symmetry of Green's function to obtain electric and magnetic fields arisen by the surface current of the metallic thin film. Since the current density is a difference value of the magnetic field in the tangential direction, both of the derived electric and magnetic fields are integration forms including magnetic field and full-field Green's Function. Finally taking an approximate value to simplify the form of the electromagnetic field, and obtaining a far field distribution of the electromagnetic field. This result is introduced in Poynting vector for understanding of energy flow. Furthermore, the form of the energy flow is treated by Bessel Function to obtain total energy passing through the hole. If the effective cross section is defined by the total energy passing through the hole divided by the area of the hole. Taking its first-order and second-order approximate formulas to respectively compare with Rayleigh-Bethe and Kirchhoff diffraction formulas: t ( 1 ) = 8 9 ⁢ ⁢ π ⁢ ka · Im ⁢ ⁢ 1 F 11 ⁡ ( ka ) + kaF 11 ′ ⁡ ( ka ) = 64 27 ⁢ ⁢ π 2 ⁢ ( ka ) 4 ⁡ [ 1 + 27 25 ⁢ ( ka ) 2 + 0.72955 ⁢ ( ka ) 4 + … ] ⁢ ⁢ t ( 2 ) = 8 9 ⁢ ⁢ π ⁢ ka · Im ⁡ [ F 22 ⁡ ( ka ) - kaF 22 ′ ⁡ ( ka ) - ( 1 / 25 ) ⁢ ( ka ) 2 { F 11 ⁡ ( ka ) + kaF 11 ′ ⁡ ( ka ) - 10 ⁢ F 12 ′ ⁡ ( ka ) } { F 11 ⁡ ( ka ) + kaF 11 ′ ⁡ ( ka ) } { F 22 ⁡ ( ka ) - kaF 22 ′ ⁡ ( ka ) } + { kaF 12 ′ ⁡ ( ka ) } 2 ] = 64 27 ⁢ ⁢ π 2 ⁢ ( ka ) 4 ⁡ [ 1 + 27 25 ⁢ ( ka ) 2 + 0.74155 ⁢ ( ka ) 4 + … ] ⁢ ⁢ t R = 64 27 ⁢ ⁢ π 2 ⁢ ( ka ) 4 ⁡ [ 1 + 27 25 ⁢ ( ka ) 2 + 0.72955 ⁢ ( ka ) 4 ] ⁢ ⁢ t K = 1 - 1 2 ⁢ ka ⁢ ∫ 0 2 ⁢ ka ⁢ J 0 ⁡ ( t ) ⁢ ⁢ ⅆ t = ( ka ) 2 3 , ka → 0 ; ≈ 1 , ka → ∞ . ( 9 ) Wherein a=radius of the hole, k = 2 ⁢ ⁢ π λ · t ( 1 ) is a first-order diffraction approximation, t(2) is a second-order diffraction approximation, F is an integration form including Bessel Function to represent electric field of Poynting vector and Green's function; tR is Rayleigh-Bethe diffraction formula; tK is Kirchhoff diffraction formula. Four curves respectively plotted by the above four formulas are shown in FIG. 4. From the drawing of FIG. 4, the three diffraction formulas behave differently in respective sections. Rayleigh-Bethe diffraction formula merely has the former terms when expanded by ka. As ka is increased, the effective cross section is infinitely increased, which is contrary to the known physical phenomenon. Therefore, Rayleigh-Bethe diffraction formula is only suitable for diffraction behavior of the incident electromagnetic waves with a very long wavelength. For a short wavelength, Rayleigh-Bethe diffraction formula cannot reasonably predict the effective cross section of the electromagnetic waves. By the way, Kirchhoff diffraction formula postulates the electromagnetic field of the diffraction plane is merely influenced by the surface current of the metallic thin film when calculating, and neglecting the effect of the hole to the electromagnetic field. Kirchhoff diffraction formula can obtain a reasonable effective cross section in a long wavelength range. Its value is 1. But when ka is less than 3, the effective cross section calculated by Kirchhoff diffraction formula is far less than the values calculated by the other diffraction formulas. The diffraction formula of Levine and Schwinger represents the far field diffraction behavior of the light incident in the hole of the metal sheet. As ka is small, it shows diffraction behavior of the electromagnetic wave similar to that of Rayleigh-Bethe diffraction formula. As ka is increased, namely the incident wavelength decreased, the effective cross section with the behavior of Bessel function approximates 1. It also fulfills the behavior of the effective cross section in a short wavelength derived by Kirchhoff diffraction formula. Since the diffraction theory of Levine and Schwinger has not special postulations, it provides highly suitability. As to the foregoing double surface structures of the metallic thin film, the structure of the incident surface is primarily to increase light transmittance, and the structure of the emitting surface is primarily to depress the divergence angle of the transmitted optical field, the effect of the structure of the incident surface could be replaced by the appropriate single hole derived by the diffraction formula of Levine and Schwinger, even the incident surface of the metallic thin film is not provided with the surface structure. The high transmittance with the effective cross section higher than 1 still can be obtained by properly designing the size of the hole. The thickness of the metallic thin film employed in previous experiments for studies is merely 300 nanometers, and the metallic thin film is not provided with any support. Its structure is too fragile. When using the metallic thin film as the optical head, it is easily destroyed even slightly applying force upon it. From a view of engineering application, it is highly difficult to manufacture double surface microstructures, and which are hardly produced in a large quantity. Therefore, the Levine-Schwinger diffraction theory of electromagnetic waves can provide a practicability for designing an optical head with a single surface structure, and having a potential for applying the non-conventional optical phenomenon of the double surface structures to the practical engineering application. Design of Optical Head The present invention provides an optical head whose structure is as shown in FIG. 5. The optical head 10 includes a transparent substrate 101, a thin film 102 having a first surface 1021 and a second surface 1022, an inner surrounding wall 1023 extending from the first surface 1021 to the second surface 1022, a passage 1024 with a subwavelength aperture confined by the inner surrounding wall 1023 and a surface subwavelength structure 103. The surface subwavelength structure 103 can be a periodic structure or a grating structure. Besides, a is the thickness of the thin film 102, b is the depth of structure, c is the period of structure, d is the width of structure, and e is the dimension of the aperture of the passage 1024. In general, d should be larger than or equal to e. In addition, an external electromagnetic field 20 including an incident light 201 and an emitting light 202 is applied on the optical head 10. The incident light 201 transmits the transparent substrate 101 but hardly directly transmit the thin film 102, and only transmitting through the passage 1024 in a form of surface waves to form a new light source at an exit of the optical head 10, and re-emitting energy by diffraction. The transparent substrate 101 is also used for supporting the thin film 102. The surface subwavelength structure 103 is used for modulating the transmitted optical field (i.e. the surface waves transmitted through the passage 1024), and its structure can be formed of either of a plurality of elongated strips with a centered slit and a plurality of concentric circles with a centered hole, which are respectively as shown in FIG. 6A and FIG. 6B. The surface subwavelength structure 103 is used for controlling the optical field emitting from the optical head 10 in order that most energy is able to be concentrated in a subwavelength-scale area. A good subwavelength light source can be defined by the subwavelength-scale area whose full width at half maximum less than 0.75λ of the incident light 201 and its peak energy larger than other areas at least one order. The design parameters of the optical head 10 can be appropriately converted for being suitable for various light sources with different wavelengths. The conversion method can be derived by the following ways. Considering nonmagnetic material, i.e. μ=μ0, if under the circumstance with original design parameters, initial conditions and boundary conditions, it is assumed that the distributions of the electric and magnetic fields are and , and free electric charges and free current density are neglected, the electric and magnetic fields should fulfill following Maxwell's equations with a single frequency. ∇ · [ ɛ M 1 ⁡ ( ω , r r ) ⁢ E 1 ⁡ ( r r ) ] = 0 ⁢ ⁢ ∇ · [ μ 0 ⁢ H r ⁡ ( r r ) ] = 0 ⁢ ⁢ ∇ × E r ⁡ ( r r ) = - j ⁢ ⁢ ω ⁢ ⁢ μ 0 ⁢ H r ⁡ ( r r ) ⁢ ⁢ ∇ × H r ⁡ ( r r ) = j ⁢ ⁢ ω ⁢ ⁢ ɛ M 1 ⁡ ( ω , r r ) ⁢ E r ⁡ ( r r ) ( 10 ) After coordinate transformation to reduce a space dimension a times, namely r r = r r / a The functions of the original electric and magnetic fields also can fulfill Maxwell's equations by the following ways. a ⁢ ∇ ′ ⁢ · [ ɛ M 1 ⁡ ( ω , r r ′ ) ⁢ E 1 ⁡ ( r ′ r ) ] = 0 ⁢ ⁢ a ⁢ ∇ ′ ⁢ · [ μ 0 ⁢ H r ⁡ ( r ′ r ) ] = 0 ⁢ ⁢ a ⁢ ∇ ′ ⁢ × E r ⁡ ( r ′ r ) = - j ⁢ ⁢ ω ⁢ ⁢ μ 0 ⁢ H r ⁡ ( r ′ r ) ⁢ ⁢ a ⁢ ∇ ′ ⁢ × H r ⁡ ( r ′ r ) = j ⁢ ⁢ ω ⁢ ⁢ ɛ M 1 ⁡ ( ω , r ′ r ) ⁢ E r ⁡ ( r ′ r ) ( 11 ) If choosing ω ′ = ω / a , ⁢ λ ′ = 2 ⁢ π ⁢ ⁢ c / ω ′ = a ⁢ ⁢ λ , ⁢ ɛ M 2 ⁡ ( ω ′ , r r ) = ɛ M 1 ⁡ ( ω , r ′ r ) ( 12 ) Then, ∇ ′ ⁢ · [ ɛ M 2 ⁡ ( ω ′ , r r ′ ) ⁢ E 1 ⁡ ( r ′ r ) ] = 0 ⁢ ⁢ ∇ ′ ⁢ · [ μ 0 ⁢ H r ⁡ ( r ′ r ) ] = 0 ⁢ ⁢ ∇ ′ ⁢ × E r ⁡ ( r ′ r ) = - j ⁢ ⁢ ω ′ ⁢ ⁢ μ 0 ⁢ H r ⁡ ( r ′ r ) ⁢ ⁢ ∇ ′ ⁢ × H r ⁡ ( r ′ r ) = j ⁢ ⁢ ω ′ ⁢ ⁢ ɛ M 2 ⁡ ( ω ′ , r ′ r ) ⁢ E r ⁡ ( r ′ r ) ( 13 ) Comparing equations (10) and (13), it is discovered that equation (10) is a governing equation of electromagnetic field when the wavelength is λ, and if the wavelength is changed to a λ and choosing another specific material whose dielectric constant is the same with that of the original material when the wavelength is λ, equation (13) provides that the solution of the electromagnetic field is maintained, merely the dimension is enlarged a times. Hence, if it is desired to design another optical head suitable for another wavelength, for example using an incident light with a wavelength a times the original wavelength, the design way is as follows: making the dimension of the optical head become a times that of the original design, and using another material, whose dielectric constant at this wavelength is the same with that of the original thin film, to form the thin film. As shown in FIG. 7, if using the material having dispersion relationship as curve M1 to form the thin film at the original wavelength λ, then using the material having dispersion relationship as curve M2 to form the thin film when designing an optical head with a wavelength a λ, and the dielectric constant of the M1 material at the wavelength λ is equal to that of the M2 material at the wavelength a λ. As a consequence, the optical head would have similar physical behavior with the original optical head except that the dimension of the optical head is enlarged a times. Therefore, the present invention provides a method for producing various optical heads with different wavelengths. The range, effect and relationship of various parameters of the optical head are described as follows: 1. The thin film to build the optical head can be formed by a material with a relative dielectric constant ranging between −4.5 and −6.5 and between −15 and −32. 2. The surface subwavelength structure of the optical head can be formed by a material with a relative dielectric constant ranging between −4.5 and −6.5, between −15 and −32, between 2.5 and 3.3, between 4.8 and 6.5, and between 8.8 and 9.2. 3. The period of the surface subwavelength structure of the optical head can be ranging between 0.35λ and 0.8λ of the incident light. 4. The period of the surface subwavelength structure of the optical head can be ranging between 0.45λ and 0.7λ of the incident light so as to provide a good subwavelength light beam. 5. The thickness of the thin film influences the intensity of the transmitted optical field; as the foregoing, the thin film is used for preventing the incident light from directly transmitting. Therefore, the selection of the thickness of the thin film relies upon the achievement of the above purpose. The more the thickness of the thin film is, the smaller the intensity of the transmitted optical field is. The distribution of the transmitted optical field is hardly influenced by the thickness of the thin film, which corresponds the foregoing transmittance phenomenon of the incident light in the form of surface waves.6. As the aperture of the passage of the thin film is shrunk, the full width at half maximum of the light beam becomes smaller when the light beam is focused.7. As the depth of the structure of the surface subwavelength structure becomes shallower, the range of the structure period, capable of modulating the transmitting optical field to show the phenomenon of focusing, is shifted toward a positive direction. Giving an example by the optical head, for which the wavelength of the incident light is 442 nanometer, the width of the grating is 250 nanometer, the width of the slit is 125 nanometer, the thickness of the thin film is 150 nanometer, the depth of the surface structure is 60 nanometer, and the dielectric constants of the thin film and structure material are −5.76+0.22i (Ag), the result calculated by the Finite Difference Time Domain Method shows that the Poynting vectors of the optical head in axis and traverse directions are respectively as shown in FIG. 8 and FIG. 9, in which the exit of the optical head is positioned at z=0.91 μm. In view of FIG. 8, it is known that the optical field is indeed divergent at the exit of the optical head, but at z=1.00 μm, the traverse energy flow is abruptly decreased to less than one order of the axis energy flow. It means that the divergence angle of the optical field is quite small, ended at z=1.60 μm. The axis distance is about 600 nanometers, however, the poynting vector is mainly concentrated in the 300-nanometer traverse distance. Accordingly, the concept of using the surface subwavelength structure to modulate the optical field to provide a subwavelength-scale optical spot can be proved herein. In addition, as shown in FIG. 10 and FIG. 11, a good subwavelength optical field also can be provided in the case that the width of the grating is 260 nanometer, the width of the slit is 130 nanometer, the thickness of the thin film is 150 nanometer, the depth of the surface structure is 60 nanometer, the dielectric constant of the material of the thin film is −5.76−022i (Ag) and the relative dielectric constant of the structure material is 9. The optical head of the present invention also can be applied to optical etching for providing a smaller optical spot for etching to improve the resolution of the optical etching. As shown in FIG. 12, the incident light 20 passes through the optical head 10 to provide an optical spot smaller than the diffraction limit, then radiating onto a photoresist layer 30 for exposing. A translational stage 40 is used for adjusting the relative position between the optical head 10 and the photoresist layer 30 so as to etch various patterns. In addition, the optical head of the present invention can be applied to optical storage for providing a smaller optical spot for recording to improve storage density of the optical storage device. As shown in FIG. 13, the incident light 20 passes through the optical head 10 to provide an optical spot smaller than the diffraction limit, and then radiating onto a photosensitive compound 50. The optical spot for recording is designated as numeral 501. In the application of optical imaging and probing, the optical head of the present invention also can provide a smaller optical spot for measuring to improve the resolution of measurement. As shown in FIG. 14, the incident light 20 passes through the optical head 10 to provide an optical spot smaller than the diffraction limit, and then radiating onto a sample 60 to be monitored, then the intensity of the light transmitted the sample 60 is detected by a light-detecting device 70 to obtain information of the sample 60. Besides, the present invention can combine a plurality of the optical heads to form a structure of multi-optical heads in order that the optical heads can be either independently operated or operated together. As shown in FIG. 15 and FIG. 16, in which FIG. 15 is a schematic top view of the structure of the multi-optical heads and FIG. 16 is a schematic cross sectional view thereof. The structure of the multi-optical heads 11 includes a plurality of optical heads 10 each of which corresponding to a switch 110 capable of being independently controlled for blocking or permitting the light beams passing through. This technology can be applied to the optical etching, optical storage or optical imaging and probing. Numeral 80 can be a photoresist layer, photosensitive compound or a transparent sample to be monitored. The embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the embodiments can be made without departing from the spirit of the present invention.
043893686	summary	DESCRIPTION Background of the Invention This invention relates to high pressure fluid cooled nuclear reactors and means for minimizing the effects of a loss-of-coolant through a cold leg break or loss-of-power to the reactor coolant pumps. In the event of an accident in which there is a break in the cold leg of the reactor coolant system, it has been postulated that the entire coolant medium which absorbs and removes the heat generated in the nuclear core will be lost or at least considerably decreased. If sufficient coolant water does not reach the reactor core within the first minute following the accident, the entire reactor core, fuel and supporting structure begins to melt down and slump to the bottom of the reactor vessel. Emergency cooling water injected at this stage may well amplify the disaster as the now molten metals can react violently with water, generating large quantities of heat, releasing steam and hydrogen in amounts and at pressures that can themselves breach the containment. If the containment vessels themselves do not burst, it has been postulated that the molten mass of fuel would continue to melt downward, fed by the heat generated by fission product radioactivity. If a break occurs in the cold leg between the reactor vessel and the coolant pump causing the loss of coolant accident, then the first path for pressure relief is down through the middle of the reactor core and up through the outer annulus between the core support barrel and the pressure vessel walls and out through the cold leg to the break. This flow is opposite to the normal flow of reactor coolant as well as the flow of emergency core cooling water being injected into that leg, thereby impeding the flooding of the reactor core from the bottom. The second path for pressure relief is from the plenum above the reactor core out through the hot leg to the steam generator, through the steam generator and through the coolant pump to the cold leg break where the steam is discharged to the atmosphere. The steam that flows through this path is being driven by the pressure differential between the high pressure in the reactor plenum above the core and the containment buliding pressure which is initially atmospheric. Consequently, the steam flow rate is very high and the steam tends to drive the reactor pump like a turbine. This circumstance produces the substantial danger of over speeding the reactor coolant pump to the point where the massive flywheel connected to the reactor coolant pump shaft disintegrates and eventually would cause severe damage to the surrounding equipment. Flywheels store the energy required to maintain sufficient cooling flow after a loss-of-power to the driving motors. Absence of the flywheels would allow the motor and its coupled pump to slow, or stop, more rapidly, such that the slowing, or stationary pump impeller would seriously restrict the coolant flow. This desirable flow is traversing in the desired direction due to the previously established momentum of the fluid and the thermal driving head established by the fluid being heated in the reactor and being cooled by the steam generators. Restriction of this flow is undesirable. It is to the solution of these problems that the present invention is directed. One prior art solution to the problem is represented by U.S. Pat. Nos. 4,017,217 issued Apr. 12, 1977 to Robert P. Lamers and 4,036,561 issued July 19, 1977 to Elmar Harand et al. According to the teachings of these patents, brake means are provided to prevent overspeeding of the coolant pump and motor. However, in the event of a loss of coolant accident, it is desirable to maintain the flow established by the fluid momentum and the thermal driving head to reduce the temperature of the reactor. The braking of the coolant pumps according to the teaching of the prior art will at least limit the flow of coolant and will tend to actually impede the flow of coolant under these emergency conditions and will be no benefit during the loss-of-power casualty. Other prior art solutions are represented by U.S. Pat. No. 4,064,001, issued Dec. 20, 1977 to Richard J. Duncan and the article in the April 1970 issue of "Power Magazine" on pages 90-91. According to these solutions, valve means are provided to help maintain normal flow direction through the reactor vessel. While these would reduce the amount of stored energy which would cause pump overspeed, it is expected that these reductions would be insufficient to solve the overspeed problem. These solutions are expected to have no effect on the loss-of-power casualty. SUMMARY OF THE INVENTION According to this invention, an improvement is provided in a pressurized fluid nuclear steam supply system which not only provides overspeed protection to prevent the failure of a flywheel caused by an overspeed condition of the pump, but also enhances the flow of fluid under other emergency conditions. An analysis of a pump fitted with this means might indicate that the pump motors could be fitted with smaller flywheels and might further indicate that the flywheel could be eliminated. The improvement comprises a unidirectional drive means interposed between the coolant pump and the motor driving the pump. The unidirectional drive means is adapted to enable the pump to operate in the pumping direction only at a greater speed than the motor which normally drives it. That is, it allows the impeller to free-wheel in the pumping direction.
	description	This application claims the benefit of priority from European Patent Application EP17156621 filed Feb. 17, 2017, which is incorporated by reference in its entirety. The present invention relates to generally relates to the field of X-ray analysis. More particularly, the invention relates to an X-ray optical device. X-ray analysis techniques, such as X-ray diffraction (or XRD) have become very popular because they enable a non-destructive analysis of samples. For instance, X-ray diffraction has become one of the fundamental experimental techniques for investigating structural properties of crystalline samples of proteins or other macromolecules. Generally, the preparation of macromolecule samples in crystalline form is challenging. Usually, the samples are very small, and X-ray diffractometers are required which are capable of directing a focused X-ray beam with small cross-sectional size and high intensity onto the small samples. Such X-ray diffractometers are described in DE 10 2004 052 350 A1 and US 2010/0086104 A1. These diffractometers include an X-ray source that emits X-rays, X-ray optics designed to image a beam of X-rays generated by the X-ray source onto a sample to be analyzed, a sample stage on which the sample to be analyzed is positioned, and an X-ray detector designed to detect the scattered X-rays. As X-ray optics, reflective optics are employed comprising one or two multilayer mirrors (also known as Goebel or Montel optics) which are arranged and designed to image an X-ray beam with specific beam properties onto the sample. Since the design of the X-ray optics, such as the surface curvature of the mirrors is fixed and cannot be adjusted to specific experimental needs later on, it has to be decided at the stage of production of the optics which experimental needs should be met. In X-ray diffraction, one relevant beam properties (or parameters) are the convergence angle and divergence angle of the focused beam, the beam intensity and the beam size at the focal point. The resolution of the X-ray diffractometer depends on the beam convergence and divergence angles and decreases with increasing convergence and divergence angles. On the other hand, the signal-to-noise ratio improves with increasing beam intensity, and the beam intensity increases with increasing convergence and divergence angles. Therefore, depending on the properties of the sample to be analyzed (i.e., whether the sample has a small or large unit cell) different convergence and divergence angles and therefore different X-ray optics are needed. In order to tune the convergence and divergence angles of the imaged beam at the focal point, US 2009/0129552 A1 suggests using an adjustable aperture in order to occlude or cut away certain portions of the X-ray beam reflected by the X-ray optics. The adjustable aperture is arranged at or in the close proximity of the distal end of the optics (i.e. at the end facing away from the X-ray source) and is made of two angled plates, wherein at least one of the two angled plates can be linearly moved. Adjustable apertures for occluding unwanted X-ray beam portions are also known from US 2010/0086104 A1. According to one implementation, the aperture is defined by two L-shaped aperture blades. At least one L-shaped aperture blade is movable by means of a high-precision micrometer screw or fine-thread bolt. Depending on the direction of rotation the screw is turned, the blade can be linearly moved forth or back so that the aperture opening size narrows or widens accordingly. According to another implementation, an aperture with fixed aperture opening size is suggested. In this embodiment, the aperture is movable as a whole in a plane perpendicular to the propagation of the X-ray beam. By appropriately moving the aperture relative to the X-ray beam, unwanted X-ray portions can be occluded so that only a beam portion with a desired convergence and divergence angle can pass the aperture opening. Again the linear movement of the aperture with respect to the X-ray beam is implemented by micrometer or fine-thread screws. The above-described aperture designs have some drawbacks. First, micrometer screws or fine threaded screws are expensive and very sensitive to external influences. Further, apertures with micrometer screws are difficult to implement in a gas-tight housing in which the reflective optics are received. Still, further, aperture blade motion by micrometer screws is difficult to control because of motion parameters, such as start position, end stop, change of the sense of rotation, have to be precisely defined. An X-ray optical device includes an X-ray source configured to emit X-rays, an X-ray optics configured to image a beam of X-rays generated by the X-ray source onto a sample to be analyzed, a beam collimating device, and a beam blocking element arranged for selectively blocking off at least a portion of the X-ray beam output by the X-ray optics. The beam blocking unit has a rotating shaft and a beam blocking element, wherein the rotating shaft is rotatable around its axis and arranged laterally offset with respect to the X-ray beam output by the X-ray optics. The beam blocking element is mounted eccentrically on the rotating shaft such that the beam blocking element is movable into different beam overlap positions for blocking off desired beam portions when the beam blocking element is eccentrically rotated around the rotating shaft axis. The beam portions blocked off by the beam blocking unit correspond to those beam portions of the output X-ray beam which are overlapped by the eccentrically rotating beam blocking element. The remaining unblocked (or non-overlapped) beam portions can pass through the beam blocking unit and propagate to the sample to be analyzed. The ratio between the unblocked beam portion and blocked beam portion can be continuously changed by rotating the beam blocking element into different beam overlap positions. Accordingly, unblocked beam portions with desired beam properties (i.e., with desired divergence angles, beam intensities, beam sizes or beam cross-sectional areas) can be easily adjusted by simply changing the angular position of the eccentrically rotating beam blocking element. Since the beam blocking element and the rotating shaft rotate about the same rotating shaft axis, the beam overlap position reached by the beam blocking element may depend on the angle of rotation of the rotating shaft. Thus, by turning the rotating shaft by a specific angle of rotation, a specific beam overlap position for the beam blocking element can be reached. Accordingly, beam portions with desired convergence angles and divergence angles can be cut out by simply turning the rotating shaft about its axis. By turning the rotating shaft around its axis, the eccentrically rotating beam blocking element may be movable between a predetermined minimum beam overlap position and a predetermined maximum beam overlap position. The minimum overlap position may be a position where the beam blocking element has a minimum overlap with the output X-ray beam. The maximum overlap position may be a position where the beam blocking element has a maximum overlap with the output X-ray beam. Accordingly, the beam portion of the X-ray beam which is not overlapped by the beam blocking element and which can pass through the beam blocking unit becomes smallest at the maximum overlap position and largest at the minimum overlap position. The maximum overlap obtainable by the eccentrically beam blocking element may depend on the geometric dimensions of the beam blocking element, in particular on its lateral dimensions. According to one variant, the beam blocking element may be dimensioned such that it fully overlaps with the output X-ray beam in the maximum overlap position. According to an alternative variant, the beam blocking element may be dimensioned such that it only partially overlaps with the output X-ray beam. Beam overlaps in the range of 50% to 100% of the output X-ray beam may be conceivable for the maximum overlap position. The minimum overlap obtainable by the eccentrically rotating beam blocking element may also depend on the geometric dimensions of the beam blocking element and its eccentric bearing on the rotating shaft. According to one variant the minimum overlap may also include the limit of no overlap between the beam blocking element and the output X-ray beam. Beam overlaps in the range of 0% to 40% of the output X-ray beam may be conceivable for the minimum overlap position. The minimum overlap position and the maximum overlap position may each be associated with a specific angular position of the rotating beam blocking element and the corresponding rotating shaft. The beam blocking element may be designed and eccentrically mounted on the rotating shaft such that starting from the minimum overlap position the maximum overlap position can be reached by a 180° (or one-half) turn of the rotating shaft (and the corresponding beam blocking element). Moreover, the beam blocking element can reach any position between the minimum overlap position and the maximum overlap position by simply rotating the rotating shaft around its axis by a corresponding angle of rotation selected between 0° to 180°. After having reached a maximum overlap position by a 180° degree turn of the rotation shaft, the beam blocking element can be further moved from the maximum overlap position back to the minimum overlap position by a further 180° degree rotation (further one-half turn). Thus, by turning the beam blocking element by a full turn (360° turn), the beam blocking element can oscillate (i.e., move forth and back) between the minimum overlap position and maximum overlap position. Further, the rotation of the rotating shaft and beam blocking element may not be limited to one full revolution. They can be rotated multiple revolutions without limitation in either direction. The beam blocking element oscillates thereby between the minimum overlap position and maximum overlap position with an oscillation period of 360°. Therefore, any overlap position between the minimum and maximum overlap positions can repeatedly be reached by simply continuing turning the rotating shaft in one direction. Although forth and back movement is possible, there is no need to change the direction of rotation of the rotating shaft because starting from a current overlap position any other overlap position between the minimum and maximum positions (including the minimum position and maximum position) can be obtained within a further full revolution of the rotating shaft. Hence, there is no need for a forth and back movement of the beam blocking element in order to adjust different overlap positions. Thus, the control of the beam blocking element position can be further simplified. The beam blocking element may comprise a rotationally symmetric body with a lateral surface defining a beam blocking edge for the output X-ray beam. The beam blocking element may be mounted on the rotating shaft such that a rotation axis of the rotationally symmetric body is substantially parallel to the rotation axis of the rotating shaft, but located offset therefrom. Due to this offset, the body may carry out an eccentric rotation about the shaft axis so that the beam blocking edge can oscillate between the predetermined minimum beam overlap position and maximum beam overlap position. The lateral surface of the rotationally symmetric body may be the body surface along its circumferential direction. Further, the beam blocking edge may be defined by a contour of the lateral surface. The contour may be defined by the one-dimensional lateral body edge obtained from a projection of the rotationally symmetric body onto a cross-sectional plane being substantially perpendicular to the direction of propagation of the output X-ray beam. Due to the eccentric rotation, the body may increasingly or decreasingly overlap with the output X-ray beam and, accordingly, the body contour can move further into or out of a beam cross-sectional area lying within the plane. Thus, the body may function as variable slit or aperture for the output X-ray beam with the lateral surface as a movable slit or aperture edge. The contour of the lateral surface defining a beam blocking edge may further align with a cross-sectional shape of the output X-ray beam. The shape of the beam cross-section may be substantially perpendicular to the beam propagation direction. For instance, if the cross-sectional shape of the output X-ray beam may be rectangular, the beam blocking element body may be a cylinder having a lateral surface contour of a straight line that may be aligned with a side of the rectangular shape of the output beam. Alternatively, if the cross-sectional shape of the output X-ray beam is diamond-shaped, the body of the beam blocking element may be a double cone, having an L-shaped contour which is aligned with two sides of the diamond-shaped cross-sectional area. Independent of the above described geometrical form, the beam blocking element (beam blocking element body) may be made of a material which effectively absorbs X-rays. According to one variant, the beam blocking element may be made of bronze. The beam blocking element may be securely mounted on the rotating shaft. The rotating shaft, in turn, may be rotatably born by a bearing unit. The bearing unit may be arranged after the X-ray optics. For instance, the bearing unit may be arranged at or in the vicinity of the distal end of the X-ray optics (i.e., the end facing away from the X-source). Further, the bearing unit may be mounted such that the rotating shaft may be located off the beam. That is, the rotating shaft may not overlap with the output X-ray beam. The X-ray optical device may further comprise a casing designed for receiving at least one bearing unit, the rotating shaft and the beam blocking element. Further, the casing may be designed for additionally receiving the X-ray optics. The casing may be designed as an air-tight casing which can be evacuated and/or filled with a protective gas. The X-ray optical device may also comprise at least one sealing element arranged for realizing an airtight seal around the rotating shaft. For instance, O-rings may be used as sealing elements. In order to obtain a desired beam overlap position, the rotating shaft may be turned either manually or automatically. For implementing an automated shaft rotation, the X-ray optical device may further comprise a driving unit operatively connected to the rotating shaft and configured to rotate the shaft by predetermined angles of rotation. Further, the X-ray optical device may also comprise a sensor unit configured to measure the current angular position and/or angular displacement of the shaft during shaft rotation. Since each angular position can be assigned to a specific overlap position of the beam blocking element, the current overlap position can be easily adjusted by setting a corresponding angle of rotation for the shaft. The driving unit may comprise an electrical motor configured to generate a torque and a transmission unit configured to transmit the torque to the shaft. As transmission unit, a belt drive may be used. However, other transmissions are also conceivable for transmitting the motor torque to the shaft. The X-ray optical device may further comprise a control unit. The control unit may be in communication with the sensor unit, driving unit, and an external input device. The control unit may be programmed to determine an actual beam overlap position of the beam blocking element based on the angular position of the rotating shaft measured by the sensor unit, to compare the actual overlap position with a set beam overlap position received from the input device, and to generate, based on the comparison, a motor signal that controls the motor of the driving unit to drive the rotating shaft to an angular position that corresponds to the set overlap position. For this purpose, the controller may comprise at least one processor for processing software routines implementing the above-described control steps. The X-ray optics of the X-ray optical device may comprise at least one reflective element shaped to focus the X-ray beam onto a predetermined focal point with a predetermined focal length. The at least one reflective element may be designed as multilayer mirror with (laterally or depth) graded d-spacing. According to one variant, a Goebel optics may be realized comprising only one reflective mirror. According to an alternative variant, a Montel optics may be realized comprising two reflective mirrors mounted side by side and mutually perpendicular. The X-ray optics may further comprise a collimator arranged after the X-ray optics and configured to further refine the beam of X-rays in between the X-ray optics and the sample to be analyzed. The collimator may comprise a pipe with one or more pinholes or a capillary pipe or any other collimator elements for beam refining. According to one implementation variant, the beam blocking unit may be arranged after the X-ray optics but before the collimator. According to an alternative implementation variant, the beam blocking unit may be arranged after the X-ray optics and the collimator. The X-ray source of the X-ray optical device may be a conventional X-ray generator configured to generate X-rays by bombarding metal targets with high-velocity electrons accelerated by strong electric fields. The metal target may be implemented as rotating or fixed target. Further, as a metal target, chromium (Cr), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag) or iron (Fe) target may be used. According to another aspect of the invention, a method of operating the above described X-ray optical device is provided. The may include the steps of generating, by the X-ray source, an X-ray beam, imaging, by the X-ray optics, the X-ray beam onto a sample to be analyzed, collimating, by the collimator, the beam of X-rays to be imaged to the sample, and adjusting a divergence angle and/or intensity of the imaged X-ray beam in dependence of the sample to be analyzed. The adjusting step may include moving the beam blocking element towards a desired beam overlap position by rotating the rotating shaft of the beam blocking unit by a predetermined angle of rotation. The adjusting step may be performed automatically by the above-mentioned control unit and driving unit which is mechanically coupled with the rotating shaft. According to still another aspect, an X-ray analysis system is provided, comprising the above described X-ray optical device, a sample stage configured to hold and orient a sample to be analyzed relative to the X-ray beam output by the X-ray optical device, and an X-ray detector configured to detect X-rays scattered by the sample. The X-ray analysis device may be an X-ray diffractometer designed for analyzing crystalline or powder samples. With the crystalline sample, a sample may be prepared in monocrystalline or polycrystalline form. The sample stage may be designed to position the sample in an arbitrary position and orient the sample relative to the output beam. In particular, the stage may be designed for rotating the sample in two different directions. The X-ray detector may be configured to detect the scattered X-ray beam. As X-ray detector, a commercially available one-dimensional or two-dimensional X-ray detector may be used, which is configured to measure the intensity of X-ray beams diffracted from the sample as a function of position, time, and energy. Further objects, features, and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. In the following description, for explanation and not limitation, specific details are outlined to provide a thorough understanding of the X-ray analysis system and X-ray optical device presented herein. It will be apparent for one skilled in the art that the disclosed X-ray analysis system and X-ray optical device may deviate within the scope of protection from specific details set forth hereinafter. FIG. 1 illustrates a schematic representation of an X-ray analysis system 100 according to the claimed invention. The X-ray analysis system 100 is an X-ray diffractometer designed for carrying out X-ray diffraction analyses on crystalline samples 300. The X-ray analysis system 100 comprises an X-ray optical device 110, a sample stage 120 and an X-ray detector 130. The X-ray optical device 110, in turn, comprises an X-ray source 1100, an X-ray optics 1200, and an X-ray beam blocking unit 1300. The X-ray optical device 110 may also comprise a collimator (not shown in FIG. 1) for refining the imaged beam. The X-ray source 1100 of the X-ray optical device 110 is configured to generate X-ray radiation 220. For this purpose, a conventional X-ray generator may be employed which is configured to generate X-rays 220 by bombarding a static or rotating metal target with high-velocity electrons accelerated by strong electric fields. As metal target, a chromium (Cr), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag) or iron (Fe) target may be used. According to a preferred implementation, a copper or molybdenum target is used. The sample stage 120 is configured to hold the sample 300 in predetermined orientations relative to the X-ray beam 240 output from the X-ray optics 1200. In order to orient the sample 300 with respect to the X-ray beam 240, the stage 120 may be rotatable in at least two independent directions. The X-ray detector 130 is configured to measure intensity, spatial distribution, spectrum and/or other properties of the X-rays scattered by the sample 300. Conventional scintillation detectors or gas-filled detectors may be used, as known from the prior art. The X-ray optics 1200 is arranged between the X-ray source 1100 and the sample stage 120. The X-ray optics 1200 is arranged and configured such that a monochromatic X-ray beam 240 of predetermined shape is generated from the X-rays 220 of the X-ray source 1100 and imaged to a specific region where a sample 300 can be placed. For this purpose, the X-ray optics 1200 may be designed as X-ray focusing optics comprising at least one reflective element 1210, such as a multilayer mirror with (laterally or depth) graded d-spacing. The surface of the reflective element 1210 may be shaped such that an X-ray beam 240 with a predetermined shape, size, intensity and convergence and divergence angle 310 at the image focus is obtained. The beam blocking unit 1300 of the X-ray optical device 110 is disposed at the exit (i.e., distal end) of the X-ray optics 1200. The beam blocking unit 1300 comprises a beam blocking element 1320 and a rotating shaft 1310. The rotating shaft 1310 is disposed laterally and does not overlap with the output X-ray beam 240. According to the implementation illustrated in FIG. 2, the rotating shaft 1310 and the beam blocking element 1320 are arranged close to a beam side where the beam 240 has its lowest intensities. An alternative implementation is also conceivable, in which the rotating shaft 1310 and the beam blocking element 1320 are arranged at the opposite side, i.e., in the vicinity of a beam side where the beam 240 has its highest intensity. In this context, it is noted that the beam intensity may not be uniform over the reflective element 1210 and may vary from its near end 1210a (i.e., the reflective element end closest to the X-ray source 1100) to its far end 1210b (i.e., the reflective element end farthest away from the X-ray source 1100) due to different X-ray capture angles at the near end 1210a and far end 1210b of the reflective element 1210. Generally, X-ray beam portions 240a reflected from reflective element portions at or close to the near end 1210a have a higher intensity than beam portions 240b reflected from reflective element portions at or close to the far end 1210b. Independent of the above described arrangement at the near end beam side or far end beam side, the beam blocking element 1320 is mounted eccentrically on the rotating shaft 1310 so that a rotation of the rotating shaft 1310 around its axis (see arrow in FIG. 2) causes an eccentric rotation of the beam blocking element 1310 around the rotating shaft 1310 and thereby a rotation-dependent movement of the beam blocking element 1320 relative to the output X-ray beam 240. That is, due to the eccentric arrangement of the beam blocking element 1320 (i.e., a centre of gravity axis of the beam blocking element 1320 is offset to the axis of the rotating shaft 1210) at least a portion of the laterally arranged beam blocking element 1320 can be rotated into the output X-ray beam 240. Accordingly, the output X-ray beam 240 can at least be partially overlapped by the beam blocking element 1320 so that only a remaining non-overlapped beam portion 240a can pass through the beam blocking unit 1300. In FIG. 1, the beam blocking element 1320 is shown to assume two different beam overlap positions, i.e., a minimum overlap position (solid line representation of the beam blocking element 1320) and a maximum overlap position (see dashed line representation). In the present case, the minimum overlap position corresponds to a non-overlapping position, where the beam blocking element 1320 is turned away from the output X-ray beam 240 and does not overlap with the output X-ray beam 240 at all. In this case the X-ray beam 240 output by the X-ray optics 1200 can pass through the blocking unit 1300 as a whole. However, it is also conceivable that the beam blocking unit 1300 is designed such that a small overlap between the beam blocking element 1320 and the output X-ray beam 240 still remains even in the case the beam blocking element 1320 is rotated away from the output X-ray beam. In such a case a small beam portion is also blocked off in the minimum overlap position. The maximum overlap position corresponds to the position where a maximum overlap between the beam blocking element 1320 and the X-ray output beam 240 is reached. From the drawing in FIG. 1 it becomes clear that the maximum overlap position reachable by the beam blocking element 1320 mainly depends on the geometric dimensions of the beam blocking element 1320. For instance, the beam blocking element 1320 can be dimensioned in directions perpendicular to the rotating shaft 1310 such that the whole X-ray beam 240 or only a portion 240a thereof is overlapped by the beam blocking element 1320, when the beam blocking element 1320 reaches its maximum overlap position. In FIG. 1, only for the purpose of explanation but not of limitation, the beam blocking element 1320 at the maximum overlap position only blocks off a portion 240b of the output X-ray beam 240. The remaining unblocked beam portion 240a can still pass through the blocking unit and reach the sample 300. Accordingly, the convergence angle or, equivalently, the divergence angle 310a of the remaining unblocked beam portion 240a is reduced compared to the convergence angle or divergence angle 310 of the whole beam 240. The minimum overlap position and the maximum overlap position of the beam blocking element 1320 can be each associated with a specific angular position of the rotating shaft 1310. In the present case the beam blocking element 1320 is designed and born on the rotating shaft 1310 such that the minimum overlap position can be associated with a 0° angular position and the maximum overlap position with a 180° angular position of the rotating shaft 1310. In other words, when starting from the minimum overlap position, the maximum overlap position is obtainable after a 180° turn of the rotating shaft 1320. Further, any overlap position between the minimum overlap position and the maximum overlap position can be obtained by simply rotating the rotating shaft 1310 about a corresponding angle of rotation between 0° and 180°. Thus, by choosing appropriate angles of rotation for the rotating shaft 1310 any desired overlap position between the predefined minimum and maximum overlap positions can be adjusted. Accordingly, desired portions of the beam 240 can be selectively blocked off so that the convergence/divergence angles 310 can be selectively adjusted to the experimental needs. The beam blocking element can be rotated multiple revolutions without limitations. By carrying out one full revolution (i.e. 360° turn) the beam blocking element 1320 can be moved from the minimum overlap position (or non-overlapping position) to the maximum overlap position and back to the initial minimum overlap position. As the beam blocking element 1320 oscillates with a rotation period of 360° between the minimum overlap position and maximum overlap position, there is no need to change the direction of rotation regardless of whether the beam blocking element 1320 is turned into the beam or out therefrom. In the following, the operation of the X-ray system 100 will be further described. In operation, the X-ray source 1100 emits X-rays (e.g. X-ray generated by a Cu-target) towards the reflective optics 1200. The reflective optics 1200, in turn, reflects X-rays of a selected wavelength (for instance Cu-Kα) in form of an X-ray beam of predetermined cross-sectional area and cross-sectional shape towards a crystalline or powder sample 300 to be investigated. The shape and cross-sectional area of the X-ray beam depends on the X-ray optics design and may vary between different design implementations. The sample 300 is mounted on the sample stage 120 and can be oriented by means of the stage 120 with respect to the X-ray beam 240. The sample orientation can be changed by rotating the sample 300 during X-ray beam exposure. The X-ray beam 240 is diffracted by the sample 300. The intensity and spatial distribution of the diffracted X-ray beams at different sample orientations are recorded by means of the detector 130 and, based thereon an X-ray diffraction pattern is generated. The obtained X-ray diffraction pattern comprises spaced apart discrete spots for crystalline samples or lines for powder samples. The resolution of X-ray diffraction patterns (i.e., the distinguishability of adjacent spots or lines) depends on the divergence angle of the X-ray beam 240 output by the X-ray optics 1200. For samples 300 with large unit cells, an output X-ray beam 240 with small divergence angle is desired in order to improve the pattern resolution. An X-ray beam 240 with small divergence angle can be reached by simply rotating the beam blocking element 1320 to a desired overlap position (see, for instance, FIG. 1). Since in FIG. 1 the beam blocking element 1320 is arranged to block off the weak beam portion 240b of the output X-ray beam 240, X-ray beams with small divergence angle can be obtained at the sample 300 without restricting too much the beam intensity. Thus, the beam blocking element 1320 functions as adjustable aperture capable of restricting the output X-ray beam 240 to beams of desired divergence angles. Furthermore, the beam blocking element 1320 can be used to adjust the intensity of the output X-ray beam 240 reaching to the sample 300. For the case of a strongly diffracting sample 300 the diffracted intensity reaching the detector 130 may be too intense to be measured correctly and in such a case the beam blocking element 1320 can be simply rotated to a desired overlap position in order to achieve a reduced X-ray beam intensity on the sample 300. In conjunction with FIG. 2 an implementation of the X-ray optical device 110 will be further described. More specifically, an implementation of the X-ray optics 1200 and beam blocking unit 1300 of the X-ray optical device 110 is further described. FIG. 2 illustrates a three-dimensional view of an end portion of the X-ray optics 1200 which is faced away from the X-ray source 1100. The X-ray optics 1210 comprises two reflective mirrors 1212, 1214 and a casing 1230a for receiving the mirrors 1212, 1214. The X-ray optics 1200 may further comprise a pivoting mechanism 1240 for pivoting the casing 1230a in at least one direction and an outer housing 1230c for receiving the casing 1230a and the pivoting mechanism 1250 (not shown in FIG. 2, but visible in FIG. 4). Moreover, the outer housing 1250 may be provided with pins 1260 at its proximal end through which the housing 1250 can be mechanically connected to the X-ray source 1100. The two reflective mirrors 1212, 1214 are designed and arranged to generate a monochromatic X-ray beam 240. A fixed aperture may be provided at the distal end of the mirrors 1212, 1214. The fixed aperture is designed to let pass only the monochromatic X-ray beam reflected by the two mirrors 1212, 1214 and to block other X-ray beam portions, such as beam portions that are reflected from a single mirror only (not shown in FIG. 2). The generated X-ray beam 240 has a predetermined cross-sectional size and shape which depends on the design details of the used mirrors 1212, 1214. In the present implementation, only for the purpose of explanation but not of limitation, a mirror arrangement is used generating and outputting a diamond-shaped X-ray beam 240. The beam blocking unit 1300 of the X-ray optical device 110 is arranged at the distal end of the X-ray optics 1210. It comprises the rotatable beam blocking element 1320 and the rotating shaft 1310 on which the beam blocking element 1320 is eccentrically mounted. It further comprises a bearing unit 1340 configured to rotatably support the rotating shaft 1310 and at least one sealing element 1350. The beam blocking unit 1300 is received by casing 1230b fixed at the distal end to the mirror casing 1230a. According to an alternative implementation, the beam blocking unit 1300 can directly received by the mirror housing 1230 at its distal end. The bearing unit 1340 comprises a sleeve 1342 arranged on an upper side of the casing 1230b and configured to receive an upper portion of the rotating shaft 1310. The sleeve 1340 also comprises a recess arranged at the outer sleeve surface and in circumferential direction of the sleeve 1342. The recess 1350 is configured to partially receive a sealing element 1350 (i.e., an O-ring) for providing a gas-tight sealing between sleeve 1340 and casing 1230b. Further, the bearing unit 1340 comprise a bearing recess 144 arranged at a lower side of the casing 1230b and configured to receive the lower end portion of the rotating shaft 1310. The bearing unit 1340 is arranged such that the rotating shaft 1310 is disposed laterally offset to the output beam 240. That, is the rotating shaft 1310 does not overlap with the X-ray beam 240. The beam blocking element 1320 comprises a rotationally symmetric body 1324 arranged eccentrically on the rotating shaft 1310. Further, in axial direction along the rotating shaft 1310, the body 1324 is mounted at the height of the output X-ray beam 240. The body 1324 has the shape of a double cone with truncated apices. Accordingly, the body 1324 has a lateral surface 1326 with an L-shaped lateral contour 1326a defining a beam blocking edge for the output beam 240. In the present implementation, the shape of the beam blocking edge is adapted to the cross-sectional shape of the X-ray beam 240. It represents two sides of the diamond-shaped beam 240 (see also FIGS. 3a and 3b). The operation of the beam blocking unit 1300 of FIG. 3 will be further described in conjunction with FIGS. 3a and 3b. FIGS. 3a and 3b are both side views of the distal end of the X-ray optical device 110 illustrated in FIG. 2. Components of the X-ray optical device 110 having the same structural and/or functional features are provided with the same reference numerals. For the sake of clarity, only the most prominent components have been provided with reference numerals. FIG. 3a illustrates the position in which the beam blocking element 1320 is fully rotated out from the X-ray beam 240. That is, in this position the beam blocking element 1320 does not overlap with the X-ray beam 240. This position corresponds to the above-mentioned minimum overlap position and can be associated with a 0° angular position of the rotating shaft 1310. In this position, the output X-ray beam 240 has its maximum cross-sectional area 240a. By turning the rotating shaft 1310 by 180°, the body 1324 is turned into the X-ray beam 240 so that the lateral contour 1326a of the body continuously moves into the beam 240. As a consequence, the beam cross-sectional area 240a continuously shrinks and becomes minimal at 180° rotation where the maximum overlap position is reached (see FIG. 3b). As already mentioned above, the degree of overlap at the maximum overlap position depends on the design of the beam blocking element 1320, in particular on its lateral extension. In FIG. 3b only a small X-ray portion having a small cross-sectional area 240a can pass through the blocking unit 1300, whereas a major portion of the beam 240 is occluded by the beam blocking element 1320. It is conceivable to dimension the body 1324 such that the beam cross-sectional size 240a is reduced by 80% to 98% with respect to the initial cross-sectional size when reaching the maximum overlap position. Alternatively, it is also conceivable to dimension the body 1324 such that a complete beam blocking is achieved when reaching the maximum overlap position. In order to reduce X-ray scattering at the body surface 1326, the body 1324 is made of a material having excellent X-ray absorption properties. For instance, bronze may be used for the body. With reference to FIGS. 4 and 5 an X-ray optical device 100a according to a further implementation will be discussed. The X-ray optical device 100a comprises the X-ray source 1100, X-ray optics 1200 and aperture device 1300 of the implementation discussed above in conjunction with FIGS. 2, 3a and 3b. These components will not be described again. Instead reference is made to the corresponding description above. Additionally, the X-ray optical device 100a further comprises a driving unit 1400, a sensor unit 1500, a control unit 1600 and an input unit 1700 (see also FIG. 5). The driving unit 1400 comprises an electrical motor 1410 configured to generate a torque. Further, the driving unit 1040 comprises a transmission unit in the form of a belt drive. The belt drive comprises a belt 1420 arranged to transmit the torque generated by the motor 1410 to a pulley 1430 mounted at the upper end of the rotating shaft 1310. The driving unit 1400 is arranged at the upper side of the housing 1230. The sensor unit 1500 is configured to measure the angular position of the rotating shaft 1310 and/or an angular displacement of the rotating shaft 1310 during shaft rotation. For this purpose, an optical sensor may be used which is arranged close to the rotating shaft 1310. The input unit 1700 (only shown in the block diagram of FIG. 6) is configured to receive user inputs. The user input may be indicative of a beam overlap position, rotating angle for the rotating shaft 1310 and/or a beam property, such as the divergence angle 310 of the beam 240. Since these quantities correlate with each other, the control unit 1600 can use each quantity for generating appropriate motor control signals. The control unit 1600 (only shown in the block diagram of FIG. 5) is in communication with the sensor unit 1500, the driving unit 1400 and the input unit 1700. The control unit 1600 may be programmed to determine an actual overlap position of the beam blocking element 1320 (or its lateral edge 1326a) based on the angular position of the rotating shaft 1310 measured by the sensor unit 1500, to compare the actual overlap position with a set overlap position received from the input device 1700, and to generate, based on the comparison, a motor signal that controls the motor 1410 to drive the motor 1410 to an angular position that corresponds to the set overlap position. For this purpose, the controller 1600 comprises at least one processor for processing software routines implementing the above-described control steps. The above-described beam blocking technique has many advantages. The blocking technique can be easily combined with conventional X-ray optics because the rotating shaft 1310 and beam blocking element 1320 can be easily combined with conventional X-ray optics. Further, the blocking technique is mechanically robust and cheap because expensive high precision threads or micrometer screws are not used. Still further, the described technique facilitates the adjustment of a desired overlap position and, therefore, the adjustment of desired beam divergence angles and/or bean intensities because any position between a predefined minimum overlap position and maximum overlap position can easily be selected by simply rotating the rotating shaft in one direction. There is no need to reverse the shaft rotation because the blocking element oscillates between the minimum and maximum overlap position with each new shaft revolution. As a person skilled in the art will readily appreciate, the above description is meant as an illustration of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation, and change, without departing from the spirit of this invention, as defined in the following claims.
	description	1. Field of the Invention The present invention concerns a method to produce x-ray-optical gratings, x-ray-optical gratings and an x-ray system for x-ray dark field imaging and for x-ray phase contrast imaging. 2. Description of the Prior Art It is known to produce an x-ray optical grating as follows. An x-ray-sensitive layer with an electrically conductive cover layer is applied on a base plate and a grating structure is transferred by a lithographic method into the x-ray-sensitive layer, so exposed and unexposed regions are created. The exposed regions of the x-ray-sensitive layer is dissolved so that a grating structure remains; a metal is introduced into the grating interstices by electroplating. A negative imprint of a grating made of metal remains after removing the x-ray-sensitive material and the base plate. A grating made of a first material is produced with this negative imprint, wherein this grating having a number of periodically arranged grating webs and grating openings, and the grating openings are filled by electroplating with a second material. Such a method for the production of x-ray-optical gratings to generate x-ray dark field exposures and x-ray phase contrast exposures is known from DE 10 2006 037 281 A1. The term “x-ray-optical grating” as used herein means a grating that has certain absorption properties with regard to x-ray radiation. Significant technological requirements for such an x-ray-optical grating exist with regard to the precision of the height of the absorbing structures thereof, the aspect ratio, and mechanical stability. Generally such gratings are produced according to a technique known as the LIGA method, from the German acronym for Röntgen-Lithographie, Galvanik, Abformung (x-ray lithography in English). In this procedure, a grating structure is first created in an x-ray-sensitive material via partial exposure with, for example, parallel synchrotron radiation, in which grating structure a metal is introduced by galvanic deposition. After the removal of the x-ray-sensitive material, this metal represents a negative with which a grating is produced from a material with low absorption coefficient. To improve the absorption properties of this grating, the grating openings are filled, by electroplating, with a different material that has a higher absorption coefficient. In the x-ray-optical gratings produced according to the LIGA method, in particular in absorption gratings with a high aspect ratio, a number of parameters (for example the surface roughness, and what is known as the bath temperature) affect the deposition process of the second metal in the electroplating and lead to different growth heights within the grating gaps. The height of the filling between the individual grating webs can vary in some cases by up to 10-20%. These variances lead to a degradation of the measurement signal in x-ray dark field imaging and in x-ray phase contrast imaging, since the bands of generated high and low emission then deliver minima or maxima of different magnitudes that degrades the acquisition quality. An object of the present invention is to provide a method for the production of x-ray-optical gratings for x-ray dark field imaging and for x-ray phase contrast imaging, and such an x-ray-optical grating itself that enable a uniform filling of the grating gaps of a grating with regard to the level of the filling, such that ultimately the quality of the measurement signal is maintained. The invention is based on the insight that it is possible to design the process of electroplating to fill the grating gaps with a material with high absorption coefficient so that the grating structures are deliberately over-plated, so all grating gaps across the entire grating surface are filled with a highly absorbent material to their complete height, and additionally a cohesive and uniform layer of this filling material is created (most importantly with a uniform height) over (atop) the grating webs. It is furthermore advantageous that an improved mechanical stability of the gratings is achieved as a beneficial side-effect, due to the additional cohesion of the grating gaps filled in the electroplating process. In accordance with the invention, the known method for the production of x-ray-optical gratings for x-ray dark field imaging and for x-ray phase contrast imaging is improved by an x-ray-sensitive layer with an electrically conductive cover layer being applied on a base plate, and a grating structure is transferred into the x-ray-sensitive layer by a lithographic method so exposed and unexposed regions are created, and the exposed regions of the x-ray-sensitive layer are dissolved so that a grating structure remains, and a metal is introduced into the grating interstices by electroplating, and after removing the x-ray-sensitive material and the base plate, a negative impression of a grating made of metal remains, and a grating made of a first material is produced with this negative impression, this grating having a number of periodically arranged grating webs and grating spacings (openings) and the grating gaps are filled with a second material by electroplating, with the electroplating being continued until a cohesive layer of the second material is created over the grating webs. With regard to the absorption properties of the grating, it is advantageous for the x-ray absorption coefficient of the first material to be lower than the x-ray absorption coefficient of the second material. Different absorption coefficients in an x-ray-optical grating are a basic requirement for the function of such a grating since, upon irradiation of such a grating with x-ray radiation, differentiation should be made between radiation that has traversed the first material and radiation that has traversed the second material. In an embodiment of the invention, the over-plated layer is produced to a uniform height, for example by polishing. Although, with regard to its absorption properties, the very thin layer can nearly be disregarded in comparison to the primary structures (grating webs and grating gaps), an exact, uniform, thickness-dependent absorption value results for the coated grating, whereby the absorption properties given a uniform height over the entire surface of the layer can be reproduced. This is particularly beneficial when many of these gratings (approximately 50 to 100) are mounted together on a CT detector and detect the measurement signals together. The layer thickness is thereby advantageously at least 5 μm, advantageously at least 10 μm. An additional advantage of the layer is the increased mechanical strength the results therefrom. This is particularly advantageous if the gratings are used in a detector. In CT apparatuses of the 3rd generation with rotating detector, centrifugal forces between 20 and 40 g arise to which the gratings are exposed, and a strong mechanical stability is required. The use of a plastic as a first material, advantageously polymethacrylate (PMMA) or an epoxy resin, has proven to be advantageous. These materials have a desired low x-ray absorption coefficient and are simple to handle in terms of their processing. Furthermore, epoxy resin in particular is very x-ray-insensitive. Furthermore, it is advantageous to use a metal as a second material, advantageously gold or nickel. Metals are well suited for galvanic processing and possess a relatively high x-ray absorption coefficient. Good knowledge of the use of gold exists especially in microsystem production processes. The described method is particularly suitable for gratings with a high aspect ratio. The aspect ratio is calculated from the ratio of the height of the grating to the period of the grating, wherein what is described with grating height is the height of the grating spacings and webs, and a period corresponds to the width of a grating web and a grating spacing together. It is primarily sought to achieve a high aspect ratio via an optimally large height of the grating, and this affects the absorption of the x-ray radiation traversing the grating since this is dependent on the layer thickness. For a given grating period, a high aspect ratio results in significant differences between the absorption maxima and minima so that after the grating the desired large differences arise in the intensity of the x-ray radiation exiting there. The method according to the invention advantageously concerns x-ray-optical gratings that are constructed from two different materials, wherein the first material forms grating webs arranged in parallel which are connected at one end of the grating webs with one another via a flat substrate layer made from the first material, and grating spacings (openings) exist between the grating webs. Furthermore, the second material advantageously likewise forms grating webs which are arranged in the grating opening of the first material and are connected with one another by a cover layer made of the second material on the side of the grating facing away from the substrate layer. The arrangement of the grating webs advantageously ensues so that the grating webs of the second material are fit exactly into the grating openings of the first material, and the grating webs of the first material are fit exactly into the grating openings of the second material. It is advantageous to produce the x-ray-optical grating according to the method described above, namely to attach an x-ray-sensitive layer with an electrically conductive cover layer on a base plate, afterward to transfer a grating structure into the x-ray-sensitive layer via a lithographic method, wherein exposed and unexposed regions are created and the exposed regions of the x-ray-sensitive layer are dissolved so that a grating structure remains. A metal can subsequently be introduced into the grating interstices via electroplating so that a negative impression of a grating made of metal remains after removal of the x-ray-sensitive material and the base plate, and a grating made from a first material can be produced with this negative impression. In an advantageous embodiment of an x-ray system with a radiator/detector system for projective or tomographical x-ray dark field imaging and/or x-ray phase contrast imaging, at least one of the gratings used there is produced according to the method according to the invention. FIG. 1 shows a conventional x-ray-optical grating 1 that was produced according to the LIGA method. An x-ray-sensitive layer—this is for the most part a plastic such as polymethacrylate, abbreviated as PMMA—is applied on a base plate. A grating structure is subsequently transferred via lithographic exposure with, for example, parallel synchrotron radiation. Exposed and unexposed regions are hereby created, wherein the exposed regions are subsequently dissolved. In the next step, a metal is filled into the grating openings (spacings) by electroplating. In an electrolytic bath, a voltage is thereby applied between the grating and an anode made of the metal to be plated. By electrolysis, metal ions detach from the anode and deposit by reduction on the cathode, to produce the grating. This is continued until a complete negative impression of a grating has been created. With the use of this negative impression, the grating 1 with periodically arranged grating webs 4 and grating gaps 5 is produced from a first material 2. A second material 3 is visible in the grating gaps 5 of the grating gap 1. This material is likewise introduced via electroplating. Extremely small structures can be filled with a material via this technique. The deposition or accumulation of the metal ions thereby depends on multiple parameters, for example the bath temperature and the surface roughness of the grating material. In these known methods it is disadvantageous that the height of the electroplated material can thereby vary by 10% to 15% of the total height. These variances in the height of the second material 3 are also visible in the example shown here, meaning that the surface of the second material 3 in the grating gaps 5 does not always correspond to the height 6 of the surface of the grating 1. If such a grating is used as a source grating in a Talbot interferometer, corresponding differences in the absorption maxima and minima of the passing x-ray radiation that are formed by the grating also arise in a disadvantageous manner due to the different heights of the second material, so disadvantageous interference conditions (and therefore imprecise measurement signals) are generated. A grating 1 according to FIG. 1 with grating gaps 5 filled according to the invention is visible in FIG. 2, wherein a continuous layer of the filling material 3 is applied over the grating webs 4. For this purpose, the electroplating is conducted first until the grating gaps are filled and subsequently until the layer is created. In principle, a strong homogenization of the filling material is achieved solely via this overfilling of the grating gaps. According to the invention, this layer can additionally be brought to an additionally homogenized level 7 via polishing. The height 7 of the layer of the second material is thereby significantly smaller than the height 6 of the grating 1. The layer can thereby be disregarded in terms of its absorption properties. The low level 7 (which is uniform over the entire area of the grating 1) is advantageous if many gratings (for example approximately 50 to 100) are mounted together in a detector of a CT system. With the described method, a height of the absorbing structures (advantageously gold structures) that is uniform over the entire grating area is achieved in the first place. The reproducibility of the absorption properties of the grating that is thus obtained is particularly helpful if many of these gratings (for example approximately 50-100) are mounted together on a CT detector and generate the measurement signals together. Furthermore, the mechanical strength of the grating is significantly increased. In the case of the installation of the grating in a CT gantry, the gratings are exposed to strong acceleration forces (approximately 20-40 g) during the acceleration of the CT gantry, which can lead to the destruction of the grating structures. The described over-plating leads to an increase of the mechanical stability of the grating webs, and thus of the entire grating composite. FIG. 3 shows, as an example, an x-ray CT system with a radiator/detector system for projective or tomographical x-ray dark field imaging and/or x-ray phase contrast imaging a schematic 3D representation of a radiator/detector system of a CT apparatus. The gratings used here are of a source grating G0 to generate a bundle of quasi-coherent rays, the phase grating G1 to deflect the rays of the beam and generate interferences, and the analysis grating G2 directly before the detector D to determine phase shifts and scatter ratios. A sample P as an examination subject is arranged in the beam path. The focus F and the detector D are arranged on a gantry (not shown in detail here) and move in an orbit around the system axis S (represented as a dash-dot line). According to the invention, at least one of the gratings G0, G1 or G2 (advantageously at least the source grating G0 fashioned as an absorption grating) is produced according to the method described above. A predominantly homogeneous field of quasi-coherent radiation is hereby generated so that the interferences that are generated by the phase grating G1 can be optimally detected with measurement technology. As a whole, an improvement of a method to produce x-ray-optical gratings, an x-ray-optical grating and an x-ray system is thus proposed with the invention, wherein these gratings consisting of a first material possess a plurality of periodically arranged grating webs and grating gaps, and the grating gaps are filled with a second material via electroplating. According to the invention, the electroplating is continued until a cohesive layer of the second material with uniform height is created over the grating webs. The absorption properties of the grating structure of the grating are homogenized via this layer with a large absorption coefficient, whereby an improvement of the measurement signal that is generated with this is produced. Moreover, the mechanical stability of gratings produced in this way is improved. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
	description	This application is related to a co-assigned U.S. Patent Publication No. 2007/0295012, entitled “Nitrogen Enriched Cooling Air Module for UV Curing System,” filed on Nov. 3, 2006 and assigned to Applied Materials, the assignee of the present application. The entire contents of the related applications are hereby incorporated by reference for all purposes. The present invention relates generally to methods and apparatus of semiconductor manufacturing process. More particularly, the invention provides methods and apparatus for excimer curing. Materials such as silicon oxide (SiOx), silicon carbide (SiC) and carbon doped silicon oxide (SiOCx) films find widespread use in the fabrication of semiconductor devices. One approach for forming such silicon-containing films on a semiconductor substrate is through the process of chemical vapor deposition (CVD) within a chamber. For example, chemical reaction between a silicon supplying source and an oxygen supplying source may result in deposition of solid phase silicon oxide on top of a semiconductor substrate positioned within a CVD chamber. As another example, silicon carbide and carbon-doped silicon oxide films may be formed from a CVD reaction that includes an organosilane source including at least one Si—C bond. Water is often a by-product of the CVD reaction of organosilicon compounds. As such, water can be physically absorbed into the films as moisture or incorporated into the deposited film as Si—OH chemical bond. Either of these forms of water incorporation are generally undesirable. Accordingly, undesirable chemical bonds and compounds such as water are preferably removed from a deposited carbon-containing film. Also, in some particular CVD processes, thermally unstable organic fragments of sacrificial materials need to be removed. One conventional method used to address such issues is a thermal anneal. The energy from such an anneal replaces unstable, undesirable chemical bonds with more stable bonds characteristic of an ordered film thereby increasing the density of the film. Conventional thermal anneal steps are generally of relatively long duration (e.g., often between 30 min to 2 hrs) and thus consume significant processing time and slow down the overall fabrication process. Another technique to address these issues utilizes ultraviolet radiation to aid in the post treatment of CVD silicon oxide, silicon carbide and carbon-doped silicon oxide films. The use of UV radiation for curing and densifying CVD films can reduce the overall thermal budget of an individual wafer and speed up the fabrication process. A number of various UV curing systems have been developed which can be used to cure films deposited on substrates. Usually, an UV curing system has either mercury vapor lamps or metal halide doped mercury lamps powered by microwave generator. UV lamps generate light across a broad band of wavelengths from 170 nm to 600 nm. However, UV lamps usually have a short lifetime and provide low output of radiation at wavelength less than about 400 nm. Furthermore, particularly at wavelength less than 250 nm, the power output of UV lamps declines with the increasing use of the UV lamps. Accordingly, improvements to existing UV curing systems and methods are desirable. Embodiments of the present invention pertain to apparatuses that provide benefits over previously known processes and apparatuses by employing an excimer lamp to excite an inert gas to illuminate an excimer light having a narrow range of bandwidth, such as 152 nm, 172 nm, 193 nm, 222 nm, 248 nm or 303 nm, for curing dielectric materials. The excimer light can have a desired power to cure dielectric materials even if its wavelength is under about 250 nm. One embodiment of the invention provides an apparatus for generating excimer radiation. The apparatus includes a housing having a housing wall. An electrode is configured within the housing. A tubular body is around the electrode. The tubular body includes an outer wall and an inner wall. At least one inert gas is between the outer wall and the inner wall, wherein the housing wall and the electrode are configured to excite the inert gas to illuminate an excimer light for curing. Another embodiment provides an apparatus for excimer curing dielectric material. The apparatus includes a chamber defining a substrate processing region. A substrate support is configured within and at a bottom region of the chamber. At least one excimer lamp is separated from the substrate support and configured to generate and transmit radiation to a substrate positioned over the substrate support. Each of the at least one excimer lamp includes an electrode. A tubular body is configured around the electrode. The tubular body includes an outer wall and an inner wall. At least one inert gas is between the outer wall and the inner wall. A reflector is adjacent to the outer wall of the tubular body, wherein the reflector and the electrode are configured to excite the inert gas to illuminate an excimer light for curing. The other embodiment provides a method for excimer curing a dielectric material over a substrate. The substrate is disposed within a chamber having a chamber wall and an excimer lamp disposed within the chamber. The method includes applying a voltage drop between the chamber wall and the excimer lamp to excite an inert gas within the excimer lamp to illuminate an excimer light to cure the dielectric material. These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. The present invention relates to apparatus for curing dielectric materials such as low-k dielectric material, spin-on-glass (SOG), or other dielectric materials deposited over substrate, such as silicon wafers, liquid crystal display substrates, solar panel substrates, and others. The apparatus excites an inert gas to illuminate an excimer light having a narrow range of bandwidth, such as 152 nm, 172 nm, 193 nm, 222 nm, 248 nm or 303 nm, for curing dielectric materials. The excimer light can have a desired power to cure dielectric materials even if its wavelength is under about 250 nm. The apparatus includes a chamber having a chamber wall. An electrode is configured within the chamber. A tubular body is around the electrode. The tubular body includes an outer wall and an inner wall. At least one inert gas is between the outer wall and the inner wall, wherein the chamber wall and the electrode are configured to excite the inert gas to illuminate an excimer light for curing. FIG. 1 is a simplified plan view of a semiconductor processing system 100 in which embodiments of the invention may be incorporated. System 100 illustrates one embodiment of a Producer processing system, commercially available from Applied Materials, Inc., of Santa Clara, Calif. Processing system 100 is a self-contained system having the necessary processing utilities supported on mainframe structure 101. Processing system 100 generally includes front end staging area 102 where substrate cassettes 109 are supported and substrates are loaded into and unloaded from loadlock chamber 112, transfer chamber 111 housing substrate handler 113, a series of tandem process chambers 106 mounted on transfer chamber 111 and back end 138 which houses the support utilities needed for operation of system 100, such as gas panel 103 and power distribution panel 105. Each of tandem process chambers 106 includes two processing regions for processing the substrates. The two processing regions share a common supply of gases, common pressure control and common process gas exhaust/pumping system. Modular design of the system enables rapid conversion from any one configuration to any other. The arrangement and combination of chambers may be altered for purposes of performing specific process steps. Any of the tandem process chambers 106 can include a lid according to aspects of the invention as described below that includes one or more excimer lamps for use in a cure process of a low K material on the substrate and/or in a chamber clean process. In one embodiment, all three of the tandem process chambers 106 have excimer lamps and are configured as excimer curing chambers to run in parallel for maximum throughput. In an alternative embodiment where not all of tandem process chambers 106 are configured as excimer curing chambers, system 100 can be adapted with one or more of the tandem process chambers having supporting chamber hardware as is known to accommodate various other known processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, and the like. For example, system 100 can be configured with one of tandem process chambers 106 and a CVD chamber for depositing materials, such as a low dielectric constant (K) film, on the substrates. Such a configuration can maximize research and development fabrication utilization and, if desired, eliminate exposure of as-deposited films to atmosphere. FIG. 2 is a simplified perspective view of one of tandem process chambers 106 shown in FIG. 2 that is configured for excimer curing. Tandem process chamber 106 includes body 200 and lid 202 that can be hinged to body 200. Coupled with lid 202 are two housings 204 that each includes inlets 206 along with outlets 208 for passing cooling air through an interior of housings 204. The cooling air can be at room temperature or approximately twenty-two degrees Celsius. A central pressurized air source (not shown) provides a sufficient flow rate of air to inlets 206 to insure proper operation of any excimer lamp bulbs and/or associated power sources for the bulbs. Outlets 208 receive exhaust air from the housings 204. Unlike a conventional UV curing lamp, the excimer lamps do not use ozone. Accordingly, ozone management issues can be avoided. Details of a cooling module that can be used in conjunction with tandem process chamber 106 can be found in U.S. Patent Publication No. 2007/0295012, entitled “Nitrogen Enriched Cooling Air Module for UV Curing System,” filed on Nov. 3, 2006 and assigned to Applied Materials, the assignee of the present application. The 2007/0295012 application is hereby incorporated by reference in its entirety. Each housing 204 includes upper housing 210 in which an excimer lamp (not shown) is placed and lower housing 214 in which a secondary reflector (not shown) is placed. Some embodiments of the invention further include disc 212 having a plurality of teeth 212a that grip a corresponding belt (not shown) that couples disc 212 to spindle 216 which in turn is operatively coupled with a motor (not shown). The combination of discs 212, belts, spindle 216 and motor allow upper housings 210 (and the excimer lamps mounted therein) to be rotated relative to a substrate positioned on substrate support below lid 202. FIG. 3 shows a partial section view of the tandem process chamber 106 with lid 202, housings 204 and power sources 303. Each of housings 204 covers a respective one of two excimer lamps 302 disposed respectively above two process regions 300 defined within body 200. Each of process regions 300 includes heating pedestal 306 for supporting substrate 308 within process regions 300. Pedestals 306 can be made from ceramic or metal such as aluminum. Some embodiments, pedestals 306 couple to stems 310 that extend through a bottom of body 200 and are operated by drive systems 312 to move pedestals 306 in processing regions 300 toward and away from excimer lamps 302. Drive systems 312 can also rotate and/or translate pedestals 306 during curing to further enhance uniformity of substrate illumination. Adjustable positioning of pedestals 306 enables control of volatile cure by-product and purge and clean gas flow patterns and residence times in addition to potential fine tuning of incident excimer irradiance levels on substrate 308 depending on the nature of the light delivery system design considerations such as focal length. In general, embodiments of the invention contemplate any excimer source such as pulsed helium, neon, argon, krypton or xenon flash lamps that can generate radiation with wavelength specifically at, for example, 152 nm, 172 nm, 193 nm, 222 nm, 248 nm or 303 nm. Excimer lamps 302 are filled with one or more gases such as helium, neon, argon, krypton or xenon for excitation by power sources 303. Preferably, power sources 214 are radio frequency (RF) generators. The RF generators can generate frequency between about 50 kHz and about 180 MHz. In one embodiment, each of housings 204 includes aperture 305 adjacent to power sources 303 to receive an RF power from power sources 303. Excimer lamps 302 can emit an excimer light having a narrow range of bandwidth, such as about 152 nm, 172 nm, 193 nm, 222 nm, 248 nm or 303 nm. The gases selected for use within excimer lamps 302 can determine the wavelengths emitted. Unlike a conventional UV lamp that emits an UV light having a broadband of wavelengths from 170 nm to 400 nm, excimer lamps 302 can emit light having a narrow range of bandwidth corresponding to bonding energies of silicon-silicon (Si—Si), silicon-oxygen (Si—O), silicon-nitrogen (Si—N) and/or silicon-carbon (Si—C) so as to cure dielectric material, such as oxide, nitride, oxynitride, carbide-containing dielectric material, or other dielectric material. Excimer lamps 302 can provide desired power output at wavelengths lower than about 400 nm for curing dielectric materials. By using the excimer lamp, curing dielectric material such as low-k dielectric material can be more desirably achieved. In embodiments, the distance between excimer lamps 302 and substrate 308 can be between about 1 mm and about 200 mm. In other embodiments, the distance can be between about 1 mm and about 60 mm. Light emitted from excimer lamps 302 enters processing regions 300 by passing through windows 314 disposed in apertures in lid 202. Windows 314 can be made of an OH free synthetic quartz glass and have sufficient thickness to maintain vacuum without cracking. Further, windows 314 can be fused silica that transmits light down to approximately 150 nm. Processing or cleaning gases enter process regions 300 via a respective one of two inlet passages 316. The processing or cleaning gases then exit process regions 300 via common outlet port 318. Additionally, the cooling air supplied to the interior of housings 204 circulates past excimer lamps 302, but is isolated from process regions 300 by windows 314. In one embodiment, each of housings 204 includes an interior parabolic surface defined by cast quartz lining 304 coated with a dichroic film. Quartz linings 304 reflect light emitted from excimer lamps 302 and are shaped to suit both the cure processes as well as the chamber clean processes based on the pattern of excimer light directed by quartz linings 304 into process regions 300. For some embodiments, quartz linings 304 adjust to better suit each process or task by moving and changing the shape of the interior parabolic surface. Additionally, quartz linings 304 can desirably transmit light emitted by excimer lamps 302 due to the dichroic film. The dichroic film usually constitutes a periodic multilayer film composed of diverse dielectric materials having alternating high and low refractive index. Since the coating is non-metallic, microwave radiation from power sources 303 that is downwardly incident on the backside of cast quartz linings 304 does not significantly interact with, or get absorbed by, the modulated layers and is readily transmitted for ionizing the gas in excimer lamps 302. In embodiments, rotating or otherwise periodically moving quartz linings 304 during curing and/or cleaning enhances the uniformity of illumination in the substrate plane. In yet another embodiment, entire housings 204 rotate or translate periodically over substrate 308 while quartz linings 304 are stationary with respect to excimer lamps 302. In still another embodiment, rotation or periodic translation of substrate 308 via pedestals 306 provides the relative motion between substrate 308 and excimer lamps 302 to enhance illumination and curing uniformity. For cure processes, pedestals 306 are heated to between about 100° C. and about 1,100° C., preferably about 300° C. and about 750° C. The pressure within processing regions 300 can be between about 500 micron Torr (μTorr) and about 500 Torr, preferably between about 500 mTorr and about 5 Torr in order to desirably cure substrate 308. During the curing treatment, pedestals 306 can rotate substrate 308 between about 1 rotate per minute (rpm) and about 300 rpm to uniformly expose substrate 308 to light generated from excimer lamps 302. FIG. 4A is a schematic cross-sectional view of an exemplary excimer lamp configured at a sidewall of a housing according to an embodiment of the present invention. FIG. 4B is a schematic cross-sectional view of the example excimer lamp of FIG. 4A along section line 4B-4B. In FIG. 4A, excimer lamp 302 includes electrode 410, reflector 420, and tubular body 400. Tubular body 400 is around electrode 410. Tubular body 400 includes outer wall 402 and inner wall 404. At least one inert gas such as He, Ne, Ar, Kr and Xe is filled and sealed between inner wall 404 and outer wall 402. Reflector 420 is configured adjacent to outer wall 402 of tubular body 400. Reflector 420 can be substantially grounded, and electrode 410 can be coupled with RF power source 303 (shown in FIG. 3) to excite inert gas 406 to emit an excimer light having a narrow range of bandwidth for curing. Tubular body 400 is configured through sidewall 430 of the housing. Brazed vacuum flanges 450 attached to the tubular body 400 are configured between sidewall 430 and lamp clamps 440. O-ring 460 is configured within a groove of sidewall 430 to desirably seal the housing and/or maintain the pressure within the housing. It is noted the shape of tubular body 400 is not limited to that as shown in FIG. 4A. Tubular body 400 can have any shape that can desirably accommodate electrode 410. Excimer lamp 302 can excite the inert gas to illuminate excimer light by applying a high voltage to electrode 410 and substantially grounding reflector 420 and/or housing sidewall 430. The excimer light can cure dielectric materials, such as low-k dielectric materials, to desirably remove moistures and densify the dielectric materials. In embodiments, wire 410a coupled with electrode 410 is configured within tubular body 400 and is free from being exposed within tandem process chamber 106. The configuration can desirably prevent generation of plasma within tandem process chamber 106 due to the high voltage applied to wire 410a and substantially grounded housing sidewall 430. Additionally, a pressure is provided in the space between electrode 410 and inner wall 404 of tubular body 400. The pressure is provided such that plasma is substantially free from being generated within the space when electrode 410 and reflector 420 and/or sidewall 430 are configured to generate the excimer light. The pressure can be, for example, about an atmosphere pressure, and different from the pressure within housing 204 (shown in FIG. 3). In FIG. 4B, reflector 420 can be substantially semi-cylindrical around outer wall 402 of tubular body 400. Reflector 420 can desirably reflect excimer light emitted from excimer lamp 302. Reflector 420 can be substantially grounded. One of ordinary skill in the art can modify reflector 420 to cover outer wall 402 to generate a desired radiation for curing. FIG. 5A is a schematic cross-sectional view of an exemplary excimer lamp configured at a sidewall of a housing according to an embodiment of the present invention. FIG. 5B is a schematic cross-sectional view of the exemplary excimer lamp of FIG. 5A along section line 5B-5B. In FIG. 5A, another exemplary excimer lamp 302a is provided. Partition walls 403 contact inner wall 404 and outer wall 402. Partition walls 403 separate area 405 adjacent to one end of tubular body 400 from other area 407 adjacent to the other end of tubular body 400. Inert gas 406 is filled and sealed within area 405. It is optional that gas such air or other gas can be filled and/or sealed in area 407. Partition walls 403 may be substantially adjacent to sidewall 430 of the housing. Partition walls 403 of excimer lamp 302a separate area 407 from area 405. Gas other than inert gas can be filled within area 407. During exciting inert gas 406 in area 405, no substantially excimer light is generated from the gas in area 407. O-ring 460 can be desirably free from being subjected to excimer light from area 407. The life span of O-ring 460 can be more desirably extended. O-rings 460 can desirably seal the housing. FIG. 6A is a schematic cross-sectional view of an example excimer lamp configured at a sidewall of a housing according to another embodiment of the present invention. FIG. 6B is a schematic cross-sectional view of the example excimer lamp of FIG. 6A along section line 6B-6B. In FIG. 6A, the other exemplary excimer lamp 302b is provided. Excimer lamp 302b has dielectric material area 407a such as glass and/or any solid dielectric material. The use of brazed vacuum flange 450 (shown in FIGS. 4A and 5A) is optional if sidewall 430 can desirably hold excimer lamp 302b. O-rings 460 are configured within grooves of the housing wall and between tubular body 400 and the housing wall. With dielectric material area 407a, no excimer light can be generated from solid dielectric material area 407a when excimer lamp 302b generates an excimer light. In addition, sidewall 430 can substantially block excimer light generated from inert gas 406 within area 405. O-rings 460 is not subjected any excimer light from solid dielectric material area 407a. Accordingly, O-rings 460 can be desirably prevented from being damaged during the excimer curing process. The life span of O-rings 460 can be more desirably extended and O-rings 460 can desirably seal the housing. FIG. 7A is a schematic cross-sectional view of an example excimer lamp configured at a sidewall of a housing according to still another embodiment of the present invention. FIG. 7B is a schematic cross-sectional view of the example excimer lamp of FIG. 7A along section line 7B-7B. In FIG. 7A, an exemplary excimer lamp 302c is provided. In FIG. 7A, excimer lamp 302c has inner wall 404, which is separated from outer wall 402 at the region adjacent to end 415 of tubular body 400. When sidewall 430 is substantially grounded or floating for generating excimer light, electrode 410 and sidewall 430 can substantially excite the inert gas between inner wall 404 and outer wall 402. The gap between outer wall 402 and inner wall 404 at the region adjacent to end 415 can desirably prevent generating plasma by electrode 410 and sidewall 430 within the chamber. FIGS. 8-10 are schematic drawings showing exemplary configurations of excimer lamps within a housing. In FIG. 8, excimer lamps 302 are substantially parallel configured within the housing. One end of each of excimer lamps 302 is configured through sidewall 430a and the other end of each of excimer lamps 302 is distant from sidewall 430b. In embodiments, excimer lamps 302 may be configured adjacent to the center of the housing. The number of excimer lamps 302 shown in FIG. 8 is merely exemplary. The scope of the invention is not limited thereto. One or more than two excimer lamps 302 can be configured within the housing if the housing can accommodate the number of excimer lamps 302. In embodiments, the number of excimer lamps 302 can be between about 2 and about 12. Excimer lamps 302 and 302a-302c described above in conjunction with FIGS. 4A, 5A, 6A, and 7A can be optionally used. In FIG. 9, both ends of each of excimer lamps 302 are configured through sidewalls 430a and 430b. Since each end of excimer lamps 302 is not configured within the chamber, ends of electrodes 410 within each of the excimer lamps 302 and sidewalls 430a and 430b do not generate plasma within chamber. The configuration of lamps 302 in FIG. 9 can desirably prevent ionizing gas in the chamber. In embodiments, excimer lamps 302 and 302a-302c described above in conjunction with FIGS. 4A, 5A, 6A, and 7A can be optionally used. In FIG. 10, excimer lamps 302d-302i can be configured with a substantially same space between each other along housing wall 430. For example, excimer lamps 302d-302i are configured such that one end of excimer lamp 302d substantially faces one end of excimer lamp 302g, one end of excimer lamp 302e substantially faces one end of excimer lamp 302h, and one end of excimer lamp 302f substantially faces one end of excimer lamp 302i. Excimer lamps 302d-302i can be any one of excimer lamps 302 and 302a-302c described above in conjunction with FIGS. 4A, 5A, 6A, and 7A. Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention. Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a method” includes a plurality of such methods and reference to “the precursor” includes reference to one or more precursors and equivalents thereof known to those skilled in the art, and so forth. Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.
	abstract	A thermal solar rocket that includes a solar energy receiver having two sections (a thermal energy storage section and a direct gain section), a solar concentrator, and a propulsion nozzle. In one embodiment, the focus of the solar energy between the storage section and the direct gain section is controlled by mechanical means such as movable insulation. In another embodiment, the focus of the solar energy between the storage section and the direct gain section is controlled by an optical switch in the form of relative motion between the solar concentrator and the solar energy receiver.
050013513	summary	The invention relates to an object holder for positioning an object in a radiation beam, comprising an X-Y translation mechanism. In known object holders an X-Y translation mechanism is constructed so that an X-transporter for translation in an X-direction carries a carriage for translation across the X-transporter in an Y-direction, the X-transporter acting as a reference and supporting face for the Y-transporter or vice versa. This results in a comparatively complex translation mechanism where errors in the second translation constitute a sum of errors in both translation systems and where an undesirable rotary movement and tilting can readily occur during the last translation motion. This is understandable because, considering the desirable low-friction movements, it is difficult to prevent a given play for each of the guides. This is extremely undesirable, however, in object carriers where angular orientation of an object is co-decisive for the accuracy of measurements to be performed. It is the object of the invention to mitigate these drawbacks. In accordance with the present invention each of two translatory movements separately refers directly to a supporting face of a supporting plate in a translation mechanism. A simple and inexpensive movement mechanism exhibited extremely accurate positioning, notably because of a force coupling, which minimizes undesirable rotation and tilting. In a preferred embodiment in accordance with the invention the pressure exerted towards the supporting plate is realized by a magnetic force of attraction, by means of permanent magnets, for example, which are coupled to an X-transporter and to a support for the object table, which magnets preferably bear on the supporting face of the supporting plate via an intermediate spacer which are preferably ductile to some extent. In addition to a smooth sliding contact, a desirable air gap is thus also achieved. In a further preferred embodiment, a rotation of the object table is added to the X-Y translation; this is comparatively simply achieved by mounting the supporting plate so as to be rotatable about an axis extending transversely of its supporting face. Driving can be realized by mounting a motor-driven rotation mechanism on a rear side of the supporting plate (with respect to the object table), the axis of rotation preferably extending through the centre of a substantially circular supporting plate. An object tilting mechanism for tilting the supporting face of the supporting plate can also be added to the supporting plate. If the angles of tilt need not be very large, for example no more than approximately plus and minus 10.degree., use can be made of a shaft in the form of a cylindrical bush which is partly open in the lateral direction, so that at that area a free passage is realized for a radiation beam extending parallel to the supporting plate.
	claims	1. A nuclear fuel assembly having a top end fitting and a bottom end fitting connected together by a structural assembly having an axial dimension that extends from the bottom end fitting to the top end fitting, the top end fitting having a spring assembly projecting above an upper surface of the top end fitting, the spring assembly comprising:a primary spring member extending above the top end fitting, including a first straight leg portion extending from a point of attachment proximate one end of the primary spring member with the one end attached to a frame of the top end fitting at an acute angle to a plane orthogonal to the axial dimension, with the acute angle greater than zero degrees, an arcuate transition portion at the other end of the first leg, and a straight second leg portion extending from the transition portion toward the frame at an acute included angle with the first leg, the primary spring member being oriented on the top end fitting so that the transition portion is at the vertical highest elevation, whereby movement of the end fitting and an upper plate of a reactor that the nuclear fuel assembly is designed to operate in, relatively toward each other primarily loads the transition portion and deflects the first leg portion about the attachment to the top end fitting frame;at least one secondary spring having a first and second end, the first end attached to the top end fitting adjacent the first end of the primary spring first leg, and the second end terminating adjacent the transition portion, and means at the second end of the secondary spring for interacting with the transition portion to resist downward movement of the transition portion as the primary spring member deflects in a cantilever fashion;wherein the one end of the primary spring that is attached to the frame of the top end fitting is clamped on a first portion of a surface on the frame that extends substantially at the acute angle, a periphery of the first portion of the surface of the frame under the primary spring being radiused to transition to a second portion of the surface of the frame under the primary spring that extends substantially parallel to the plane orthogonal to the axial dimension; andwherein the at least one secondary spring has a substantially flat leg that extends from the first end to an intermediate portion near the second end where, in an undeflected state, the flat leg is radiused in the direction of the frame away from the primary spring so that the secondary spring substantially contacts an underside of the primary spring over more than a half of a length of the secondary spring and a gap exists between the primary spring and the secondary spring at the transition portion of the primary spring. 2. The nuclear fuel assembly of claim 1 wherein the one end of the primary spring that is attached to the frame of the top end fitting is supported in a slot in the frame that extends substantially at the acute angle. 3. The nuclear fuel assembly of claim 1 wherein the radiused intermediate portion is curved at between 10° and 70°. 4. The nuclear fuel assembly of claim 1 wherein the one end of the first straight leg portion of the primary spring member is attached to the frame of the top end fitting by a retaining pin or screw. 5. The nuclear fuel assembly of claim 1 wherein the periphery of the first portion of the surface of the frame under the primary spring that is radiused is curved at between 10° and 70°.
051739305	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to monochromators. 2. Prior Art Monochromators which can produce a monochromatic beam with narrow spectral wavebands are known. Such beams are very useful in the testing and calibrating of x-ray telescopes and microscopes, in research in biological and biomedical disciplines, in research in properties of materials and processing etc. Previous monochromators have used metal foil filters, gratings, or crystals. Metal foil monochromators have the advantage of a high throughput but do not have the narrow bandwidth needed for some applications. Much higher spectral resolution is possible with the use of crystal or grating monochromators but these have other disadvantages. Natural crystal monochromators are suitable for hard x-ray use and even some of the shorter wavelengths in the soft x-ray wavelengths but the crystal lattice structure in naturally occurring crystals is too small to permit observations in the longer wavelength soft x-ray/EUV regimes. Grating monochromators are capable of covering the soft x-ray/EUV portions of the electromagnetic spectrum, which is the concern of the present invention, but they have a very low throughput. In addition, grating monochromators are difficult to fabricate, align and maintain in optical alignment. Also, grating monochromators are typically large and expensive. SUMMARY OF THE INVENTION An x-ray monochromator wherein a plurality of parallel pairs of facing mirrors are mounted in a housing having therein an inlet window and an outlet window for each pair of mirrors. Each pair of facing mirrors is coated with identical multilayer coatings which reflect x-rays at a wavelength which is dependent on the angle of incidence of the x-rays on the mirror and the nature of the multilayer coating, with different pairs of facing mirrors having different multilayer coatings such that each pair of facing mirrors has a peak reflection of x-rays at a different wavelength. The mirrors are pivotally mounted in a row in the housing and are interconnected so that all of the mirrors pivot at the same time and amount so that the mirror surfaces always remain parallel to each other. The housing is moveable so that any pair of mirrors can be moved into position to intercept a x-ray beam traveling along a fixed path through the inlet window associated with that pair of mirrors to thereby provide a monochromatic x-ray beam of a desired wavelength.
	abstract	Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.
	description	The present application is related to and claims the benefit of the earliest available effective filing date from the following listed application (the “Related Application”) (e.g., claims benefits under 35 USC §119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc. applications of the Related Application). For purposes of the USPTO extra-statutory requirements, the present application claims benefit of priority of U.S. Provisional Patent Application No. 61/280,370 , entitled TRAVELING WAVE NUCLEAR FISSION REACTOR FUEL SYSTEM AND METHOD, naming Charles E. Ahlfeld, Thomas M. Burke, Tyler S. Ellis, John Rogers Gilleland, Jonatan Hejzlar, Pavel Hejzlar, Roderick A. Hyde, David G. McAlees, Jon D. McWhirter, Ashok Odedra, Robert C. Petroski, Nicholas W. Touran, Joshua C. Walter, Kevan D. Weaver, Thomas Allan Weaver, Charles Whitmer, Lowell L. Wood, Jr., and George B. Zimmerman as inventors, filed Nov. 2, 2009 , which was filed within the twelve months preceding the filing date of the present application or is an application of which a currently co-pending application is entitled to the benefit of the filing date. The United States Patent Office (USPTO) has published a notice to the effect that the USPTO's computer programs require that patent applicants reference both a serial number and indicate whether an application is a continuation or continuation-in-part. Stephen G. Kunin, Benefit of Prior-Filed Application, USPTO Official Gazette Mar. 18, 2003 , available at http://www.uspto.gov/web/offices/com/sol/og/2003/week11/patbene.htm. The present Applicant Entity (hereinafter “Applicant”) has provided above a specific reference to the application(s) from which priority is being claimed as recited by statute. Applicant understands that the statute is unambiguous in its specific reference language and does not require either a serial number or any characterization, such as “continuation” or “continuation-in-part,” for claiming priority to U.S. patent applications. Notwithstanding the foregoing, Applicant understands that the USPTO's computer programs have certain data entry requirements, and hence Applicant is designating the present application as a continuation-in-part of its parent applications as set forth above, but expressly points out that such designations are not to be construed in any way as any type of commentary and/or admission as to whether or not the present application contains any new matter in addition to the matter of its parent application(s). All subject matter of the Related Application and of any and all parent, grandparent, great-grandparent, etc. applications of the Related Application is incorporated herein by reference to the extent such subject matter is not inconsistent herewith. The present patent application relates to nuclear fission reactors and methods. Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor. The foregoing is a summary and thus may contain simplifications, generalizations, inclusions, and/or omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is NOT intended to be in any way limiting. In addition to any illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. Other aspects, features, and advantages of the devices and/or processes and/or other subject matter described herein will become apparent in the teachings set forth herein. Introduction In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, the use of similar or the same symbols in different drawings typically indicates similar or identical items, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken limiting. The present application uses formal outline headings for clarity of presentation. However, it is to be understood that the outline headings are for presentation purposes, and that different types of subject matter may be discussed throughout the application (e.g., device(s)/structure(s) may be described under process(es)/operations heading(s) and/or process(es)/operations may be discussed under structure(s)/process(es) headings; and/or descriptions of single topics may span two or more topic headings). Hence, the use of the formal outline headings is not intended to be in any way limiting. Overview Referring now to FIGS. 1A-1C and FIG. 2 and given by way of non-limiting overview, an illustrative nuclear fission reactor 10 will be described by way of illustration and not of limitation. As will be discussed below in detail, embodiments of the nuclear fission reactor 10 are breed-and-burn fast reactors (also referred to as traveling wave reactors, or TWRs) in which a standing wave of breeding-and-fissioning (also referred to as a breed-burn wave) via movement (also referred to as shuffling) of nuclear fuel assemblies. Still by way of overview, a nuclear fission reactor core 12 is disposed in a reactor vessel 14. A central core region 16 (FIG. 2) of the nuclear fission reactor core 12 includes fissile nuclear fuel assemblies 18 (FIG. 2). The central core region 16 also includes fertile nuclear fuel assemblies 20a (FIG. 2). The central core region 16 also includes movable reactivity control assemblies 22 (FIG. 2). A peripheral core region 24 (FIG. 2) of the nuclear fission reactor core 12 includes fertile nuclear fuel assemblies 20b (FIG. 2). It will be appreciated that the fertile nuclear fuel assemblies 20a and 20b may be made of the same or similar construction (as indicated by use of similar reference numbers). As will be explained further below, the fertile nuclear fuel assemblies 20a reside in a neutron flux environment in the central core region 16 that is different from the neutron flux environment in the peripheral core region 24 (in which the fertile nuclear fuel assemblies 20b reside). As a result, over core life the fertile nuclear fuel assemblies 20a may undergo breeding and may experience burnup at rates that are different from rates undergone and experienced by the fertile nuclear fuel assemblies 20b. Therefore, the similar (but not the same) reference numbers 20a and 20b are used to help keep track of the fertile nuclear fuel assemblies 20a and 20b during discussions herein of various phases of core life. The peripheral core region 24 also includes neutron absorber assemblies 26. An in-vessel handling system 28 is configured to shuffle ones of the fissile nuclear fuel assemblies 18 and ones of the fertile nuclear fuel assemblies 20a and 20b. The nuclear fission reactor 10 also includes a reactor coolant system 30. Continuing by way of non-limiting overview, according to some aspects methods are provided for operating a nuclear fission reactor. Given by way of non-limiting example, in some embodiments fissile nuclear fuel material in a plurality of fissile nuclear fuel assemblies is fissioned in a central core region of a nuclear fission reactor core of a nuclear fission reactor. Fissile material is bred in ones of a plurality of fertile nuclear fuel assemblies in the central core region of the nuclear fission reactor core, and selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies are shuffled in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material. Continuing by way of non-limiting overview, according to some aspects methods are provided for managing excess reactivity in a nuclear fission reactor. Given by way of non-limiting example, in some embodiments criticality with a positive quantity of reactivity is achieved in a central core region of a reactor core of a nuclear fission reactor. The quantity of reactivity is increased until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core, and the increase in reactivity is compensated for. Details will be set forth below by way of non-limiting examples. Illustrative Nuclear Fission Reactors In the discussion set forth below, details regarding extra-core components of the nuclear fission reactor 10 will be set forth first by way of non-limiting examples. Details regarding extra-core components of the nuclear fission reactor 10 will be set forth next by way of non-limiting examples. This ordering of discussion details will facilitate an understanding of establishment of a standing wave of breeding and fissioning in the nuclear fission reactor core 10. Extra-Core Components Still referring to FIGS. 1A-1C and FIG. 2, embodiments of the nuclear fission reactor 10 may be sized for any application as desired. For example, various embodiments of the nuclear fission reactor 10 may be used in low power (around 300 MWe—around 500 MWe) applications, medium power (around 500 MWe—around 1000 MWe) applications, and large power (around 1000 MWe and above) applications as desired. Embodiments of the nuclear fission reactor 10 are based on elements of liquid metal-cooled, fast reactor technology. For example, in various embodiments the reactor coolant system 30 includes a pool of liquid sodium disposed in the reactor vessel 14. In such cases, the nuclear fission reactor core 12 is submerged in the pool of sodium coolant in the reactor vessel 14. The reactor vessel 14 is surrounded by a containment vessel 32 that helps prevent loss of sodium coolant in the unlikely case of a leak from the reactor vessel 14. In various embodiments the reactor coolant system 30 also includes reactor coolant pumps 34. The reactor coolant pumps 34 may be any suitable pump as desired, such as for example electromechanical pumps or electromagnetic pumps. In various embodiments the reactor coolant system 30 also includes heat exchangers 36. The heat exchangers 36 are disposed in the pool of primary liquid sodium. The heat exchangers 36 have non-radioactive intermediate sodium coolant on the other side of the heat exchangers 36. To that end, the heat exchangers 36 may be considered intermediate heat exchangers. Steam generators (not shown for clarity in FIGS. 1A-1C and 2) are in thermal communication with the heat exchangers 36. It will be appreciated that any number of reactor coolant pumps 34, heat exchangers 36, and steam generators may be used as desired. The reactor coolant pumps 34 circulate primary sodium coolant through the nuclear fission reactor core 12. The pumped primary sodium coolant exits the nuclear fission reactor core 12 at a top of the nuclear fission reactor core 12 and passes through one side of the heat exchangers 36. Heated intermediate sodium coolant is circulated via intermediate sodium loops 42 to the steam generators (not shown) that, in turn, generate steam to drive turbines (not shown) and electrical generators (not shown). During periods of reactor shut down, in some embodiments plant electrical loads are powered by the electrical grid and decay heat removal is provided by pony motors (not shown for clarity) on the reactor coolant pumps 34 that deliver reduced reactor coolant flow through heat transport systems. Referring additionally to FIGS. 5A and 5B, in various embodiments the nuclear fission reactor 10 includes a decay heat removal system 38. In the event that electrical power is not available from the electric grid, decay heat is removed using the decay heat removal system 38. In various embodiments, the decay heat removal system 38 may include either one or both of two dedicated safety class decay heat removal systems 38a (FIG. 5A) and 38b (FIG. 5B) which operate entirely by natural circulation with no need for electrical power. In the safety class decay heat removal system 38a (FIG. 5A), heat from the nuclear fission reactor core 12 first is transferred by naturally circulated sodium to the reactor vessel 14, then is radiated across an argon-filled gap 40 between the reactor vessel 14 and the containment vessel 32, and finally is removed by naturally circulating ambient air that flows along the wall of the containment vessel 32. In the safety class decay heat removal system 38b (FIG. 5B), the heat exchangers 36 and the intermediate sodium loops 42 (FIGS. 1A-1C) transfer heat by natural circulation of sodium to steam generators 44 where the heat is dissipated through shell walls of the steam generator 44 using ambient temperature air drawn in through protected air intakes 46. Referring back to FIGS. 1A-1C and 2, the in-vessel handling system 28 is configured to shuffle ones of the fissile nuclear fuel assemblies 18 and ones of the fertile nuclear fuel assemblies 20a and 20b. In some stages of core life (as will be discussed below), it may be desired to shuffle ones of the fissile nuclear fuel assemblies 18 and ones of the fertile nuclear fuel assemblies 20a and 20b between the central core region 16 and the peripheral core region 24. Thus, the in-vessel handling system 28 may also be configured to shuffle ones of the fissile nuclear fuel assemblies 18 and ones of the fertile nuclear fuel assemblies 20a and 20b between the central core region 16 and the peripheral core region 24. It will be appreciated that the in-vessel handling system 28 permits movement of the selected fissile nuclear fuel assemblies 18 and fertile nuclear fuel assemblies 20a and 20b without removing the moved fissile nuclear fuel assemblies 18 and fertile nuclear fuel assemblies 20a and 20b from the nuclear fission reactor 10. In various embodiments, the in-vessel handling system 28 includes a rotating plug 48 and a rotating plug 50 that are both vertically spaced apart from the top of the nuclear fission reactor core 12. The rotating plug 50 is smaller than the rotating plug 48 and is disposed on top of the rotating plug 48. An offset arm machine 52 extends through the rotating plug 48 to the top of the nuclear fission reactor core 12. The offset arm machine 52 is rotatable through the rotating plug 48. A straight pull machine 54 extends through the rotating plug 50 to the top of the nuclear fission reactor core 12. Lower ends of the offset arm machine 52 and the straight pull machine 54 include suitable gripping devices, such as grapples or the like, that enable gripping of selected fissile nuclear fuel assemblies 18 and fertile nuclear fuel assemblies 20a and 20b (and in some applications, as will be discussed below, neutron absorber assemblies disposed in the peripheral core region 24) by the offset arm machine 52 and the straight pull machine 54 during movement operations. Rotation of the rotating plugs 48 and 50 and the offset arm machine 52 allows the offset arm machine 52 and the straight pull machine 54 to be localized to any desired position for pulling a selected assembly out of the nuclear fission reactor core 12 and for re-inserting the selected assembly into the nuclear fission reactor core 12 at any desired empty location. In some embodiments the in-vessel handling system 28 may be further configured to move ones of the neutron absorber assemblies among selected locations in the peripheral core region 24. In such cases, the locations in the peripheral core region 24 may be selected from predetermined radial locations in the peripheral core region 24 based upon a predetermined burnup level of nuclear fuel assemblies 18, 20a, and/or 20b (depending upon stage of core life and burnup levels) that are located in the peripheral core region 24. In some other embodiments, the in-vessel handling system 28 may be further configured to rotate ones of the neutron absorber assemblies. In some other embodiments, the in-vessel handling system 28 may be further configured to shuffle ones of the fissile nuclear fuel assemblies 18 and ones of the fertile nuclear fuel assemblies 20a and/or 20b (depending upon stage of core life and burnup levels) between the central core region 16 and a portion of the reactor vessel 14 that is located as desired exterior the nuclear fission reactor core 12. In-Core Components Given by way of nonlimiting overview, in embodiments of the nuclear fission reactor core 12 a sufficient number of fissile nuclear fuel assemblies achieve initial criticality and sufficient breeding to approach a steady state reactor core breed-and-burn (breeding-and-fissioning) condition. The fissile assemblies are primarily located in the central core region 16, which generates most of the core power. Fertile nuclear fuel assemblies are placed in the central core region 16 and the peripheral core region 24 and their number is selected such that reactor operation is possible for up to 40 years or more without the need to bring new fuel into the reactor. The initial core loading is configured to achieve criticality with a small amount of excess reactivity and ascension to full power output shortly after initial reactor startup. Excess reactivity increases because of breeding until a predetermined burnup is achieved in a selected number of fuel assemblies. The reactivity increase is compensated by movable reactivity control assemblies, which are gradually inserted into the core to maintain core criticality. Still given by way of non-limiting overview, a wave of breeding and fissioning (a “breed-burn wave” is originated in the central core region 16 but does not move through fixed core material. Instead, a “standing” wave of breeding and fissioning (“burning”) is established by periodically moving core material in and out of the breed-burn region. This movement of fuel assemblies is referred to as “fuel shuffling” and will be described in more detail later. Details regarding components within the nuclear fission reactor core 12 will now be discussed by way of non-limiting examples. When relevant, differences over core life in composition and/or burnup levels of fuel assemblies and/or locations of fuel assemblies within the nuclear fission reactor core 12 will be noted. Regardless of stage of core life, the central core region 16 includes the movable reactivity control assemblies 22. The movable reactivity control assemblies 22 suitably may be provided as control rods and may be moved axially in and/or out of the central core region 16 by associated control rod drive mechanisms. It will be appreciated that axial position of the movable reactivity control assemblies 22 may be adjusted by the control rod drive mechanisms to insert neutron absorbing material into the central core region 16 and/or to remove neutron absorbing material from the central core region 16 as desired (such as to compensate for increases in reactivity, to compensate for decreases in reactivity, to shut down the reactor for planned shutdowns, and/or to start up the reactor after the reactor has been shut down). It will also be appreciated that in some embodiments the movable reactivity control assemblies 22 may perform safety functions, shut as rapidly inserting neutron absorbing material to rapidly shut down the reactor (that is, scramming the reactor). In some embodiments, neutron absorbing material disposed in the movable reactivity control assemblies 22 may include hafnium hydride. Also regardless of stage of core life, the peripheral core region 24 includes the neutron absorber assemblies 26. Unlike the movable reactivity control assemblies 22 (which may be moved during reactor operation as desired, such as to compensate for increases in reactivity), the neutron absorber assemblies 26 remain in-place and do not move during reactor operation. The neutron absorber assemblies 26 help maintain a low core power level in the peripheral core region 24. This low power level helps to simplify coolant flow requirements in the peripheral core region 24. This low power level also helps to mitigate further increases in burnup in fuel assemblies that previously have been used for power production in the central core region 16 and subsequently have been moved from the central core region 16 to the peripheral core region 24. In some embodiments, neutron absorbing material disposed in the neutron absorber assemblies 26 may include hafnium hydride. However, as discussed above, in some embodiments, if desired the neutron absorber assemblies 26 may be moved by the in-vessel handling system 28 among selected locations in the peripheral core region 24. As mentioned above, the locations in the peripheral core region 24 may be selected from predetermined radial locations in the peripheral core region 24 based upon a predetermined burnup level of nuclear fuel assemblies 18, 20a, and/or 20b (depending upon stage of core life and burnup levels) that are located in the peripheral core region 24. As also discussed above, in some other embodiments the neutron absorber assemblies 26 may be rotated by the in-vessel handling system 28. Now that the movable reactivity control assemblies 22 and the neutron absorber assemblies 26 have been discussed, the nuclear fuel assemblies 18, 20a, and 20b will be discussed. As mentioned above, this discussion includes references to various stages of core life. Regardless of stage of core life, fertile material in the fertile nuclear fuel assemblies 20 (that is, the fertile nuclear fuel assemblies 20a and the fertile nuclear fuel assemblies 20b) includes U238. In various embodiments, the U238 may include natural uranium and/or depleted uranium. Thus, in various embodiments at least one of the fertile nuclear fuel assemblies 20a may include U238 that includes natural uranium. In some other embodiments, at least one of the fertile nuclear fuel assemblies 20a may include U238 that includes depleted uranium. In some embodiments, at least one of the fertile nuclear fuel assemblies 20b may include U238 that includes natural uranium. In some embodiments, at least one of the fertile nuclear fuel assemblies 20b may include U238 that includes depleted uranium. That is, at any point in core life any one or more of the nuclear fuel assemblies 20a may include U238 that includes natural uranium, any one or more of the nuclear fuel assemblies 20a may include U238 that includes depleted uranium, any one or more of the nuclear fuel assemblies 20b may include U238 that includes natural uranium, and/or any one or more of the nuclear fuel assemblies 20b may include U238 that includes depleted uranium. Thus, regardless of stage of core life, the U238 in the fertile nuclear fuel assemblies 20a and/or 20b need not be limited to any one of natural uranium or depleted uranium. Therefore, at any stage in core life, one or more of the nuclear fuel assemblies 20a may include natural uranium, one or more of the nuclear fuel assemblies 20a may include depleted uranium, one or more of the nuclear fuel assemblies 20b may include natural uranium, and/or one or more of the nuclear fuel assemblies 20b may include depleted uranium. At beginning of life (BOL), in various embodiments the central core region 16 includes the fissile nuclear fuel assemblies 18, the fertile nuclear fuel assemblies 20a, and the movable reactivity control assemblies 22, and the peripheral core region includes the fertile nuclear fuel assemblies 20b and the neutron absorber assemblies 26. The fertile nuclear fuel assemblies 20a and 20b, the movable reactivity control assemblies 22, and the neutron absorber assemblies 26have been discussed above for all stages of core life, including BOL. At BOL, the central core region 16 includes the fissile nuclear fuel assemblies 18 and the fertile nuclear fuel assemblies 20, and during core life (and possibly at end-of-life) the central core region 16 includes the fissile nuclear fuel assemblies 18 and the fertile nuclear fuel assemblies 20a and/or 20b. The nuclear fuel assemblies 18 and 20 may be arranged as desired within the central core region 16. In some embodiments, the nuclear fuel assemblies 18 and 20 may be arranged symmetrically within the central core region 16. At BOL, the fissile nuclear fuel assemblies 18 include enriched fissile nuclear assemblies 18a. In various embodiments, enriched fissile material in the enriched fissile nuclear assemblies 18a includes U235. Uranium in the enriched fissile nuclear fuel assemblies 18a is typically enriched less than twenty percent (20%) in the U235 isotope. It will be appreciated that in some embodiments (such as the first of a fleet of the nuclear fission reactors 10), at BOL all of the fissile material in the fissile nuclear fuel assemblies 18a includes U235. However, in other embodiments (such as in later nth-of-a-kind members of a fleet of the nuclear fission reactors 10), as will be discussed below at BOL at least some of the fissile material in the fissile nuclear fuel assemblies 18a may include Pu239 (that has been bred in previous members of the fleet of nuclear fission reactors 10). It will be further appreciated that only a small mass of fissile nuclear fuel material (relative to the total mass of nuclear fuel material, including fertile nuclear fuel material, included in the nuclear fission reactor core 10 and, as will be appreciated, as opposed to a conventional fast breeder reactor) is entailed in initiating a breeding-and-fissioning (breed-burn) wave in the nuclear fission reactor core 10. Illustrative initiation and propagation of a breeding-and-fissioning (breed-burn) wave is described by way of example and not of limitation in U.S. patent application Ser. No. 11/605,943 , entitled AUTOMATED NUCLEAR POWER REACTOR FOR LONG-TERM OPERATION, naming RODERICK A. HYDE, MURIEL Y. ISHIKAWA, NATHAN P. MYHRVOLD, AND LOWELL L. WOOD, JR. as inventors, filed 28 Nov. 2006 , the contents of which are hereby incorporated by reference. It will further be noted that it is within the capacity of a person of skill in the art of nuclear fission reactor design and operation to determine, without undue experimentation, the amount of fissile nuclear fuel material that is entailed in initiating a breeding-and-fissioning (breed-burn) wave in a nuclear fission reactor core 10 of any size as desired. It will also be appreciated that a breed-burn wave does not move through fixed core material. Instead, a “standing” wave of breeding and burning (fissioning) is established by periodically moving core material in and out of the breed-burn region. This movement of fuel assemblies is referred to as “fuel shuffling” and will be described in more detail later. It will be appreciated that after BOL the nuclear fission reactor 10 has been started up and the enriched fissile nuclear fuel assemblies 18a have begun fissioning. Some of the neutrons may be absorbed by nuclei of fertile material, such as U238, in the fertile nuclear fuel assemblies 20a in the central core region 16. As a result of such absorption, in some instances the U238 will be converted via capture to U239, then via β decay to Np239, then via further β decay to Pu239. Thus, in such cases the fertile material (that is, U238) in the fertile nuclear fuel assemblies 20a will have been bred to fissile material (that is, Pu239) and, as a result, such fertile nuclear fuel assemblies 20a will have been converted into bred nuclear fuel assemblies 18b. Therefore, it will be appreciated that after BOL the fissile nuclear fuel assemblies 18 in the central core region 16 include the enriched fissile nuclear fuel assemblies 18a and the bred fissile nuclear fuel assemblies 18b. As discussed above, fissile material in the enriched fissile nuclear fuel assemblies 18a may include U235 and fissile material in the bred fissile nuclear fuel assemblies 18b may include PU239. Some of the other neutrons may be absorbed by other nuclei of fertile material, such as U238, in the fertile nuclear fuel assemblies 20a in the central core region 16. As a result of such absorption, in some other instances it will be appreciated that the U238 in some of the fertile nuclear fuel assemblies 20a may undergo fast fission. It will be further appreciated that, after BOL, some neutrons may leak from the central core region 16 to the peripheral core region 24. In such cases, some of the leaked neutrons may be absorbed by fertile material (such as U238) in the fertile nuclear fuel assemblies 20b in the peripheral core region 24. As a result of such absorption and as discussed above, in some instances the U238 will be converted via capture to U239, then via β decay to Np239, then via further β decay to Pu239. Thus, in such cases the fertile material (that is, U238) in the fertile nuclear fuel assemblies 20b will have been bred to fissile material (that is, Pu239) and, as a result, such fertile nuclear fuel assemblies 20b will have been converted into bred nuclear fuel assemblies 18b. Thus, in such cases, after BOL the peripheral core region 24 may include ones of the bred fissile nuclear fuel assemblies 18b. Some of the other leaked neutrons may be absorbed by other nuclei of fertile material, such as U238, in the fertile nuclear fuel assemblies 20b in the peripheral core region 24. As a result of such absorption, in some other instances it will be appreciated that the U238 in some of the fertile nuclear fuel assemblies 20b may undergo fast fission. As discussed above, the neutron absorber assemblies 26 help maintain a low power level in the peripheral core region even though fast fission of U238 in the fertile nuclear fuel assemblies 20b in the peripheral core region 24 may occur. The enriched fissile nuclear fuel assemblies 18a will undergo burnup after BOL. After some time after BOL, the enriched fissile nuclear fuel assemblies 18a will accumulate sufficient burnup such that it will be desired to shuffle (or move) such enriched fissile nuclear fuel assemblies 18a from the central core region 16 to the peripheral core region 24 (with the in-vessel handling system 28). It will be appreciated that a person of skill in the art of nuclear fission reactor design and operation will be able to determine, without undue experimentation, a burnup level at which one of the enriched fissile nuclear fuel assemblies 18a is to be shuffled from the central core region 16 to the peripheral core region 24. Thus, in such cases, the peripheral core region 24 may further include selected ones of the enriched fissile nuclear fuel assemblies 18a having at least a predetermined burnup level. Likewise, the bred fissile nuclear fuel assemblies 18b will also undergo burnup after BOL. After some time after BOL, the bred fissile nuclear fuel assemblies 18b will accumulate sufficient burnup such that it will be desired to shuffle (or move) such bred fissile nuclear fuel assemblies 18b from the central core region 16 to the peripheral core region 24 (with the in-vessel handling system 28). It will be appreciated that a person of skill in the art of nuclear fission reactor design and operation will be able to determine, without undue experimentation, a burnup level at which one of the enriched fissile nuclear fuel assemblies 18b is to be shuffled from the central core region 16 to the peripheral core region 24. Thus, in such cases, the peripheral core region 24 may further include selected ones of the bred fissile nuclear fuel assemblies 18b having at least a predetermined burnup level. It will further be appreciated that, as discussed above, some of the fertile nuclear fuel assemblies 20b in the peripheral core region 24 will be converted to the bred fissile nuclear fuel assemblies 18b. As also discussed above, the fertile nuclear fuel assemblies 20b may have been subject to neutron flux levels in the peripheral core region 24 below neutron flux levels in the central core region 16 to which the fertile nuclear fuel assemblies 20a have been subjected. As a result, the peripheral core region 24 may include ones of the bred fissile nuclear fuel assemblies 18b (that is, converted from the fertile nuclear fuel assemblies 20b in the peripheral core region 24) having less than a predetermined burnup level. During various stages of core life, ones of the neutron absorber assemblies 26 may be moved by the in-vessel handling system 28 among any of several locations in the peripheral core region 24. The locations in the peripheral core region 24 may include predetermined radial locations in the peripheral core region 24 that are selectable based upon a predetermined burnup level of nuclear fuel assemblies 18 and 20 that are located in the peripheral core region 24. Toward end-of-life (EOL), the enriched fissile nuclear fuel assemblies 18a may have undergone sufficient burnup such that the enriched fissile nuclear fuel assemblies 18a have been shuffled (moved) from the central core region 16 to the peripheral core region 24. Thus, toward EOL the fissile nuclear fuel assemblies 18 that are located in the central core region 16 are the bred fissile nuclear fuel assemblies 18b. Therefore, toward EOL, the fissile nuclear fuel assemblies 18 (in the central core region 16) include the bred fissile nuclear fuel assemblies 18b, and the peripheral core region 24 includes enriched fissile nuclear fuel assemblies 18a having at least a predetermined burnup level. It will be appreciated that, toward EOL, the peripheral core region may also include bred fissile fuel assemblies 18b. Some of the bred fissile nuclear fuel assemblies 18b in the peripheral core region 24 may include selected ones of the bred fissile nuclear fuel assemblies 18b that have been shuffled from the central core region 16 to the peripheral core region 24 and that have at least a predetermined burnup level. It will further be appreciated that some others of the bred fissile nuclear fuel assemblies 18b in the peripheral core region 24 may include (i) ones of the bred fissile nuclear fuel assemblies 18b that have been shuffled from the central core region 16 to the peripheral core region 24 that have less than a predetermined burnup level and/or (ii) ones of the bred fissile nuclear fuel assemblies 18b that have been converted from ones of the fertile nuclear fuel assemblies 20b (that have resided in the peripheral core region 24) that have less than a predetermined burnup level. Embodiments of the nuclear fission reactor 10 lend themselves to fuel recycling. Some embodiments of the nuclear fission reactor 10 may discharge their fuel at an average burnup of approximately 15% of initial heavy metal atoms, with axial peaking making the peak burnup in the range of 28-32%. Meanwhile, fissile material bred in various embodiments of the nuclear fission reactor 10 of nominal ‘smear’ composition may remain critical to over 40% average burnup (even without any fission product removal) via melt refining. Including the effect of periodic melt refining can allow burn-ups exceeding 50% to be achieved. Therefore, fuel discharged from a first generation nuclear fission reactor 10 still has most of its potential life remaining from a neutronic standpoint (even before any “life extension” associated with thermal removal of fission products during recladding is considered) and would be available for re-use without any need for chemical reprocessing. To that end and as mentioned above, in some embodiments (such as in later nth-of-a-kind members of a fleet of the nuclear fission reactors 10), at BOL at least some of the fissile material in the fissile nuclear fuel assemblies 18a may include Pu239 (that has been bred in previous members of the fleet of nuclear fission reactors 10). In some such cases, one or more of the fissile nuclear fuel assemblies 18 may include fissile material that has been discharged from a nuclear fission reactor. Moreover, in some of these cases the fissile nuclear fuel assemblies 18 that include fissile material that has been discharged from a nuclear fission reactor may include re-clad fissile fuel assemblies. In such embodiments, the fissile nuclear fuel assemblies 18 may be recycled via fuel recladding—a process in which the old clad is removed and the used fuel is refabricated into new fuel. The fissile fuel material is recycled through thermal and physical (but not chemical) processes. The used fuel assemblies are disassembled into individual fuel rods which then have their cladding mechanically cut away. The used fuel then undergoes a high temperature (1300-1400° C.) melt refining process in an inert atmosphere which separates many of the fission products from the fuel in two main ways: (i) the volatile and gaseous fission products (e.g., Br, Kr, Rb, Cd, I, Xe, Cs) simply escape; while (ii) the more than 95% of the chemically-reactive fission products (e.g., Sr, Y, Te, Ba, and rare earths) become oxidized in a reaction with the zirconia crucible and are readily separated. The melt-refined fuel can then be cast or extruded into new fuel slugs, placed into new cladding with a sodium bond, and integrated into new fuel assemblies. Referring additionally to FIG. 3, an illustrative nuclear fuel assembly (regardless of whether it is a fissile nuclear fuel assembly 18 or a fertile nuclear fuel assembly 20) includes fuel pins (or fuel rods or fuel elements) 56. In various embodiments, the fuel pins 56 include metal fuel (again, regardless of whether the fuel is fissile fuel or fertile fuel). It will be appreciated that metal fuel offers high heavy metal loadings and excellent neutron economy, which is desirable for the breed-and-burn process in the nuclear fission reactor core 12. In various embodiments the metal fuel may be alloyed with about 3% to about 8% zirconium to dimensionally stabilize the alloy during irradiation and to inhibit low-temperature eutectic and corrosion damage of the cladding. A sodium thermal bond fills the gap that exists between the alloy fuel and the inner wall of the clad tube to allow for fuel swelling and to provide efficient heat transfer which keeps the fuel temperatures low. Individual fuel pins 56 may have a thin wire 58 from about 0.8 mm diameter to about 1.6 mm diameter helically wrapped around the circumference of the clad tubing to provide coolant space and mechanical separation of individual fuel pins 56 within the housing of the fuel assembly 18 and 20 (that also serves as the coolant duct). In various embodiments the cladding, wire wrap, and housing may be fabricated from ferritic-martensitic steel because of its irradiation performance as indicated by a body of empirical data. Large power differences between the fissile nuclear fuel assemblies 18 in the central core region 16 and the fertile nuclear fuel assemblies 20a and/or 20b in the peripheral core region 24 entail significant differences in assembly flow distribution to match flow to power and thus outlet temperature. In various embodiments this flow distribution is accomplished through orifices, such as a combination of fixed and variable orifices, which make it possible to optimize primary coolant flow proportionally to predicted assembly power. Referring now to FIG. 4A, in various embodiments orifices 60, such as fixed orifices, are installed in fuel assembly flow receptacles 62 below the nuclear fission reactor core 12. The fuel assembly flow receptacles 62 mate with seats 64 in a core support grid plate 66 and contain sockets 68 where the nuclear fuel assemblies 18 and 20 are inserted. The fuel assembly flow receptacles 62 have orifices 60 that may be used to match flow to power generated in the nuclear fuel assemblies. For example, the fuel assembly flow receptacles 62 under the peripheral core region 24 have very high-pressure-drop orifices 60 to minimize the flow into very low-power fertile nuclear fuel assemblies 20. On the other hand, the fuel assembly flow receptacles 62 below the nuclear fuel assemblies 18 and 20 in the central core region 16 may be divided into several groups having orifices 60 ranging from very low resistance to higher resistance to match the radial power profile in the central core region 16. In addition to the fixed orifices 60, in some embodiments each nuclear fission fuel assembly 18 and 20 may have an ability to adjust assembly flow by rotation during fuel shuffling operations to enable minor flow adjustments at the assembly level, if desired. Thus, in some embodiments, the fuel assembly flow receptacles 62 may define a group of reactor coolant flow orifices 60 in the central core region 16 and another group of reactor coolant flow orifices 60 in the peripheral core region 24. The group of reactor coolant flow orifices 60 in the central core region 16 may includes reactor coolant flow orifice groups. In such cases, flow rate through a selected one of the reactor coolant flow orifice groups may be based upon a power profile at a radial location of the selected one of the reactor coolant flow orifice groups. Moreover, flow rate through the reactor coolant flow orifices 60 in the peripheral core region 24 may include a predetermined flow rate based upon power level in the peripheral core region 24. In various embodiments, the orifices 60 include fixed orifices. In other embodiments, variable orifices may be provided (via rotation of the nuclear fuel assemblies 18 and 20). In some other embodiments, the orifices 60 may include fixed orifices and variable orificing may also be provided (via rotation of the nuclear fuel assemblies 18 and 20). In some other embodiments and referring additionally to FIG. 4B, a core support grid plate 66a may be “stepped”. That is, the stepped core support grid plate 66a may be used to offset the nuclear fuel assemblies 18 and 20 axially. As such, the stepped core support grid plate 66a allows changing position of the nuclear fuel assemblies 18 and 20 in the axial direction as a function of their position in the radial direction. Utilization of fuel in the nuclear fission reactor core 12 may be further increased by offsetting the assemblies axially (in addition to shuffling the nuclear fuel assemblies 18 and 20 radially). It will be appreciated that relative neutron flux distribution is higher in the central axial zone of the nuclear fission reactor core 12 than in the axial extents of the nuclear fission reactor core 12, as shown by curve 67. Such axially offsetting can allow for fuel bred near the axial extents of the fertile nuclear fuel assemblies 20 to be moved closer to (or, if needed, further from) the central axial zone of the nuclear fission reactor core 12. Such offsetting can thus allow for a higher degree of control of bum-up in the axial dimension, which can further help yield higher fuel utilization. In some embodiments the stepped core support grid plate 66a may include a single axially-sectioned assembly. In some embodiments the level of offset could be fixed and could include a pre-determined fuel management strategy. In some other embodiments the level of offset may be altered through the use of spacers, such as risers or shims or the like, that may be installed at the bottom of the nuclear fuel assemblies 18 and 20 or directly onto the stepped core support grid plate 66a. Aspects of operation of embodiments of the nuclear fission reactor core 12 will be explained. It will be appreciated that various design features of embodiments of the nuclear fission reactor core 10 can help increase the maximum burnup and fluence the fuel can sustain before the accumulation of fission products makes the fuel subcritical. For example, the fissile nuclear fuel assemblies 18 in the central core region 16 are surrounded by subcritical feed fuel (that is, the fertile nuclear fuel assemblies 20 in the central core region 16 and in the peripheral core region 24), which absorbs leakage neutrons and uses them to breed new fuel. It will be appreciated by those of skill in the art of nuclear reactor design and operation that past a thickness of feed fuel surrounding the central core region 16 of approximately 70 cm (or, depending upon size of the fertile nuclear fuel assemblies 20, about 5 assembly rows) the fraction of neutrons leaking from the nuclear fission reactor core 12 is reduced toward zero. Such neutron conserving features accomplish two things. First, they minimize the burnup and fluence entailed in achieving breeding-and-fissioning wave propagation, which in turn eases material degradation issues and enables embodiments of the nuclear fission reactor 10 to be made with existing materials. Second, they increase the maximum burnup and fluence the fuel can sustain before the accumulation of fission products makes the fuel subcritical. This second point is illustrated in FIG. 6A. Referring additionally to FIG. 6A, a graph 70 graphs reactivity versus burnup for illustrative embodiments of the nuclear fission reactor core 12 along a curve 72. The graph 70 compares the reactivity evolution of feed fuel in illustrative embodiments of the nuclear fission reactor core 12 (illustrated along the curve 72) with the reactivity evolution of enriched fuel from a typical sodium fast reactor which is illustrated along a curve 74. The enriched fuel from a typical sodium fast reactor is modeled as having SuperPhenix fuel, coolant and structure volume fractions with 75% smear density, and an initial enrichment of 16%. As is known, typical sodium fast reactor fuel must start at a high enrichment to achieve criticality, and the excess reactivity of fresh fuel is lost to control elements, absorption in the breeding blanket, and leakage from the core. As shown by the curve 74, the typical sodium fast reactor fuel quickly loses reactivity as U235 is depleted, and it becomes subcritical at approximately 310 MWd/kgHM burnup. At the point where the typical sodium fast reactor fuel becomes subcritical, about half of the total fissions are due to U235, and the utilization fraction of U238 is less than 20%. Meanwhile, as shown by the curve 72, feed fuel in embodiments of the nuclear fission reactor core 12 begins as subcritical fertile fuel in the fertile nuclear fuel assemblies 20 and gains reactivity as Pu239 is bred in. Once the fuel becomes critical, excess reactivity is offset by breeding additional subcritical feed fuel (it will be noted that during the first 50 MWd/kgHM of burn-up, the driver fuel makes the reactor critical). A total fuel burnup of up to 400 MWd/kgHM or higher can be achieved before the fuel becomes subcritical, and since the fuel begins as nearly all U238, the U238 utilization fraction can be greater than 40%. Referring additionally to FIG. 6B, a graph 76 of reactivity versus burnup shows effects of periodic thermal removal of fission products along a curve 78. The graph 76 also includes the graph 72 for feed fuel without thermal removal of fission products. Embodiments of the nuclear fission reactor core 12 are presently designed to discharge their fuel at an average burnup of approximately 15% of initial heavy metal atoms, with axial peaking making the peak burnup in the range of 28-32%. Meanwhile, as shown by the curve 72, feed fuel bred in an illustrative nuclear fission reactor core 12 of nominal ‘smear’ composition remains critical to over 40% average burnup, even without any fission product removal via melt refining. Including the effect of periodic melt refining, as shown by the curve 78, allows burn-ups exceeding 50% to be achieved. Therefore, fuel discharged from a first generation nuclear fission reactor 10 still has most of its potential life remaining from a neutronic standpoint (even before any “life extension” associated with thermal removal of fission products during recladding is considered) and would be available for reuse without any need for chemical reprocessing. Referring now to FIG. 7, a graph 80 illustrates plutonium isotope evolution versus utilization of U238. At low utilization, the plutonium produced is substantially all Pu239, since operation begins with U238 and no plutonium. At higher utilizations, the plutonium quality becomes increasingly degraded as higher isotopes of plutonium are created. At the point which the feed fuel's k-infinity falls below unity (as shown by the curve 72 in FIGS. 6A and 6B), the fissile plutonium fraction is under 70%, similar to reactor-grade plutonium from LWR spent fuel. Additionally, the plutonium in spent fuel from embodiments of the nuclear fission reactor 10 is contaminated to a much higher degree with fission products, thereby making it more difficult to handle and reprocess and less attractive for diversion to weapons purposes. Illustrative Methods Following are a series of flowcharts depicting implementations. For ease of understanding, the flowcharts are organized such that the initial flowcharts present implementations via an example implementation and thereafter the following flowcharts present alternate implementations and/or expansions of the initial flowchart(s) as either sub-component operations or additional component operations building on one or more earlier-presented flowcharts. Those having skill in the art will appreciate that the style of presentation utilized herein (e.g., beginning with a presentation of a flowchart(s) presenting an example implementation and thereafter providing additions to and/or further details in subsequent flowcharts) generally allows for a rapid and easy understanding of the various process implementations. In addition, those skilled in the art will further appreciate that the style of presentation used herein also lends itself well to modular and/or object-oriented program design paradigms. Given by way of overview and referring now to FIG. 8A, a method 100 is provided for operating a nuclear fission reactor. The method 100 starts at a block 102. At a block 104 fissile nuclear fuel material is fissioned in a plurality of fissile nuclear fuel assemblies in a central core region of a nuclear fission reactor core of a nuclear fission reactor. At a block 106 fissile material is bred in ones of a plurality of fertile nuclear fuel assemblies in the central core region of the nuclear fission reactor core. At a block 108 selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies are shuffled in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material. The method 100 stops at a block 110. Details will be set forth below by way of non-limiting examples. Referring to FIG. 8B, in some embodiments fissioning fissile nuclear fuel material in a plurality of fissile nuclear fuel assemblies in a central core region of a nuclear fission reactor core of a nuclear fission reactor at the block 104 may include generating in the central core region at least a predetermined amount of power in the nuclear fission reactor core at a block 112. Referring to FIG. 8C, in some embodiments neutrons may be absorbed in a peripheral core region at a block 114. Referring to FIG. 8D, in some embodiments absorbing neutrons in a peripheral core region at the block 114 may include absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at a block 116. Referring to FIG. 8E, in some embodiments absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at the block 116 may include breeding fissile material in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at a block 118. Referring to FIG. 8F, in some embodiments absorbing neutrons in a peripheral core region at the block 114 may include absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at a block 120. Referring to FIG. 8G, in some embodiments absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at the block 120 may include absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region such that power produced in the peripheral core region is maintained below a predetermined power level at a block 122. Referring to FIG. 8H, in some embodiments absorbing neutrons in a peripheral core region at the block 114 may include absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region and absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at a block 124. Referring to FIG. 8I, in some embodiments at a block 126 the nuclear fission reactor may be shut down before shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies. Referring to FIG. 8J, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material at the block 108 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies between the central core region and the peripheral core region in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material at a block 128. Referring to FIG. 8K, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at the block 108 may include replacing selected ones of the plurality of fissile nuclear fuel assemblies of the central core region with selected ones of the plurality of fertile nuclear fuel assemblies of the central core region and with selected others of the plurality of fertile nuclear fuel assemblies of the peripheral core region at a block 130. Referring to FIG. 8L, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at the block 108 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies having a predetermined burnup level and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 132. Referring to FIG. 8M, in some embodiments reactivity in the central core region may be controlled at a block 134. Referring to FIG. 8N, in some embodiments controlling reactivity in the central core region at the block 134 may include controlling reactivity in the central core region with a plurality of movable reactivity control assemblies at a block 136. Referring to FIG. 8O, in some embodiments controlling reactivity in the central core region at the block 134 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 138. Referring to FIG. 8P, in some embodiments controlling reactivity in the central core region at the block 134 may include controlling reactivity in the central core region with a plurality of movable reactivity control assemblies and shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 140. Referring to FIG. 8Q, in some embodiments reactor coolant may be flowed through a first plurality of reactor coolant flow orifices in the central core region at a block 142 and reactor coolant may be flowed through a second plurality of reactor coolant flow orifices in the peripheral core region at a block 144. Referring to FIG. 8R, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 142 may include flowing reactor coolant through a plurality of reactor coolant flow orifice groups in the central core region at a block 146. In some embodiments, flow rate through a selected one of the plurality of reactor coolant flow orifice groups may be based upon a power profile at a radial location of the selected one of the plurality of reactor coolant flow orifice groups. In some embodiments, flow rate through the second plurality of reactor coolant flow orifices may include a predetermined flow rate based upon power level in the peripheral core region. Referring to FIG. 8S, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 142 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 144 may include maintaining substantially steady flow of reactor coolant through ones of the first and second pluralities of reactor coolant flow orifices at a block 148. Referring to FIG. 8T, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 142 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 144 may include varying flow of reactor coolant through others of the first and second pluralities of reactor coolant flow orifices at a block 150. Referring to FIG. 8U, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 142 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 144 may include maintaining substantially steady flow of reactor coolant through ones of the first and second pluralities of reactor coolant flow orifices and varying flow of reactor coolant through others of the first and second pluralities of reactor coolant flow orifices at a block 152. Referring to FIG. 8V, in some embodiments flow of reactor coolant may be varied through at least one of the shuffled nuclear fuel assemblies at a block 154. Referring to FIG. 8W, in some embodiments varying flow of reactor coolant through at least one of the shuffled nuclear fuel assemblies at the block 154 may include rotating at least one of the shuffled nuclear fuel assemblies at a block 156. Referring to FIG. 8X, in some embodiments ones of the plurality of neutron absorber assemblies may be moved among a plurality of locations in the peripheral core region at a block 158. In some embodiments, the plurality of locations in the peripheral core region may include a plurality of predetermined radial locations in the peripheral core region that are selectable based upon a predetermined burnup level of ones of the fissile nuclear fuel assemblies that have been shuffled into the peripheral core region. Referring to FIG. 8Y, in some embodiments at a block 160 ones of the plurality of fissile nuclear fuel assemblies and ones and others of the plurality of fertile nuclear fuel assemblies may be selected for shuffling in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material. In some embodiments selecting ones of the plurality of fissile nuclear fuel assemblies and ones and others of the plurality of fertile nuclear fuel assemblies for shuffling in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material may be based upon at least one operational datum chosen from neutron flux data, fuel assembly outlet temperature, and fuel assembly flow rate. Given by way of overview and referring now to FIG. 9A, a method 200 is provided for operating a nuclear fission reactor. The method 200 starts at a block 202. At a block 204 fissile nuclear fuel material is fissioned in a plurality of fissile nuclear fuel assemblies in a central core region of a nuclear fission reactor core of a nuclear fission reactor. At a block 206 fissile material is bred in ones of a plurality of fertile nuclear fuel assemblies in the central core region of the nuclear fission reactor core. At a block 208 reactivity in the central core region is controlled. At a block 210 neutrons are absorbed in a peripheral core region. At a block 212 selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies are shuffled in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material. The method 200 stops at a block 214. Details will be set forth below by way of non-limiting examples. Referring to FIG. 9B, in some embodiments fissioning fissile nuclear fuel material in a plurality of fissile nuclear fuel assemblies in a central core region of a nuclear fission reactor core of a nuclear fission reactor at the block 204 may include generating in the central core region at least a predetermined amount of power in the nuclear fission reactor core at a block 216. Referring to FIG. 9C, in some embodiments absorbing neutrons in a peripheral core region at the block 210 may include absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at a block 218. Referring to FIG. 9D, in some embodiments absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at the block 218 may include breeding fissile material in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region at a block 220. Referring to FIG. 9E, in some embodiments absorbing neutrons in a peripheral core region at the block 210 may include absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at a block 222. Referring to FIG. 9F, in some embodiments absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at the block 222 may include absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region such that power produced in the peripheral core region is maintained below a predetermined power level at a block 224. Referring to FIG. 9G, in some embodiments absorbing neutrons in a peripheral core region at the block 210 may include absorbing neutrons in others of the plurality of fertile nuclear fuel assemblies in the peripheral core region and absorbing neutrons in a plurality of neutron absorber assemblies in the peripheral core region at a block 226. Referring to FIG. 9H, in some embodiments at a block 228 the nuclear fission reactor may be shut down before shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies between the central core region and the peripheral core region. Referring to FIG. 9I, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material at the block 212 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies between the central core region and the peripheral core region in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material at a block 230. Referring to FIG. 9J, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at the block 212 may include replacing selected ones of the plurality of fissile nuclear fuel assemblies of the central core region with selected ones of the plurality of fertile nuclear fuel assemblies of the central core region and with selected others of the plurality of fertile nuclear fuel assemblies of the peripheral core region at a block 232. Referring to FIG. 9K, in some embodiments shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at the block 212 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies having a predetermined burnup level and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 234. Referring to FIG. 9L, in some embodiments controlling reactivity in the central core region at the block 208 may include controlling reactivity in the central core region with a plurality of movable reactivity control assemblies at a block 236. Referring to FIG. 9M, in some embodiments controlling reactivity in the central core region at the block 208 may include shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 238. Referring to FIG. 9N, in some embodiments controlling reactivity in the central core region at the block 208 may include controlling reactivity in the central core region with a plurality of movable reactivity control assemblies and shuffling selected ones of the plurality of fissile nuclear fuel assemblies and selected ones and selected others of the plurality of fertile nuclear fuel assemblies at a block 240. Referring to FIG. 9O, in some embodiments reactor coolant may be flowed through a first plurality of reactor coolant flow orifices in the central core region at a block 242 and reactor coolant may be flowed through a second plurality of reactor coolant flow orifices in the peripheral core region at a block 244. Referring to FIG. 9P, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 242 may include flowing reactor coolant through a plurality of reactor coolant flow orifice groups in the central core region at a block 246. In some embodiments flow rate through a selected one of the plurality of reactor coolant flow orifice groups may be based upon a power profile at a radial location of the selected one of the plurality of reactor coolant flow orifice groups. In some embodiments flow rate through the second plurality of reactor coolant flow orifices may include a predetermined flow rate based upon power level in the peripheral core region. Referring to FIG. 9Q, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 242 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 244 may include maintaining substantially steady flow of reactor coolant through ones of the first and second pluralities of reactor coolant flow orifices at a block 248. Referring to FIG. 9R, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 242 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 244 may include varying flow of reactor coolant through others of the first and second pluralities of reactor coolant flow orifices at a block 250. Referring to FIG. 9S, in some embodiments flowing reactor coolant through a first plurality of reactor coolant flow orifices in the central core region at the block 242 and flowing reactor coolant through a second plurality of reactor coolant flow orifices in the peripheral core region at the block 244 may include maintaining substantially steady flow of reactor coolant through ones of the first and second pluralities of reactor coolant flow orifices and varying flow of reactor coolant through others of the first and second pluralities of reactor coolant flow orifices at a block 252. Referring to FIG. 9T, in some embodiments flow of reactor coolant through at least one of the shuffled nuclear fuel assemblies may be varied at a block 254. Referring to FIG. 9U, in some embodiments varying flow of reactor coolant through at least one of the shuffled nuclear fuel assemblies at the block 254 may include rotating at least one of the shuffled nuclear fuel assemblies at a block 256. Referring to FIG. 9V, in some embodiments ones of the plurality of neutron absorber assemblies may be moved among a plurality of locations in the peripheral core region at a block 258. In some embodiments the plurality of locations in the peripheral core region may include a plurality of predetermined radial locations in the peripheral core region that are selectable based upon a predetermined burnup level of ones of the fissile nuclear fuel assemblies that have been shuffled into the peripheral core region. Referring to FIG. 9W, in some embodiments at a block 260 ones of the plurality of fissile nuclear fuel assemblies and ones and others of the plurality of fertile nuclear fuel assemblies may be selected for shuffling in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material. In some embodiments selecting ones of the plurality of fissile nuclear fuel assemblies and ones and others of the plurality of fertile nuclear fuel assemblies for shuffling in a manner that establishes a standing wave of breeding fissile nuclear fuel material and fissioning fissile nuclear fuel material may be based upon at least one operational datum chosen from neutron flux data, fuel assembly outlet temperature, and fuel assembly flow rate. Given by way of overview and referring now to FIG. 10A, a method 300 is provided for managing excess reactivity in a nuclear fission reactor. The method 300 starts at a block 302. At a block 304, criticality with a positive quantity of reactivity is achieved in a central core region of a reactor core of a nuclear fission reactor. At a block 306 the quantity of reactivity is increased until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core. At a block 308 the increase in reactivity is compensated for. The method 300 stops at a block 310. Details will be set forth below by way of non-limiting examples. Referring to FIG. 10B, in some embodiments increasing the quantity of reactivity until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core at the block 306 may include monotonically increasing the quantity of reactivity until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core at a block 312. Referring to FIG. 10C, in some embodiments increasing the quantity of reactivity until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core at the block 306 may include increasing amount of fissile material in ones of the fuel assemblies of the reactor core until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core at a block 314. Referring to FIG. 10D, in some embodiments increasing amount of fissile material in ones of the fuel assemblies of the reactor core until a predetermined burnup level is achieved in selected ones of fuel assemblies in the reactor core at the block 314 may include breeding fissile fuel material from fertile fuel material at a block 316. Referring to FIG. 10E, in some embodiments compensating for the increase in reactivity at the block 308 may include inserting neutron absorbing material into the central core region at a block 318. Referring to FIG. 10F, in some embodiments inserting neutron absorbing material into the central core region at the block 318 may include inserting control rods into the central core region at a block 320. Referring to FIG. 10G, in some embodiments inserting neutron absorbing material into the central core region at the block 318 may include replacing selected fissile fuel assemblies in the central core region with fertile fuel assemblies from a peripheral core region of the reactor core at a block 322. Referring to FIG. 10H, in some embodiments inserting neutron absorbing material into the central core region at the block 318 may include inserting control rods into the central core region and replacing selected fissile fuel assemblies in the central core region with fertile fuel assemblies from a peripheral core region of the reactor core at a block 324. All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in any Application Data Sheet, are incorporated herein by reference, to the extent not inconsistent herewith. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. In some instances, one or more components may be referred to herein as “configured to,” “configured by,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Those skilled in the art will recognize that such terms (e.g. “configured to”) can generally encompass active-state components and/or inactive-state components and/or standby-state components, unless context requires otherwise. While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. Those skilled in the art will appreciate that the foregoing specific exemplary processes and/or devices and/or technologies are representative of more general processes and/or devices and/or technologies taught elsewhere herein, such as in the claims filed herewith and/or elsewhere in the present application. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
	abstract	In an ion implanting apparatus 10 including a separation slit 20 which receives an ion beam 1 having passed through a mass-separation electromagnet 17 and allows a desired type of ion to selectively pass therethrough, the separation slit 20 is operable to vary a shape of a gap through which the ion beam 1 passes. In addition, the ion implanting apparatus 10 includes a variable slit 30 which is disposed between an extraction electrode system 15 and the mass-separation electromagnet 17 so as to form a gap through which the ion beam 1 passes and is operable to vary a shape of the gap so as to shield a part of the ion beam 1 extracted from the ion source 12. The ion implanting apparatus 10 may include both or one of the separation slit 20 and the variable slit 30.
051529572	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter recovering apparatus for recovering a small foreign matter present in a space inaccessible by an operator and, in particular, a space of fuel assembly for nuclear power generation. 2. Description of the Related Art It has been generally known to use, for example, a magic hand and forceps as a means for recovering foreign matter trapped in a narrow space. Further, it has also been known to use, as means for recovering a foreign matter trapped in a normally inaccessible or hard-to-access space, a medical endoscope for immediately eliminating foreign matter by a biopsy forceps as well as a vacuum for vacuum-sucking foreign matter by a nozzle from a distant location. The endoscope is guided into the human body cavity to photograph the interior of the internal organs of a human being or remotely controlled from outside the human body to remove its diseased region by the forceps so that a diagnostic treatment is made from within the human body. In nuclear power generation, use is made of a fuel assembly 201 as shown in FIG. 19. The fuel assembly 201 is comprised of pipe-like fuel elements 202, . . . filled with nuclear fuel and has a full length of, for example, about 4 m with clearances 203, . . . of, for example, 2 to 3 mm created among the respective fuel elements 202, . . . . FIG. 19 shows the fuel assembly comprised of 8.times.8 fuel elements. In FIG. 19, reference numerals 204 and 205 show upper and lower tying plates, respectively. The fuel elements 202, . . . are held, by the upper and lower tying plates 204 and 205, at their upper and lower end portions. In FIG. 19, reference numeral 206 shows a plurality of spacers (only one of them is shown) disposed in a longitudinal direction of the fuel elements 202 such that they are held partway in the longitudinal direction of the fuel elements 202, . . . . The spacer 206 includes a mechanism for individually holding the fuel elements 202, . . . . External springs 207, . . . are disposed between the upper ends of the fuel pairs 202 and the upper tying plate 204. The fuel assembly 201 is held, prior to use, for example, in a fuel storage pool 208 as shown in FIG. 20, and suspended at a water depth of about 10 m. Further, the fuel assembly 201 may be temporarily held in the storage pool 208 in the event of a nuclear reactor failure, etc., so that it is inspected for its defect. Therefore, the fuel assembly can be held in the pool not only before its use but also at any necessary time during its use. In the case where foreign matter, such as screws and metal pieces, is trapped in the fuel assembly 201 in the pool 208, it is necessary to recover it, but the fuel assembly 201 is suspended in the storage pool at the water depth of 10 m under a high pressure environment where there exits radiation of high intensity. The clearances 203 among the fuel elements 202 are each created on the order of as small as 2 to 3 mm. It is, therefore, not possible to immediately recover such foreign matter by hand. It is required that the means for recovering the foreign matter be remotely controlled at a position adequately spaced apart from the fuel assembly 201. It may be considered that the aforementioned endoscope is applied to the recovery of the foreign matter in the fuel assembly 201. The medical endoscope can be directly operated, while viewing the foreign matter through an eyepiece, in which case the instrument is remotely controlled at an operation distance of, for example, about 1 m. The control of the instrument direction, driving of the forceps, etc., are done with the use of an operation force transmitted through a flexible wire. Further, the endoscope is usually so set to have 5 mm in external diameter. It is, therefore, difficult for the endoscope to recover a small foreign matter at a position adequately remote from the fuel assembly 201, that is, to guide the instrument's tip into the fuel assembly 201 and set it there, guide the instrument's tip or forceps into the clearance 203 of the fuel elements 202, and accurately drive the forceps and recover the foreign matter. For a means for vacuum-sucking a foreign matter without a visual inspection, it is difficult to accurately locate its vacuum nozzle at a predetermined position of an object of interest. SUMMARY OF THE INVENTION It is accordingly the object of the present invention to provide a foreign matter recovering apparatus which can positively recover a small foreign matter present in an environment not accessible by hand, while being visually identified. According to the present invention, there is provided a foreign matter recovering apparatus comprising: a body for approaching a fuel assembly; a body fixing section for fixing the body to the fuel assembly for positioning; a moving mechanism section movable relative to the body; a recovering working unit adapted to be moved by the moving mechanism section to gain access to very small clearances of the fuel assembly to allow any foreign matter to be recovered thereby; and a remote control section for remotely controlling the working unit on the basis of an image representing a working state of the working unit to operate it properly.
	summary
	claims	1. A method for radiation protection, comprising:providing a garment that substantially contours to an operator's body, wherein the garment is operable to protect a portion of the operator's body from radiation, and wherein the garment is suspended by a curved frame attached to a suspension component that reduces a portion of weight of the garment for the operator, a semi-rigid belt secured to the frame in a substantially horizontal orientation and which provides substantial contour to the garment about a portion of the operator's body, and a release mechanism for manipulating the belt that offers an entry into the garment. 2. The method of claim 1, wherein the release mechanism comprises a quick release that allows the operator to disengage from the garment using a single hand movement. 3. The method of claim 1, wherein the belt opens to allow the operator to enter the garment, and wherein the operator, in entering and exiting the garment, is able to limit his contact to components on or near a front of the garment such that the operator can operate the release mechanism for the garment without losing sterility. 4. The method of claim 1, wherein the release mechanism includes a spring mechanism that exerts a force on the belt. 5. The method of claim 1, wherein the garment allows the operator, who is wearing the garment, to move freely in X, Y, and Z spatial planes, and wherein the garment is substantially weightless to the operator. 6. The method of claim 1, wherein the garment includes a sleeve on at least one side of the garment. 7. The method of claim 1, further comprising a face shield, the face shield being substantially weightless to the operator, and wherein the face shield provides additional radiation protection. 8. The method of claim 1, wherein the suspension component is mounted to a ceiling. 9. The method of claim 1, wherein the suspension component is a selected one of a group of components the group consisting of:a) an articulating arm or trolley;b) a jib crane;c) an articulating bridge crane;d) a bridge crane;e) a reaction arm or power assisted mechanism;f) a spring motor;g) a telescopic bridge;h) a monorail suspension system; andi) balancer. 10. The method of claim 1 further comprising a sterile cover for protecting a substantial portion of the garment.
	claims	1. An extreme ultraviolet light source comprising:a production site producing extreme ultraviolet radiation;a collector optics (6) for collimating the extreme ultraviolet radiation produced at the production site;a vacuum applied at a center of the collector optics (6) that actively pumps out of the device; anda pressurized influx of gas that forms a gas curtain between the production site and the collector optics (6) to protect the collector optics (6) from debris (4) generated at the production site, wherein the gas influx is directed in a way that it follows the surface of the collector optics (6), wherein the gas is used simultaneously as a coolant for the collector optics (6) by conducting it along a back side of the collector optics (6) before it reaches an injection point (12) where it begins to protect the surface of the collector optics (6) from deposition and erosion by debris, and is injected at the injection point (12) with a maximum stagnation temperature of 700 K, andwherein internal cooling is tailored to match heat flux on the surface of the collector optics (6) by controlling the mass flow of the gas on the back side of the collector optics (6) with an arrangement of turbulators (18). 2. An extreme ultraviolet light source according to claim 1, further comprising a plurality of axis-symmetric injection nozzles (17) positioned around the outer border of the collector optics (6) to produce the gas influx. 3. An extreme ultraviolet light source according to claim 1, further comprising one axis-symmetric injection nozzle (17) covering the whole outer border of the collector optics (6) to produce the gas influx. 4. An extreme ultraviolet light source according to claim 1, wherein the gas comprises a noble gas selected from the group containing Hydrogen, Helium, Argon, Neon, Krypton, Xenon, Nitrogen, Chlorine, Fluorine, Bromine, and Iodine. 5. An extreme ultraviolet light source according to claim 1, wherein the gas influx speed is very high, and preferably significantly above the speed of the sound at an injection point (12). 6. An extreme ultraviolet light source comprising:a production site producing extreme ultraviolet radiation;a collector optics (6) for collimating the extreme ultraviolet radiation produced at the production site; anda pressurized influx of gas that forms a gas curtain between the production site and the collector optics (6) to protect the collector optics (6) from debris (4) generated at the production site, wherein the gas influx is directed in a way that it follows the surface of the collector optics (6), wherein the gas is used simultaneously as a coolant for the collector optics (6) by conducting it along a back side of the collector optics (6) before it reaches an injection point (12) where it begins to protect the surface of the collector optics (6) from deposition and erosion by debris, and is injected at the injection point (12) with a maximum stagnation temperature of 700 K, and further wherein internal cooling is tailored to match heat flux on the surface of the collector optics (6) by controlling the mass flow of the gas on the back side of the collector optics (6) and wherein matching of the heat flux is achieved by an arrangement of turbulators (18) on the backside of the collector optics (6). 7. An extreme ultraviolet light source according to claim 1, wherein the gas influx further comprises an additional component that is tangent to the border of the collector optics (6) so that a swirl is induced in the flow of the gas curtain. 8. An extreme ultraviolet light source according to claim 7, wherein a tangential angle at an injection point (12) relative to the radial line is between 0° and 45°. 9. An extreme ultraviolet light source according to claim 1, wherein matching of the heat flux is achieved by a geometric arrangement of holes (10) on the backside of the collector optics (6). 10. An extreme ultraviolet light source according to claim 1, wherein the gas is injected with an exit static pressure of at least the pressure in the extreme ultraviolet light production site. 11. An extreme ultraviolet light source according to claim 1, wherein the gas is further used to clean the surface of the collector optics (6). 12. An extreme ultraviolet light source according to claim 11, wherein the gas is ionized. 13. An extreme ultraviolet light source according to claim 1, wherein the collector optics (6) comprises a collector mirror containing a hole (7) in its center. 14. An extreme ultraviolet light source according to claim 1, wherein the gas influx is injected in parallel to the collector optics (6) such that it has a radial component with respect to the outer border of the collector optics (6). 15. An extreme ultraviolet light source according to claim 1, further comprising a separate (19), closed-loop, collector cooling system (8, 9, 10, 11). 16. An extreme ultraviolet light source according to claim 6, further comprising a vacuum applied at the center of the collector optics (6) that actively pumps out of the device.
053234324	claims	1. An apparatus for assembling fuel rods into a fuel assembly, comprising a plurality of longitudinally extending fuel rods firmly held in grid cells of a plurality of grids, said apparatus comprising: (a) a longitudinally extending fuel rod magazine containing said plurality of fuel rods; (b) a plurality of fluid-pressure operated loading cylinders provided on said fuel rod magazine, for loading specific fuel rods of said plurality of fuel rods into said grid cells, wherein each of said loading cylinders is disposed coaxially with a corresponding one of said plurality of fuel rods contained in said fuel rod magazine so as to push said corresponding one of said plurality of fuel rods from said fuel rod magazine to said grid cells; (c) a plurality of grid support frames spaced apart and disposed in the longitudinal direction of said assembly to support said plurality of grids so that said grid cells face in the direction of said fuel rods; wherein: a plurality of fuel rod support rollers are disposed in a longitudinal direction between said fuel rod magazine and said grid support frames, each of said plurality of fuel rod support rollers providing vertical support of said plurality of fuel rods from the underside thereof so as to prevent a sagging of the fuel rods; and each of said fuel rod support rollers comprise means for moving said support rollers in a vertical direction so as to enable a relative positioning of said support rollers with respect to said grid cells, such that a vertical position of said support rollers corresponds to a level of fuel rods in said fuel rod magazine and enables the loading of specific fuel rods into a corresponding coaxial grid cell. 2. A fuel rod assembling apparatus as claimed in claim 1, wherein said fluid-pressure operated loading cylinder is an air-pressure operated loading cylinder. 3. A fuel rod assembling apparatus as claimed in claim 1, wherein said plurality of support frames are disposed on the top surface of a rotating base extending in the direction of said fuel rods, wherein said rotating base is provided with a power means for raising said rotating base from a horizontal position to a vertical position. 4. A fuel rod assembling apparatus as claimed in claim 1, wherein a support frame farthest removed from said fuel rod magazine is provided with a stopper, on the exit-side of said support frame, to align the position of said plurality of fuel rods by contacting the tip end of said plurality of fuel rods. 5. A fuel rod assembling apparatus as claimed in claim 4, wherein said stopper disposed at the farthest position from said fuel rod magazine is provided with a positioning plate, at the exit-side of a support frame situated farthest from said fuel rod magazine; and a positioning cylinder which adjusts the position of said positioning plate transversely to the direction of fuel rods.
	summary
	abstract	An EUV collector is rotated between or during operations of an EUV photolithography system. Rotating the EUV collector causes contamination to distribute more evenly over the collector's surface. This reduces the rate at which the EUV photolithography system loses image fidelity with increasing contamination and thereby increases the collector lifetime. Rotating the collector during operation of the EUV photolithography system can induce convection and reduce the contamination rate. By rotating the collector at sufficient speed, some contaminating debris can be removed through the action of centrifugal force.
040240177	summary	The present invention relates to a method of, and apparatus for, measuring burn-up of nuclear fuel in a nuclear reactor. Safety as well as economic conditions make it imperative to have accurate knowledge of the local burn-up in nuclear power reactors and thus to be able dependably to avoid power density peaks, on the one hand, and to adjust the operating conditions to optimum fuel utilization, on the other hand, when the local burn-up of the nuclear fuel in the reactor core is known. Furthermore, the inherent stability of the reactor depends on the form of the neutron flux distribution and, therefore, on the burn-up condition. In essence, conventional on-line methods for determining the burn-up in a nuclear reactor are based on a time integral of the neutron flux or on a time integral of the power density, which requires the continuous measurement of the neutron flux in the core and storing the measured data. This is disadvantageous not only because of the possible loss of data but this method is also inaccurate if large control rod movements of long duration were necessary between the individual measurements, for instance at irregular cycles or peak power cycling. It is the primary object of this invention to provide a method and apparatus avoiding these disadvantages of conventional nuclear fuel burn-up measurements. The above and other objects are accomplished in accordance with the invention by producing two measuring signals, each measuring signal being the function of the flux density of a different neutron group or energy, and computing the burn-up by comparing the two signals.
053176111	abstract	A modular fuel assembly for a nuclear thermal engine includes a plurality of fuel elements each having a fueled, truncated conical shell and an unfueled peripheral lip at the base of the shell with radial passages there-through. The fuel elements are nested with the lips seating one on top of another to form a stack of fuel elements with frusto-conical flow passages between the shells of adjacent fuel elements which are divided into channels by ribs on the conical shells. The stack of fuel elements is mounted in a cylindrical housing with the bases of the shells facing a central inlet opening at one end of the housing. Propellant enters the central inlet opening, is deflected radially outward by a deflector into an annular flow distribution channel from which it flows radially inward through the passages in the fuel element lips, through the flow channels of frusto-conical passages between the fueled shells where it is heated, and out through a central exhaust passage.
062467395	abstract	Passive aerosol retention apparatus positioned in the connecting vents of a nuclear reactor containment are described. The aerosol retention apparatus minimizes aerosol transport from the lower drywell to the upper drywell of the reactor containment. The retention apparatus includes a substantially cylindrical housing and a flow modulator positioned inside the housing and extending at least partially from a first end to a second end of the housing. The flow modulator includes a helically shaped baffle positioned in the housing so as to be coaxial with the housing. The baffle is coupled at each end to the housing by attachment bars.
	claims	1. A nuclear reactor core comprising:nuclear fuel comprising Pu-239;a neutron moderator which behaves as an Einstein oscillator and as the temperature of the reactor increases said neutron moderator increases the energy of thermal neutrons into a Pu-239 neutron absorption resonance; anda neutron absorbing element with neutron absorption of 0.3 eV added to said nuclear reactor core, whereinsaid neutron absorbing element is different from a burnable poison used in the nuclear reactor core,said neutron absorbing element was added upon fueling the nuclear reactor core in an amount calculated to suppress, at any time during the life of the fuel, a reactivity gain with temperature due to said neutron moderator increasing the energy of thermal neutrons into a neutron absorption resonance of said Pu-239. 2. The nuclear reactor core of claim 1, wherein said neutron moderator comprises ZrHx, where x is between 1.5 and 1.7. 3. The nuclear reactor core of claim 1, wherein said neutron moderator comprises YH2. 4. The nuclear reactor core of claim 1, wherein said neutron moderator comprises TiH2. 5. The nuclear reactor core of claim 1, wherein said neutron moderator comprises ThH2. 6. The nuclear reactor core of claim 1, wherein said Pu-239 is 0.4 weight percent or more of said nuclear fuel. 7. The nuclear reactor core of claim 1, wherein said Pu-239 is in the range of 0.1 to 1.0 weight percent of said nuclear fuel. 8. The nuclear reactor core of claim 1, wherein said neutron absorbing element is erbium. 9. The nuclear reactor core of claim 1, wherein said Pu-239 is in the range of 1.0 to 5.0 weight percent of said nuclear fuel. 10. The nuclear reactor core of claim 1, wherein said Pu-239 is in the range of 5.0 to 10.0 weight percent of said nuclear fuel. 11. The nuclear reactor core of claim 1, wherein said Pu-239 is in the range of 10.0 to 20.0 weight percent of said nuclear fuel. 12. The nuclear reactor core of claim 1, wherein said Pu-239 is in the range of 20.0 to 100.0 weight percent of said nuclear fuel. 13. The nuclear reactor core of claim 1, wherein said neutron absorbing element has an absorption cross section of at least 100 barns. 14. The nuclear reactor core of claim 1, wherein said neutron absorbing element has an absorption cross section of at least 500 barns. 15. The nuclear reactor core of claim 1, wherein said neutron absorbing element has an absorption cross section of great than 1000 barns. 16. A method of controlling a nuclear reactor comprising:providing nuclear fuel comprising Pu-239 in a core of the nuclear reactor;providing a neutron moderator which behaves as an Einstein oscillator and as the temperature of the nuclear reactor increases said neutron moderator increases the energy of thermal neutrons into a neutron absorption resonance of said Pu-239; andadding a neutron absorbing element with neutron absorption of 0.3 eV to said core, whereinsaid neutron absorbing element is different from a burnable poison used in the core,said neutron absorbing element is added upon fueling the nuclear reactor core in an amount calculated to suppress, at any time during the life of said nuclear fuel, a reactivity gain with temperature due to said neutron moderator increasing the energy of thermal neutrons into said neutron absorption resonance of said Pu-239.
	claims	1. A substrate treatment device comprising: at least two dielectric barrier discharge lamps; a substrate which is moved in relation to the at least one dielectric barrier discharge lamp thereby irradiating the surface of the substrate with UV light from the at least two dielectric barrier discharge lamps, wherein a length for the at least two dielectric barrier discharge lamps in the lengthwise direction is less than a length of the transport direction of the substrate; a first area of the substrate which has been irradiated by one dielectric barrier discharge lamp; a second area of the substrate which has been irradiated by an other dielectric barrier discharge lamp, such that during moving of the substrate, the first and second areas have an overlapping portion; and a light screening means that substantially unifies light between the two lamps. 2. A substrate treatment device using dielectric barrier discharge lamps which are transported with respect to a substrate to be irradiated, and which irradiate the surface of this substrate with UV light comprising: at least two dielectric barrier discharge lamps, wherein the length of the dielectric barrier discharge lamps in a lengthwise direction is less than a length in the direction perpendicular to the transport direction of the substrate; a first area of the substrate which has been irradiated by one dielectric barrier discharge lamp and a second area of the substrate which has been irradiated by the other dielectric barrier discharge lamp, such that during transport of the substrate the first and second areas have an overlapping portion; and a light screening means which that substantially unifies light between the two dielectric barrier discharge lamps. 3. The substrate treatment device of claim 1 , wherein light screening means are arranged such that the amount of irradiation per unit of area on the substrate becomes essentially uniform after transport treatment. claim 1 4. The substrate treatment device of claim 2 , wherein the light screening means are arranged such that the amount of irradiation per unit of area on the substrate becomes essentially uniform after transport treatment. claim 2 5. The substrate treatment device of claim 1 , wherein the dielectric barrier discharge lamps are located in an essentially box-shaped lamp unit, with one side provided with light transmission windows, and wherein the respective light screening means is a light screening plate which is located in the light transmission window. claim 1 6. The substrate treatment device of claim 2 , wherein the dielectric barrier discharge lamps are located in an essentially box-shaped lamp unit, with one side provided with light transmission windows, and wherein the respective light screening means is a light screening plate which is located in the light transmission window. claim 2
	abstract	Some embodiments include a method comprising: flowing a molten salt out of a molten salt reactor at a first temperature, heating the molten salt reactor to a second temperature above the melding point of the second salt mixture causing the second salt mixture to melt; flowing the second salt mixture out of the molten salt reactor; flowing a third salt mixture into the molten salt reactor; and cooling the molten salt reactor from the second temperature to a third temperature causing the third salt mixture to solidify on the interior surface of the housing. In some embodiments, the molten salt may include a first salt mixture comprising at least uranium. In some embodiments, the first temperature is a temperature above the melting point of the first salt mixture.
052276830	summary	BACKGROUND --FIELD OF INVENTION This invention relates to treatment of fluid in pipes to prevent corrosion, etc., specifically to a device employing externally mounted permanent magnets that generate an electrical current in fluid. The device may be used for potable fluids, process fluids, effluent fluids, heating and cooling waters, and hydrocarbon fuels, flowing in all commercial steel pipe. BACKGROUND--DESCRIPTION OF PRIOR ART Commercial steel pipe walls (normally of the types known as ANSI, ASME or API, schedule #40, etc.,) are too thick to be penetrated by the fields from usual permanent magnets such as to provide an internal field perpendicular to the flow direction of the fluid inside the pipe. While it may be theoretically possible to redesign existing permanent magnet devices to accomplish this task, any such attempts would fail or result in products of preposterous dimensions and cost. In other words, no existing devices are designed, or claim to be designed, to drive magnetic flux through a commercial steel pipe wall. Also none are designed, or claim to be designed, to drive magnetic flux through a commercial steel pipe wall, perpendicular to the flow direction of the fluid inside. Further none are designed, or claim to be designed, to drive magnetic flux through a commercial steel pipe wall, perpendicular to the flow direction of the fluid, inside, for the purpose of generating an electrical current in the fluid. Finally none, according to their published designs, materials, dimensional specifications, are capable of driving magnetic flux through commercial steel pipe walls, perpendicular to the flow direction of the fluid inside. To generate an electrical current by means of fluid flowing in a pipe, which fluid cuts a magnetic field, the magnetic field must be perpendicular to the direction of fluid flow. Placing magnets through or inside a steel pipe for this purpose is impractical, expensive, and loses the advantages of maintaining the steel pipe wall in its strong state. Similarly, placing magnets on the outside of nonferrous pipes loses the advantage of the strong steel pipes. No existing permanent magnet devices can provide a practical means of penetrating commercial steel pipe water or fuel systems with a perpendicular magnetic field. The wall of a steel commercial pipe easily absorbs magnetic flux. If any magnetic fields of existing devices could penetrate the pipe wall, such fields would quickly curve back to the wall, parallel to the fluid flow. PRESENT INVENTION The instant device magnetically penetrates all commercial steel pipe walls by means of its magnetic concentrators or condensers which utilize new magnetic materials and also benefit from an innovative, but simple, design, essential to their operation. The present device uses simple, innovative elements which have not heretofore been employed. The magnet utilized in the present device employs neodymium, the strongest magnetic material commercially available. It provides a flux density of 12,000 gauss, or higher. This provides sufficient magnetic flux for the condenser pole pieces to be designed in a practical way so that their steel contacts can be saturated with the maximum magnetic flux that the steel in the poles and the pipe wall can carry. The pole piece's contacts are made to be three times the thickness of the pipe wall. This enables the condenser pole pieces to deliver three times the lines of magnetic flux that the pipe wall can carry. The surplus flux lines burst through the pipe wall, in their attempt to flow through it, to the other pole to complete the magnetic circuit. The device employs two condenser pole pieces. The other pole of the first condenser is further away than the distance across the inside of the pipe. This places the second and opposite condenser's opposing pole closer to the surplus lines of flux than the first condenser's opposite pole. The surplus magnetic flux takes the shortest path across the inside of the pipe to the opposite condenser. This creates a magnetic field inside the pipe. This magnetic field is perpendicular to the direction of flow of fluid inside the pipe. The flowing fluid is thereby forced to cut the magnetic lines of force, perpendicular, to the direction of flow. This generates an electrical current, in the fluid, according to the well established Faraday Effect. The device generates an electrical current in a flowing fluid or gas. During generation, the steel pipe becomes negative and a "field" or "stator" of a generator. The flowing fluid or gas becomes a positive "armature" or "rotor". OBJECTS AND ADVANTAGES The objects and advantages of the invention are therefore: 1. to provide direct power generation from a flowing fluid or gas, PA1 2. to protect steel and all other pipe systems from scale, corrosion and algae, PA1 3. to afford cathodic protection to all metal pipe systems, and PA1 4. to ionize molecules, in all fluids flowing in all pipe systems. PA1 (a) increased oxygen availability in water, PA1 (b) reduced surface tension, of water, PA1 (c) increased sudsing, in hard water, PA1 (d) increased solubility of water and other fluids; i.e., better dissolving and rinsing, PA1 (e) reduced bacteria and algae replication in water, fuels and other fluids, PA1 (f) increased precipitation and/or flotation of suspended solids in fluids, PA1 (g) compression of dissolved solids in fluids, PA1 (h) accelerated organic reactions in water and other fluids, PA1 (i) reduced biochemical oxygen demabd in effluent waters, PA1 (j) reduced suspended solids, in effluent waters, PA1 (k) accelerated and completed chlorine reactions in water sanitation, PA1 (l) elimination of commercial water treatment chemical pollution, PA1 (m) elimination of salt water softener pollution, PA1 (n) increased soil penetration by irrigation water, PA1 (o) increaded plant growth and crop yield, PA1 (p) increased efficiencies of metals ore leeching processes, PA1 (q) increased heat-transfer efficiencies in heating and cooling, PA1 (r) great reduction in cooling tower water bleed-off, PA1 (s) increased hydrocarbon fuel combustion efficiency, PA1 (t) increased hydrocarbon fuel injector life, PA1 (u) reduced pollution from hydrocarbon fuels combustion, PA1 (v) combined combustion of water and hydrocarbon fuel mixtures, and PA1 (w) possible combustion of water as a primary fuel component. Combinations of the above processes afford the following: Other objects are the nonchemical clearing of algae from pools, fountains, lakes, and waterways; the annual saving of billions of dollars spent on commercial water treatment chemicals, including commercial and domestic salt water softening, the elimination of their collective pollution; the annual saving of uncountable trillions of gallons of potable water, polluted by cooling towers and boilers, and the billions of dollars in annual savings from the elimination of their pollution; a very significant reduction of energy requirements from increased combustion, heating and cooling efficiencies; a tremendous reduction in air and water pollution; increased mining mineral yields; increased food production and quality; many more savings associated with, or as the result of, all of the above and the resulting improved quality of life to the ultimate advantage to all. Many more objects and advantages will become apparent from the following description and drawings.
052710548	claims	1. A nuclear fuel grid having a perimeter strip grid corner-piece of increased flatness having at least two flat plane side sections on either side of a transverse corner bend and having a continuous corner bend in said perimeter strip along a line of varying radii in its transverse direction with the outer longitudinal end portions of said bend having a grater radius than its inner portions; said perimeter strip characterized by: an elongated transverse fully open slot in said perimeter strip spaced from said bend line in a flat side section thereof; said transverse slot extending such that its entire perimeter lies in one flat plane and there is an equal slot perimeter length of said open slot on either side of the longitudinal center line of said flat section. 2. The perimeter strip of claim I in which the length of said slot is approximately 1/3 to 1/2 of the width of said flat section. 3. The perimeter strip of claim 1 in which the width of said slot is less than twice the thickness of the strip material. 4. The perimeter strip of claim I in which there are transverse slots in each of the flat side sections on either side of the bend line. 5. The perimeter strip of claim I in which a flat side section is interrupted by arches and springs for fuel rod support and pilot holes, and the slot is adjacent said arches on one side of said bend line, only.
	claims	1. A method for neutralizing a weapon containing a chemical payload using a neutron generator, wherein the neutron generator comprises:a low-voltage power source;a high-voltage power source;a vacuum pump;a positively-biased cylindrical vacuum chamber, operatively connected to the vacuum pump, the vacuum chamber containing:a fuel source;a platinum grid;a concentric pair of do rings operatively connected to the low-voltage power source;a first negatively-biased accelerating grid operatively connected to the high voltage source;a platinum enriched lithium mesh;a lithium blanket surrounding the lithium mesh;a second negatively-biased accelerating grid operatively connected to the high voltage source;wherein the vacuum chamber is surrounded by a neutron reflector, except for a bare region which comprises: a region with two polyethylene sheets; a region with one polyethylene sheet; and a region with no polyethylene sheets;the method comprising:locating a chemical weapon;generating a moderated neutron beam with the neutron generator; andtargeting the chemical weapon with the moderated neutron beam for a period of time. 2. The method of claim 1, wherein the period of time is calculated based upon measurements of the chemical payload. 3. A method for neutralizing a weapon containing a chemical explosive using a neutron generator, wherein the neutron generator comprises:a low-voltage power source;a high-voltage power source;a vacuum pump;a positively-biased cylindrical vacuum chamber, operatively connected to the vacuum pump, the vacuum chamber containing:a fuel source;a platinum grid;a concentric pair of dc rings operatively connected to the low-voltage power source;a first negatively-biased accelerating grid operatively connected to the high voltage source;a platinum enriched lithium mesh;a lithium blanket surrounding the lithium mesh;a second negatively-biased accelerating grid operatively connected to the high voltage source;wherein the vacuum chamber is surrounded by a neutron reflector, except for a bare region which comprises: a region with two polyethylene sheets; a region with one polyethylene sheet; and a region with no polyethylene sheets;the method comprising:locating a chemical explosive;generating a moderated neutron beam with the neutron generator; andtargeting the chemical explosive with the moderated neutron beam for a period of time. 4. The method of claim 3, wherein the period of time is calculated based upon measurements of the chemical explosive.
	description	This is a continuation of application Ser. No. 10/307,033 filed Nov. 27, 2002, which is a division of application Ser. No. 10/000,374 filed Oct. 23, 2001. 1. Field of the Invention This disclosure is related to radiation measurements using scintillation type radiation detectors, and more specifically related to apparatus and methods for measuring radiation in a borehole environment using a YAlO3:Ce (YAP) scintillation crystal. 2. Background of the Art Scintillation type radiation detectors have been used for decades in a wide variety of applications. Radiation absorbed by a scintillation crystal emits a pulse of light or “scintillates”. The intensity of light is a function of energy deposited within the crystal by the absorbed radiation. A measure of light intensity can, therefore, be related to the energy of radiation absorbed by the scintillator. A measure of the number of scintillations per unit time can be related to the intensity of radiation absorbed by the scintillation crystal. In fabricating a scintillation type radiation detector, a scintillation crystal is optically coupled to a light sensitive device that responds to the number and to the intensity of scintillations produced within the crystal. Phomultiplier tubes (PMT) are commonly used as light sensitive devices. A PMT converts scintillations from the coupled crystal into electrical pulses. A pulse is typically generated for each scintillation. The magnitude of the pulse is proportional to the intensity of the scintillation. A count per unit time of pulses can, therefore, be related to the intensity of radiation impinging upon the crystal. Measures of magnitudes of the pulses can, therefore, be related to corresponding energies of the radiation absorbed by the crystal. Alternately, scintillation crystals can be optically coupled to other types of light sensitive devices such as photodiodes, and intensity and energy of impinging radiation can be determined from electrical outputs of these devices. The scintillation process is not instantaneous and, in fact, the scintillation emission intensity follows an exponential decay. Thallium activated sodium iodide, or NaI(Tl), is a commonly used material in scintillation type gamma radiation detectors. The decay constant of a scintillation produced within a NaI(Tl) crystal by impinging gamma radiation is about 230 nanoseconds (ns). If the intensity of radiation impinging upon the crystal is sufficiently intense to generate a subsequent scintillation pulse before the previous scintillation pulse has decayed to a negligible level, the scintillation pulses will essentially “sum” within the crystal. This is commonly referred to as pulse “pile-up”. As an example, two pulses of equal intensity (induced by two gamma rays of equal energy) which pile-up within a detector system will produce a single electrical pulse output with a magnitude greater than a pulse that would be produced by a single gamma ray. Since pulse magnitude is related to radiation energy, pulse pile-up typically results in an erroneous radiation energy measurement. Furthermore, since the pulses “sum” as a single rather than a multiple radiation detector events, pulse pile-up results in erroneous radiation intensity measurements in high intensity gamma ray fluxes. It is, therefore, highly desirable to utilize a scintillation crystal with a minimum light decay constant when measuring energy and intensity of high intensity gamma radiation fluxes. As an example, there is a class of borehole instruments that employs a source of pulsed neutrons and one or more scintillation detectors. Certain measurements, such as inelastic scatter gamma ray measurements, require that the one or more detectors be operated during the neutron burst. This exposes the one or more detectors to extremely high fluxes of gamma ray and other types of radiation. The light decay constant of the scintillation material is, therefore, a critical design parameter in this type of instrumentation. Many measurement systems using scintillation type gamma ray detectors are also exposed to neutron fluxes. As in the example above, a large variety of borehole instruments used to measure properties of earth formation penetrated by the borehole employ one or more scintillation gamma ray detectors and a neutron source. The neutron source, whether pulsed or continuous, induces gamma radiation within the formation through several types of reactions including inelastic scatter and thermal capture. This induced gamma radiation is sensed by the one or more scintillation detectors and is used to determine formation and borehole parameters of interest. The scintillation detectors are also exposed to neutrons from the source, and especially to thermal neutrons generated in the borehole environs. These neutrons can produce radiation-emitting isotopes within the scintillation crystal. This is commonly referred to as crystal “activation”. Consider, as an example a scintillation detector comprising a NaI(Tl) crystal. The thermal neutron capture cross sections for the primary elemental constituents sodium (Na) and iodine (I) are 0.43 barns and 6.15 barns, respectively. Thermal neutrons impinging upon the NaI(Tl) detector produce 24Na and 128I within the scintillator through the 23Na(n,γ)24Na and 127I(n,γ)128I reactions, respectively. Both 24Na and 128I decay through beta emission with 128 I also decaying through electron capture. There is often gamma emission subsequent to the beta decay or electron capture. These radiations are generated within the NaI(Tl) crystal, and both the gamma and beta radiation induce scintillations within the crystal. These activation induced radiations are considered as “noise” in the measurement of formation properties using gamma radiation induced within the formation and borehole. It is, therefore, highly desirable to use a scintillation crystal with primary elemental constituents that do not readily “activate” when used in a system which also utilizes a neutron source. There are other considerations in selecting a scintillation crystal for borehole applications. The borehole environment is typically harsh in that pressures and temperatures are typically high. Borehole instruments are subjected to shock and vibrations as the instrument is typically conveyed within the borehole. Crystals such as NaI(Tl) are highly susceptible to shock induced cleavage, which typically worsens with constant vibration. Cleavage, in turn, results in deteriorating energy resolution and efficiency. As mentioned previously, temperature is usually elevated within a borehole, and typically varies with depth. In particular, variations in temperature can adversely affect crystal scintillation properties of a crystal which, in turn, can adversely affect subsequent radiation energy and intensity measurements. Some scintillation crystals, such as NaI(Tl), are hygroscopic. This requires that the crystal be encased in a hermetically sealed container, which increases the overall dimensions of the crystal package for a given active crystal volume. This increase in size, or the resulting necessity to reduce the active volume of the crystal, can be a critical design factor in borehole instrument fabrication. Inherent crystal gamma ray resolution properties and overall efficiency properties are also factors in borehole logging instrument design. Other scintillation crystals have been used in borehole applications. Typically, these scintillation materials exhibit advantages over NaI(Tl) in some areas, but exhibit disadvantages in other areas. On such material is bismuth germinate (BGO), with properties well documented in the literature. The scintillation material cerium activated yttrium aluminum perovskite or YAlO3:Ce (YAP) has a density of 5.55 grams per cubic centimeter (g/cm3), an effective Z of 36, a light decay constant of 27 ns, light output of 45% of NaI at 25° C., 18,000 photons/MeV, emission peak of 350 nanometer (nm), and an index of refraction of 1.94. Thermal neutron cross sections for the major constituents of the crystal yttrium, aluminum and oxygen are 1.28 barns, 0.230 barns and 0.00019 barns, respectively. The activity produced by thermal neutron capture in yttruim is relatively long-lived so that decay radiation is negligible compared to that observed from iodine activation in NaI crystals. YAP has been used in the prior art in a number of non-borehole scintillation detector applications, and especially in the field of medical imaging. Typical prior art applications are summarized below. A gamma ray camera system comprising an array of YAP(Ce) scintillation crystals optically coupled to a position sensitive photomultiplier tube is disclosed in “YAP Multi-Crystal Gamma Camera Prototype”, K. Blazek et al, IEEE Transactions on Nuclear Science, Vol. 42, No. 5, October 1995. The multiple scintillation crystals are optically isolated from one another. A scintillator detector with multiple YAP crystals and other types of crystals is disclosed in “Blue Enhanced Large Area Avalanche Photodiodes in Scintillation Detection with LSO, YAP and LuAP Crystals”, M. Moszynski et al, IEEE Transactions on Nuclear Science, Vol. 44, No. 3, June 1997. Scintillator crystals are optically coupled to large area avalanche photodiodes. A high resolution positron emission tomograph (TierPET) for imaging small laboratory animals is discloses in “Recent Results of the TierPET Scanner”, S. Weber et al, IEEE Transactions on Nuclear Science, Vol. 47, No. 4, August 2000. The system is based on an array of YAP crystals. 20×20 arrays of 2×2×15 mm polished YAP crystals are optically coupled to a position sensitive PMT. U.S. Pat. No. 5,313,504 to John B. Czirr discloses the use of a YAP scintillator in a borehole instrument to monitor output of a neutron source that is also disposed within the borehole instrument. Since the YAP scintillator is used in a neutron source monitor system, the instrument is designed to maximize the response of the YAP scintillator to the neutron source and, conversely, to minimize the response of the YAP scintillator to the borehole environs. None of the above cited references discloses a system that is suitable for operation within a borehole to measure properties of the borehole environs. The scintillation material YAlO3:Ce (YAP) possesses many properties, as summarized above, which are ideally suited for use in scintillation type radiation detectors in borehole instrumentation. More specifically, YAP is rugged and less subject to shock and vibration damage when compared to other commonly used crystals such as NaI(Tl). YAP is not hygroscopic thereby eliminating the need of hermetic packaging required for NaI(Tl) crystals. This increases design flexibility in borehole instrumentation. YAP is relatively high density (5.55 g/cm3), and is of similar efficiency to NaI(Tl) over the integrated energy range of 0.1 to 9.5 MeV. The major constituents of YAP are less susceptible to thermal neutron activation than NaI(Tl). YAP is less susceptible to variation in temperature than NaI(Tl). Temperature properties of YAP are discussed in detail in “The Change of Gamma Equivalent Energy with Temperature for scintillation Detector Assemblies”, C. Rozsa, et al, Nuclear Science Symposium, 1999. Conference Record. 1999 IEEE, Volume: 2, 1999 Page(s): 686–690 vol.2. The change of relative light output of responses of YAP(Ce) scintillators to alpha and gamma radiation was investigated over the temperature range −20 degrees Centigrade (° C.) to 70° C. Probably the most significant characteristic of YAP, with respect to borehole instrumentation design, is the scintillation light decay constant which is approximately ten times less than that of NaI(Tl). This reduces the problem of pulse pile-up in high intensity radiation fields. In non-pileup conditions, energy resolution of NaI(Tl) is somewhat better across the entire spectrum than the resolution of YAP. In high intensity fluxes, however, where pulse pile-up is a significant factor in NaI(Tl) detectors, YAP detectors with significantly shorter light decay constant exhibits superior energy resolution. These properties are especially important in certain types of borehole instrumentation, which will be discussed in detail in subsequent sections of this disclosure. Borehole logging instruments or “logging tools” can be embodied in a variety of ways depending upon the desired borehole environs measurements. Tools detailed in this disclosure contain at least one radiation detector comprising a YAP scintillation crystal optically coupled to a light sensing device such as a photomultiplier tube (PMT), a photodiode, or the like, which converts scintillation intensity to an electrical pulse of proportional magnitude. The detector assembly is preferably enclosed within a pressure housing for protection from the harsh borehole environment. The tool is conveyed along the borehole by means of a wireline, a drill string or a slick line. Scintillation detector based formation evaluation instruments, whether wireline or logging while-drilling (LWD) tools, can be embodied to measure a wide variety of parameters. In one embodiment, the tool is used to measure only natural gamma radiation emitted by formation penetrated by the borehole, or gamma radiation emitted by materials such as radioactive “tagged” tracer materials within or in the immediate vicinity of the borehole. Other classes of formation evaluation tools contain one or more sources of radiation, such as a neutron source, which induces a variety of reactions within the formation and borehole. Radiation produced by these reactions is typically measured by one or more scintillation detectors within the tool. Formation and borehole parameters of interest are then determined from the response of the one or more detectors. The source of radiation within the tool can be continuous or pulsed. Detectors are operated at specified times during a pulsed radiation cycle to optimize the measure of radiation from specific reactions of interest. This disclosure will be directed toward a YAP borehole scintillation detector embodied in a formation evaluation tool comprising a pulsed source of 14 MeV neutrons. It should be understood that the YAP borehole scintillation detector can effectively be embodied in borehole instruments containing other sources of radiation, and further embodied as a plurality of detectors. This disclosure will further be directed to a logging system wherein at least one YAP scintillation detector is operated during each neutron pulse thereby exposing the detector to an intense radiation flux. An additional embodiment of the YAP scintillator operates the YAP scintillation detector during the quiescent period between neutron pulses. Still further embodiments operate the detector during the pulse and during the quiescent periods between pulses, or operate the detector without the use of a source. Either gross count rate or spectral energy count rates can be measured by the disclosed logging system for conversion into borehole and formation parameters of interest. As an example, gamma radiation sensed by the YAP scintillation detector can be recorded in a plurality of energy ranges or “windows” and these window count rates can be related to specific reactions which, in turn, can be related to concentrations of specific elements within the formation penetrated by the borehole. Other types of radiation, such as beta radiation, can generate scintillations within a YAP scintillation crystal. This disclosure will, however, be directed primarily to systems which involve the measurement of gamma radiation. A borehole logging tool comprising YAP radiation detectors can be embodied in a variety of ways depending upon the desired borehole environs for the measurements. FIG. 1 illustrates a logging tool 11 comprising a YAP scintillation crystal 12 optically coupled to a light sensing device 14 such as a photomultiplier tube (PMT), a photodiode, or the like, which converts scintillation intensity to an electrical pulse of proportional magnitude. The light sensing device 14 is typically powered and controlled by an electronic package 16. The electronics package 16 can also contain data processing equipment, such as circuits to determine-the intensity and energy of radiation impinging upon and interacting with the scintillation crystal 12. The electronics package 16 can also contain computing means to transform radiation energy and intensity into parameters of interest. The scintillation crystal 12, light sensing device 14 and electronics package 16 are enclosed within a pressure housing 18 for protection from the harsh borehole environment. The tool is conveyed along a borehole 20 penetrating an earth formation 22 by a conveyance system including a member 24 which extends from the tool 11 to a surface conveyance unit 26. If the conveyance system is a wireline logging system, the member 24 is a wireline logging cable, and the surface conveyance unit 26 comprises wireline draw works and surface equipment well known in the art. If the conveyance system is a drilling rig, the member 24 is a drill pipe string and the surface conveyance 26 comprises a drilling rig, which is also well known in the art. Other conveyance systems, such as a slickline system, can be used to convey the tool 11 along the borehole 20. The surface conveyance unit 26 can also contain data processing equipment, such as circuits to determine the intensity and energy of radiation impinging upon and interacting with the scintillation crystal 12. The surface conveyance unit 26 can also contain computing means to transform radiation energy and intensity into parameters of interest. Embodied as the tool 11, typical measurements from the system would be naturally occurring gamma radiation emitted by the formation, or gamma radiation from radioactive tagged fluids and propants used in formation fracturing operations. FIG. 2 illustrates a YAP radiation detector embodied as a logging instrument 13 comprising a radiation source 42. The source can be an isotopic neutron source such as Americium-beryllium (Am—Be), a neutron generator, or any other type of radiation source, such as an isotopic gamma ray source or a high energy gamma ray source comprising an accelerator. It will be assumed that the source 42 is a neutron generator, which is operated to produce pulses of neutron of energy around 14 MeV. The source 42, along with a YAP scintillation crystal 32, an optically coupled light sensing device 34, and a controlling electronics package 36 are all disposed within a pressure housing 38. Shielding material 40 is typically used to minimize direct irradiation of the crystal 32 by the source 42. It should be understood that additional YAP detectors can be used within the pressure housing 38 to enhance measurements or to obtain additional measurements of interest. Still referring to FIG. 2, neutrons emitted by the source 42 induce a variety of reactions within the formation and the borehole environs. Radiation produced by these reactions are sensed by the YAP scintillation detector within the tool 13, and parameters of the formation 22 and the borehole 20 are determined from the response of the one or more detectors. The neutron source is pulsed for tool embodiments discussed below. Pulse duration and pulse repetition rate parameters are adjusted to optimize the neutron induced reactions of interest. Likewise, the YAP detector is operated at specified times during a pulsed radiation cycle to optimize the measure of radiation from specific reactions of interest. The electronics package 36, and the surface conveyance unit 26, can contain data processing equipment, such as circuits to determine the intensity and energy of radiation impinging upon and interacting with the scintillation crystal 32. The electronics package 36, and the surface conveyance unit 26, can also contain computing means to transform radiation energy and intensity into parameters of interest. The determination of formation saline water saturation from a measure of the rate of thermal neutron capture was first introduced commercially in the 1960s. This logging system is well known in the industry under the generic name “thermal neutron decay” log and by a variety of service names. FIGS. 3a and 3b illustrate conceptually the YAP detector embodied in a thermal neutron decay tool. FIG. 3a is a plot of neutron source output N as a function of time, and illustrates the neutron source pulse timing for the tool 13 embodied as a thermal neutron decay type logging system. Referring to both FIGS. 2 and 3, the source 42 is used to generate a sequence of neutron pulses 50 of time duration 56. The pulses 50 are repeated periodically after a time interval 54, with a quiescent time 52 being measured from the termination of a previous pulse to the initiation of a subsequent pulse. In typical formation and borehole conditions, the thermalization of fast neutrons from the 14 MeV source and subsequent capture of thermal neutrons by elements within the formation occurs at a rate with a half life of several hundred microseconds. The pulse repetition rate is typically about 1,000 pulses per second with a pulse width 56 of 50 to 100 μs. The quiescent period 52 is, therefore typically 900 to 950 μs. FIG. 3b is a plot 60 of the natural logarithm of gamma radiation intensity I measured as a function of time. During the time interval t0 to t1 when the neutron source 42 is operating, composite gamma radiation is quite intense as can be seen from the magnitude of the curve 60. This composite gamma radiation comprises gamma radiation from inelastic scatter reactions, and to a lesser extent gamma radiation from thermal capture reactions, naturally occurring gamma radiation from the borehole environments and even a small component of neutron induced activation within the YAP crystal 32. Since the thermalization and capture process is relatively slow, gamma radiation resulting primarily from thermal neutron capture reactions are measured with the YAP detector during at least two time intervals 62 and 64 occurring in the quiescent period 52 between neutron pulses 50. The detector is first operated starting at a time t2 and ending at a time t3 yielding a count 66 as illustrated graphically by the shaded area. The detector is again operated starting at a time t4 and terminated at a time t5 yielding a count 68, again as illustrated graphically by the shaded area. Radiation is typically not intense within these time intervals, therefore pulse pile-up is not a problem. The counts 66 and 68 are combined to obtain the parameter of interest (saline water saturation) using methods well known in the art. The determination of formation fresh water saturation from a measure of gamma radiation resulting from neutron inelastic scatter was first introduced commercially in the 1970s, and is generically known as the “carbon/oxygen” “neutron inelastic scatter” log. FIGS. 4a and 4b illustrate the logging tool 13 embodied as an inelastic scatter type logging system. Attention is first directed to FIGS. 2 and 4a. FIG. 4a is a plot of neutron output N from the source 42 plotted as a function of time. Pulses 70 of 14 MeV neutrons from the source 42 induce inelastic scatter reactions within the formation 22 penetrated by the borehole 20. FIG. 4b illustrates total gamma radiation flux for the source neutron output N of FIG. 4a. Compared with the thermal neutron capture process, the inelastic scatter process is much faster and, in practice, is essentially instantaneous. As a result, measured radiation is very intense during each neutron burst spanning the time interval t0 to t1 as illustrated in FIG. 4b. This radiation is primarily generated by inelastic scatter reactions. Because of the essentially instantaneous speed of the inelastic scatter reactions, the YAP detector must be operated during the neutron pulse within a time interval t0 to t1 thereby exposing the YAP to very intense radiation. Pulse repetition rate is typically 10,000 to 20,000 pulses per second since no measurements are made during the quiescent period between pulses 74. The relatively low level of gamma radiation 75 shown between pulses 70 typically comprises thermal capture radiation (capture component typically is larger than shown, relative to gammas during pulse), naturally occurring gamma radiation, and possibly very low levels of activation radiation from within the YAP crystal. Neutron pulse width 72 is also reduced to about 5 μs to allow for the increased pulse repetition rate. Pulse pile-up in a gamma ray detector in intense gamma radiation fields is a significant problem as discussed previously. This is the case when the tool 13 is embodied as an inelastic scatter type tool because of the intense radiation flux in which the detector must operate during a neutron pulse. The use of a YAP scintillation crystal, with its relatively short light decay constant, results in a significantly improved system when compared to prior art systems using a NaI(Tl) crystal with a light decay constant which is an order of magnitude greater. FIG. 5a illustrates enlarged views of three consecutive neutron pulses 70 as shown previously in FIG. 4a. The effects of pulse pile-up, and the minimization of this problem using a YAP scintillation crystal, will be illustrated with the following hypothetical example. Attention is first directed to FIG. 5b. Assume that three gamma rays of equal energy Ei impinge upon a NaI(Tl) detector during a time interval 72 during the first neutron pulse 70 at times 90, 91 and 92. FIG. 5b illustrates as a curve 82 voltage V(Eγ) generated by the light sensing device optically coupled to the NaI(Tl) detector. The value of V(Eγ) shown at 79 represents voltage representative of a gamma ray of energy Ei if no pileup were present. Because of the relatively long light decay constant of NaI(Tl), the corresponding voltage V(E65 ) from the gamma ray impinging at time 90 does not decay to a negligible level before the voltage buildup from the gamma ray impinging at time 91. Voltage V(Eγ) from the gamma ray impinging at time 91 does not decay to a negligible level before the voltage buildup from the gamma ray impinging at time 92. The result is pulse pile-up that produces a cumulative voltage pulse V(Eγ) of magnitude 80, which is clearly greater that the value 79 that would be produced in the absence of pile-up. Next assume that two gamma rays of energy Ei impinge upon the NaI(Tl) detector at times 93 and 94 during the time interval 72′. The time interval between the two gamma rays is less that the time interval between any of the impinging gamma rays from the previous time interval 72. Pile-up is again a significant problem producing a cumulative voltage pulse V(Eγ) of magnitude 80′, which is clearly greater that the value 79 that would be produced in the absence of pile-up. Finally, assume that three gamma rays of energy Ei impinge upon the NaI(Tl) detector at times 95, 96 and 97 during the time interval 72″. The time interval spanned by the three gamma rays is less that the time interval spanned by the three impinging gamma rays from the previous time interval 72. Pile-up is even more significant than the previous two examples, yielding a cumulative voltage pulse V(Eγ) of magnitude 80″ which is clearly greater that the pile-up values 80 and 80′. Attention is now directed to FIG. 5c. Assume that the three gamma rays of equal energy Ei impinge upon a YAP detector during the time interval 72 of the first neutron pulse 70, again at the times 90, 91 and 92. FIG. 5c illustrates as a curve 82′ the voltage V(Eγ) generated by the light sensing device optically coupled to the YAP detector. The value of V(Eγ) shown at 79 again represents voltage representative of a gamma ray of energy Ei if no pileup is present. Because of the relatively short light decay constant of YAP, the corresponding voltage V(Eγ) from the gamma ray impinging at time 90 does decay to a negligible level before the voltage buildup from the gamma ray impinging at time 91. Voltage V(Eγ) from the gamma ray impinging at time 91 does decay to a negligible level before the voltage buildup from the gamma ray impinging at time 92. This results in three well resolved pulses which produce separate voltage pulses V(Eγ) of magnitude 79 corresponding to three gamma rays of Eγ. Stated another way, there is no pulse pile-up. Next consider the two gamma rays of energy Ei impinging upon the YAP detector at times 93 and 94 during the time interval 72′. As stated previously, the time interval between the two gamma rays is less that the time interval between any of the impinging gamma rays from the previous time interval 72. The YAP detector system is still able to properly resolve the two gamma rays and generate the correct voltage pulses V(Eγ) of magnitude 79. Finally, again consider the three gamma rays of energy Ei which impinge upon the YAP detector at times 95, 96 and 97 during the time interval 72″. Although the time interval spanned by the three gamma rays is less that the time interval spanned by the three impinging gamma rays from the previous time interval 72, the YAP detector system is still able to properly resolve the three gamma rays and generate the correct voltage pulses V(Eγ) of magnitude 79. Again, there is no pulse pile-up in the YAP crystal. For the three hypothetical examples, pulse pile-up is eliminated using the YAP detector system. FIG. 6 is a gamma ray energy spectrum consisting of a plot of measured gamma ray intensity Cγ as a function of gamma ray energy Eγ. Curve 102 represents a spectrum from the hypothetical example using the NaI(Tl) detector system illustrated in FIG. 4b. The curve, which was induced by monoenergetic gamma radiation of energy Ei, does not peak sharply at Ei, but is significantly broadened to the high energy side by pulse pile-up. Curve 100 represents a spectrum from the hypothetical example using the YAP detector system illustrated in FIG. 4c. Since no pulse pile-up is present in the YAP detector, the spectrum is peaked sharply at energy Ei. The examples discussed above and illustrated in FIGS. 5a–5c and FIG. 6 clearly illustrate the advantages of a YAP detector system in borehole applications, especially in high intensity gamma ray flux fields. The light responsive means 14 and 34, and the electronic packages 16 and 36 (see FIGS. 1 and 2), are designed to efficiently process the scintillations generated by YAP scintillation crystals. In borehole instrumentation, the light responsive means is typically a photomultiplier tube. The PMT is selected with dynode string to effectively process scintillation output pulses with short light decay constants. Pulses are typically preamplified by circuitry in the cooperating electronics package. Preferably a charge integrating preamplifier is used, wherein the preamplifier outputs electrical pulses with rise and decay times commensurate with the short light constant pulses generated by the YAP scintillator. Proper selection of light responsive means and the use of complementary “fast” pre-amplification circuitry yields a detector assembly which efficiently processes scintillations with short light decay times. This efficient processing minimizes pulse pile-up in the detector assembly. FIG. 7 illustrates a typical gamma ray spectrum measured with the tool 13 configured to detect inelastic scatter radiation. Typically measured counts Cγ are integrated over preselected energy ranges or “windows” to obtain counts needed to determine formation and borehole parameters of interest. As an example, four energy windows W1, W2, W3 and W4 are shown at 112, 114, 116 and 118, respectively. Corresponding integrated counts C1, C2, C3 and C4 are shown at 122, 124, 126 and 128, respectively, as represented by shaded areas. The windows W1, W2, W3 and W4 (and thus corresponding counts C1, C2, C3 and C4) might contain radiation from inelastic scatter of neutrons from oxygen, carbon, calcium and silicon nuclei. These count rates can then be combined to obtain measures of fresh water formation saturation using methods well known in the industry. As mentioned previously, the YAP scintillation crystal posseses many properties which are ideally suited for borehole instrumentation. YAP is rugged and less subject to shock and vibration damage when compared to other commonly used crystals such as NaI(Tl). YAP is not hygroscopic thereby eliminating the need of hermetic packaging required for NaI(Tl) crystals, and thereby increasing design flexibility in borehole instrumentation. YAP is relatively high density (5.55 g/cm3), and is similar in efficiency in the detection of gamma radiation to NaI(Tl) over the integrated energy range of 0.1 to 9.5 MeV. The major constituents of YAP are less susceptible to thermal neutron activation than the major constituents of NaI(Tl). YAP is less susceptible to variation in temperature than NaI(Tl). In addition to measuring gamma radiation from reactions in the formation and borehole, YAP can be used in conjunction with the borehole environs measurement as a neutron source monitoring system. There are other applications and processing procedures of the invention that will become apparent to those of ordinary skill in the art. While the foregoing disclosure is directed toward the preferred embodiments of the invention, the scope of the invention is defined by the claims, which follow.
052609847	claims	1. An X-ray diagnostics installation comprising: An X-ray tube which generates an X-ray beam in a beam path; A primary radiation diaphragm disposed in said beam path and having at least one moveable element which can assume different orientations; and Control means for positioning said moveable element is said beam path including user-manipulable setting means, consisting of an operating lever having a free end with a cap and said operating lever being pivotable in all directions and rotatable by said cap, for operating said control means for causing said moveable element to execute a motion corresponding to motion of the second means for all orientations of said moveable element. 2. An x-ray diagnostics installation as claimed in 1 further comprising means for generating a video image of an examination subject disposed in said x-ray beam, and means, upon actuation of said setting means, for mixing the position of an evaluation dominant into said video image. 3. An x-ray diagnostics installation as claimed in claim 1 wherein said setting means is rotatable for effecting a rotary motion of said movable element. 4. An x-ray diagnostics installation as claimed in claim 1 wherein said setting means is pivotable for effecting a movement of said movable element in a direction corresponding to the direction of the pivot. 5. An x-ray diagnostics installation as claimed in claim 1 further comprising means for displaying a video image of an examination subject disposed in said beam path, and means for displaying said movable element of said primary radiation diaphragm in said video image so that movement of said movable element in said video image coincides with movement of said setting means. 6. An x-ray diagnostics installation as claimed in claim 5 further comprising processing means, connected to said control means, for, upon actuation of said setting means generating a line corresponding to a contour of said movable element mixed in said video image. 7. An x-ray diagnostics installation as claimed in claim 1 further comprising high-voltage means for feeding said x-ray tube, and further comprising means for reducing the dose of said x-ray tube upon actuation of said setting means. 8. An x-ray diagnostics installation as claimed in claim 1 wherein said operating lever is mounted so as to be pressable and pullable. 9. An x-ray diagnostics installation as claimed in claim 8 further comprising an optics system in video chain for generating a visible image of an examination subject disposed in said beam path, said optics system including an iris diaphragm, and wherein said iris diaphragm is connected to said control means so that pressing and pulling of said operating lever respectively opens and closes said iris diaphragm.
046876057	abstract	An automated fuel rod production system includes a radioactive powder fabrication and processing stage, a pellet fabrication stage, a pellet processing stage, a tube preparation stage and a fuel rod fabrication and inspection stage, all of which provide a continuous (paced) mode of operation from the conversion of a radioactive gas to powder, through the fabrication of the powder into pellets, to completion of the assembly of the fuel rods. Extra capacity is designed into the system at critical points in the powder processing and pellet fabrication and processing stages to facilitate the continuous, paced mode of operation.
052260658	abstract	A device for disinfecting medical materials includes a heat source capable of heating the medical materials to approximately 60.degree. C. and exposing the medical materials to a source of gamma irradiation capable of irradiating medical materials with about 0.25 to about 2.0 Mrads.
	claims	1. An apparatus comprising:a pressurized water reactor (PWR) comprising a pressure vessel containing a nuclear reactor core comprising fissile material;a central riser disposed inside the pressure vessel and defining a coolant circulation path in which coolant water heated by the nuclear reactor core flows upward inside the central riser, exits a top opening of the central riser, and flows downward in a downcomer annulus defined between the central riser and the pressure vessel to return to the nuclear reactor core;a radiological containment structure inside of which the PWR is disposed;an emergency core cooling system configured to drain water from a body of water through an injection line into the pressure vessel in response to a vessel penetration break at the top of the pressure vessel that depressurizes the pressure vessel; andan extension of the injection line disposed inside the pressure vessel and passing through the central riser, the extension configured to operate concurrently with the emergency core cooling system to suppress flow of liquid water from the pressure vessel out the vessel penetration break at the top of the pressure vessel. 2. The apparatus of claim 1 wherein the extension of the injection line includes a downwardly oriented outlet spigot disposed inside the central riser. 3. The apparatus of claim 1 wherein the body of water comprises a refueling water storage tank (RWST) disposed with the PWR in the radiological containment. 4. The apparatus of claim 3 wherein the emergency core cooling system further includes:a pressurized water injection tank configured to inject pressurized water into the pressure vessel during depressurization of the pressure vessel;wherein the injection line is configured to drain water from the RWST into the pressure vessel after the depressurization of the pressure vessel. 5. The apparatus of claim 1 wherein the PWR further comprises an integral pressurizer defining a pressurizer volume at the top of the pressure vessel, the integral pressurizer including pressure control elements operable to control pressure in the pressurizer volume. 6. The apparatus of claim 1 further comprising:openings in a lower portion of the central riser arranged to shunt a portion of the upward flow in the central riser into a lower portion of the downcomer annulus. 7. The apparatus of claim 1 wherein:an integral pressurizer defining a pressurizer volume at the top of the pressure vessel and including pressure control elements operable to control pressure in the pressurizer volume; anda surge line configured to provide fluid communication between the pressurizer volume at the top of the pressure vessel and the remainder of the pressure vessel, the surge line configured to direct water outboard toward the downcomer annulus.
	abstract	An object of the present invention is to provide an inspection apparatus for inspecting weld zones in a reactor pressure vessel, the inspection apparatus comprising: an ultrasonic probe 6 for emitting an ultrasonic wave; a probe holding unit 60 for holding the ultrasonic probe 6 such that a ultrasonic wave transmitting surface of the ultrasonic probe 6 is kept in direct contact with or at a constant distance from the outer surface of the reactor pressure vessel 1; a pressing unit 50 for pressing the probe holding unit 60 parallel to a central axis of a control rod drive housing 8 against the reactor pressure vessel; and a rotator 40 for rotating the probe holding unit 60 and the pressing unit 50 about the central axis of the control rod drive housing 8.
046560009	summary	BACKGROUND OF THE INVENTION The present invention relates to a nuclear reactor and, more particularly, to a novel construction of nuclear reactor which can provide greater flow rate of coolant flowing through the reactor core. The construction of a nuclear reactor in accordance with the invention is suitable for use particularly in small-sized nuclear reactors. Most nuclear reactors commercially operating presently are light-water nuclear reactors of large capacities having electric power output of an order of 400 MWE. A boiling water reactor, which is known as a kind of light-water reactor, has a pressure vessel and a reactor core disposed in the pressure vessel. The reactor core includes a multiplicity of fuel assemblies. Control rods for controlling the power of the reactor are adapted to be inserted into the reactor core from the lower side of the reactor core. The boiling water reactor has also a recycling system for recycling a coolant through the reactor core and serving also as means for effecting a fine adjustment of the power of the nuclear reactor. The steam generated in the pressure vessel of the nuclear reactor is introduced into a steam turbine to drive the latter and is then condensed in a condenser. The condensate is then recycled as the coolant into the pressure vessel. Another typical example of a light-water reactor is a pressurized water reactor which is constituted by a pressure vessel containing a reactor core having a multiplicity of fuel assemblies, a steam generator and a primary cooling system which forms a closed loop including the pressure vessel and the steam generator. The hot coolant after being heated in the reactor core is introduced into the steam generator through the pipe of the primary cooling system to make a heat exchange with feed water fed into the steam generator. The coolant, the temperature of which has been lowered as a result of the heat exchange, is returned from the steam generator into the pressure vessel through the pipe of the primary system. On the other hand, the feed water is evaporated to become steam as a result of the heat exchange. The steam is introduced into a turbine to drive the latter and, thereafter, condensed in a condenser. The condensate is returned as the feed water to the steam generator. The capacity of the light-water nuclear reactors is getting larger year by year. On the other hand, however, there is an increasing demand for nuclear reactors of smaller capacities having electric power output of less than 200 MeW, as the power source of small-scale power generating equipment and the heat source for a district heating system. SUMMARY OF THE INVENTION Accordingly, an object of the invention is to provide a nuclear reactor which is improved to provide greater flow rate of coolant flowing through the reactor core. Another object of the invention is to provide a nuclear reactor which permits an easier refueling. Still another object of the invention is to provide a nuclear reactor which can prevent unfavorable vibration of control rods. To these ends, according to the invention, there is provided a nuclear reactor having a reactor vessel, a reactor core disposed in the reactor vessel and including a multiplicity of fuel assemblies, a plurality of control rods adapted to be inserted into the reactor core, and a plurality of control rod driving devices adapted for driving the control rods, characterized in that it comprises a plurality of tubular coolant passage members disposed above the fuel assemblies in the reactor core, the tubular coolant passage members extending upwardly so that the coolant coming out of the fuel assemblies is introduced into the tubular members.
	summary
	summary
044951396	summary	FIELD OF THE INVENTION The present invention relates to a container for the storage and shipment of radioactive waste such as spent nuclear-reactor fuel rods. More particularly this invention concerns such a container which is provided with means for monitoring leakage from its interior. BACKGROUND OF THE INVENTION It is standard practice to ship and store spent nuclear-reactor fuel rods in large metallic containers formed normally of vessels and covers both made of spherulitic cast iron or even steel. Such a container is quite large, having wall thickness of 0.2 m to 0.6 m and an overall height of several meters. The vessel can be made as described in copending patent application Ser. No. 379,890 filed 5/1982 of Friedrich Werner, and may have inclusions of shielding metal such as lead or even lead bars imbedded in its walls. The cover of such a container is formed with a plug that fits within the mouth of the vessel. For best sealing action the vessel mouth and plug are complementarily formed with at least one interfitting shoulder bordered by an annular nonplanar--usually cylindrical or frustoconical--surface. Seals, typically O-rings, are set in the confronting surfaces to form several seal barriers. Typically the material inside is stabilized by concrete, but even so radioactive material is quite active. In fact the vessels are often formed with cooling fins for the figuratively and literally hot contents. In order to monitor whether any of the seals has failed, German patent document No. 2,905,094 filed Feb. 10, 1979 with no priority claim by Henning Baatz proposes a system wherein the vessel is formed with several passages that open between the seals. Such a vessel can be pressurized with a tracer gas, or the chambers themselves can be thus pressurized. In this manner a sniffer connected to the other end of any of these passages can detect the presence or absence of this tracer gas as well as any leaked radioactivity. In addition a pressure reading of each of these chambers can often provide valuable information. To this end the upper rim of the vessel is formed with recesses in which the valves for the other ends of the passages open. Thus this rim must be provided with a safety cover to protect these elements. The provision of this extra cover, normally in addition to the above-described cover and a so-called second safety cover overlying it, represents an noticeable manufacturing expense. In addition the passages in the vessel, which may weigh over a ton empty, must be made in situ, that is they cannot be easily conveyed to a shop. This again adds to costs. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved radioactive-waste container. Another object is the provision of such a radioactive-waste container which overcomes the above-given disadvantages. A further object is to provide an inexpensive such container which is provided with a superior leak monitor. SUMMARY OF THE INVENTION These objects are attained according to the instant invention in a container whose massive metallic vessel, much as in the prior art, has an interior adapted to receive radioactive waste and a mouth formed with inner and outer spaced generally planar and annular vessel shoulders and formed therebetween with a nonplanar intermediate annular vessel surface. A massive metallic cover formed with a plug fits in the mouth and has respective inner and outer plug shoulers closely juxtaposed with the vessel shoulders and a nonplanar intermediate annular plug surface complementary to the intermediate vessel surface. An inner ring seal engages snugly between the inner shoulders. A pair of generally concentric and spaced outer ring seals engage snugly between the outer shoulders and forming an annular outer chamber therebetween. An intermediate ring seal engages snugly between the intermediate surfaces and forms therebetween and with the inner ring seal an annular inner chamber and therebetween and with the outer ring seals an intermediate chamber. The cover is formed with respective inner, intermediate, and outer passages each having one end opening into the respective chamber and another end. Means is provided on the cover at the other ends of the passages for sampling gases therein and in the respective chambers. Thus with the system of this invention the relatively small cover is formed with the passages and is provided with the monitoring means. In fact according to another feature of this invention all the seal rings, which may be of any standard elastic or metallic construction, are received in respective grooves in the cover. The provision of a third chamber on the shoulder at the flange of the cover eliminates the necessity of an additional hermetically tight cover to form an outermost chamber for monitoring leaks. A simple cover serving only to prevent physical damage to the covered structure is all that is needed. All of the passages terminate in respective recesses or pockets formed in the top of the cover and also covered, for safety's sake, by respective bolted-on plates. Obviously these leak monitors are not used a lot; typically they are useful in the event of an accident, such as during transport, when the integrity of the containers might be doubted. According to another feature of this invention the covers are secured by means such as bolts to the vessel at its mouth. Such connection is inexpensive and very strong. The shoulders according to this inventjion are planar and parallel. The intermediate surfaces are surfaces of revolution, normally cylindrical. A body of tracer gas at above-ambient pressure in the vessel makes the system of this invention particularly easy to use to detect leaks. The gas can be in the vessel or in some or all of the chambers, and may be at different pressures in the different chambers so any leakage can be detected. According to this invention the other passage ends are provided with valves of the one-way type, or of the type that only open when connected to an appropriate fitting. Thus leakage at this end of each passage is made impossible.
	claims	1. A method, comprising:providing an x-ray beam from a laser-Compton x-ray source, wherein said x-ray beam is produced by colliding only one laser beam with an electron beam wherein said x-ray beam includes a first beam region having an energy that is greater than the k-shell absorption edge of a test element and wherein said x-ray beam further includes a second beam region having an energy that is less than the k-shell absorption edge of said test element;directing said x-ray beam onto a first location on an object;detecting first energy of said first beam region and second energy of said second beam after portions of each have transmitted through said first location;calculating the difference between said first energy and said second energy pattern; anddisplaying said difference. 2. The method of claim 1, wherein the step of displaying said difference comprises displaying said difference either as data or an image. 3. The method of claim 1, further comprising repeating the steps of claim 1 a plurality of times at different locations. 4. The method of claim 1, further comprising repeating the steps of claim 1 a plurality of times by rastoring the relative locations one to another of said object and said x-ray beam. 5. The method of claim 1, wherein said x-ray beam is apertured between said source and said object such that only said first beam region and said second beam region of said x-ray beam propagate onto said object. 6. The method of claim 5, wherein only one of said first beam region or said second beam region is allowed to propagate onto said location at a time, and then the other of said first beam region or said second beam region is allowed to propagate onto said location. 7. The method of claim 1, further comprising eliminating, with a high Z tube, at least a portion of x-rays that have been scattered by said object from being detected. 8. The method of claim 1, wherein the step of detecting is carried out with an x-ray detector having an inner region for detecting said first energy and an outer region for detecting said second energy. 9. The method of claim 1, wherein the step of detecting is carried out with a 2-D x-ray detector array. 10. The method of claim 9, wherein only pixels of said 2-D detector array that are fully covered by said first energy are used to calculate said first energy and only pixels of said 2-D detector array that are fully covered by said second energy are used to calculate said second energy. 11. The method of claim 1, further comprising passing said x-ray beam through a slit such that one dimension of said first beam region and said second beam region are the same. 12. The method of claim 1, further comprising aperturing said x-ray beam such that there is a distinct area between said first beam region and said second beam region where there are no photons of either region. 13. The method of claim 1, wherein the step of detecting is carried out with an x-ray detector having an area that is small enough so that it can detect only one of said first energy or said second energy at a time, the method further comprising dithering said detector between said first beam region and said second beam region. 14. The method of claim 1, wherein said first region and said second region are aperture to have about the same area. 15. The method of claim 1, wherein the size of said second region is set so that the total number of photons contained in said second beam region equals that of said first region. 16. The method of claim 1, wherein an aperture is placed in the path of said beam prior to said object, wherein said aperture is configured to allow passage of only one of said first beam region or said second beam region, the method further comprising dithering said aperture to allow first one beam region and then the other. 17. An apparatus, comprising:a laser-Compton x-ray source, wherein said x-ray beam is produced by colliding only one laser beam with an electron beam for providing an x-ray beam that includes a first beam region having an energy that is greater than the k-shell absorption edge of a test element and wherein said x-ray beam further includes a second beam region having an energy that is less than the k-shell absorption edge of said test element;a detector configured for detecting first energy of said first beam region and second energy of said second beam after portions of each have transmitted through a first location of an object;a processor configured for calculating the difference between said first energy and said second energy pattern; anda display device configured for displaying said difference. 18. The apparatus of claim 17, further comprising a first aperture located between said source and said object, wherein said aperture is configured to only allow said first beam region and said second beam region to propagate onto said object. 19. The apparatus of claim 18, wherein only one of said first beam region or said second beam region is allowed to propagate onto said location at a time, and then the other of said first beam region or said second beam region is allowed to propagate onto said location. 20. The apparatus of claim 17, further comprising a high Z tube placed between said object and said detector, wherein said high Z tube is configured for eliminating at least a portion of x-rays that have been scattered by said object from being detecting. 21. The apparatus of claim 17, wherein said detector comprises an inner region for detecting said first energy and an outer region for detecting said second energy. 22. The apparatus of claim 17, wherein said detector comprises a 2-D x-ray detector array. 23. The apparatus of claim 17, further comprising a slit aperture positioned between said source and said object, wherein said slit is configured such that one dimension of said first beam region and said second beam region are about the same. 24. The apparatus of claim 17, further comprising an annulus placed within said beam for aperturing said x-ray beam such that there is a distinct area between said first beam region and said second beam region where there are no photons of either region. 25. The apparatus of claim 17, wherein said detector has an area that is small enough so that it can detect only one of said first energy or said second energy at a time, said apparatus further comprising means for dithering said detector between said first energy region and said second energy region. 26. The apparatus of claim 17, further comprising an aperture placed in said beam to perform a function selected from the group consisting of (i) setting said first region and said second region to have about the same area, (ii) setting the size of said second region so that the total number of photons contained in said second beam region equals that of said first region and (iii) allowing passage of only one of said first beam region or said second beam region wherein the apparatus further comprises means for dithering said aperture to allow first one beam region and then the other. 27. A method for 2-color radiography with an x-ray beam produced by a laser-Compton x-ray source, the method comprising:providing an x-ray beam from a laser-Compton x-ray source, wherein said x-ray beam is produced by colliding only one laser beam with an electron beam, wherein said x-ray beam includes a first beam region having an energy that is greater than the k-shell absorption edge of a test element and wherein said x-ray beam further includes a second beam region having an energy that is less than the k-shell absorption edge of said test element;directing said first beam region onto a first location of an object;obtaining a first energy measurement of a portion of any photons from said first beam region that propagate through said object at said first location;directing said second beam region onto said first location;obtaining a second energy measurement of a portion of any photons from said second beam region that propagate through said object at said first location;calculating the difference between said first energy measurement and said second energy measurement; anddisplaying said difference. 28. An apparatus for 2-color radiography with an x-ray beam produced by a laser-Compton x-ray source, the method comprising:a laser-Compton x-ray source, wherein said x-ray beam is produced by colliding only one laser beam with an electron beam for providing an x-ray beam, wherein said x-ray beam includes a first beam region having an energy that is greater than the k-shell absorption edge of a test element and wherein said x-ray beam further includes a second beam region having an energy that is less than the k-shell absorption edge of said test element;a detector configured and positioned for obtaining a first energy measurement and a second energy measurement, wherein said first energy measurement is of a portion of any photons from said first beam region that propagate through an object at a first location on said object and wherein said second energy measurement is of a portion of any photons from said second beam region that propagate through said object at said first location;means for calculating the difference between said first energy measurement and said second energy measurement; andmeans for displaying said difference.
047088443	claims	1. In a nuclear reactor core, a plurality of combined in-core flux detector and thermocouple assemblies, each said assembly comprising: an outer tube which is sealed at its upper end; an inner tube disposed within, and extending along the length of, said outer tube; neutron detector means disposed within said inner tube; means connected to said neutron detector means for displacing said neutron detector means along the length of said inner tube; and a plurality of thermocouples disposed outside of said inner tube and enclosed within said outer tube, said plurality of thermocouples comprising one group of thermocouples which are spaced apart along the length of said outer tube, wherein said group of thermocouples of each said assembly is connected to constitute a back-up coolant level monitoring means, and said assemblies are distributed over a selected region of the reactor core, with the locations of said group of thermocouples along the length of said outer tube being different from one said assembly to another to provide a coolant level monitoring operation having a higher precision than could be achieved by one said assembly alone. 2. An arrangement as defined in claim 1 wherein in each said assembly thermocouples is provided with conductive leads and all of said conductive leads and said means connected to said neutron detector means extend out of said assembly via the lower end of said outer tube. 3. An arrangement as defined in claim 2 wherein in each said assembly outer tube is arranged to extend through the bottom of a reactor pressure vessel into the core of such reactor. 4. An arrangement as defined in claim 1 wherein said group of thermocouples of each said assembly is connected to constitute a back-up coolant level monitoring means. 5. An arrangement as defined in claim 4 wherein said plurality of thermocouples of each said assembly further comprises a first thermocouple connected to monitor the temperature of coolant exiting the reactor core and a second thermocouple connected to monitor that temperature in the event of failure of said first thermocouple. 6. An arrangement as defined in claim 1 wherein said plurality of thermocouples of each said assembly further comprises a first thermocouple connected to monitor the temperature of coolant exiting the reactor core and a second thermocouple connected to monitor that temperature in the event of failure of said first thermocouple. 7. An arrangement as defined in claim 1 in combination with a reactor including a pressure vessel and a core housed within said pressure vessel and containing a plurality of fuel rod assemblies, wherein each said flux detector and thermocouple assembly is located within a respective fuel rod assembly and is connected to the region outside of said pressure vessel via a single passage in the vicinity of the bottom of said pressure vessel.
	summary
055263844	description	DETAILED DESCRIPTION FIGS. 1A and 1B show a fuelling machine 1, resting on the upper edge of the vertical concrete walls 3 of the cavity 2 of a nuclear reactor, in the bottom of which a reactor pit containing the vessel of the reactor opens out. The fuelling machine 1 is used for lifting or fitting fuel assemblies constituting the core of the reactor arranged inside the vessel. The operations of fuelling or refuelling the nuclear reactor, which require use of the fuelling machine 1, are carried out underwater, the cavity being filled with water up to the level 4. The fuelling machine 1 includes a mobile carriage 12, making it possible to displace the fuelling machine in order to take up or deposit a fuel assembly in any location in the core of the reactor inside the vessel. The carriage 12 includes a first carriage 5 mounted movably on rails 6, by means of wheels 7. The rails 6 are themselves fastened on a second carriage 8 mounted movably on rails 9 resting on the upper part of the walls 3 of the cavity 2 and arranged in a direction perpendicular to the direction of the rails 6. The carriage 12 including the first and second carriages constitutes a carriage having crossed movements in two perpendicular directions of the horizontal plane. The first carriage 5 of the assembly 12 constituting the carriage of the fuelling machine carries the external tubular shaft 10 of the fuelling machine, which is of cylindrical shape and has a vertical axis 11. The shaft 10 rests on the carriage 5 via guide means allowing it to be displaced in rotation and to be oriented about the axis 11 on the first carriage 5. An internal mast 13 is mounted, inside the external shaft 10, in a coaxial arrangement and so as to be movable along the direction of the axis 11 of the external shaft, which mast is fixed by means of pulleys to lifting cables 14 of a winch 15. The lower part of mast 13 includes means 16 which make it possible to attach a fuel assembly 17 by means of its top nozzle. The mobile carriage 12 of the fuelling machine makes it possible to displace the assembly consisting of the external shaft 10 and the internal mast 13 in two directions of the horizontal plane in crossed movements. In this way, it is possible to place the mobile mast 13 in line with any position inside the core of the nuclear reactor, in order to take up or deposit any fuel assembly 17. The external shaft 10 includes means, such as 18, for guiding in the axial direction 11 the internal mast 13 which is movable inside the external shaft 10. A guide means 18, which has only been represented schematically in FIG. 1, includes sets of guide rollers 19 spaced along the axial direction of the external shaft 10 and arranged so as to interact with guide parts of the mast 13, as will be explained hereinbelow. The mast 13 can be displaced in the axial direction 11, which corresponds to the vertical direction, during use of the fuelling machine, by virtue of the winch 15, between a completely raised position represented in FIG. 1 and a bottom position in which the attachment device 16 of the mobile mast 13 is at the level of the top nozzles of the fuel assemblies of the core of the nuclear reactor. In this bottom position, it is possible to grip or deposit a fuel assembly 17 of the core of the reactor. In the top position of the mobile mast 13, as represented in FIGS. 1A and 1B, the fuel assembly 17 fastened to the lower end of the mobile mast 13 by means of the attachment device 16 is completely housed within the external shaft 10 which protects the fuel assembly, for example during displacements of the carriage 12 in the horizontal directions. Between its bottom position and its top position, the mobile mast 13 is guided inside the external shaft 10 by the guide elements 18. The alignment of the sets of rollers 19 of the guide elements 18 determines the alignment and the direction of displacement of the mobile mast 13 and of the fuel assembly 17. The alignment of the rollers 19 should therefore be checked and adjusted very precisely. The fuelling machine also includes, inside the external shaft 10, a means 20 for holding the fuel assembly 17 in the transport position and a means 21 making it possible to facilitate engagement of the fuel assembly in order to fit it in the core. The holding device 20 includes an end-stop 22 mounted so as to pivot about a pin 23 at the lower end part of the external shaft 10 and a substantially axial manuevering rod 24 connected at one of its ends to the holding end-stop 22 and, at its other end which is next to the upper part of the external shaft 20, to a manuevering jack. The manuevering jack makes it possible to displace the end-stop 22 between a position for holding the fuel assembly 17, represented in solid lines in FIG. 1, in which the end-stop is engaged in the bottom nozzle 17a of the fuel assembly, and a standby position 22' represented in dashes. The engagement device 21 includes a very long body which has a bent part connected at its upper part to a manuevering rod 26 which is connected to a manuevering jack 25 at the level of the upper part of the external shaft 10. The jack 25 makes it possible to displace the elongate body of the engagement device 21, by means of the manuevering rod 26, between a standby position represented in FIG. 1 and a working position in which the body 21 of the engagement device rests on attachment means which are solidly attached to the exterior surface of the mobile internal mast 13. In this working position, the lower part of the engagement device 21, below the bent part, is arranged adjacent to the lateral surface of the fuel assembly 17. In this position, a lower end-stop 21a makes it possible to guide the bottom nozzle 17a of the fuel assembly 17 at the moment when the fuel assembly 17 is deposited by the mobile mast 13. When the mobile mast 13 to which a fuel assembly 17 is fastened is lowered into the cavity of the reactor and then into the vessel, so that the leg of the fuel assembly comes into proximity with the lower support plate of the core, the end-stop 21a is recentered on the lower core plate and guides the bottom nozzle 17a of the fuel assembly with respect to the lower core plate during its descent. The fuel assembly is thus fitted very reliably. Fitting of the fuel assembly on the support plate of the core in a desired orientation is guaranteed by virtue of the possibility of orienting the external shaft 10, in which the mobile internal mast 13 is mounted, on the carriage 5, about the axis 11. As shown in FIGS. 2 and 3, the guide elements 18 of the mobile internal mast 13 consist of sets of rollers 19 spaced along the length of a beam 28 and carried by supports 29 which are rigidly and solidly attached to the beam 28. Each of the sets of rollers 19 includes two rollers having mutually perpendicular axes which are arranged in a plane perpendicular to the axis 11 common to the external shaft 10 and to the mobile internal mast 13. The straight profiled beam 28, which has a U-shaped cross-section, is slightly shorter than the external shaft 10. Each of the beams 28 is fastened outside the external shaft 10, facing and at a short distance from its external surface, along the direction of the generatrices, i.e. along the axial direction 11 of the external shaft 10. In its part facing the beams 28, the external shaft 10 includes openings 27 spaced along the axial direction of the shaft 10, each of the openings 27 providing passage for a set of rollers 19 and for the support 29 of these radially directed rollers. The openings 27 have a height, in the axial direction of the shaft 10, substantially greater than the dimension of the supports 29 of the sets of rollers 19 in this axial direction. The openings 27 also have a width, in the circumferential direction, substantially greater than the width of the supports 29 and of the sets of rollers 19 in the circumferential direction. In this way, it is easy to mount the guide elements on the external shaft of the fuelling machine, as will be explained hereinbelow. As shown in FIG. 2, the fuelling machine includes two guide elements 18 placed opposite each other, so that these two guide elements have the same axial plane 30 of the shaft 10 and of the mast 13 as plane of symmetry. In particular, the rollers of each of the sets of rollers 19 are arranged symmetrically with respect to the axial plane 30. The mobile internal mast 13, made in tubular form, includes two guide rails 31 fixed on its exterior surface at 180.degree. from one another. The rails 31 each include two straight and plane rolling tracks 31a and 31b which are symmetrical with respect to an axial plane of the mast 13, which interact with the rolling surfaces of the rollers of the sets of rollers 19 in order to guide the mobile internal mast 13 during its displacements in the axial direction 11. The rollers of the sets of rollers 19 and the rolling tracks 31a and 31b of the guide rails 31 of the mobile internal mast 13 are then arranged symmetrically with respect to the axial plane 30. It is thus possible to guide the mobile mast 13 efficiently by using two guide assemblies arranged at 180.degree. to one another about the axis 11 of the external shaft 10. Other arrangements are possible, for example the use of three guide elements arranged at 120.degree. about the axis 11 of the shaft 10, or four elements arranged at 90.degree. about the axis 11. Each of the axially directed guide elements constituted by a beam 18 carries, by means of supports 29, groups of rollers 19 spaced along the axial direction of the external shaft 10. In the case of a machine of the type used in currently employed pressurized water reactors, five sets of two rollers 19 are used, spaced substantially regularly along the axial direction of the external shaft 10. The external shaft 10 carries, on its external surface, in alignment with each of the axially directed beams 28, a lower support foot 32 and an upper support foot 33. The foot 32 is fastened on the exterior surface of the external shaft 10, for example by welding, below the lower opening 27 which allows passage of the lower set of rollers 19 and its support 29. The upper support foot 33 is fastened on the exterior surface of the external shaft 10, for example by welding, above the upper opening 27 which allows passage of the upper set of rollers 19 and its support 29. The beams 28 of the guide elements 18 each include, at one of their ends, a lower fastening panel 34 and, at their opposite end, an upper fastening panel 35. The lower fastening panel 34 of each of the beams 28 carries two positioning studs 36 which can be engaged in openings, of corresponding dimensions, passing through a lower support foot 32 of the external shaft 10. Each of the upper support feet 33 of the external shaft 10 includes two sheaths 37 arranged facing two openings 38 which pass through the upper support panel of the beam 28. Each of the beams 28 is fastened on the exterior surface of the external shaft 10 by engagement of the positioning studs 36, which are solidly attached to the lower support panel 34 of the beam 28, in two openings of a lower positioning foot 32 of the external shaft 10 and by screwing of two externally threaded fastening studs 39 in the tapped bores of two sheaths 37 which are solidly attached to an upper support foot 33 arranged in axial alignment with the lower support foot 32. Screwing the fastening studs 39, by means of a tool engaged on a profiled end part 39a of the stud, makes it possible to engage the lower, blocking part of the fastening stud in an opening 38 of the upper fastening plate 35 of the beam 28. A wall 40, flared upwards in the shape of a funnel, makes it possible to guide the lower part of the beam 28 and engage the positioning studs 36 in the openings of the lower support foot 32 of the external shaft 10. Each of the beams 28 also includes a handling ring 41 in the vicinity of its upper part. As shown in FIG. 2, the fuelling machine also includes a video camera fastened to the lower end of a tubular mast 42 which is mounted so that it can move in the axial direction inside the external shaft 10. The camera fastened to the end of the tubular mast 42 makes it possible to view the operations of gripping and depositing the fuel assemblies 17 in the core of the reactor. The tubular beam 42 for fastening the video camera has independent motorization and guide systems for displacing the video camera during the fuel assembly handling and lifting operations. On the exterior surface of the external shaft 10, three axially directed rails 43 are also fastened, arranged at 120.degree. with respect to one another about the axis 11 of the external shaft 10, and each carrying a floodlight mounted on a carriage, making it possible to illuminate a part of the operating zone of the fuelling machine. The images supplied by the camera suspended from the tubular beam 42 are transmitted to a video screen 44 arranged in the control unit 45 of the fuelling machine, carried by the mobile carriage 12 or installed on the operating deck. At the end of an operation for fuelling or refuelling the core of a nuclear reactor with fuel assemblies, using a fuelling machine according to the invention, the beams 28 of the guide elements 18 are dismounted from the external shaft 10. This dismounting can be carried out very easily, for each of the beams 28, by unscrewing the fastening studs 39 so as to extract the lower engagement parts of these fastening studs from the corresponding openings 38 in the upper fastening panel 35 of the beam 28. The beam 28 is connected via its handling ring 41 to the lifting hook of a hoist which can be moved on a rail fastened under the carriage of the fuelling machine. The hoist makes it possible to lift the beam 28, so as to disengage the positioning studs 36 from the openings in the lower support foot 32 of the external shaft 10. The beam 28 can then be fully disengaged from the external shaft 10 by moving it in a radial direction, so as to extract the sets of rollers 19 carried by the supports 29 from the openings 27. The beam 28 is then taken up by the polar crane of the nuclear reactor and removed from the reactor building. The two beams of the two guide elements of the external shaft which have been removed from the reactor building are successively dismounted before returning the nuclear reactor to operation. The two beams are stored in a horizontal position outside the reactor building, in a room in which it is possible to check and adjust the alignment of the sets of rollers of each of the beams. In the event of damage to one or more of the rollers, they can be replaced easily. The operations of adjusting and repairing the guide elements of the fuelling machine can therefore be carried out under very good conditions for the personnel charged with this task and without having to work inside the building of the reactor. In addition, these operations can be carried out during operation of the nuclear reactor, i.e., without encroaching on the shutdown period of the nuclear reactor during which the fuelling or the refuelling is carried out. The guide elements are therefore available for an operation of fuelling or refuelling a nuclear reactor by using a fuelling machine according to the invention. In particular, on the site of a nuclear power station including a plurality of reactors equipped with fuelling machines of the same type, it is possible to equip any machine with standard guide elements which have been adjusted and/or repaired after a preceding refuelling operation. In order to fit the guide elements on a fuelling machine, before a fuelling or refuelling operation, the guide elements are introduced into the reactor building, and they are then fitted in the vicinity of the external shaft of the fuelling machine using the polar crane of the nuclear reactor. Each of the guide elements is then taken up by the hoist which is located under the carriage of the fuelling machine and can move on a rail in a radial direction. The beam constituting the support of the guide element is placed in a vertical position in the vicinity of the external surface of the external shaft 10 and is then displaced radially by the hoist so that the sets of rollers 19 and their support 29 are introduced into the corresponding openings 27, in a position which is raised with respect to the lower end of the openings 27. The beam 28 is then lowered vertically by using the hoist, so that the positioning studs 36 fastened to its lower part which is guided by the funnel-shaped wall 40, engage in the corresponding openings in the support foot 32 of the external shaft 10. The upper part of the beam 28 is then fastened by screwing the fastening studs 39 into the sheaths 37 of the upper support foot 33 of the external shaft 10, so that the lower engagement part of each of the studs 39 engages in the corresponding opening 38 of the upper fastening panel 35 of the beam 28. Each of the beams constituting the support of each of the guide elements is then mounted in succession. The fuelling machine is then ready to operate, the mobile internal mast being guided perfectly in the vertical direction by the sets of rollers 19. If one of the guide elements proves to be defective during fuelling or refuelling of the nuclear reactor, for example due to an incident, it is possible to dismount it without emptying the cavity of the nuclear reactor and to adjust it on the operating deck of the reactor building or replace it with a new guide element which has been adjusted and checked outside the building of the reactor. The fuelling machine according to the invention can therefore be employed in all cases under very good operating conditions and it can be repaired, after an incident, in a simple and rapid manner. A different type of means for positioning and fastening the support beam of the guide elements on the external shaft of the fuelling machine than those which have been described may be used. More than two guide elements in beam form, each including a number of sets of rollers other than five, may also be used. The fuelling machine according to the invention can be used for carrying out fuelling or refuelling operations of nuclear reactors of widely varied types.
	description	This application is a Divisional of U.S. patent application Ser. No. 11/313,904 filed Dec. 21, 2005. This invention relates generally to nuclear reactors, and more particularly, to an instrument removal system to remove detector cables from their housing. 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 core assembly is contained within the RPV and includes the core support plate, fuel assemblies, control rod blades and a top guide. A core shroud typically surrounds the core assembly 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. A plurality of detectors are utilized to monitor the reactor. Periodically detectors need to be removed for replacement. The detectors are typically positioned in a housing and are attached to cables for transmitting data. A known method of removing detectors includes the use of a bottom entry disposal system which utilizes a pinch wheel system to pull the detector cables from the housing. The detector cables are fed into a cutter for cutting into small two inch pieces for disposal. The detector cable pieces are fed into a disposal cask for transport and removal from the reactor. However, this method has some shortcomings, for example, pinch wheels can slip causing jammed detector cables and/or missed cuts. Also, cutters can jam and generate loose, irradiated chips. Further, disposal casks can fill unevenly which can make cask lids difficult to close. In one embodiment, an instrument removal system for removing detector cables from a nuclear reactor is provided. The instrument removal system includes a removal cart and a disposal cask. The removal cart includes a base including a plurality of wheels coupled thereto, a motor mounted on the base, and a drive shaft operatively coupled to the motor. A disposal spool is removably mounted on the drive shaft, and the disposal spool includes a notch sized to receive the detector cable. A housing is mounted on the base, with the housing enclosing the disposal spool. Also, an entrance port is located in the housing to permit the detector cable to enter the housing. In another aspect, a method of removing detectors from a nuclear reactor using an instrument removal system is provided. the instrument removal system includes a removal cart and a disposal cask. The removal cart includes a base, a plurality of wheels coupled to the base, a motor mounted on the base, a drive shaft operatively coupled to the motor, a disposal spool removably mounted on the drive shaft, a notch in the disposal spool sized to receive the detector cable, a housing mounted on the base that encloses the disposal spool, an entrance port in the housing sized to permit the detector cable to enter the housing. The reactor includes a pressure vessel, an under vessel platform, and a plurality of transfer rails. The method includes positioning the removal cart under the reactor pressure vessel, attaching the detector cable to the disposal spool, winding the detector cable onto the disposal spool, transferring the disposal spool to the disposal cask, and moving the disposal cask from under the reactor pressure vessel. In another aspect, a nuclear reactor is provided. The nuclear reactor includes a reactor pressure vessel, an under vessel platform positioned below the reactor pressure vessel, a plurality of transfer rails positioned below the reactor pressure vessel, at least one detector cable coupled to the reactor pressure vessel, and an instrument removal system operationally positioned on the transfer rails below the reactor pressure vessel. The instrument removal system includes a removal cart and a disposal cask. The removal cart includes a base including a plurality of wheels coupled thereto, a motor mounted on the base, and a drive shaft operatively coupled to the motor. A disposal spool is removably mounted on the drive shaft, and the disposal spool includes a notch sized to receive the detector cable. A housing is mounted on the base, with the housing enclosing the disposal spool. Also, an entrance port is located in the housing to permit the detector cable to enter the housing. An instrument removal system and method of removing detectors from a nuclear reactor is described in detail below. The system includes a removal cart that includes a disposal spool operatively coupled to a motor. A detector cable is coiled around the spool by rotating the spool with the motor, and then the disposal spool is transferred to a disposal cask for removal from the reactor. The removal system does not have a cable cutting process which eliminates loose chips and/or jammed cutters that need be cleared by personnel. The removal system utilizes existing under vessel equipment, for example, under vessel platform and rails, has low complexity with minimal operator interface resulting in lower personnel exposure to radiation. Referring to the drawings, FIG. 1 is a sectional view, with parts cut away, of a boiling water nuclear reactor pressure vessel (RPV) 10. RPV 10 has a generally cylindrical shape and is closed at one end by a bottom head 12 and at its other end by a removable top head 14. A side-wall 16 extends from bottom head 12 to top head 14. Side-wall 16 includes a top flange 18. Top head 14 is attached to top flange 18. A cylindrically shaped core shroud 20 surrounds a reactor core 22. Shroud 20 is supported at one end by a shroud support 24 and includes a removable shroud head 26 at the other end. An annulus 28 is formed between shroud 20 and side-wall 16. A pump deck 30, which has a ring shape, extends between shroud support 24 and RPV side-wall 16. Pump deck 30 includes a plurality of circular openings 32, with each opening housing a jet pump 34. Jet pumps 34 are circumferentially distributed around core shroud 20. An inlet riser pipe 36 is coupled to two jet pumps 34 by a transition assembly 38. Each jet pump 34 includes an inlet mixer 40, a diffuser 42, and a tailpipe assembly 43. Inlet riser 36 and two connected jet pumps 34 form a jet pump assembly 44. Thermal power is generated within core 22, which includes fuel assemblies 46 of fissionable material. Water circulated up through core 22 is at least partially converted to steam. Steam separators 48 separates steam from water, which is recirculated. Residual water is removed from the steam by steam dryers 50. The steam exits RPV 10 through a steam outlet 52 near vessel top head 14. The amount of thermal power generated in core 22 is regulated by inserting and withdrawing control rods 54 of neutron absorbing material, such as for example, boron carbide. To the extent that control rod 54 is inserted into core 22 between fuel assemblies 46, it absorbs neutrons that would otherwise be available to promote the chain reaction which generates thermal power in core 22. Control rod guide tubes 56 maintain the vertical motion of control rods 54 during insertion and withdrawal. Control rod drives 58 effect the insertion and withdrawal of control rods 54. Control rod drives 58 extend through bottom head 12. Fuel assemblies 46 are aligned by a core plate 60 located at the base of core 22. A top guide 62 aligns fuel bundles 46 as they are lowered into core 22. Core plate 60 and top guide 62 are supported by core shroud 20. Pressure vessel 10 is mounted on a reinforced concrete pedestal 66 FIG. 2 is a sectional schematic illustration of an under pressure vessel area 70 of nuclear reactor pressure vessel 10 enclosed by pedestal 66. Under pressure vessel area 70 includes a work platform 72 and transfer rails 74 that can be used for moving work equipment into under vessel area 70. Referring to FIGS. 3-6, an instrument removal system 80 for removing detector cables 82 from nuclear reactor pressure vessel 10 includes, in an exemplary embodiment, a removal cart 84 and a disposal cask 86. Removal cart 84 includes a base 88 with a plurality of wheels 90 operatively coupled to base 88. Wheels 90 permit removal cart to move along transfer rails 74. A motor 92 mounted on base 88, and a drive shaft 94 is operatively coupled to motor 92. Motor 92 can be any suitable motor, for example, an electric motor, an hydraulic driven motor, and an air driven motor. A disposal spool 96 is removably mounted on drive shaft 94. Disposal spool 96 includes a notch 98 sized to receive an end of detector cable 82. Disposal spool 96 also includes a spiral groove 100 to facilitate coiling detector cable 82 around disposal spool 96. A bearing block 102 is mounted on base 88 with drive shaft 94 extending through bearing block 102. At least one air piston 104 (two shown) is mounted in bearing block 102. FIGS. 3 and 4 show air pistons 104 in a first, non-extended position, and FIGS. 5 and 6 show air pistons 104 in an activated extended position. A housing 106 is mounted on base 88 with disposal spool 96, drive shaft 94, bearing block 102, and air pistons 104 positioned inside housing 106. An entrance port 108 is located in housing 106 to permit detector cable 82 to enter housing 106. In the exemplary embodiment entrance port 108 is formed from a transparent tube to permit remote visual monitoring during detector removal. A door 110 is located in one side of housing 106 that permits removal of disposal spool 96 from housing 106 when door 110 is in an open position (shown in FIGS. 5 and 6). Disposal cask 86 includes a main body 114 having a receiving cavity 116 therein. Cavity 116 is sized to receive at least one disposal spool 96. An access door 118 permits access to cavity 116. When door 118 is in an open position, a disposal spool can be transferred into cavity 116. When door 118 is in a closed position, cavity 116 is sealed. A plurality of wheels 120 are operatively coupled to main body 114 to enable disposal cask 86 to move along rails 74 in under vessel area 70. In operation, instrument removal system 80 is first positioned in under pressure vessel area 70. Particularly, removal cart 84 and disposal cask 86 are wheeled into under vessel area 70, and then an end of a detector cable 82 is inserted into notch 98 of disposal spool 96 in removal cart 84. Air motor 92 is activated to coil detector cable 82 onto disposal spool 96. After the entire length of detector cable 82 is coiled onto disposal spool 96, disposal spool 96 is transferred to disposal cask 86 by activating air pistons 104 to push disposal spool 96 off drive shaft 94, out door 106 and into disposal cask 86 through access door 118. Disposal cask 86 is then removed from under vessel area 70. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
	summary
055966128	abstract	A testing arrangement (14) and a method for materials testing at lead-throughs in a cap of a pressurized-water reactor, comprising a flexible sword (85) which at one end is equipped with a probe. Since the lead-throughs consists of a first tube passing the cap and welded to it, and a second tube inserted in the first tube, the weld joint has to be inspected from below via a gap between the tubes. In order to do this by means of a manipulator, a pinching arrangement (32) is arranged, which by pressing the inner tube towards one side widens the gap at the opposite side so that the sword can be inserted.. The pinching arrangement and the sword can then be displaced so that the sword and the widened gap moves around the inner tube, in order that the whole weld and its surrounding area can be inspected.
	summary
	abstract	A radiation area monitor device/method, utilizing: a radiation sensor having a directional radiation sensing capability; a rotation mechanism operable for selectively rotating the radiation sensor such that the directional radiation sensing capability selectively sweeps an area of interest; and a processor operable for analyzing and storing a radiation fingerprint acquired by the radiation sensor as the directional radiation sensing capability selectively sweeps the area of interest. Optionally, the radiation sensor includes a gamma and/or neutron radiation sensor. The device/method selectively operates in: a first supervised mode during which a baseline radiation fingerprint is acquired by the radiation sensor; and a second unsupervised mode during which a subsequent radiation fingerprint is acquired by the radiation sensor, wherein the subsequent radiation fingerprint is compared to the baseline radiation fingerprint and, if a predetermined difference threshold is exceeded, an alert is issued.
	description	The present invention relates to a stimulable cerium activated lutetium borate phosphor capable of giving a stimulated emission off, a radiation image storage panel comprising that phosphor, and a radiation image recording and reproducing method. When exposed to a radiation such as X-rays, an energy-storing phosphor (e.g., stimulable phosphor, which gives off stimulated emission) absorbs and stores a portion of the radiation energy. The phosphor then emits a stimulated emission according to the level of the stored energy when exposed to electromagnetic wave such as visible or infrared light (i.e., stimulating light). A radiation image recording and reproducing method utilizing the energy-storing phosphor has been widely employed in practice. In the method, a radiation image storage panel which is a sheet comprising the energy-storing phosphor is used. The method comprises the steps of: exposing the storage panel to a radiation having passed through an object or having radiated from an object, so that a radiation image information of the object is temporarily recorded in the storage panel; sequentially scanning the storage panel with a stimulating light such as a laser beam to emit a stimulated light; and photoelectrically detecting the emitted light to obtain electric image signals. The storage panel thus processed is subjected to a step for erasing radiation energy remaining therein, and then stored for the use in the next recording and reproducing procedure. Thus, the radiation image storage panel can be repeatedly used. The radiation image storage panel (often referred to as energy-storing phosphor sheet) has a basic structure comprising a support and an energy-storing phosphor layer provided thereon. However, if the phosphor layer is self-supporting, the support may be omitted. Further, a protective layer is generally provided on the free surface (surface not facing the support) of the phosphor layer to keep the phosphor layer from chemical deterioration or physical damage. Various kinds of energy-storing phosphor layer are known and used. For example, a phosphor layer comprising a binder and an energy-storing phosphor dispersed therein is used, and a phosphor layer comprising agglomerate of an energy-storing phosphor without binder is also known. The latter can be formed by a gas phase-accumulation method or by a firing method. The radiation image recording and reproducing method (or radiation image forming method) has various advantages as described above. However, it is still desired that the radiation image storage panel used in the method have as high sensitivity as possible and give a reproduced radiation image of high quality (in regard to sharpness and graininess). It is known that rare earth activated rare earth borate compounds give instant emission off in the ultraviolet or visible wavelength region. For example, L. Zhang et al., “Radiation Effects & Defects in Solids”, vol. 150, pp. 47 to 52 describes that a cerium or praseodymium activated lutetium orthoborate (LuBO3:Ce3+, LuBO3:Pr3+) shows scintillation, namely, gives off instant emission in the ultraviolet or visible wavelength region when excited with UV light or X-rays. Japanese Patent Provisional Publication Nos. 11-271453, 2001-187884 and 2003-248282 propose utilization of rare earth activated rare earth borates (e.g., GdBO3:Eu, YBO3:Eu) as scintillators or as phosphors for lamps or plasma display panels. For preparing the rare earth activated rare earth borate, a hydrothermal process is known. For example, Japanese Patent Provisional Publication No. 2001-187884 discloses a process comprising the steps of: preparing an aqueous solution of Y2(OH)3, EU2(OH)3 and H2BO3, adding a basic aqueous solution (e.g., aqueous ammonia) to the former aqueous solution to prepare hydrates; and causing hydrothermal reaction of the hydrates at a predetermined temperature and a predetermined pressure. In the process, it is necessary to make the hydrates gel in the hydration step. Xiao-Cheng Jiang et al., “Journal of Solid State Chemistry”, vol. 175 (2003), pp. 245 to 251 describes another process which comprises the steps of: dissolving Y2O3, Eu2O3 and H2BO3 in nitric acid, adjusting the pH value of the solution, adding urea to the solution, and subjecting the solution to hydrothermal processing. In the process, an excess of urea often forms undesirable compounds such as Y(OH)CO3 and Eu(OH)CO3. Further, products given by the process are in the form of polydispersive particles. Yuhua Wang et al., “Chemistry Letters”, vol. 30 (2001), No. 3, pp. 206 to 207 describes a process which comprises the steps of: dissolving Gd2O3, Eu2O3 and B2O3 in nitric acid, evaporating the solution to dryness, and treating the residue hydrothermally. It is an object of the present invention to provide a new stimulable phosphor suitable for the radiation image forming method utilizing the energy-storing phosphor. It is another object of the invention to provide a radiation image storage panel comprising the stimulable phosphor. It is still another object of the invention to provide a radiation image recording and reproducing method utilizing the radiation image storage panel comprising the stimulable phosphor. The applicant has studied energy-storing phosphors usable for the radiation image forming method, and found that a cerium activated lutetium borate having been exposed to X-rays or UV rays gives visible stimulated emission off when it is excited with a visible light. The present invention resides in a radiation image storage panel having a phosphor layer which comprises a stimulable cerium activated lutetium borate phosphor represented by the following formula (I):(Lux,Lny)BO3:aCe,bA (I)in which Ln is at least one rare earth element selected from the group consisting of Y, La and Gd; A is at least one element selected from the group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Zr; and x, y, a and b are numbers satisfying the conditions of 0.5≦x<1, 0≦y<0.5, 0<a≦0.2, 0≦b≦0.2 and x+y+a+b=1.0. The invention also resides a method for producing a stimulated emission which comprises the steps of: applying a radiation to a stimulable cerium activated lutetium borate phosphor of the formula (I), whereby storing an energy of the radiation in the phosphor and stimulating the phosphor in which the energy of the radiation is stored with a stimulating light, whereby giving a stimulated emission off. The invention further resides in a radiation image recording and reproducing method comprising the steps of: exposing the radiation image storage panel of the invention to a radiation having passed through an object or having radiated from an object, whereby a spatial energy distribution of the radiation is recorded as a latent image in the phosphor layer of the storage panel; irradiating the storage panel with a stimulating light to emit a stimulated light from the latent image in the phosphor layer; photoelectrically detecting and converting the stimulated light to image signals; and forming a radiation image from the image signals. The cerium activated lutetium borate phosphor of the invention is a novel stimulable phosphor, and is favorably employable for the radiation image forming method. The radiation image storage panel of the invention, which comprises the phosphor of the invention, and the radiation image recording and reproducing method of the invention can be favorably used for medical radiation image diagnosis. In the above formula (I), A is preferably Sm and/or Zr. The number represented by b preferably is 0. The number represented by y preferably is 0. The radiation image storage panel of the invention preferably comprises a support, an energy-storing phosphor layer and a protective layer in order. The stimulable cerium activated lutetium borate phosphor of the invention used for a radiation image forming method is described below in detail. The stimulable cerium activated lutetium borate phosphor of the invention can be preferably prepared by the following first method, in which acetates are used as the starting materials, or otherwise by the second method described later, in which an amide compound is incorporated in a solution of material mixture to coexist with the materials. (1) First Method for Preparation [Step of Preparing Starting Solution] As the starting materials, lutetium acetate [Lu(CH3COO)3.4H2O], cerium acetate [Ce(CH3COO)3.H2O], a boron compound, and if desired, a rare earth acetate [Ln(CH3COO)3.mH2O in which Ln is Y, La and/or Gd, and m is a number of 0 to 4] and other acetates [A(CH3COO)p.nH2O in which A is Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and/or Zr, p is a number of 2 to 4, and n is a number of 0 to 4] are used. Since the co-activator A is in a small amount, nitrate, oxide or nitrate oxide thereof can be used in place of the acetate. Examples of the boron compounds include boric acid [H3BO3], tetraammonium borate [(NH4)2B4O7] and boron oxide [B2O3]. Boric acid is preferred. The starting materials are weighed so that the molar ratio of B/(Lu+Ln+Ce+A) would be in the range of 0.95 to. 2.00, preferably 1.00 to 1.50, more preferably 1.02 to 1.25 and so that relative amounts of Lu, Ln, Ce and A would be in the stoichiometrical ratio. The weighed materials are dissolved in an aqueous medium to prepare an aqueous solution. Examples of the aqueous medium include water, deionized water, pure water, and mixtures thereof with a small amount of nonaqueous solvents (e.g., methanol, ethanol). To the aqueous solution, compounds (e.g., acetates, nitrates) of Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Mn, Al, Ga, In, Tl, Si, Ge, Sn and/or Bi can be added in small amounts. The aqueous solution mixture can have a desired pH value, but it is necessary to adjust the pH value so as not to deposit undesired precipitates such as hydroxides. The pH values at which rare earth elements form the hydroxides to precipitate are different. If even one rare earth element forms the hydroxide in synthesizing the phosphor precursor, a homogeneous rare earth borate cannot be obtained. The pH value of the material solution generally is 9.0 or less, preferably 6.0 or less, more preferably 5.0 or less. [Step of Hydrothermal Treatment] The prepared solution is then subjected to a hydrothermal treatment. In the hydrothermal treatment, the solution is processed at a high temperature and a high pressure for a predetermined period of time. Since reactivity, dissociation and precipitation in the solution are enhanced at a high temperature and a high pressure, the desired compound can be easily synthesized and its crystals can be grown well. The treatment comprises the procedures of: placing the solution in a corrosion-resistant and heat-resistant high-pressure reactor such as a stainless steel-made autoclave, and heating the solution in, for example, an electric furnace. The treatment is generally carried out at a temperature of 100° C. to 500° C. If the temperature is below 100° C., the yield of the product is very low. If above 500° C., the size of the reactor is restricted. The treatment temperature preferably is in the range of 120° C. to 300° C., more preferably in the range of 140° C. to 260° C. If the temperature is kept in this range, a fluorocarbon resin made or fluorocarbon resin-coated reactor can be used. The pressure generally is in the range of 0.1 to 50 MPa. The period of time generally is in the range of 0.1 to 100 hours, preferably in the range of 1 to 24 hours. The reaction mixture produced after the hydrothermal treatment is filtered to collect the precipitated product, which is then washed with alcohol such as ethanol and dried to obtain a powdery cerium activated lutetium borate phosphor (crystalline particles in a single phase). [Firing Step] The obtained powdery phosphor can be fired, if desired, to improve the emission properties. The firing step can be performed by the procedures of placing the powdery phosphor in a heat-resistant container such as alumina crucible and then heating the powdery phosphor in an electric furnace. The firing conditions such as temperature, pattern of temperature control, period of time and atmosphere can be optionally chosen. The fired product can be further subjected to various known procedures such as pulverization and sieving, which are generally performed for preparing conventional phosphors. Thus, the desired stimulable cerium activated lutetium borate phosphor represented by the following formula (I) can be prepared.(Lux,Lny)BO3:aCe,bA (I)In the formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La and Gd; A is at least one element selected from the group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Zr; and x, y, a and b are numbers satisfying the conditions of 0.5≦x<1, 0≦y<0.5, 0<a≦0.2, 0≦b≦0.2 and x+y+a+b=1.0. In consideration of stimulated emission properties, the co-activator A in the formula (I) preferably is Sm and/or Zr. Otherwise, the phosphor is preferably activated by Ce only (namely, b is preferably 0). Further, the rare earth element represented by Ln preferably is not contained (namely, y is preferably 0). As additive components or activating components, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Hf, Nb, Ta, Mn, Al, Ga, In, Tl, Si, Ge, Sn and/or Bi can be incorporated in an amount of 0.4 mol or less based on one mol of B. The crystal structure of the obtained powdery stimulable phosphor can be assigned by X-ray diffraction. The shape and size of the phosphor particles can be determined by means of an electron microscope and a diffractive particle size analyzer. The powdery phosphor of the invention generally comprises monodispersive particles since the crystals grow in the hydrothermal treatment. The phosphor particles can be in the form of sphere, tabular, cube or other shapes, but preferably are in the spherical shape. The mean size of the phosphor particles generally is in the range of 0.01 to 30 μm, preferably in the range of 0.1 to 20 μm, more preferably in the range of 0.2 to 10 μm. The powdery phosphor comprising spherical particles of a small mean size can be thus prepared by the hydrothermal treatment. FIG. 1 is a scanning electron micrograph (×5.000) of powdery Lu0.99875BO3:0.001Ce, 0.00025Sm, which is an example of the stimulable phosphor according to the invention. The powdery phosphor consists essentially of monodispersive spherical particles. The powder pattern of X-ray diffraction indicates that the powdery phosphor consists essentially of crystalline particles of vaterite type in a single phase. FIG. 2 shows time-dependence of stimulated emission intensity (peak wavelength: approx. 400 nm) given off from the powdery phosphor of FIG. 1 when the phosphor having been exposed to X-rays is excited with a semiconductor laser beam (wavelength: 633 nm). FIG. 3 is a spectrum of stimulated emission given off from the powdery phosphor of FIG. 1. (2) Second Method for Preparation [Step of Preparing Starting Solution] As the starting materials, a lutetium (Lu) compound, a cerium (Ce) compound, a boron (B) compound and an amide compound are used. Further, if desired, other rare earth (Ln, A) compounds and a zirconium (Zr) compound can be used. Examples of the rare earth and zirconium compounds include nitrates, halides (chlorides, bromides, iodides), oxides and hydroxides. Acetates can be used. Examples of the boron (B) compounds are the same as those described above. Examples of the amide compounds include lower amides such as formamide and acetamide. The starting materials are weighed so that the molar ratio of B/(Lu+Ln+Ce+A) would be in the range of 0.95 to 2.00, preferably 1.00 to 1.50, more preferably 1.02 to 1.25. The weighed materials are dissolved in an aqueous medium to prepare an aqueous solution. To the aqueous solution of material mixture, compounds (e.g., acetates, nitrates) of Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Mn, Al, Ga, In, Tl, Si, Ge, Sn and/or Bi can be added in small amounts. The aqueous solution can have a desired pH value, but it is necessary to adjust the pH value so as not to deposit undesired precipitates such as hydroxides. The pH value of the starting solution generally is 9.0 or less, preferably 6.0 or less, more preferably 5.0 or less. If some rare earth compounds are used in the starting materials, the desired reaction product is not always precipitated in the below-described hydrothermal treatment. However, the amide compound coexisting in the starting solution enables the product to precipitate well and increases the yield of the product. [Step of Hydrothermal Treatment] As described above, the starting solution containing the amide compound is then subjected to a hydrothermal treatment. The resultant reaction mixture of the hydrothermal treatment is filtered to collect the precipitated product, which is then washed with alcohol such as ethanol and dried to obtain a powdery cerium activated lutetium borate phosphor (crystalline particles in a single phase). [Firing Step] The obtained powdery phosphor can be fired, if desired to improve the emission properties. The fired product can be further subjected to various known treatments such as pulverization and sieving. Thus, the desired stimulable cerium activated lutetium borate phosphor represented by the aforementioned formula (I) can be prepared. The stimulable phosphor of the invention can be easily prepared by the first or second method, in which it is unnecessary to make the hydrates gel or to evaporate the solution to dryness and in which no by-product is produced. Particularly in the first method, a precursor such as hydrate or carbonate is not produced and hence the phosphor can be easily prepared without any by-product derived from the precursor. The above-mentioned preparation methods, however, by no means restrict the invention, and the stimulable phosphor of the invention can be prepared various known methods. The radiation image storage panel of the invention is described below. The radiation image storage panel of the invention comprises an energy-storing phosphor layer containing a stimulable cerium activated lutetium borate phosphor of the formula (I). The phosphor layer generally comprises a binder and the energy-storing phosphor in the form of particles dispersed therein, but further can contain other energy-storing phosphor particles and additives such as colorant. In the following description, the process for preparation of the radiation image storage panel of the invention is explained in detail, by way of example, in the case where the phosphor layer comprises a binder and energy-storing phosphor particles dispersed therein. The support generally is a soft resin sheet or film having a thickness of 50 μm to 1 mm. Examples of the resin material employable for the support include polyethylene terephthalate, polyethylene naphthalate, aramide resin and polyimide resin. The support can be transparent, can contain a light-reflecting material (e.g., particles of alumina, titanium dioxide and barium sulfate) or voids for reflecting the stimulating light or the emission, or can contain a light-absorbing material (carbon black) for absorbing the stimulating light or the emission. The support can be a sheet of metal, ceramics or glass, if desired. For improving the sensitivity or the image quality (e.g., sharpness and graininess), a light-reflecting layer containing a light-reflecting material such as titanium dioxide or a light-absorbing layer containing a light-absorbing material such as carbon black can be formed on the support surface on the side where the phosphor layer is provided. On the opposite side of the support surface, a light-shielding layer containing carbon black can be provided. For improving the image quality, fine concaves and convexes may be formed on the phosphor layer-side surface of the support (or on the phosphor layer-side surface of an auxiliary layer such as an undercoating layer (or adhesive layer), a light-reflecting layer or a light-absorbing layer, if they are provided). On the support (or on the auxiliary layer), the phosphor layer containing the energy-storing phosphor is provided. For forming the phosphor layer, the energy-storing phosphor particles and a binder are dispersed or dissolved in an appropriate organic solvent to prepare a coating solution. The ratio between the binder and the phosphor in the solution generally is in the range of 1:1 to 1:100 (by weight), preferably 1:8 to 1:40 (by weight). Examples of the binders dispersing and supporting the phosphor particles include natural polymers such as proteins (e.g., gelatin), polysaccharides (e.g., dextran) and gum arabic; and synthetic polymers such as polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer, polyalkyl(meth)acrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, and thermoplastic elastomers. These may be crosslinked with a crosslinking agent. Examples of the solvents employable for the preparation of the coating solution for the phosphor layer include lower aliphatic alcohols such as methanol, ethanol, n-propanol and n-butanol; chlorinated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters of lower aliphatic alcohols with lower aliphatic acids such as methyl acetate, ethyl acetate and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether and tetrahydrofuran; and mixtures thereof. The coating solution can contain various additives such as a dispersing aid, a plasticizer for enhancing the bonding between the binder and the phosphor particles, an anti-yellowing agent for preventing the layer from undesirable coloring, a hardening agent, and a crosslinking agent. The prepared coating solution is then evenly spread to coat a surface of the support by a known means such as a doctor blade, a roll coater or a knife coater, and dried to form the energy-storing phosphor layer. The thickness of the phosphor-layer is determined according to various conditions such as characteristics of the desired storage panel, and the mixing ratio between the binder and the phosphor, but generally is in the range of 20 μm to 1 mm, preferably in the range of 50 to 500 μm. It is not necessary to form the energy-storing phosphor layer directly on the support. For example, the phosphor layer beforehand formed on another substrate (temporary support) can be peeled off and then fixed onto the support with an adhesive or by pressing with heating. The energy-storing phosphor layer does not always consist of a single layer, and can consist of two or more sub-layers. In that case, it is possible to change desirably the phosphor, sizes of the phosphor particles and the mixing ratio of binder and phosphor in each sub-layer. The emission properties of the energy-storing phosphor layer can be thus controlled. On the energy-storing phosphor layer, a protective layer is preferably provided to ensure good handling of the storage panel in transportation and to avoid deterioration. The protective layer is preferably transparent so as not to prevent the stimulating light from coming in or not to prevent the emission from coming out. Further, for protecting the storage panel from chemical deterioration and physical damage, the protective layer preferably is chemically stable, physically strong and of high moisture proof. The protective layer can be provided by coating the phosphor layer with a solution in which a transparent organic polymer (e.g., cellulose derivatives, polymethyl methacrylate, fluororesins soluble in organic solvents) is dissolved in an appropriate solvent, by placing a beforehand prepared sheet as the protective layer (e.g., a film of glass or organic polymer such as polyethylene terephthalate) on the phosphor layer with an adhesive, or by depositing vapor of inorganic compounds on the phosphor layer. Various additives may be contained in the protective layer. Examples of the additives include light-scattering fine particles (e.g., particles of magnesium oxide, zinc oxide, titanium dioxide and alumina), a slipping agent (e.g., powders of perfluoroolefin resin and silicone resin) and a crosslinking agent (e.g., polyisocyanate). The thickness of the protective layer generally is in the range of about 0.1 to 20 μm if the layer is made of polymer material or in the range of about 100 to 1,000 μm if the layer is made of inorganic material such as glass. For enhancing the resistance to stain, a fluororesin layer may be further provided on the protective layer. The fluororesin layer can be formed by coating the surface of the protective layer with a solution in which a fluororesin is dissolved (or dispersed) in an organic solvent, and drying the applied solution. The fluororesin may be used singly, but a mixture of the fluororesin and a film-forming resin generally is employed. In the mixture, an oligomer having polysiloxane structure or perfluoroalkyl group can be further added. In the fluororesin layer, fine particle filler may be incorporated to reduce blotches caused by interference and to improve the quality of the resultant radiation image. The thickness of the fluororesin layer is generally in the range of 0.5 to 20 μm. For forming the fluororesin layer, additives such as a crosslinking agent, a film-hardening agent and an anti-yellowing agent can be used. In particular, the crosslinking agent is advantageously employed to improve durability of the fluororesin layer. Thus, a radiation image storage panel of the invention can be produced. The storage panel of the invention can be in known various structures. For example, in order to improve the sharpness of the resultant image, at least one of the layers or sub-layers may be colored with a colorant which does not absorb the stimulated emission but the stimulating light. Further, another phosphor layer comprising a phosphor which absorbs radiation and spontaneously emits ultraviolet or visible light (namely, a layer of radiation-absorbing phosphor) can be provided. Examples of the phosphors include phosphors of LnTaO4:(Nb, Gd) type, Ln2SiO5:Ce type and LnOX:Tm type (Ln is a rare earth element); CsX (X: halogen); Gd2O2S:Tb; Gd2O2S:Pr,Ce; ZnWO4; LuAlO3:Ce; Gd3Ga5O12:Cr,Ce; and HfO2. The radiation image recording and reproducing method of the invention is described below by referring to the attached drawings. FIG. 4 is a sectional view schematically illustrating an radiation image information-reading apparatus of single-side type adopting a point detection system. FIG. 5 is a sectional view schematically illustrating an example of the radiation image storage panel of the invention. The storage panel 10 comprises a light-shielding layer 11, a support 12, an undercoating layer 13, an energy-storing phosphor layer 14, an adhesive layer 15, and a protective layer 16. First, radiation image information (information of spatial distribution of radiation energy) is recorded on the radiation image storage panel 10 (recording procedure). This procedure is carried out, for example, by means of a radiation recording apparatus (not shown in the drawings). A sample is placed between the storage panel 10 and a radiation source, and then exposed to a radiation emitted from the source. Examples of the radiations include neutron beams and ionization radiations such as X-ray, γ-ray, α-ray, β-ray, electron beam and ultraviolet light. In accordance with characteristics of the sample and/or the radiation, the radiation passes through the object or is diffracted or scattered by the object. Since the radiation incident to the protective layer 16-side surface of the storage panel 10 is thus affected by the sample, the spatial energy distribution thereof gives image information of the sample. A portion of the irradiated radiation is absorbed and the energy thereof is stored in the phosphor layer 14, and consequently information on the spatial energy distribution is recorded in the energy-storing phosphor layer 14 in the form of a latent image of the sample. In the case where the sample itself emits radiation (e.g., in the case of autoradiography), the radiation source may be omitted. Next, the information on the spatial energy distribution recorded in the storage panel 10 is read out by means of the apparatus shown in FIG. 4. The storage panel 10 is installed in the apparatus so that the protective layer 16 would be on the reading side (upside). In FIG. 4, the storage panel 10 is conveyed with two pairs of nip rollers 21 and 22 in the direction indicated by the arrow. The stimulating light 23 such as a laser beam is applied onto the protective layer-side (phosphor layer-side) surface of the storage panel 10. From the area having been exposed to the stimulating light 23, the phosphor layer gives off stimulated emission 24 according to the level of the stored energy (namely, according to the spatial energy distribution recorded in the form of a latent image of the sample). The stimulated emission 24 is partly reflected by the mirror 29 and collected with the condenser guide 25 placed above. Another portion of the stimulated emission 24 directly comes into the condenser guide 25. Thus condensed emission is converted into electric signals by means of the photo-electric converter (photomultiplier tube) 26 provided on the base of the condenser guide 25. The electric signals are amplified in the amplifier 27, and then transmitted to the signal processor 28. In the signal processor 28, the signals coming from the amplifier 27 are processed according to the basis of operations (such as addition and subtraction). Thus processed signals are output as image signals. From the image signals, a visible image is reproduced in an image reproduction apparatus (not shown in the drawings). In this way, the radiation image of the sample is reconstituted on the basis of the spatial energy distribution of radiation. The image reproduction apparatus can be a displaying device such as a CRT display, a light-scanning recorder with photosensitive film, or a thermal recorder with heat-sensitive film. Otherwise, the image signals can be temporarily recorded in an image file stored in an optical disc or a magnetic disc. Successively after the above reading-out procedure, the storage panel 10 is conveyed with nip rollers 21 and 22 in the direction indicated by the arrow to an area for erasing. In the area for erasing (not shown in the drawings), the storage panel 10 is exposed to erasing light emitted from a light source such as a sodium lamp, a fluorescent lamp or an infrared lamp, or otherwise an electric field generated by; an electric power supply is applied to the panel, and thereby radiation energy remaining in the storage panel is removed so that the remaining latent image may not give undesirable effects to the next recording procedure. The radiation can be applied to the support-side (light-shielding layer-side) surface of the storage panel. If the storage panel has a structure different from that shown in FIG. 5 (for instance, if the storage panel comprises neither a light-shielding layer nor a light-reflecting layer but comprises a transparent support), the stimulated emission can be collected on the support side or on both sides. For example, another condenser guide 25 and another photo-electric converter 26 are provided below the storage panel 10 in FIG. 4, and the stimulated emission 24 is collected not only on the side having been exposed to the stimulating light 23 but also on the opposite side (double-side reading system). In the reading-out procedure, a line detection system can be adopted. In that case, the procedure is carried out, for example, in the following manner. While the storage panel or a linear stimulating light source (e.g., LD array, LED array, fluorescent light guide) is being moved parallel to the plane of the panel, a linear stimulating light is applied to the storage panel so that it may cross the moving direction almost perpendicularly. The stimulated emission given off from the latent image area having been exposed to the stimulating light is then sequentially and linearly detected with a line sensor, which is, for example, an array of many solid photo-electric converters. Thus, the information on the spatial distribution of radiation energy can be obtained in the form of electric signals giving a visible radiation image. The radiation recording apparatus and the radiation image information-reading apparatus described above can be combined to give a single apparatus, whereby the procedures for recording and reading-out can be continuously performed. Stimulable Lu0.99875BO3:0.001Ce, 0.00025Sm phosphor In a polytetrafluoroethylene(PTFE) container, 2.542 g of Lu(CH3COO)3.4H2O, 0.0020 g of Ce(CH3COO)3.H2O, 0.00060 g of Sm(CH3COO)3.4H2O and 0.408 g of H3BO3 were mixed and dissolved in water to prepare 30 mL of an aqueous solution (pH: approx. 3.8). There was produced no-precipitate in the aqueous solution. The container filled with the aqueous solution was then placed in a stainless steel autoclave, and the autoclave is closed. The closed autoclave was set in an electric oven equipped with a thermostat, and heated at 200° C. for 10 hours to perform hydrothermal treatment. The reaction liquid was filtered to collect the precipitated product, which was then washed with 200 ml of ethanol and dried at 80° C. to obtain a powder. The obtained powder was analyzed by means of an X-ray powder diffractometer on the following conditions, and thereby it was confirmed that the powdery product was crystalline Lu0.99875BO3:0.001Ce, 0.00025Sm compound of vaterite type in a single phase. X-ray tube:CuTube voltage:40 kVTube current:40 mASampling width:0.020°Scanning speed:3.000°/minuteDivergence slit:1°Scattering slit:1°Receiving slit:0.3 mmReceiving slit for monochromatic light:0.6 mm FIG. 1 is a scanning electron micrograph (×5.000) of the prepared Lu0.99875BO3:0.001Ce, 0.00025Sm powder. The phosphor powder consisted essentially of monodispersive spherical particles. The powder was placed in an alumina crucible, and carbon powder was spread around the crucible. The crucible was then placed in an electric furnace, and fired in the atmospheric conditions at 1,000° C. for 1 hour and then at 1,200° C. for 2 hours. The fired powder in the amount of 71 mg was evenly packed in a black cylindrical holder (diameter of concave: 10 mm, depth: 250 μm), and exposed to X-rays (40 kV, 30 mA) for 10 seconds in a darkroom. The powder was then exposed to a semiconductor laser beam (wavelength: 633 nm) 12 seconds after the exposure to X-rays. During the exposure of laser beam, stimulated emission (peak wavelength: approx. 400 nm) given off from the powder surface was detected through an optical filter (B-410, from HOYA Corporation) by a photomultiplier tube (R-1849, from HAMAMATSU Photonics K.K.). FIG. 2 shows how the stimulated emission intensity of the powdery Lu0.99875BO3:0.001Ce, 0.00025Sm varied according to the laser exposing period of time (elapsed time from beginning of the exposure). FIG. 2 clearly indicates that the powder was a stimulable phosphor, which gave off stimulated emission when secondarily excited with a laser beam (633 nm) after primary excitation with X-rays. Stimulable Lu099725BO3:0.0025Ce, 0.00025Zr phosphor The procedure of Example 1 was repeated except that 2.538 g of Lu(CH3COO)3.4H2O, 0.005 g of Ce(CH3COO)3.H2O, 0.0004 g of ZrO(NO3)2.2H2O and 0.408 g of H3BO3 was used as the starting materials, to prepare the stimulable phosphor of the invention represented by the titled formula in the form of powder. There was no precipitate in the aqueous solution. The solution was then subjected to the hydrothermal treatment, and the obtained powder was analyzed by means of an X-ray diffractometer. It was confirmed that the product was crystalline Lu0.99725BO3:0.0025Ce, 0.00025Zr compound of vaterite type in a single phase. After the product was fired, the stimulated emission properties of the obtained powder was measured. The same graph as FIG. 2 was obtained. Stimulable Lu0.995BO3:0.005Ce Phosphor The procedure of Example 1 was repeated except that 2.585 g of Lu(NO3)3.4H2O, 0.013 g of Ce(NO3)3.6H2O, 0.408 g of H3BO3 and 1.351 g of formamide were used as the starting materials, to prepare the stimulable phosphor of the invention represented by the titled formula in the form of powder. There was produced no precipitate in the aqueous solution. The aqueous solution was then subjected to the hydrothermal treatment, and the obtained powder was analyzed by means of an X-ray diffractometer. It was confirmed that the product was crystalline Lu0.995BO3:0.005Ce compound of vaterite type in a single phase. After the product was fired, the stimulated emission properties of the obtained powder was measured. The same graph as FIG. 2 was obtained. Lu0.995BO3:0.005Ce Stimulable Phosphor The procedure of Example 1 was repeated except that 2.585 g of Lu(NO3)3.4H2O, 0.013 g of Ce(NO3)3.6H2O, 0.408 g of H3BO3 and 1.772 g of acetamide were used as the starting materials, to prepare the stimulable phosphor of the invention represented by the titled formula in the form of powder. There was produced no precipitate in the aqueous solution. The aqueous solution was then subjected to the hydrothermal treatment, and the obtained powder was analyzed by means of an X-ray diffractometer. It was confirmed that the product was crystalline Lu0.995BO3:0.005Ce compound of vaterite type in a single phase. After the product was fired, the stimulated emission properties of the obtained powder was measured. The same graph as FIG. 2 was obtained. Stimulable Lu0.995Bo3:0.005Ce Phosphor The procedure of Example 1 was repeated except that 2.325 g of LuCl3.6H2O, 0.011 g of CeCl3.7H2O, 0.408 g of H3BO3 and 1.772 g of acetamide were used as the starting materials, to prepare the stimulable phosphor of the invention represented by the titled formula in the form of powder. There was produced no precipitate in the aqueous solution. The aqueous solution was then subjected to the hydrothermal treatment, and the obtained powder was analyzed by Means of an X-ray diffractometer. It was confirmed that the product was crystalline Lu0.995BO3:0.005Ce compound of vaterite type in a single phase. After the product was fired, the stimulated emission properties of the obtained powder was measured. The same graph as FIG. 2 was obtained. Radiation Image Storage Panel (1) Preparation of Phosphor Sheet Stimulable phosphor: Lu0.99875BO3: 0.001Ce, 0.00025Sm 100 gpowder (prepared in Example 1)Binder: Polyurethane elastomer [Pandex T-5265H (solid),23.7 gfrom Dainippon Ink & Chemicals, Inc.] dissolved inmethyl ethyl ketone [solid content: 15 wt. %]Anti-yellowing agent: Epoxy resin [Epikote #1004 (solid), 1.0 gYuka Shell Epoxy Kabushiki Kaisha]Crosslinking agent: Polyisocyanate resin [Colonate 0.7 gHX (solid content: 100%), Nippon Polyurethane Co.,Ltd.] dissolved in methyl ethyl ketone [solid content:71 wt. %] The above-mentioned materials were added to 13 g of methyl ethyl ketone (MEK), and mixed and dispersed by means of a propeller mixer to prepare a coating solution. The prepared coating solution was pumped to send at a constant flow (160 ml/minute) and to spread on a temporary support (polyethylene terephthalate sheet having a surface beforehand coated with a silicon releasing agent) of 188 μm thickness. The temporary support was then transferred into an oven, dried at 80° C. for 8 minutes, and then cooled. Thus, a phosphor sheet comprising the temporary support and a phosphor layer (thickness: 330 μm) provided thereon was prepared. (2) Preparation of Support A light-shielding layer of approx. 20 μm thickness [composition: carbon black, calcium carbonate, silica and binder (nitrocellulose and polyester resin) in the weight ratio of 10/21/16/53] was formed by coating procedure on one surface of a polyethylene terephthalate (PST) sheet [support, thickness: 350 μm, Melinex #992, from Du pont] containing barium sulfate (10 wt. %). The other surface was coated with a soft acrylic resin (Cryscoat P-1018GS [20% toluene solution], available from Dainippon Ink & Chemicals, Inc.) to form an undercoating layer (thickness: 20 μm). (3) Mounting of Phosphor Layer The phosphor layer was peeled from the temporary support of the phosphor sheet, laid on the undercoating layer of the support, and continuously hot-pressed by means of a calender roll (pressure: 500 kgw/cm2, temperature of the upper roll: 75° C., temperature of the lower roll: 75° C., transferring rate: 1.0 m/minute), so that the phosphor layer (thickness: 230 μm) was completely fixed onto the support via the undercoating layer. (4) Formation of Protective Layer On a PET film (protective film, thickness: 9 μm, Lumilar 9-P53 Toray Industries, Inc.) was coated an unsaturated polyester resin solution (Byron 30SS, Toyobo Co., Ltd.) and dried to form an adhesive layer (applied amount: 2.0 g/m2). Thus treated PET film was fixed onto the phosphor layer via the adhesive layer by means of laminating rolls, to give a protective layer. Thus, the radiation image storage panel of the invention shown in FIG. 5 was produced. It was confirmed that the obtained storage panel after exposed to X-rays gave off stimulated emission when exposed to a semi-conductor laser beam of 633 nm. Radiation Image Storage Panels The procedure of Example 6 was repeated except that each powdery phosphor prepared in Examples 2 to 5 was used, to produce various radiation image storage panels of the invention. It was confirmed that all of the produced storage panel after exposed to X-rays gave off stimulated emission when exposed to a semi-conductor laser beam of 633 nm.
053848128	abstract	A cabling arrangement is provided for a nuclear reactor located within a containment. Structure inside the containment is characterized by a wall having a near side surrounding the reactor vessel defining a cavity, an operating deck outside the cavity, a sub-space below the deck and on a far side of the wall spaced from the near side, and an operating area above the deck. The arrangement includes a movable frame supporting a plurality of cables extending through the frame, each connectable at a first end to a head package on the reactor vessel and each having a second end located in the sub-space. The frame is movable, with the cables, between a first position during normal operation of the reactor when the cables are connected to the head package, located outside the sub-space proximate the head package, and a second position during refueling when the cables are disconnected from the head package, located in the sub-space. In a preferred embodiment, the frame straddles the top of the wall in a substantially horizontal orientation in the first position, pivots about an end distal from the head package to a substantially vertically oriented intermediate position, and is guided, while remaining about vertically oriented, along a track in the sub-space to the second position.
	abstract	Performance monitors (PMs) are provided in a system to identify the execution time for data being transferred within the system and determine operation parameters of the system based on the rate data is transferred. The operation parameters are then used to configure hardware within the system. The PMs can provide a histogram of the transactions usable to evaluate system performance. The PMs can provide a time line diagram of the transactions to show the specific order the transactions occurred. The PMs can be provided in a multi-port memory controller (MPMC) to monitor the speed of read and write transactions from the MPMC ports, and used to configure logic within the MPMC to maximize the rate of data flow.
044951400	description	DETAILED DESCRIPTION OF INVENTION The plant 10 shown in FIG. 1 includes a nuclear reactor 11 which serves as a prime energy source to drive the propulsors 13 from power-conversion system 15. This plant 10 may be used to drive the propeller 16 of a ship 18. The nuclear reactor 11 may also be cooled by an emergency cooling system 17 in the event of an emergency. The reactor 11 has a fissile core 19. Typically the reactor 11 may be a 300 megawatt reactor that transfers energy to a working fluid coupled directly to a regenerative Brayton cycle. The coupling is shown in FIG. 1 as an energy conversion loop with the conduits through which the coolant flows in heavy lines. Typically the coolant is helium. It may also be another gas such as argon or hydrogen. In the main power conversion loop 15 the working fluid flows from the hot leg 29 of the reactor through a shutdown valve 31, a gas-generator turbine 33, the power turbine 35 which drives the propulsors 13, a recuperator 37, the primary 38 of a precooler 39, a low-pressure compressor 41, the primary 42 of intercooler 44, a high-pressure compressor 43, the primary 45 of the recuperator 37, a check valve 47, to the cold leg 49 to the reactor 11. The working fluid can also flow in a like parallel power-conversion loop 50 (not shown completely) through shutdown valve 51 and back through check valve 53. The turbine 33 drives the compressors 41 and 43. The heat rejected in the recuperator 37 preheats the compressed working fluid returning to the reactor 11. The precooler 39 is connected to a heat absorber (not shown) through valve 56. The intercooler 44 is connected to a heat absorber (not shown) through valve 48. The power-conversion loop 15 includes a working fluid cleanup system 55. This system 55 includes a molecular sieve 57 and charcoal bed 59 for purifying the coolant. A small portion, typically 3% of the working fluid, is continuously tapped from the conduit section 61 and passed through a heat economizer or heat absorber 63 and through the seive 57 and charcoal bed 59. the power-conversion loop 15 includes a system 65 for varying the power delivered by the plant. This system includes storage containers or bottles 67 and 69 of the working fluid and valves 71, 73, 75, 77, 79. The purified working fluid flows from charcoal bed 59 through the primary 81 of heat absorber 63 to the valves 71, 73, 75. Valve 71 is connected directly to conduit section 83 of the main loop 15. Valves 73 and 75 are connected to the containers 67 and 69. The containers 67 and 69 are connected to conduit section 85 through valves 77 and 79. During steady-state operation valve 71 is open and valves 73, 75, 77 and 79 are closed. The purified gas (working fluid) is fed into the reactor 11 through the main conduit. To reduce power, valve 71 is closed, valves 77 and 79 remain closed, and either valves 73 or 75 are opened. The working fluid, typically at the rate of 3% per second, is fed into either containers 67 or 69. The working fluid in the main loop 15 and the power are reduced. Valve 71 remains closed and valves 73 or 75 remain open until the power is reduced to the desired magnitude. To increase power, valve 71 remains open, valves 73 and 75 are closed and valves 77 or 79 are opened. Additional working fluid, typically at the rate of 3% per second, is then supplied through conduit section 85. Valves 77 or 79 are closed when the power reaches the desired magnitude. The emergency cooling system 17 is connected in the upstream side of valve 31. It includes a turbine 91, a compressor 93 and a cooling heat exchanger 95. A pump 97 driven by the turbine 91 drives a cooling fluid, typically water, through the heat exchanger. The turbine 91 also drives the compressor 93. The emergency cooling system is automatically set into operation responsive to the needs of the nuclear reactor 11 and continues to circulate working fluid through the reactor. If a break occurs in the main conduit loop, the emergency cooling system is enabled. Under these conditions working fluid will only flow out of the power conversion system until the containment pressure equals the pressure in the power conversion system where the break exists. Working fluid now flows through turbine 91, the primary 105 of heat exchanger 95, compressor 93, check valve 107, conduit 133, reactor core 19, cold leg 29 to turbine 91. Turbine 91 drives compressor 93 and provides a flow of working fluid through reactor 11. The core 19 (FIG. 2) is typically formed of hexagonal graphite fuel elements 111 with corresponding sides abutting to form a generally cylindrical structure. The fuel is in the form of beads as shown in FIG. 4 of Jones U.S. Pat. No. 4,021,298. The beads have a kernel of highly enriched uranium 235 or in any other fissile isotopes. Typically, the enrichment is up to 93%. The beads are embedded in the elements 111. Usually the elements are extruded from a mass containing the beads. Typically the distance between opposite flat surfaces 113 and 115 of an element is 3/4 inch and the length of an element is 45 inches. The elements 111 have perforations 117 through which the coolant flows. For permanently deactivating the reactor 11, the apparatus includes a container 121 (FIG. 1) containing a boron compound under pressure. Alternatively there may also be a container 123 containing a reacting agent under pressure in addition to container 121. Each container 121 and 123 is connected through valves 125 and 127 respectively and through the cold leg 49 directly to the reactor 11 through its pressure vessel 129. The containers 121 and 123 may also be connected through valves 125 and 127 to the conduit 133 downstream from check valve 107 as shown in broken lines. The valves 125 and 127 are normally closed. On the occurrence of an emergency they are opened by a control 131. The boron container 121 contains a boron compound such as triethylboron or an aminoborane, and these compounds may be directly injected into the reactor. Alternatively, container 121 may contain diborane. In this case container 123 includes a reacting agent such as acetylene, an alkyl hydrocarbon or ammonia. When the substances from containers 121 and 123 are injected into the working fluid, they react in the heat of the fluid producing the alkyboranes, alkydiboranes, carboranes, or boron nitrogen oligomers. These resulting compounds are carried through the perforations 117 in the fuel elements 111. They dissociate on the heat of the core producing predominantly boron, boron carbide or a boron-carbon polymer and, in the case of the boron nitrogen oligomers boron nitride or a boron-nitrogen polymer which adhere to the walls of the perforations. The boron is usually enriched in boron 10 so that the reactor 11 is deactivated. If a boron-carbon or boron-nitrogen compound or a metal borohydride serve as deactivating compounds, no reacting agent is necessary. For example, triethyl boron, aminodiborane or a metal borohydride are held under high pressure in container 121 and injected into the coolant on the occurrence of an emergency. If the compounds are liquids they may be sprayed into the coolant stream from the pressurized container 121. If the compounds are solids, they may be contained in the container 121 as a powder, and blown into the coolant when valve 125 is opened. The compounds, be they solid, liquid or gas, dissociate as they pass through the coolant channels in the structure 111. The resulting metal boride and/or other boron compounds deposit on the walls of the coolant channels. The typical above mentioned 300 MW.sub.t plant consists of the reactor 11 with an open volume of 53 cubic feet, the plug shield and plenum (not shown) with a volume of 99 cubic feet, and the emergency cooling system circulator and heat exchanger with a volume of 20 cubic feet. Helium circulation through the system is at a rate of 11 lb/sec and a single-pass flow-through time, of about 2.5 seconds. A reactive compound introduced into the emergency cooling system 17 makes at least about 8 passes through the core 19 before the influx of water begins. Maximum deposition is required to occur to effectively terminate the nuclear reactions before water influx begins. Calculations based on neutronic considerations indicate that a conservative estimate of 10 Kg of B-10 as boron or as a refractory compound uniformly distributed on the core channel surface area of about 2,625,000 cm.sup.2, in the case of the typical 300 MW.sub.t plant, will poison a water-flooded reactor. This requires the deposition of approximately 0.004 gm B-10/cm.sup.2 or an approximate thickness of 0.6 mil (3.8 mils natural boron carbide). For maximum effectiveness, as much of the B-10 containing compound as possible should be deposited in a single pass through the core. The deposit should be in a form of a film so that it does not block a flow passage. Candidate compounds must be capable of being stored in a container subject to ambient conditions of atmospheric pressures to 300 psi and 140.degree. to 200.degree. F. for long periods of time. Although storage is assumed to be inside the containment vessel, storage outside the containment, may be necessary if long term stability cannot be guaranteed and periodic replacement with fresh compound is required. However, it is desired to keep penetrations of the containment vessel to a minimum and compounds with long-term stability should be chosen. The compound will be injected into the working fluid, under high pressure, in the event of a sinking accident. The most desirable point of injection is directly above the reactor core. The goal is for the compound to dissociate and/or react to give a high yield of a distributed boron-containing deposit in each pass over a surface having both radial and axial temperature gradients. As mentioned, there are at least eight passes before water is introduced into the reactor containment. Flooding of the core must not adversely affect the deposit, and the deposit may be able to remain indefinitely adherent to the substrate and not be adversely affected by the corrosive aqueous environment. The boron, boron carbide, boron nitride and the metal borides meet these conditions. While preferred practices and embodiments of this invention have been disclosed herein, many modifications thereof are feasible. This invention is not to be restricted except insofar as is necessitated by the spirit of the prior art.
042108179	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to the art of taking x-ray pictures of a common object along two sight lines and, more particularly, to means for preventing cross-fogging of the x-ray pictures in such an arrangement. 2. Prior Art: In a radiographic practice known as angiography, a radiopaque or contrast material is injected into the blood or lymphatic vessels of a patient and its progress through these vessels is observed by taking a series of x-ray pictures. The contrast materials currently used are toxic and, therefore, the amount injected into the patient must be limited. However, often it is necessary in this practice to obtain x-ray pictures in multiple projections, such as the front and side and so forth. In order to accommodate this requirement while minimizing both time of examination and the amount of contrast material used, pairs of x-ray tubes and film changers at right angles to each other have been used simultaneously, thus obtaining two orthogonal projections for each injection of contrast material. It is well known that x-rays interact with the matter being x-rayed to produce scattering. This phenomenon, known as the Compton effect, produces noise on the x-ray film. While means have been devised to diminish the effect of scattered radiation on the primary film, namely the Potter-Bucky grid which is placed between the object being x-rayed and the film to absorb radiation which is not parallel to the line of sight of the picture, no attention has been focused on diminution of noise caused by scattered radiation from the second axis in a two axis angiogram. It is a primary object of this invention to provide means to eliminate cross-fogging between the two axes of a two axis angiogram. It is another object of this invention to eliminate such cross-fogging by means which are simple, reliable and inexpensive. SUMMARY OF THE INVENTION According to the invention, cross-fogging in biplane radiography is eliminated by shields having radiolucent and radiopaque portions which are alternately disposed in front of the film changers. Means are provided to synchronize the two shields such that the radiopaque portion of one shield is disposed in front of the film presented for exposure by its associated film changer when the radiolucent portion of the other shield is disposed in front of the film presented for exposure by the other film changer. In one embodiment of the invention, the shield is in the form of a flexible endless belt having alternating radiolucent and radiopaque sections. The belt is mounted such that it forms a loop surrounding the film changer. In another embodiment of the invention, the shield is a planar member mounted for movement in a plane parallel to the plane of the film presented for exposure. This shield may comprise a disc having alternating sectors of radiolucent and radiopaque material which is rotated in a plane parallel to and in front of the film or it may be a planar member having one radiopaque and one radiolucent section which is mounted for reciprocal movement in front of the film changer.
	claims	1. A method for generating and maintaining a magnetic field with a field reversed configuration (FRC) within a confinement chamber of a system comprising:first and second diametrically opposed FRC formation sections coupled to the confinement chamber,first and second divertors coupled to the first and second formation sections,one or more of a plurality of plasma guns, one or more biasing electrodes and first and second mirror plugs, wherein the plurality of plasma guns includes first and second axial plasma guns operably coupled to the first and second divertors, the first and second formation sections and the confinement chamber, wherein the one or more biasing electrodes being positioned within one or more of the confinement chamber, the first and second formation sections, and the first and second divertors, and wherein the first and second mirror plugs being position between the first and second formation sections and the first and second divertors,a gettering system coupled to the confinement chamber and the first and second divertors,a plurality of neutral atom beam injectors coupled to the confinement chamber adjacent a midplane of the confinement chamber and oriented to inject neutral atom beams toward the mid-plane at an angle of about fifteen degrees (15°) to twenty-five degrees (25°) less than normal to a longitudinal axis of the confinement chamber, anda magnetic system comprising a plurality of quasi-de coils positioned around the confinement chamber, the first and second formation sections, and the first and second divertors, first and second set of quasi-dc mirror coils positioned between the confinement chamber and the first and second formation sections;the method comprising the steps of:forming an FRC about a plasma in the confinement chamber, wherein the FRC plasma is in spaced relation with the wall of the confinement chamber, andmaintaining the FRC at or about a constant value without decay by injecting beams of fast neutral atoms from neutral beam injectors into the FRC plasma at an angle of about 15° to 25° less than normal to the longitudinal axis of the confinement chamber and towards the mid-plane of the confinement chamber. 2. The method of claim 1 further comprising the step of generating a magnetic field within the chamber with the quasi-dc coils extending about the chamber and a mirror magnetic field within opposing ends of the chamber with the quasi-dc mirror coils extending about the opposing ends of the chamber. 3. The method of claim 1 wherein the step of the forming the FRC includes forming a formation FRC in the opposing first and second formation sections coupled to opposite ends of the confinement chamber and accelerating the formation FRC from the first and second formation sections towards the mid-plane of the chamber where the two formation FRCs merge to form the FRC. 4. The method of claim 3 wherein the step of forming the FRC includes one of forming a formation FRC while accelerating the formation FRC towards the mid-plane of the chamber and forming a formation FRC then accelerating the formation FRC towards the mid-plane of the chamber. 5. The method of claim 4 further comprising the step of guiding magnetic flux surfaces of the FRC into the diverters coupled to the ends of the formation sections. 6. The method of claim 5 further comprising the step of generating a magnetic field within the formation sections and diverters with quasi-dc coils extending about the formation sections and diverters. 7. The method of claim 6 further comprising the step of generating a mirror magnetic field between the formation sections and the diverters with quasi-dc mirror coils. 8. The method of claim 6 further comprising step of generating a mirror plug magnetic field within a constriction between the formation sections and the diverters with quasi-dc mirror plug coils extending about the constriction between the formation sections and the diverters. 9. The method of claim 1 wherein the step of maintaining the FRC further comprising the step of injecting pellets of neutral atoms into the FRC. 10. The method of anyone of claim 1 further comprising the step of generating one of a magnetic dipole field and a magnetic quadrupole field within the chamber with saddle coils coupled to the chamber. 11. The method of claim 1 further comprising the step of conditioning the internal surfaces of the chamber, formation sections, and diverters with the gettering system. 12. The method of claim 11 wherein the gettering system includes one of a Titanium deposition system and a Lithium deposition system. 13. The method of claim 1 further comprising the step of axially injecting plasma into the FRC from the axially mounted plasma guns. 14. The method of claim 1 further comprising the step of controlling the radial electric field profile in an edge layer of the FRC. 15. The method of claim 14 wherein the step of controlling the radial electric field profile in an edge layer of the FRC includes applying a distribution of electric potential to a group of open flux surfaces of the FRC with the biasing electrodes. 16. A system for generating and maintaining a magnetic field with a field reversed configuration (FRC) comprisinga confinement chamber,first and second diametrically opposed FRC formation sections coupled to the confinement chamber,first and second divertors coupled to the first and second formation sections,one or more of a plurality of plasma guns, one or more biasing electrodes and first and second mirror plugs, wherein the plurality of plasma guns includes first and second axial plasma guns operably coupled to the first and second divertors, the first and second formation sections and the confinement chamber, wherein the one or more biasing electrodes being positioned within one or more of the confinement chamber, the first and second formation sections, and the first and second divertors, and wherein the first and second mirror plugs being position between the first and second formation sections and the first and second divertors,a gettering system coupled to the confinement chamber and the first and second divertors,a plurality of neutral atom beam injectors coupled to the confinement chamber adjacent a midplane of the confinement chamber and oriented to inject neutral atom beams toward the mid-plane at an angle of about fifteen degrees (15°) to twenty-five degrees (25°) less than normal to a longitudinal axis of the confinement chamber, anda magnetic system comprising a plurality of quasi-dc coils positioned around the confinement chamber, the first and second formation sections, and the first and second divertors, first and second set of quasi-dc mirror coils positioned between the confinement chamber and the first and second formation sections,wherein the system is configured to generate an FRC and maintain the FRC without decay while the neutral beams are injected from neutral beam injectors into the FRC plasma at an angle of about 15° to 25° less than normal to the longitudinal axis of the confinement chamber and towards the mid-plane of the confinement chamber. 17. The system of claim 16 further comprising two or more saddle coils coupled to the confinement chamber. 18. The system of claim 17 further comprising an ion pellet injector coupled to the confinement chamber. 19. The system of claim 16 wherein the formation section comprises modularized formation systems for generating an FRC and translating it toward a midplane of the confinement chamber. 20. The system of claim 16 wherein biasing electrodes includes one or more of one or more point electrodes positioned within the containment chamber to contact open field lines, a set of annular electrodes between the confinement chamber and the first and second formation sections to charge far-edge flux layers in an azimuthally symmetric fashion, a plurality of concentric stacked electrodes positioned in the first and second divertors to charge multiple concentric flux layers, and anodes of the plasma guns to intercept open flux.
	claims	1. A telescoped control rod for a pebble-bed high-temperature gas-cooled reactor, comprising an inner rod, an outer rod and a guide cylinder assembly which are vertically and coaxially arranged, wherein the outer rod and the guide cylinder assembly are hollow cylindrical bodies; the top end of the inner rod can move up and down inside the outer rod and the other end of the inner rod moves up and down, along with the top end, inside a control rod passage which is positioned below the guide cylinder assembly and is coaxial with the guide cylinder assembly; and the top end of the outer rod can move up and down in the guide cylinder assembly and the other end of the outer rod moves up and down, along with the top end, inside the control rod passage,wherein the inner rod is of a multi-section structure and comprises a coupling head assembly, an anti-impact head assembly and a plurality of internal section rods connected in series by sphere articulated joints, one end of the coupling head assembly is connected with the internal section rod at a first section and the other end of the coupling head assembly is connectable with a loop chain of a control rod driving mechanism; and one end of the anti-impact head assembly is connected with the internal section rod at a tail section,wherein the coupling head assembly comprises a coupling head, a flat pin, a locking bead ring, a buffer pressure plate, a cylinder spring, a bearing pressure plate, a ceramic ball, a bearing bottom plate and a sphere joint; the coupling head is connected with the loop chain of the control rod driving mechanism by the flat pin and the locking bead ring is used for encircling and fastening the flat pin; andthe buffer pressure plate is arranged on the cylinder spring to form a buffer structure, the buffer structure is externally arranged on the side wall of the coupling head, the sphere joint is in threaded connection with the bearing pressure plate and is in spherical fit with an internal section rod upper end plate, a thrust bearing structure is formed by the ceramic ball, the bearing pressure plate and the bearing bottom plate together, and the thrust bearing structure is externally sleeved by the coupling head. 2. The telescoped control rod for the pebble-bed high-temperature gas-cooled reactor according to claim 1, wherein each internal section rod comprises an outer sleeve, the upper end plate and a lower end plate which are respectively positioned at both ends of the outer sleeve, and a B4C pellet which is welded and packaged between the upper end plate and the lower end plate and is positioned in the outer sleeve; gaps are reserved between the B4C pellet and the outer sleeve and between the B4C pellet and the upper end plate; and a hold-down spring is arranged between the B4C pellet and the upper end plate. 3. The telescoped control rod for the pebble-bed high-temperature gas-cooled reactor according to claim 2, wherein the anti-impact head assembly comprises a buffer pressure plate, a disk spring and an anti-impact head of which the side wall is provided with a bulge; and the disk spring is arranged between the bulge and the buffer pressure plate. 4. The telescoped control rod for the pebble-bed high-temperature gas-cooled reactor according to claim 1 , wherein the guide cylinder assembly is fixedly mounted on an upper bearing plate for metal reactor internals and comprises an upper segment, a middle segment and a lower segment; the upper segment and the middle segment are fixedly mounted on the upper bearing plate for the metal reactor internals together; the upper segment is positioned above the bearing plate and a gap is reserved between the upper segment and a reactor pressure vessel sealing head; the middle segment is positioned under the bearing plate and passes through a plurality of layers of reactor core pressure plates; the bottom of the middle segment is inserted into the lower segment; the lower segment is fixed to a metal reactor internal positioning plate; and a positioning ring is welded at the lower end of the lower segment. 5. A telescoped control rod for a pebble-bed high-temperature gas-cooled reactor, comprising an inner rod, an outer rod and a guide cylinder assembly which are vertically and coaxially arranged, wherein the outer rod and the guide cylinder assembly are hollow cylindrical bodies; the top end of the inner rod can move up and down inside the outer rod and the other end of the inner rod moves up and down, along with the top end, inside a control rod passage which is positioned below the guide cylinder assembly and is coaxial with the guide cylinder assembly; and the top end of the outer rod can move up and down in the guide cylinder assembly and the other end of the outer rod moves up and down, along with the top end, inside the control rod passage,wherein a top inner shrunk opening and a top outer shaft shoulder are formed at the top of the outer rod; and the outer rod is of a multi-section structure and comprises a sliding sleeve type shock absorber, hanging assemblies and a plurality of external section rods, the hanging assemblies are connected with the corresponding external section rods, and the sliding sleeve type shock absorber is connected with the external section rod at a first section, andwherein each external section rod comprises an inner sleeve, an outer sleeve, an upper end plate, a lower end plate, a hold-down spring and a B4C pellet; the B4C pellet is mounted in an annular space defined by the inner sleeve, the outer sleeve, the upper end plate and the lower end plate and gaps are reserved between the B4C pellet and the inner and outer sleeves as well as the upper end plate; the hold-down spring is arranged between the B4C pellet and the upper end plate; and the outer sleeve is provided with a vent hole. 6. The telescoped control rod for the pebble-bed high-temperature gas-cooled reactor according to claim 5, wherein the guide cylinder assembly is fixedly mounted on an upper bearing plate for metal reactor internals and comprises an upper segment, a middle segment and a lower segment; the upper segment and the middle segment are fixedly mounted on the upper bearing plate for the metal reactor internals together; the upper segment is positioned above the bearing plate and a gap is reserved between the upper segment and a reactor pressure vessel sealing head; the middle segment is positioned under the bearing plate and passes through a plurality of layers of reactor core pressure plates; the bottom of the middle segment is inserted into the lower segment; the lower segment is fixed to a metal reactor internal positioning plate; and a positioning ring is welded at the lower end of the lower segment. 7. The telescoped control rod for the pebble-bed high-temperature gas-cooled reactor according to claim 5, wherein all the hanging assemblies are the same in the number of hanger ring structures arranged; each hanger ring structure comprises two sphere pendants, two cylindrical pins, a long hanger ring and two check rings; the sphere pendants are mounted in inner side grooves of the upper end plates and the lower end plates; the sphere pendants are connected with the long hanger ring by the cylindrical pins and the cylindrical pins are fixed by the check rings; and gaps are reserved among the sphere pendants, the cylindrical pins and the long hanger.
047387998	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS One preferred embodiment of a disposable cartridge according to the invention is illustrated in Figure 1 where the cartridge has the form of a cylindrical container defined by a cylindrical side wall 1, a bottom cover 2 and a top cover 3, the bottom cover 2 and the top cover 3 being permanently secured to respective axial ends of cylindrical side wall 1 to delimit a closed space. The top cover 3 includes a plate portion 4 and an upstanding portion 5 presenting, at its upper end, an inwardly directed annular flange 6. Secured to, and passing through, plate portion 4 are three tubular conduits 8, 9 and 10 which project upwardly beyond annular flange 6 and whose upper ends are formed to define male nozzles or couplers. Conduit 8 is centered on the axis of the cartridge and extends downwardly to the region of the bottom of the space enclosed by the container, which space constitutes a waste storage region. Conduits 9 and 10, on the other hand, terminate at the lower surface of plate portion 4 and thus open into the upper region of the enclosed space. Within the enclosed space defined by the container, there are disposed two annular, perforated retainer-distribution plates 12 and 13, each surrounding, and secured to, tubular conduit 8. The upper perforated plate 12 is secured to top cover 3 and defines therewith an annular space 15. Similarly, lower perforated plate 13 is secured to bottom cover 2 and defines therewith a circular space 16. All of the components identified thus far are preferably made of fiberglass, or other suitable plastic, and are firmly bonded together, as by cementing, to form a single, rigid unit. Plates 12 and 13 delimit an annular space which is filled with a fibrous mass 18 constituting a ferromagnetic filter matrix and preferably constituted by ordinary steel wool. The use of steel wool as a matrix for electromagnetic filters is well known in the art and has been found to be highly efficient in producing the steep magnetic field gradients needed to filter such weakly paramagnetic particles as cupric oxide from coolant streams. Magnetically saturated nickel ferrite (also known colloquially as "crud") is attracted by a given magnetic gradient and field strength to an extent which is three orders of magnitude greater than cupric oxide of the same particle size. Steam generator sludge is mostly magnetite, which is magnetically similar to nickel ferrite, together with other magnetic oxides of iron and copper. Particle size is the main consideration in selecting a proper matrix for the system according to the present invention. As is disclosed in the article by J. A. Oberteuffer, Magnetic Separation: A Review of Principles, Devices, and Applications, IEEE Trans. on Mag., Volume Mag-10, June, 1974, the optimum matrix element diameter is about three times that of the particles to be trapped. Therefore, a fine steel wool will give better results than coarser screen matrices for very small particles. In the usual electromagnetic filter, a graded screen matrix is employed since the filter must both be an efficient filter when the magnetic flux is applied and a poor filter, so as to be easily backflushed, when the flux is removed. Since, in the present case, there is no backflush requirement for the filter itself, a graded screen matrix is not required. The bottom cover 2 of the embodiment shown in FIG. 1 is provided with a groove which is formed to mate with a lug on the conveyor which will transport the cartridge to its associated filling station. This groove assures correct orientation of the cartridge and therefore of its conduits 8, 9 and 10, at the filling station. Reverting to top cover 3, the upstanding portion 5 and annular flange 6 cooperate to form a reservoir in which any spilled liquid will collect, and from which that liquid can be removed before the cartridge is installed and sealed into a permanent storage drum. Flange 6 also serves as a lifting lug and gripping ring via which the cartridge is raised into its filling position at the filling station, as will be described below. Two outlet conduits are provided because the waste loading operation and the resin filling operation present different requirements; the valve in conduit 10 for monitoring the resin filling operation would interfere with fluid flow during waste loading. The disposal system for loading the cartridge with particulate waste includes a loading head and turret assembly having conduits constructed to mate with the conduits 8, 9 and 10 to provide the requisite fluid flow connections. FIG. 2 is a bottom plan view of one preferred embodiment of the loading head and turret assembly, which is essentially composed of a cylindrical housing 21 closed at the top and open at the bottom, and a turret 23 carrying five conduits 24, 25, 26, 27 and 28. Turret 23 is mounted in housing 21 to be pivotal about the axis of conduit 24, as will be described in detail below. The lower end of each of conduits 24-28 is given the form of a female coupler constructed to form a releasable, sealed connection with the coupler at the upper end of a respective one of the conduits 8, 9 and 10, of FIG. 1. At the lower edge of cylindrical housing 21 there is provided an annular gasket 30 for forming a sealed connection between the lower housing edge and the upper surface of top cover 3 of the cartridge. Housing 21 carries three equispaced locking and lifting cams 32 which are pivotal between a locking position, shown in solid lines, in which they will bear against the lower surface of flange 6 to press that flange against gasket 30, and a release position, shown for one of cams 32 in broken lines, which permits the loading head and turret assembly to be lifted away from the cartridge. The turret 23 is pivotal, about the axis of conduit 24, between two operating positions. In both operating positions, conduit 24 is located to be coupled to conduit 10 of the cartridge. In the first operating position, associated with the introduction of particulate waste material into the cartridge, the position of turret assembly is such that conduit 26 will mate with conduit 8 and conduit 25 will mate with conduit 9. In the second operating position, employed for backfilling the cartridge with resin, conduit 28 will mate with conduit 8 and conduit 27 will mate with conduit 9. Turret 23 additionally carries a siphon tube 33 for siphoning off any liquid which may accumulate in the reservoir formed by upstanding portion 5 and annular flange 6 of top cover 3. FIG. 3 is a detail view illustrating the conduits 10 and 24 in their coupled position, which exists when the disposal cartridge is secured to the loading head and turret assembly and turret 23 is in its lowered position. At its lower end, the interior of conduit 24 has a conical wall which opens downwardly and in which is seated a gasket 35 made of neoprene, or other suitable material. Gasket 35 is dimensioned to effect a sealed coupling between the upper end of conduit 10 and the lower end of conduit 24. As indicated above in the description of Figure 1, conduit 10 is provided with a check valve which is composed of a valve stem and body 37 and a valve guide and seat 38 secured to the interior wall of conduit 10. A retainer disc 39 is secured to the valve stem and normally rests upon the upper edge of valve guide and seat 38. Retainer disc 39 is configured to rest against the upper edge of valve guide and seat 38, while permitting the flow of air therepast, when the valve is in its open position. The valve is biased in its open condition by a light spring 40 whose upper end is secured within conduit 24 and whose lower end bears against the upper surface of disc 39. Associated with the upper end of valve stem and body 37 is a microswitch 42 which will be actuated when the valve is closed by upward pressure exerted by plotting resin in conduit 10. Otherwise, the valve assembly remains in its open condition. FIG. 4 is an elevational view, partly in cross-section, illustrating one preferred embodiment of the loading head and turret assembly of FIG. 2 secured to the top of the cartridge shown in FIG. 1. For the sake of clarity, only the annular flange 6 and part of the upstanding portion 5 of the cartridge are shown in FIG. 4, i.e. the conduits forming part of that cartridge are not illustrated. In addition, only the cylindrical side wall of housing 21 is shown in cross-section. Turret 23 is shown in its raised, or retracted, position, in which position the lower ends of conduits 24-28 are separated from the upper ends of conduits 8-10. Turret 23 is supported for pivotal movement about the axis of conduit 24 by means of a column 44 which extends upwardly through the top of housing 21 via a suitable opening which is provided in the top of the housing and which may be furnished with a suitable seal. Column 44 is provided, near its top, with a bearing collar 45 which is secured to column 44 and rests upon a support plate 46. Thus, plate 46 supports column 44 and turret 23 through the intermediary of bearing collar 45. Column 44 and collar 45 are rotatable, about the axis of conduit 24, relative to plate 46. For this purpose, collar 45 can include a suitable roller bearing or slide bearing via which it rests upon plate 46. Plate 46 is supported by a plurality of piston-cylinder assemblies 47. Typically, three such assemblies can be provided, two of which are visible in FIG. 4. The cylinder portions of assemblies 47 are supported on the top of housing 21, while the piston rods thereof support plate 46. Assemblies 47 may be of the pneumatic type. Supported from the underside of plate 46 is a further piston-cylinder assembly 49 whose piston is articulated to a lug 50 carried by column 44. Assembly 49, which may also be of the pneumatic type, is operated to act on lug 50 in order to rotate column 44 between the two operating positions of turret 23. Also mounted on the top of housing 21 is a guide collar 52 which is fixed to the top of housing 21 and serves to assist in guiding the movements of column 44. Collar 52 is provided with two keyways 53, either one of which may cooperate with a key 54 secured to column 44 in order to maintain turret 23 in the desired operating position when column 44 and turret 23 have been lowered to couple appropriate ones of conduits 24-28 with conduits 8-10. Plate 46 additionally supports, via a support arm 56, a rotary coupling 57. The coupling 57 is thus prevented from rotating when column 44 is rotated by the action of piston-cylinder assembly 49. Coupling 57 contains a conventional mechanically operated valve which can be shifted between an open position and a closed position by rotation of column 44 relative to rotary coupling 57. The fluid passage associated with conduit 24 extends upwardly through the entire length of column 44 to communicate with the flow path defined by the above-described valve. The flow passages in conduits 25, 26 and 28 are connected, at the top of turret 23, to flexible hoses 59 which pass out of housing 21 and are coupled to suitable valves of the disposal system, to be described below. The valve in rotary coupling 57 is similarly connected to the remainder of the disposal system via a flexible hose 60. Housing 21 further carries three locking and lifting cams, only one of which is shown in FIG. 4 to facilitate clarity of the illustration of the other components shown in that figure. Each cam 32 is supported by a support rod 62 extending upwardly through the top of housing 21 and terminating at its upper end in a circular shoulder 63. The opening through which rod 62 passes may be provided with a suitable seal if required. Rod 62 also passes through a guide block 65 provided with a camming groove 66. Rod 62 carries a cam follower 67, which may be in the form of a roller, constructed to cooperate with groove 66. Locking and lifting cam 32 is biased into the locking position, shown in FIG. 4, by a suitable compression spring 68 held between shoulder 63 and guide block 65. The system can also be provided with suitable interlocks associated, inter alia, with assemblies 70 and 47 to prevent the conduits on turret 23 from engaging conduits 8, 9 and 10 if cartridge 75 is not properly locked to head 21 or the conduits are not properly aligned. For moving each cam 32 into its release position, there is provided a further pneumatic piston-cylinder assembly 70 carried by a support arm 71 secured to the top of housing 21. The piston rod of assembly 70 bears against the top of shoulder 63. When air under pressure is supplied to assembly 70, the piston thereof is forced downwardly, causing follower 67 to follow camming groove 66. Because of the configuration of groove 66, this produces an initial downward movement of cam 32, followed by a rotation thereof into the release position shown in broken lines in FIG. 2. Thus, the mechanism for controlling the movement of each cam 32 is of the "fail-safe" type in that a failure in the high pressure air supply will assure that spring 68 brings or maintains cam 32 in its locking position. When the three cams 32 are in their locking position, gasket 30 is pressed between the upper surface of flange 6 and the lower edge of housing 21 in order to seal the region enclosed thereby. When the turret assembly is lowered to bring selected ones of conduits 24-28 into communication with conduits 8-10, the lower end of siphon tube 33 will come within a fraction of an inch of the upper surface of plate portion 4 of the cartridge, so that siphon tube 33 can be employed to withdraw any liquid which may have spilled into the reservoir above plate portion 4 and enclosed by upstanding portion 5 and flange 6. As also shown in FIG. 4, the upper end of siphon tube 4 is connected to a flexible tube via which any liquid extracted by the siphon is conducted to a suitable storage tank. FIG. 5 illustrates, in schematic form, one suitable embodiment of a backflush disposal system according to the invention for loading a cartridge with particulate waste. The system includes a conveyor 74, which can be of any suitable conventional type, on which a cartridge 75, having the form shown in FIG. 1, and a disposal drum 76 are conveyed in succession in the direction of arrow 77. Conveyor 74 includes a suitable lug which mates with the groove in bottom cover 2 in order to assure correct orientation of cartridge 75. When cartridge 75 arrives at a drumming station, it comes to a position below an annular solenoid 78 presenting a circular, vertical passage into which drum 75 and the loading head and turret assembly can be introduced. The loading head and turret assembly, and more specifically housing 21, is suspended from a hydraulic ram 80 via loader arms 81 secured to the top of housing 21, at diametrically opposed points adjacent its periphery. Fluid conduits 83, 84, 85, 86 and 87 extend from respective ones of the flexible hoses associated with the conduits 24, 25, 26 and 28 and siphon tube 33 carried by turret 23 (FIG. 4). In the embodiment shown in FIG. 5, conduit 83 is connected to siphon tube 33, conduit 84 is connected to, or constitutes an extension of, flexible hose 60, and conduits 85, 86 and 87 are connected to, or constitute extensions of, the flexible hoses 59 connected to conduits 28, 26 and 25, respectively. Conduit 27 of turret assembly 23 is utilized during the resin filling process, and is permanently blocked to seal conduit 9 during this process, as will be discussed in greater detail below. Each of conduits 83-87 is in the form of a flexible hose having a length selected to allow for the required vertical movements of the loading head and turret assembly. As with the other components of the system, these hoses are made of a material, or are provided with a lining, suitable for the fluids to be conveyed. Conduit 83 is connected to a pump 89 which is operated during the waste material filling process to remove any water or slurry that may collect in the reservoir provided at the top of the disposal cartridge. Conduits 84, 85, 86 and 87 are connected to respective ones of valves 90, 91, 92 and 93, which may be of any suitable, conventional type and which may be electrically operated at the appropriate times in the disposal process. These valves, like other valves provided in the system, are constructed, or lined, to be compatible with the materials being handled. Valve 90 could be eliminated since its function duplicates somewhat that of the valve in coupling 57. Valve 90 is connected to a conduit leading to a controlled vent, which may be of any suitable, conventional type. Valve 91 is connected via a conduit 96 to a source of a suitable resin-catalyst mixture which is to be pumped into the cartridge after it has been filled with waste material and dewatered. Valve 92 is connected to a conduit 97 which leads to a pump 98 for supplying the waste mixture which is to be delivered to the cartridge, as well as to a valve 99 via which clean flush water can be supplied and a valve 100 via which air under pressure can be supplied. Valve 93 is connected to a conduit 102 which communicates with the inlet of a flush water storage tank 103. Tank 103 has an outlet conduit connected to a pump 105 via which flush water is delivered to a device 120, such as one or more backflush filters, from which the waste material is to be removed. The system further includes a receiving tank 107 having an inlet conduit 108 connected to device 120 to receive the waste material to be stored and an outlet conduit connected to the inlet of pump 98 via a valve 109. Receiving tank 107 may be equipped with a stirrer driven by a motor 110. A conduit 112 leading to a controlled vent communicates with the upper region of the interior of each of tanks 103 and 107. The system shown in FIG. 5 can be operated as follows. A disposal cartridge 75 and a storage drum 76 are placed one behind the other on conveyor 74 and conveyor 74 is advanced in direction 77 to bring cartridge 75 into the position shown in solid lines. Cartridge 75 is correctly oriented by means of the cooperation between the groove in bottom cover 2 and the associated lug on conveyor 74, as described above. Ram 80 is then operated to lower arms 81, together with the loading head and turret assembly until cylinder 21 comes to rest against the upper surface of cartridge flange 6. At this time, turret 23 is in its raised position, shown in FIG. 4, and piston-cylinder assemblies 70 have been actuated so that cams 32 are in their release position. Turret 23 is, or has been, rotated into the operating position in which conduits 25 and 26 are in vertical alignment with conduits 9 and 8, respectively. Then, piston-cylinder assemblies 70 are deactuated to cause cams 32 to first rotate and then move upwardly into their locking position, this position being shown for one cam 32 in FIG. 4, whereupon cartridge 75 is connected in a sealed manner to housing 21. Piston-cylinder assemblies 47 are then controlled to permit support plate 46 to move downwardly, together with collar 45, column 44 and turret 23, so that conduits 25, 26 and 24 are coupled in a sealed manner to conduits 9, 8 and 10, respectively. At the same time as the above operations, or prior thereto, a slurry containing the particulate waste material to be disposed of is delivered into receiving tank 107 via conduit 108. If, for example, the slurry is to be received from backflush filters, this is achieved by pumping water from storage tank 103 to the filters via pump 105, thereby causing slurry to be conveyed via conduit 108 to tank 107. Then, solenoid 78 is energized to produce a magnetic field which traverses cartridge matrix 18. Typically, solenoid 78 is designed to produce, in its center passage in which cartridge 75 is disposed, a substantially uniform magnetic induction, or flux density, of the order of 5 kilogauss, when cartridge 75 is not present in the solenoid passage. When cartridge 75 is in the position shown in broken lines in FIG. 5, steel wool matrix 18 will create gradients in the magnetic field. Then, valves 92, 93 and 109 are opened, all of the other valves being closed, and pump 98 is placed into operation to pump slurry from tank 107 and via conduits 86, 26 and 8 into circular space 16 at the cartridge bottom. The slurry then flows upwardly through the perforations in plate 13 and into matrix 18, where the particulate waste products are held in matrix 18 under the influence of the existing magnetic field. The remaining filtrate which passes through the perforations in plate 12 and into annular space 15 can flow through conduits 9, 25, 87 and 102 and via valve 93 into flush water storage tank 103. A sufficient quantity of slurry is pumped into cartridge 75 to produce a full load of particulate waste material in matrix 18. Then valve 109 is closed, pump 98 is turned off, and valve 99 opened to convey clean flush water into the cartridge via conduit 8, the flush water also being conducted via conduits 9, 25, 87 and 102 to tank 103. Normally, two system volumes of flush water will be employed during each cartridge loading process. Periodically, some of the flush water held in tank 103 will be discharged to the plant waste processing system to compensate for the clean flush water which is added. Then valve 99 will be closed and valve 100 opened to blow air under pressure through cartridge 75 in order to effect dewatering. During this operation, solenoid 78 remains energized to retain the particulate waste material in matrix 18. The dewatering air will also be conducted to tank 103, from which it can be expelled via conduit 112. During the above operating steps, pump 89 can be in operation to remove, via siphon tube 33 and conduit 83, any liquid which may collect in the reservoir provided above cartridge plate portion 4. Pump 89 can be connected to deliver this liquid to tank 103. Thereafter, all valves may be closed and piston-cylinder assemblies 47 are actuated to lift plate 46, together with turret 23. Then, piston-cylinder assembly 49 is actuated to pivot turret 23 about the axis of conduit 24 into its second operating position, in which conduits 27 and 28 will be vertically aligned with conduits 9 and 8, respectively, conduit 24 remaining vertically aligned with conduit 10. Then piston-cylinder assemblies 47 are again operated to lower plate 46, together with turret 23, so that a sealed coupling is formed between conduits 27, 28 and 24, on the one hand, and conduits 9, 8 and 10, respectively, on the other hand. Thereafter, valves 90 and 91 are opened, all other valves remaining closed. As noted above, conduit 27 is constructed to form a seal for conduit 9. With solenoid 78 remaining energized, the selected encapsulating material, e.g. a resin-catalyst mixture, is pumped in via conduit 96, valve 91 and conduits 85, 28 and 8, while the air in cartridge 75 which is being displaced by the resin-catalyst mixture is permitted to escape via conduits 10, 24, 84 and 95 and valve 90, conduit 95 being connected to a controlled plant vent system. When the encapsulating material level in cartridge 75 reaches the level of valve 37, 38 in conduit 10, it forces valve stem and body 37 upwardly against the action of spring 40 until microswitch 42 is actuated, producing the control signal to halt the injection of the encapsulating material. At this time, the interior of the cartridge is completely filled with the encapsulating material. Then, valves 90 and 91 are closed, solenoid 78 is deenergized, and conveyor 74 is actuated to bring drum 76 directly below cartridge 75. Drum 76 can be brought below cartridge 75 at any time after the cartridge has been raised into the broken line position shown in FIG. 5. Thereafter, ram 80 is operated to lower cartridge 75 into drum 76. Thereafter, piston-cylinder assemblies 70 are actuated to move cams 32 downwardly and to then rotate the cams into their release position, after which ram 80 is operated to lift loader arms 81 together with the loading head and turret assembly. Assemblies 47 can be operated at any time after encapsulation to lift conduits 24, 27 and 28 away from conduits 8-10. Finally, the open end of drum 76 can be sealed at a subsequent station and the drum removed for final disposal. When the filling of cartridge 75 with encapsulating material has been completed and cartridge 75 has been placed into drum 76, the conduits supplying such material should be flushed to prevent plugging of the system with residual encapsulating material. Since this material is not radioactive, the associated lines and conduit 28 can be flushed into a further drum brought into position beneath cylinder 21 by conveyor 74. Ram 80 can be lowered and plate 46 can then be lowered to bring the outlet ends of conduits 24-28 to below the rim of the further drum and the lines can then be flushed by conducting a suitable solvent and entraining air through the lines which previously conducted the encapsulating material and through conduit 28. Cylinder 21 is then lifted and the further drum is then removed by conveyor 74 for sealing and disposal as non-radioactive waste or it can be handled with the drums containing radioactive waste, as required. In the illustrated system, in-line radiation detectors are mounted on the inlet and outlet conduits of the loading head and turret assembly to measure the decontamination factor of the cartridge. The radiation activity in the backflush slurry will be due primarily to insoluable corrosion products therein. When matrix 18 in cartridge 75 reaches its holding capacity, the outlet monitor will indicate a corresponding increase in radiation activity to produce a signal indicating that the cartridge is loaded. Then, the slurry delivery process can be halted, either automatically or by an operator, and the resin filling process can be initiated. The instrumention employed can be calibrated to indicate differential radiation activity rather than an absolute level thereof, if desired. The sealing of the top of the drum will normally be carried out at a location remote from the station shown in FIG. 5, the drum being brought to the sealing station by conveyor 74, and there being automatically sealed in a conventional manner. The encapsulating material can be of any suitable, officially approved type which is already known in the art. Since conduit 24 is only used to permit venting of air during the resin filling procedure, microswitch 42 will not come into contact with possibly corrosive liquid products. The greatest likelihood of liquid collecting in the reservoir above plate portion 4 will occur after the waste material loading, flush and dewatering steps at the moment when turret 23 is raised and the connections between conduits 25, 26 and 24 and conduits 9, 8 and 10, respectively, are broken. Therefore, it is particularly desirable for pump 89 to be in operation at this time, and until after turret 23 has again been lowered to couple conduits 27, 28 and 24 to conduits 9, 8 and 10 respectively, prior to start of encapsulating material injection. Once that injection operation has started, pump 89 can be turned off. It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended with the meaning and range of the appended claims.
042253900	description	DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a nuclear reactor 10 which includes one or more closed loop coolant circulating systems as is well known in the art. A connecting conduit 18 draws off predetermined amount of coolant, in this example light water, from the primary circulation system for chemical control purposes, such as during plant startup, load follow operations, shutdowns and/or boron removal. Briefly, if dilution of the coolant within the reactor is desired, makeup water is sent to the reactor coolant by opening a valve 12 to allow demineralized and deaerated water from the primary water storage tank 14 to enter the primary cooling system of the nuclear reactor 10. A preselected quantity of concentrated boric acid solution at a predetermined flow rate is added to the reactor coolant system. The apparatus shown in FIG. 1 is essentially the same as that shown and described in detail in the aforementioned copending application of Gramer et al although the mode of operation has been changed in accordance with this invention. Where dilution of boron ion concentration in the water within the reactor is desired, valves 12 and 16 are first closed. A predetermined amount of flow then is permitted to leave the reactor via conduit 18. This flow may be referred to as the letdown flow and passes through a letdown heat exchanger 20, a mixed bed demineralizer 22, and intermittently through cation beds 24; and is there purified in the normal manner. The water then flows via valve 26 and moderating heat exchanger 28 to a letdown chiller heat exchanger 30 where the water is cooled to, for example, 50.degree. F. The water which enters the ion exchangers 32 at this low temperature loses its content of boric acid which is stored on the ion exchangers. Ion exchangers 32 contain a temperature sensitive resin such as a styrene di-vinyl benzene polymer which absorb borate ions from the coolant and whose absorption capacity increases as the resin temperature decreases. Water with a very low concentration of boric acid leaves the ion exchangers and is sent via the moderating heat exchanger 28 back to a volume control tank 34 from which the usual charging system returns the water to the reactor 10. The control of this system is such that only one ion exchanger 32 is utilized at a given time. At the start of the dilution valves 36, 38 and 40 are closed. The boric acid concentration of the flow which passes through ion exchanger 32A via valve 35 is continuously read on a boron meter 42 of known construction. An increase of the extract concentration of ion exchanger 32A indicates that the resins within the exchanger 32A are saturated with boron. At that moment, the valve 35 is closed and the valve 36 is opened so that ion exchanger 32B is used for the next portion of boron storage. This process can be repeated until all the ion exchangers 32 are saturated. If desired, a throttle valve 44 may be closed and the entire letdown flow would pass through valve 26 and the maximum rate of dilution would be achieved. At the beginning of core life, the boric acid concentration of the primary coolant must be high. Thus, the required amount of dilution water for a given change in concentration is smaller near the beginning of core life than near the end of core life when the boron concentration within the reactor coolant is lower. Therefore, the maximum letdown flow for boron removal or coolant dilution purposes is only required near the end of core life. For this reason, throttle valve 44 is used to control the amount of flow which passes through the ion exchangers 32. A part of the letdown flow is then returned to the volume control tank without losing its boric acid content which means that the rate of dilution may be controlled by controlling the throttle valve 44. The amount of resin necessary in the ion exchange beds 32 depends upon the storage capacity of the resin, the volume of the primary system and the required change in concentration of the primary water. For given operating temperatures of the resin and a given size reactor, the storage capacity of the resin and the volume of the primary coolant are fixed quantities, the amount of resin is then only dependent upon the required change in concentration. The system described in this invention desirably is sized to store an amount of boron which corresponds to a change in concentration of the primary coolant required for load follow purposes. As will be explained, an evaporator recycle system may be utilized where greater changes are desired. When a higher concentrate of boric acid is desired to be added to the reactor, valves 12 and 16 are first closed. The letdown flow then follows the same path as in the case of dilution; explained in detail above. The water which enters the system via valve 26 is not cooled in the letdown heat exchanger 30 but is rather increased in temperature in a letdown reheat heat exchanger 46 to a temperature which is limited to the maximum allowable temperatures at which the resin can be used. The temperature of the flow which enters the ion exchangers 32 is controlled by controlling a throttle valve 48 such that hot water of about 300.degree. F. can pass through the shell side of the letdown reheat heat exchanger 46 and heat up the effluent, for example to 170.degree. F. A temperature indicating control 50 located downstream of the letdown reheat heat exchangers 46 controls valve 48 in throttling of the heating fluid to maintain the desired temperature of the heated influent to the ion exchangers 32. The water flowing through each ion exchanger 32 now takes up boron from the resin. The extraction of boron continues until the resin in the ion exchanger tanks 32 reaches a new equilibrium point at which no more boron is being removed. The boron meter 42 gives a continuous reading of the boric acid concentration of the flow which passes from each ion exchanger 32. A decrease in the extract concentration indicates that the resin is depleted and the letdown flow is then fed sequentially through the next resin bed 32B, 32C and 32D, etc. The boron enriched water which leaves the ion exchangers 32 is sent back to the primary coolant system via moderating heat exchanger 28 and volume control tank 34. As previously indicated, a major cost savings results from reducing the amount of effluent that must be reprocessed. As explained above, the effluent produced during load follow operations can be greatly reduced by the use of boron storage resin ion exchange system described. Another source of effluent requiring reprocessing in the prior art was that resulting from a removal of boron from the system, as for example, with the reduction in fissionable material caused by fuel burnup. In accordance with the present invention, in order to remove boron from the system, valve 44 is closed and the process operates initially as described under the dilution mode, the letdown flow is chilled in heat exchanger 30 and boron is removed therefrom in the ion exchangers 32A, 32B, 32C and 32D. After the resin beds 32A, 32B, 32C and 32D are sequentially saturated with boron, a valve 51 controlling the entry of fluid to volume control tank 34 is closed and valves 12 and 16 are opened. The system then operates as described above under the boron addition mode except that the effluent is sent to holdup tanks (not shown) in FIG. 1 and the water is pumped from the primary water storage tank 14 into the primary coolant system. After depletion of the resin of the boron from the resin beds 32, valves 16 and 12 are again closed and valve 51 is reopened. This process may be repeated until the required decrease in boric acid concentration in the primary coolant is achieved. The effluent which is sent to the holdup tanks 52 (see FIG. 2) initially causes a displacement of the cover gas therein. Initially the tanks are filled with nitrogen which is displaced by the entering fluid and is pumped by compressors to gas decay tanks (not shown). The fluid in the holdup tanks 52 is pumped to evaporator feed ion exchanger 54 where nitrogen, hydrogen and fission gases are removed therefrom. The fluid is then pumped to the boric acid evaporator package 56 where the evaporative process separates the boric acid from the primary water. This is a continuous batch operation which produces a high concentration of boric acid solution. Although one gas stripper 54 and one evaporator package 56 are shown connected in series, two gas stripper units and two evaporators are more often used, operating in parallel. Distillate from the evaporator flows continuously to monitor tanks 58 where samples are drawn and evaluated before the fluid is pumped to the primary water storage tank 14. The evaporator bottom collects boric acid solution which gradually increases in concentration during the process. The accumulated batch is then sent to concentrate holding tanks 60 where samples are also drawn to check the boric acid concentration. Following this, the fluid is pumped to boric acid tanks 62. In the case of boration, the flow of boric acid from the boric acid tanks 62 and water from the primary water storage tank 14 are sent to a boric acid mixing tank 64 where the primary coolant is blended to the proper concentration and then fed directly into the primary coolant. It should now be apparent that a combination of an ion exchange system which is utilized for normal load follow operations and an evaporative process which is utilized to remove boron for the system allows for substantial reduction in the size and cost of systems required for a boron chemical shim recycle system. By way of a general numerical example of the reductions possible with this system, in the presently sized nuclear reactor plants, a daily load reduction of 50% would produce about 50 system volumes of effluent per core life. An additional 10 system volumes per core life are produced during other operations such as plant startup, shutdown and compensation for core burnup reactivity effects. In the prior art, the 60 system volumes would have to be processed by a plurality of large evaporators. As can be seen with the process of this invention, a small evaporator can handle the entire boron reduction inasmuch as the normal load follow functions can be performed by the ion exchange system. It should further now be apparent that a sequential operation of the ion exchangers allow for a reduction in the size of this system and an increase in the efficiency of same.
	summary
	description	This application claims the benefit of U.S. Provisional Application No. 61/020,054, filed Jan. 9, 2008. Not Applicable 1. Field of Invention This invention relates to a digital rod position indication system for use in a nuclear power plant. More specifically, this invention relates to a high resolution digital rod position indication system having improved resolution compared to conventional rod position indication systems. 2. Description of the Related Art In a Pressurized Water Reactor (PWR), the power level of the reactor 10 is controlled by inserting and retracting the control rods 12, which for purposes of this application include the shutdown rods, into the reactor core 14. The control rods are moved by the Control Rod Drive Mechanisms (CRDM), which are electromechanical jacks that raise or lower the control rods in increments. The CRDM includes a lift coil DML, a moveable gripper coil DMM, and a stationary gripper coil DMS that are controlled by the Rod Control System (RCS) and a ferromagnetic drive rod that is coupled to the control rod and moves within the pressure housing 16. The drive rod includes a number of circumferential grooves at ⅝ inch intervals (“steps”) that define the range of movement for the control rod. A typical drive rod contains approximately 231 grooves, although this number may vary. The moveable gripper coil mechanically engages the grooves of the drive rod when energized and disengages from the drive rod when de-energized. Energizing the lift coil raises the moveable gripper coil (and the control rod if the moveable gripper coil is energized) by one step. Energizing the moveable gripper coil and de-energizing the lift coil moves the control rod down one step. Similarly, when energized, the stationary gripper coil engages the drive rod to maintain the position of the control rod and, when de-energized, disengages from the drive rod to allow the control rod to move. The RCS includes the logic cabinet and the power cabinet. The logic cabinet receives manual demand signals from an operator or automatic demand signals from Reactor Control and provides the command signals needed to operate the shutdown and control rods according to a predetermined schedule. The power cabinet provides the programmed dc current to the operating coils of the CRDM. Current PWR designs have no direct indication of the actual position of each control rod. Instead, step counters associated with the control rods are maintained by the RCS and rod position indication (RPI) systems to monitor the positions of the control rods within the reactor. The associated step counter is incremented or decremented when movement of a control rod is demanded and successful movement is verified. Because the step counter only reports the expected position of the control rod, certain conditions can result in the step counter failing and deviating from the actual position of the control rod. In certain situations where the actual position of the control rod is known, the step counter can be manually adjusted to reflect the actual position. However, if the actual position of the control rod is not known, a plant shutdown may be required so that the step counters to be initialized to zero while the control rods are at core bottom. The RPI systems derive the axial positions of the control rods by direct measurement of drive rod positions. Currently both analog rod position indication (ARPI) systems and digital rod position indication (DRPI) systems are in use in PWRs. The conventional DRPI systems have been in service for over 30 years in nuclear power stations worldwide and are currently being used as the basis for the rod position indication systems in the new Westinghouse AP1000 designs. A conventional DRPI system includes two coil stacks for each control rod and the associated DPRI electronics for processing the signals from the coil stacks. Each coil stack is an independent channels of coils placed over the pressure housing. Each channel includes 21 coils. The coils are interleaved and positioned at 3.75 inch intervals (6 steps). The DRPI electronics for each coil stack of each control rod are located in a pair of redundant data cabinets (Data Cabinets A and B). Although intended to provide independent verification of the control rod position, conventional DRPI systems are not accurate to fewer than 6 steps. The overall accuracy of a DRPI system is considered to be accurate within ±3.75 inches (6 steps) with both channels functioning and ±7.5 inches using a single channel (12 steps). In contrast to the conventional DRPI system, a conventional ARPI system determines the position based on the amplitude of the dc output voltage of an electrical coil stack linear variable differential transformer. The overall accuracy of a properly calibrated ARPI system is considered to be accurate within ±7.2 inches (12 steps). Neither conventional ARPI systems nor conventional DRPI systems are capable of determining the actual positions of the control rods. It should be noted that for purposes of this application, the phrase “control rod” is used generically to refer to a unit for which separate axial position information is maintained, such as a group of control rods physically connected in a cluster assembly. The number of control rods varies according to the plant design. For example, a typical four-loop PWR has 53 control rods. Each control rod requires its own sets of coils having one or more channels and the DRPI electronics associated with each channel. Thus, in a typical four-loop PWR, the entire DPRI system would include 53 coil stacks, each having two independent channels, and 106 DPRI electronics units. Further, in this application, the phrase “coil stack” is used generically to refer to the detector coils associated with each control rod and should be understood to include either or both channels of detector coils. Thus, a measurement across a coil stack contemplates the value across both channels combined and/or the value across a single channel. The failure of either or both of the RPI system and the step counter can result in a plant shutdown to resolve the problem. For example, if both the step counter and the conventional RPI system fail, no position information is available and a plant shutdown is required to re-initialize the step counter and synchronize the two systems. Similarly, if either the step counter or the conventional RPI system develops a problem causing the position information reported by the two systems to differ by more than the allowable difference, a plant shutdown for re-initialization of the step counter and synchronization of the two systems is required. The allowable difference is typically 12 steps based on the resolution of a DRPI system operating from a single coil stack. Unfortunately, aging and obsolescence issues have led to an increase in problems with conventional DRPI systems including analog card failures and coil cable connection problems that, in some cases, may result in unplanned reactor trips. These problems, along with plans for plant life extension, have prompted the industry to actively seek viable options to monitor the health and accuracy of the DRPI systems and/or to replace failing systems in order to ensure reliable plant operations for decades to come. Beyond the technical problems of the conventional DRPI systems, regulatory issues exist. Many existing PWRs are approaching the end of qualified life for several components of the conventional DRPI systems during the next decade and are actively seeking replacement options at this time. There has been a significant push in recent years for plants to replace aging analog systems with digital systems made from commercially-available off-the-shelf parts. Using readily-available commercial parts provide plants more options for replacement in the future. A high resolution digital rod position indication (high resolution DRPI) system having improved resolution is described in detail herein and illustrated in the accompanying figures. The high resolution DRPI system monitors the rod control cluster and provides an indication of the rod position with precision to a single step. In addition, the high resolution DRPI system is capable of producing a rod position output compatible with existing rod control systems. The improved resolution of the high resolution DRPI system allows the actual position of the control rods to be continuously monitored and eliminates the need for or reduces the frequency of offline re-initialization of the step counters. The high resolution DRPI system can be implemented as a complete system in a new plant design or a supplemental system that works in conjunction with portions of a conventional DRPI system to provide position measurements with improved resolution compared to the conventional DRPI. The high resolution DRPI system includes high resolution DRPI electronics that are connected to and monitor the electrical signals from the plurality of detector coils and the reference voltage. The high resolution DRPI electronics include a data acquisition unit in communication with an interface device. The high resolution DRPI data acquisition unit has a number of analog inputs equal to the number of coils in a single channel plus an additional input for the reference line. The electronic signals produced by each DRPI coil are sampled by high resolution DRPI data acquisition unit. The interface transmits the sampled data to the high resolution DRPI processing unit located outside containment. Analysis of actual measured data from obtained from the detector coils shows that each step clearly produces a measureable change in the RMS voltage. More specifically, the RMS voltage obtained using detector coil outputs shows a series of discrete steps that occur as a result of operation of the CRDM moving the drive rod one step at a time. Likewise, the dc voltage signal obtained from the sampled data of the detector coils shows a voltage fluctuation corresponding to each step of the control rod. The high resolution DRPI system captures and processes this information allowing an accurate determination of the actual position of the drive rod with single step precision, effectively improving the resolution of the position information 6 times when compared to conventional DRPI systems. A high resolution digital rod position indication (high resolution DRPI) system having improved resolution compared to conventional digital rod position indication (DRPI) systems is described in detail herein and illustrated in the accompanying figures. The high resolution DRPI system monitors the rod control cluster and provides an indication of the rod position with precision to a single step. In addition, the high resolution DRPI system is capable of producing a rod position output compatible with existing rod control systems. The improved resolution of the high resolution DRPI system allows the actual position of the control rods to be continuously monitored and eliminates the need for or reduces the frequency of offline re-initialization of the step counters. FIG. 1 is a block diagram of a high resolution DRPI system in a pressurized water reactor (PWR). A brief overview of the systems of a PWR that are relevant to the high resolution DRPI can be found in the description of the related art. The high resolution DRPI system can be implemented as a complete system in a new plant design or a supplemental system that works in conjunction with portions of a conventional DRPI system to provide position measurements with improved resolution compared to the conventional DRPI. In the illustrated embodiment, the high resolution DRPI system includes the high resolution DRPI electronics located inside containment and the high resolution DRPI processing unit located outside containment in the main control room. The high resolution DRPI electronics sample the electrical signals from the detector coils common to DRPI systems and transmit the sampled data to the high resolution DRPI processing unit. The high resolution DRPI processing unit evaluates the sampled data from the high resolution DRPI electronics to derive the positions of the control rods. The position information generated by the high resolution DRPI processing unit is displayed to the reactor operators via a user interface and may be used to verify the position information maintained by the step counters of the rod control system (RCS). FIG. 2 illustrates one embodiment of the high resolution DRPI system used to retrofit plants with existing conventional DRPI systems. The conventional DRPI system consists of two redundant components (Data Cabinets A and B) located inside the containment area and in communication with the detector coils of the coil stacks and mounted on the rod control housings above the reactor. In this embodiment, the high resolution DRPI electronics are connected to the data cabinets at a point between the input from the existing detector coils and the conventional DRPI electronics allowing the high resolution DRPI electronics to sample the DRPI coil currents and convert them into digital signals. The digital signal is then transmitted to the high resolution DRPI processing unit in the main control room. FIG. 3 is a diagram of one embodiment of the high resolution DRPI electronics used in the retrofit application of FIG. 2. In this embodiment, the high resolution DRPI electronics are connected to the test points PT1-PTn, PTREF in the data cabinets of the conventional DRPI. The test points PT1-PTn, PTREF provide access to the electrical signals from the plurality of detector coils C1-Cn and the reference voltage VREF. The high resolution DRPI electronics include a data acquisition unit in communication with an interface device. Each control rod has one high resolution DRPI electronics unit for each independent channel of the coil stack associated with the control rod. For example, a PWR having 53 control rods monitored by redundant DPRI systems (53 coil stacks with two independent channels) would have 106 ADPRI electronics (53 per data cabinet). In one embodiment, each high resolution DRPI data acquisition unit has a number of analog inputs equal to the number of coils in a single channel plus an additional input for the reference line. The electronic signals produced by each DRPI coil are sampled by high resolution DRPI data acquisition unit. The interface unit is used to transmit the sampled data to the high resolution DRPI processing unit located outside containment. The interface unit is selected to have sufficient data transmission speeds to send the sampled data to the high resolution DRPI processing unit in real time. By way of example, one suitable device for performing the functions of the high resolution DRPI data acquisition unit and the interface unit is the CompactRIO remote high speed interface system produced by National Instruments Corporation, which includes swappable I/O modules connected to an FPGA for acquiring various types of signals including the voltage and current signals used by the high resolution DRPI system and a high speed interface allowing an external computer to communicate with the FPGA at data rates up to 50 MB/s. One skilled in the art will recognize that the general specifications for the high resolution DRPI electronics are not intended to be limiting and that deviations intended to acquire sufficient data containing information from which the positions of the control rods to a single step can be derived are considered to remain with the scope and spirit of the appended claims. To better appreciate the high resolution DRPI system, a brief discussion of rod movement and control and of the operation of conventional DRPI systems is appropriate. FIG. 4 relates the electrical signals produced by the detector coils to rod movement and the output of a conventional DPRI system. In a conventional DPRI system, the detector coils C1-Cn are excited by a low-voltage ac source VREF generating a magnetic field around each of the detector coils. While undisturbed, the output voltage of each DRPI coil remains steady. As the drive rod approaches a DRPI coil, the magnetic field varies and the voltage induced in the DRPI coil changes. The output voltage of a DRPI coil is greatest when the drive rod is not interrupting the magnetic field, i.e., when the drive rod does not pass through the DRPI coil. As the drive rod passes through the DRPI coil, it interrupts the magnetic field and reduces the induced voltage. Thus, the output voltage of a DRPI coil is minimized when the drive rod passes through that DRPI coil. The outputs of neighboring detector coils are fed into a bank of differential amplifiers and logic components to produce the output signals of the conventional DRPI electronics. The changes in the DPRI electronics output signals indicate the movement of the drive rod into or out of a particular coil giving the approximate positions the control rods. As discussed in the background section, the position information provided by the conventional DRPI system is only accurate, at best, to within 6 steps. In other words, the precision of a conventional DRPI system is limited by the number of detector coils and their spacing. The output of the conventional DRPI electronics are shown in FIG. 3 by signals VD1, representing the voltage differential between the first coil C1 and the second coil C2, and VD2, representing the voltage differential between the second coil C2 and the third coil C3, as a control rod 12 is withdrawn from the reactor core 14. For reference, the first coil C1 is the bottom coil in the coil stack and the highest numbered coil Cn is the top coil in the coil stack. As the control rod is withdrawn, the drive rod moves upward through the coil stack. Initially, the drive rod does not pass through any of the detector coils and the output voltage of all of the detector coils is maximized. At this point, all of the outputs of the conventional DRPI electronics are logical zeros. As the drive rod passes through the first coil C1, the output voltage of the first coil C1 falls while the output voltage of the second coil C2 remains high. The resulting voltage differential produces a logical one at the first conventional DRPI electronics output D1. The drive rod continues to rise and passes through the second coil C2 causing the output voltage of the second coil C2 to fall. At this point, the output voltages of the first coil C1 and the second coil C2 are both low. Because the voltage differential between the first coil C1 and the second coil C2 is no longer large, the first conventional DRPI electronics output D1 once again becomes a logical zero. However, a significant voltage differential exists between the second coil C2 and the third coil C3 because the voltage of the second coil C2 is low while the voltage of the third coil C3 remains high. This causes the second conventional DRPI electronics output D2 to produce a logical one. Thus, each time the drive rod moves into or out of a DRPI coil, the resulting difference in voltage from the neighbor coil allows the most recently affected coil to be identified, thereby allowing the approximate position of the control rod to be determined with a resolution corresponding to the number of active detector coils. The high resolution DRPI system described herein provides higher resolution position information than is available with conventional DRPI systems. A prototype of the high resolution DPRI system was tested at the Farley nuclear power plant using a single channel of detector coils for one control rod when withdrawing the control rod 226 steps out of core, inserting the control rod 226 steps into the core, and during rod drop testing. FIGS. 5-8 show portions of the data obtained during testing of the prototype. FIG. 5 substitutes a portion of the idealized signal shown in FIG. 4 with a root-mean-square (RMS) voltage obtained from the sampled data. FIG. 5 shows that every one of the 12 steps clearly produces a measureable change in the RMS voltage. More specifically, the RMS voltage obtained using the detector coil output shows a series of discrete steps that occur as a result of operation of the CRDM moving the drive rod one step at a time. In other words, the detector coil output produces a substantially constant RMS voltage 18a while the position of the control rod remains stationary. Each time the control rod moves, fluctuations 20 in the RMS voltage occur including an abrupt, discrete, and measurable change 22 in the amplitude of the RMS voltage. The amplitude change is followed by another period where the RMS voltage 18b remains substantially constant until the control rod moves again. These amplitude changes/fluctuations provide an identifiable characteristic introduced by and corresponding to movement of the control rod. FIG. 6 shows the RMS voltage change corresponding to a single step to illustrate the signal characteristics associated with movement of the control rod in greater detail. FIG. 7 relates the RMS voltage signal of FIG. 5 and a dc voltage signal obtained from the detector coil output to the movement of the drive rod through one coil. As with the RMS voltage signal, the dc voltage signal shows a voltage fluctuation corresponding to each step of the control rod. FIG. 8 shows the fluctuation 24 of the dc voltage signal for a single step of the control rod to more clearly illustrate the identifiable characteristics identifying movement of the control rod, namely a brief pulse or swing 26 from the dc voltage baseline having a minimum peak-to-peak voltage. Unfortunately, this information is lost by conventional DRPI electronics during the differential analysis. However, the high resolution DRPI system disclosed herein bypasses the conventional DRPI system and captures the raw DRPI coil outputs thereby preserving this information. The high resolution DRPI system captures and processes this information allowing an accurate determination of the actual position of the drive rod with single step precision, effectively improving the resolution of the position information 6 times when compared to conventional DRPI systems. In one embodiment, the actual positions of the control rods are derived by accumulating the occurrences of the identifiable characteristics for each control rod starting from a known position. A count is added when a control rod moves upward, i.e., the detector coil output voltage increases, and a count is subtracted when a control rod moves downward, i.e., the coil output voltage decreases thereby allowing an accurate position determination with precision of a single step. In an alternate embodiment, the high resolution DRPI system is calibrated by moving the control rods through their entire range of motion and associating the output voltages of the coils with a rod position value. The calibration process may be repeated and the results averaged, if necessary, to create an accurate set of reference voltages. In operation, the processing unit compares the measured outputs of the detector coils with the set of reference voltages to accurately identify the positions of the control rods thereby allowing an accurate position determination with the precision of a single step. While time-domain analysis of the RMS voltage and the dc voltage signals derived from the DRPI coil outputs has been disclosed, the information relating to the movement of the drive rod may be discerned through analysis of other derived signals and/or analysis in other domains, such as the frequency domain. FIG. 9 illustrates an alternate embodiment of the high resolution DRPI system that completely replaces conventional DRPI systems. In this embodiment, the high resolution DRPI electronics are connected directly to the DPRI coils and communicate directly with the high resolution DRPI processing unit located outside containment. The high resolution DRPI system may also replace a conventional ARPI system; however, as previously discussed, the detector of a conventional ARPI system differs from the DRPI coils used for drive rod presence sensing. Accordingly, when replacing a conventional ARPI system, the high resolution DRPI necessarily includes the DRPI detection coils. FIG. 10 illustrates an alternate embodiment of the high resolution DRPI system where some or all of the processing functions occur in the high resolution DRPI electronics. In the embodiment of FIG. 10, the high resolution DRPI electronics includes a processing unit receiving data from the high resolution DRPI data acquisition unit. In one embodiment, the processing unit in the high resolution DRPI electronics calculates the position information containment thereby reducing the amount of data that must be transferred to the main control system. In another embodiment, the processing unit in the high resolution DRPI electronics assumes all of the processing functions thereby eliminating the need for the high resolution DRPI system to provide a separate processing unit in the main control system. In this embodiment, the high resolution DRPI electronics communicate directly with other control systems in the PWR, such as the reactor control of the main control system or the logic cabinet in the rod drive system, or simply communicates with the user interface. For example, in a system using the CompactRIO previously described, the FPGA calculates axial position information. One skilled in the art will appreciate that the processing units described herein can be implemented using any number of logic components including controllers and processors without departing from the scope and spirit of the present invention. From the foregoing description, it will be recognized by those skilled in the art that a high resolution DRPI system having improved resolution (i.e., single step precision) has been provided. The high resolution DRPI system provides accurate rod position information resolved to a single step thereby avoiding the numerous operation problems that occur when step counters fail and rod position is unknown. While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.
	claims	1. A power cycle test method for testing an electronic equipment, the method comprising:providing a hardware configuration consisting of a host computer, a single chip processor, a relay, and a power supply;predefining a total test count, and resetting a current test count;updating the current test count by incrementing the current test count by a value;checking whether the electronic equipment passes an alternating current (AC) test under a first AC control signal, the first AC control signal being transmitted to the single chip processor;powering off the electronic equipment under a first direct current (DC) control signal if the electronic equipment passes the AC test, the first DC control signal being transmitted to the single chip processor;checking whether the electronic equipment passes a DC test under a second DC control signal, the second DC control signal being transmitted to the single chip processor;checking whether the electronic equipment passes a reboot test under a reboot control signal if the electronic equipment passes the DC test, the reboot control signal being transmitted to the single chip processor;powering off the electronic equipment under a second AC control signal if the electronic equipment passes the reboot test, the second AC control signal being transmitted to the single chip processor;determining whether the current test count is equal to the total test count; anddisplaying a result message if the current test count is equal to the total test count. 2. The method as claimed in claim 1, wherein said AC control signals are used for enabling/disabling the relay to correspondingly power on/power off the electronic equipment. 3. The method as claimed in claim 1, wherein said DC control signals are used for actuating/activating a power switch of the electronic equipment to correspondingly power on/power off the electronic equipment. 4. The method as claimed in claim 1, wherein the reboot control signal is used for actuating a reboot switch of the electronic equipment to reboot the electronic equipment. 5. The method as claimed in claim 1, wherein each of said checking steps is achieved by checking whether a test result is received. 6. The method as claimed in claim 5, wherein the test result is a bootup success message of the electronic equipment. 7. The method as claimed in claim 1, further comprising the steps of:displaying the current test count and an error message that indicates the electronic equipment is an unqualified product, if the electronic equipment does not pass the AC test, the DC test, or the reboot test. 8. The method as claimed in claim 1, further comprising the steps of:returning to the step of updating the current test count by incrementing the current test count by a value, if the current test count does not equal to the total test count. 9. The method as claimed in claim 1, wherein the power supply is an AC power supply. 10. The method as claimed in claim 1, wherein the single chip processor is a microcontroller unit (MCU). 11. The method as claimed in claim 1, wherein the electronic equipment is selected form a group consisting of a personal computer, a notebook computer, a server, and a television. 12. A power cycle test method for testing an electronic equipment, the method comprising:configuring a total test count and a current test count;updating the current test count by incrementing the current test count by a value;utilizing a corresponding AC control signal, a corresponding DC control signal, and a reboot control signal to control the electronic equipment in sequence;checking whether the electronic equipment is in a workable condition when the electronic equipment is respectively controlled under said control signals;repeating said updating step, said utilizing step and said checking step until the current test count is equal to the total test count; andgenerating a result message if the current test count is equal to the total test count. 13. The method as claimed in claim 12, wherein said creating step, utilizing step, checking step, and generating step are executed by a hardware configuration consisting of a host computer, a single chip processor, a relay, and a power supply. 14. The method as claimed in claim 12, wherein the result message indicates the electronic equipment is a qualified product.
	description	The present invention relates to a process for the manufacture of a dense material from at least two powders, each containing at least uranium dioxide UO2, obtained through different synthesis routes, said process including the intermediate step of manufacturing at least one particulate material having outstanding compressibility and sinterability properties. After such a process a dense material is obtained having, in particular, a constant density whatever the starting conditions, such as the degree of agglomeration and aggregation of the powders used, and whatever the shaping stress applied to the intermediate particulate material during its compaction as it is prepared for a final sintering step. Specifically, the invention applies to the use of said dense material for manufacturing a nuclear fuel in the form of pellets or tablets or other shapes. Oxide powders, in particular uranium oxide powders (such as uranium dioxide) used in the manufacture of fuel elements for nuclear reactors, generally exist in the form of crystallites with an average diameter ranging from 0.08 to 0.5 μm. These crystallites are more or less strongly bound together to form aggregates, which in turn are more or less strongly bound together to form agglomerates. Generally, the average diameter of the aggregates ranges from a few micrometers to a few tens of micrometers, for example from 2 to 60 μm, and the average diameter of the agglomerates ranges from a few micrometers to a few hundreds of micrometers, for example from 2 to 700 μm. In order to form a nuclear fuel into a pellet or any other shape from such oxide powders, several manufacturing steps are generally required, namely the following consecutive steps: i) An oxide powder is introduced into a mould or pressing die. Generally, the powder has to fill the entire volume which is accessible to it within the mould, thus making it possible afterwards to obtain a compact and sound material (free of blemishes and/or crack(s) that may or may not show up on the surface) with minimum porosity. This ability of a powder to completely fill a mould is referred to as flowability. It varies widely from one powder to another. In order to obtain sufficient flowability, it may be required to pre-process the powder (for example by means of a granulating process, such as an atomization or mechanical granulation process), ii) A shaping stress is then applied to the powder contained in the mould, for example by cold uniaxial pressing, in order to compact the powder. For nuclear oxide powders, this stress generally ranges from 200 to 600 MPa. At the end of this compaction step, a body of compacted material, or a so-called green compact, made of nuclear fuel, is obtained. Generally, this body has the form of a pellet, but any other shape is possible. The compact has enough cohesion to be handled during the later stages of nuclear fuel manufacturing, in the form of pellets or tablets or other shapes. The compressibility of the powder, which can be measured, is a curve representing the change in density (in g/cm3) of the dense material versus the applied stress (in MPa). Compressibility is thus a relative concept that depends on the operating conditions, in particular if lubricant is added to the powder or if the mould is lubricated with a lubricant spray, for example before each compaction. Two powders may be compared in terms of their compressibility, all things being equal. In this respect, the NF EN 725-10 standard can be referred to. iii) Then, the density and cohesion of the above obtained green compact is increased by applying at least one sintering cycle in which the pellet (or any other shape) generally undergoes a change in temperature and/or pressure with time, as known to those skilled in the art. Of course, other parameters may influence the sintering cycle, for instance the atmosphere, the presence of impurities, and the like. As a result of this sintering cycle, a sintered body, made of a dense material, is obtained and has a larger density than that of the green compact. For oxides intended to be used in the nuclear field, the sintering cycle is generally as follows: first the temperature is raised to the sintering temperature, generally around 1600° C., and this sintering temperature is then maintained, generally for a few hours, and more often four hours. The sinterability of a powder represents the change in density of the sintered body as a function of the green compact's density. Therefore, sinterability is a relative concept which depends on the operating conditions. Two powders may be compared in terms of their sinterability, all things being equal. In this respect, the B42-011 standard can be referred to. iv) Finally, this sintered body still needs to be provided with its appropriate dimensions so that it may be used as a pellet (or any other shape) of nuclear fuel. To this end, it is generally necessary to machine the sintered body to a standard size, which generally consists in removing some material to provide the pellet (or any other shape) of nuclear fuel with the appropriate shape and size to be used in a nuclear reactor. Deviations from the standard size are generally caused, for a pellet, which is the most common form used, by insufficient control of the average diameter with respect to the specified range and by a deviation from cylindricality due to the stress gradient generated in the green compact during uniaxial pressing. From patent application FR 2,861,888 a process for the manufacture of nuclear fuel pellets is known, which consists in preparing a particulate material having given properties from a uranium dioxide powder. It is this particulate material which is then subjected to the above-mentioned manufacturing steps (i) to (iii). The technical problem to be solved by the invention disclosed in this previous patent application was to obtain a particulate material having the properties of flowability and bulk density required for its introduction into the mould in step (i), while avoiding the numerous and complex operations that had to be carried out for that purpose, as previously known in the art. To this end, this patent application proposes to introduce the powder of uranium dioxide intended to enter the composition of the nuclear fuel into a vessel containing movable compression members, and this vessel is then shaken in order to form the desired particulate material. Only one uranium dioxide UO2 powder (main component of the nuclear fuel) is used, which uranium dioxide UO2 powder is derived from a process for the conversion of uranium hexafluoride. One or more additives, such as other oxides or pore forming substances are sometimes added to said powder. Patent application FR 2,861,888 mainly relates to a uranium dioxide powder UO2 produced through a process of the “dry route” type. These “dry route” processes are generally those in which the powder results from a conversion of the uranium hexafluoride (UF6) into UO2 by solid-gas reactions. “Wet route” processes, on the other hand, are generally those in which the powder results from a conversion of UF6 or uranium nitrate through liquid-liquid and liquid-solid reactions. For criticality and waste treatment management reasons, the industry generally prefers to manufacture the powders using a “dry route” process. The object of this patent application was only to solve the problems relating to the compaction of a particulate material provided by a single uranium dioxide powder, mainly obtained by means of a “dry route” process. The problems usually encountered during the green compact sintering step (iii) are in no way addressed in this patent application. However, the sinterability of a powder is problematic for uranium dioxide powders, in particular for those resulting from <<wet route>> processes, in particular because of their sinterability characteristics, which are inferior to those of powders produced by <<dry route>> processes, although their characteristics of density and flowability are superior. This is because, in addition to the fact that this sinterability depends on the size and shape of the powder crystallites, the degree of aggregation and/or agglomeration of the crystallites also has a strong influence. As a consequence, after sintering, the densities of the sintered bodies whose corresponding green compact had the same density before sintering but were prepared from two powders containing crystallites of the same size and same shape, can vary widely if the states of agglomeration and aggregation among these powders are different, for example because they were obtained through two different synthesis routes. This may be the case when a process is of the wet route type and the other process is of the dry route type; or when both processes, although being of the same “wet” or “dry” route type, are nevertheless different in their operating procedure. Lastly, it should be noted that, in general, the sinterability of powders is strongly related to operating parameters such as the value of the shaping stress applied to the particulate material during the compaction step. In practice, this variability in the sinterabilities of the powders has many disadvantages, namely: a) the non-reproducibility of the dimensions of the sintered body which makes it necessary to re-grind it in order to provide it with its final dimensional characteristics, thus strongly lengthening and increasing the complexity of the process for manufacturing a nuclear fuel pellet (or any other shape) ready for use. On the other hand, this re-grinding operation implies the loss of part of the useful fuel material, which has just been manufactured using a difficult method. Finally, this operation is hazardous since it produces extremely fine actinide oxide dusts, which can present health risks due to their toxicity (such as a PuO2 powder) and radioactivity; b) the disparity in sintering behaviours between powders having widely variable states of agglomeration and aggregation. This disparity requires continual adjustment of the shaping and/or sintering parameters. Therefore, there exists a strong need for new manufacturing processes of nuclear fuel, in the form of pellets or tablets or other shapes, to solve the problems and remedy the disadvantages of prior art techniques. Accordingly, one of the objects of the present invention is to provide a process for the manufacture of a dense material via the manufacture of a particulate material, from at least two powders each containing uranium dioxide UO2, so that the dense material has the same sinterability whatever the state of agglomeration and aggregation exhibited by the powders, and also has a sinterability which has a very small dependence on the density of the green compacts (that is, on the shaping stress applied to the particulate material originating from the powders). The invention relates to a process for the manufacture of a dense material containing uranium dioxide UO2, said process comprising the consecutive steps of: a) introducing at least two powders each comprising uranium dioxide UO2 into a vibrating grinder, wherein at least two powders are provided by two different synthesis routes and each powder has a specific surface area close to that of any other uranium-dioxide containing powder introduced into said grinder; b) shaking said powders by means of said vibrating grinder so as to form a particulate material, the grinding intensity being sufficient to break up the agglomerates and the aggregates in the powders without at the same time breaking up the crystallites in the powders, and the grinding energy provided to the powders being such that substantially all of the agglomerates and aggregates are destroyed; c) introducing said particulate material into a mould; d) applying a shaping stress to said particulate material, generally from 200 to 1200 MPa, preferably from 200 to 1000 MPa, more preferably from 200 to 600 MPa, and still more preferably from 300 to 500 MPa, in order to obtain a compacted material; e) carrying out the sintering of said compacted material so as to obtain the dense material. According to the present invention, by “particulate material” is meant a material containing the crystallites of said powders having a reduced degree of agglomeration or aggregation compared to that of each of the original powders, whereas the size of the crystallites has practically not changed. According to the invention, by “dense material” is generally meant a material obtained through a densification operation such as sintering. By “compacted material” is meant a material obtained through a compaction operation. Further according to the invention, by “similar specific surface area” is meant that a specific surface area does not differ from any other specific surface area by more than 10 m2/g, preferably by 2 to 5 m2/g, and more preferably by 2 to 3 m2/g. The measurement of the grinding energy applied to the powders is very delicate, but is directly correlated, for a given grinding intensity, to grinding duration. Also, measuring the agglomerates is generally carried out by dry sieving or laser granulometry, provided this analysis does not lead to their destruction. Moreover, the size and shape of the aggregates can be partially estimated by observing them with a scanning electron microscope. Finally, to date, there is no reliable way of quantifying the degree of aggregation. This is the reason for which the efficiency of step b) of the process according to the invention is measured in practice in an indirect way, by measuring the parameters of the particulate material provided by step b), as will be explained thereafter. Practically, the shaking of step b) is generally carried out over at least a given minimum duration so as to form a particulate material having a substantially constant sinterability, the compressibility and sinterability of said particulate material having moreover substantially given values, independent from the amount of agglomerates and/or aggregates contained in each of said powders. The minimum given duration is thus generally the duration which, as the Applicant has surprisingly observed for a given grinding intensity, is necessary to obtain the advantageous properties of the particulate material according to the invention. It is directly correlated to a given minimum grinding energy. The sinterability “is given” in the sense that, for a powder of a given specific surface area, it has a determined or specific value, which is observed experimentally. Beyond this given duration, the sinterability of the particulate material is substantially constant, and the compressibility continues to increase. The compressibility is “given” in the sense that, for a powder of a given specific surface area, it has a determined or specific value or a similar or close value, which is in general observed experimentally. The grinding energy, i.e. in practice the grinding duration for a given grinding intensity, generally reaches a maximum value beyond which compressibility has a given constant value and the density of the compacted material does not change any more. This maximum value is generally associated with the maximum compactness ratio of the density of the compacted material to the theoretical density of the considered compound, which is 0.72 if the crystallites are considered, as a first approximation, to be spheres. The given value of compressibility and the given value of sinterability depend on parameters that are specific to the characteristics of crystallites (size, shape, size distribution) and thus, indirectly, to the specific surface area of the powders, but in a surprising and advantageous way, do not depend on the quantity of aggregates and/or agglomerates in the powder. The relative amounts of powders used in step a) are variable. For example, in the case of two powders and when one powder pollutes, as will be explained further, the other powder, the “pollutant” powder is generally present with a ratio of 0.1 to 1% by weight, relative to the total weight of these two powders. In the case of a first powder resulting from a <<dry route>> process and a second powder resulting from a <<wet route>> process, the first powder is in a ratio ranging from 10 to 50% by weight relative to the total weight of the two powders. According to the invention, the powders, each of which comprises uranium dioxide UO2, may have been introduced into the grinder simultaneously, for example as a mixture, or consecutively, by introducing at least one powder during step a) and then later introducing at least one other powder during step b). One of the fundamental facts from which the invention derives is the surprising discovery of the properties of the particulate materials containing uranium dioxide UO2 after the powders have been shaken by the vibrating grinder with at least a given minimum grinding energy, i.e. in practice, for at least a given minimum duration. More specifically, above a given minimum grinding energy, i.e., in practice, above a given minimum shaking period under a given grinding intensity, two surprising properties of the particulate material obtained were found: i) the sinterability of this particulate material levels off, whatever the duration of the shaking (and thus, whatever the grinding energy) to which it was subjected, and ii) the value of this sinterability is “universal”, in the sense that it is in agreement with a value common to particulate materials derived from any one of the powders which, although having similar specific surface areas, did however have some different or even strongly dissimilar physical characteristics, for instance the agglomeration and aggregation degrees of the crystallites in these powders. Thus, in particular, the process according to this invention makes it possible to reduce the differences in sinterability between at least two uranium dioxide UO2 powders, which, in spite of their similar specific surface areas, have disparate degrees of crystallite agglomeration and aggregation. This unexpected behaviour of the powders subjected to the process of the invention and the way it is obtained were never disclosed before. These behaviours are illustrated in FIGS. 4 and 5 explained hereinbelow. This behaviour of the powders has several significant industrial advantages. Specifically, during the manufacture of nuclear fuel, whether in the form of pellets or tablets or other shapes, a powder, before a compaction step, is subjected to various manipulations, thereby implying transfers between two consecutive operations. The powder transfer and/or preparation equipment, which generally comprises containers or pneumatic means or conveyor belts, may then retain a more or less significant amount of powder. However, the nuclear fuel manufacturer often resorts to several providers or types of powder (for example, a powder obtained through a “dry route” process and a powder obtained through a “wet route process”). Thus, the powders used, although they are chemically identical, nevertheless originate from different sources. These different sources most often result in a wide variability of the aggregation and agglomeration state of the crystallites constituting such powders, and therefore, in widely variable compressibility and sinterability properties of said powders. In order for the dense material to have nevertheless constant characteristics in terms of dimensions and density, it is generally necessary: i) either to adapt the operating conditions of the powder manufacturing process for each powder, which may prove to be complex and expensive, since it may be difficult to simultaneously estimate not only the degree of pollution of one powder by another powder, but also the changes in the physical parameters of a mixture of at least two powders thus obtained; ii) or to avoid any mixing between two powders that are to be used consecutively, which implies the requirement to rinse the equipment that may cause retention. By cancelling the differences in agglomeration and aggregation between at least two powders using the process according to the invention, these two powders being for example in a mixture resulting from the pollution of a first powder by a second powder, it is therefore possible to use, indifferently but in the same installation, several powders of comparable nature without having to worry about unintentional mixture of a new powder to an old powder, which might have been made by a different process and/or which would have remained in the installation due to retention. This obviously leads to a significant increase in productivity. Thus the present invention is particularly beneficial for the manufacture of nuclear fuels, in the form of pellets or tablets or other shapes, under flexible, reproducible and independent operating conditions. These numerous advantages open the way to standardization when it comes to the industrial implementation of the process for sintering nuclear fuel powders. As for the vibrating grinder and the movable bodies that it contains and are used in the process according the invention, these are of the same kind as, or even identical to those employed in patent application FR 2,861,888. Such a vibrating grinder, according to the present invention, is generally a device comprising a vessel including the compression and mixture means, which are movable bodies, wherein shaking the vessel is carried out in such a way that the powder it contains moves within the vessel's volume along three non-coplanar axes, so that said powder is compressed between the movable bodies themselves, and between the movable bodies and the walls of the vessel until forming a particulate material of increased density as compared to the powder. It should be noted that one skilled in the art may use a wide range of grinding intensities and grinding energies that may be provided by the vibrating grinder. In all cases, the vibrating grinder must permit the breaking up of the agglomerates and aggregates rather than the grinding of crystallites. The grinding energy generated by the vibrating grinder used according to the present invention can be modified, in particular, by changing the unbalance masses and the angular distance between the upper and lower unbalances, increasing the mass of the media, or changing their shape or their nature, or modifying the amount of powder. According to a preferred aspect of this invention, at least one powder is obtained by a synthesis process of the “wet route” type, and at least one other powder is obtained by a synthesis process of the “dry route” type. According to one embodiment of the invention, at least one of the powders contains at least one oxide chosen from the group consisting of uranium oxide U3O8, uranium oxide U3O7, plutonium oxide PuO2 and thorium oxide ThO2. This oxide may also be added to said powders before and/or while performing the manufacturing process of the invention (steps a) to c)). For example, it is possible within the framework of the invention, to directly add such an oxide as a powder in the grinder. When the powders contain plutonium dioxide PuO2, a fuel of the MOX (“Mixed Oxide”) type can then be advantageously made. According to a preferred aspect of the present invention, at least one of the powders contains at least one additive selected from among gadolinium oxide Gd2O3, erbium oxide Er2O3, a pore-forming substance, such as, for example, ammonium oxalate or azodicarbonamide, a lubricant, such as zinc stearate or calcium stearate, and a sintering promoter, such as chromium oxide. More generally, this additive is most often comprised of at least one neutron absorbing or moderating substance for the control of nuclear reactors or at least one substance used in the manufacturing process (such as the lubricant), or for controlling the density (such as the pore-forming substance) and microstructure (such as the sintering promoter used in the sintering of the nuclear fuel, which, for example, is formed into a pellet). This additive can be added to said powders before and/or while performing the manufacturing process of the invention (steps a) to c)). According to a preferred aspect of the present invention, the shaking operation of said grinder is continued in order to increase the compressibility of the particulate material up to a given value, while sinterability remains substantially constant. This is because, as will be illustrated in the following examples, one of the distinctive features of the process of the present invention is that, even if the sinterability of said particulate material has reached, at a given minimum grinding energy, i.e., in practice, at the end of a given minimum shaking period, an optimum value which may no longer vary, it is nevertheless still possible, when needed, to adjust its compressibility by continuing to shake this material in step b) of the process of the present invention. Thus, in an embodiment of the present invention, the shaking of step b) is carried out by said grinder so as to increase the compressibility of the particulate material up to a given, substantially constant value, while sinterability remains substantially constant. It is yet another goal of the present invention to provide a product obtained by the process according to the present invention. In all figures, each plotted point is generally an average of at least six exactly identical samples. FIG. 1 illustrates, for various shaking durations according to step b) of the process of the present invention, the change in sinterability of a compacted material (green compact) containing the particulate material obtained according to the present invention from a powder of uranium dioxide UO2. This figure will allow one skilled in the art to determine the minimum given duration (for a given grinding intensity), beyond which the particulate material of the present invention forms on uranium dioxide UO2 powders of similar nature, that is, although these powders have specific surface areas similar to one another, their crystallites have dissimilar degrees of agglomeration and aggregation. FIGS. 2 and 3 illustrate the compressibility (change in density of a compacted material (green compact) as a function of the various shaping stress values applied to make this compacted material), respectively, for different powders and for the particulate materials obtained from each of these powders according to the present invention. FIGS. 4 and 5 illustrate the sinterability (change in density of a dense material (sintered body) as a function of the density of the corresponding compacted material (green compact) respectively, for different powders and for the different particulate materials obtained from the same powders according to the present invention. FIGS. 6 and 7 illustrate the change in volume shrinkage of the dense materials (sintered bodies) as a function of the density of the corresponding green compacts containing, respectively, at least one of the powders and one of the particulate materials obtained according to the present invention from the same powders. FIGS. 8 and 9 illustrate compressibility for two powders and for the mixture of these two powders and compressibility for the particulate materials obtained from each of these two powders and from this mixture, respectively, according to the present invention. FIGS. 10 and 11 illustrate sinterability for two powders and for the mixture of these two powders, and sinterability for the particulate materials obtained from each of these two powders and from this mixture, respectively, according to the present invention. The following illustrative examples are not intended to limit the scope of the invention in any way. The invention will be better understood from the following examples, which illustrate the process for manufacturing a dense material using the process for manufacturing a particulate material. The examples which follow are in all respects in accordance with the process of the present invention, in particular when they are carried out using only one powder at a time, rather than at least two, since it will be clear to one skilled in the art that each of these powders exhibits the compressibility and sinterability properties obtained according to the present invention, even in the presence of at least one other powder, as is the case in the process of the present invention wherein at least two powders are considered. This is also demonstrated in other examples relating to a mixture of two powders obtained by two different synthesis processes. In all of the following embodiments, the preparation, shaping and sintering operations were carried out under the same operating conditions for all powders (or mixtures of powders), and for all particulate materials (or mixtures of particulate materials) obtained from the powders according to the present invention. These examples were carried out on each of the uranium dioxide UO2 powders (or powder mixture) that were synthesized by means of a “wet route” process (powders VH1, VH2 and VH3) (each of these powders being synthesized by a so-called ADU process (Ammonium Di Uranate of formula U2O7(NH4)2) as explained, for example, in U.S. Pat. No. 6,235,223, but each powder originating from three different installations, each with different manufacturing parameters, thus explaining their different characteristics), and a “dry route” process (powder VS1). Powders VH1, VH2, VH3, and VS1 have similar specific surface areas, of 3.8 m2/g; 3.0 m2/g; 3.3 m2/g and 2.1 m2/g, respectively. The particulate materials obtained according to the present invention from powders VH1, VH2, VH3, and VS1 have specific surface areas of 4.2 m2/g; 3.7 m2/g; 4.2 m2/g and 2.6 m2/g, respectively. The slight increase in the observed specific surface area, from the powder state to the state of particulate materials derived from the powders, is generally due to the appearance of surfaces resulting from the breaking up of the aggregates and agglomerates. This is also the case when going from the powder mixture state to the state of a mixture of particulate materials obtained from this powder mixture. In all examples, each point plotted in the figures is generally an average of at least six exactly identical samples. The vibrating grinder used was an apparatus marketed under the trade name Vibromill by SWECO. It comprised a polyurethane vessel resting on springs and supporting an unbalanced motor. The vessel had a toroidal shape with a semicircular cross-section. The motion of the vessel induced a displacement of the movable grinding bodies (media), which underwent a triple motion. They “went up” against the external wall of the vessel and fell down, moved along the torus generator line, and rotated about themselves. The fall distance of the media was a function of the unbalance, and the rate of travel of the media along the torus generator line was a function of the angular distance between the upper unbalance and the lower unbalance. The conditions used in these examples were generally those recommended by SWECO. Thus, the parameters for adjusting the vibration intensity were the mass of the lower unbalance and the angular distance between the two unbalances. The lower unbalance consisted of five plates with a total mass of 575 g. The angular distance between the lower unbalance and the upper unbalance was 60°. The mass of the media used was 36 kg; the mass of powder (or mixture of powders) grinded in the examples was 4 kg. A metal cover closed the vessel. An opening in this cover allowed the powder(s) to be introduced. The junction between the vessel and the cover was sealed by O-rings. Before being shaped (compaction operation), the powders were prepared as follows: the powders were lubricated by adding 0.3% by weight of zinc stearate over 10 minutes at 20 rpm using a gently-acting mixer (Turbula trademark). The thus obtained mixture was then introduced into a cylindrical mould. The diameter of the mould was 10 mm and its height was set to 30 mm. Filling of the mould was carried out manually and the excess mixture was then scraped off. This mixture was then compacted and shaped by applying a stress appropriate for shaping, that is, a stress that may range preferably from 200 to 600 MPa. As will be seen thereafter, one of the advantages of the process according to the present invention, which makes it particularly reliable and reproducible, is precisely the fact that it smoothes out the differences in sinterability of powders compacted under varying shaping stresses. Consequently, the value of the shaping stress, as long as it remained in the above-mentioned range, had substantially no influence on the sinterability of the tested powders to obtain a dense material according to the present invention. The green compact obtained at the end of the preceding compaction step was then subjected to a sintering step in which the green compact was heated from ambient temperature to 1000° C. at a rate of 350° C./h, and this temperature of 1000° C. was then maintained for one hour. This temperature of 1000° C. was then increased at a rate of 350° C./h to 1700° C., which temperature was maintained for 4 hours. Lastly, cooling was carried out at a rate of 300° C./h. The sintering atmosphere was dry hydrogen. A slightly oxidizing or reducing humidified atmosphere could also have been appropriate, as long as the atmosphere at the end of the treatment makes it possible to obtain a stoichiometric phase of UO2. In order to determine, according to the present invention, the minimum given duration (corresponding to a minimum given grinding energy) during or beyond which said shaking must be performed so as to form said particulate material, a preliminary investigation was carried out, which consisted in grinding a uranium dioxide UO2 powder during a variable time interval. For each grinding duration, a powder sample was taken, and then when it was shaped (compaction operation), the density of the green compact was calculated based on the measured weights and dimensions of the green compacts. Then, a sintering operation was performed, following which a sintered body was obtained, whose density was measured under the same conditions. After these operations were finished, the change in density of the green compact as a function of the sintered body density was plotted, for each grinding duration, in a figure such as the one plotted for powder VH2, and shown by way of example in FIG. 1. The minimum given duration according to the present invention was then simply determined as the grinding duration beyond which the sinterability of the powder became substantially constant. For powder VH2, this duration was estimated to be 90 minutes, no significant change in sinterability being noted for a 120 minute duration, as illustrated in FIG. 1. Of course, one skilled in the art will be able to carry out a measurement of the minimum given duration (corresponding to a minimum given grinding energy), for a given grinding intensity and a given powder. Powders VH1, VH2, VH3 and VS1, and the particulate materials obtained according to the present invention from these powders then underwent the preparation and shaping operations under the above-mentioned operating conditions in order to form green compacts, and the density of each of them was measured according to the preceding procedure. The change in density of these eight green compacts as a function of the applied shaping stress is plotted in FIGS. 2 and 3. The overall operations described in the preceding paragraph were again performed for a mixture of powders comprising 50% of VH1+50% of VS1, by weight, as well as for the particulate material obtained according to the present invention from this mixture. The mixture had a specific surface area of 2.64 m2/g and the particulate material, a specific surface area of 3.21 m2/g. It was noted (see FIG. 2) that the density of the green compact containing the powders increased with the shaping stress. Its values for powders VH1, VH3 and VS1 were substantially similar, only powder VH2 having a slightly smaller value than the others. A similar observation was made for the mixture of powders VH1+VS1 (see FIG. 8). As regards the particulate materials, which were all produced in step b) for which the minimum given duration was 90 minutes, an increase in compressibility for all of these materials was noticed from FIG. 3. This increase was approximately 4% for smaller stresses (200 MPa) and 2% for larger stresses (600 MPa). A similar observation was made for the mixture of powders VH1+VS1 (see FIG. 9). It may thus be noted that, for a given shaping stress and a given shaking duration, which here is equal to the minimum given duration, the compressibility of these various materials is substantially constant after the process of the present invention has been applied, and that, for all powders (or powder mixtures) the increase in density as a function of the applied stress is smaller. This reduced dependence of the density of the green compacts on the applied stress advantageously makes it possible to reduce the previously mentioned deviation from cylindricality, when the nuclear fuel is shaped into a substantially cylindrical pellet. The fourteen green compacts (of which two contained a mixture of powders VH1+VS1) obtained in example 2 were subjected to a sintering operation under the above-mentioned operating conditions in order to form sintered bodies. The density of each green compact and the density of each sintered body were measured according to the above procedure. Sinterability was plotted in FIGS. 4 and 5 for the above-mentioned compacts containing only one powder and in FIGS. 10 and 11 for the above-mentioned compacts containing a mixture of powders. It was noticed from FIG. 4 that the powders, to which step b) of the process of the present invention was not applied, had widely different sinterabilities, whereas their compressibilities were close to one another. A similar observation was made for the mixture of powders VH1+VS1 (see FIG. 10). Conversely, it was observed in FIG. 5 that the 90 minute application of step b) of the process of the present invention led to a substantially constant and substantially identical sinterability, whatever the particulate material considered. A similar observation was made for the mixture of powders VH1+VS1 (see FIG. 11). Also, whatever the density of the green compact formed from the same particulate material, the density of the corresponding sintered bodies lay in the range from 10.61 to 10.71 g/cm3, which represented a density variation of less than 1%. This deviation is smaller than the density tolerance generally specified for the manufacture of nuclear fuel materials in the form of pellets or tablets or other shapes. Moreover, if the applied stress is restricted to the range from 300 to 500 MPa, which is the stress range generally used in the industry, the sintered densities all range from 10.66 to 10.70 g/cm3. It may thus be seen from these various examples, in particular from FIGS. 3 and 5 as well as FIGS. 9 and 11, that one of the distinctive features of the process of the present invention is that, even if the sinterability of the particulate material reaches, at the end of a given minimum shaking duration, an optimum value which thereafter remains substantially constant, it is nevertheless still possible, if needed, to adjust the compressibility of this material by continuing its shaking. Therefore, it is possible to adjust the compressibility of the powders (or mixture of powders) without modifying the density of the sintered body, which is generally a value specified by design. Thus, if another powder (or mixture of powders) is used in the process of manufacturing a fuel material, in order to keep the density of the sintered body constant, either i) the grinding duration is adapted and the shaping stress is not changed so as to obtain the same density of the green compact, or ii) the grinding duration is kept constant (larger than or equal to the minimum given duration of the present invention) and the shaping stress is adapted so as to obtain a constant green density (see FIG. 3). The flexibility and reliability of the process are thus remarkable. This very weak dependence of the density of the sintered bodies on the density of the green compacts advantageously makes it possible to control the dimensional properties without modifying the density of the sintered bodies. In addition, since shrinkage is generally a function only of the density of the considered powder (or mixture of powders) in the green state, it is sufficient to anticipate the sintering-induced shrinkage by accounting for it in the design size of the green compact, for example, by arranging to obtain a green compact which, compared to the sintered body, has dimensions which are greater by a value corresponding to said shrinkage. Thus, after sintering, whatever the origin of the powder (or origins of the powders constituting the mixture of powders), according to the present invention, an object having the desired size or a size as close as possible to the desired size (thus reducing re-grinding needs) is obtained by modifying only slightly, and within the specified interval, the density of the sintered bodies. The consistency, for a given density of the green compact, of the shrinkage value for different powders when they are shaken according to the process of the present invention, is illustrated in FIGS. 6 and 7. This is a significant advantage, in particular in terms of productivity and safety, when the invention is implemented for the manufacture of nuclear fuels in the form of pellets or tablets or other shapes, in an industrial setting.
	summary
	summary
	claims	1. A contour collimator or adaptive filter for adjusting a contour of a ray path of x-ray radiation, the contour collimator comprising:a magnetic fluid that is impermeable to x-ray radiation; andswitchable magnet elements, by which an aperture forming the contour is formable in the magnetic fluid by the magnetic fluid being attracted by magnetic fields of the switchable magnet elements. 2. The contour collimator or adaptive filter as claimed in claim 1, wherein the magnetic fluid is a ferrofluid. 3. The contour collimator or adaptive filter as claimed in claim 1, further comprising a first layer having the magnetic fluid. 4. The contour collimator or adaptive filter as claimed in claim 3, further comprising at least one second layer, in which the switchable magnet elements are arranged. 5. The contour collimator or adaptive filter as claimed in claim 4, further comprising an electrical grid structure formed from conductor paths in the at least one second layer, at points of intersection, of which the switchable magnet elements are arranged. 6. The contour collimator or adaptive filter as claimed in claim 1, wherein the switchable magnet elements include coils, through which current passes. 7. The contour collimator or adaptive filter as claimed in claim 1, further comprising an electric control unit operable to switch the magnet elements on and off in accordance with the contour to be formed. 8. The contour collimator as claimed in claim 4, wherein a plurality of first and second layers are stacked, the plurality of first and second layers comprising the first layer and the at least one second layer. 9. The contour collimator or adaptive filter as claimed in claim 2, further comprising a first layer having the magnetic fluid. 10. The contour collimator or adaptive filter as claimed in claim 9, further comprising at least one second layer, in which the switchable magnet elements are arranged. 11. The contour collimator or adaptive filter as claimed in claim 10, further comprising an electrical grid structure formed from conductor paths in the at least one second layer, at points of intersection, of which the switchable magnet elements are arranged. 12. The contour collimator or adaptive filter as claimed in claim 2, wherein the switchable magnet elements include coils, through which current passes. 13. The contour collimator or adaptive filter as claimed in claim 5, wherein the switchable magnet elements include coils, through which current passes. 14. The contour collimator or adaptive filter as claimed in claim 2, further comprising an electric control unit operable to switch the magnet elements on and off in accordance with the contour to be formed. 15. The contour collimator or adaptive filter as claimed in claim 5, further comprising an electric control unit operable to switch the magnet elements on and off in accordance with the contour to be formed. 16. The contour collimator as claimed in claim 5, wherein a plurality of first and second layers are stacked, the plurality of first and second layers comprising the first layer and the at least one second layer. 17. A method for adjusting a contour in a ray path of an x-ray radiation using a contour collimator or an adaptive filter, the method comprising:attracting a magnetic fluid and drawing the magnetic fluid from an area of an aperture; andforming the aperture as the contour by performing the attracting and drawing of the magnetic fields in a magnetic fluid that is impermeable to x-ray radiation. 18. The method as claimed in claim 17, wherein the magnetic fields are formed by switchable magnet elements. 19. The method as claimed in claim 17, wherein the magnetic fields are formed by electric currents. 20. The method as claimed in claim 18, wherein the magnetic fields are formed by electric currents.
053435044	abstract	To measure the spring constants of double-acting, fuel rod-centering springs assembled with different pairs of ferrules in a nuclear fuel bundle spacer, a gauge is provided to include an alignment rod and a probe carried by a handle for insertions into the ferrules of a ferrule pair. The alignment rod loads the side of the spring acting in its ferrule, while the other spring side exerts its fuel rod-centering force on a load cell carried by the probe. A micrometer acts against the load cell to produce measured deflections of the other spring side. Spring constants are calculated from electrical readouts of spring force and spring deflection from the load cell and micrometer.
	claims	1. An ion generator comprising:a vacuum chamber;an anode in the vacuum chamber, wherein the anode is a hollow anode formed by a metallic matrix and adapted to be positively charged and pressurized by a gas whereby electrons of the gas can be stripped off and diffused through the metallic matrix, whereby a purer reactive ionized gas can be supplied to interact enhancing the potential of high energy plasma double layers;two movable cathodes in the vacuum chamber; anda servo actuated motor operably connected to each movable cathode to move the two movable cathodes;whereby the position of the two movable cathodes relative to the anode can be varied. 2. The ion generator of claim 1, said each movable cathode further comprising a cathode disk and a cone shaped winding. 3. The ion generator of claim 2, further comprising a cone housing the cone shaped winding. 4. The ion generator of claim 1, wherein the vacuum chamber is capable of containing a gas under pressure, the gas selected from the group consisting of helium, hydrogen, deuterium, tritium, argon, water, nitrogen, oxygen, neon, and mixtures thereof. 5. The ion generator of claim 1, wherein the vacuum chamber is capable of containing a gas at a pressure up to and including 10-9 torr. 6. The ion generator of claim 1, further comprising a direct current regulated power supply for supplying radio and microwave frequencies, whereby plasma regimes in the ion generator may be enhanced. 7. The ion generator of claim 1, wherein the two movable cathodes comprising a material conducive to good electron emission. 8. The ion generator of claim 7, wherein the material selected from the group consisting of copper, stainless steel, aluminum, and tungsten. 9. The ion generator of claim 7, wherein the geometry of the electromagnetic field generators is selected from the group consisting of a spherical shape, a conical shape and geometric variants thereof, whereby the electromagnetic field providing the capability to either push ions away from the anode or coalesce toward the anode having the effect of enhancing natural formation of plasma double layers. 10. The ion generator of claim 1, wherein the servo actuated motors are capable of providing at least <0.01 mm of positional movement at a rate of 0.01 m to 1 m/second. 11. The ion generator of claim 1, further comprising electromagnetic field generators to further guide and tune high energy the plasma double layers. 12. The ion generator of claim 11, wherein the electromagnetic field generators comprise a coil geometry whereby an induced field can be even or uniform or adjusted to be stronger at one end of the vacuum chamber than at another end of the vacuum chamber. 13. The ion generator of claim 11, wherein the electromagnetic field generators are powered by an AC or DC power supply, whereby current being a primary factor affecting plasma manipulation. 14. The ion generator of claim 1, further comprising an anti-chamber which is adapted to enable the anode to be retracted without the need to pressurize the vacuum chamber from an experimental vacuum setting, separated by a butterfly valve capable of maintaining a desired pressure differential. 15. The ion generator of claim 14, wherein the anti-chamber comprising a lower section composed of a screw-driven base that feeds a driver with an anode mount, and an upper section that can be opened to enable change-out of the anode that is under a constant flow of inert gas to prevent atmospheric water adsorption.
046722130	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a container, especially for radioactive substances such as radioactive liquids, with an inner container for receiving the substances, an outer container which contains the inner container and thermal insulation between the inner and the outer container. 2. Description of the Prior Art Such a container is already in use. The thermal insulation between the inner and the outer container consists, for instance, of phenolic resin foam. The purpose of the foam insulation, in the event of a fire, is to prevent heat from the outside from entering into the inner container to cause a sudden rise in the pressure in the inner container, which may ultimately result in the bursting of this inner container and the escape of the radioactive substances. The thermal insulation between the inner and the outer container, however, prevents the escape of decay heat of the radioactive substances to the outside. The capacity of this container is very limited since in the course of time, with output of decay heat, a heat accumulation could occur which would lead to excessive high pressure in the inner container. SUMMARY OF THE INVENTION An object of the invention is to provide a container which is not limited in capacity with respect to radioactive substances or at least has increased capacity in this regard. With the foregoing and other objects in view, there is provided in accordance with the invention a container, especially adapted for enclosing radioactive substances such as radioactive liquids, which comprises; an inner container for receiving a substance to be contained, an outer container in which the inner container is disposed, and thermal insulation between the inner container and the outer container, in combination with a coolant tube associated with the inner container disposed within the outer container, said coolant tube containing a fluid coolant which can be circulated, a heat-discharge tube which also contains the coolant arranged at the outer container, and connecting lines at both tube ends of the cooling tube and the heat discharge tube through which said cooling tube and said heat discharge tube are in communication with each other. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a container, especially for radioactive substances, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
046577211	abstract	A system for illuminating a tiny target of fusion fuel with energy from a laser source to achieve uniform surface heat leading to fusion including a laser light source with a beam splitter to provide two laser beams directed to a common target point and a pair of identical ellipsoidal mirrors facing each other concavely and positioned to have a common reflective focal point, the mirrors each being coaxially and centrally apertured to pass respective laser beams to the other and opposed mirrors of said pair wherein reflected energy will be directed normal to and distributed around the surface of a spherical target located at the common spherical focus.
	summary
	description	This application claims the benefit of U.S. Provisional Application No. 62/890,813 filed Aug. 23, 2019, which is incorporated herein by reference in its entirety. The present invention relates generally to systems for storing used or spent nuclear fuel, and more particularly to an improved nuclear fuel cask which forms part of the storage system. In the operation of nuclear reactors, the nuclear energy source is in the form of hollow zircaloy tubes filled with enriched uranium, collectively arranged in multiple assemblages referred to as fuel assemblies. When the energy in the fuel assembly has been depleted to a certain predetermined level, the used or “spent” nuclear fuel (SNF) assemblies are removed from the nuclear reactor. The standard structure used to package used or spent fuel assemblies discharged from light water reactors for off-site shipment or on-site dry storage is known as the fuel basket. The fuel basket is essentially an assemblage of prismatic storage cells each of which is sized to store one fuel assembly that comprises a plurality of individual spent nuclear fuel rods. The fuel basket is arranged inside a cylindrical metallic storage canister (typically stainless steel), which is often referred to as a multi-purpose canister (MPC), which forms the primary containment. The canister loaded with SNF is then placed into an outer ventilated overpack or cask, which forms the secondary containment, for safe transport and storage of the multiple spent fuel assemblies. Casks are used to transfer the SNF the cask from the spent fuel pool (“transfer cask”) in the nuclear reactor containment structure to a more remote staging area for interim term storage such as in the dry cask storage system of an on-site or off-site independent spent fuel storage installation (ISFSI) until a final repository for spent nuclear fuel is available from the federal government. A significant number of dry storage casks containing SNF congregated at an ISFSI pad, however, often accrue radiation dose at the nuclear plant's site boundary that exceeds the allowable limit for the local jurisdiction and/or the federal government. The dose emanating from such casks must be attenuated to enable them to be used in the intermediate term storage role at an ISFSI. Improvements in radiation level reduction for dry storage casks which overcomes the foregoing deficiencies are desired. To overcome the foregoing limitations in the art for intermediate storage of spent nuclear fuel (SNF) or other high level radioactive nuclear wastes generated by the nuclear reactor at a nuclear facility, the present disclosure provides a tertiary radiation containment approach to supplement the primary and secondary containment measures of the canister and dry storage cask which may still emit radiation exceeding acceptable dosage limits. A nuclear waste storage system according to the present disclosure generally comprises an outer radiation-shielded cask containment enclosure configured for housing a nuclear waste dry storage cask inside (which in turn contains the radioactive SNF canister housing the waste). The shielded enclosure may be incorporated directly into the previously mentioned independent spent fuel storage installation (ISFSI) or other intermediate nuclear waste storage facility. In some installations, each storage cask in the array of casks of the ISFSI may include a tertiary radiation shielded outer enclosure. In certain embodiments, the outer shielded cask containment enclosure may be embedded at least partially in the concrete pad of the independent spent fuel storage installation (ISFSI) to take advantage of the gamma and neutron radiation blocking/attenuation properties of the thick concrete mass. The shielded enclosure may comprise two parts including a lower base portion embedded at least partially in the concrete pad, and a separate discrete upper radiation shielding portion coupled thereto at a circumferential joint. In some embodiments, the portions may be approximately equal height representing half-sections; however, either portion may be taller than the other in some implementations. The base and radiation shielding portions are coupled together in the field at the ISFSI to complete the cask containment enclosure which completely surrounds the nuclear waste cask. The upper shielding portion is coupled to the lower base portion after the cask is placed inside the base portion. In some embodiments, an annular gasket forms a gas-tight seal between the lower and upper portions of the enclosure. The upper shielding portion may be configured as a radiation-blocking shield jacket which is positioned over the upper portion of the cask which protrudes upwards beyond the lower base portion and is otherwise exposed above the top surface of the concrete pad (i.e. grade). The jacket is fabricated of radiation blocking/shielding material for reducing radiation emissions from the cask. In preferred embodiment, the shielding material comprises a boron-containing material and metal which effectively blocks/attenuates both gamma and neutron radiation. In some embodiments, the cask containment enclosure may be ventilated to allow ambient cooling air to flow inwards between the containment enclosure and cask via natural convective thermo-siphon effect induced air flow as the air within the enclosure is heated by the heat radiating outwards from the cask. The cooling air ventilation system may comprise a plurality of upper air inlets formed which may be formed in the middle waist area of the cask containment enclosure at the horizontal circumferential joint between the lower base portion and upper shielding portion. The natural flow air ventilation system thus is unaided by a powered blower or fan which therefore does not rely on an available source of power. This allows the cask containment enclosure to be located at remote sites and is not susceptible to power outages which could in result in overheating the enclosure and compromising the structural integrity of the cask-canister containment vessels. The concrete pad of the interim storage facility may be expansive in extend being dimensioned in length and width to hold a plurality of shielded enclosures in an array. Examples of such facilities are the HI-STORE consolidated interim storage facility from Holtec International of Camden, N.J. Advantageously, the cask containment enclosure disclosed herein reduces radiation emitted by the cask directly at its source, in contrast to other possible approaches focused on the site boundary of the ISFSI such as constructing earthen berms or thick concrete walls around the entire perimeter of the storage site. Such peripheral amelioration of the radiation dosage problems is not only expensive due to the required length of the perimetrically-extending berms or walls, but notably these measures do not reduce the ambient radiation levels inside the ISFSI itself where crews work. The radiation field within the ISFSI is beneficially ameliorated by the present cask containment enclosure resulting in reduced radiation dose to the plant staff in the ISFSI. In addition, there is no limit to the amount of shielding and/or type than can be used and combined in the radiation-blocking shield jacket; therefore, substantial dose reductions can be realized which is not possible with a berm construction. According to one aspect, a containment enclosure for shielding a nuclear waste cask comprises: a lower base portion at least partially embedded in a concrete pad, the base portion comprising a baseplate supporting a plurality of coaxially aligned shells defining a lower cavity; an upper radiation shielding portion coupled to and supported by the lower base portion, the shielding portion defining an upper cavity; the shielding portion comprising a radiation shielding material configured to block gamma and neutron radiation; the lower and upper cavities collectively defining a contiguous containment space configured for holding the cask; wherein the base and shielding portions enclose the cask. According to another aspect, a nuclear waste storage system comprises: a concrete pad; and a plurality of cask containment enclosures arranged on the concrete pad, each containment enclosure housing a storage cask containing a canister holding radioactive nuclear waste. Each containment enclosure comprises: a cylindrical lower base portion at least partially embedded in the concrete pad, the lower base portion comprising a baseplate supporting a plurality of coaxially aligned shells defining a lower cavity; a separate upper shield jacket coupled to and supported by the lower base portion, the shield jacket having a wall construction comprising boron-containing radiation shielding materials, the upper shield jacket defining an upper cavity; a plurality of ambient cooling air inlets formed in the shield jacket, the air inlets circumferentially spaced apart at a circumferential joint between the base portion and the shield jacket; an annular air inlet plenum formed at a bottom of the shield jacket by an inwardly recessed stepped portion of the shield jacket, air inlet plenum located at the circumferential joint and in direct fluid communication with the air inlets and a downcomer formed in the lower base portion; a plurality of air exchange passageways circumferentially spaced apart at a bottom of the base portion, the passageways in fluid communication with the downcomer and a riser which extends vertically between the cask and innermost surfaces of the lower base portion and shield jacket; and a top discharge opening formed in the shield jacket in fluid communication with the riser and ambient air; wherein the storage cask containing nuclear waste is positioned partially in both the upper and lower cavities of the lower base portion and shield jacket. According to another aspect, a method for providing radiation shielding for a cask containing a nuclear waste canister comprises: at least partially embedding an upwardly open base portion in a concrete pad; lowering the cask into the upwardly open lower cavity of the base portion; positioning a shield jacket over the cask; and abuttingly engaging the shield jacket with the base portion forming a circumferential joint therebetween; wherein the cask is fully enclosed by the shield jacket and base portion. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. All drawings are schematic and not necessarily to scale. Features shown numbered in certain figures which may appear un-numbered in other figures are the same features unless noted otherwise herein. The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls. As used herein, the terms “seal weld or welding” shall be construed according to its conventional meaning in the art to be a continuous weld which forms a gas-tight joint between the parts joined by the weld. FIGS. 1-14 depict a nuclear waste storage system comprising a cask containment enclosure 100 for housing and shielding a nuclear waste cask 20 to ameliorate gamma and neutron radiation emitted by the spent nuclear fuel (SNF) or other high lever radioactive waste held in the SNF canister contained inside the cask. Cask 20 may be any commercially-available storage and/or transport cask, such as a HI-STORM cask available from Holtec International of Camden, N.J. or other. Cask 20 has a vertically elongated metallic cylindrical body including an open top 21 end, a circular bottom closure plate 22 defining a bottom end 23, a cylindrical sidewall 24 extending between the ends, and an internal cavity 28. The cylindrical metallic SNF canister 30 (represented schematically by dashed lines and well known in the art) containing radioactive SNF or other nuclear waste W is insertable into cavity 28 through top end 21, which is then closed by a bolt-on lid 25 to seal the cask 20. Cavity 28 extends for a full height of the cask. The cavity 28 is configured (e.g. dimensions and transverse cross-sectional area) to conventionally holds only a single SNF canister 30. Cask 20 may be comprised of a single long cylindrical shell 24, or alternatively may be formed by a plurality of axially aligned and vertically stacked cylinder segments seal welded together at the joints therebetween as best shown in FIG. 9 to collectively form the cask body. A pair of lifting lugs or protrusions 26 (see, e.g. FIGS. 3-4) are standardly provided for lifting and transporting the cask 20 via a motorized cask crawler typically driven by tank-like tracks for hauling the extremely heavy casks (e.g. 30 ton or more). Such robust cask crawlers are well known in the art without need for further elaboration and conventionally used for transporting and raising/lowering casks at a nuclear reactor facility (e.g. power generation plant or other) or interim nuclear waste storage facility. Cask crawler transporters are commercially-available from companies such as J&R Engineering Co. of Mukwonago, Wis. (e.g. LIFT-N-LOCK®) and others. Bottom closure plate 22 of cask 20 may be considered cup-shaped in one embodiment having a cylindrical vertical stub wall 22a which rises up a short distance from the horizontal flat canister support surface 22b of the closure plate on which the SNF canister 30 is positioned when loaded into the cask. In other possible embodiments, however, the bottom closure plate 22 may be a flat plate and the lower end of cylindrical shell 24 may be welded directly to the peripheral edge of the plate. The sidewall 24 of cask 20 may have a composite construction including at least one cylindrical metallic shell 29 and radiation shielding material 27. In some embodiments, the shielding material 24 may comprise concrete, lead, boron-containing materials, or a combination of these or other materials effective to block and/or attenuate gamma and neutron radiation emitted by the nuclear waste W in canister 30 enclosed by the cask 20. In certain embodiments, the radiation shielding material may be sandwiched between a pair of shells 29 depending on the nature and hardness of the material (only one shell shown in the figures for clarity). The cask containment enclosure 100 of the nuclear waste storage system will now be described with continuing reference general reference to FIGS. 1-14. Cask containment enclosure 100 is a two-part vessel generally including lower base portion 101 and a separate discrete upper radiation shielding portion 102 coupled thereto at a circumferential joint 107 at the ISFSI 200 or other interim storage facility (see, e.g. FIG. 15). Upper radiation shielding portion 102 may alternatively be referred to herein as simply “upper shielding portion” for brevity. Cask containment enclosure 100 defines a vertical longitudinal axis LA aligned with the geometric center of the enclosure (shown in FIG. 9). In some embodiments, the lower base and upper shielding portions 101, 102 may be approximately equal in height H1, H2 (respectively) representing half-sections; however, either portion may be shorter or taller than the other in some implementations. Lower base portion 101 and upper shielding portion 102 each have a respective height H1, H2 which is less than the height H3 of cask 20. Accordingly, the lower and upper portions are therefore coupled together to completely surround and enclose the full height of the cask. Lower base portion 102 may be embedded at least partially in a concrete pad 50 of ISFSI 200 as shown. A majority of the height H1 of lower base portion 101, and preferably substantially the entire lower base portion except for the uppermost top portion which is coupled to the upper shielding portion 102 may be embedded (see, e.g. FIG. 9). This provides that about at least half the height H3 of the cask 20 is below grade G to help protect the cask and nuclear waste W therein in the event of a projectile impact. In addition, the embedment results in a lower overall exposed profile of the cask containment enclosure 100, which is less detectable and susceptible to both attack and severe weather incidents. In some embodiments, the lower base portion 101 may have a height H1 substantially greater than the height H2 of the upper shielding portion 102 such that a majority of the height of the cask 20 sits and is protected below grade G. This concomitantly results in the shorter upper shielding portion 102 having a lower exposed profile than illustrated, and the lower base portion 101 embedded further downward in concrete pad 50 than illustrated. The present cask containment enclosure 100 advantageously allows either portion to be customized in height as desired. It bears noting that figures preceding FIG. 15, which shows an example of a complete ISFSI 200, show only a cutout portion of the concrete pad 50 immediately surrounding each cask containment enclosure 100 for compact illustrative purposes. With continuing reference to FIGS. 1-14, the lower base portion and upper shielding portion 101, 102 each define a partial-height cavity of certain vertical depth relative to the height of the cask 20. Lower base portion 101 defines a lower cavity 103 of the cask containment enclosure 100. Upper shielding portion 102 defines an upper cavity 103 which communicates directly with the lower cavity. When the separable upper shielding portion is coupled to the lower base portion, cavities 103 and 104 combine to collectively define a contiguous common containment space 105 configured for holding and enclosing the entirety of the cask 20. The depth of the cavities 103, 104 may be adjusted as desired to suit architectural or other design considerations. Referring particularly to FIGS. 7-11 and 14, lower base portion 101 in some embodiments may comprise a horizontal baseplate 106 supporting a plurality of coaxially aligned and vertically oriented cylindrical shells which define the lower cavity 103. The shells of the base portion 101 comprise an outer shell 110, and a pair of closely spaced innermost “conjugate” shells 111, 112 which structurally act as a double-walled stiffened single shell to better support and transfer the weight of the upper shielding portion 102 to the concrete pad 50. Shell 112 forms the inner boundary of base portion 102 surrounding cask 20 and defines the lower cavity 103. The paired conjugate shells are spaced radially inwards from outer shell 110 by a radial gap R1 defining a corresponding distance substantially greater than a radial gap R2 formed between the conjugate shells (see, e.g. FIG. 14). In some embodiments, gap R2 may be about 1 inch or less. Gap R2 in certain embodiments may be less than ½ inch such as for example without limitation about ⅛ inch in one non-limiting construction. Gap R2 may be evacuated for increasing thermal resistance to heat transfer across the shells. This prevents radially transmitted heat from cask 20 from pre-heating ambient cooling air descending in the cooling air downcomer 130 (FIG. 9) until the air can be evenly distributed around the exterior of the cask, as further described herein. Bottom ends of shells 110-112 are hermetically seal welded to baseplate 106. The top ends of the conjugate shells 111, 112 are closed by an annular seal plate 142 welded thereto which completely encloses the radial gap R2. Radial gap R1 between the outer shell 110 and conjugate shells remains open at the top to define a portion of the cooling ventilation air inlet to annular downcomer 130. Gap R1 structurally defines the cooling ventilation air downcomer 130 in lower base portion 101. The outer shell 110 and paired conjugate shells 111, 112 may be formed of steel, and preferably of corrosion resistant stainless steel in one embodiment. Other suitably strong structural metals however may be used. Upper shielding portion 102 may be in the form of a double-walled radiation-blocking shield jacket 120 comprising radiation shielding material configured and selected to effectively block/attenuate gamma and neutron radiation. Because shield jacket 120 is located entirely above grade G of the concrete pad 50, it preferably provides the supplemental radiation shielding needed to compensate for radiation emission not blocked by the shielding of cask 20 alone which may exceed the allowable local and national dosage limits. The shield jacket 120 preferably extends for substantially the full height of the body of the upper shielding portion 102 (see, e.g. FIG. 9). The shield jacket has a composite wall construction comprising an outer wall 121, an inner wall 122, and an intermediate layer 123 sandwiched therebetween which is formed a radiation shielding material. Intermediate layer 123 is preferably thicker than the inner and outer walls in some embodiments as shown. Shield jacket 120 of the upper shielding portion 102, formed by walls 121, 122 and intermediate layer 123, may have a compound shape including a lower cylindrical section 120a and upper frustoconical section 120b in some non-limiting embodiments. Frustoconical section 120b acts as a venturi which concentrates the internal rising and heated ventilation air flow and increases its velocity leaving top discharge opening 124, thereby advantageously increasing the naturally-driven thermos-siphon effect and amount of ambient cooling air drawn into the cask containment enclosure 100 to optimize the dissipation of heat generated by the cask 20. The sections 120a, 120b may be fabricated separately and seal welded together in the manufacturer's fabrication shop to form an integrated and self-supporting shield jacket structure which can be lifted and transported as a single unit. The top portion of upper cavity 104 terminates in a top vent or discharge opening 124 defined at the top end 126 of jacket 120. Top opening is protected by a cap 125 which still allows the heated cooling air to exit the upper shielding portion 102, but prevents the ingress of debris and rain into jacket. Cap 125 defines a plurality of laterally open air discharge outlets 125a through which the heated cooling air ascending in the cask containment enclosure 100 is discharged to atmosphere. The walls 121, 122 of radiation-blocking shield jacket 120 may be formed of steel, and preferably of corrosion resistant stainless steel in one embodiment. Other suitably strong structural metals however may be used. Steel is effective at gamma ray blocking. The intermediate layer 123 of jacket 120 may comprise boron-containing material which is effective to deflect and attenuate the neutron radiation. In some embodiments, the intermediate layer 123 may be formed of Holtite™ (a proprietary product of Holtec International of Camden, N.J.), which generally comprises hydrogen rich polymer impregnated with boron carbide particles. Other boron containing materials however may be used and the invention is not limited to use of the foregoing proprietary product. The metallic walls 121, 122 protect the intermediate layer 123 which may be softer and less impact resistant. The intermediate layer 123 thus protects the against direct neutron streaming, and in some embodiments may have a greater thickness than the inner or outer walls 121, 122. Other gamma or neutron blocking/attenuation materials may be included and used in the construction of the radiation-blocking shield jacket 120, such as for example without limitation lead or copper as some non-limiting examples. The upper shielding portion 102 is separated from and sealed to the lower base portion 101 at horizontal circumferential joint 107 by a flat annular gasket 140 compressed between a flat annular upper seal plate 142 of the lower base portion and a flat annular lower seal plate 141 of the shielding portion (best shown in FIGS. 9 and 10). The seal plates and gasket preferably have approximately the same radial width to form a gas-tight seal. The seal plates may be formed of a suitable preferably corrosion resistant metal (e.g. stainless steel) which is welded to each of their respective lower and upper portions 101, 102 at the joint. Any suitable commercially-available gasket material capable of making a gas-tight seal at joint 107 between the seal plates 141, 142 may be used (e.g. neoprene or other). The weight of the upper shielding portion 102 maintains the gasket 140 in the compressed state. The ambient cooling air ventilation system will now be further described. The cooling air ventilation system essentially includes: (1) an annular downcomer 130 formed in the lower base portion 101; (2) annular riser 132 collectively formed in both the lower base and upper shielding portions 101 between the cask 20 and the base and shielding portions; (3) a plurality of circumferentially spaced upper air inlets 133 formed at the joint 107 between the lower base and shielding portions; (4) upper air inlet plenum 131 in direct fluid communication with the upper air inlets and the downcomer; (5) a plurality of circumferentially spaced internal air exchange passages 134 in lower base portion 101 which are in fluid communication with the bottom of both the downcomer and riser to introduce cooling air into the lower portion of lower cavity 103 of the base portion; (6) top discharge opening 124 formed in the shield jacket 120 of the upper shielding portion; and (7) top discharge openings 125a formed in cap 125. These components fluidly cooperate to draw ambient cooling air into the cask containment enclosure 100 via natural gravity driven thermo-siphon effect as air heated by the cask in the containment space 105 of the enclosure creates the cooling air flow circulation or path shown by the dashed air flow lines CA in FIG. 9. The cooling air dissipates the heat emitted by cask 20 from the decaying nuclear waste stored in the canister 30 therein. Details of the foregoing portions of the cooling air ventilation system will be further described below. Cooling air inlet plenum 131 is formed at the circumference joint 107 between the lower base portion and upper shielding portion 101, 102. The bottom end of radiation-blocking shield jacket 120 may have an inwardly stepped configuration as best shown in FIGS. 9 and 10. This creates an inwardly region at the middle waist portion of cask containment enclosure 100 to define the annular upper air inlet plenum 131 of the cooling air ventilation system. This waist portion and concomitantly the air inlet plenum 131 are located above grade G of the concrete pad 50. In the event of a prevailing or other weather related wind, the inlet plenum advantageously allows the ambient air to circulate around the cask containment enclosure 100 from the higher windward air pressure side to the leeward lower air pressure side to ensure even distribution of ambient air to the downcomer 130. To in part protect the air inlet plenum 131 from debris and excessive rain infiltration, an annular castellated air inlet skirt 145 is attached to the bottom end of the outer wall 122 of the shield jacket 120. Skirt 145 therefore at least partially encloses the otherwise outwardly open recessed air plenum 131. Outer wall 122 of shield jacket 120 terminates a vertical distance above the top of the lower base portion outer shell 110, and this space is taken up by the skirt 145. Skirt 145 may therefore have the same outer diameter as the outer wall 122 of the jacket 120 to form a flush transition between the jacket and lower base portion 101 as shown. In one embodiment, as best shown in FIG. 10, a flat annular ring plate 147 may be welded to the bottom end of outer wall 122. The top end of skirt 145 is welded to the ring plate. The bottom end of the skirt 145 defined by the bottom ends of the downwardly-extending castellations 146 may be fielded welded in turn to the top end 149 of the lower base portion outer shell 110 after the upper shielding portion 102 is placed on the lower base portion 101 (see, e.g. FIG. 10). This provides a few advantages. First, this physically and laterally stabilizes the coupling between these two portions to resist laterally acting forces such as those that might be created by a seismic event (e.g. earthquake). By filling in the vertical gap or void at the waist portion of the cask containment enclosure 100 created by the air inlet plenum, skirt 145 therefore creates a vertically continuous structure between outermost wall 122 of shield jacket 120 to outermost shell 110 of lower base portion 101 to transmit a portion of the dead weight of the upper shield jacket to the lower base portion at the peripherally of the cask containment enclosure 100. In addition to the coupling between the lower base portion 101 and upper shielding portion 102 at the inboard gasketed portion of the joint 107, this provides a secondary outboard coupling. This further ensures stability of the inboard gasketed interface between the lower base portion 101 and upper shielding portion 102. The circumferential joint 107 thus may be considered to be both a gasketed at its inboard side and welded at it peripheral outboard side. In the illustrated embodiment, the plurality of upper air inlets 133 are defined by the open areas formed between the castellations 146 of the air inlet skirt 145; which represents any additional function of the skirt. The air inlets place the air inlet plenum 131 in direct fluid communication with ambient cooling air. The annular cooling air downcomer 130 is in turn in direct fluid communication with the air inlet plenum 131. Air inlets 133 are circumferentially spaced apart preferably around the entire circumference of the cask containment enclosure 100. Any suitable shape air inlets may be used such as polygonal (e.g. rectangular as shown) or non-polygonal. Advantageously, the air inlet skirt 145 is configured to both define the air inlets 133 while the castellations of the skirt serve a structural purpose to distribute a portion of the weight load of the shield jacket 120 to the outer shell 110 of the lower base portion 101. In one embodiment, the annular air inlet skirt 145 may be circular and circumferentially continuous in structure. An annular ring wall 148 having a greater height than radial thickness closes the inboard portion or side of the air inlet plenum 131. Ring wall 148 may be seal welded to the ring plate 147 at top and to seal plate 141 of the shield jacket 120 at bottom (see, e.g. FIG. 10). Radial gap R3 formed between ring wall 148 and innermost wall 121 of the conjugate shells of the upper shielding portion 101 is filled with the same contiguous radiation shielding material of the intermediate layer 123. This ensures that the inlet air plenum 131 and air inlets 133 protect against straight line radiation streaming from the cask 20 to the ambient environment from the waist area of the cask containment enclosure 100. In the illustrated preferred embodiment, the ring wall 148 and innermost wall 121 of the shield jacket 120 are radially spaced apart by the same radial distance (defined by gap R3) as the radial distance (defined by gap R2) between the pair of conjugate shells 111, 112 of lower base portion 101. This ensures both even distribution of the weight load from the upper shielding portion 102 to the lower base portion 101 and compression of gasket 140. The internal air exchange passages 134 in one embodiment may be collectively formed by radially aligned through holes in the paired conjugate shells 111, 112 of the lower base portion 101. Preferably, passages 134 are formed in the terminal bottom end of shells 111, 112 to introduce cooling air into the lowest point possible of the cask containment space 105 of the cask containment enclosure 100 at the baseplate 106 of lower base portion 101. Passages 134 are circumferentially spaced apart and may have any suitable polygonal or non-polygonal shape. In the non-limiting illustrated embodiment, passages 134 are downwardly open such that baseplate 106 formed the bottom side of the passages. The air exchange passages allows air descending in to the downcomer 130 to be drawn radially inwards into the cask containment space 105 and enter the bottom end of the cooling air riser 132 for optimum cooling of the cask 20. The annular cooling air riser 132 is formed in containment space 105 of cask containment enclosure 100 by the radial gap created between cask 20 and the innermost wall or shell of the upper shielding portion 102 and lower base portion 101 as best shown in FIG. 9. Accordingly, the inside diameter of the containment enclosure is preferably larger than the outside diameter of the cask by an amount selected to be the radial width of the annular riser. The riser 132 terminates at top to form a common discharge air plenum 135 between the top of the cask 20 and top end 126 of the shield jacket 120 of upper shielding portion 102. The plenum 135 assumes a frustoconical due to the shape of the frustoconical section 120b of the jacket 120. As noted elsewhere herein, upwardly conversing shape of the discharge air plenum concentrates and increases the velocity of the rising air heated by the cask to effectively drive the thermos-siphon (aka chimney effect) which optimizes cooling of the cask. In operation, with reference to the cooling air flow lines CA in FIG. 9, air at ambient temperature is drawn radially inwards into and through the upper air inlets 133 and flows radially, into the cooling air inlet plenum 131 from all sides of the cask containment enclosure 100. The air is then drawn vertically downwards into downcomer 130 to the bottom of enclosure 100. The air flows radially inwards through the air exchange passages 134 into containment space 105 and reverses direction flowing vertically upwards in riser 132 along the sides of cask 20 as it is heated by the cask 20. The now heated rising air collects in the discharge plenum 135 above the cask through top discharge opening 124, enters the cap 125, and is discharged radially/laterally outwards therefrom through the plural air discharge outlets 126a back to atmosphere. It bears noting that this naturally driven air cooling system cools the cask which may not be a vented design as shown. The cask, which contains the SNF canister 30 which holds the nuclear waste, emits decay heat which must be dissipated to protect the structural integrity of both the cask and canister. In the above cooling air ventilation system design, it bears noting that no straight line of sight exists from the containment space 105 inside cask containment enclosure 100 to the outside environment through either air inlets 133 or air discharge outlets 125a in cap 125. Cap 125 is terminated at top with a lid 125b to eliminate a straight line of sight in the vertical direction from the top of cask 20 to atmosphere. It also is notable that the cooling air ventilation system, and particularly the air inlet plenum 131 and air inlets 133, are only fully formed and completed for operation once the upper shield jacket 120 is placed on the lower base portion 101 embedded in the concrete pad 50. A method or process for providing radiation shielding for a cask 20 containing a nuclear waste canister 30 using cask containment enclosure 100 will now be briefly summarized. General reference is made to FIGS. 1-14 in the description which follows, with reference to specific figures noted as needed. The method begins with the step of first embedding the lower base portion 101 of cask containment enclosure 100 in the concrete pad 50. This step in some implementations may include sub-steps including a two pour process for forming the concrete pad. This includes first pouring/forming a flat-topped lower foundation section 50a of the concrete pad (reference FIG. 7). This provides temporary support for the lower base portion 101. Next, the lower base portion 101 is then positioned on top of the poured foundation section. The baseplate 106 of lower base portion 101 rests directly on the foundation section as shown. Next, a second pour is made creating an upper section 50b of concrete pad 50 which embeds the lower base portion 101 of cask containment enclosure 100. The upper section 50b is poured to a depth such that the final grade G of the concrete pad 50 remains below the cooling air inlets 133, thereby keeping the inlets exposed. It bears noting that due to its embedment, the lower base portion 101 preferably has no lateral openings to preclude the unhardened concrete from entering the base portion. The exposed part of the outer shell 110 of the lower base portion 101 preferably has a sufficient height selected to prevent runoff from entering the air inlets 133. The main method or process continues by lowering and positioning the cask 20 containing canister 30 with nuclear waste W therein into the upwardly open lower cavity 103 of the lower base portion 101. The annular gasket 140 may be placed on annular seal plate 142 of the lower base portion 101 before or after positioning the cask in the lower base portion. The process then continues by positioning the upper shielding portion 102 (i.e. shield jacket 120) over the cask and on top of the embedded lower base portion 101 of cask containment enclosure 100. During the process, the gasket 140 at circumferential joint 107 is compressed between the lower base portion and upper shielding portion (i.e. between seal plate 142 of lower base portion and seal plate 141 of the upper shielding portion). The castellations 146 of the air inlet skirt 145, which preferably is already shop welded onto the shield jacket 120, are concurrently abuttingly engaged with the outer shell 110 of the lower base portion 101. The castellations may then be welded to the shell 110. It bears noting that lifting lugs 150 (represented schematically in FIG. 5) of any suitable configuration may be welded to the lower base portion 101 and upper shielding portion 102 to facilitate lifting these parts of the cask containment enclosure 100 with a cask transport crawler, crane, or other suitable lifting equipment. The foregoing simple process effectively shields the cask 20. The natural convective air cooling ventilation system is automatically activated by the heat emitted from the cask once enclosed in the now fully assembled cask containment enclosure 100. FIG. 15 shows an example of a full ISFSI (independent spent fuel storage installation) comprising an array of cask containment enclosures 100 according to the present disclosure. The vacant aisles formed between rows of the enclosures need only be width enough to allow the tracks or wheels of the cask crawler to straddle each enclosure for first loading the cask into the previously embedded lower base portions 101, and placing the upper shielding portions 102 thereon. This allows the cask containment enclosures to be tightly packed in an array on the concrete pad 50. The pad may be formed as a single large concrete structure formed at one time, or in multiple sections formed over time as additional cask storage space is needed. Numerous advantages can be attributed to the two-piece cask containment enclosure 100. For example, the two-part system which is field assembled makes it easier to handle and transport each of the lower base portion 101 and upper shielding portion 102 individually rather than as a larger single shop-fabricated enclosure cask storage enclosure with a circular top closure lid. In another aspect, multiple lower base portions 101 formed of the cylindrical coaxial metal shells previously described herein can be pre-installed and embedded in the concrete pad 50 well in advance of storing any SNF or other high level radiation waste at the ISFSI. The ISFSI is therefore prepared to accept casks 20 containing the nuclear waste at any point in time thereafter when needed in accordance with the method previously described herein. Pre-installed lower base portions 101 may be temporarily capped to prevent ingress of rainwater until the cask storage space is needed. In addition, since the lower base portion 101 receives the benefit of radiation shielding provided by the concrete pad 50, no additional radiation shielding materials are required for this lower unit which reduces the overall cost of the cask storage enclosure. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
054065976	abstract	A boiling water reactor includes a pressure vessel containing a reactor core, chimney, steam separator assembly, and steam dryer assembly therein, with the vessel being filled with reactor water to a normal water level through the steam separator assembly. A plurality of control rod drives extend downwardly from the bottom of the pressure vessel and are operatively joined to control rods extending downwardly into the reactor core. The chimney includes a plurality of channels disposed above the core and laterally spaced apart to define guide slots for receiving the control rods as they are selectively translated upwardly out of the core by the control rod drives. The chimney has a vertical height for increasing the normal water level above the reactor core and for providing a space for the control rods withdrawn from the reactor core by the bottom-mounted control rod drives. The control rods are selectively withdrawn upwardly from the core and inserted downwardly into the core by the control rod drives, which also are effective for selectively releasing the control rods for allowing gravity to insert the control rods into the core.
040653510	abstract	This invention provides a poloidal divertor for stacking counterstreaming ion beams to provide high intensity colliding beams. To this end, method and apparatus are provided that inject high energy, high velocity, ordered, atomic deuterium and tritium beams into a lower energy, toroidal, thermal equilibrium, neutral, target plasma column that is magnetically confined along an endless magnetic axis in a strong restoring force magnetic field having helical field lines to produce counterstreaming deuteron and triton beams that are received bent, stacked and transported along the endless axis, while a poloidal divertor removes thermal ions and electrons all along the axis to increase the density of the counterstreaming ion beams and the reaction products resulting therefrom. By balancing the stacking and removal, colliding, strong focused particle beams, reaction products and reactions are produced that convert one form of energy into another form of energy.
	description	This application is a continuation of U.S. application Ser. No. 11/028,219, filed Jan. 4, 2005, now U.S. Pat. No. 7,078,691, the contents of which are incorporated herein by reference. The present invention claims priority from Japanese application JP 2004-049218 filed on Feb. 25, 2004, the content of which is hereby incorporated by reference on to this application. The present invention relates to electron-beam metrology including a standard reference for metrology used in electron-beam metrology. Standard references for metrology for electron-beam metrology according to the prior art use a grating which is fabricated over a semiconductor substrate by laser interferometer lithography and anisotropic chemical etching. Their calibration is accomplished by measuring the diffraction angle of grating by the use of a laser beam whose absolute accuracy is guaranteed (see, for instance, Japanese Patent Application Laid-Open No. 7-71947). The minimum possible dimensions for the standard references mentioned are determined by the resolution limit of laser interferometer lithography. The lower limit of the pitch is ½ of the wavelength of the laser beam that is used. The minimum possible pitch of argon ion lasers of 351.1 nm in wavelength currently used in a laser interferometer lithography system is about 200 nm. Exposure devices whose laser beam source is altered to a shorter wavelength involve many problems, and are difficult to develop. Similarly, there is a limit to the accuracy of diffraction angle measurement of grating using a laser beam for the calibrating purpose, and such measuring is impossible at a minimum pitch below 200 nm approximately. On the other hand, as semiconductor devices are ever more reduced in size, the minimum machining dimension is now less than 100 nm. Whereas the dimensional management of such ultra-fine machining uses an electron-beam metrology system, standard references of dimensions are indispensable for the absolute accuracy management of such a system. However, conventional standard references of dimensions cannot meet the requirements of the minimum machining dimensions of the latest semiconductor devices. Moreover, the patterning of grating using laser interferometer lithography can prepare only simple line and space patterns very because of its principle. For this reason, the same pattern is formed all over the specimen, making it impossible to form positioning marks. Therefore, it cannot be accurately specify the position of the grating pattern which was used in calibration with a pitch size proving device and a metrology system. Where an electron-beam metrology system is used, consecutive use of any specific pattern would invite deterioration in calibration accuracy because the sticking of contamination ensuing from irradiation with a beam gives rise to dimensional variations in the specimen. An object of the present invention, attempted in view of the problems noted above, is to provide a standard reference for metrology having finer reference sizes and high-precision electron-beam metrology including the same. In order to achieve the object stated above, in the basic configuration according to the invention, finer pattern areas than a conventional grating pattern are formed over a plurality of identical semiconductor members separately from the conventional grating pattern. Thus, the pitch size of a grating pattern of not less than 200 nm, which is the pitch size of the conventional grating pattern, is figured out by diffraction angle measurement of the grating using a laser beam, and the pitch size so figured out is used as an absolute size. Apart from this grating pattern, a grating pattern whose minimum pitch size is not more than 100 nm is formed over the same semiconductor member. Since the proof of this pattern is impossible by conventional diffraction angle measurement of the grating using a laser beam whose wavelength is absolutely guaranteed, the pitch size of the conventional grating pattern, figured out as described above as the absolute size by using an electron-beam metrology system, a scanning probe microscope or a deep ultraviolet short-wavelength laser of which the wavelength is not necessarily guaranteed absolutely, is used as reference. This makes possible, by arranging a pattern of or above a length for the same scanning range of an electron-beam or a probe, calibration permitting ready beam addressing. Further by arranging near this pattern a mark pattern whose shape is easily distinguishable from other patterns, recording of positional information measured with an electron-beam or a probe is made possible. Thus, by arranging a pattern permitting conventional diffraction angle measurement of grating by the use of a laser beam and a fine pattern matching the minimum machining dimensions of the latest semiconductor devices within the same member, a standard reference for metrology and calibration by which fineness and high accuracy are made compatible can be realized. Further, by arranging patterns in the vertical direction and patterns in the lateral direction within the same member, unprecedented size calibration in both vertical and lateral directions can be realized at the same level of accuracy. By keeping the distance between these pattern units within 20 μm, calibration can be accomplished under the same optical conditions of the electron-beam metrology system, and accordingly a higher level of accuracy can be achieved. Next will be described how this standard reference for metrology is fabricated. A conventional grating pattern and a fine pattern matching minimum machining dimensions of the latest semiconductor devices cannot be arranged within the same member by laser interferometer lithography using a conventional standard reference for metrology because of its limitation in resolution and in the freedom of pattern creation. In view of this problem, the invention uses electron-beam delineation excelling in resolution and unlimited in pattern shaping. For the fabrication of a highly accurate standard reference for metrology improved in uniformity in the specimen plane, an electron-beam cell projection exposure method by which the desired pattern is formed into a stencil mask and projected in a reduced size with an electron-beam for exposure is particularly effective. Thus, since a plurality of kinds of delineation patterns of grating in the vertical and lateral directions are all fabricated into stencil masks, accurately reproducible patterning is possible without dimensional variations from shot to shot by selecting the desired mask by beam deflection and exposing it to light repetitively. Combination of this patterning method and dry etching makes possible fine standard references for metrology suitable for use with an electron-beam metrology system of a scanning probe microscope. Formation of square apertures in stencil masks in advance would make possible variable shaped delineation with no limitation of the variety of patterns. When a fine size is to be measured in calibrating an electron-beam metrology system with this standard reference, size calibration is accomplished with a proven fine grating pattern by using an electron-beam metrology system, a scanning probe microscope or a deep ultraviolet solid-state short-wavelength laser. Proper accomplishment of the calibration can be confirmed by measuring, after this calibration, the pitch size of a proven grating with a laser beam whose wavelength is absolutely guaranteed. The configuration is such that, if the measured size and the pitch size figured out from the diffraction angle surpass the reference, the electron-beam metrology system issues an alarm, and another fine pattern is used in that case. Thus, by calibrating the electron-beam metrology system again by using a fine pattern in another location than the previously used fine grating with reference to the mark pattern, the high level of calibration accuracy can be maintained. Typical examples of configuration according to the invention will be described below. (1) A standard reference for metrology according to the invention includes, disposed over a substrate, a first grating unit pattern formed of an array of gratings whose pitch size is figured out in advance by optical means, and a second grating unit pattern formed of an array of gratings smaller than the first grating unit pattern in pitch size. (2) In the standard reference for metrology described in (1) above, the minimum pitch size of the second grating unit pattern may not be greater than 100 nm. (3) In the standard reference for metrology described in (1) above, a first pattern area in which a plurality of the first grating unit patterns are arranged and a second pattern area in which a plurality of the second grating unit patterns are arranged may be disposed over the substrate. (4) In the standard reference for metrology described in (1) above, a mark pattern for beam addressing of probing means for use in metrology may be provided over the substrate. (5) In the standard reference for metrology described in (3) above, the second pattern area may contain a plurality of mark patterns including positional information on each of the plurality of the second grating unit patterns. (6) The standard reference for metrology described in (1) above may further have, over the substrate, a third grating unit pattern formed of gratings arrayed in a direction different from the gratings constituting the first grating unit pattern and a fourth grating unit pattern formed of gratings arrayed in a direction different from the gratings constituting the second grating unit pattern, wherein the pitch size of the fourth grating unit pattern is smaller than the pitch size of the third grating unit pattern. (7) In the standard reference for metrology described in (6) above, a first pattern area in which a plurality of the first grating unit patterns are arranged, a second pattern area in which a plurality of the second grating unit patterns are arranged, a third pattern area in which a plurality of the third grating unit patterns are arranged, and a fourth pattern area in which a plurality of the fourth grating unit patterns are arranged may be disposed over the substrate. (8) In the standard reference for metrology described in (6) above, the first grating unit pattern and the third grating unit pattern may be arranged to form a grating with each other may be and the second grating unit pattern and the fourth grating unit pattern, arranged to form a grating with each other. (9) In the standard reference for metrology described in (1) or (6) above, a distance between the grating unit patterns may be within 20 μm. (10) A method of calibration of electron-beam metrology systems according to the invention is a method using a standard reference for metrology to perform measurement by scanning a prescribed area of a specimen with an electron-beam, wherein the standard reference for metrology is provided, over a substrate, with a first grating unit pattern formed of an array of gratings whose pitch size is figured out in advance by optical means and a second grating unit pattern formed of an array of gratings whose pitch size is smaller than that of the first grating unit pattern, the first grating unit pattern is measured, a difference between a result of the measurement and the pitch size is calculated and compared with a reference value and, if the difference is greater than the reference value, the second grating unit pattern is measured to calibrate the measured value. (11) An electron-beam metrology system according to the invention has a specimen mounting stage for holding a specimen, electron optics for scanning the specimen on the specimen mounting stage with an electron-beam, a secondary electron detector for detecting a secondary electron-beam generated by the scanning with the electron-beam, operation treatment means for measuring the specimen by analyzing a signal waveform obtained from the detector, display means for displaying a result of the measurement, storage means in which reference sizes are stored for use in calibrating the result of measurement, and a standard reference for metrology held on the specimen mounting stage, wherein the standard reference for metrology is provided, over a substrate, with a first grating unit pattern formed of an array of gratings whose pitch sizes are found in advance by optical means, and a second grating unit pattern formed of an array of a plurality of gratings smaller than the first grating unit pattern in pitch size, and the operation treatment means compares a result of the measurement and the reference sizes and, if a different surpasses a certain value, causes the display means to display abnormality of calibration. According to the invention, a standard reference for metrology having a finer reference size and highly accurate electron-beam metrology including the same can be realized. Preferred embodiments of the present invention will be described in detail below with reference to accompanying drawings. FIG. 1 through FIG. 5 show one example of standard reference for beam metrology according to the invention. FIG. 6 shows an example of standard reference for metrology for an electron-beam metrology system according to the prior art. Conventionally, the trench pattern of unevenness on the semiconductor substrate of orientation (110) is prepared as a grating pattern 28 in a fixed direction by laser interferometer lithography and wet etching as shown in FIG. 6. The pitch of the grating pattern 28 is about 200 nm, and this value is obtained by diffraction angle measurement using a laser. The grating pattern 28 is formed all over a standard reference substrate 27 of 4 mm square. Calibration of an electron-beam metrology system using this reference substrate would involve the following problems. The first problem concerns fineness. The latest semiconductor patterns include some whose minimum machining dimension is less than 100 nm. However, as the minimum pitch of conventional grating patterns by laser interferometer lithography is 200 nm, a full pitch of a grating pattern overflows the field of view of image of 200,000 or more magnifications for use in semiconductor pattern metrology, making calibration impossible at this level of magnification. The second problem is posed by the impossibility to identify the position of calibration because of the pattern uniformity all over the specimen. For this reason, a plurality of points in the specimen are measured and the measurements are averaged, resulting in a correspondingly long time taken for calibration. Furthermore, a grating in only one direction can be prepared for a pattern of unevenness on the semiconductor substrate of orientation (110). This means a disadvantage that dimensional calibration can be accomplished in only one direction. By contrast, according to the invention, an electron-beam cell projection exposure method is used for pattern exposure and a dry process for etching. Though this method permits patterning of 100 nm or less in pitch, diffraction angle measurement is optically difficult for a grating of this pitch size because its wavelength is proven as an absolute size because of a wavelength limit. In view of this difficulty, a grating pattern shown in FIG. 1 was prepared in the calibration pattern area 3 of a standard reference substrate 5. This grating pattern is formed of grating unit patterns 1 in each of which 10 trenches of 2 μm in length are arrayed at a pitch of 200 nm and which are arranged at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively. In part of this array, grating unit patterns 2, in each of which 20 trenches of 2 μm in length are arrayed at a pitch of 100 nm, are arranged. Around the periphery of the calibration pattern area 3, cross patterns for beam addressing 400 and 401 of probing means for measurement use are arranged. In the standard reference, the standard reference substrate 5 of 5 mm square containing these patterns and the calibration pattern area in which trenches of the aforementioned grating unit patterns are arrayed in the vertical direction (or the lateral direction) are arranged. By measuring the diffraction angle by irradiating this standard reference with an He—Cd laser whose wavelength was guaranteed as an absolute size, it was proven that the pitch size of the grating unit pattern 1, containing 10 trenches at a pitch of 200 nm, was 200.01 nm with a tolerance of 0.01 nm. The pitch size of the grating unit pattern 2, containing 20 trenches at a pitch of 100 nm, was determined by using a scanning probe microscope (e.g. an AFM) in the following manner, and a value of 100.45 nm was obtained. First, in search for a grating unit pattern, the parallelism between the moving directions of the standard reference and the scanning probe microscope was corrected by using the cross patterns for beam addressing 400 and 401, and the position of each grating unit was kept at or below 2 μm. Then, the pitch size of the grating unit pattern 1 containing 10 trenches at a pitch of 200 nm in the array was measured, and after carrying out size calibration of the scanning probe microscope by setting this size to 200.01 nm, the pitch size of the grating unit pattern 2 was measured. Since the length of the grating unit pattern 2 was 2 μm, the scanning by the scanning probe microscope could be positioned to the grating unit pattern with an accuracy of 100%, and the pitch size was successfully figured out from the measurement of a 19-pitch equivalent. In the same way, the pitch sizes of 20 or more different grating unit patterns 2 were figured out, and their average was determined to be 100.45 nm. Next will be described how the electron-beam metrology system using this standard reference for metrology is calibrated. A specimen wafer 32 containing a device pattern of 50 nm in designed size and a standard reference 35 fitted to a holder 34 are mounted on the stage 33 of the electron-beam metrology system as shown in FIG. 7. The device pattern of 50 nm in designed size is measured with the electron-beam metrology system at 200,000 or more magnifications. At this level of magnification, a full pitch of a grating of 200 nm in pitch which is the conventional size standard, cannot be covered by scanning with an electron-beam 30 focused by electron optics 29, and accordingly the system cannot be calibrated. For the calibration of this magnification level, the pitch size of the grating unit patterns 2 was measured with the electron-beam metrology system. First to search for the grating unit pattern 2 in which 20 trenches were arrayed at a pitch of 100 nm, the parallelism between the moving directions of the specimen and the electron-beam metrology system was corrected by using the cross patterns for beam addressing 400 and 401. Next, the pitch size of the grating unit pattern 2 within the array was measured with the secondary electron signal waveform from a secondary electron detector 31. In the same way, the pitch sizes or 20 or more different grating unit patterns 2 were figured out, and their average was determined to be 100.45 nm to make possible calibration. To confirm the correctness of this calibration, the pitch size of the grating unit pattern 1 containing 10 trenches at a pitch of 200 nm in the array was measured at a magnifying power of 100,000, which permitted one pitch to be covered by the scanning range, and was determined to be 200.06 nm. In this standard reference, as the distance between the grating unit pattern 2 in which 20 trenches were arrayed at a pitch of 100 nm and the grating unit pattern 1 containing 20 trenches at a pitch of 200 nm was 2.5 μm, i.e. within the 20 μm range in which measurement was possible without altering the focusing condition of the electron optics 29 of the electron-beam metrology system, calibration of high accuracy could be realized. As a result, the difference from the pitch size of 200.01 nm obtained by measuring the diffraction angle was 0.05 nm, indicating a satisfactory level of accuracy. Next, the method of fabricating the standard reference for metrology according to the present invention will be described. First, after an oxide film of 100 nm was formed over an Si substrate, the surface was coated with a resist. Then, in the flow of fabrication charted in FIG. 8, pattern formation was carried out with an electron-beam cell projection exposure system mounted with stencil masks having apertures 10 and 11 shown in FIG. 9. An aperture 38 corresponding to the grating unit pattern containing 10 trenches at a pitch of 200 nm, one of the patterns for calibration, was selected by beam deflection, and exposure was accomplished in a desired position on the specimen by beam deflection (step 81). The dosage for this delineation was 10 μC/cm2, adequate for the resolution of the grating unit pattern containing 10 trenches at a pitch of 200 nm (step 82). Next, an aperture 40 corresponding to the grating unit pattern containing 20 trenches at a pitch of 100 nm, another of the patterns for calibration, was selected by beam deflection, and exposure was accomplished in a desired position on the specimen by beam deflection (step 83). The dosage for this delineation was 15 μC/cm2, adequate for the resolution of the grating unit pattern containing 20 trenches at a pitch of 100 nm (step 84). Next, by using a square aperture for variable shaped method 36, exposure was accomplished to place the marks 400 and 401 for correcting the specimen rotation on the left and right sides of the periphery where exposure had been accomplished for the grating pattern (step 85). The dosage for this delineation was 7 μC/cm2, adequate for the resolution of the mark pattern (step 86). In the same way, the grating pattern in the lateral direction was delineated. An aperture 37 corresponding to the grating unit pattern containing 10 trenches at a pitch of 200 nm, one of the patterns for calibration, was selected by beam deflection, and exposure was accomplished to place the grating pattern in the lateral direction in a desired position on the specimen by beam deflection. The dosage for this delineation was 10 μC/cm2, adequate for the resolution of the grating unit pattern containing 10 trenches at a pitch of 200 nm. Next, an aperture 39 corresponding to the grating unit pattern containing 20 trenches at a pitch of 100 nm, another of the patterns for calibration, was selected by beam deflection, and exposure was accomplished to place it in a desired position on the specimen by beam deflection. The dosage for this delineation was 15 μC/cm2, adequate for the resolution of the grating unit pattern containing 20 trenches at a pitch of 100 nm. After development, the oxide film was etched with the resist as the mask, and then the Si substrate was dry-etched (step 87). For delineation, both vertical and lateral directions of the grating pattern were prepared in advance on the same substrate by electron-beam exposure as described above. As the use of the electron-beam cell projection method for the grating pattern resulted in exposure of any position of the specimen with the same stencil mask, it was made possible to form a uniform pattern with dimensional fluctuations of no more than 5 nm. Incidentally, as the distances between different gratings can be shortened in the example of pattern shown in FIG. 1, there is provided an advantage that proof by SEM can be accurately accomplished. FIG. 2 shows another example of standard reference for metrology according to the invention. In the grating pattern shown in FIG. 2, grating unit patterns 6 containing 10 trenches of 2 μm in length at a pitch of 200 nm are arrayed in a calibration pattern area 8 of 2 mm square at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively. In the vicinity of this area, a grating unit pattern 7 in which 20 trenches of 2 μm in length are arrayed at a pitch of 100 nm is arranged in a calibration pattern area 9 of 2 mm square, as in the figure. In the peripheries of the grating patterns, cross marks for beam addressing 100 and 101 are arranged. On the standard reference substrate 5, there are arranged, in addition to these patterns, calibration pattern areas 11 and 12 of 2 mm square, each containing grating arrays in which lines of the grating unit are laterally arranged as illustrated. FIG. 3 shows details of these areas. In these calibration pattern areas 11 and 12, grating unit patterns 13 and 14 are laterally arrayed at the same lengths and at the same pitches as in the grating unit patterns 6 and 7, respectively. The diffraction angle was measured by irradiating with an He—Cd laser, whose wavelength was guaranteed as an absolute size, a 2-mm square area in this standard reference, the area in which grating unit patterns 6 containing 10 trenches at a pitch of 200 nm were arrayed at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively, and it was thereby proven with a tolerance of 0.01 nm that the pitch size of the grating unit patterns 6 was 200.02 nm. The pitch size of the grating unit patterns 7 in which 20 trenches were arrayed at a pitch of 100 nm was found to be 100.40 nm by diffraction angle measurement with a deep ultraviolet solid-state laser of 193 nm in wavelength. In this measurement, first the pitch size of the grating unit pattern 6 containing 10 trenches at a pitch of 200 nm was determined by diffraction angle measurement with a deep ultraviolet solid-state laser of the same wavelength 193 nm, and by measuring the diffraction angle by irradiation with an He—Cd laser whose wavelength was guaranteed as an absolute size a value of 200.02 nm was obtained. The diffraction angle measurement with the deep ultraviolet solid-state laser of 193 nm in wavelength was thereby calibrated. Next will be described the calibration of the electron-beam metrology system using this standard reference for metrology. The specimen wafer 32 containing a device pattern of 50 nm in designed size and the standard reference are mounted on the electron-beam metrology system as shown in FIG. 7. The device pattern of 50 nm in designed size is measured with the electron-beam metrology system at a magnification power of 200,000 or more. If a grating of 200 nm in pitch, which is the conventional size standard, is measured at this magnification power, one pitch will overflow electron-beam scanning, and therefore the system cannot be calibrated. For calibration at this magnification power, the pitch size of the grating unit pattern 7 was measured with the electron-beam metrology system. First, the parallelism between the moving directions of the specimen and the electron-beam metrology system was corrected by using the cross marks for beam addressing 100 and 101 to find the grating unit pattern 7 in which 20 trenches were arrayed at a pitch of 100 nm. Next, the pitch size of the grating unit pattern 7 in the array was measured. In the same way, the pitch sizes of 20 or more different grating unit patterns 7 were measured, and calibration was successfully accomplished by averaging the measurements to 100.40 nm. In order to confirm the correctness of this calibration, the pitch size of the grating unit pattern 6 containing 10 trenches at a pitch of 200 nm in the array was measured at 100,000 magnifications, a power permitting one pitch to be covered by scanning, and a pitch size of 200.08 nm was obtained. The result was so satisfactory that the difference from the pitch size of 200.02 nm obtained by measuring the diffraction angle was only 0.06 nm. In the same way, measurement calibration of the electron-beam metrology system in the lateral direction was successfully achieved with high accuracy by using the array of the grating unit patterns 14 in which 20 trenches were arrayed at a pitch of 100 nm and that of the grating unit patterns 13 in which 10 trenches were arrayed at a pitch of 200 nm incorporated into the standard reference pattern in the lateral direction as shown in FIG. 3. Incidentally, the examples of pattern shown in FIG. 2 and FIG. 3, as the calibration pattern areas are separate, have an advantage that both the pattern of the greater pitch size and that of the smaller pitch size can be proven by optical diffraction. FIG. 4 shows still another example of standard reference for metrology according to the invention. In the grating pattern shown in FIG. 4, grating unit patterns 15 containing 10 trenches of 2 μm in length at a pitch of 200 nm are arrayed at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively, in a calibration pattern area 17 of 2 mm square. In the vicinities of this area, grating unit patterns 16 and 161 in which four trenches of 2 μm are arrayed at a pitch of 100 nm are arranged in a calibration pattern area 18 of 2 mm square as illustrated. In positions laterally away from these grating unit patterns having four trenches by 2 μm each, mark patterns 160 and 162 different in shape from one another, by one or another of which the position of each grating unit pattern can be identified, are placed. Further, cross marks for beam addressing 102 and 103 are arranged in the peripheries of the grating patterns. Over this standard reference substrate 5, calibration pattern areas 19 and 20 of 2 mm square each, containing grating arrays in which the trenches of the grating unit pattern 15 are arrayed in the lateral direction, are arranged in addition to these patterns. The diffraction angle was measured by irradiating with an He—Cd laser whose wavelength was guaranteed as an absolute size a 2-mm square area in this standard reference, the area in which the grating unit patterns 15 containing 10 trenches at a pitch of 200 nm are arrayed at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively, and it was thereby proven with a tolerance of 0.01 nm that the pitch size of the grating unit patterns 15 was 200.01 nm. Further, the pitch size in the central part of the grating unit patterns 16 containing four trenches at a pitch of 100 nm was determined by using a scanning probe microscope in the following manner, and values of 100.55 nm and 100.65 nm were obtained. First, the parallelism between the moving directions of the specimen and the scanning probe microscope was corrected by using the cross marks 102 and 103 for beam addressing to find the grating unit pattern, and the position toward each grating unit was kept at or below 2 μm. Next, after carrying out size calibration of the scanning probe microscope by measuring the pitch size in the central part of the grating unit pattern 15 containing 10 trenches at a pitch of 200 nm in the array and setting this size to 200.01 nm, the pitch size of the grating unit patterns 16 was measured. Since the grating unit patterns 16 were 2 μm long, scanning by the scanning probe microscope was successfully was positioned to the grating unit patterns with 100% correctness. The positions of the measured grating patterns allowed discrimination by scanning the mark pattern 160 located nearby. Next will be described calibration of the electron-beam metrology system using this standard reference for metrology. This electron-beam metrology system has a system configuration as shown in FIG. 12, and calibration was performed in accordance with a calibration program so designed that the calibration could be accomplished in the procedure charted in FIG. 11. In the measuring procedure, an electron-beam 42 radiating from an electron-gun 41 was narrowed with lenses 43 and 45, secondary electrons 48 generated when a specimen 46 mounted on a stage 47 was scanned by a deflector 44 were detected by a secondary electron detector 49, and the waveform was determined by a beam deflection control unit and a secondary electron signal treatment unit. The size was computed from this waveform, and was displayed and stored as the correct line width through line width calibration operation. The electron-beam metrology system according to the invention further has a differential operation unit and a calibration state display unit for comparison for calibration as shown in FIG. 12, and the correctness of calibration is verified by comparison with different reference sizes, and can be displayed. The actual measuring procedure will be described below. The specimen wafer 32 and the standard reference containing a device pattern of 50 nm in designed size are mounted on the electron-beam metrology system as shown in FIG. 7. The device pattern of 50 nm in designed size is measured with the electron-beam metrology system at a magnification power of 200,000. In a grating of 200 nm in pitch, which is the conventional size standard, is measured at this magnification power, one pitch will overflow electron-beam scanning, and therefore the system cannot be calibrated. The calibration of this magnification power was accomplished in the procedure charted in FIG. 11. The pitch size of the grating unit pattern 16 was measured with the electron-beam metrology system. First, the parallelism between the moving directions of the specimen and the scanning probe microscope was corrected by using the cross marks for beam addressing 102 and 103 to find the grating unit pattern 16 in which four trenches were arrayed at a calibrated pitch of 100 nm. Then, the pitch size of the grating unit pattern 16, calibrated on the basis of the mark pattern 160 in the array, was measured by displaying and storing in the line width memory unit the size according to the waveform display and line width operation obtained from the beam deflection control unit and the secondary electron signal treatment unit. That pitch value was calibrated with the line width calibration operation unit to make it 100.55 nm, and calibration was accomplished by storing that line width into the storage unit (step 111). In order to confirm the correctness of the calibration, the pitch size of the grating unit pattern 1 containing 10 trenches at a pitch of 200 nm in this array was measured at 100,000 magnifications, a power permitting one pitch to be covered by scanning, through the line width calibration operation unit calibrated according to the configuration of FIG. 12, and a pitch size of 200.03 nm was obtained (step 112). The difference from the pitch size of 200.01 nm obtained by measuring the diffraction angle was 0.02 nm. As this difference was not more than 0.1 nm, set as the reference value (step 113), a display of normality was instructed by the differential operation unit for comparison with reference value to the calibration state display unit, and a satisfactory measurement was guaranteed (step 114). In the same way, measurement calibration of the electron-beam metrology system in the lateral direction was successfully achieved with high accuracy by using the grating unit pattern array 20 in which four trenches were arrayed at a pitch of 100 nm in the lateral direction and the grating unit patterns 19 in which 10 trenches were arrayed at a pitch of 200 nm incorporated into the same standard reference pattern as what is shown in FIG. 4. Next, similar calibration was carried out three months later using the same grating patterns as the above-described. First, the parallelism between the moving directions of the specimen and the electron-beam metrology system was corrected by using the cross marks for beam addressing 102 and 103 to find the grating unit pattern 16 in which four trenches were arrayed at a calibrated pitch of 100 nm, and then the pitch size of the grating unit pattern 16, placed in the same position as before and calibrated on the basis of the mark pattern 160 in the array, was measured. Calibration was successfully accomplished by making the pitch value 100.55 nm. In order to confirm the correctness of the calibration, the pitch size of the grating unit pattern 15 containing 10 trenches at a pitch of 200 nm in this array was measured at 100,000 magnifications, a power permitting one pitch to be covered by scanning, and a pitch size of 200.25 nm was obtained. As its difference from the pitch size of 200.01 nm obtained by measuring the diffraction angle was 0.24 nm, surpassing the 0.1 nm set as the reference of calibration, a display of abnormality was instructed by the differential operation unit for comparison with reference value to the calibration state display unit of the electron-beam metrology system (step 115). For this reason, in accordance with the procedure charted in FIG. 11, a grating unit pattern 161 which was in another position and in which four trenches were arrayed at a calibrated pitch of 100 nm was identified on the basis of the mark pattern 162, and calibration was successfully accomplished by measuring its pitch size to determine the size to be 100.65 nm (step 111). In order to confirm the correctness of the calibration, the pitch size of the grating unit pattern 15 containing 10 trenches at a pitch of 200 nm in this array was measured at 100,000 magnifications, a power permitting one pitch to be covered by scanning, and a pitch size of 200.02 nm was obtained (step 112). The difference from the pitch size of 200.01 nm obtained by measuring the diffraction angle was a satisfactory result of 0.01 nm (step 113), indicating that highly accurate calibration was maintained and stable measurement performance was successfully continued (step 114). By contrast, in system calibration using the conventional electron-beam metrology system of the configuration shown in FIG. 10 and the conventional calibration pattern 28 shown in FIG. 6, the calibration pattern 28 is used many times during the long-term operation for months as mentioned above. For this reason, if contamination by irradiation with electron-beams gives rise to size variations in calibration pattern, the accuracy cannot be guaranteed on account of the absence of a function to compare with a plurality of size references or to display whether calibration is satisfactory or not. Incidentally, the example of pattern shown in FIG. 4 has an advantage of permitting ready measurement with an AFM or the like because the position of the pattern of the smaller pitch size can be identified. FIG. 5 shows yet another example of standard reference for metrology according to the invention. Referring to FIG. 5, the grating pattern is such that grating unit patterns 21 containing 10 trenches of 2 μm in length at a pitch of 200 nm are arrayed at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively, in a calibration pattern area 23 of 2 mm square. In part of this array, grating unit patterns 210 containing 10 trenches at a pitch of 200 nm in the lateral direction are arranged as illustrated. In the vicinity of this area, grating unit patterns 22 in which 20 trenches of 2 μm in length are arrayed at a pitch of 100 nm are arrayed in a calibration pattern area 24 of 2 mm square as illustrated. In part of this array, grating unit patterns 220 containing 20 trenches in the lateral direction at a pitch of 100 nm are arranged as shown in FIG. 5. In the peripheries of the grating pattern 1, cross marks for beam addressing 104 and 105 are arranged. The diffraction angle was measured by irradiating with an He—Cd laser whose wavelength was guaranteed as an absolute size the 2 mm square calibration pattern area 23 in this standard reference, the area in which grating unit patterns 21 and 210 containing 10 trenches at a pitch of 200 nm are arrayed at pitches of 2.5 μm and 2.4 μm in the vertical and lateral directions, respectively, and it was thereby proven with a tolerance of 0.01 nm that the pitch size of both grating unit patterns 21 and 210 was 200.02 nm. Further, the pitch sizes of grating unit patterns 22 and 220 containing 20 trenches at a pitch of 100 nm were determined by diffraction angle measurement using a deep ultraviolet solid-state laser of 193 nm in wavelength, and a value of 100.40 was obtained for both. In this measurement, first the pitch sizes of the grating unit patterns 21 and 210 containing 10 trenches at a pitch of 200 nm were determined by diffraction angle measurement with a deep ultraviolet solid-state laser of the same wavelength 193 nm, and by measuring the diffraction angle by irradiation with an He—Cd laser whose wavelength was guaranteed as an absolute size, a value of 200.02 nm was obtained. The diffraction angle measurement with the deep ultraviolet solid-state laser of 193 nm in wavelength was thereby calibrated. Next, calibration of the electron-beam metrology system using this specimen will be described. The specimen wafer 32 and the standard reference containing a device pattern of 50 nm in designed size are mounted on the electron-beam metrology system as shown in FIG. 7. The device pattern of 50 nm in designed size is measured with the electron-beam metrology system at a magnification power of 200,000. In a grating of 200 nm in pitch, which is the conventional size standard, is measured at this magnification power, one pitch will overflow electron-beam scanning, and therefore the system cannot be calibrated. For calibration at this magnification power, the pitch size of the grating unit pattern 22 was measured with the electron-beam metrology system. First, the parallelism between the moving directions of the specimen and the electron-beam metrology system was corrected by using the cross marks for beam addressing 104 and 105 to find the grating unit pattern 22 in which 20 trenches were arrayed at a pitch of 100 nm. Then, the pitch size of the grating unit pattern 22 in the array was measured. In the same way, the pitch sizes of 20 or more different grating unit patterns were measured, and calibration was successfully accomplished by averaging the measurements to 100.40 nm. In order to confirm the correctness of this calibration, the pitch size of the grating unit pattern 21 containing 10 trenches at a pitch of 200 nm in the array was measured at 100,000 magnifications, a power permitting one pitch to be covered by scanning, and a pitch size of 200.08 nm was obtained. The result was so satisfactory that the difference from the pitch size of 200.02 nm obtained by measuring the diffraction angle was only 0.06 nm. In the same way, measurement calibration of the electron-beam metrology system in the lateral direction was successfully achieved with high accuracy within a tolerance of 0.1 nm by using the array of the grating unit patterns 220 in which 20 trenches were arrayed at a pitch of 100 nm and the array of the grating unit patterns 210 in which 10 trenches were arrayed at a pitch of 200 nm incorporated into the standard reference pattern in the lateral direction. Since the distance between these grating units in the vertical and lateral directions was 2.5 μm, within the 20 μm range in which measurement is possible without altering the focusing condition of the electron-beam metrology system, calibration of high accuracy could be realized in both vertical and lateral directions. Incidentally, the example of pattern shown in FIG. 5 has an advantage of permitting highly accurate calibration in both vertical and lateral directions because the vertical and lateral directions are close to each other. Although the description of the standard reference for calibration in each of the foregoing examples referred to what was configured by sticking a patterned semiconductor substrate 35 to the holder 34 as shown in FIG. 7, highly accurate measurement is also possible, even if the patterned semiconductor substrate has the same wafer shape as the wafer 32 intended to be measured, by first calibrating the system mounted with the standard reference for calibration use, then replacing it with the wafer 32 to be measured and measuring it. Further, though the foregoing description refers to grating arrays in each of which trenches of grating unit patterns are arrayed in vertical and lateral directions as shown in FIG. 2 through FIG. 5, obviously the applicability of the invention is not limited to these grating arrays but also covers such grating arrays in which the trenches of grating unit patterns are arrayed in mutually different directions. As hitherto described, the present invention makes possible dimensional calibration for smaller pitch sizes than what is proven by an optical diffraction angle with a laser whose wavelength is absolutely guaranteed. Furthermore, the invention makes possible setting of a pitch size proven by an optical diffraction angle with a laser whose wavelength is absolutely guaranteed and a reference pattern finer than that and realization of a guarantee of the appropriateness of calibration by comparing the two reference sizes, thereby enabling highly accurate electron-beam metrology to be accomplished. Highly accurate calibration of metrology is further made possible for patterns in vertical and lateral directions by arranging two mutually orthogonal patterns over the same substrate.
	claims	1. A fast reactor having a reflector control system, comprising:a reactor vessel which is filled with a liquid metal coolant;a reactor core including a fuel assembly, which is placed at a central position of the reactor vessel; anda neutron reflector including a region, which is placed at an upper side thereof, and at which a neutron absorber or a neutron transmitting material having a neutron reflection ability lower than that of the liquid metal coolant is placed and a reflection region which is placed at a lower side thereof and provided outside the reactor core so as to be moved in a vertical direction in an installed state of the fast reactor for adjusting leakage of neutrons from the reactor core so as to control a reactivity thereof,wherein said neutron reflector is moved in an upward direction in accordance with a change in reactivity caused by burn-up of a fuel, andwherein said fuel assembly includes a fuel pin bundle having fuel pins filled with a fissile fuel and a non-fissile fuel placed in a wrapper tube and having an outermost fuel pin adjacent to the neutron reflector and another fuel pin placed at a farther distance away from the neutron reflector, and wherein, prior to neutron exposure in the reactor, the ratio of the fissile fuel amount in the outermost fuel pin to total amount of the fissile fuel and the non-fissile fuel in the outermost fuel pin is made smaller than the ratio of the fissile fuel amount in the another fuel pin to the total amount of the fissile fuel and the non-fissile fuel in another fuel pin. 2. The fast reactor according to claim 1, wherein said neutron reflector further has a low reflection region at a central portion thereof, and the low reflection region has a lower neutron reflection ability as compared to the reflection region. 3. The fast reactor according to claim 1, wherein said reflection region of the neutron reflector includes at least one of carbide and graphite, and the neutron reflector includes a region made of steel containing at least one of chromium and nickel. 4. The fast reactor according to claim 1, wherein said reflection region has a largest thickness of the neutron reflector. 5. The fast reactor according to claim 1, wherein said reflection region comprises a neutron reflector material having a highest effective density the neutron reflector. 6. The fast reactor according to claim 1, further comprising an external frame formed of steel which contains at least one of chromium and nickel, wherein said external frame encloses the neutron reflector. 7. The fast reactor according to claim 6, wherein said external frame including at least of a part which comprises austentic stainless steel having a high resistance against swelling, the stainless steel containing iron, chromium, and nickel as a primary component, and further containing titanium. 8. The fast reactor according to claim 1, wherein said neutron reflector includes at least of a part which comprises austentic stainless steel having a high resistance against swelling, the austentic stainless steel containing iron, chromium, and nickel as a primary component, and further containing titanium. 9. The fast reactor according to claim 1, wherein said neutron reflector is provided so as to surround the reactor core, and a position of a boundary in the axial direction between the reflection region and the remainder of the neutron reflector varies with a circumferential position. 10. The fast reactor according to claim 1, wherein said reactor core has a first region having a higher ratio of fissile material to total amount of fissile and non-fissile material than that in a second region of the reactor core, and said first region being a region other than said second region being located from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to a place at substantially one half of the height thereof. 11. The fast reactor according to claim 1, wherein said reactor core has a first region having a higher fuel smear density than that in a second region of the reactor core, and said first region being a region other than said second region being located from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to a place at substantially one half of the height thereof. 12. The fast reactor according to claim 1, wherein said reactor core has a first region having a larger fuel diameter than that in a second region of the reactor core so as to achieve a low differential reflector reactivity at the central portion in the axial direction, and said first region being a region other than said second region being located from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to a place at substantially one half of the height thereof. 13. The fast reactor according to claim 1, wherein said reactor core has a first region having one of a higher ratio of fissile material to total amount of fissile material and non-fissile material, a higher fuel smear density, and a larger fuel diameter than that in a second region of the reactor core, and said first region being a region other than said second region being located from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to a place at substantially one half of the height thereof. 14. The fast reactor according to claim 1, wherein said reactor core has a first region having one of a ratio of fissile material to total amount of fissile and non-fissile material, a fuel smear density, and a fuel diameter, which is gradually increased in an upward direction, and said first region being a region from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to the top of the reactor core. 15. The fast reactor according to claim 1, wherein said reactor core has a first region having one of a higher ratio of fissile material to total amount of fissile and non-fissile material, a higher fuel smear density, and a larger fuel diameter than that in a second region of the reactor core, and said first region being a region other than the second region and being located between the top of the reactor core and substantially one half of the height thereof. 16. The fast reactor according to claim 1, wherein said reactor core includes first regions only or both first and second regions with minor actinides in the fuel at a high content than that in the other region, the first region being located from a place between substantially one tenth and one fifth of the height of the reactor core from the bottom end thereof to a place at substantially one half of the height thereof, the second region being located from the bottom of the reactor core to substantially one half of the height thereof. 17. The fast reactor according to claim 16, wherein said minor actinide is one of neptunium and americium. 18. The fast reactor according to claim 1, wherein said reactor core includes a minor actinide, and the content of the minor actinide is increased toward the bottom end of the reactor core except for a region from the bottom thereof to a place between substantially one tenth and one fifth of the height of the reactor core. 19. The fast reactor according to claim 18, wherein said minor actinide is one of neptunium and americium. 20. A fast reactor having a reflector control system, comprising:a reactor vessel which is filled with a liquid metal coolant;a reactor core including a fuel assembly, which is placed at a central position of the reactor vessel; anda neutron reflector including a region, which is placed at an upper side thereof, and at which a neutron absorber or a neutron transmitting material having a neutron reflection ability lower than that of the liquid metal coolant is placed and a reflection region which is placed at a lower side thereof and provided outside the reactor core so as to be moved in a vertical direction in an installed state of the fast reactor for adjusting leakage of neutrons from the reactor core so as to control a reactivity thereof,wherein said neutron reflector is moved in an upward direction in accordance with a change in reactivity caused by burn-up of a fuel, andwherein said fuel assembly includes a fuel pin bundle having fuel pins each having a fuel smear density placed in a wrapper tube and having an outermost fuel pin adjacent to the neutron reflector and a fuel pin placed at a further distance away from the neutron reflector, and, prior to neutron exposure in the reactor, the fuel smear density of the outermost fuel pin is smaller than the fuel smear density of the fuel pin placed at a farther distance away from the neutron reflector. 21. The fast reactor according to claim 1, wherein said fuel assembly includes a fuel pin facing the neutron reflector and a fuel pin placed at a distance from the neutron reflector, and a ratio of the fissile fuel to amount of fissile fuel and non-fissile fuel filled in the fuel pin facing the neutron reflector is changed in the axial direction. 22. The fast reactor according to claim 1, wherein said fuel assembly containing fuel pins, and the fuel pins each have a low fissile material region, an intermediate fissile material region, and a high fissile material region in that order from a coolant inlet side to a coolant outlet side. 23. The fast reactor according to claim 1, wherein said fuel assembly includes a fuel pin facing the neutron reflector and a fuel pin placed at a distance from the neutron reflector, and a fuel smear density of the fuel pin facing the neutron reflector is increased in the axial direction from a coolant inlet side to a coolant outlet side. 24. The fast reactor according to claim 1, wherein said neutron reflector comprises a structural member at a side facing the fuel assembly and a moderator at another side. 25. The fast reactor according to claim 1, wherein said neutron reflector comprises a structural member at an upper side in a lifting direction and a moderator at another side. 26. The fast reactor according to claim 1, wherein said reactor core further includes a neutron absorption assembly which is placed among the fuel assembly. 27. The fast reactor according to claim 26, wherein said neutron absorption assembly is disposed at the central position among the fuel assembly. 28. The fast reactor according to claim 26, wherein said neutron absorption assembly comprises a case member, a core shutdown rod placed at the central position of the case member, and a fixed absorber disposed outside of the core shutdown rod. 29. The fast reactor according to claim 26, wherein said neutron absorption assembly comprises a case member, a core shutdown rod placed at a central position of the case member, and a fixed absorber disposed outside of the core shutdown rod, and the solid absorber has a tube-shaped structure formed of a plurality of segments. 30. The fast reactor according to claim 29, wherein said segments include at least one comprising a structural member so as to adjust the reactivity of the fuel assembly. 31. The fast reactor according to claim 26, wherein said neutron absorption assembly comprises a case member, a core shutdown rod placed at the central position of the case member, and a fixed absorber disposed outside of the core shutdown rod, and the case member has a polygonal structure. 32. The fast reactor according to claim 1, wherein said reactor core further comprises a minor actinide annihilation assembly provided outside the fuel assembly. 33. The fast reactor according to claim 32, wherein said minor actinide annihilation assembly comprises a mixed portion of a high concentration moderator and a minor actinide, a mixed portion of a low concentration moderator and a minor actinide, and a minor actinide portion provided in that order from a side facing the fuel assembly to an external side. 34. The fast reactor according to claim 1, wherein:said fuel pin bundle has a first plurality of said fuel pins adjacent to the neutron reflector, a second plurality of fuel pins located at a first distance further away from said neutron reflector than said first plurality of fuel pins, and a third plurality of fuel pins located a second distance further away from said neutron reflector than said first distance;the ratio of the fissile fuel to amount of fissile fuel and non-fissile fuel filled in the first plurality of fuel pins is smaller than the ratio of the fissile fuel to amount of fissile fuel and non-fissile fuel filled in the second plurality of fuel pins; andthe ratio of the fissile fuel to total amount of the fissile fuel and the non-fissile fuel in the second plurality of fuel pins is smaller than the ratio of the fissile fuel to total amount of the fissile fuel and the non-fissile fuel in the third plurality of fuel pins. 35. The fast reactor according to claim 34, comprising:said second plurality of fuel pins being located adjacent to said first plurality of fuel pins, and said third plurality of fuel pins being located adjacent to said second plurality of fuel pins. 36. The fast reactor according to claim 20, wherein:said fuel pins are filled with a fissile fuel and a non-fissile fuel;said fuel pin bundle has a first plurality of said fuel pins adjacent to the neutron reflector, a second plurality of fuel pins located at a first distance further away from said neutron reflector than said first plurality of fuel pins, and a third plurality of fuel pins located a second distance further away from said neutron reflector than said first distance;the fuel smear density of the first plurality of fuel pins is smaller than the fuel smear density of the second plurality of fuel pins; andthe fuel smear density of the second plurality of fuel pins is smaller than the fuel smear density of the third plurality of fuel pins. 37. The fast reactor according to claim 36, comprising:said second plurality of fuel pins being located adjacent to said first plurality of fuel pins, and said third plurality of fuel pins being located adjacent to said second plurality of fuel pins.
	claims	1. A method of manufacturing an object having miniaturized structures, the method comprising:(a) processing the object bysupplying process gas to a surface of the object, anddirecting an electron beam to a processing location on the surface of the object; for at least one of depositing material on the object and ablating material from the object; and(b) inspecting the object byscanning the surface the object with the electron beam and supplying backscattered electrons and secondary electrons, generated by the scanning electron beam, to an energy selector,reflecting the secondary electrons at the energy selector,detecting backscattered electrons having traversed the energy selector, andgenerating an electron microscopic image of the scanned surface based on the detected backscattered electrons; and(c) performing one of(i) repeating the processing and the inspecting of the object, and(ii) stopping further processing and inspecting of the object,based on an analysis of the generated electron microscopic image of the object. 2. The method according to claim 1, wherein the energy selector comprises two grid electrodes disposed at a distance from each other, and wherein the reflecting of the secondary electrons comprises reflecting the secondary electrons by an electric field generated between the grid electrodes. 3. The method according to claim 1, wherein electrons of the electron beam have, at the surface of the object, a kinetic energy of less than 5 keV. 4. The method according to claim 1, further comprising supplying secondary electrons generated by the scanning electron beam, which are not supplied to the energy selector, to a secondary electron detector, and detecting the secondary electrons supplied to the secondary electron detector. 5. The method according to claim 1, further comprising generating a fourth vacuum in a space in which an electron detecting surface of the secondary electron detector is disposed, and generating a third vacuum in a space in which the energy selector is disposed, andmaintaining, during the processing of the object, a ratio of a gas pressure of the third vacuum and a gas pressure of the fourth vacuum of less than 1:2. 6. The method according to claim 5, further comprising generating a second vacuum in a space disposed between a space in which an electron beam source is disposed and the space in which the energy selector is disposed, generating a first vacuum in a space in which the electron beam source is disposed, andmaintaining, during the processing of the object,a ratio of a gas pressure of the first vacuum and a gas pressure of the second vacuum, anda ratio of the gas pressure of the second vacuum and a gas pressure of the third vacuum,to be each smaller than 1:10. 7. A processing system for inspecting and processing of an object having miniaturized structures, the electron microscopy system comprising:an electron beam source for generating an electron beam;a focussing lens for focussing the electron beam onto the object;a secondary electron detector disposed at a distance from the object;an energy selector disposed at a greater distance from the object than the secondary electron detector;a backscattered electron detector disposed at a greater distance from the object than the energy selector;a first vacuum space in which the electron beam source is disposed;a second vacuum space which is partially separated from the first vacuum space by a first separating structure comprising an aperture traversed by the electron beam;a third vacuum space in which the backscattered electron detector is disposed, wherein the third vacuum space is partially separated from the second vacuum space by a second separating structure (26) comprising an aperture traversed by the electron beam; anda fourth vacuum space in which a surface of the secondary electron detector is disposed, wherein the fourth vacuum space is partially separated from the third vacuum space by a third separating structure (27) comprising an aperture traversed by the electron beam. 8. The processing system according to claim 7, wherein the third separating structure comprises the secondary electron detector. 9. The processing system according to claim 7, wherein the energy selector is configured to separate secondary electrons and backscattered electrons from each other. 10. The processing system according to claim 9, wherein the energy selector is configured to reflect the secondary electrons. 11. The processing system according to claim 9, wherein the energy selector is configured such that only backscattered electrons having a kinetic energy above a predetermined threshold energy are allowed to reach at the backscattered electron detector. 12. The processing system according to claim 7, wherein the energy selector comprises two grid electrodes disposed at a distance from each other, and a voltage source for generating an electric field between the two grid electrodes. 13. The processing system according to claim 7, further comprising a gas supply arrangement for supplying a reaction gas to a surface of the object. 14. The processing system according to claim 7, further comprising first, second and third vacuum pumps,wherein a housing of the first vacuum space comprises an opening communicating with the first vacuum pump,wherein a housing of the second vacuum space comprises an opening communicating with the second vacuum pump,wherein a housing of the third vacuum space comprises an opening communicating with the third vacuum pump. 15. The processing system according to claim 7, further comprising a fifth vacuum space in which the object is disposed,wherein a housing of the fourth vacuum space comprises an opening not traversed by the electron beam,wherein a housing of the fifth vacuum space comprises an opening not traversed by the electron beam and communicating with the opening of the fourth vacuum space. 16. The processing system according to claim 15, further comprising a fourth vacuum pump different from the first, second and third vacuum pumps, wherein the housing of the fifth vacuum space comprises an opening communicating with the fourth vacuum pump. 17. The processing system according to claim 15, wherein the fifth vacuum space comprises an opening communicating with the third vacuum pump. 18. The processing system according to claim 7, wherein the electron microscopy system is configured such that, during operation,a ratio of a gas pressure in the first vacuum space and a gas pressure in the second vacuum space, anda ratio of the gas pressure in the second vacuum space and a gas pressure in the third vacuum space are each smaller than 1:10. 19. The processing system according to claim 7, wherein the electron microscopy system is further configured such that, during operation,a ratio of the gas pressure in the third vacuum space and a gas pressure in the fourth vacuum space is smaller than 1:2.
	description	This application is a divisional of and claims priority to U.S. patent application Ser. No. 15/997,819, filed on Jun. 5, 2018, and entitled “STORING HAZARDOUS MATERIAL IN A SUBTERRANEAN FORMATION,” which in turn claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application Ser. No. 62/515,050, filed on Jun. 5, 2017, and entitled “STORING HAZARDOUS MATERIAL IN A SUBTERRANEAN FORMATION.” The entire contents of each previous application are incorporated by reference herein. This disclosure relates to storing hazardous material in a subterranean formation and, more particularly, storing spent nuclear fuel in a subterranean formation. Hazardous waste is often placed in long-term, permanent, or semi-permanent storage so as to prevent health issues among a population living near the stored waste. Such hazardous waste storage is often challenging, for example, in terms of storage location identification and surety of containment. For instance, the safe storage of nuclear waste (e.g., spent nuclear fuel, whether from commercial power reactors, test reactors, or even high-grade military waste) is considered to be one of the outstanding challenges of energy technology. Safe storage of the long-lived radioactive waste is a major impediment to the adoption of nuclear power in the United States and around the world. Conventional waste storage methods have emphasized the use of tunnels, and is exemplified by the design of the Yucca Mountain storage facility. Other techniques include boreholes, including vertical boreholes, drilled into crystalline basement rock. Other conventional techniques include forming a tunnel with boreholes emanating from the walls of the tunnel in shallow formations to allow human access. In a general implementation, a hazardous material storage repository includes a drillhole extending into the Earth and including an entry at least proximate a terranean surface, the drillhole including a substantially vertical drillhole portion, a transition drillhole portion coupled to the substantially vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion, at least one of the transition drillhole portion or the hazardous material storage drillhole portion including an isolation drillhole portion that is directed vertically toward the terranean surface and away from an intersection between the substantially vertical drillhole portion and the transition drillhole portion; a storage canister positioned in the hazardous material storage drillhole portion, the storage canister sized to fit from the drillhole entry through the substantially vertical drillhole portion, the transition drillhole portion, and into the hazardous material storage drillhole portion of the drillhole, the storage canister including an inner cavity sized enclose hazardous material; and a seal positioned in the drillhole, the seal isolating the hazardous material storage drillhole portion of the drillhole from the entry of the drillhole. In an aspect combinable with the general implementation, the isolation drillhole portion includes a vertically inclined drillhole portion that includes a proximate end coupled to the transition drillhole portion at a first depth and a distal end opposite the proximate end at a second depth shallower than the first depth. In another aspect combinable with any of the previous aspects, the vertically inclined drillhole portion includes the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, an inclination angle of the vertically inclined drillhole portion is determined based at least in part on a distance associated with a disturbed zone of a geologic formation that surrounds the vertically inclined drillhole portion and a length of a distance tangent to a lowest portion of the storage canister and the substantially vertical drillhole portion. In another aspect combinable with any of the previous aspects, the distance associated with the disturbed zone of the geologic formation includes a distance between an outer circumference of the disturbed zone and a radial centerline of the vertically inclined drillhole portion. In another aspect combinable with any of the previous aspects, the inclination angle is about 3 degrees. In another aspect combinable with any of the previous aspects, the isolation drillhole portion includes a J-section drillhole portion coupled between the substantially vertical drillhole portion and the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, the J-section drillhole portion includes the transition drillhole portion. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion includes at least one of a substantially horizontal drillhole portion or a vertically inclined drillhole portion. In another aspect combinable with any of the previous aspects, the isolation drillhole portion includes a vertically undulating drillhole portion coupled to the transition drillhole portion. In another aspect combinable with any of the previous aspects, the transition drillhole portion includes a curved drillhole portion between the substantially vertical drillhole portion and the vertically undulating drillhole portion. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is located within or below a barrier layer that includes at least one of a shale formation layer, a salt formation layer, or other impermeable formation layer. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is vertically isolated, by the barrier layer, from a subterranean zone that includes mobile water. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is formed below the barrier layer and is vertically isolated from the subterranean zone that includes mobile water by the barrier layer. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is formed within the barrier layer, and is vertically isolated from the subterranean zone that includes mobile water by at least a portion of the barrier layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a permeability of less than about 0.01 millidarcys. In another aspect combinable with any of the previous aspects, the barrier layer includes a brittleness of less than about 10 MPa, where brittleness includes a ratio of compressive stress of the barrier layer to tensile strength of the barrier layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a thickness proximate the hazardous material storage drillhole portion of at least about 100 feet. In another aspect combinable with any of the previous aspects, the barrier layer includes a thickness proximate the hazardous material storage drillhole portion that inhibits diffusion of the hazardous material that escapes the storage canister through the barrier layer for an amount of time that is based on a half-life of the hazardous material. In another aspect combinable with any of the previous aspects, the barrier layer includes about 20 to 30% weight by volume of clay or organic matter. In another aspect combinable with any of the previous aspects, the barrier layer includes an impermeable layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a leakage barrier defined by a time constant for leakage of the hazardous material of 10,000 years or more. In another aspect combinable with any of the previous aspects, the barrier layer includes a hydrocarbon or carbon dioxide bearing formation. In another aspect combinable with any of the previous aspects, the hazardous material includes spent nuclear fuel. Another aspect combinable with any of the previous aspects further includes at least one casing assembly that extends from at or proximate the terranean surface, through the drillhole, and into the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, the storage canister includes a connecting portion configured to couple to at least one of a downhole tool string or another storage canister. In another aspect combinable with any of the previous aspects, the isolation drillhole portion includes a spiral drillhole. In another aspect combinable with any of the previous aspects, the isolation drillhole portion has a specified geometry independent of a stress state of a rock formation into which the isolation drillhole portion is formed. In another general implementation, a method for storing hazardous material includes moving a storage canister through an entry of a drillhole that extends into a terranean surface, the entry at least proximate the terranean surface, the storage canister including an inner cavity sized enclose hazardous material; moving the storage canister through the drillhole that includes a substantially vertical drillhole portion, a transition drillhole portion coupled to the substantially vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion, at least one of the transition drillhole portion or the hazardous material storage drillhole portion including an isolation drillhole portion that is directed vertically toward the terranean surface and away from an intersection between the substantially vertical drillhole portion and the transition drillhole portion; moving the storage canister into the hazardous material storage drillhole portion; and forming a seal in the drillhole that isolates the storage portion of the drillhole from the entry of the drillhole. In an aspect combinable with the general implementation, the isolation drillhole portion includes a vertically inclined drillhole portion that includes a proximate end coupled to the transition drillhole portion at a first depth and a distal end opposite the proximate end at a second depth shallower than the first depth. In another aspect combinable with any of the previous aspects, the vertically inclined drillhole portion includes the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, an inclination angle of the vertically inclined drillhole portion is determined based at least in part on a distance associated with a disturbed zone of a geologic formation that surrounds the vertically inclined drillhole portion and a length of a distance tangent to a lowest portion of the storage canister and the substantially vertical drillhole portion. In another aspect combinable with any of the previous aspects, the distance associated with the disturbed zone of the geologic formation includes a distance between an outer circumference of the disturbed zone and a radial centerline of the vertically inclined drillhole portion. In another aspect combinable with any of the previous aspects, the inclination angle is about 3 degrees. In another aspect combinable with any of the previous aspects, the isolation drillhole portion includes a J-section drillhole portion coupled between the substantially vertical drillhole portion and the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, the J-section drillhole portion includes the transition drillhole portion. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion includes at least one of a substantially horizontal drillhole portion or a vertically inclined drillhole portion. In another aspect combinable with any of the previous aspects, the isolation drillhole portion includes a vertically undulating drillhole portion coupled to the transition drillhole portion. In another aspect combinable with any of the previous aspects, the transition drillhole portion includes a curved drillhole portion between the substantially vertical drillhole portion and the vertically undulating drillhole portion. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is located within or below a barrier layer that includes at least one of a shale formation layer, a salt formation layer, or other impermeable formation layer. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is vertically isolated, by the barrier layer, from a subterranean zone that includes mobile water. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is formed below the barrier layer and is vertically isolated from the subterranean zone that includes mobile water by the barrier layer. In another aspect combinable with any of the previous aspects, the hazardous material storage drillhole portion is formed within the barrier layer, and is vertically isolated from the subterranean zone that includes mobile water by at least a portion of the barrier layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a permeability of less than about 0.01 millidarcys. In another aspect combinable with any of the previous aspects, the barrier layer includes a brittleness of less than about 10 MPa, where brittleness includes a ratio of compressive stress of the barrier layer to tensile strength of the barrier layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a thickness proximate the hazardous material storage drillhole portion of at least about 100 feet. In another aspect combinable with any of the previous aspects, the barrier layer includes a thickness proximate the hazardous material storage drillhole portion that inhibits diffusion of the hazardous material that escapes the storage canister through the barrier layer for an amount of time that is based on a half-life of the hazardous material. In another aspect combinable with any of the previous aspects, the barrier layer includes about 20 to 30% weight by volume of clay or organic matter. In another aspect combinable with any of the previous aspects, the barrier layer includes an impermeable layer. In another aspect combinable with any of the previous aspects, the barrier layer includes a leakage barrier defined by a time constant for leakage of the hazardous material of 10,000 years or more. In another aspect combinable with any of the previous aspects, the barrier layer includes a hydrocarbon or carbon dioxide bearing formation. In another aspect combinable with any of the previous aspects, the hazardous material includes spent nuclear fuel. Another aspect combinable with any of the previous aspects further includes at least one casing assembly that extends from at or proximate the terranean surface, through the drillhole, and into the hazardous material storage drillhole portion. In another aspect combinable with any of the previous aspects, the storage canister includes a connecting portion configured to couple to at least one of a downhole tool string or another storage canister. Another aspect combinable with any of the previous aspects further includes prior to moving the storage canister through the entry of the drillhole that extends into the terranean surface, forming the drillhole from the terranean surface to a subterranean formation. Another aspect combinable with any of the previous aspects further includes installing a casing in the drillhole that extends from at or proximate the terranean surface, through the drillhole, and into the hazardous material storage drillhole portion. Another aspect combinable with any of the previous aspects further includes cementing the casing to the drillhole. Another aspect combinable with any of the previous aspects further includes, subsequent to forming the drillhole, producing hydrocarbon fluid from the subterranean formation, through the drillhole, and to the terranean surface. Another aspect combinable with any of the previous aspects further includes removing the seal from the drillhole; and retrieving the storage canister from the hazardous material storage drillhole portion to the terranean surface. Another aspect combinable with any of the previous aspects further includes monitoring at least one variable associated with the storage canister from a sensor positioned proximate the hazardous material storage drillhole portion; and recording the monitored variable at the terranean surface. In another aspect combinable with any of the previous aspects, the monitored variable includes at least one of radiation level, temperature, pressure, presence of oxygen, presence of water vapor, presence of liquid water, acidity, or seismic activity. Another aspect combinable with any of the previous aspects further includes based on the monitored variable exceeding a threshold value removing the seal from the drillhole; and retrieving the storage canister from the hazardous material storage drillhole portion to the terranean surface. In another general implementation, a method for storing hazardous material includes moving a storage canister through an entry of a drillhole that extends into a terranean surface, the entry at least proximate the terranean surface, the storage canister including an inner cavity sized enclose hazardous material; moving the storage canister through the drillhole that includes a substantially vertical drillhole portion, a transition drillhole portion coupled to the substantially vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion, the hazardous material storage drillhole portion located below a self-healing geological formation, the hazardous material storage drillhole portion vertically isolated, by the self-healing geological formation, from a subterranean zone that includes mobile water; moving the storage canister into the hazardous material storage drillhole portion; and forming a seal in the drillhole that isolates the storage portion of the drillhole from the entry of the drillhole. In an aspect combinable with the general implementation, the self-healing geologic formation includes at least one of shale, salt, clay, or dolomite. In another general implementation, a hazardous material storage repository includes a drillhole extending into the Earth and including an entry at least proximate a terranean surface, the drillhole including a substantially vertical drillhole portion, a transition drillhole portion coupled to the substantially vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion, the hazardous material storage drillhole portion located below a self-healing geological formation, the hazardous material storage drillhole portion vertically isolated, by the self-healing geological formation, from a subterranean zone that includes mobile water; a storage canister positioned in the hazardous material storage drillhole portion, the storage canister sized to fit from the drillhole entry through the substantially vertical drillhole portion, the transition drillhole portion, and into the hazardous material storage drillhole portion of the drillhole, the storage canister including an inner cavity sized enclose hazardous material; and a seal positioned in the drillhole, the seal isolating the hazardous material storage drillhole portion of the drillhole from the entry of the drillhole. In an aspect combinable with the general implementation, the self-healing geologic formation includes at least one of shale, salt, clay, or dolomite. Implementations of a hazardous material storage repository according to the present disclosure may include one or more of the following features. For example, a hazardous material storage repository according to the present disclosure may allow for multiple levels of containment of hazardous material within a storage repository located thousands of feet underground, decoupled from any nearby mobile water. A hazardous material storage repository according to the present disclosure may also use proven techniques (e.g., drilling) to create or form a storage area for the hazardous material, in a subterranean zone proven to have fluidly sealed hydrocarbons therein for millions of years. As another example, a hazardous material storage repository according to the present disclosure may provide long-term (e.g., thousands of years) storage for hazardous material (e.g., radioactive waste) in a shale formation that has geologic properties suitable for such storage, including low permeability, thickness, and ductility, among others. In addition, a greater volume of hazardous material may be stored at low cost—relative to conventional storage techniques—due in part to directional drilling techniques that facilitate long horizontal boreholes, often exceeding a mile in length. In addition, rock formations that have geologic properties suitable for such storage may be found in close proximity to sites at which hazardous material may be found or generated, thereby reducing dangers associated with transporting such hazardous material. Implementations of a hazardous material storage repository according to the present disclosure may also include one or more of the following features. Large storage volumes, in turn, allow for the storage of hazardous materials to be emplaced without a need for complex prior treatment, such as concentration or transfer to different forms or canisters. As a further example, in the case of nuclear waste material from a reactor for instance, the waste can be kept in its original pellets, unmodified, or in its original fuel rods, or in its original fuel assemblies, which contain dozens of fuel rods. In another aspect, the hazardous material may be kept in an original holder but a cement or other material is injected into the holder to fill the gaps between the hazardous materials and the structure. For example, if the hazardous material is stored in fuel rods which are, in turn, stored in fuel assemblies, then the spaces between the rods (typically filled with water when inside a nuclear reactor) could be filled with cement or other material to provide yet an additional layer of isolation from the outside world. As yet a further example, secure and low cost storage of hazardous material is facilitated while still permitting retrieval of such material if circumstances deem it advantageous to recover the stored materials. The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. FIG. 1A is a schematic illustration of example implementations of a hazardous material storage repository system, e.g., a subterranean location for the long-term (e.g., tens, hundreds, or thousands of years or more) but retrievable safe and secure storage of hazardous material, during a deposit or retrieval operation according to the present disclosure. For example, turning to FIG. 1A, this figure illustrates an example hazardous material storage repository system 100 during a deposit (or retrieval, as described below) process, e.g., during deployment of one or more canisters of hazardous material in a subterranean formation. As illustrated, the hazardous material storage repository system 100 includes a drillhole 104 formed (e.g., drilled or otherwise) from a terranean surface 102 and through multiple subterranean layers 112, 114, 116, and 132. Although the terranean surface 102 is illustrated as a land surface, terranean surface 102 may be a sub-sea or other underwater surface, such as a lake or an ocean floor or other surface under a body of water. Thus, the present disclosure contemplates that the drillhole 104 may be formed under a body of water from a drilling location on or proximate the body of water. The illustrated drillhole 104 is a directional drillhole in this example of hazardous material storage repository system 100. For instance, the drillhole 104 includes a substantially vertical portion 106 coupled to a radiussed or curved portion 108, which in turn is coupled to an inclined portion 110. As used in the present disclosure, “substantially” in the context of a drillhole orientation, refers to drillholes that may not be exactly vertical (e.g., exactly perpendicular to the terranean surface 102) or exactly horizontal (e.g., exactly parallel to the terranean surface 102), or exactly inclined at a particular incline angle relative to the terranean surface 102. In other words, vertical drillholes often undulate offset from a true vertical direction, that they might be drilled at an angle that deviates from true vertical, and inclined drillholes often undulate offset from a true incline angle. Further, in some aspects, an inclined drillhole may not have or exhibit an exactly uniform incline (e.g., in degrees) over a length of the drillhole. Instead, the incline of the drillhole may vary over its length (e.g., by 1-5 degrees). As illustrated in this example, the three portions of the drillhole 104—the vertical portion 106, the radiussed portion 108, and the inclined portion 110—form a continuous drillhole 104 that extends into the Earth. The illustrated drillhole 104, in this example, has a surface casing 120 positioned and set around the drillhole 104 from the terranean surface 102 into a particular depth in the Earth. For example, the surface casing 120 may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the drillhole 104 in a shallow formation. As used herein, “tubular” may refer to a member that has a circular cross-section, elliptical cross-section, or other shaped cross-section. For example, in this implementation of the hazardous material storage repository system 100, the surface casing 120 extends from the terranean surface through a surface layer 112. The surface layer 112, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer 112 in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing 120 may isolate the drillhole 104 from such mobile water, and may also provide a hanging location for other casing strings to be installed in the drillhole 104. Further, although not shown, a conductor casing may be set above the surface casing 120 (e.g., between the surface casing 120 and the surface 102 and within the surface layer 112) to prevent drilling fluids from escaping into the surface layer 112. As illustrated, a production casing 122 is positioned and set within the drillhole 104 downhole of the surface casing 120. Although termed a “production” casing, in this example, the casing 122 may or may not have been subject to hydrocarbon production operations. Thus, the casing 122 refers to and includes any form of tubular member that is set (e.g., cemented) in the drillhole 104 downhole of the surface casing 120. In some examples of the hazardous material storage repository system 100, the production casing 122 may begin at an end of the radiussed portion 108 and extend throughout the inclined portion 110. The casing 122 could also extend into the radiussed portion 108 and into the vertical portion 106. As shown, cement 130 is positioned (e.g., pumped) around the casings 120 and 122 in an annulus between the casings 120 and 122 and the drillhole 104. The cement 130, for example, may secure the casings 120 and 122 (and any other casings or liners of the drillhole 104) through the subterranean layers under the terranean surface 102. In some aspects, the cement 130 may be installed along the entire length of the casings (e.g., casings 120 and 122 and any other casings), or the cement 130 could be used along certain portions of the casings if adequate for a particular drillhole 102. The cement 130 can also provide an additional layer of confinement for the hazardous material in canisters 126. The drillhole 104 and associated casings 120 and 122 may be formed with various example dimensions and at various example depths (e.g., true vertical depth, or TVD). For instance, a conductor casing (not shown) may extend down to about 120 feet TVD, with a diameter of between about 28 in. and 60 in. The surface casing 120 may extend down to about 2500 feet TVD, with a diameter of between about 22 in. and 48 in. An intermediate casing (not shown) between the surface casing 120 and production casing 122 may extend down to about 8000 feet TVD, with a diameter of between about 16 in. and 36 in. The production casing 122 may extend inclinedly (e.g., to case the inclined portion 110) with a diameter of between about 11 in. and 22 in. The foregoing dimensions are merely provided as examples and other dimensions (e.g., diameters, TVDs, lengths) are contemplated by the present disclosure. For example, diameters and TVDs may depend on the particular geological composition of one or more of the multiple subterranean layers (112, 114, 116, and 132), particular drilling techniques, as well as a size, shape, or design of a hazardous material canister 126 that contains hazardous material to be deposited in the hazardous material storage repository system 100. In some alternative examples, the production casing 122 (or other casing in the drillhole 104) could be circular in cross-section, elliptical in cross-section, or some other shape. As illustrated, the vertical portion 106 of the drillhole 104 extends through subterranean layers 112, 114, 116, and 132, and, in this example, lands in a subterranean layer 119. As discussed above, the surface layer 112 may or may not include mobile water. Subterranean layer 114, which is below the surface layer 112, in this example, is a mobile water layer 114. For instance, mobile water layer 114 may include one or more sources of mobile water, such as freshwater aquifers, salt water or brine, or other source of mobile water. In this example of hazardous material storage repository system 100, mobile water may be water that moves through a subterranean layer based on a pressure differential across all or a part of the subterranean layer. For example, the mobile water layer 114 may be a permeable geologic formation in which water freely moves (e.g., due to pressure differences or otherwise) within the layer 114. In some aspects, the mobile water layer 114 may be a primary source of human-consumable water in a particular geographic area. Examples of rock formations of which the mobile water layer 114 may be composed include porous sandstones and limestones, among other formations. Other illustrated layers, such as the impermeable layer 116 and the storage layer 119, may include immobile water. Immobile water, in some aspects, is water (e.g., fresh, salt, brine), that is not fit for human or animal consumption, or both. Immobile water, in some aspects, may be water that, by its motion through the layers 116 or 119 (or both), cannot reach the mobile water layer 114, terranean surface 102, or both, within 10,000 years or more (such as to 1,000,000 years). Below the mobile water layer 114, in this example implementation of hazardous material storage repository system 100, is an impermeable layer 116. The impermeable layer 116, in this example, may not allow mobile water to pass through. Thus, relative to the mobile water layer 114, the impermeable layer 116 may have low permeability, e.g., on the order of nanodarcy permeability. Additionally, in this example, the impermeable layer 116 may be a relatively non-ductile (i.e., brittle) geologic formation. One measure of non-ductility is brittleness, which is the ratio of compressive stress to tensile strength. In some examples, the brittleness of the impermeable layer 116 may be between about 20 MPa and 40 MPa. As shown in this example, the impermeable layer 116 is shallower (e.g., closer to the terranean surface 102) than the storage layer 119. In this example rock formations of which the impermeable layer 116 may be composed include, for example, certain kinds of sandstone, mudstone, clay, and slate that exhibit permeability and brittleness properties as described above. In alternative examples, the impermeable layer 116 may be deeper (e.g., further from the terranean surface 102) than the storage layer 119. In such alternative examples, the impermeable layer 116 may be composed of an igneous rock, such as granite. Below the impermeable layer 116 is the storage layer 119. The storage layer 119, in this example, may be chosen as the landing for the inclined portion 110, which stores the hazardous material, for several reasons. Relative to the impermeable layer 116 or other layers, the storage layer 119 may be thick, e.g., between about 100 and 200 feet of total vertical thickness. Thickness of the storage layer 119 may allow for easier landing and directional drilling, thereby allowing the inclined portion 110 to be readily emplaced within the storage layer 119 during constructions (e.g., drilling). If formed through an approximate horizontal center of the storage layer 119, the inclined portion 110 may be surrounded by about 50 to 100 feet of the geologic formation that comprises the storage layer 119. Further, the storage layer 119 may also have only immobile water, e.g., due to a very low permeability of the layer 119 (e.g., on the order of milli- or nanodarcys). In addition, the storage layer 119 may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer 119 is between about 3 MPa and 10 MPa. Examples of rock formations of which the storage layer 119 may be composed include: shale and anhydrite. Further, in some aspects, hazardous material may be stored below the storage layer, even in a permeable formation such as sandstone or limestone, if the storage layer is of sufficient geologic properties to isolate the permeable layer from the mobile water layer 114. In some examples implementations of the hazardous material storage repository system 100, the storage layer 119 (and/or the impermeable layer 116) is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer 119. For example, shale formations may be suitable for a long-term confinement of hazardous material (e.g., in the hazardous material canisters 126), and for their isolation from mobile water layer 114 (e.g., aquifers) and the terranean surface 102. Shale formations may be found relatively deep in the Earth, typically 3000 feet or greater, and placed in isolation below any fresh water aquifers. Other formations may include salt or other impermeable formation layer. Shale formations (or salt or other impermeable formation layers), for instance, may include geologic properties that enhance the long-term (e.g., thousands of years) isolation of material. Such properties, for instance, have been illustrated through the long term storage (e.g., tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid, mixed phase fluid) without escape of substantial fractions of such fluids into surrounding layers (e.g., mobile water layer 114). Indeed, shale has been shown to hold natural gas for millions of years or more, giving it a proven capability for long-term storage of hazardous material. Example shale formations (e.g., Marcellus, Eagle Ford, Barnett, and otherwise) has stratification that contains many redundant sealing layers that have been effective in preventing movement of water, oil, and gas for millions of years, lacks mobile water, and can be expected (e.g., based on geological considerations) to seal hazardous material (e.g., fluids or solids) for thousands of years after deposit. In some aspects, the formation of the storage layer 119 and/or the impermeable layer 116 may form a leakage barrier, or barrier layer to fluid leakage that may be determined, at least in part, by the evidence of the storage capacity of the layer for hydrocarbons or other fluids (e.g., carbon dioxide) for hundreds of years, thousands of years, tens of thousands of years, hundreds of thousands of years, or even millions of years. For example, the barrier layer of the storage layer 119 and/or impermeable layer 116 may be defined by a time constant for leakage of the hazardous material more than 10,000 years (such as between about 10,000 years and 1,000,000 years) based on such evidence of hydrocarbon or other fluid storage. Shale (or salt or other impermeable layer) formations may also be at a suitable depth, e.g., between 3000 and 12,000 feet TVD. Such depths are typically below ground water aquifer (e.g., surface layer 112 and/or mobile water layer 114). Further, the presence of soluble elements in shale, including salt, and the absence of these same elements in aquifer layers, demonstrates a fluid isolation between shale and the aquifer layers. Another particular quality of shale that may advantageously lend itself to hazardous material storage is its clay content, which, in some aspects, provides a measure of ductility greater than that found in other, impermeable rock formations (e.g., impermeable layer 116). For example, shale may be stratified, made up of thinly alternating layers of clays (e.g., between about 20-30% clay by volume) and other minerals. Such a composition may make shale less brittle and, thus less susceptible to fracturing (e.g., naturally or otherwise) as compared to rock formations in the impermeable layer (e.g., dolomite or otherwise). For example, rock formations in the impermeable layer 116 may have suitable permeability for the long term storage of hazardous material, but are too brittle and commonly are fractured. Thus, such formations may not have sufficient sealing qualities (as evidenced through their geologic properties) for the long term storage of hazardous material. The present disclosure contemplates that there may be many other layers between or among the illustrated subterranean layers 112, 114, 116, and 119. For example, there may be repeating patterns (e.g., vertically), of one or more of the mobile water layer 114, impermeable layer 116, and storage layer 119. Further, in some instances, the storage layer 119 may be directly adjacent (e.g., vertically) the mobile water layer 114, i.e., without an intervening impermeable layer 116. In some examples, all or portions of the radiussed drillhole 108 and the inclined drillhole 110 may be formed below the storage layer 119, such that the storage layer 119 (e.g., shale or other geologic formation with characteristics as described herein) is vertically positioned between the inclined drillhole 110 and the mobile water layer 114. Further, in this example implementation, a self-healing layer 132 may be found below the terranean surface 102 and between, for example, the surface 102 and one or both of the impermeable layer 116 and the storage layer 119. In some aspects, the self-healing layer 132 may comprise a geologic formation that can stop or impede a flow of hazardous material (whether in liquid, solid, or gaseous form) from a storage portion of the drillhole 104 to or toward the terranean surface 102. For example, during formation of the drillhole 104 (e.g., drilling), all are portions of the geologic formations of the layers 112, 114, 116, and 119, may be damaged (as illustrated by a damaged zone 140), thereby affecting or changing their geologic characteristics (e.g., permeability). Indeed, although damaged zone 140 is illustrated between layers 114 and 132 for simplicity sake, the damaged zone 140 may surround an entire length (vertical, curved, and inclined portions) of the drillhole 104 a particular distance into the layers 112, 114, 116, 119, 132, and otherwise. In certain aspects, the location of the drillhole 104 may be selected so as to be formed through the self-healing layer 132. For example, as shown, the drillhole 104 may be formed such that at least a portion of the vertical portion 106 of the drillhole 104 is formed to pass through the self-healing layer 132. In some aspects, the self-healing layer 132 comprises a geologic formation that that does not sustain cracks for extended time durations even after being drilled therethrough. Examples of the geologic formation in the self-healing layer 132 include clay or dolomite. Cracks in such rock formations tend to heal, that is, they disappear rapidly with time due to the relative ductility of the material, and the enormous pressures that occur underground from the weight of the overlying rock on the formation in the self-healing layer. In addition to providing a “healing mechanism” for cracks that occur due to the formation of the drillhole 104 (e.g., drilling or otherwise), the self-healing layer 132 may also provide a barrier to natural faults and other cracks that otherwise could provide a pathway for hazardous material leakage (e.g., fluid or solid) from the storage region (e.g., in the inclined portion 110) to the terranean surface 102, the mobile water layer 114, or both. As shown in this example, the inclined portion 110 of the drillhole 104 includes a storage area 117 in a distal part of the portion 110 into which hazardous material may be retrievably placed for long-term storage. For example, as shown, a work string 124 (e.g., tubing, coiled tubing, wireline, or otherwise) may be extended into the cased drillhole 104 to place one or more (three shown but there may be more or less) hazardous material canisters 126 into long term, but in some aspects, retrievable, storage in the portion 110. For example, in the implementation shown in FIG. 1A, the work string 124 may include a downhole tool 128 that couples to the canister 126, and with each trip into the drillhole 104, the downhole tool 128 may deposit a particular hazardous material canister 126 in the inclined portion 110. The downhole tool 128 may couple to the canister 126 by, in some aspects, a threaded connection or other type of connection, such as a latched connection. In alternative aspects, the downhole tool 128 may couple to the canister 126 with an interlocking latch, such that rotation (or linear movement or electric or hydraulic switches) of the downhole tool 128 may latch to (or unlatch from) the canister 126. In alternative aspects, the downhole tool 124 may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to the canister 126. In some examples, the canister 126 may also include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) of an opposite polarity as the magnets on the downhole tool 124. In some examples, the canister 126 may be made from or include a ferrous or other material attractable to the magnets of the downhole tool 124. As another example, each canister 126 may be positioned within the drillhole 104 by a drillhole tractor (e.g., on a wireline or otherwise), which may push or pull the canister into the inclined portion 110 through motorized (e.g., electric) motion. As yet another example, each canister 126 may include or be mounted to rollers (e.g., wheels), so that the downhole tool 124 may push the canister 126 into the cased drillhole 104. In some example implementations, the canister 126, one or more of the drillhole casings 120 and 122, or both, may be coated with a friction-reducing coating prior to the deposit operation. For example, by applying a coating (e.g., petroleum-based product, resin, ceramic, or otherwise) to the canister 126 and/or drillhole casings, the canister 126 may be more easily moved through the cased drillhole 104 into the inclined portion 110. In some aspects, only a portion of the drillhole casings may be coated. For example, in some aspects, the substantially vertical portion 106 may not be coated, but the radiussed portion 108 or the inclined portion 110, or both, may be coated to facilitate easier deposit and retrieval of the canister 126. FIG. 1A also illustrates an example of a retrieval operation of hazardous material in the inclined portion 110 of the drillhole 104. A retrieval operation may be the opposite of a deposit operation, such that the downhole tool 124 (e.g., a fishing tool) may be run into the drillhole 104, coupled to the last-deposited canister 126 (e.g., threadingly, latched, by magnet, or otherwise), and pull the canister 126 to the terranean surface 102. Multiple retrieval trips may be made by the downhole tool 124 in order to retrieve multiple canisters from the inclined portion 110 of the drillhole 104. Each canister 126 may enclose hazardous material. Such hazardous material, in some examples, may be biological or chemical waste or other biological or chemical hazardous material. In some examples, the hazardous material may include nuclear material, such as spent nuclear fuel recovered from a nuclear reactor (e.g., commercial power or test reactor) or military nuclear material. For example, a gigawatt nuclear plant may produce 30 tons of spent nuclear fuel per year. The density of that fuel is typically close to 10 (10 gm/cm3=10 kg/liter), so that the volume for a year of nuclear waste is about 3 m3. Spent nuclear fuel, in the form of nuclear fuel pellets, may be taken from the reactor and not modified. Nuclear fuel pellet are solid, although they can contain and emit a variety of radioactive gases including tritium (13 year half-life), krypton-85 (10.8 year half-life), and carbon dioxide containing C-14 (5730 year half-life). In some aspects, the storage layer 119 should be able to contain any radioactive output (e.g., gases) within the layer 119, even if such output escapes the canisters 126. For example, the storage layer 119 may be selected based on diffusion times of radioactive output through the layer 119. For example, a minimum diffusion time of radioactive output escaping the storage layer 119 may be set at, for example, fifty times a half-life for any particular component of the nuclear fuel pellets. Fifty half-lives as a minimum diffusion time would reduce an amount of radioactive output by a factor of 1×10−15. As another example, setting a minimum diffusion time to thirty half-lives would reduce an amount of radioactive output by a factor of one billion. For example, plutonium-239 is often considered a dangerous waste product in spent nuclear fuel because of its long half-life of 24,100 years. For this isotope, 50 half-lives would be 1.2 million years. Plutonium-239 has low solubility in water, is not volatile, and as a solid. its diffusion time is exceedingly small (e.g., many millions of years) through a matrix of the rock formation that comprises the illustrated storage layer 119 (e.g., shale or other formation). The storage layer 119, for example comprised of shale, may offer the capability to have such isolation times (e.g., millions of years) as shown by the geological history of containing gaseous hydrocarbons (e.g., methane and otherwise) for several million years. In contrast, in conventional nuclear material storage methods, there was a danger that some plutonium might dissolve in a layer that comprised mobile ground water upon confinement escape. As further shown in FIG. 1A, the storage canisters 126 may be positioned for long term storage in the inclined portion 110, which, as shown, is tilted upward at a small angle (e.g., 2-5 degrees) as it gets further away from the vertical portion 106 of the drillhole 104. As illustrated, the inclined portion 110 tilts upward toward the terranean surface 102. In some aspects, for example when there is radioactive hazardous material stored in the canisters 126, the inclination of the drillhole portion 110 may provide a further degree of safety and containment to prevent or impede the material, even if leaked from the canister 126, from reaching, e.g., the mobile water layer 114, the vertical portion 106 of the drillhole 104, the terranean surface 102, or a combination thereof. For example, radionuclides of concern in the hazardous material tend to be relatively buoyant or heavy (as compared to brine or other fluids that might fill the drillhole). Buoyant radionuclides may be the greatest concern for leakage, since heavy elements and molecules tend to sink, and would not diffuse upward towards the terranean surface 102. Krypton gas, and particularly 14CO2 (where 14C refers to radiocarbon, also called C-14, which is an isotope of carbon with a half-life of 5730 years), is a buoyant radioactive element that is heavier than air (as are most gases) but much lighter than water. Thus, should 14CO2 be introduced into a water bath, such gas would tend to float upward towards the terranean surface 102. Iodine, on the other hand, is denser than water, and would tend to diffuse downward if introduced into a water bath. By including the inclined portion 110 of the drillhole 104, any such diffusion of radioactive material (e.g., even if leaked from a canister 126 and in the presence of water or other liquid in the drillhole 104 or otherwise) would be directed angularly upward toward a distal end 121 of the inclined portion 110 and away from the radiussed portion 108 (and the vertical portion 106) of the drillhole 104. Thus, leaked hazardous material, even in a diffusible gas form, would not be offered a path (e.g., directly) to the terranean surface 102 (or the mobile water layer 114) through the vertical portion 106 of the drillhole 110. For instance, the leaked hazardous material (especially in gaseous form) would be directed and gathered at the distal end 121 of the drillhole portion 110. Alternative methods of depositing the canisters 126 into the inclined drillhole portion 110 may also be implemented. For instance, a fluid (e.g., liquid or gas) may be circulated through the drillhole 104 to fluidly push the canisters 126 into the inclined drillhole portion 110. In some example, each canister 126 may be fluidly pushed separately. In alternative aspects, two or more canisters 126 may be fluidly pushed, simultaneously, through the drillhole 104 for deposit into the inclined portion 110. The fluid can be, in some cases, water. Other examples include a drilling mud or drilling foam. In some examples, a gas may be used to push the canisters 126 into the drillhole, such as air, argon, or nitrogen. In some aspects, the choice of fluid may depend at least in part on a viscosity of the fluid. For example, a fluid may be chosen with enough viscosity to impede the drop of the canister 126 into the substantially vertical portion 106. This resistance or impedance may provide a safety factor against a sudden drop of the canister 126. The fluid may also provide lubrication to reduce a sliding friction between the canister 126 and the casings 120 and 122. The canister 126 can be conveyed within a casing filled with a liquid of controlled viscosity, density, and lubricant qualities. The fluid-filled annulus between the inner diameter of the casings 120 and 122 and the outer diameter of the conveyed canister 126 represents an opening designed to dampen any high rate of canister motion, providing automatic passive protection in an unlikely decoupling of the conveyed canister 126. In some aspects, other techniques may be employed to facilitate deposit of the canister 126 into the inclined portion 110. For example, one or more of the installed casings (e.g., casings 120 and 122) may have rails to guide the storage canister 126 into the drillhole 102 while reducing friction between the casings and the canister 126. The storage canister 126 and the casings (or the rails) may be made of materials that slide easily against one another. The casings may have a surface that is easily lubricated, or one that is self-lubricating when subjected to the weight of the storage canister 126. The fluid may also be used for retrieval of the canister 126. For example, in an example retrieval operation, a volume within the casings 120 and 122 may be filled with a compressed gas (e.g., air, nitrogen, argon, or otherwise). As the pressure increases at an end of the inclined portion 110, the canisters 126 may be pushed toward the radiussed portion 108, and subsequently through the substantially vertical portion 106 to the terranean surface. In some aspects, the drillhole 104 may be formed for the primary purpose of long-term storage of hazardous materials. In alternative aspects, the drillhole 104 may have been previously formed for the primary purpose of hydrocarbon production (e.g., oil, gas). For example, storage layer 119 may be a hydrocarbon bearing formation from which hydrocarbons were produced into the drillhole 104 and to the terranean surface 102. In some aspects, the storage layer 119 may have been hydraulically fractured prior to hydrocarbon production. Further in some aspects, the production casing 122 may have been perforated prior to hydraulic fracturing. In such aspects, the production casing 122 may be patched (e.g., cemented) to repair any holes made from the perforating process prior to a deposit operation of hazardous material. In addition, any cracks or openings in the cement between the casing and the drillhole can also be filled at that time. For example, in the case of spent nuclear fuel as a hazardous material, the drillhole may be formed at a particular location, e.g., near a nuclear power plant, as a new drillhole provided that the location also includes an appropriate storage layer 119, such as a shale formation. Alternatively, an existing well that has already produced shale gas, or one that was abandoned as “dry,” (e.g., with sufficiently low organics that the gas in place is too low for commercial development), may be selected as the drillhole 104. In some aspects, prior hydraulic fracturing of the storage layer 119 through the drillhole 104 may make little difference in the hazardous material storage capability of the drillhole 104. But such a prior activity may also confirm the ability of the storage layer 119 to store gases and other fluids for millions of years. If, therefore, the hazardous material or output of the hazardous material (e.g., radioactive gasses or otherwise) were to escape from the canister 126 and enter the fractured formation of the storage layer 119, such fractures may allow that material to spread relatively rapidly over a distance comparable in size to that of the fractures. In some aspects, the drillhole 102 may have been drilled for a production of hydrocarbons, but production of such hydrocarbons had failed, e.g., because the storage layer 119 comprised a rock formation (e.g., shale or otherwise) that was too ductile and difficult to fracture for production, but was advantageously ductile for the long-term storage of hazardous material. FIG. 1B is a schematic illustration of a portion of the example implementation of the hazardous material storage repository system 100 that shows an example determination of a minimum angle of the inclined portion 110 of the hazardous material storage repository system 100. For example, as shown in system 100, the inclined portion 110 provides that any path that leaking hazardous material (e.g., from one or more of the canister 126) takes to the terranean surface 102 through the drillhole 104 includes at least one downward component. In this case, the inclined portion 110 is the downward component. In other example implementations described later, such as systems 200 and 300, other portions (e.g., a J-section portion or undulating portion) may include at least one downward component. Such paths, as shown in this example, dip below a horizontal escape limit line 175 that intersects a canister 126 that is closest (when positioned in the storage area 117) to the vertical portion 106 of the drillhole 104. and therefore must include a downward component. In some aspects, an angle, a, of the inclined portion 110 of the drillhole 104 may be determined (and thereby guide the formation of the drillhole 104) according to a radius, R, of the damaged zone 140 of the drillhole 104 and a distance, D, from the canister 126 that is closest to the vertical portion 106 of the drillhole 104. As shown in the callout bubble in FIG. 1B, with knowledge of the distances R and D (or at least estimates), then the angle, a, can be computed according to the arctangent of R/D. In an example implementation, R may be about 1 meter while D may be about 20 meters. The angle, a, therefore, as the arctangent of R/D is about 3°. This is just one example of the determination of the angle, a, of a downward component (e.g., the inclined portion 110) of the drillhole 104 to ensure that such a downward component dips below the horizontal escape limit line 175. FIG. 2 is a schematic illustration of example implementations of another hazardous material storage repository system, e.g., a subterranean location for the long-term (e.g., tens, hundreds, or thousands of years or more) but retrievable safe and secure storage of hazardous material, during a deposit or retrieval operation according to the present disclosure. For example, turning to FIG. 2, this figure illustrates an example hazardous material storage repository system 200 during a deposit (or retrieval, as described below) process, e.g., during deployment of one or more canisters of hazardous material in a subterranean formation. As illustrated, the hazardous material storage repository system 200 includes a drillhole 204 formed (e.g., drilled or otherwise) from a terranean surface 202 and through multiple subterranean layers 212, 214, and 216. Although the terranean surface 202 is illustrated as a land surface, terranean surface 202 may be a sub-sea or other underwater surface, such as a lake or an ocean floor or other surface under a body of water. Thus, the present disclosure contemplates that the drillhole 204 may be formed under a body of water from a drilling location on or proximate the body of water. The illustrated drillhole 204 is a directional drillhole in this example of hazardous material storage repository system 200. For instance, the drillhole 204 includes a substantially vertical portion 206 coupled to a J-section portion 208, which in turn is coupled to a substantially horizontal portion 210. The J-section portion 208 as shown, has a shape that resembles the bottom portion of the letter “J” and may be shaped similar to a p-trap device used in a plumbing system that is used to prevent gasses from migrating from one side of the bend to the other side of the bend. As used in the present disclosure, “substantially” in the context of a drillhole orientation, refers to drillholes that may not be exactly vertical (e.g., exactly perpendicular to the terranean surface 202) or exactly horizontal (e.g., exactly parallel to the terranean surface 202), or exactly inclined at a particular incline angle relative to the terranean surface 202. In other words, vertical drillholes often undulate offset from a true vertical direction, that they might be drilled at an angle that deviates from true vertical, and horizontal drillholes often undulate offset from exactly horizontal. As illustrated in this example, the three portions of the drillhole 204—the vertical portion 206, the J-section portion 208, and the substantially horizontal portion 210—form a continuous drillhole 204 that extends into the Earth. As also shown in dashed line in FIG. 2, the J-section portion 208 may be coupled to an inclined portion 240 rather than (or in addition to) the substantially horizontal portion 210 of the drillhole 204. The illustrated drillhole 204, in this example, has a surface casing 220 positioned and set around the drillhole 204 from the terranean surface 202 into a particular depth in the Earth. For example, the surface casing 220 may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the drillhole 204 in a shallow formation. As used herein, “tubular” may refer to a member that has a circular cross-section, elliptical cross-section, or other shaped cross-section. For example, in this implementation of the hazardous material storage repository system 200, the surface casing 220 extends from the terranean surface through a surface layer 212. The surface layer 212, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer 212 in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing 220 may isolate the drillhole 204 from such mobile water, and may also provide a hanging location for other casing strings to be installed in the drillhole 204. Further, although not shown, a conductor casing may be set above the surface casing 220 (e.g., between the surface casing 220 and the surface 202 and within the surface layer 212) to prevent drilling fluids from escaping into the surface layer 212. As illustrated, a production casing 222 is positioned and set within the drillhole 204 downhole of the surface casing 220. Although termed a “production” casing, in this example, the casing 222 may or may not have been subject to hydrocarbon production operations. Thus, the casing 222 refers to and includes any form of tubular member that is set (e.g., cemented) in the drillhole 204 downhole of the surface casing 220. In some examples of the hazardous material storage repository system 200, the production casing 222 may begin at an end of the J-section portion 208 and extend throughout the substantially horizontal portion 210. The casing 222 could also extend into the J-section portion 208 and into the vertical portion 206. As shown, cement 230 is positioned (e.g., pumped) around the casings 220 and 222 in an annulus between the casings 220 and 222 and the drillhole 204. The cement 230, for example, may secure the casings 220 and 222 (and any other casings or liners of the drillhole 204) through the subterranean layers under the terranean surface 202. In some aspects, the cement 230 may be installed along the entire length of the casings (e.g., casings 220 and 222 and any other casings), or the cement 230 could be used along certain portions of the casings if adequate for a particular drillhole 202. The cement 230 can also provide an additional layer of confinement for the hazardous material in canisters 226. The drillhole 204 and associated casings 220 and 222 may be formed with various example dimensions and at various example depths (e.g., true vertical depth, or TVD). For instance, a conductor casing (not shown) may extend down to about 120 feet TVD, with a diameter of between about 28 in. and 60 in. The surface casing 220 may extend down to about 2500 feet TVD, with a diameter of between about 22 in. and 48 in. An intermediate casing (not shown) between the surface casing 220 and production casing 222 may extend down to about 8000 feet TVD, with a diameter of between about 16 in. and 36 in. The production casing 222 may extend inclinedly (e.g., to case the substantially horizontal portion 210 and/or the inclined portion 240) with a diameter of between about 11 in. and 22 in. The foregoing dimensions are merely provided as examples and other dimensions (e.g., diameters, TVDs, lengths) are contemplated by the present disclosure. For example, diameters and TVDs may depend on the particular geological composition of one or more of the multiple subterranean layers (212, 214, and 216), particular drilling techniques, as well as a size, shape, or design of a hazardous material canister 226 that contains hazardous material to be deposited in the hazardous material storage repository system 200. In some alternative examples, the production casing 222 (or other casing in the drillhole 204) could be circular in cross-section, elliptical in cross-section, or some other shape. As illustrated, the vertical portion 206 of the drillhole 204 extends through subterranean layers 212, 214, and 216, and, in this example, lands in a subterranean layer 219. As discussed above, the surface layer 212 may or may not include mobile water. Subterranean layer 214, which is below the surface layer 212, in this example, is a mobile water layer 214. For instance, mobile water layer 214 may include one or more sources of mobile water, such as freshwater aquifers, salt water or brine, or other source of mobile water. In this example of hazardous material storage repository system 200, mobile water may be water that moves through a subterranean layer based on a pressure differential across all or a part of the subterranean layer. For example, the mobile water layer 214 may be a permeable geologic formation in which water freely moves (e.g., due to pressure differences or otherwise) within the layer 214. In some aspects, the mobile water layer 214 may be a primary source of human-consumable water in a particular geographic area. Examples of rock formations of which the mobile water layer 214 may be composed include porous sandstones and limestones, among other formations. Other illustrated layers, such as the impermeable layer 216 and the storage layer 219, may include immobile water. Immobile water, in some aspects, is water (e.g., fresh, salt, brine), that is not fit for human or animal consumption, or both. Immobile water, in some aspects, may be water that, by its motion through the layers 216 or 219 (or both), cannot reach the mobile water layer 214, terranean surface 202, or both, within 10,000 years or more (such as to 1,000,000 years). Below the mobile water layer 214, in this example implementation of hazardous material storage repository system 200, is an impermeable layer 216. The impermeable layer 216, in this example, may not allow mobile water to pass through. Thus, relative to the mobile water layer 214, the impermeable layer 216 may have low permeability, e.g., on the order of 0.01 millidarcy permeability. Additionally, in this example, the impermeable layer 216 may be a relatively non-ductile (i.e., brittle) geologic formation. One measure of non-ductility is brittleness, which is the ratio of compressive stress to tensile strength. In some examples, the brittleness of the impermeable layer 216 may be between about 20 MPa and 40 MPa. As shown in this example, the impermeable layer 216 is shallower (e.g., closer to the terranean surface 202) than the storage layer 219. In this example rock formations of which the impermeable layer 216 may be composed include, for example, certain kinds of sandstone, mudstone, clay, and slate that exhibit permeability and brittleness properties as described above. In alternative examples, the impermeable layer 216 may be deeper (e.g., further from the terranean surface 202) than the storage layer 219. In such alternative examples, the impermeable layer 216 may be composed of an igneous rock, such as granite. Below the impermeable layer 216 is the storage layer 219. The storage layer 219, in this example, may be chosen as the landing for the substantially horizontal portion 210, which stores the hazardous material, for several reasons. Relative to the impermeable layer 216 or other layers, the storage layer 219 may be thick, e.g., between about 100 and 200 feet of total vertical thickness. Thickness of the storage layer 219 may allow for easier landing and directional drilling, thereby allowing the substantially horizontal portion 210 to be readily emplaced within the storage layer 219 during constructions (e.g., drilling). If formed through an approximate horizontal center of the storage layer 219, the substantially horizontal portion 210 may be surrounded by about 50 to 100 feet of the geologic formation that comprises the storage layer 219. Further, the storage layer 219 may also have only immobile water, e.g., due to a very low permeability of the layer 219 (e.g., on the order of milli- or nanodarcys). In addition, the storage layer 219 may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer 219 is between about 3 MPa and 10 MPa. Examples of rock formations of which the storage layer 219 may be composed include: shale and anhydrite. Further, in some aspects, hazardous material may be stored below the storage layer, even in a permeable formation such as sandstone or limestone, if the storage layer is of sufficient geologic properties to isolate the permeable layer from the mobile water layer 214. In some examples implementations of the hazardous material storage repository system 200, the storage layer 219 (and/or the impermeable layer 216) is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer 219. For example, shale formations may be suitable for a long-term confinement of hazardous material (e.g., in the hazardous material canisters 226), and for their isolation from mobile water layer 214 (e.g., aquifers) and the terranean surface 202. Shale formations may be found relatively deep in the Earth, typically 3000 feet or greater, and placed in isolation below any fresh water aquifers. Other formations may include salt or other impermeable formation layer. Shale formations (or salt or other impermeable formation layers), for instance, may include geologic properties that enhance the long-term (e.g., thousands of years) isolation of material. Such properties, for instance, have been illustrated through the long term storage (e.g., tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid, mixed phase fluid) without escape of such fluids into surrounding layers (e.g., mobile water layer 214). Indeed, shale has been shown to hold natural gas for millions of years or more, giving it a proven capability for long-term storage of hazardous material. Example shale formations (e.g., Marcellus, Eagle Ford, Barnett, and otherwise) has stratification that contains many redundant sealing layers that have been effective in preventing movement of water, oil, and gas for millions of years, lacks mobile water, and can be expected (e.g., based on geological considerations) to seal hazardous material (e.g., fluids or solids) for thousands of years after deposit. In some aspects, the formation of the storage layer 219 and/or the impermeable layer 216 may form a leakage barrier, or barrier layer to fluid leakage that may be determined, at least in part, by the evidence of the storage capacity of the layer for hydrocarbons or other fluids (e.g., carbon dioxide) for hundreds of years, thousands of years, tens of thousands of years, hundreds of thousands of years, or even millions of years. For example, the barrier layer of the storage layer 219 and/or impermeable layer 216 may be defined by a time constant for leakage of the hazardous material of more than 10,000 years (such as between 10,000 years and 1,000,000 years) based on such evidence of hydrocarbon or other fluid storage. Shale (or salt or other impermeable layer) formations may also be at a suitable depth, e.g., between 3000 and 12,000 feet TVD. Such depths are typically below ground water aquifer (e.g., surface layer 212 and/or mobile water layer 214). Further, the presence of soluble elements in shale, including salt, and the absence of these same elements in aquifer layers, demonstrates a fluid isolation between shale and the aquifer layers. Another particular quality of shale that may advantageously lend itself to hazardous material storage is its clay content, which, in some aspects, provides a measure of ductility greater than that found in other, impermeable rock formations (e.g., impermeable layer 216). For example, shale may be stratified, made up of thinly alternating layers of clays (e.g., between about 20-30% clay by volume) and other minerals. Such a composition may make shale less brittle and, thus less susceptible to fracturing (e.g., naturally or otherwise) as compared to rock formations in the impermeable layer (e.g., dolomite or otherwise). For example, rock formations in the impermeable layer 216 may have suitable permeability for the long term storage of hazardous material, but are too brittle and commonly are fractured. Thus, such formations may not have sufficient sealing qualities (as evidenced through their geologic properties) for the long term storage of hazardous material. The present disclosure contemplates that there may be many other layers between or among the illustrated subterranean layers 212, 214, 216, and 219. For example, there may be repeating patterns (e.g., vertically), of one or more of the mobile water layer 214, impermeable layer 216, and storage layer 219. Further, in some instances, the storage layer 219 may be directly adjacent (e.g., vertically) the mobile water layer 214, i.e., without an intervening impermeable layer 216. In some examples, all or portions of the J-section drillhole 208 and the substantially horizontal portion 210 (and/or the inclined portion 240) may be formed below the storage layer 219, such that the storage layer 219 (e.g., shale or other geologic formation with characteristics as described herein) is vertically positioned between the substantially horizontal portion 210 (and/or the inclined portion 240) and the mobile water layer 214. Although not illustrated in this particular example shown in FIG. 2, a self-healing layer (e.g., such as the self-healing layer 132) may be found below the terranean surface 202 and between, for example, the surface 202 and one or both of the impermeable layer 216 and the storage layer 219. In some aspects, the self-healing layer may comprise a geologic formation that can stop or impede a flow of hazardous material (whether in liquid, solid, or gaseous form) from a storage portion of the drillhole 204 to or toward the terranean surface 202. For example, during formation of the drillhole 204 (e.g., drilling), all are portions of the geologic formations of the layers 212, 214, 216, and 219, may be damaged, thereby affecting or changing their geologic characteristics (e.g., permeability). In certain aspects, the location of the drillhole 204 may be selected so as to be formed through the self-healing layer. For example, as shown, the drillhole 204 may be formed such that at least a portion of the vertical portion 206 of the drillhole 204 is formed to pass through the self-healing layer. In some aspects, the self-healing layer comprises a geologic formation that that does not sustain cracks for extended time durations even after being drilled therethrough. Examples of the geologic formation in the self-healing layer include clay or dolomite. Cracks in such rock formations tend to heal, that is, they disappear rapidly with time due to the relative ductility of the material, and the enormous pressures that occur underground from the weight of the overlying rock on the formation in the self-healing layer. In addition to providing a “healing mechanism” for cracks that occur due to the formation of the drillhole 204 (e.g., drilling or otherwise), the self-healing layer may also provide a barrier to natural faults and other cracks that otherwise could provide a pathway for hazardous material leakage (e.g., fluid or solid) from the storage region (e.g., in the substantially horizontal portion 210) to the terranean surface 202, the mobile water layer 214, or both. As shown in this example, the substantially horizontal portion 210 of the drillhole 204 includes a storage area 217 in a distal part of the portion 210 into which hazardous material may be retrievably placed for long-term storage. For example, as shown, a work string 224 (e.g., tubing, coiled tubing, wireline, or otherwise) may be extended into the cased drillhole 204 to place one or more (three shown but there may be more or less) hazardous material canisters 226 into long term, but in some aspects, retrievable, storage in the portion 210. For example, in the implementation shown in FIG. 2, the work string 224 may include a downhole tool 228 that couples to the canister 226, and with each trip into the drillhole 204, the downhole tool 228 may deposit a particular hazardous material canister 226 in the substantially horizontal portion 210. The downhole tool 228 may couple to the canister 226 by, in some aspects, a threaded connection or other type of connection, such as a latched connection. In alternative aspects, the downhole tool 228 may couple to the canister 226 with an interlocking latch, such that rotation (or linear movement or electric or hydraulic switches) of the downhole tool 228 may latch to (or unlatch from) the canister 226. In alternative aspects, the downhole tool 224 may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to the canister 226. In some examples, the canister 226 may also include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) of an opposite polarity as the magnets on the downhole tool 224. In some examples, the canister 226 may be made from or include a ferrous or other material attractable to the magnets of the downhole tool 224. As another example, each canister 226 may be positioned within the drillhole 204 by a drillhole tractor (e.g., on a wireline or otherwise), which may push or pull the canister into the substantially horizontal portion 210 through motorized (e.g., electric) motion. As yet another example, each canister 226 may include or be mounted to rollers (e.g., wheels), so that the downhole tool 224 may push the canister 226 into the cased drillhole 204. In some example implementations, the canister 226, one or more of the drillhole casings 220 and 222, or both, may be coated with a friction-reducing coating prior to the deposit operation. For example, by applying a coating (e.g., petroleum-based product, resin, ceramic, or otherwise) to the canister 226 and/or drillhole casings, the canister 226 may be more easily moved through the cased drillhole 204 into the substantially horizontal portion 210. In some aspects, only a portion of the drillhole casings may be coated. For example, in some aspects, the substantially vertical portion 206 may not be coated, but the J-section portion 208 or the substantially horizontal portion 210, or both, may be coated to facilitate easier deposit and retrieval of the canister 226. FIG. 2 also illustrates an example of a retrieval operation of hazardous material in the substantially horizontal portion 210 of the drillhole 204. A retrieval operation may be the opposite of a deposit operation, such that the downhole tool 224 (e.g., a fishing tool) may be run into the drillhole 204, coupled to the last-deposited canister 226 (e.g., threadingly, latched, by magnet, or otherwise), and pull the canister 226 to the terranean surface 202. Multiple retrieval trips may be made by the downhole tool 224 in order to retrieve multiple canisters from the substantially horizontal portion 210 of the drillhole 204. Each canister 226 may enclose hazardous material. Such hazardous material, in some examples, may be biological or chemical waste or other biological or chemical hazardous material. In some examples, the hazardous material may include nuclear material, such as spent nuclear fuel recovered from a nuclear reactor (e.g., commercial power or test reactor) or military nuclear material. For example, a gigawatt nuclear plant may produce 30 tons of spent nuclear fuel per year. The density of that fuel is typically close to 10 (10 gm/cm3=10 kg/liter), so that the volume for a year of nuclear waste is about 3 m3. Spent nuclear fuel, in the form of nuclear fuel pellets, may be taken from the reactor and not modified. Nuclear fuel pellet are solid, although they can contain and emit a variety of radioactive gases including tritium (13 year half-life), krypton-85 (10.8 year half-life), and carbon dioxide containing C-14 (5730 year half-life). In some aspects, the storage layer 219 should be able to contain any radioactive output (e.g., gases) within the layer 219, even if such output escapes the canisters 226. For example, the storage layer 219 may be selected based on diffusion times of radioactive output through the layer 219. For example, a minimum diffusion time of radioactive output escaping the storage layer 219 may be set at, for example, fifty times a half-life for any particular component of the nuclear fuel pellets. Fifty half-lives as a minimum diffusion time would reduce an amount of radioactive output by a factor of 1×10−15. As another example, setting a minimum diffusion time to thirty half-lives would reduce an amount of radioactive output by a factor of one billion. For example, plutonium-239 is often considered a dangerous waste product in spent nuclear fuel because of its long half-life of 24,100 years. For this isotope, 50 half-lives would be 1.2 million years. Plutonium-239 has low solubility in water, is not volatile, and as a solid is not capable of diffusion through a matrix of the rock formation that comprises the illustrated storage layer 219 (e.g., shale or other formation). The storage layer 219, for example comprised of shale, may offer the capability to have such isolation times (e.g., millions of years) as shown by the geological history of containing gaseous hydrocarbons (e.g., methane and otherwise) for several million years. In contrast, in conventional nuclear material storage methods, there was a danger that some plutonium might dissolve in a layer that comprised mobile ground water upon confinement escape. As further shown in FIG. 2, the storage canisters 226 may be positioned for long term storage in the substantially horizontal portion 210, which, as shown, is coupled to the vertical portion 106 of the drillhole 104 through the J-section portion 208. As illustrated, the J-section portion 208 includes an upwardly directed portion angled toward the terranean surface 202. In some aspects, for example when there is radioactive hazardous material stored in the canisters 226, this inclination of the J-section portion 208 (and inclination of the inclined portion 240, if formed) may provide a further degree of safety and containment to prevent or impede the material, even if leaked from the canister 226, from reaching, e.g., the mobile water layer 214, the vertical portion 206 of the drillhole 204, the terranean surface 202, or a combination thereof. For example, radionuclides of concern in the hazardous material tend to be relatively buoyant or heavy (as compared to other components of the material). Buoyant radionuclides may be the greatest concern for leakage, since heavy elements and molecules tend to sink, and would not diffuse upward towards the terranean surface 202. Krypton gas, and particularly krypton-85, is a buoyant radioactive element that is heavier than air (as are most gases) but much lighter than water. Thus, should krypton-85 be introduced into a water bath, such gas would tend to float upward towards the terranean surface 202. Iodine, on the other hand, is denser than water, and would tend to diffuse downward if introduced into a water bath. By including the J-section portion 208 of the drillhole 204, any such diffusion of radioactive material (e.g., even if leaked from a canister 226 and in the presence of water or other liquid in the drillhole 204 or otherwise) would be directed angularly upward toward the substantially horizontal portion 210, and more specifically, toward a distal end 221 of the substantially horizontal portion 210 and away from the J-section portion 208 (and the vertical portion 206) of the drillhole 204. Thus, leaked hazardous material, even in a diffusible gas form, would not be offered a path (e.g., directly) to the terranean surface 202 (or the mobile water layer 214) through the vertical portion 206 of the drillhole 210. For instance, the leaked hazardous material (especially in gaseous form) would be directed and gathered at the distal end 221 of the drillhole portion 210, or, generally, within the substantially horizontal portion 210 of the drillhole 204. Alternative methods of depositing the canisters 226 into the inclined drillhole portion 210 may also be implemented. For instance, a fluid (e.g., liquid or gas) may be circulated through the drillhole 204 to fluidly push the canisters 226 into the inclined drillhole portion 210. In some example, each canister 226 may be fluidly pushed separately. In alternative aspects, two or more canisters 226 may be fluidly pushed, simultaneously, through the drillhole 204 for deposit into the substantially horizontal portion 210. The fluid can be, in some cases, water. Other examples include a drilling mud or drilling foam. In some examples, a gas may be used to push the canisters 226 into the drillhole, such as air, argon, or nitrogen. In some aspects, the choice of fluid may depend at least in part on a viscosity of the fluid. For example, a fluid may be chosen with enough viscosity to impede the drop of the canister 226 into the substantially vertical portion 206. This resistance or impedance may provide a safety factor against a sudden drop of the canister 226. The fluid may also provide lubrication to reduce a sliding friction between the canister 226 and the casings 220 and 222. The canister 226 can be conveyed within a casing filled with a liquid of controlled viscosity, density, and lubricant qualities. The fluid-filled annulus between the inner diameter of the casings 220 and 222 and the outer diameter of the conveyed canister 226 represents an opening designed to dampen any high rate of canister motion, providing automatic passive protection in an unlikely decoupling of the conveyed canister 226. In some aspects, other techniques may be employed to facilitate deposit of the canister 226 into the substantially horizontal portion 210. For example, one or more of the installed casings (e.g., casings 220 and 222) may have rails to guide the storage canister 226 into the drillhole 202 while reducing friction between the casings and the canister 226. The storage canister 226 and the casings (or the rails) may be made of materials that slide easily against one another. The casings may have a surface that is easily lubricated, or one that is self-lubricating when subjected to the weight of the storage canister 226. The fluid may also be used for retrieval of the canister 226. For example, in an example retrieval operation, a volume within the casings 220 and 222 may be filled with a compressed gas (e.g., air, nitrogen, argon, or otherwise). As the pressure increases at an end of the substantially horizontal portion 210, the canisters 226 may be pushed toward the J-section portion 208, and subsequently through the substantially vertical portion 206 to the terranean surface. In some aspects, the drillhole 204 may be formed for the primary purpose of long-term storage of hazardous materials. In alternative aspects, the drillhole 204 may have been previously formed for the primary purpose of hydrocarbon production (e.g., oil, gas). For example, storage layer 219 may be a hydrocarbon bearing formation from which hydrocarbons were produced into the drillhole 204 and to the terranean surface 202. In some aspects, the storage layer 219 may have been hydraulically fractured prior to hydrocarbon production. Further in some aspects, the production casing 222 may have been perforated prior to hydraulic fracturing. In such aspects, the production casing 222 may be patched (e.g., cemented) to repair any holes made from the perforating process prior to a deposit operation of hazardous material. In addition, any cracks or openings in the cement between the casing and the drillhole can also be filled at that time. For example, in the case of spent nuclear fuel as a hazardous material, the drillhole may be formed at a particular location, e.g., near a nuclear power plant, as a new drillhole provided that the location also includes an appropriate storage layer 219, such as a shale formation. Alternatively, an existing well that has already produced shale gas, or one that was abandoned as “dry,” (e.g., with sufficiently low organics that the gas in place is too low for commercial development), may be selected as the drillhole 204. In some aspects, prior hydraulic fracturing of the storage layer 219 through the drillhole 204 may make little difference in the hazardous material storage capability of the drillhole 204. But such a prior activity may also confirm the ability of the storage layer 219 to store gases and other fluids for millions of years. If, therefore, the hazardous material or output of the hazardous material (e.g., radioactive gasses or otherwise) were to escape from the canister 226 and enter the fractured formation of the storage layer 219, such fractures may allow that material to spread relatively rapidly over a distance comparable in size to that of the fractures. In some aspects, the drillhole 202 may have been drilled for a production of hydrocarbons, but production of such hydrocarbons had failed, e.g., because the storage layer 219 comprised a rock formation (e.g., shale or otherwise) that was too ductile and difficult to fracture for production, but was advantageously ductile for the long-term storage of hazardous material. FIG. 3 is a schematic illustration of example implementations of another hazardous material storage repository system, e.g., a subterranean location for the long-term (e.g., tens, hundreds, or thousands of years or more) but retrievable safe and secure storage of hazardous material, during a deposit or retrieval operation according to the present disclosure. For example, turning to FIG. 3, this figure illustrates an example hazardous material storage repository system 300 during a deposit (or retrieval, as described below) process, e.g., during deployment of one or more canisters of hazardous material in a subterranean formation. As illustrated, the hazardous material storage repository system 300 includes a drillhole 304 formed (e.g., drilled or otherwise) from a terranean surface 302 and through multiple subterranean layers 312, 314, and 316. Although the terranean surface 302 is illustrated as a land surface, terranean surface 302 may be a sub-sea or other underwater surface, such as a lake or an ocean floor or other surface under a body of water. Thus, the present disclosure contemplates that the drillhole 304 may be formed under a body of water from a drilling location on or proximate the body of water. The illustrated drillhole 304 is a directional drillhole in this example of hazardous material storage repository system 300. For instance, the drillhole 304 includes a substantially vertical portion 306 coupled to a curved portion 308, which in turn is coupled to a vertically undulating portion 310. As used in the present disclosure, “substantially” in the context of a drillhole orientation, refers to drillholes that may not be exactly vertical (e.g., exactly perpendicular to the terranean surface 302) or exactly horizontal (e.g., exactly parallel to the terranean surface 302), or exactly inclined at a particular incline angle relative to the terranean surface 302. In other words, vertical drillholes often undulate offset from a true vertical direction, that they might be drilled at an angle that deviates from true vertical, and horizontal drillholes often undulate offset from exactly horizontal. Further, in some aspects, an undulating portion may not undulate with regularity, i.e., have peaks that are uniformly spaced apart or valleys that are uniformly spaced apart. Instead, an undulating drillhole may undulate irregularly, e.g., with peaks that are non-uniformly spaced and/or valleys that are non-uniformly spaced. Further, an undulated drillhole may have a peak-to-valley distance that varies along a length of the drillhole. As illustrated in this example, the three portions of the drillhole 304—the vertical portion 306, the curved portion 308, and the vertically undulating portion 310—form a continuous drillhole 304 that extends into the Earth. The illustrated drillhole 304, in this example, has a surface casing 320 positioned and set around the drillhole 304 from the terranean surface 302 into a particular depth in the Earth. For example, the surface casing 320 may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the drillhole 304 in a shallow formation. As used herein, “tubular” may refer to a member that has a circular cross-section, elliptical cross-section, or other shaped cross-section. For example, in this implementation of the hazardous material storage repository system 300, the surface casing 320 extends from the terranean surface through a surface layer 312. The surface layer 312, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer 312 in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing 320 may isolate the drillhole 304 from such mobile water, and may also provide a hanging location for other casing strings to be installed in the drillhole 304. Further, although not shown, a conductor casing may be set above the surface casing 320 (e.g., between the surface casing 320 and the surface 302 and within the surface layer 312) to prevent drilling fluids from escaping into the surface layer 312. As illustrated, a production casing 322 is positioned and set within the drillhole 304 downhole of the surface casing 320. Although termed a “production” casing, in this example, the casing 322 may or may not have been subject to hydrocarbon production operations. Thus, the casing 322 refers to and includes any form of tubular member that is set (e.g., cemented) in the drillhole 304 downhole of the surface casing 320. In some examples of the hazardous material storage repository system 300, the production casing 322 may begin at an end of the curved portion 308 and extend throughout the vertically undulating portion 310. The casing 322 could also extend into the curved portion 308 and into the vertical portion 306. As shown, cement 330 is positioned (e.g., pumped) around the casings 320 and 322 in an annulus between the casings 320 and 322 and the drillhole 304. The cement 330, for example, may secure the casings 320 and 322 (and any other casings or liners of the drillhole 304) through the subterranean layers under the terranean surface 302. In some aspects, the cement 330 may be installed along the entire length of the casings (e.g., casings 320 and 322 and any other casings), or the cement 330 could be used along certain portions of the casings if adequate for a particular drillhole 302. The cement 330 can also provide an additional layer of confinement for the hazardous material in canisters 326. The drillhole 304 and associated casings 320 and 322 may be formed with various example dimensions and at various example depths (e.g., true vertical depth, or TVD). For instance, a conductor casing (not shown) may extend down to about 120 feet TVD, with a diameter of between about 28 in. and 60 in. The surface casing 320 may extend down to about 2500 feet TVD, with a diameter of between about 22 in. and 48 in. An intermediate casing (not shown) between the surface casing 320 and production casing 322 may extend down to about 8000 feet TVD, with a diameter of between about 16 in. and 36 in. The production casing 322 may extend inclinedly (e.g., to case the vertically undulating portion 310) with a diameter of between about 11 in. and 22 in. The foregoing dimensions are merely provided as examples and other dimensions (e.g., diameters, TVDs, lengths) are contemplated by the present disclosure. For example, diameters and TVDs may depend on the particular geological composition of one or more of the multiple subterranean layers (312, 314, and 316), particular drilling techniques, as well as a size, shape, or design of a hazardous material canister 326 that contains hazardous material to be deposited in the hazardous material storage repository system 300. In some alternative examples, the production casing 322 (or other casing in the drillhole 304) could be circular in cross-section, elliptical in cross-section, or some other shape. As illustrated, the vertical portion 306 of the drillhole 304 extends through subterranean layers 312, 314, and 316, and, in this example, lands in a subterranean layer 319. As discussed above, the surface layer 312 may or may not include mobile water. Subterranean layer 314, which is below the surface layer 312, in this example, is a mobile water layer 314. For instance, mobile water layer 314 may include one or more sources of mobile water, such as freshwater aquifers, salt water or brine, or other source of mobile water. In this example of hazardous material storage repository system 300, mobile water may be water that moves through a subterranean layer based on a pressure differential across all or a part of the subterranean layer. For example, the mobile water layer 314 may be a permeable geologic formation in which water freely moves (e.g., due to pressure differences or otherwise) within the layer 314. In some aspects, the mobile water layer 314 may be a primary source of human-consumable water in a particular geographic area. Examples of rock formations of which the mobile water layer 314 may be composed include porous sandstones and limestones, among other formations. Other illustrated layers, such as the impermeable layer 316 and the storage layer 319, may include immobile water. Immobile water, in some aspects, is water (e.g., fresh, salt, brine), that is not fit for human or animal consumption, or both. Immobile water, in some aspects, may be water that, by its motion through the layers 316 or 319 (or both), cannot reach the mobile water layer 314, terranean surface 302, or both, within 10,000 years or more (such as to 1,000,000 years). Below the mobile water layer 314, in this example implementation of hazardous material storage repository system 300, is an impermeable layer 316. The impermeable layer 316, in this example, may not allow mobile water to pass through. Thus, relative to the mobile water layer 314, the impermeable layer 316 may have low permeability, e.g., on the order of nanodarcy permeability. Additionally, in this example, the impermeable layer 316 may be a relatively non-ductile (i.e., brittle) geologic formation. One measure of non-ductility is brittleness, which is the ratio of compressive stress to tensile strength. In some examples, the brittleness of the impermeable layer 316 may be between about 20 MPa and 40 MPa. As shown in this example, the impermeable layer 316 is shallower (e.g., closer to the terranean surface 302) than the storage layer 319. In this example rock formations of which the impermeable layer 316 may be composed include, for example, certain kinds of sandstone, mudstone, clay, and slate that exhibit permeability and brittleness properties as described above. In alternative examples, the impermeable layer 316 may be deeper (e.g., further from the terranean surface 302) than the storage layer 319. In such alternative examples, the impermeable layer 316 may be composed of an igneous rock, such as granite. Below the impermeable layer 316 is the storage layer 319. The storage layer 319, in this example, may be chosen as the landing for the vertically undulating portion 310, which stores the hazardous material, for several reasons. Relative to the impermeable layer 316 or other layers, the storage layer 319 may be thick, e.g., between about 100 and 200 feet of total vertical thickness. Thickness of the storage layer 319 may allow for easier landing and directional drilling, thereby allowing the vertically undulating portion 310 to be readily emplaced within the storage layer 319 during constructions (e.g., drilling). If formed through an approximate horizontal center of the storage layer 319, the vertically undulating portion 310 may be surrounded by about 50 to 100 feet of the geologic formation that comprises the storage layer 319. Further, the storage layer 319 may also have only immobile water, e.g., due to a very low permeability of the layer 319 (e.g., on the order of milli- or nanodarcys). In addition, the storage layer 319 may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer 319 is between about 3 MPa and 10 MPa. Examples of rock formations of which the storage layer 319 may be composed include: shale and anhydrite. Further, in some aspects, hazardous material may be stored below the storage layer, even in a permeable formation such as sandstone or limestone, if the storage layer is of sufficient geologic properties to isolate the permeable layer from the mobile water layer 314. In some examples implementations of the hazardous material storage repository system 300, the storage layer 319 (and/or the impermeable layer 316) is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer 319. For example, shale formations may be suitable for a long-term confinement of hazardous material (e.g., in the hazardous material canisters 326), and for their isolation from mobile water layer 314 (e.g., aquifers) and the terranean surface 302. Shale formations may be found relatively deep in the Earth, typically 3000 feet or greater, and placed in isolation below any fresh water aquifers. Other formations may include salt or other impermeable formation layer. Shale formations (or salt or other impermeable formation layers), for instance, may include geologic properties that enhance the long-term (e.g., thousands of years) isolation of material. Such properties, for instance, have been illustrated through the long term storage (e.g., tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid, mixed phase fluid) without escape of such fluids into surrounding layers (e.g., mobile water layer 314). Indeed, shale has been shown to hold natural gas for millions of years or more, giving it a proven capability for long-term storage of hazardous material. Example shale formations (e.g., Marcellus, Eagle Ford, Barnett, and otherwise) has stratification that contains many redundant sealing layers that have been effective in preventing movement of water, oil, and gas for millions of years, lacks mobile water, and can be expected (e.g., based on geological considerations) to seal hazardous material (e.g., fluids or solids) for thousands of years after deposit. In some aspects, the formation of the storage layer 319 and/or the impermeable layer 316 may form a leakage barrier, or barrier layer to fluid leakage that may be determined, at least in part, by the evidence of the storage capacity of the layer for hydrocarbons or other fluids (e.g., carbon dioxide) for hundreds of years, thousands of years, tens of thousands of years, hundreds of thousands of years, or even millions of years. For example, the barrier layer of the storage layer 319 and/or impermeable layer 316 may be defined by a time constant for leakage of the hazardous material more than 10,000 years (such as between 10,000 years and 1,000,000 years) based on such evidence of hydrocarbon or other fluid storage. Shale (or salt or other impermeable layer) formations may also be at a suitable depth, e.g., between 3000 and 12,000 feet TVD. Such depths are typically below ground water aquifer (e.g., surface layer 312 and/or mobile water layer 314). Further, the presence of soluble elements in shale, including salt, and the absence of these same elements in aquifer layers, demonstrates a fluid isolation between shale and the aquifer layers. Another particular quality of shale that may advantageously lend itself to hazardous material storage is its clay content, which, in some aspects, provides a measure of ductility greater than that found in other, impermeable rock formations (e.g., impermeable layer 316). For example, shale may be stratified, made up of thinly alternating layers of clays (e.g., between about 20-30% clay by volume) and other minerals. Such a composition may make shale less brittle and, thus less susceptible to fracturing (e.g., naturally or otherwise) as compared to rock formations in the impermeable layer (e.g., dolomite or otherwise). For example, rock formations in the impermeable layer 316 may have suitable permeability for the long term storage of hazardous material, but are too brittle and commonly are fractured. Thus, such formations may not have sufficient sealing qualities (as evidenced through their geologic properties) for the long term storage of hazardous material. The present disclosure contemplates that there may be many other layers between or among the illustrated subterranean layers 312, 314, 316, and 319. For example, there may be repeating patterns (e.g., vertically), of one or more of the mobile water layer 314, impermeable layer 316, and storage layer 319. Further, in some instances, the storage layer 319 may be directly adjacent (e.g., vertically) the mobile water layer 314, i.e., without an intervening impermeable layer 316. In some examples, all or portions of the curved portion 308 and the vertically undulating portion 310 may be formed below the storage layer 319, such that the storage layer 319 (e.g., shale or other geologic formation with characteristics as described herein) is vertically positioned between the vertically undulating portion 310 and the mobile water layer 314. Although not illustrated in this particular example shown in FIG. 3, a self-healing layer (e.g., such as the self-healing layer 132) may be found below the terranean surface 302 and between, for example, the surface 302 and one or both of the impermeable layer 316 and the storage layer 319. In some aspects, the self-healing layer may comprise a geologic formation that can stop or impede a flow of hazardous material (whether in liquid, solid, or gaseous form) from a storage portion of the drillhole 304 to or toward the terranean surface 302. For example, during formation of the drillhole 304 (e.g., drilling), all are portions of the geologic formations of the layers 312, 314, 316, and 319, may be damaged, thereby affecting or changing their geologic characteristics (e.g., permeability). In certain aspects, the location of the drillhole 304 may be selected so as to be formed through the self-healing layer. For example, as shown, the drillhole 304 may be formed such that at least a portion of the vertical portion 306 of the drillhole 304 is formed to pass through the self-healing layer. In some aspects, the self-healing layer comprises a geologic formation that that does not sustain cracks for extended time durations even after being drilled therethrough. Examples of the geologic formation in the self-healing layer include clay or dolomite. Cracks in such rock formations tend to heal, that is, they disappear rapidly with time due to the relative ductility of the material, and the enormous pressures that occur underground from the weight of the overlying rock on the formation in the self-healing layer. In addition to providing a “healing mechanism” for cracks that occur due to the formation of the drillhole 304 (e.g., drilling or otherwise), the self-healing layer may also provide a barrier to natural faults and other cracks that otherwise could provide a pathway for hazardous material leakage (e.g., fluid or solid) from the storage region (e.g., in the vertically undulating portion 310) to the terranean surface 302, the mobile water layer 314, or both. As shown in this example, the vertically undulating portion 310 of the drillhole 304 includes a storage area 317 in a distal part of the portion 310 into which hazardous material may be retrievably placed for long-term storage. For example, as shown, a work string 324 (e.g., tubing, coiled tubing, wireline, or otherwise) may be extended into the cased drillhole 304 to place one or more (three shown but there may be more or less) hazardous material canisters 326 into long term, but in some aspects, retrievable, storage in the portion 310. For example, in the implementation shown in FIG. 3, the work string 324 may include a downhole tool 328 that couples to the canister 326, and with each trip into the drillhole 304, the downhole tool 328 may deposit a particular hazardous material canister 326 in the vertically undulating portion 310. The downhole tool 328 may couple to the canister 326 by, in some aspects, a threaded connection or other type of connection, such as a latched connection. In alternative aspects, the downhole tool 328 may couple to the canister 326 with an interlocking latch, such that rotation (or linear movement or electric or hydraulic switches) of the downhole tool 328 may latch to (or unlatch from) the canister 326. In alternative aspects, the downhole tool 324 may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to the canister 326. In some examples, the canister 326 may also include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) of an opposite polarity as the magnets on the downhole tool 324. In some examples, the canister 326 may be made from or include a ferrous or other material attractable to the magnets of the downhole tool 324. As another example, each canister 326 may be positioned within the drillhole 304 by a drillhole tractor (e.g., on a wireline or otherwise), which may push or pull the canister into the vertically undulating portion 310 through motorized (e.g., electric) motion. As yet another example, each canister 326 may include or be mounted to rollers (e.g., wheels), so that the downhole tool 324 may push the canister 326 into the cased drillhole 304. In some example implementations, the canister 326, one or more of the drillhole casings 320 and 322, or both, may be coated with a friction-reducing coating prior to the deposit operation. For example, by applying a coating (e.g., petroleum-based product, resin, ceramic, or otherwise) to the canister 326 and/or drillhole casings, the canister 326 may be more easily moved through the cased drillhole 304 into the vertically undulating portion 310. In some aspects, only a portion of the drillhole casings may be coated. For example, in some aspects, the substantially vertical portion 306 may not be coated, but the curved portion 308 or the vertically undulating portion 310, or both, may be coated to facilitate easier deposit and retrieval of the canister 326. FIG. 3 also illustrates an example of a retrieval operation of hazardous material in the vertically undulating portion 310 of the drillhole 304. A retrieval operation may be the opposite of a deposit operation, such that the downhole tool 324 (e.g., a fishing tool) may be run into the drillhole 304, coupled to the last-deposited canister 326 (e.g., threadingly, latched, by magnet, or otherwise), and pull the canister 326 to the terranean surface 302. Multiple retrieval trips may be made by the downhole tool 324 in order to retrieve multiple canisters from the vertically undulating portion 310 of the drillhole 304. Each canister 326 may enclose hazardous material. Such hazardous material, in some examples, may be biological or chemical waste or other biological or chemical hazardous material. In some examples, the hazardous material may include nuclear material, such as spent nuclear fuel recovered from a nuclear reactor (e.g., commercial power or test reactor) or military nuclear material. For example, a gigawatt nuclear plant may produce 30 tons of spent nuclear fuel per year. The density of that fuel is typically close to 10 (10 gm/cm3=10 kg/liter), so that the volume for a year of nuclear waste is about 3 m3. Spent nuclear fuel, in the form of nuclear fuel pellets, may be taken from the reactor and not modified. Nuclear fuel pellet are solid, although they can contain and emit a variety of radioactive gases including tritium (13 year half-life), krypton-85 (10.8 year half-life), and carbon dioxide containing C-14 (5730 year half-life). In some aspects, the storage layer 319 should be able to contain any radioactive output (e.g., gases) within the layer 319, even if such output escapes the canisters 326. For example, the storage layer 319 may be selected based on diffusion times of radioactive output through the layer 319. For example, a minimum diffusion time of radioactive output escaping the storage layer 319 may be set at, for example, fifty times a half-life for any particular component of the nuclear fuel pellets. Fifty half-lives as a minimum diffusion time would reduce an amount of radioactive output by a factor of 1×10−15. As another example, setting a minimum diffusion time to thirty half-lives would reduce an amount of radioactive output by a factor of one billion. For example, plutonium-239 is often considered a dangerous waste product in spent nuclear fuel because of its long half-life of 24,100 years. For this isotope, 50 half-lives would be 1.2 million years. Plutonium-239 has low solubility in water, is not volatile, and as a solid is not capable of diffusion through a matrix of the rock formation that comprises the illustrated storage layer 319 (e.g., shale or other formation). The storage layer 319, for example comprised of shale, may offer the capability to have such isolation times (e.g., millions of years) as shown by the geological history of containing gaseous hydrocarbons (e.g., methane and otherwise) for several million years. In contrast, in conventional nuclear material storage methods, there was a danger that some plutonium might dissolve in a layer that comprised mobile ground water upon confinement escape. As further shown in FIG. 3, the storage canisters 326 may be positioned for long term storage in the vertically undulating portion 310, which, as shown, is coupled to the vertical portion 106 of the drillhole 104 through the curved portion 308. As illustrated, the curved portion 308 includes an upwardly directed portion angled toward the terranean surface 302. Further, as shown, the undulating portion 310 of the drillhole 304 includes several upwardly and downwardly (relative to the surface 302) inclined portions, thereby forming several peaks and valleys in the undulating portion 310. In some aspects, for example when there is radioactive hazardous material stored in the canisters 326, these inclinations of the curved portion 308 and undulating portion 310 may provide a further degree of safety and containment to prevent or impede the material, even if leaked from the canister 326, from reaching, e.g., the mobile water layer 314, the vertical portion 306 of the drillhole 304, the terranean surface 302, or a combination thereof. For example, radionuclides of concern in the hazardous material tend to be relatively buoyant or heavy (as compared to other components of the material). Buoyant radionuclides may be the greatest concern for leakage, since heavy elements and molecules tend to sink, and would not diffuse upward towards the terranean surface 302. Krypton gas, and particularly krypton-85, is a buoyant radioactive element that is heavier than air (as are most gases) but much lighter than water. Thus, should krypton-85 be introduced into a water bath, such gas would tend to float upward towards the terranean surface 302. Iodine, on the other hand, is denser than water, and would tend to diffuse downward if introduced into a water bath. By including the curved portion 308 of the drillhole 304 and the undulating portion 310, any such diffusion of radioactive material (e.g., even if leaked from a canister 326 and in the presence of water or other liquid in the drillhole 304 or otherwise) would be directed toward the vertically undulating portion 310, and more specifically, to peaks within the vertically undulating portion 310 and away from the curved portion 308 (and the vertical portion 306) of the drillhole 304. Thus, leaked hazardous material, even in a diffusible gas form, would not be offered a path (e.g., directly) to the terranean surface 302 (or the mobile water layer 314) through the vertical portion 306 of the drillhole 310. For instance, the leaked hazardous material (especially in gaseous form) would be directed and gathered at the peaks of the drillhole portion 310, or, generally, within the vertically undulating portion 310 of the drillhole 304. Alternative methods of depositing the canisters 326 into the inclined drillhole portion 310 may also be implemented. For instance, a fluid (e.g., liquid or gas) may be circulated through the drillhole 304 to fluidly push the canisters 326 into the inclined drillhole portion 310. In some example, each canister 326 may be fluidly pushed separately. In alternative aspects, two or more canisters 326 may be fluidly pushed, simultaneously, through the drillhole 304 for deposit into the vertically undulating portion 310. The fluid can be, in some cases, water. Other examples include a drilling mud or drilling foam. In some examples, a gas may be used to push the canisters 326 into the drillhole, such as air, argon, or nitrogen. In some aspects, the choice of fluid may depend at least in part on a viscosity of the fluid. For example, a fluid may be chosen with enough viscosity to impede the drop of the canister 326 into the substantially vertical portion 306. This resistance or impedance may provide a safety factor against a sudden drop of the canister 326. The fluid may also provide lubrication to reduce a sliding friction between the canister 326 and the casings 320 and 322. The canister 326 can be conveyed within a casing filled with a liquid of controlled viscosity, density, and lubricant qualities. The fluid-filled annulus between the inner diameter of the casings 320 and 322 and the outer diameter of the conveyed canister 326 represents an opening designed to dampen any high rate of canister motion, providing automatic passive protection in an unlikely decoupling of the conveyed canister 326. In some aspects, other techniques may be employed to facilitate deposit of the canister 326 into the vertically undulating portion 310. For example, one or more of the installed casings (e.g., casings 320 and 322) may have rails to guide the storage canister 326 into the drillhole 302 while reducing friction between the casings and the canister 326. The storage canister 326 and the casings (or the rails) may be made of materials that slide easily against one another. The casings may have a surface that is easily lubricated, or one that is self-lubricating when subjected to the weight of the storage canister 326. The fluid may also be used for retrieval of the canister 326. For example, in an example retrieval operation, a volume within the casings 320 and 322 may be filled with a compressed gas (e.g., air, nitrogen, argon, or otherwise). As the pressure increases at an end of the vertically undulating portion 310, the canisters 326 may be pushed toward the curved portion 308, and subsequently through the substantially vertical portion 306 to the terranean surface. In some aspects, the drillhole 304 may be formed for the primary purpose of long-term storage of hazardous materials. In alternative aspects, the drillhole 304 may have been previously formed for the primary purpose of hydrocarbon production (e.g., oil, gas). For example, storage layer 319 may be a hydrocarbon bearing formation from which hydrocarbons were produced into the drillhole 304 and to the terranean surface 302. In some aspects, the storage layer 319 may have been hydraulically fractured prior to hydrocarbon production. Further in some aspects, the production casing 322 may have been perforated prior to hydraulic fracturing. In such aspects, the production casing 322 may be patched (e.g., cemented) to repair any holes made from the perforating process prior to a deposit operation of hazardous material. In addition, any cracks or openings in the cement between the casing and the drillhole can also be filled at that time. For example, in the case of spent nuclear fuel as a hazardous material, the drillhole may be formed at a particular location, e.g., near a nuclear power plant, as a new drillhole provided that the location also includes an appropriate storage layer 319, such as a shale formation. Alternatively, an existing well that has already produced shale gas, or one that was abandoned as “dry,” (e.g., with sufficiently low organics that the gas in place is too low for commercial development), may be selected as the drillhole 304. In some aspects, prior hydraulic fracturing of the storage layer 319 through the drillhole 304 may make little difference in the hazardous material storage capability of the drillhole 304. But such a prior activity may also confirm the ability of the storage layer 319 to store gases and other fluids for millions of years. If, therefore, the hazardous material or output of the hazardous material (e.g., radioactive gasses or otherwise) were to escape from the canister 326 and enter the fractured formation of the storage layer 319, such fractures may allow that material to spread relatively rapidly over a distance comparable in size to that of the fractures. In some aspects, the drillhole 302 may have been drilled for a production of hydrocarbons, but production of such hydrocarbons had failed, e.g., because the storage layer 319 comprised a rock formation (e.g., shale or otherwise) that was too ductile and difficult to fracture for production, but was advantageously ductile for the long-term storage of hazardous material. FIG. 4A-4C are schematic illustrations of other example implementations of a hazardous material storage repository system according to the present disclosure. FIG. 4A shows hazardous material storage repository system 400, FIG. 4B shows hazardous material storage repository system 450, and FIG. 4C shows hazardous material storage repository system 480. Each of the systems 400, 450, and 480 include a substantially vertical drillhole (404, 454, and 484, respectively) drilled from a terranean surface (402, 452, and 482, respectively). Each substantially vertical drillhole (404, 454, 484) couples to (or continues into) a transition drillhole (406, 456, and 486, respectively) that is a curved or radiussed drillhole. Each transition drillhole (406, 456, and 486) then couples to (or continues into) an isolation drillhole (408, 458, and 488, respectively) that includes or comprises a hazardous material storage repository into which one or more hazardous material storage canisters (e.g., canisters 126) may be placed for long-term storage and, if necessary retrieved according to the present disclosure. As shown in FIG. 4A, the isolation drillhole 408 is a spiral drillhole that, at the point where it connects to the transition drillhole 406, starts to curve to the horizontal and simultaneously begins to curve to the side, i.e. in a horizontal direction. Once the spiral drillhole reaches its lowest point, it continues to curve in both directions, giving it a slight upward spiral. At that point the horizontal curve may be made a little bigger so that the curve does not intersect the vertical drillhole 404. Once the spiral drillhole begins to rise, a curved hazardous material storage repository section may commence. The storage section may continue until a highest point (e.g., point closest to the terranean surface 402), which is a dead-end trap (e.g., for escaped hazardous material solid, liquid, or gas). The rise of the spiral drillhole can be typically 3 degrees. In some aspects, the path of the spiral drillhole 408 can be down the axis of the spiral (that is, in the center of the spiraling circles) or displaced. Also, as shown in FIG. 4A, the vertical drillhole 404 is formed within the spiral drillhole 408. In other words, the spiral drillhole 408 may be formed symmetrically around the vertical drillhole 404. Turning briefly to FIG. 4C, the system 480 shows a spiral drillhole 488 similar to that of the spiral drillhole 408. However, spiral drillhole 488 is formed offset and to a side of the vertical drillhole 484. In some aspects, the spiral drillhole 488 can be formed offset of any side of the vertical drillhole 484. Turning to FIG. 4B, the system 450 includes a spiral drillhole 458 that is coupled to the transition drillhole 456 that turns from the vertical drillhole 454. Here, the spiral drillhole 458, rather than being oriented vertically (e.g., with an axis of rotation parallel of the vertical drillhole), is oriented horizontally (e.g., with an axis of rotation perpendicular to the vertical drillhole 454). At an end of or within the spiral drillhole 458 (or both) is a hazardous material storage section. In the implementations of systems 400, 450, and 480, a radius of curvature of the transition drillholes may be about 1000 feet. The circumference of each spiral in the spiral drillholes may be about a times the radius of curvature, or about 6,000 feet. Thus, each spiral in the spiral drillholes may contain a bit over one mile of storage area of hazardous material canisters. In some alternative aspects, the radius of curvature may be about 500 feet. Then, each spiral of the spiral drillholes may include about 0.5 miles of storage area of hazardous material canisters. If two miles of storage is desired then there may be four spirals for each spiral drillholes of this size. As shown in FIGS. 4A-4C, each of the systems 400, 450, and 480 include drillhole portions that serve as hazardous material storage areas and are directed vertically toward the terranean surface and away from an intersection between the transition drillhole of each system and the vertical drillhole of each section. Thus, any leaked hazardous material (e.g., such as radioactive waste gas) may be directed to such vertically-directed storage areas and away from the vertical drillholes. Each of the drillholes shown in FIGS. 4A-4C may be cased or uncased; the casing may serve as an additional layer of protection to prevent hazardous material from reaching mobile water. If casing is omitted, then angular changes to any drillhole can be more rapid with a constraint being the accommodation of movement of any canister therethrough. If there is casing, angular changes in direction for the drillholes may be done sufficiently slowly (as they are in standard directional drilling) that the casing can be pushed into the drillhole. Further, in some aspects, all or a portion of each of the illustrated isolation drillholes (408, 458, and 488) may be formed in or under an impermeable layer (as described in the present disclosure). In some aspects, implementations of a spiral drillhole may have a constant curvature around an axis of rotation. Alternative implementations of a spiral drillhole may have a gradually changing curvature, making the spirals in the spiral drillhole either tighter or less confined. Still additional implementations of a spiral drillhole may have the spirals changing in radius (making it tighter or less tight) but have little or no vertical rise (e.g., for situations in which it might be useful if the geologic layer in which the hazardous material storage section of the isolation drillholes is not very thick in the vertical dimension). FIG. 5A is a top view, and FIGS. 5B-5C are side views, of schematic illustrations of another example implementation of a hazardous material storage repository system 500. As shown, the system includes a vertical drillhole 504 formed from a terranean surface 502. The vertical drillhole 504 is coupled to or continues into a transition drillhole 506. The transition drillhole 506 is coupled to or turns into an isolation drillhole 508. In this example, the isolation drillhole 508 includes or comprise an undulating drillhole in which the undulations are substantially side-to-side. As shown in FIG. 5B, the isolation drillhole 508 rises toward the terranean surface 502 and vertically away from the transition drillhole 506 as it undulates side-to-side. As shown in FIG. 5C, alternatively, the isolation drillhole 508 stays in a plane substantially parallel to the terranean surface 502 as it undulates side-to-side. In some aspects, the spiral or undulating drillholes may be oriented without regard to the stress pattern of any gas or oil bearing layer in which they are formed. This is because the orientation need not take into account any fracturing of the drillhole as is the case for hydrocarbon production. Thus, drillhole geometers that are not oriented in the direction of the rock stress pattern, and are more compact, can be utilized. These drillholes may also have significant value in reducing the amount of terranean land under which the drillholes are formed. This may also reduce a cost of the land and of any mineral rights that must be bought to allow the hazardous material storage repository systems to be built. The drillholes are therefore determined not by the pattern of stresses in the rock, but primarily by the efficient and practical use of the available land. Each of the drillholes shown in FIGS. 5A-5C may be cased or uncased; the casing may serve as an additional layer of protection to prevent hazardous material from reaching mobile water. If casing is omitted, then angular changes to any drillhole can be more rapid with a constraint being the accommodation of movement of any canister therethrough. If there is casing, angular changes in direction for the drillholes may be done sufficiently slowly (as they are in standard directional drilling) that the casing can be pushed into the drillhole. Further, in some aspects, all or a portion of the isolation drillhole 508 may be formed in or under an impermeable layer (as described in the present disclosure). Referring generally to FIGS. 1A, 2, 3, 4A-4C, and 5A-5C, the example hazardous material storage repository systems (e.g., 100, 200, 300, 400, 450, 480, and 500) may provide for multiple layers of containment to ensure that a hazardous material (e.g., biological, chemical, nuclear) is sealingly stored in an appropriate subterranean layer. In some example implementations, there may be at least twelve layers of containment. In alternative implementations, a fewer or a greater number of containment layers may be employed. First, using spent nuclear fuel as an example hazardous material, the fuel pellets are taken from the reactor and not modified. They may be made from sintered uranium dioxide (UO2), a ceramic, and may remain solid and emit a variety of radioactive gases including tritium (13 year half-life), krypton-85 (10.8 year half-life), and carbon dioxide containing C-14 (5730 year half-life). Unless the pellets are exposed to extremely corrosive conditions or other effects that damage the multiple layers of containment, most of the radioisotopes (including the C-14, tritium or krypton-85) will be contained in the pellets. Second, the fuel pellets are surrounded by the zircaloy tubes of the fuel rods, just as in the reactor. As described, the tubes could be mounted in the original fuel assemblies, or removed from those assemblies for tighter packing. Third, the tubes are placed in the sealed housings of the hazardous material canister. The housing may be a unified structure or multi-panel structure, with the multiple panels (e.g., sides, top, bottom) mechanically fastened (e.g., screws, rivets, welds, and otherwise). Fourth, a material (e.g., solid or fluid) may fill the hazardous material canister to provide a further buffer between the material and the exterior of the canister. Fifth, the hazardous material canister(s) are positioned (as described above), in a drillhole that is lined with a steel or other sealing casing that extends, in some examples, throughout the entire drillhole (e.g., a substantially vertical portion, a radiussed portion, and a inclined portion). The casing is cemented in place, providing a relatively smooth surface (e.g., as compared to the drillhole wall) for the hazardous material canister to be moved through, thereby reducing the possibility of a leak or break during deposit or retrieval. Sixth, the cement that holds or helps hold the casing in place, may also provide a sealing layer to contain the hazardous material should it escape the canister. Seventh, the hazardous material canister is stored in a portion of the drillhole (e.g., the inclined portion) that is positioned within a thick (e.g., 100-200 feet) seam of a rock formation that comprises a storage layer. The storage layer may be chosen due at least in part to the geologic properties of the rock formation (e.g., only immobile water, low permeability, thick, appropriate ductility or non-brittleness). For example, in the case of shale as the rock formation of the storage layer, this type of rock may offers a level of containment since it is known that shale has been a seal for hydrocarbon gas for millions of years. The shale may contain brine, but that brine is demonstrably immobile, and not in communication with surface fresh water. Eighth, in some aspects, the rock formation of the storage layer may have other unique geological properties that offer another level of containment. For example, shale rock often contains reactive components, such as iron sulfide, that reduce the likelihood that hazardous materials (e.g., spent nuclear fuel and its radioactive output) can migrate through the storage layer without reacting in ways that reduce the diffusion rate of such output even further. Further, the storage layer may include components, such as clay and organic matter, that typically have extremely low diffusivity. For example, shale may be stratified and composed of thinly alternating layers of clays and other minerals. Such a stratification of a rock formation in the storage layer, such as shale, may offer this additional layer of containment. Ninth, the storage layer may be located deeper than, and under, an impermeable layer, which separates the storage layer (e.g., vertically) from a mobile water layer. Tenth, the storage layer may be selected based on a depth (e.g., 3000 to 12,000 ft.) of such a layer within the subterranean layers. Such depths are typically far below any layers that contain mobile water, and thus, the sheer depth of the storage layer provides an additional layer of containment. Eleventh, example implementations of the hazardous material storage repository system of the present disclosure facilitate monitoring of the stored hazardous material. For example, if monitored data indicates a leak or otherwise of the hazardous material (e.g., change in temperature, radioactivity, or otherwise), or even tampering or intrusion of the canister, the hazardous material canister may be retrieved for repair or inspection. Twelfth, the one or more hazardous material canisters may be retrievable for periodic inspection, conditioning, or repair, as necessary (e.g., with or without monitoring). Thus, any problem with the canisters may be addressed without allowing hazardous material to leak or escape from the canisters unabated. Thirteenth, even if hazardous material escaped from the canisters and no impermeable layer was located between the leaked hazardous material and the terranean surface, the leaked hazardous material may be contained within the drillhole at a location that has no upward path to the surface or to aquifers (e.g., mobile water layers) or to other zones that would be considered hazardous to humans. For example, the location, which may be a dead end of an inclined drillhole, a J-section drillhole, or peaks of a vertically undulating drillhole, may have no direct upward (e.g., toward the surface) path to a vertical portion of the drillhole. A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, example operations, methods, or processes described herein may include more steps or fewer steps than those described. Further, the steps in such example operations, methods, or processes may be performed in different successions than that described or illustrated in the figures. Accordingly, other implementations are within the scope of the following claims.
	description	FIG. 1 is a schematic diagram of a conventional commercial nuclear power reactor and various safety and cooling systems for the same. As shown in FIG. 1, a reactor 10 is positioned inside of a containment structure 1. During operation of reactor 10, liquid water coolant and moderator enters the reactor 10 through main feedwater lines 60 that are typically connected to a heat sink and source of fluid coolant, like a condenser cooled by a lake or river. Recirculation pump 20 and main recirculation loops 25 force flow of the liquid down through a bottom of the reactor 10, where the liquid then travels up through core 15 including nuclear fuel. As heat is transferred from fuel in core 15 to the liquid water coolant, the coolant may boil, producing steam that is driven to the top of reactor 10 and exits though a main steam line 50. Main steam line 50 connects to a turbine and paired generator to produce electricity from the energy in the steam. Once energy has been extracted from the steam, the steam is typically condensed and returned to the reactor 10 via feedwater line 60. In the instance that recirculation pump 20 fails and/or liquid coolant from main feedwater lines 60 are lost, such as in a station blackout event where access to the electrical grid is cut off, reactor 10 is typically tripped so as to stop producing heat through fission. However, significant amounts of decay heat are still generated in core 15 following such a trip, and additional fluid coolant may be required to maintain safe core temperatures and avoid reactor 10 overheat or damage. In these scenarios, active emergency cooling systems, such as a Reactor Core Isolation Cooling (RCIC) turbine 40 or higher-output High Pressure Injection Cooling (HPIC) turbine, for example, operate using steam produced in core 15 by decay heat to drive turbines. Flow from main steam lines 50 is diverted to RCIC lines 55 in this instance. RCIC turbine 40 may then drive an RCIC pump 41, which injects liquid coolant from a suppression pool 30 or condensate storage tank 31 into main feedwater line 60 via RCIC suction line 35 and injection line 42. The injected liquid coolant maintains a coolant level in reactor 10 above core 15 and transfers decay heat away from core 15, preventing fuel damage. Saturated steam coming off RCIC turbine 40 can be condensed in suppression pool 30 by venting into suppression pool 30 via RCIC exhaust line 43. RCIC turbine 40 typically requires a minimum steam pressure of 150 pounds/square inch in order to drive RCIC pump 41 to inject liquid coolant into main feedwater line 60 via injection line 42 and suction line 35. Pressure in main steam lines 50 from an outlet of reactor 10 will typically drop below 150 pounds/square inch after 8-20 hours of shutdown, at which time RCIC turbine 40 and other higher-pressure injection systems will not function. At this time, lower-pressure shutdown coolant injection systems (not shown) are activated and run off electricity from the electrical grid, or, in the station blackout event, emergency diesel generators. As long as an electricity source is available, lower-pressure injection systems can maintain safe temperatures and fluid level in core 15 until cold shutdown can be achieved or transient circumstances have ended and core 15 can resume generating power through fission. Regulatory bodies worldwide typically require these active systems, including RCIC systems and electricity-powered lower-pressure delivery systems, as the sole mechanisms to avoid core overheat and damage in transient scenarios involving loss of coolant and/or loss of offsite power. Example embodiments include methods and systems for cooling a nuclear reactor post-shutdown with a passive injection device connected to the reactor that injects a coolant into the reactor or a steam generator for the same using a local energetic fluid to drive the injection. Example embodiment injection devices work using fluids having pressure ranges with lower limits below those used in the operating nuclear reactor and those used to drive conventional coolant injection systems post-shutdown. The local energetic fluid may be supplied by the reactor itself; for example, in a Boiling Water Reactor (BWR) the passive injection device may use steam created by heating a coolant in the reactor. Similarly, in a Pressurized Water Reactor the passive injection device may use steam from a steam generator and inject coolant into the same. Example embodiment injection devices can passively inject coolant, without moving parts or electricity, using the local energetic fluid to suction and/or entrain the coolant and delivering the mixed fluid and coolant to the reactor. For example, an injection device may be a venturi that accelerates the fluid to create a pressure drop and draw the coolant into the fluid flow, which is then injected into the reactor. An example venturi may include a fluid inlet receiving the energetic fluid source, which then flows through a narrowing section to cause the acceleration and pressure drop, a coolant inlet at the narrowing section through which the coolant is drawn and entrained, and an outlet where the mix is injected into the nuclear reactor. For example, in a light water reactor, the coolant can be liquid water drawn from a suppression pool or other condensed source. Example methods include installing a passive, low-pressure-compatible injection device between a coolant source and the reactor and supplying the same with an energetic fluid. For example, a venturi can be installed off an RCIC line connected to a main steam line of a BWR, with the venturi on an RCIC suction line where the venturi can draw water from a suppression pool or condensate tank and inject the water into the reactor using steam from the main steam line. Example methods may further include operating one or more valves to selectively operate the injection device by providing it with fluid connection to the various coolant and fluid sources. Such operation may be executed any time coolant injection into the reactor is desired, such as post-shutdown following a complete station blackout transient after reactor pressure has dropped to levels at which RCIC and other active injection systems cannot operate, in order to maintain coolant to the reactor for several days or weeks following such a transient. This is a patent document, and general broad rules of construction should be applied when reading and understanding it. Everything described and shown in this document is an example of subject matter falling within the scope of the appended claims. Any specific structural and functional details disclosed herein are merely for purposes of describing how to make and use example embodiments. Several different embodiments not specifically disclosed herein fall within the claim scope; as such, the claims may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). Similarly, a term such as “communicatively connected” includes all variations of information exchange routes between two devices, including intermediary devices, networks, etc., connected wirelessly or not. As used herein, the singular forms “a”, “an” and “the” are intended to include both the singular and plural forms, unless the language explicitly indicates otherwise with words like “only,” “single,” and/or “one.” It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, steps, operations, elements, ideas, and/or components, but do not themselves preclude the presence or addition of one or more other features, steps, operations, elements, components, ideas, and/or groups thereof. It should also be noted that the structures and operations discussed below may occur out of the order described and/or noted in the figures. For example, two operations and/or figures shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Similarly, individual operations within example methods described below may be executed repetitively, individually or sequentially, so as to provide looping or other series of operations aside from the single operations described below. It should be presumed that any embodiment having features and functionality described below, in any workable combination, falls within the scope of example embodiments. Applicants have recognized that plant emergency power systems, including local batteries and emergency diesel generators, may become unavailable in confounding combination with loss of access to the electrical grid during certain plant transients. That is, a transient event that cuts offsite power may also render unusable emergency diesel generators. In such a situation, active high-pressure injection systems, such as RCIC turbine 40 and pump 41, can provide fluid coolant flow to a reactor 10 to remove decay heat from the same for several hours; however, once reactor pressure falls below the high-pressure injection systems' operating pressure (typically within a day of the transient event), low-pressure injection systems must be initiated to provide liquid coolant makeup to reactor 10, which is still generating large amounts of decay heat. If emergency diesel generator and local power grid access are unavailable, conventional low-pressure injection systems cannot be operated, and battery-based systems are insufficient to prevent eventual loss of liquid coolant level in core 15 due to decay heat, greatly increasing the risk of fuel damage. As such, Applicants have recognized an unexpected need for reliable reactor liquid coolant injection that is available without batteries or the electrical power grid starting almost a day after, and continuing several weeks after, a transient event that cuts both offsite power and local emergency power generation. Applicants have identified that using a steam source, such as low pressure steam from reactor 10 at below 150 pounds/square inch, may power some devices capable of injecting liquid coolant into reactor 10, at lower but sufficient flow rates to prevent core 15 from becoming uncovered or overheated for weeks, with proper device and system engineering. Example embodiment systems and methods discussed below address and overcome these problems identified by Applicants in unique and advantageous ways. FIG. 2 is a schematic drawing of an example embodiment passive low-pressure injection system 100 useable in conventional and future water-cooled nuclear power plants. It is understood that although example embodiment 100 is shown using light water as a liquid coolant in a conventional BWR, other plant and coolant types are useable as example embodiments. Reference characters shared between FIGS. 1 and 2 label plant components that may be in existing systems, and whose redundant description is omitted. As shown in FIG. 2, example embodiment system includes a low-pressure injection device 110 that is operable to inject coolant from a source, such as suppression pool 30 and/or condensate storage tank 31, into reactor 10. Low-pressure injection device 110 is operable at pressures below those required to operate conventional high-pressure systems, such as RCIC turbine 40, in order to provide parallel cooling to reactor 10 at lower pressures. Low-pressure injection device 110 may be operable at pressures where conventional high-pressure systems operate, additionally allowing low-pressure injection device 110 to supplement such higher-pressure systems. For example, low-pressure injection device 110 may be a venturi device that receives steam from reactor 10, passes the steam through a venturi that accelerates the steam and causes a suction/pressure drop, thereby drawing and entraining liquid coolant from suppression pool 30 and/or or condensate storage tank 31, and then injects the resultant steam-liquid mixture into reactor 10 to makeup liquid coolant volume of reactor 10. Such an example venturi tube for low-pressure injection device 110 is shown in FIG. 3. For example, as shown in FIG. 3, relatively lower-pressure steam from a reactor 10 can be routed into venturi 110 from main steam diversion line 155. In a narrowing section 111 of venturi 110, the steam may increase velocity with resultant pressure drop, or suction, under Bernoulli's principle. In this example, the suction draws liquid coolant from suction diversion line 135 into venturi 110, where the coolant is entrained in the steam flow through venturi 110. Venturi 110 may include a diffuser section 112 that decreases flow velocity and increases pressure of the resulting liquid coolant/steam flow to that necessary for injection into reactor 10 via injection diversion line 142, or to some other desired pressure and velocity for compatibility with example embodiment systems. The liquid coolant may also condense a significant portion of steam flow through venturi 110 when mixing, yielding even more liquid coolant for injection into reactor 10. Venturi 110 may be sized in a diameter and length and otherwise configured, such as in angle of narrowing section 111 and/or presence of diffuser section 112, to provide desired flow characteristics to reactor 10 given the arrangement, parameters, and anticipated transient conditions of example embodiment system 100 in which venturi 110 operates. Venturi 110 generally includes few or no moving parts and may provide suction and liquid coolant entrainment/injection passively as long as a minimally pressurized steam flow from reactor 10 is connected to venturi 110. For example, venturi 110 may be operable to draw and entrain fluid from suppression pool 30/condensate tank 31 at about 150 to 50 pounds per square inch or less, well below an operating pressure of RCIC turbine 40. Similarly, venturi 110 may be operable at pressures well above 150 pounds per square inch to supplement or replace any RCIC turbine 40 and pump 41 or other high-pressure injection systems. Further, venturi 110 may have very few energy losses, permitting efficient energy transfer from pressurized steam flow to liquid coolant injection. For example, with typical decay heat generated by commercial nuclear reactors, venturi 110 may be able to reliably inject sufficient liquid coolant to maintain coolant level above core 15 for several days or weeks before pressure in reactor 10 would be inadequate to operate venturi 110 and maintain required liquid coolant injection. Additionally, venturi 110 may be relatively simple and reliable, requiring no outside power or moving parts, so as to present very little opportunity for failure, even in transients involving emergency conditions and total station blackout, with easy installation and fabrication. Although the example embodiment of FIG. 3 shows a particular venturi for low-pressure injection device 110, it is understood that other reliable low-pressure injection devices may be used instead of a venturi in example embodiment system 100. For example, low-pressure injection device 110 could be a choke plate, a nozzle, aspirator, and/or any other device that can reliably and passively drive liquid coolant into reactor 10 using only lower-pressure steam. In an example embodiment coolant system 100, low-pressure injection device 110 is connected to a steam source, a liquid coolant source, and a reactor inlet to deliver entrained liquid coolant. These sources and connections may be achieved in several flexible ways, depending on the arrangement of a reactor and associated coolant systems. As shown in FIG. 2, for example, low-pressure injection device 110 can be connected to a main steam line 50 of reactor 10, via RCIC line 55 and an isolated main steam diversion line 155. Suction diversion line 135 may connect low-pressure injection device 110 to liquid coolant sources such as suppression pool 30 and/or condensate makeup tank 31 via conventional suction line 35. Low-pressure injection device 110 may inject its entrained liquid coolant back into injection line 42 via injection diversion line 142 for delivery to reactor 10 through main feedwater line 60. Any or all of main steam diversion line 155, suction diversion line 135, and injection diversion line 142 may include valves that permit isolation or activation of low-pressure injection device 110 through automatic or manual valve activation. For example, simple swing check valves may be used in main steam diversion line 155, suction diversion line 135, and/or injection diversion line 142 to reliably operate low-pressure injection device 110 when desired. Of course, a venturi or other low-pressure injection device 110 may be placed in any configuration with access to a steam source, a liquid coolant source, and injection to reactor 10 in order to provide reliable low-pressure coolant injection in example embodiment system 100, in approximate parallel with conventional active emergency cooling systems. For example, low-pressure injection device 110 could be positioned directly between a heat sink and liquid coolant source, such as a river or lake, and an inlet of reactor 10 with access to any steam source in order to drive liquid coolant into reactor 10. Similarly, low-pressure injection device 110 could be positioned in direct parallel with RCIC turbine 40 and pump 41 and operate simultaneously with these or other systems, and/or be switched to exclusive use upon failure of these or other systems. Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied and substituted through routine experimentation while still falling within the scope of the following claims. For example, although example embodiments are described in connection with BWRs using light water as a liquid coolant in nuclear power plants, it is understood that example embodiments and methods can be used in connection with any reactor cooling system where energetic fluid input can be used to entrain and inject a coolant into the reactor or a heat sink/steam generator of the reactor, including heavy-water, gas-cooled, and/or molten salt reactors. For example, superheated helium coolant could be diverted from a pebble bed reactor output and into an example embodiment injection device such as an orifice plate or venturi and be used to passively draw and entrain colder helium or another fluid coolant for injection into the reactor with relatively low pressures to maintain core temperatures and/or coolant flow. Such variations are not to be regarded as departure from the scope of the following claims.
	claims	1. A system for encapsulating and storing radiological sources, the system comprising:a) a basket to removably position capsules relative to each other, the capsules containing the radiological sources;b) a containment vessel for reversibly receiving the basket; andc) a cask housing the containment vessel wherein the cask is surrounded in a framework of metal mesh. 2. The system as recited in claim 1 wherein the basket and the containment vessel are coaxially arranged. 3. The system as recited in claim 1 further comprising a means for transporting the framework. 4. The system as recited in claim 1 wherein the cask is removably received by the framework. 5. The system as recited in claim 1 wherein the basket symmetrically positions the capsules relative to each other. 6. The system as recited in claim 1 wherein the capsules are stacked on top of each other within the basket. 7. The system as recited in claim 1 wherein all of the components contain metal and the system has a 1000 W heat dissipation feature. 8. The system as recited in claim 1 wherein the basket comprises depleted uranium. 9. The system as recited in claim 1 wherein the framework comprises stainless steel webbing extending between horizontally and vertically disposed substrates. 10. The system as recited in claim 1 wherein the cask is removably received by the framework. 11. The system as recited in claim 1 further comprising a plurality of sensors attached to one of said cask, framework, or containment vessel. 12. The system as recited in claim 1 wherein the mesh defines a plane which enables airflow about the cask while simultaneously preventing personnel from inserting their hands through the plane. 13. The system as recited in claim 1 wherein the mesh provides crumple zones.
	summary
	description	The present invention refers generally to a spacer for holding a number of fuel rods in a nuclear plant of a light water type, especially a boiling water reactor, BWR, or a pressure water reactor, PWR. More specifically, the present invention refers to a spacer for holding a number of elongated fuel rods intended to be located in a nuclear plant, wherein the spacer encloses a number of cells, which each has a longitudinal axis and is arranged to receive a fuel rod in such a way that the fuel rod extends in parallel with the longitudinal axis, each cell is formed by a sleeve-like member, which has an upper edge and a lower edge, the sleeve-like member includes a number of elongated abutment surfaces, which project inwardly towards the longitudinal axis and extend substantially in parallel with the longitudinal axis for abutment to the fuel rod to be received in the cell, and the lower edge, seen transversely to the longitudinal axis, has a wave-like shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and wave valleys located between two adjacent ones of said abutment surfaces. The invention also refers to a fuel unit for a nuclear plant including a number of elongated fuel rods and a number of spacers for holding the fuel rods, wherein the spacers enclose a number of cells, which each has a longitudinal axis and is arranged to receive one of said fuel rods in such a way that the fuel rod extends in parallel to the longitudinal axis, each cell is formed by a sleeve-like member, which has an upper edge and a lower edge, the sleeve-like member includes a number of elongated abutment surfaces, which project inwardly towards the longitudinal axis and extend substantially in parallel with the longitudinal axis for abutment to the fuel rod to be received in the cell, and the lower edge, seen transversely to the longitudinal axis, has a wave-like shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and wave valleys located between two adjacent ones of said abutment surfaces. In a reactor for a nuclear plant of the type defined above, a large number of elongated fuel units are arranged in the core of the reactor. Each fuel unit includes a number of elongated fuel rods. Each fuel rod includes an elongated cladding tube and a number of fuel pellets, which are provided in a pile in the cladding tube. The fuel rods in the fuel unit are maintained by means of a number of spacers, for instance 6-10 spacers, which are distributed along the length of the fuel unit. Each spacer defines cells for receiving the fuel rods. The spacers thus hold the fuel rods in a correct position in the fuel unit and have the function to ensure the maintaining of a constant mutual distance between the fuel rods during the operation of the reactor. In a boiling water reactor, the fuel rods are normally enclosed in casings, so called boxes. Each box includes a relatively large number of fuel rods and forms together with these fuel rods a so-called fuel assembly, which can be lifted into and out of the core of the reactor. Each fuel assembly may include one or several fuel units. JP-7225291 discloses a fuel assembly having one such fuel unit. U.S. Pat. No. 5,875,223 discloses a fuel assembly having four such fuel units. The core is submerged in a coolant, normally water, which functions both as coolant and as moderator. The fuel units and fuel rods are normally provided substantially vertically in the reactor. The coolant normally flows from below and upwardly. It is important to maintain a proper cooling of the fuel rods in the reactor. In a boiling water reactor it is especially critical to obtain a proper cooling in the upper part of the fuel rods where a significant part of the coolant (water) has been converted to steam. In the upper part of the fuel assembly, the coolant thus prevails in a two-phase state, wherein the liquid state partly flows as a film on the different parts of the fuel assembly, inter alia the surfaces of the fuel rods, the spacers and the inner side of the casing, and partly as droplets in the steam flow. If the coolant film on the surfaces of the fuel rods is not maintained an isolating steam layer is formed on the fuel rod leading to a quick temperature increase, so called dry-out, which can lead to defects of the cladding tubes. The design of the spacers influences the flowing of the coolant and thus the cooling of the fuel rods. It is known to provide the spacers with deflection members provided for deflecting the coolant towards the fuel rods. Such deflecting members have the disadvantage that they, if they are used to a too large extent, result in a substantial increase of the pressure drop coefficient of the spacer. The percentage of steam is highest in the upper part of the fuel assembly. Due to the high percentage steam in the upper part of the fuel assembly, the pressure drop frequently is higher in this part than in the lower part of the fuel assembly. The larger the difference in pressure drop between the upper part of the fuel assembly and lower part, the higher the risk that the core becomes unstable. In order to give the fuel assembly proper stability properties, it is aimed at a low-pressure drop in the upper part of the fuel assembly. There are spacers of a plurality of different types, for instance spacers formed by crossing sheets, spacers where the cells are formed by open elements having support points and spring members and spacers formed by sleeve-like members welded together. The spacers used today are normally manufactured of zirconium-based alloys (Zircaloy), nickel-based alloys (Inconel), combinations of these alloys or stainless steel. The present invention refers to a spacer formed by sleeve-like members. A spacer of the kind initially defined is disclosed in U.S. Pat. No. 5,875,223. The known spacer thus includes welded sleeves forming the cells mentioned above. Each of the sleeves has a lower edge and an upper edge. The upper edge is parallel to a plane whereas the lower edge has a wave-shape with wave peaks and wave valleys. The purpose of this design of the lower edge is to prevent possible debris particles in the coolant from getting caught in the spacer, and thus to reduce the wear of the fuel rods. JP-6-148370 discloses a sleeve spacer for a boiling water reactor. Each sleeve has inwardly directed projections for abutting the fuel rod extending through the sleeve. The projections extend merely over a small part of the length of the sleeve. Each sleeve is also, according to one example, at the lower end provided with a bevel. According to another example, each sleeve has a wave shape at the lower end of the sleeve. JP-7-225291 discloses another sleeve spacer for a boiling water reactor. The circular cylindrical sleeves are here provided with an upper, downstream end, which has triangular or rectangular projections extending upwardly. The lower end of the sleeve appears to be straight. Each sleeve may also include inwardly directed projections, which extend over merely a part of the length of the sleeve for abutting the fuel rod extending through the sleeve. U.S. Pat. No. 5,331,679 discloses a further variant of a sleeve spacer having substantially circular cylindrical sleeves. The spacer is kept together by means of a band extending around the outer periphery of the spacer. Each sleeve has relatively short inwardly directed projections, which together with a spring element form abutment points against the fuel rod extending through the sleeve. Both the lower edge and the upper edge may, according to one embodiment, have a wave-like shape with wave peaks and wave valleys. The wave peaks of the upper edge appear to be aligned to a respective wave valley of the lower edge. When designing a spacer, consideration has to be taken to a plurality of different requirements, which at least partly are contradictory. 1) The spacer shall be sufficiently mechanically strong to reduce the bending and vibration of the fuel rods and to resist large thermal and hydraulic forces also at dimensioning events such as plant accidents and earthquakes. 2) The spacer has to be able to resist axial and radial dimension changes of the fuel rods. 3) The spacer has to give sufficient abutment surface to the fuel rods for minimizing local wear and the risk for defects of the fuel rods. 4) The spacer shall be provided with a minimal amount of material for minimizing the neutron absorption. 5) The spacer shall be designed to give a minimal flow resistance and thus a small pressure drop. 6) The spacer shall be designed in such a way that possible debris particles in the coolant do not get caught in the spacer in such a way that these debris particles can subject the fuel rods to wear. 7) The spacer shall be designed in such a way that it provides a proper cooling of the fuel rods through a suitable mixing of the coolant. 8) The spacer shall be manufactured in a relatively easy and inexpensive manner. The object of the present invention is to provide a spacer, which has a mechanical strength for reducing the bending and the vibration of the fuel rods, and for resisting large thermal and hydraulic forces, and which withstand axial and radial dimension changes of the fuel rods. A further object is to provide a spacer having a large abutment surface against the fuel rods for minimizing local wear and risk for defects on the fuel rods. A further object is to provide a spacer requiring a small amount of material in order to minimize the neutron absorption. A further object is to provide a spacer giving a low flow-resistance. A further object is to provide a spacer, which ensures a proper cooling of the fuel rods. The purpose is achieved by the spacer initially defined, which is characterized in that the upper edge, seen transversely to the longitudinal axis, has a wave-like shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and with wave valleys located between two adjacent ones of said abutment surfaces. In such a spacer, the sleeve-like members thus have abutment surfaces, which have a long axial extension that ensures a long abutment line against the fuel rod extending through the sleeve-like member. The abutment line is especially long in relation to the length and weight of the sleeve-like member. By such a long abutment a small wear of the cladding tube of the fuel rod is achieved. Furthermore, each such sleeve-like member has, on each side of each abutment surface, i.e. at the wave valleys, a significantly shorter extension than at the abutment surfaces and the wave peaks, wherein the abutment surfaces advantageously extend from the upper edge to the lower edge of substantially each sleeve-like member. In addition, by such a design a flexibility of the sleeve-like member is obtained in such a way that the fuel rods and the abutment surfaces may move radially inwardly and outwardly and at the same time the abutment surfaces are permitted to rotate around a center point in a radial plane. The sleeve-like member thus permits a certain inclination of fuel rod. Consequently, a uniform abutment against a fuel rod is achieved along the whole length of the abutment surface also at a bending outwardly of the fuel rod or at other axial and/or radial dimension changes of the fuel rod. The wave-like shape at the lower edge also reduces the risk for possible debris particles to get clogged in the spacer and to wear against the fuel rod. According to an embodiment of the invention, each sleeve-like member includes at least four of said abutment surfaces. According to a further embodiment of the invention each of said abutment surfaces is formed by a respective ridge projecting inwardly towards the longitudinal axis. According to a further embodiment of the invention, the sleeve-like members abut each other in the spacer along a connection area extending in parallel to the longitudinal axis between one of said wave valleys of the upper edge and one of said wave valleys of the lower edge. Advantageously, the sleeve-like members may also be permanently connected to each other by means of weld joints, wherein said weld joint may include an edge weld at said connection area at at least one of the upper edge and the lower edge. According to a further embodiment of the invention, substantially each sleeve-like member is manufactured from a sheet-shaped material, which is bent to the sleeve-like shape. Such a sheet-shaped material, for instance, in the form of a band may in an easy manner be worked and given a desired shape along the upper edge and the lower edge. After such a shaping, the sheet-shaped material may be bent to the sleeve-like shape. Advantageously, the sheet-shaped material may, before said bending, have a first connection portion in the proximity of a first end of the sheet-shaped material and a second connection portion in the proximity of a second end of the sheet-shaped material, wherein the first end overlaps the second end of the sleeve-like member after said bending. The first connection portion and the second connection portion are preferably permanently joined to each other by means of one weld joint, for instance at least one spot weld. According to a further embodiment of the invention, substantially each sleeve-like member is manufactured from a tubular material, which is worked to the wave-like shape of the upper edge and the lower edge. According to this embodiment, it is thus started in a more conventional manner from a tubular material, which is cut to suitable lengths, wherein the upper edge and the lower edge are worked to a suitable shape. According to a further embodiment of the invention, the sleeve-like member, seen in the direction of the longitudinal axis, has four substantially orthogonal long sides, wherein each long side includes one of said abutment surfaces. Such long sides provide a suitable elasticity of the sleeve-like member and especially of the abutment surfaces to abut the fuel rod. Each long side may then include one of said wave peaks of the upper edge and one of said wave peaks of the lower edge. Furthermore, the sleeve-like member, seen in the direction of the longitudinal axis, advantageously has four substantially orthogonal short sides, wherein each short side connects two of said long sides and includes with a portion of one of said wave valleys of the upper edge and a portion of one of said wave valleys of the lower edge. Said edge portion may be substantially straight and perpendicular to the longitudinal axis, and is thus suitable for being welded with a corresponding portion of an adjacent sleeve-like member. According to a further embodiment of the invention, the sleeve-like member has a thickness of material, which is less than 0.24 mm, preferably less than or equal to 0.20, and more preferably less than or equal to 0.18 mm. By such a thin thickness of material, two substantial advantages are achieved, namely a small amount of material of the spacer, which gives a low neutron absorption, and a low flow resistance through the spacer, which contributes to a low pressure drop in the reactor. A thin thickness of material also contributes to the achievement of the above mentioned flexibility of the sleeve-like member and to make the sleeve-like member less rigid, which facilitates the introduction of the fuel rods when the fuel unit is mounted. The nuclear plant is arranged to permit re-circulation of a coolant flow and the spacer is arranged to be located in this coolant flow, wherein the spacer according to a further embodiment of the invention may include at least one vane for influencing the coolant flow. Such an influence may include guiding of a coolant flow in a direction towards at least one adjacent fuel rod and/or creating turbulence in the coolant flow. In such a way, a proper cooling is ensured and dry-out prevented. Advantageously, said vane is formed by portion of material, which extends from the first connection portion. Such a vane may in an easy manner be provided in connection with the manufacturing of the sleeve-like member and the shaping of the sheet-shaped material to be bent to the sleeve-like member. In connection with this bending operation, also the vane may be bent to a suitable angle. The sleeve-like member may, however, also include a slit, which extends from at least one of the upper and lower edges and which permits bending outwardly of a part of the sleeve-like member for forming said vane. Advantageously, said vane is inclined in relation to the longitudinal axis. Furthermore, said vane may suitably extend outwardly from one of said long sides. According to a further embodiment of the invention, the spacer, seen in the direction of the longitudinal axis, has a substantially rectangular shape and includes at least two separate outer edge elements, which extend along a respective side of the space. Such edge elements contribute to an increased strength of the spacer and to hold the sleeve-like members together. The edge elements may also advantageously provide surfaces arranged to facilitate the introduction of the fuel unit in the initially mentioned casing and to create a hydraulic damping to the inner wall of the casing during operation of the plant. According to a further embodiment of the invention, one of said four corners is reduced by the lack of an outer sleeve-like member, wherein the spacer includes a separate inner edge element extending along two of said sides and along said reduced corner. The inner edge element may then include a vane, which is located at said reduced corner and which slopes upwardly and inwardly towards a centre of the spacer. A spacer for holding a number of elongated fuel rods encloses a number of cells, each having a longitudinal axis and arranged to receive a fuel rod in such a way that the fuel rod extends substantially in parallel with the longitudinal axis. Each cell is formed by a sleeve having an upper edge and a lower edge. The sleeve includes a number of elongated abutment surfaces, which project inwardly towards the longitudinal axis and extend substantially in parallel with the longitudinal axis for abutment to the fuel rod. The lower edge, seen transversely to the longitudinal axis, has a wave shape with wave peaks, which are aligned with a respective one of the elongated abutment surfaces, and wave valleys located between two adjacent ones of the elongated abutment surfaces. The upper edge, seen transversely to the longitudinal axis, has a wave shape with wave peaks, which are aligned with a respective one of the elongated abutment surfaces, and with wave valleys located between two adjacent ones of the elongated abutment surfaces. Each of the elongated abutment surfaces extend from a respective one of the wave peaks of the upper edge to a respective one of the wave peaks of the lower edge. The sleeves abut each other in the spacer along respective connection areas, each extending substantially parallel to the longitudinal axis between one of the wave valleys of the upper edge and one of the wave valleys of the lower edge. The connection area has a length and the sleeve has a thickness, the length of the connection area and the thickness of the sleeve being configured to make the elongated abutment surfaces rotatable with respect to a center point of the connection area. The object is also achieved by the fuel unit initially defined, which is characterized in that the upper edge, seen transversely to longitudinal axis, has a wave-like shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and with wave valleys located between two adjacent ones of said abutment surfaces. FIG. 1 discloses schematically a nuclear plant including a reactor 1. The reactor 1 includes a reactor vessel 2 enclosing a core. The core 3 includes a number of fuel assemblies 4, which each includes a number of fuel rods 5, see FIGS. 2 and 3. Each fuel rod 5 includes a cladding tube and a nuclear fuel in the form of a pile with fuel pellets (not disclosed), which are enclosed in the cladding tube. Through the nuclear plant a coolant, in this case water, is flowing, which is heated by the nuclear reaction in the nuclear fuel. The coolant flows through the core 3 and into each fuel assembly 4 in contact with each fuel rod 5. The heated coolant is conveyed via a first connection 10 to a plant 11 for obtaining heat energy from the coolant. The plant 11 may include a turbine and a condenser. The cooled coolant is conveyed back to the reactor via a second connection 12. The reactor 1 may be of a boiling water type, BWR, wherein the coolant is vaporized in the core 3 and conveyed to the plant 11 as steam for driving a steam turbine. The reactor 1 may also be of a pressure water type, PWR, wherein the coolant is not vaporized but conveyed to a heat exchanger of the plant 11 for vaporizing a medium in another circuit including a turbine. FIG. 2 discloses schematically a fuel assembly 4 for a boiling water reactor. In the embodiment disclosed, the fuel assembly 4 includes four fuel units 20, which each includes a plurality of fuel rods 5 and is located in a respective space in a box 21. Between these spaces and the four fuel units 20 coolant channels extend. Each fuel unit 20 is kept together by means of a number of spacers 30, for instance six to ten spacers 30. A fuel assembly 4 with this principle design is disclosed in the initially mentioned document U.S. Pat. No. 5,875,223. FIG. 3 discloses schematically a fuel assembly 4 for a pressure water reactor. The fuel assembly 4 includes a fuel unit 20, which includes a plurality of fuel rods 5. The fuel assembly 4 normally includes an upper tie plate 25, a lower tie plate 26 and a number of guide tubes 27, which extend between and connect the tie plates 25 and 26 and which may be arranged to receive a control rod (not disclosed). The fuel rods 5 in the fuel unit 20 are kept together by means of a number of spacers 30, for instance six to eight spacers 30. The fuel unit 20 is also connected to the guide tubes 27 via the spacers 30 in a manner known per se. The design and the manufacturing of the spacers 30 are now to be explained more closely with reference to FIGS. 4-13. In the embodiment disclosed in FIGS. 4-13, the spacers 30 are intended for a fuel assembly 4 for a reactor 1 of a boiling water type and including four fuel units 20. However, it is to be noted that the invention also is applicable to fuel assemblies intended for boiling water reactors and including another number than four fuel units, for instance one fuel unit. The invention is also applicable to fuel assemblies 4 for reactors 1 of pressure water type, see FIG. 3. The spacer 30 encloses a number of cells 31, which each has a longitudinal axis x, see FIG. 6, which is intended to extend substantially vertically when the fuel unit 20 is located in a reactor 1. Each such cell 31 is in the embodiment disclosed arranged to receive a fuel rod 5 in such a way that the fuel rod 5 extends in parallel with the longitudinal axis x. As illustrated in FIG. 6, the connection area 41 has a first length L1 parallel to the axis X and between the wave valleys 37 of the upper edge 33 and the wave valleys 37 of the lower edge 34. A second length L2 is defined between the wave peaks 36 of the upper edge 33 and wave peaks 36 of the lower edge 34. The first length L1 is less than the second length L2. The first length L1 has a magnitude configured to make the elongated abutment surfaces 35 rotatable with respect to a center point 80 of said connection area 41, for example in the direction indicated by the arrow A, to minimize wear of the fuel rod 5. Each cell 31 is formed by a sleeve-like member 32, see FIGS. 6-9, which has an upper edge 33 and a lower edge 34. The sleeve-like member 32 also includes four elongated abutment surfaces which are adapted to abut the fuel rod 5 extending through the cell 31. These abutment surfaces may be designed in various ways, for instance as substantially plane surfaces or curve surfaces, e.g. ridges 35. In the embodiments disclosed, the abutment surfaces are formed by four such elongated ridges 35 projecting inwardly towards the longitudinal axis x and to the fuel rod 5 extending through the cell 31. Each ridge 35 extends substantially in parallel with the longitudinal axis x along substantially the whole length of the sleeve-like member 32 from the upper edge 33 to the lower edge 34. Thanks to the fact that the ridges 35 project towards the fuel rod a relatively wide gap is created between the fuel rod 5 and the sleeve-like member in the proximity of the ridges 35. In such a way a proper cooling is ensured. The upper edge 33 and the lower edge 34 have, seen transversely to the longitudinal axis x, a wave-like shape with wave peaks 36 and wave valleys 37. The wave peaks 36 of the upper edge 33 are aligned with a respective wave peak 36 of the lower edge 34 and with a respective one of the ridges 35. The wave valleys 37 of the upper edge 33 are aligned with a respective wave valley 37 of the lower edge 34. The wave valleys 37 are located between two adjacent ridges 35. Each sleeve-like member 32 has, seen in the longitudinal direction of the axis x, four substantially orthogonal long sides 40, which each includes one of the ridges 35. Each long side 40 thus also includes one of the wave peaks 36 of the upper edge 33 and one of the wave peaks 36 of the lower edge 34. Furthermore, each sleeve-like member 32 has, seen in direction of the longitudinal axis x, four substantially orthogonal short sides 41. Each short side 41 connects two of the long sides 40. Each sleeve-like member 32 thus has, seen in the direction of the longitudinal axis x, an octagonal basic shape, see FIG. 7. However, it is to be noted that this basic shape may vary, for instance the sleeve-like members 32 may have a more circular cylindrical shape or a more square shape. Each short side 41 includes a portion of one of the wave valleys 37 of the upper edge 33 and a portion of one of the wave valleys 37 of the lower edge 34. These portions are substantially straight and perpendicular to the longitudinal axis x. The sleeve-like members 32 abut, as appears from FIG. 5, each other in the spacer 30 along a connection area formed by the short sides 41 of two adjacent sleeve-like members 32. This connection area thus extends in parallel to the longitudinal axis x between the above-mentioned portion of one of wave valleys 37 of the upper edges 33 and the above-mentioned portion of one the wave valleys 37 of the lower edges 34. Furthermore, the sleeve-like members 32 are permanently connected to each other by means of weld joints. Each such weld joint includes an edge weld at said connection area of at least one of the upper edge 33 and the lower edge 34. Preferably one such edge weld is provided both at the upper edge 33 and the lower edge 34. Since the edge welds in this case are located at the opposite wave valleys 37 they will be relatively close to each other which is advantageous from a strength point of view. The substantially straight portions are suitable for the application of such edge welds. The spacer 30 has, seen in the direction of the longitudinal axis x, a substantially square shape, see FIG. 5. The spacer 30 includes at least two separate outer edge elements 50, which extend along a respective side of the spacer 30. One such outer edge element 50 is disclosed more closely in FIGS. 10 and 11. The spacer 30 also includes a separate inner edge element 51, which extends along two of the sides of the spacer 30. The inner edge element 51 is disclosed more closely in FIGS. 12 and 13. The edge elements 50, 51 thus create a non-closed or open frame contributing to the strength of the spacer 30 and providing outer surfaces 52 of the spacer 30. These outer surfaces 52 facilitate the introduction of the fuel unit 20 into the box 21 and create a hydraulic damping to the inner wall of the box 21. Thanks to the fact that the frame is open in three corners, the sleeve-like members 32 in these corners are permitted to move elastically outwardly. As is clear from FIG. 4, the edge elements 50, 51 have a longer extension in a vertical direction, i.e. in parallel with the longitudinal axis x, than the sleeve-like members 32. In particular, the edge elements 50, 51 extend a significant distance above the upper ends of the sleeve-like members 32, which is located at the level of the wave peaks 36. As is clear from FIG. 5, one of the four corners of the spacer 30 is reduced through the lack of one outer sleeve-like member 32. The purpose of this reduction is to create space for a central water channel through the box 21. The inner edge element 51 extends around the reduced corner. The inner edge element 51 thus is turned inwardly in the box 21 to the central water channel. The inner edge element 51 also includes a vane 53, which is located at said reduced corner and which is inclined upwardly and inwardly to a centre of the spacer 30. The sleeve-like members 32 are manufactured in a nickel-based alloy such as Alloy X-750, Alloy 718, Alloy 650, Alloy 690 or Alloy 600. The sleeve-like members 32 may also be manufactured in a zirconium-based alloy, such as various types of Zircaloy alloys, in stainless steel or in combinations of these alloys. An important aspect is however that the sleeve-like members 32 are to have a small thickness of material, which is less than 0.24 mm, less than or equal to 0.20 mm or less than or equal to 0.18 mm. According to a first alternative the sleeve-like member 32 is manufactured in a sheet-shaped material in the form of a sheet band 60, see FIGS. 8 and 9. The sheet band 60 has the thickness of material mentioned above. During the manufacturing a sheet is worked to the sheet band 60 with the shape disclosed in FIGS. 8 and 9, for instance by means of punching. The sheet band 60 is then bent to the sleeve-like shape. The sheet band 60 has before this bending a first connection portion 61 in the proximity of a first end of the sheet band 60 and a second connection portion 62 in the proximity of the second end of the sheet band 60. The sheet band 60 is bent in such a way that, after the bending, the first connection portion 61 overlaps the second connection portion 62. After the bending, the connection portions 61 and 62 are connected to each other through the application of a weld joint, for instance in the form of two spot welds 63, which extend through the two portions 61 and 62, see FIG. 6. Since the sheet band 60 has a small thickness of material, the above-mentioned overlap may be permitted with the maintenance of a total small amount of material of the sleeve-like member 32 and without any negative effect on the flow resistance. The manufacturing of the sleeve-like member 32 is with this method very easy and the upper and lower edges 33, 34 may in an easy manner be given the disclosed wave-like shape. A further advantage is that the size of sleeve-like member 32 with regard to the outer diameter seen in the direction of the longitudinal axis x may vary in an easy manner. This is essential since the sleeve-like members 32 in a spacer normally include sleeve-like members 32 with different diameters. During the manufacturing of the spacer, the different sheet bands 60 are thus bent in the manner described above. Advantageously, the individual bent sheet bands 60 are welded by means of the above-mentioned spot weld or spot welds 63 for keeping the sleeve-like members 32 together during the mounting of the spacer 30 proper. However, it is possible to replace this or these spot welds 63 with a more or less temporary connection during the mounting of the spacer 30 proper, for instance brazing. The sleeve-like members 32 are then positioned in a fixture of the like in the position it is to have in the spacer 30. Thereafter, the sleeve-like members 32 are welded together by means of the above-mentioned edge welds along said portions of the wave valleys 37. The edge welds may advantageously be performed as melt welds by means of laser welding or electron-beam welding. It is also possible to position the bent sheet bands 60 directly in a fixture which keeps these during the welding by means of the above-mentioned edge welds, i.e. without any joining of the end portions 61, 62 of the sheet bands 60. The edge elements 50, 51 may then be positioned against the sleeve-like members 32 in the above-mentioned fixture or the like and welded to the sleeve-like members 32 in connection with the application of said edge welds. It is also possible to apply and weld the edge elements 50, 51 firstly after the sleeve-like members 32 have been welded to each other. According to a second alternative, the sleeve-like member 32 is manufactured from a tubular material having the above-mentioned thickness of material. The tubular material may be cut to a suitable size whereafter the upper edge 33 and the lower edge 34 are worked to the wave-like shaped disclosed. The disclosed ridges may be obtained through a pressing operation or be provided on the original tubular material. At least some of the spacers 30 in the fuel unit 20 include one or several vanes 70 for influencing the coolant flow. With such a vane 70, the coolant may for instance be guided in a direction towards at least one adjacent fuel rod 5. With such a vane 70, turbulence in the coolant flow may also be created. Advantageously, such a vane 70 is formed by a portion 64 of material, which extends from the first connection portion 61, see FIG. 8. Such a vane 70 may be manufactured in an easy manner through a bending outwardly of the portion of material 64 outside the first connection portion 61 along a folding line 71 in such a way that the vane 70 extends outwardly form one of the long sides 40 and is inclined in relation to the longitudinal axis x. According to another embodiment, the sleeve-like member 32 may include a slit 72. The slit 72 extends from the upper edge 33 and/or the lower edge 34 and is bendable along a folding line 73, see FIG. 8. The slit 72 permits bending outwardly of a part of a sheet band 60 of the tubular material for forming of a vane, see also WO02/03394, which discloses how such a vane may be provided. The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. For instance it is to be noted that the wave shape defined may include all imaginable wave shapes, such as a pure sinus wave, a square wave, a triangular wave and mixtures of these shapes.
	claims	1. A method of controlling the reactivity of a molten salt fission reactor, wherein the molten salt fission reactor comprises a core and a coolant tank, the core comprising fuel tubes containing a molten salt fissile fuel, and the coolant tank containing a molten salt coolant, wherein the fuel tubes are immersed in the coolant tank, the method comprising:dissolving a neutron absorbing compound in the molten salt coolant, the neutron absorbing compound comprising a halogen and a neutron absorbing element; andreducing the neutron absorbing compound to a salt of the halogen and an insoluble substance comprising the neutron absorbing element, the halogen being fluorine or chlorine, wherein the insoluble substance is insoluble in the molten salt coolant and not volatile at a temperature of the coolant during operation of the reactor,wherein the neutron absorbing element has a Pauling electronegativity of greater than 1.5 and is a neutron absorber. 2. The method of claim 1, wherein the step of reducing the neutron absorbing compound comprises adding a reducing agent to the molten salt coolant. 3. The method of claim 1, wherein the step of reducing the neutron absorbing compound comprises electrochemical reduction of the neutron absorbing compound. 4. The method of claim 1, further comprising extracting the insoluble substance from the coolant. 5. The method of claim 4, wherein extracting the insoluble substance comprises any one or more of:withdrawing the insoluble substance from the top or bottom of the coolant;filtration;sedimentation;centrifugation;sparging with inert gas. 6. The method of claim 3, further comprising extracting the insoluble substance from the coolant, wherein the step of removing the insoluble substance comprises collection of the insoluble substance on an electrode. 7. The method of claim 1, wherein the neutron absorbing compound is a metal halide, the neutron absorbing element being a metal, and the insoluble substance being the pure metal or an insoluble salt of the metal. 8. The method of claim 7, wherein the metal is any one of indium and silver. 9. The method of claim 1, wherein the neutron absorbing compound is a haloborate salt, the haloborate being fluoroborate or chloroborate, the neutron absorbing element is boron, and the insoluble substance is an insoluble boride. 10. The method of claim 2, wherein the neutron absorbing compound is a haloborate salt, the haloborate being fluoroborate or chloroborate, the neutron absorbing element is boron, the insoluble substance is an insoluble boride and the reducing agent is thorium, zirconium or zirconium difluoride. 11. A nuclear fission reactor comprising:a core comprising fuel tubes containing a molten salt fissile fuel;a coolant tank containing a molten salt coolant, wherein a neutron absorbing compound is dissolved in the molten salt coolant, the neutron absorbing compound comprising a halogen, the halogen being fluorine or chlorine, and a neutron absorbing element;wherein the fuel tubes are immersed in the coolant; anda reduction unit configured to reduce the neutron absorbing compound to a salt of the halogen and an insoluble substance comprising the neutron absorbing element wherein the insoluble substance is insoluble in the molten salt coolant and not volatile at a temperature of the coolant during operation of the reactor;wherein the neutron absorbing element has a Pauling electronegativity of greater than 1.5. 12. A nuclear fission reactor according to claim 11, and comprising a neutron absorber addition unit configured to dissolve a neutron absorbing compound in the molten salt coolant, the neutron absorbing compound comprising a halogen and a neutron absorbing element. 13. A nuclear fission reactor according to claim 11 wherein the reduction unit comprises:an inlet configured to be immersed in a pool of coolant salt of the nuclear fission reactor;a mixing chamber configured to mix coolant drawn through the inlet with a reducing agent in order to reduce a neutron absorbing compound within the coolant salt into an insoluble substance containing a neutron absorbing element of the neutron absorbing compound, and a salt;a filtration unit configured to filter the insoluble substance from the coolant salt;an outlet configured to return the filtered coolant salt to the pool of coolant salt; anda pump configured to cause a flow of coolant salt from the pool through the outlet, then into the mixing chamber, then into the filtration unit, then out of the outlet. 14. A nuclear fission reactor according to claim 11, wherein the reduction unit comprises:an anode and a cathode, each of which is immersed in the coolant; anda voltage regulator configured to supply a voltage between the anode and cathode sufficient to electrolyse the neutron absorbing compound and insufficient to electrolyse other components of the molten salt coolant.
	claims	1. A method of calibrating exit thermocouples distributed over a plurality of fuel assemblies in a nuclear reactor comprising the steps of: repetitively recording temperatures measured by the thermocouples as reactor power increases during power ascension; generating calibration factors from the temperatures measured during startup; and applying the calibration factors to subsequent measurements of temperature taken by the thermocouples. 2. The method of claim 1 wherein: claim 1 recording includes recording with each temperature measured for each thermocouple, the reactor power level at the time of the measurement and a predicted power at the thermocouple at the time of the temperature measurement using a three-dimensional nodal model of the reactor core; generating calibration factors comprises generating a measured thermocouple power from each temperature measured for each thermocouple, generating a mixing factor for each temperature measured for each thermocouple by dividing the measured thermocouple power for each temperature measured for each thermocouple into the corresponding predicted power, and for each thermocouple fitting the mixing factors to a selected mixing factor function of reactor power; and applying the calibration factors comprises, for each subsequent thermocouple temperature measurement, converting the temperature measurement to a measured thermocouple power and adjusting the measured thermocouple power by a mixing factor value determined from the selected mixing factor function of reactor power for that thermocouple. 3. The method of claim 2 wherein the selected mixing factor function of reactor power is one of a linear function and a constant. claim 2 4. The method of claim 2 wherein the selected mixing factor function of reactor power is a quadratic function. claim 2 5. The method of claim 4 wherein the selected mixing factor function of reactor power is a linear function below a selected reactor power level and is then a said quadratic function. claim 4 6. The method of claim 5 including periodically adjusting the selected mixing factor function of reactor power for each thermocouple. claim 5 7. The method of claim 6 wherein adjusting the selected mixing factor function of reactor power comprises periodically generating a flux map of the reactor core at certain conditions, using the flux map and the three-dimensional nodal model at said certain conditions of the reactor core to generate a reference measured power distribution for the reactor core, generating a thermocouple measured temperature for each thermocouple at said certain conditions, converting each thermocouple measured temperature to a reference thermocouple power, establishing for each thermocouple an associated reference mixing factor by dividing a reference measured power for the thermocouple determined from the reference measured power distribution by the reference thermocouple power and adjusting the selected mixing factor function of reactor power for each thermocouple to pass through the associated thermocouple reference power. claim 6 8. The method of claim 7 comprising periodically adjusting the selected mixing factor function of reactor power for each thermocouple. claim 7 9. The method of claim 8 including periodically adjusting the selected mixing factor functions of reactor power for each thermocouple during startup. claim 8 10. The method of claim 7 including periodically adjusting the selected mixing factor functions of reactor power multiple times during startup. claim 7 11. The method of claim 7 comprising periodically adjusting the selected mixing factor functions of reactor power for the thermocouples after initial power ascension. claim 7 12. The method of claim 2 further including generating standard deviations for each mixing factor for each thermocouple for each measured temperature, fitting all of the standard deviations to a single selected function of assembly power. claim 2 13. The method of claim 10 wherein the selected function of assembly power is one of a quadratic function and a linear function of assembly power. claim 10 14. The method of claim 1 wherein the step of repetitively recording temperatures measured by the thermocouples as power increases during power ascension comprises recording temperatures for discrete ranges of power during power ascension and limiting the number of measured temperatures recorded for each range of power. claim 1 15. The method of claim 14 wherein recording temperatures for discrete ranges of power during power ascension comprise recording temperatures for ranges of about 5% power. claim 14 16. The method of claim 12 including determining the quality of the thermocouple data by using the standard deviations. claim 12
051006111	abstract	A fuel assembly for a light-water nuclear reactor contains a plurality of vertical fuel rods which are arranged, mutually spaced from each other in the lateral direction, between a bottom tie plate and a top tie plate. The bottom tie plate is provided with through-holes for conducting water through the bottom tie plate and into the spaces between the fuel rods. The through-holes in the bottom tie plate have parts, the centre lines of which are displaced in relation to each other or make an angle with each other.
	description	This application claims priority from prior Japanese Patent Application No. 2016-116148 filed with the Japan Patent Office on Jun. 10, 2016, the entire contents of which are incorporated herein by reference. The present disclosure relates to an inspection apparatus that uses radioactive rays. Inspection techniques known in the art may use image information obtained from X-ray imaging of an inspection object to perform non-destructive inspection of the object. For example, Patent Literature 1 describes a technique for reconstructing three-dimensional (3D) data representing components mounted on a substrate with X-ray computed tomography (CT), and determining whether, for example, the solder is defective or non-defective based on the 3D data. This type of X-ray inspection apparatus, which can inspect the internal structure or the microstructure of the object with high accuracy, is now used in, for example, automatic inspection performed in production lines of various industrial products. In-line inspection apparatuses may minimize the cycle time for inspection to prevent delays in the inspection process. A known structure as described in Patent Literature 2 uses two feeding lines arranged in parallel (referred to as dual lanes), on one of which an inspection object is inspected, and on the other one of which a subsequent inspection object is fed to the inspection position at the same time. This structure achieves substantially close-to-zero time taken for feeding the object to the inspection position. However, an X-ray inspection apparatus having this structure receives a subsequent inspection object fed into the apparatus during irradiation of X-rays. The X-ray inspection apparatus may thus have the structure for preventing X-rays from leaking outside the apparatus. An inspection apparatus described in Patent Literature 3 includes two shutters for each of a feed-in unit and a feed-out unit to prevent an imaging unit from being exposed outside when an inspection object is fed in and fed out. This apparatus allows smooth reception and discharge of an inspection object while preventing leakage of X-rays. Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2009-156788 Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2000-12999 Patent Literature 3: Japanese Unexamined Patent Application Publication No. 2014-098567 However, the use of a plurality of shield shutters as in the inspection apparatus described in Patent Literature 3 complicates the structure of the shutters and their control, and increases the cost of the apparatus. Also, the dual lane structure combined with the technique described in Patent Literature 3 can increase the size of the shutters, and lower the inspection speed. In response to this issue, one or more aspects of the present invention are directed to a technique for shortening the inspection time and preventing leakage of radioactive rays in an inspection apparatus that uses radioactive rays. The inspection apparatus according to a first embodiment of the present invention includes three compartments, namely, a feed-in preparation chamber, an imaging chamber, and a feed-out preparation chamber. In detail, each of the feed-in preparation chamber and the feed-out preparation chamber includes a feed-in unit that receives an inspection object through a first opening, a traverser that translates the received inspection object to a second opening in a direction different from a direction in which the inspection object is received, and a feed-out unit that moves the inspection object in a direction different from a moving direction of the traverser, and discharges the inspection object through the second opening. The imaging chamber includes an imaging unit that images the inspection object that is received from the feed-in preparation chamber. The traverser includes a mount on which the inspection object is mountable, and a shield that moves together with the mount, and prevents radioactive rays that enter through one of the first opening and the second opening and propagate in the moving direction of the traverser from reaching the other one of the first opening and the second opening. The imaging chamber allows imaging of an inspection object using radioactive rays, such as X-rays. The feed-in preparation chamber allows an inspection object to wait until the object is fed into the imaging chamber. The feed-out preparation chamber allows the inspection object that has undergone imaging to be discharged. An inspection apparatus that performs imaging using radioactive rays may have leakage of radioactive rays when an inspection object is fed into and out of the imaging chamber. The inspection apparatus according to the aspect of the present invention includes the feed-in preparation chamber and the feed-out preparation chamber to keep radioactive rays inside. Each of the feed-in preparation chamber and the feed-out preparation chamber receives the inspection object through its first opening, moves the object using the traverser, and then discharges the inspection object through its second opening. In other words, the feed-in preparation chamber has its first opening communicating with the outside, and its second opening communicating with the imaging chamber. The feed-out preparation chamber has its first opening communicating with the imaging chamber, and its second opening communicating with the outside. The traverser translates the inspection object in a direction different from the direction in which the inspection object is received and discharged through the openings. The traverser includes a shield, which is arranged to prevent radioactive rays that enter through one opening from reaching the other opening. The shield is positioned to prevent the first opening and the second opening from communicating with each other when the traverser is at any position, and moves together with the mount. This structure eliminates a special mechanism, such as a shutter, and allows the inspection object to be fed into and out while preventing the imaging chamber from communicating with the outside. The shield may include a first member and a second member. The first member and the second member may be positioned to define a closed space together with opposing inner walls of the feed-in preparation chamber or the feed-out preparation chamber while the traverser is moving. The shields are positioned to define the closed space together with the opposing inner walls. The compartment is thus independent and is like an airlock on the path for feeding the inspection object into and out of the compartment. In other words, this structure allows an inspection object to be fed in and out while preventing the first opening and the second opening from communicating with each other. In the inspection apparatus according to the above aspect of the present invention, the first opening and the second opening may be spatially separated by the closed space. Spatially separating the first opening and the second opening prevents radioactive rays from leaking outside the apparatus. The first member and the second member may be plates that are arranged in parallel with the mount sandwiched therebetween within a plane orthogonal to the moving direction of the traverser, and are slidable on the inner walls of the feed-in preparation chamber or the feed-out preparation chamber. The two plates, which are arranged in parallel with the mount sandwiched between them, can slide on the inner walls to prevent radioactive rays that enter from the imaging chamber both when the mount is communicating with the first opening and when it is communicating with the second opening. The shields sliding on the inner walls may not intend no gap between the shields and the inner walls. A small gap may be left between the inner walls and the shields to allow smooth movement of the shields. In the inspection apparatus according to the above aspect of the present invention, a shortest distance from the first opening to the second opening may be longer than a distance between the first member and the second member. This structure prevents the first opening and the second opening from communicating with each other, and prevents leakage of radioactive rays that enter from the imaging chamber in a reliable manner when the traverser is at any position. The inspection apparatus according to the above aspect of the present invention may include a member that limits a movable range of the traverser to prevent the traverser positioned at one of the first opening and the second opening from moving in a direction away from the other one of the first opening and the second opening. When the traverser is arranged between the first opening and the second opening, the shields prevent leakage of radioactive rays that enter from the imaging chamber. However, when the traverser moves outside this range, the first opening and the second opening can communicate with each other. To prevent this, a member that limits the movement of the traverser may be used. The feed-in unit included in the feed-in preparation chamber may receive a subsequent inspection object into the feed-in preparation chamber before the imaging unit completes imaging. The traverser included in the feed-in preparation chamber may move the subsequent inspection object to the second opening before the imaging unit completes imaging. In this manner, a subsequent inspection object is fed to a position immediately before the imaging chamber and waits while the imaging of the current inspection object is being performed. This shortens the time taken before starting the inspection, and improves the total inspection speed. An inspection apparatus according to a second aspect of the present invention includes a feed-in preparation chamber, an imaging chamber, and a feed-out preparation chamber. Each of the feed-in preparation chamber and the feed-out preparation chamber includes a feed-in unit that receives an inspection object through a first opening, a traverser that translates the received inspection object to a second opening in a direction different from a direction in which the inspection object is received, and a feed-out unit that moves the inspection object in a direction different from the direction of the traverser, and discharges the inspection object through the second opening. The imaging chamber includes an imaging unit that images the inspection object received from the feed-in preparation chamber. The traverser includes a mount on which the inspection object is mountable, and a first shield and a second shield that move together with the mount. The first shield and the second shield are positioned to define a closed space together with opposing inner walls of the feed-in preparation chamber or the feed-out preparation chamber to allow the closed space to spatially separate the first opening from the second opening while the traverser is moving. One or more aspects of the present invention are directed to an inspection apparatus including at least one of the above units. The above processes and units may be combined with one another unless any technical contradiction arises. The inspection apparatus that uses radioactive rays according to one or more embodiments of the present invention shortens the time for inspection and prevents leakage of radioactive rays. An X-ray inspection apparatus according to one or more embodiments of the present invention performs non-destructive inspection of an object using image information obtained from X-ray imaging of the object. The embodiments are particularly directed to the structure for feeding an inspection object into and out of the X-ray inspection apparatus, and its control. In the embodiments described below, a substrate inspection apparatus reconstructs three-dimensional (3D) data representing components mounted on a substrate with oblique X-ray computed tomography (CT), and determines whether, for example, the solder is defective or non-defective based on the 3D data. Apparatus Overview Referring to FIGS. 1 and 2, the structure of an X-ray inspection apparatus according to the present embodiment will now be described. FIG. 1 is a schematic cross-sectional view of an X-ray inspection apparatus 1 according to the present embodiment. FIG. 2 is a block diagram showing the components and the functions of the X-ray inspection apparatus 1. As shown in FIGS. 1 and 2, the X-ray inspection apparatus 1 includes a feed-in preparation unit 10, an imaging unit 20, and a feed-out preparation unit 30. FIG. 1 is a diagram schematically showing a path on which a substrate is moved for inspection. A structure for preventing leakage of X-rays will be described later with reference to FIG. 3. As shown in FIG. 1, the X-ray inspection apparatus 1 includes, in its body, the imaging unit 20 for imaging using X-rays. The feed-in preparation unit 10 for feeding a substrate K as an inspection object into the imaging unit 20 is arranged upstream (left in the figure) from the imaging unit 20. The feed-out preparation unit 30 for discharging the object is arranged downstream (right in the figure) from the imaging unit 20. The feed-in preparation unit 10 includes a feeding mechanism 111 for feeding the substrate received from an upstream process (e.g., a reflow process). The feeding mechanism 111 is movable upward and downward in the figure, and is connectable to a feeding mechanism 203, which is arranged in the imaging unit 20. The substrate K that is fed from the upstream process passes through the feed-in preparation unit 10 (feeding mechanism 111), and then is fed into the imaging unit 20 to undergo intended imaging and inspection. The substrate is then fed to a feeding mechanism 311, which is arranged in the feed-out preparation unit 30. The feeding mechanism 311 moves upward and downward in the figure, and feeds the substrate K through its exit to a downstream process. In this manner, the X-ray inspection apparatus 1 according to the present embodiment is installed on a production line (in-line) and is designed to automatically inspect substrates. The feed-in preparation unit 10 will now be described. The feed-in preparation unit 10 includes a box (hereafter, a feed-in preparation chamber 100) having an entrance through which the substrate K to be inspected is fed in, and an exit through which the substrate is fed to the imaging unit. The box is formed from a material that does not transmit X-rays. The box through which the substrate to be inspected is moved is referred to as the feed-in preparation chamber 100, and the mechanisms arranged in the feed-in preparation chamber 100 and their controller are collectively referred to as the feed-in preparation unit 10. The feed-in preparation unit 10 includes the feed-in preparation chamber 100, the feeding mechanism 111, a lift mechanism 112, and a controller 120. The feeding mechanism 111 moves an object mounted on it in the feeding direction (X-direction in the figure). Although the feeding mechanism 111 typically includes a linear actuator, a rail, and a belt conveyor, it may include other components. The substrate K fed from an upstream process is fed by the feeding mechanism 111 into the feed-in preparation chamber 100. The feeding mechanism 111 is movable using the lift mechanism 112 in a direction orthogonal to the feeding direction of the substrate (Z-direction in the figure). The lift mechanism 112 may be driven by, for example, a linear actuator, or may be driven using power transferred with a belt or a chain to transfer the substrate to the feeding mechanism 111. When the substrate K fed into the feed-in preparation chamber 100 reaches the exit, the feeding mechanism 111 feeds the substrate K into the imaging chamber 200, where the substrate K undergoes imaging and inspection. The controller 120 controls the operations of the feeding mechanism 111 and the lift mechanism 112. The controller 120 may be implemented by, for example, software executed on a general-purpose computer, or using dedicated hardware. The control performed by the controller 120 will be described in detail later. The imaging unit 20 will now be described. The imaging unit 20 includes a box (hereafter, an imaging chamber 200) having an entrance through which the substrate K to be inspected is fed from the feed-in preparation chamber 100, and an exit through which the substrate is fed to a feed-out preparation chamber 300. The box is formed from a material that does not transmit X-rays. The box, which defines a compartment for inspecting a substrate, is hereafter referred to as an imaging chamber 200. The components arranged in the imaging chamber 200 and their controller are collectively referred to as the imaging unit 20. The imaging unit 20 includes the imaging chamber 200, an X-ray generator 201, an X-ray detector 202, a feeding mechanism 203, a controller 204, and an inspection unit 205. The X-ray generator 201 emits X-rays. The apparatus uses X-ray computerized tomography (CT) imaging, and thus uses an X-ray source that emits an X-ray cone beam, which diverges conically. The X-ray detector 202 is a two-dimensional X-ray detector that detects X-rays that have been emitted from the X-ray source and have transmitted through the substrate under inspection. The X-ray detector 202 may be an image intensifier (I.I.) tube or a flat panel detector (FPD). Although the single X-ray detector is used in the present embodiment, a plurality of X-ray detectors may be used. The X-ray generator 201 and the X-ray detector 202 are movable in two-dimensional directions using stages (not shown). The feeding mechanism 203 is the same as the feeding mechanism 111, and will not be described. The controller 204 controls X-ray imaging of the inspection object by controlling the operations of the X-ray generator 201, the X-ray detector 202, and the feeding mechanism 203. In detail, the controller 204 controls reception of the substrate fed from the feed-in preparation chamber 100, discharge of the substrate that has undergone inspection, positioning of the X-ray generator 201 and the X-ray detector 202 using the stage (not shown), and X-ray emission performed by the X-ray generator 201. The inspection unit 205 inspects the substrate using X-ray images detected by the X-ray detector 202. In the present embodiment, imaging is performed multiple times (several times to several tens of times) while changing the relative positions of the X-ray generator, the X-ray detector, and the inspection object to obtain X-ray transmission images captured from different angles. Based on the obtained data, three-dimensional data for the substrate is reconstructed. This imaging method is called oblique X-ray CT, and is suitable for inspecting a thin object, such as an electronic substrate. The computation method used for oblique X-ray CT is known, and will not be described. The inspection unit 205 inspects the substrate based on the obtained three-dimensional data. The inspection unit 205 determines, for example, the positions of the components mounted on the substrate or the state of the solder (e.g., the solder wetting height or angle), and generates the results. The results may then be transmitted to a downstream process, or may be provided to the user of the apparatus through a display (not shown). The controller 204 and the inspection unit 205 may each include a typical general-purpose arithmetic unit called a central processing unit (CPU). The controller 204 and the inspection unit 205 may also include a memory, such as a random-access memory (RAM), or a read-only memory (ROM), a hard disk drive (HDD), or a solid-state drive (SSD). The controller 204 and the inspection unit 205 may also include an input device with which a user can input instructions, such as a keyboard, a button, a switch, or a pointing device. The controller 204 and the inspection unit 205 may also include an output device that provides the inspection results to the user in the form of an image or a sound with, for example, a display or a speaker. In other words, these functional units may be implemented using a typical computer system. Although the imaging unit 20 inspects the substrate using X-ray transmission images in the present embodiment, the imaging unit 20 may use a different mechanism for inspection. For example, the imaging unit 20 may further include a camera for capturing a visible light image, and may inspect the substrate using the visible light image. The feed-out preparation unit 30 will now be described. The feed-out preparation unit 30 includes a box (hereafter, the feed-out preparation chamber 300) having an entrance through which the substrate K that has undergone inspection is fed from the imaging chamber 200, and an exit through which the substrate is fed to a downstream process. The box is formed from a material that does not transmit X-rays. The box through which the inspected substrate is moved is hereafter referred to as the feed-out preparation chamber 300, and the components arranged in the feed-out preparation chamber 300 and their controller are collectively referred to as the feed-out preparation unit 30. The feed-out preparation unit 30 includes the feed-out preparation chamber 300, a feeding mechanism 311, a lift mechanism 312, and a controller 320. After the inspection, the substrate K is fed out of the imaging chamber 200, and is then moved to the feed-out preparation chamber 300 using the feeding mechanism 311. The feeding mechanism 311 and the lift mechanism 312 included in the feed-out preparation unit 30 are the same as the feeding mechanism 111 and the lift mechanism 112, and will not be described in detail. The feed-out preparation chamber 300 also has an entrance and an exit in the same manner as the feed-in preparation chamber 100, and feeds the substrate K to a downstream process. Structure for Preventing Leakage of X-rays Referring now to FIG. 3, an X-ray shielding structure included in each of the feed-in preparation chamber 100 and the feed-out preparation chamber 300 for preventing leakage of X-rays outside will now be described. FIG. 3 is a cross-sectional view showing the structure of the feed-in preparation chamber 100 and the feed-out preparation chamber 300 in more detail. Shield plates 113A and 113B are arranged in the XY plane to have the feeding mechanism 111 sandwiched between them. The shield plates 113A and 113B may be any typical members that prevent leakage of radioactive rays, and are typically formed from lead or tungsten. The shield plates 113A and 113B have their four sides in contact with the inner walls of the feed-in preparation chamber 100 to prevent leakage of radioactive rays. The feeding mechanism 111, the shield plate 113A, and the shield plate 113B are movable together. In the present embodiment, these members are collectively referred to as a traverser 110. The members included in the feed-out preparation chamber 300 are the same as the corresponding members described above except for the hundreds places in their reference numerals, and will not be described. FIG. 4 is a diagram describing the movable range of the traverser 110. As shown in FIG. 4, the movable range of the traverser 110 in Z-direction has its upper limit corresponding to the feeding mechanism 111 placed at the height of the entrance, and has its lower limit corresponding to the feeding mechanism 111 placed at the height of the exit. In other words, the shield plate 113A and/or the shield plate 113B is constantly located between the entrance and the exit. Although X-rays may enter the exit of the feed-in preparation chamber 100, which communicates with the imaging chamber 200, the entering X-rays are prevented by one or both of these shield plates from reaching the entrance of the feed-in preparation chamber 100. This structure spatially separates the imaging chamber 200 from outside the apparatus. The separation is maintained when the traverser 110 is at any position. To enable this, the distance d1 between the shield plate 113A and the shield plate 113B is to be smaller than the shortest distance d2 between the entrance and the exit. Although the feed-in preparation chamber 100 is described above, the substrate is fed from the imaging chamber 200 and discharged through the feed-out preparation chamber 300 in the same manner as in the feed-in preparation chamber 100. Procedure Referring now to FIGS. 5 to 7, the control associated with feeding-in, inspection, and feeding-out of the substrate will be described. FIG. 5 is a flowchart showing a control procedure for feeding-in of the substrate. The procedure shown in FIG. 5 is implemented by the controller 120 included in the feed-in preparation unit 10. In this example, the feed-in preparation unit 10, the imaging unit 20, and the feed-out preparation unit 30 each hold its status, and determine whether to perform feeding in accordance with the status of those units. The status is one of three statuses, namely the feed-in wait status, the operating status, or the feed-out wait status. In step S11, the traverser 110 is lifted using the lift mechanism 112, and then the status is changed to the feed-in wait status. This connects the feeding mechanism 111 to a feeding path in an upstream process. In step S12, the controller determines whether the upstream process is ready. In this step, the controller determines whether an upstream device is ready for feeding the substrate to be inspected into the inspection apparatus. When the determination result is affirmative, the processing advances to step S13, and the feeding mechanism 111 is activated to receive the substrate to be inspected. When the result is negative, the controller waits for a predetermined wait time, and then repeats the determination. When the substrate to be inspected is fed through the entrance, the status is changed to the operating status in step S14. In step S15, the traverser 110 is lowered, and the status is changed to the feed-out wait status. This connects the feeding mechanism 111 to the feeding mechanism 203. In step S16, the controller determines whether the imaging chamber 200 is ready. In this step, the controller 120 determines whether the controller 204 included in the imaging unit 20 is ready for receiving the substrate. In this step, the determination result is affirmative when the status of the imaging unit 20 is the feed-in wait status, and is negative when the status is either the operating status or the feed-out wait status. When the determination result is affirmative, the processing advances to step S17, and the feeding mechanism 111 is activated to feed the substrate to be inspected into the imaging chamber. When the determination result is negative, the controller waits for a predetermined wait time, and then repeats the determination. When the substrate to be inspected has been fed into the imaging chamber 200, the status is changed to the operating status in step S18. The processing then returns to step S11, and the traverser is moved to its initial position (lifted position). FIG. 6 is a flowchart showing a control procedure for inspection of the substrate. The procedure shown in FIG. 6 is implemented by the controller 204 included in the imaging unit 20. In step S21, the status is changed to the feed-in wait status. In step S22, the controller determines whether the substrate is ready for being fed from the feed-in preparation chamber 100. In this step, the determination result is affirmative when the status of the feed-in preparation unit 10 is the feed-out wait status, and is negative when the status is either the operating status or the feed-in wait status. When the determination result is affirmative, the processing advances to step S23, and the feeding mechanism 203 is activated to receive the substrate to be inspected. When the determination result is negative, the controller waits for a predetermined wait time, and then repeats the determination. When the substrate to be inspected is fed into the imaging chamber, the status is changed to the operating status in step S24. The substrate is inspected in step S24. More specifically, the substrate undergoes X-ray irradiation and imaging. The obtained images are transmitted to the inspection unit 205 to perform inspection. When the inspection is complete, the status is changed to the feed-out wait status in step S25. In the above example, the processing advances to step S25 after the inspection is complete. In some embodiments, the imaging and the inspection may be performed in parallel. More specifically, the substrate may be discharged immediately when the inspection is started by the inspection unit 205 after the X-ray imaging is complete. In step S26, the controller determines whether the feed-out preparation unit 30 is ready for receiving the substrate. In this step, the determination result is affirmative when the status of the feed-out preparation unit 30 is the feed-in wait status, and is negative when the status is either the operating status or the feed-out wait status. When the determination result is affirmative, the operation advances to step S27, and the feeding mechanism 203 is activated to discharge the substrate that has undergone inspection. When the determination result is negative, the controller waits for a predetermined wait time, and then repeats the determination. FIG. 7 is a flowchart showing a control procedure for feeding-out of the substrate. The procedure shown in FIG. 7 is implemented by the controller 320 included in the feed-out preparation unit 30. In step S31, the traverser 310 is lowered using the lift mechanism 312, and then the status is changed to the feed-in wait status. This connects the feeding mechanism 311 to the feeding mechanism 203. In step S32, the controller determines whether the substrate is ready for being fed from the imaging chamber 200. In this step, the determination result is affirmative when the status of the imaging unit 20 is the feed-out wait status, and is negative when the status is either the operating status or the feed-in wait status. When the determination result is affirmative, the operation advances to step S33, and the feeding mechanism 311 is activated to receive the substrate that has been inspected. When the determination result is negative, the controller waits for a predetermined wait time, and then repeats the determination. When the substrate that has been inspected is fed through the entrance, the status is changed to the operating status in step S34. In step S35, the traverser 310 is lifted, and the status is changed to the feed-out wait status. In step S36, the controller determines whether the downstream process is ready. In this step, the controller determines whether a device installed in the downstream process is ready for feeding the substrate from the inspection apparatus. When the determination result is affirmative, the processing advances to step S37, and the feeding mechanism 311 is activated to discharge the substrate that has undergone inspection. When the determination is negative, the controller waits for a predetermined wait time, and then repeats the determination. When the substrate has been discharged, the status is changed to the operating status in step S38. The processing advances to step S31, and the traverser is moved to its initial position (lowered position). As described above, the inspection apparatus according to the present embodiment prevents leakage of X-rays generated in the imaging chamber using the shields included in the traverser. This structure eliminates a mechanism that opens and closes the X-ray shields independently, and thus reduces the cost of the apparatus. This structure also enables the feed-in and feed-out operations to be performed during X-ray irradiation in the imaging chamber, and thus readily shortens the time taken for the inspection. Additionally, the feed-in preparation unit and the feed-out preparation unit operate independently of each other. This allows a subsequent substrate to be fed into the inspection chamber before the currently inspected substrate is completely discharged from the inspection apparatus. This shortens the interval of X-ray imaging operations, and thus shortens the total inspection time. The feeding mechanism 203 in the first embodiment extends across the imaging chamber 200 to allow a mounted substrate to be moved on the feeding mechanism 203. In the second embodiment, a feeding mechanism 203 is moved to move a substrate together. FIG. 8 is a schematic cross-sectional view of an X-ray inspection apparatus 1 according to the second embodiment. As shown in the figure, the feeding mechanism 203 in the present embodiment is movable in X-direction in the figure. In the second embodiment, the feeding mechanism 203 is moved to a position at which it can receive a substrate before the processing in step S21 is started. The feeding mechanism 203 is also moved to a position at which it can discharge the substrate before the processing in step S25 is started. After the completion of the processing in step S27, the status is temporarily changed to the operating status until the feeding mechanism 203 is moved to a position at which it can receive the substrate. This is another embodiment of the present invention. Modifications The embodiments disclosed herein should not be construed to be restrictive, but may be modified within the spirit and scope of the claimed invention. The technical features disclosed in different embodiments may be combined in other embodiments within the technical scope of the invention. For example, although the above embodiments are directed to the apparatuses for inspecting substrates, the present invention is applicable to X-ray non-destructive inspection for various other inspection objects, in addition to substrates. The present invention is also applicable to any other imaging method, in addition to the imaging method using oblique X-ray CT. Although the structure according to the embodiments of the present invention is suitable for an imaging method that uses a cone beam for effective shielding, it is also applicable to other imaging methods using a fan beam or a highly directional beam. Further, although the apparatuses according to the above embodiments have a single inspection line in the imaging chamber, the apparatuses may have two or more lines in the imaging chamber. For example, the apparatuses may include a plurality of inspection lines when a longer time is taken for X-ray imaging than for an operation in an upstream (downstream) process. In this case, the imaging chamber may have a plurality of entrances and a plurality of exits. For example, when the entrances (exits) are arranged in Z-direction, the traverser may be controlled to stop at an intended entrance (exit). When the entrances (exits) are arranged in Y-direction, the traverser may include an additional mechanism that shifts the substrate in Y-direction. The traverser may further include a plurality of feeding mechanisms arranged in parallel. The number of inspection lines may be determined to balance between the processing amount and the processing time. Further, although the inspection object is fed in X-direction and the traverser is moved in Z-direction in the above embodiments, the embodiments are not limited to this structure. For example, the traverser may be movable in the depth direction in the figure (Y-direction). This modification is suitable for inspecting a substrate that is thick in the vertical direction (Z-direction) and thin in the horizontal direction (Y-direction). In this case, a plurality of shield plates may be arranged in parallel in the depth direction in the figure. The direction in which the traverser moves and the positions at which the shield plates are arranged may be changed as appropriate for the design. Further, members may be added to prevent the traverser from moving outside its movable range. For example, as shown in FIG. 9A, movement of the traverser into an unintended area due to mispositioning may allow communication between the entrance and the exit, and may cause X-ray leakage. Cushions may be arranged as shown in FIG. 9B to limit the movable range of the traverser. This prevents the traverser from moving outside the intended movable range, and improves safety. Although the traverser in the above embodiments includes the whole plates that slide on the inner walls of the feed-in preparation chamber (feed-out preparation chamber) as the shield plates, the shield plates may not be whole plates, and also may not slide on the inner walls. For example, as shown in FIG. 10, a small gap may be left between the shield plates and the inner walls. The size of the gap may be determined in accordance with the permissible amount of X-ray leakage. In particular, shield plates with side walls shown in FIG. 10 are appropriate and can also serve as the cushions in FIGS. 9A and 9B. 10 feed-in preparation unit 20 imaging unit 30 feed-out preparation unit 100 feed-in preparation chamber 111 feeding mechanism 112 lift mechanism 120 controller 200 imaging chamber 201 X-ray generator 202 X-ray detector 203 feeding mechanism 204 controller 205 inspection unit 300 feed-out preparation chamber 311 feeding mechanism 312 lift mechanism 320 controller
	summary
	claims	1. Dental radiology apparatus comprising:a generator (18) provided with a window (18b) emitting X-radiation and a collimation device positioned in front of said window in order to collimate the radiation in a suitable manner using several forms of collimation slits,at least one sensor (20a, 20b) comprising a first image acquisition surface elongated along a Z-axis perpendicular to a plane P and being used in a first position of the apparatus to produce a panoramic image of a jaw placed between the generator and the first image acquisition surface, the panoramic image being produced from the X-radiation collimated by a first form of collimation slit (22a) elongated along the Z-axis and received by the first sensor image acquisition surface and by displacement of the generator and of said first surface along a given trajectory in the plane P combined with a rotation about an axis parallel to the Z-axis, the said at least one sensor comprising a second image acquisition surface used in cone beam tomographic mode, in a second position of the apparatus, to produce a three-dimensional model of only a part of the jaw from the X-radiation collimated by a second form of collimation slit (22b) and received by the second image acquisition surface and by displacement of the generator and of said second surface in rotation about an axis parallel to the Z-axis, the second form of collimation slit having dimensions matched to those of the second image acquisition surface, characterized in that the apparatus is able to occupy a third position of use and to this end comprises means of positioning, in front of the window emitting X-radiation, a third form of collimation slit (22c) elongated in a direction parallel to the plane P and arranged opposite a third image acquisition surface corresponding to a part of the second surface along the Z-axis in order to cooperate with the third image acquisition surface, the longitudinal dimension of the slit in the direction parallel to the plane P being matched to the dimension of the second image acquisition surface in this same direction. 2. Apparatus according to claim 1, characterized in that it comprises means of obtaining in cone beam tomographic mode a predetermined number of three-dimensional models each representing a different part of the jaw from an assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P. 3. Apparatus according to claim 2, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels, and the predetermined number of three-dimensional models depends in particular on the size of the array or the sub array of pixels of the third image acquisition surface. 4. Apparatus according to claim 1, characterized in that it comprises:means of positioning, in the plane P, about a fixed axis parallel to the Z-axis, the assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P;means of driving in rotation, about the fixed axis of rotation, the assembly comprising third surface and generator;means of acquiring several image signals of a part of a jaw illuminated by the radiation collimated by the third form of slit oriented parallel to the plane P for a plurality of angular positions occupied by the assembly comprising third surface and generator during the rotation movement. 5. Apparatus according to claim 4, characterized in that the positioning means are able to position the assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P successively about other fixed axes of rotation in order that, for each positioning about one of these other axes of rotation, the drive means and the acquisition means are able to cooperate with a view to acquiring image signals of another illuminated part of the jaw. 6. Apparatus according to claim 4, characterized in that it comprises means of obtaining a three-dimensional model of each illuminated part of a jaw from the set of acquired image signals. 7. Apparatus according to claim 6, characterized in that it comprises:means of reconstructing a three-dimensional model of a jaw from the three-dimensional models of the different parts of a jaw; andmeans of identifying, from the three-dimensional model reconstructed in this way, a trajectory which the assembly comprising first image acquisition surface and generator will have to follow during the subsequent production of a panoramic image of the jaw. 8. Apparatus according to claim 7, characterized in that the means of identifying a trajectory from the reconstructed three-dimensional model comprise means of thresholding or segmenting the data constituting this three-dimensional model. 9. Apparatus according to claim 4, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels, and the means of acquiring several image signals comprise means of reading the data captured by the array or the sub array of pixels, said reading means comprising means of grouping the pixels according to a predetermined number of pixels for the purpose of reading the pixels grouped in this way. 10. Apparatus according to claim 1, characterized in that the collimation device comprises three collimation slits of different forms which are each able to be positioned, on command, in front of the emission window in order to collimate the radiation in an appropriate manner. 11. Apparatus according to claim 1, characterized in that the collimation device comprises a mobile collimation slits support which is able to position, under the action of positioning means, a form of collimation slit in front of the window emitting X-radiation. 12. Apparatus according to claim 11, characterized in that the collimation slits support is able to pivot under the action of the positioning means. 13. Apparatus according to claim 1, characterized in that the collimation device comprises a collimation slit and means of adjusting the dimensions of the slit in order to give it at least some of the three forms of collimation slit used in the three respective positions of the apparatus. 14. Apparatus according to claim 13, characterized in that the adjustment means are means of adjusting the elongation of the slit in directions perpendicular to each other. 15. Apparatus according to claim 14, characterized in that the adjustment means are independent as regards the directions. 16. Apparatus according to claim 1, characterized in that the collimation slit is delimited by four edges (58, 60, 62, 64) and the adjustment means are able to displace each of the edges independently of one another. 17. Apparatus according to claim 1, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels. 18. Apparatus according to claim 1, characterized in that the first and second image acquisition surfaces form part of a first and a second sensor respectively. 19. Apparatus according to claim 18, characterized in that it comprises a mobile unit (20) comprising the two sensors and which is able to position, on command, opposite the generator, each of the two sensors in order that it receives the X-radiation collimated by a collimation slit of appropriate form. 20. Apparatus according to claim 1, characterized in that the first, second and third image acquisition surfaces form part of a single sensor. 21. Method for producing a panoramic image of a patient's jaw from a dental radiology apparatus comprising:a generator (18) provided with a window (18b) emitting X-radiation and a collimation device positioned in front of said window in order to collimate the radiation in a suitable manner using several forms of collimation slits,at least one sensor (20a, 20b) comprising a first image acquisition surface elongated along a Z-axis perpendicular to a plane P and being used in a first position of the apparatus to produce a panoramic image of a jaw placed between the generator and the first image acquisition surface, the panoramic image being produced from the X-radiation collimated by a first form of collimation slit (22a) elongated along the Z-axis and received by the first sensor image acquisition surface and by displacement of the generator and of said first surface along a given trajectory in the plane P combined with a rotation about an axis parallel to the Z-axis, the said at least one sensor comprising a second image acquisition surface used in cone beam tomographic mode, in a second position of the apparatus, to produce a three-dimensional model of only a part of the jaw from the X-radiation collimated by a second form of collimation slit (22b) and received by the second image acquisition surface and by displacement of the generator and of said second surface in rotation about an axis parallel to the Z-axis, the second form of collimation slit having dimensions matched to those of the second image acquisition surface, characterized in that the method comprises, in a third position of use of the apparatus in cone beam tomographic mode, the following preliminary steps in order to obtain a trajectory which will be travelled in the plane P, by the assembly comprising generator and first image acquisition surface, in the first position of use of the apparatus for the production of a panoramic image of the jaw:positioning (S1 ), in front of the window emitting X-radiation, of a third form of collimation slit (22c) elongated in a direction parallel to the plane P and the longitudinal dimension of which in this direction is matched to the dimension of the second image acquisition surface in this same direction,positioning (S2), opposite the third form of collimation slit oriented in this way, of a third image acquisition surface corresponding to a part of the second surface along the Z-axis, for the purpose of cooperation of the third form of slit and the third surface. 22. Method according to claim 21, characterized in that it comprises, following the positioning steps, a step of obtaining in cone beam tomographic mode a predetermined number of solid images each representing a different part of a jaw from the assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P. 23. Method according to claim 22, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels, and the predetermined number of three-dimensional models depends in particular on the size of the array or the sub array of pixels of the third image acquisition surface. 24. Method according to claim 21, characterized in that it comprises the following steps:a) positioning (S4) in the plane P, about a fixed axis parallel to the Z-axis, of the assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P;b) driving in rotation (S5) of the assembly comprising third image acquisition surface and generator about the fixed axis of rotation;c) acquisition (S6) of several image signals of a part of a jaw illuminated by the radiation collimated by the third form of slit oriented parallel to the plane P for a plurality of angular positions occupied by the assembly comprising third image acquisition surface and generator during the rotation movement. 25. Method according to claim 24, characterized in that it comprises the following steps:positioning of the assembly comprising third image acquisition surface and generator provided with the third form of collimation slit elongated parallel to the plane P about another fixed axis parallel to the Z-axis andrealization of steps b) and c) for the acquisition of the image signals of another illuminated part of the jaw. 26. Method according to claim 24, characterized in that it comprises a step of obtaining, from the set of acquired image signals, a three-dimensional model of each illuminated part of the jaw. 27. Method according to claim 26, characterized in that it comprises the following steps:reconstruction (S12) of a three-dimensional model of a jaw from the three-dimensional models of different parts of a jaw;identification (S14), from the three-dimensional model reconstructed in this way, of a trajectory which the assembly comprising first image acquisition surface and generator will have to follow during the subsequent production of a panoramic image of the jaw. 28. Method according to claim 27, characterized in that the identification of a trajectory from the reconstructed three-dimensional model comprises a step (S13) of thresholding or segmenting the data constituting this three-dimensional model. 29. Method according to claim 24, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels, and the acquisition of several image signals comprises a step of reading the data captured by the array or the sub array of pixels which comprises a grouping of the pixels according to a predetermined number of pixels for the purpose of reading the pixels grouped in this way. 30. Method according to claim 21, characterized in that it comprises the following steps:positioning (S16), in front of the window emitting X-radiation, of the first form of collimation slit elongated along the Z-axis,positioning (S17) of the first image acquisition surface opposite the first form of collimation slit oriented in this way,control of the displacement of the assembly formed of the generator provided with the first form of collimation slit and the first image acquisition surface arranged parallel to the axis (Z) along the trajectory previously obtained combined with a rotation movement about an axis parallel to the axis (Z),acquisition of a panoramic image of the jaw during this controlled displacement combined with a shift of the pixels of the first image acquisition surface. 31. Method according to claim 21, characterized in that the collimation device comprises three collimation slits of different forms and the positioning of each of them in front of the emission window is carried out by displacement from a home position placed outside the radiation that has come from the generator. 32. Method according to claim 21, characterized in that the collimation device comprises a collimation slit and the positioning, in front of the emission window, of a different form of collimation slit is carried out by adjusting the dimensions of the slit. 33. Method according to claim 32, characterized in that the adjustment more particularly comprises the adjustment of the elongation of the slit in directions perpendicular to each other. 34. Method according to claim 21, characterized in that each first, second and third image acquisition surface of the said at least one sensor is an array of pixels or a sub array of pixels. 35. Method according to claim 21, characterized in that the first and second image acquisition surfaces form part of a first and a second sensor respectively. 36. Method according to claim 35, characterized in that the positioning of a sensor opposite the generator is carried out by displacement of said sensor. 37. Method according to claim 21, characterized in that the first, second and third image acquisition surfaces form part of a single sensor.
039473228	claims	1. A nuclear reactor pressure vessel support arrangement comprising a vertical substantially cylindrical pressure vessel having top and bottom portions, a substantially circular downwardly facing surface connected to said bottom portion, and a substantially circular upwardly facing surface on which said downwardly facing surface rests and which is fixed against displacement; wherein the improvement comprises said surfaces being substantially frusto-conical shapes with said upwardly facing surface upright and said downwardly facing surface inverted and slidable on said upwardly facing surface. 2. The arrangement of claim 1 in which said surfaces are concentric with the axis of said vessel and a foundation is below said vessel and a cylindrical base has a bottom portion supported by said foundation and a top portion on which said upwardly facing surface is formed. 3. The arrangement of claim 2 in which said base is formed by circumferentially interspaced cylindrical segments. 4. The arrangement of claim 1 in which said vessel's said top portion has means for holding it against upward displacement. 5. The arrangement of claim 1 in which said vessel has an upper portion and a horizontal coolant pipe has one end which is connected with said upper portion, and a steam generator, said pipe having another end and which is connected with said steam generator, and means for vertically supporting said steam generator for horizontal movement of the generator in the direction of said pipe. 6. The arrangement of claim 5 in which a concrete biological shield is positioned between said pressure vessel and said steam generator and has a horizontal hole through which said coolant pipe passes. 7. The arrangement of claim 6 in which said pipe has means for restraining it from excessive longitudinal displacement in the event it breaks and which normally permits said displacement to a degree preventing stressing of the pipe longitudinally by motion resulting from radial thermally induced motion of said vessel.
052689433	summary	BACKGROUND OF THE INVENTION The invention relates to a nuclear reactor system which includes means for injecting additional coolant into the reactor coolant circuit, and in particular to a system wherein the residual heat removal apparatus which thermally couples the coolant circuit system to heat exchangers for removing residual heat is coupleable into fluid communication between an in-containment refueling water supply tank and the reactor coolant circuit as a means to inject additional coolant. The invention is applicable to reactor systems having passive safety features, with depressurization of the reactor coolant circuit to facilitate injection of additional coolant water. A nuclear reactor such as a pressurized water reactor circulates coolant at high pressure through a coolant circuit traversing a reactor vessel containing nuclear fuel for heating the coolant, a steam generator operable to extract energy from the coolant. A residual heat removal system is typically provided to remove decay heat during shutdowns. In the event of a loss of coolant, means are provided for adding additional coolant. A coolant loss may involve only a small quantity, whereby additional coolant can be injected from a relatively small high pressure makeup water supply, without depressurizing the reactor coolant circuit. If a major loss of coolant occurs, it is necessary to add coolant from a low pressure supply containing a large quantity of water. Whereas it is difficult using pumps to overcome the substantial pressure of the reactor coolant circuit (e.g., 2,250 psi or 150 bar), the reactor coolant circuit is depressurized so that coolant water can be added from an in-containment refueling water storage tank at ambient pressure in the containment shell. The Westinghouse AP600 reactor system, of which the present invention is a part, uses a staged pressure reduction apparatus for depressurizing the coolant circuit. A series of valves couple the reactor outlet (also known as the "hot leg" of the coolant circuit) to the inside of the containment shell. The valves operate at successively lower pressures. When initially commencing depressurization, the coolant circuit and the containment structure are coupled by depressurization valves through one or more smaller conduits along a flow path with not-insubstantial back pressure. As the pressure in the coolant circuit drops, additional conduits are opened by further depressurization valves in stages, each stage opening a larger and/or more direct flow path between the coolant circuit and the containment shell. The initial stages couple a pressurizer tank which is connected by a conduit to the coolant circuit hot leg, to spargers in an in-containment refueling water supply tank. The spargers comprise conduits leading to small jet orifices submerged in the tank, thus providing back pressure and allowing water to condense from steam emitted by the spargers into the tank. The successive depressurization stages have progressively larger conduit inner diameters. A final stage has a large conduit that couples the hot leg directly into the containment shell, for example, at a loop compartment through which the hot leg of the reactor circuit passes. This arrangement reduces the pressure in the coolant circuit expeditiously, substantially to atmospheric pressure, without sudden hydraulic loading of the respective reactor conduits. When the pressure is sufficiently low, water is added to the coolant circuit by gravity flow from the in-containment refueling water supply tank. Automatic depressurization in the AP600 reactor is a passive safeguard which ensures that the reactor core is cooled even in the case of a major loss of coolant accident such as a large breach in the reactor coolant circuit. Inasmuch as the in-containment refueling water storage tank drains by gravity, no pumps are required. Draining the water into the bottom of the containment building where the reactor vessel is located, develops a fluid pressure head of water in the containment sufficient to force water into the depressurized coolant circuit without relying on active elements such as pumps. Once the coolant circuit is at atmospheric pressure and the containment is flooded, water continues to be forced into the reactor vessel, where boiling of the water cools the nuclear fuel. Water in steam escaping from the reactor coolant circuit is condensed on the inside walls of the containment shell, and drained back to be injected again into the reactor coolant circuit. The foregoing arrangement has been shown to be effective in the scenario of a severe loss of coolant accident. However, there is a potential that if the automatic depressurization system is activated in less dire circumstances, the containment may be flooded needlessly. Depressurization followed by flooding of the reactor containment requires shutdown of the reactor and a significant cleanup effort. There is a need for a system which is sufficiently responsive to react appropriately to a major accident, but which also minimizes damage and expense if the situation can be remedied appropriately by addition of coolant in excess of the high pressure makeup supply, or perhaps by an orderly shutdown procedure for effecting repairs. This system must be arranged to complement the passive safety system, without retarding or otherwise adversely affecting the ability of the passive safety system to respond to a real accident. SUMMARY OF THE INVENTION It is an object of the invention to couple the normal residual heat removal system of a pressurized water nuclear reactor to a passive safeguard system which depressurizes the reactor coolant circuit when adding coolant, in order to preclude disruptive final depressurization steps which may be unnecessary under the circumstances. It is another object of the invention to provide a non-safety grade coolant additive apparatus associated with the residual heat removal system, for preventing flooding of the reactor containment building in the event of inadvertent or unnecessary actuation of a passive core cooling system using automatic depressurization. It is a further object of the invention to employ the pumping power of one or more residual heat removal pumps, for functions other than residual heat removal attendant to shutdown, including charging of the reactor coolant system and cooling the in-containment refueling storage tank water. These and other objects are accomplished by a pressurized water nuclear reactor that normally uses a residual heat removal system for cooling the reactor coolant circuit when the reactor is not operational. According to the invention, the same residual heat removal system is manually coupleable for charging the reactor coolant circuit from an in-containment refueling water supply during staged depressurization. Depressurization stages can be triggered by falling levels of coolant. In a final stage of depressurization, the containment building would be flooded for emergency cooling using the refueling water storage tank, i.e., at atmospheric pressure. Whereas coolant can be added via the residual heat removal system when depressurization is due to inadvertence or a small leak, the residual heat removal system prevents depressurization from proceeding to the final, containment flood stage when such action is not necessary and a more orderly shutdown can be accomplished to effect repairs. Nevertheless, operation of the passive cooling system is not impaired when fast depressurization and passive cooling are called for by an emergency. A makeup water storage tank is coupled to the reactor coolant circuit, holding coolant at the operational pressure of the reactor. A depressurization system which can be triggered by falling levels of makeup water opens successive conduits leading to spargers in the refueling water storage tank, thus reducing pressure, ultimately to atmospheric pressure. The spargers prevent steam and radiation from being discharged into the containment during the opening of the first three stages of depressurization. At reduced pressure the coolant circuit can be charged by gravity feed from the refueling water storage tank, and/or the reactor can be cooled by flooding the containment building from the refueling water storage tank as a passive cooling means. The residual heat removal system is manually activated for pumping water from the refueling water storage tank, where the water is at ambient pressure, into the still pressurized coolant circuit as the coolant circuit reaches a depressurized prior to flooding of the containment. The staged depressurization system vents the coolant circuit to the containment, reducing the supply of coolant. However, coolant added by the residual heat removal system makes up the lost coolant and thus prevent reaching the final depressurization stage. The residual heat removal system can also be coupled in a loop with the refueling water supply tank, for an auxiliary heat removal path.
	summary
048266507	description	Referring to FIG. 1, a reactor vessel V is shown shut down and open having its head H, dryer D and steam separator S all removed. Working personnel P1 and P2 are shown standing on a work platform overlying the top guide G some 50 feet deep within the reactor. Worker P1 through rod R1 manipulates frame F1 for the interrogation of the reactor top guide for vertical cracking; similarly worker P2 through rod R2 manipulates frame F2 for the interrogation of the top guide G for horizontal cracking. Typically, such an inspection will occur when portions of the top guide have been exposed to radiation in the order of 2.times.10.sup.21 neutrons/cm.sup.2. It is at this dosage level that the stainless steel of the top guide assembly G can begin to have that phenomenon known as irradiation assisted stress crack corrosion (IASCC). Referring to FIG. 2, a plan view of the top guide G is illustrated within the reactor vessel V. Top guide G is shown to be a lattice-like structure of intersecting bars. These bars typically overlie a core plate C (see FIG. 1) and define discrete cells 20. As is well known in the prior art, the cells 20 each brace the tops of four fuel assemblies. The cells 20 of the top guide G hold the fuel assemblies at their upward end remote from the core plate C which supports the weight of the fuel assemblies. The function of the top guide G is at least two fold in nature. First, the top guide G maintains the fuel assemblies in their upright position. Secondly, the top guide G maintains the fuel assemblies with their sides parallel to one another and spaced apart from one another. This enables among other things, the control rods to penetrate the cruciformed shaped interstices between four fuel assemblies. Such a configuration of four fuel assemblies A maintained by the top guide assembly is shown at cell 20' in FIG. 2. In order for a test of this invention to be conducted, it is preferred that each cell 20 have the fuel assemblies A removed. This prevents protrusion of the fuel channels of the fuel assembly from interfering with the test procedures herein set forth. The area of fuel assembly removal is shown in heavy solid lines. It will be understood that fuel assemblies on both sides of the portion of the top guide G designated by the heavy lines are removed. Having set forth the ambient within which testing occurs, the tests will now be described. First, a test frame F1 will be illustrated with respect to FIG. 3A and 3B. Its placement in testing a portion of the top guide G will be set forth with respect to FIG. 5. Thereafter and with reference to FIG. 4, a test frame F2 will be set forth. Its placement in testing top guide G will also be set forth with respect to FIG. 5. Referring to FIG. 3A, frame F1 includes a nose piece 40 having the shape of a finder and a main body 50 having the approximate section of a fuel channel of a typical fuel assembly. A carriage 60 is shown mounted for vertical excursion along two respective open and therefore exposed sides 51, 52 of frame F1. The carriage rides on three bars 53, 54, and 55. The carriage is propelled by a ball screw (imbedded in the carriage 60 and therefore not shown) following a rotating threaded shaft 57. Rotation of shaft 57 is monitored at shaft encoder 58 and caused by motor 59 at the top of the assembly. Conventional rotation of motor 59 and tracking of rotation at shaft encoder 58 enables precise positioning of the carriage 60 to be known. Carriage 60 includes a carriage face 61 parallel to open side 51 and a second carriage face 62 parallel to open side 52. Faces 51, 52 each confront a bar at the corner of a cell in a top guide. Referring to FIG. 3B, carriage 60 is illustrated in plan with its two faces 61, 62. Each of the faces 61, 62 have paired transducers. These transducers are 63 and 65 on face 61 and 64 and 66 on face 62. Transducer 63 sends a signal at 70.degree. way from face 61 towards the corner defined by the intersection of the faces 61, 62. Transducer 65 adjacent the corner of faces 61, 62 sends an acoustical signal horizontally at 70.degree. away from the corner defined by faces 61, 62. The acoustical signals of transducers 64, 66 on face 62 are correspondingly angularly incident towards and away from the swept cell corner. The purpose of these opposed angularly incident signals may readily be understood. Specifically, the transducers 63, 65 will pass immediately over the bar that they are interrogating. In such passage, the acoustical signals must be given an angle of incidence wherein penetration of the bar with the acoustical signal and detection of the returned acoustical signal is assured. By the specific orientation herein disclosed, thorough checking of a bar at the corner of a discrete cell in guide G is assured; one transducer interrogates to the corner, the remaining transducer interrogates away from the corner; as can be seen, vertical sweep across the entire width of the bar by the transducers thoroughly interrogates the full width of the bars forming the corner with horizontal ultrasound to detect vertical cracking. Turning to FIG. 5, positioning of the bar to the top guide G can be understood. Specifically, paired plates 71, 72 are positioned on the exterior of test frame F1. These plates define an inwardly extending angle, which angle braces frame F1 to a corner of the discrete cell illustrated in FIG. 3. Once the frame F1 is so positioned, excursion and acoustical interrogation in a horizontal plane of the illustrated transducers 63, 65 and 64, 66 occurs. It can be understood that all of the bars defining a discrete cell can be tested. This can occur by positioning frame F1 in each of the respective corners of a defined cell. With repeat of this procedure, acoustical sweeping of the bars of the top guide with horizontally interrogating acoustical signals for the detection of vertical cracks can occur. Referring to FIG. 4, frame F2 is illustrated. It includes longitudinal sides 101, 102 and ends 104, 105. These sides and ends form a rigid frame structure connected at a yoke 106 to rod R2. Paired rods 114, 116 form points of support for the excursion of a carriage 110. Carriage 110 has mounted there below an ultrasound transducer 112. Carriage 110 is driven by a threaded shaft 118 at a ball screw imbedded within the carriage 110 (not shown). Motor 119 causes shaft 118 to rotate. A shaft encoder 120 determines the precise position of the carriage 110. Feet 131, 132 rest upon a bar parallel to section 104 of the rotor. A forward foot from bar 105 (obscured in the view here shown) preferably rests on the bar tested at a portion within the next cell on top guide G. Turning to FIG. 5, placement of the frame F2 is illustrated. Referring back to FIG. 4 it will be understood that transducer 112 undergoes excursion the length of the frame. The single transducer 112 interrogates with vertical ultrasound waves a bar for horizontal cracking. Thus the fixtures set forth in Figs. 3A and 3B and FIG. 4 are capable of remotely interrogating the lattice of top guide G for horizontal and vertical cracking.
	abstract	Corner of each square pipe is molded into a terrace shape having steps. When a basket is constructed by these square pipes, steps of adjoining square pipes are assembled together face to face. Fuel rod aggregates are housed inside the square pipes and in a cells formed between the square pipes. Since the adjoining square pipes are assembled in a staggered arrangement, boundaries of the cells are defined by the walls of the square pipes itself.
	claims	1. A nuclear reactor internals component having a sensor insert for monitoring one or more environmental conditions surrounding the sensor insert's location within a reactor internals, the nuclear reactor internals component comprising;a head;an elongated shank extending from the head to a distal end, the shank having a hollow compartment extending at least partially between the distal end and the head and a cross-sectional profile of the elongated shank being sized to fit into an opening in the reactor internals;an end plug for sealing off the hollow compartment at the distal end, affixed to the distal end;one or more self-contained, passive environmental sensors secured within the hollow compartment in the sensor insert; andan anchor for fixing the elongated shank in the opening in the reactor internals, the anchor including a locking mechanism that fixes an orientation of the shank within the opening in the reactor internals, wherein the locking mechanism is a lockbar that extends through an opening in the head and through a groove on a surface off the shank and partially into a groove in a surface of a wall in the opening in the reactor internals, in which the shank is to be inserted. 2. The nuclear reactor internals component of claim 1 wherein the one or more self-contained, passive environmental sensors comprise a plurality of environmental sensors respectively configured to monitor different environmental parameters. 3. The nuclear reactor internals component of claim 1 wherein the one or more environmental sensors comprise material samples, dosimetry or maximum temperature monitors. 4. The nuclear reactor internals component of claim 1 wherein the sensor insert includes one or more coded markings that identify the location of the sensor insert within the reactor internals. 5. The nuclear reactor internals component of claim 4 wherein the coded markings identify the orientation of the sensor insert within the reactor internals. 6. The nuclear reactor internals component of claim 1 wherein the anchor comprises one of either a male or female thread extending over at least a portion of the shank, that is sized to mate with another of a male or female thread on the opening in the reactor internals. 7. The nuclear reactor internals component of claim 1 wherein the lockbar is held in position within the opening in the head by a spring clip wedged against a portion of the head. 8. The nuclear reactor internals component of claim 7 wherein the spring clip is wedged in a counter-bore in a surface of the head. 9. The nuclear reactor internals component of claim 8 wherein the spring clip is a circular spring clip. 10. The nuclear reactor internals component of claim 1 wherein the shank has an axial dimension along an elongated dimension of the shank and the hollow compartment is partitioned into separate axial compartments in the sensor insert in which the one or more self-contained, passive environmental sensors are respectively supported. 11. The nuclear reactor internals component of claim 1 comprising a plurality of self-contained passive environmental sensors secured within the hollow compartment, wherein the hollow compartment is partitioned into separate circumferential compartments in the sensor insert in which the plurality of self-contained, passive environmental sensors are respectively supported. 12. The nuclear reactor internals component of claim 1 comprising a plurality of self-contained passive environmental sensors secured within the sensor insert within the hollow compartment, wherein the plurality of self-contained, passive environmental sensors are housed within the sensor insert comprising a partitioned sheath within which the plurality of self-contained, passive environmental sensors are separated, with the sheath sized to slide into and out of the hollow compartment. 13. The nuclear reactor internals component of claim 12 wherein the sheath has a positioning feature that fixes the orientation of the sheath relative to the hollow compartment. 14. The nuclear reactor internals component of claim 12 wherein the sheath has a coded marking that identifies the sensor insert in which it resided. 15. The nuclear reactor internals component of claim 12 wherein the sheath includes a gripping feature proximate the distal end to ease movement of the sheath out of the hollow compartment. 16. The nuclear reactor internals component of claim 1 wherein the one or more environmental sensors includes a neutron activation wire that is enclosed within a stainless steel tubing with cadmium shielding. 17. The nuclear reactor internals component of claim 1 wherein the shank comprises Stainless Steel 347 and/or titanium. 18. The nuclear reactor internals component of claim 1 wherein the distal end of the shank has a larger circumference than a portion of the shank that extends from the head. 19. The nuclear reactor internals component of claim 1 wherein the head has a flared circumferential extension configured to mechanically engage with a circumferentially-machined groove or slot in the opening in the reactor internals. 20. The nuclear reactor internals component of claim 1 wherein the reactor internals component is configured to resemble a bolt used elsewhere in the reactor internals. 21. The nuclear reactor internals component of claim 1 wherein the reactor internals component is configured to function as a thimble plug. 22. The nuclear reactor internals component of claim 1 wherein the reactor internals component has an external profile substantially equal to a profile of another reactor internals component.
	description	This application is a continuation of U.S. patent application Ser. No. 10/367,355, filed on Feb. 14, 2003, now U.S. Pat. No. 7,167,811 entitled METHODS AND APPARATUS FOR DATA ANALYSIS. The invention relates to data analysis. Semiconductor companies test components to ensure that the components operate properly. The test data not only determine whether the components function properly, but also may indicate deficiencies in the manufacturing process. Accordingly, many semiconductor companies may analyze the collected data from several different components to identify problems and correct them. For example, the company may gather test data for multiple chips on each wafer among several different lots. This data may be analyzed to identify common deficiencies or patterns of defects or identify parts that may exhibit quality and performance issues and to identify or classify user-defined “good parts”. Steps may then be taken to correct the problems. Testing is typically performed before device packaging (at wafer level) as well as upon completion of assembly (final test). Gathering and analyzing test data is expensive and time consuming. Automatic testers apply signals to the components and read the corresponding output signals. The output signals may be analyzed to determine whether the component is operating properly. Each tester generates a large volume of data. For example, each tester may perform 200 tests on a single component, and each of those tests may be repeated 10 times. Consequently, a test of a single component may yield 2000 results. Because each tester is testing 100 or more components an hour and several testers may be connected to the same server, an enormous amount of data must be stored. Further, to process the data, the server typically stores the test data in a database to facilitate the manipulation and analysis of the data. Storage in a conventional database, however, requires further storage capacity as well as time to organize and store the data. The analysis of the gathered data is also difficult. The volume of the data may demand significant processing power and time. As a result, the data is not usually analyzed at product run time, but is instead typically analyzed between test runs or in other batches. To alleviate some of these burdens, some companies only sample the data from the testers and discard the rest. Analyzing less than all of the data, however, ensures that the resulting analysis cannot be fully complete and accurate. As a result, sampling degrades the complete understanding of the test results. In addition, even when the full set of test data generated by the tester is retained, the sheer volume of the test data presents difficulties in analyzing the data and generating meaningful results. The data may contain significant information about the devices, the testing process, and the manufacturing process that may be used to improve production, reliability, and testing. In view of the amount of data, however, isolating and presenting the information to the user or another system is challenging. Furthermore, acquiring the test data presents a complex and painstaking process. A test engineer prepares a test program to instruct the tester to generate the input signals to the component and receive the output signals. The program tends to be very complex to ensure full and proper operation of the component. Consequently, the test program for a moderately complex integrated circuit involves a large number of tests and results. Preparing the program demands extensive design and modification to arrive at a satisfactory solution, and optimization of the program, for example to remove redundant tests or otherwise minimize test time, requires additional exertion. A method and apparatus for testing semiconductors according to various aspects of the present invention comprises a test system comprising composite data analysis element configured to analyze data from more than one dataset. The test system may be configured to provide the data in an output report. The composite data analysis element suitably performs a spatial analysis to identify patterns and irregularities in the composite data set. The composite data analysis element may also operate in conjunction with a various other analysis systems, such as a cluster detection system and an exclusion system, to refine the composite data analysis. The composite may also be merged into other data. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the connections and steps performed by some of the elements in the figures may be exaggerated or omitted relative to other elements to help to improve understanding of embodiments of the present invention. The present invention may be described in terms of functional block components and various process steps. Such functional blocks and steps may be realized by any number of hardware or software components configured to perform the specified functions. For example, the present invention may employ various testers, processors, storage systems, processes, and integrated circuit components, e.g., statistical engines, memory elements, signal processing elements, logic elements, programs, and the like, which may carry out a variety of functions under the control of one or more testers, microprocessors, or other control devices. In addition, the present invention may be practiced in conjunction with any number of test environments, and each system described is merely one exemplary application for the invention. Further, the present invention may employ any number of conventional techniques for data analysis, component interfacing, data processing, component handling, and the like. Referring to FIG. 1, a method and apparatus according to various aspects of the present invention operates in conjunction with a test system 100 having a tester 102, such as automatic test equipment (ATE) for testing semiconductors. In the present embodiment, the test system 100 comprises a tester 102 and a computer system 108. The test system 100 may be configured for testing any components 106, such as semiconductor devices on a wafer, circuit boards, packaged devices, or other electrical or optical systems. In the present embodiment, the components 106 comprise multiple integrated circuit dies formed on a wafer or packaged integrated circuits or devices. The tester 102 suitably comprises any test equipment that tests components 106 and generates output data relating to the testing. The tester 102 may comprise a conventional automatic tester, such as a Teradyne tester, and suitably operates in conjunction with other equipment for facilitating the testing. The tester 102 may be selected and configured according to the particular components 106 to be tested and/or any other appropriate criteria. The tester 102 may operate in conjunction with the computer system 108 to, for example, program the tester 102, load and/or execute the test program, collect data, provide instructions to the tester 102, implement a statistical engine, control tester parameters, and the like. In the present embodiment, the computer system 108 receives tester data from the tester 102 and performs various data analysis functions independently of the tester 102. The computer system 108 also implements a statistical engine to analyze data from the tester 102. The computer system 108 may comprise a separate computer, such as a personal computer or workstation, connected to or networked with the tester 102 to exchange signals with the tester 102. In an alternative embodiment, the computer system 108 may be omitted from or integrated into other components of the test system 100 and various functions may be performed by other components, such as the tester 102. The computer system 108 includes a processor 110 and a memory 112. The processor 110 comprises any suitable processor, such as a conventional Intel, Motorola, or Advanced Micro Devices processor, operating in conjunction with any suitable operating system, such as Windows 98, Windows NT, Unix, or Linux. Similarly, the memory 112 may comprise any appropriate memory accessible to the processor 110, such as a random access memory (RAM) or other suitable storage system, for storing data. In particular, the memory 112 of the present system includes a fast access memory for storing and receiving information and is suitably configured with sufficient capacity to facilitate the operation of the computer 108. In the present embodiment, the memory 112 includes capacity for storing output results received from the tester 102 and facilitating analysis of the output test data. The memory 112 is configured for fast storage and retrieval of test data for analysis. The memory 112 is suitably configured to store the elements of a dynamic datalog, suitably comprising a set of information selected by the test system 100 and/or the operator according to selected criteria and analysis based on the test results. For example, the memory 112 suitably stores a component identifier for each component 106, such as x-y coordinates corresponding to a position of the component 106 on a wafer map for the tested wafer. Each x-y coordinate in the memory 112 may be associated with a particular component 106 at the corresponding x-y coordinate on the wafer map. Each component identifier has one or more fields, and each field corresponds, for example, to a particular test performed on the component 106 at the corresponding x-y position on the wafer, a statistic related to the corresponding component 106, or other relevant data. The memory 112 may be configured to include any data identified by the user as desired according to any criteria or rules. The computer 108 of the present embodiment also suitably has access to a storage system, such as another memory (or a portion of the memory 112), a hard drive array, an optical storage system, or other suitable storage system. The storage system may be local, like a hard drive dedicated to the computer 108 or the tester 102, or may be remote, such as a hard drive array associated with a server to which the test system 100 is connected. The storage system may store programs and/or data used by the computer 108 or other components of the test system 100. In the present embodiment, the storage system comprises a database 114 available via a remote server 116 comprising, for example, a main production server for a manufacturing facility. The database 114 stores tester information, such as tester data files, master data files for operating the test system 100 and its components, test programs, downloadable instructions for the test system 100, and the like. In addition, the storage system may comprise complete tester data files, such as historical tester data files retained for analysis. The test system 100 may include additional equipment to facilitate testing of the components 106. For example, the present test system 100 includes a device interface 104, like a conventional device interface board and/or a device handler or prober, to handle the components 106 and provide an interface between the components 106 and the tester 102. The test system 100 may include or be connected to other components, equipment, software, and the like to facilitate testing of the components 106 according to the particular configuration, application, environment of the test system 100, or other relevant factors. For example, in the present embodiment, the test system 100 is connected to an appropriate communication medium, such as a local area network, intranet, or global network like the internet, to transmit information to other systems, such as the remote server 116. The test system 100 may include one or more testers 102 and one or more computers 108. For example, one computer 108 may be connected to an appropriate number of, such as up to twenty or more, testers 102 according to various factors, such as the system's throughput and the configuration of the computer 108. Further, the computer 108 may be separate from the tester 102, or may be integrated into the tester 102, for example utilizing one or more processors, memories, clock circuits, and the like of the tester 102 itself. In addition, various functions may be performed by different computers. For example, a first computer may perform various pre-analysis tasks, several computers may then receive the data and perform data analysis, and another set of computers may prepare the dynamic datalogs and/or other output reports. A test system 100 according to various aspects of the present invention tests the components 106 and provides enhanced analysis and test results. For example, the supplemental analysis may identify incorrect, questionable, or unusual results, repetitive tests, and/or tests with a relatively high probability of failure. The test system 100 may also analyze multiple sets of data, such as data taken from multiple wafers and/or lots of wafers, to generate composite data based on multiple datasets. The operator, such as the product engineer, test engineer, manufacturing engineer, device engineer, or other personnel using the test data, may then use the results to verify and/or improve the test system 100 and or the fabrication system and classify the components 106. The test system 100 according to various aspects of the present invention executes an enhanced test process for testing the components 106 and collecting and analyzing test data. The test system 100 suitably operates in conjunction with a software application executed by the computer 108. Referring to FIG. 2, the software application of the present embodiment includes multiple elements for implementing the enhanced test process, including a configuration element 202, a supplementary data analysis element 206, and an output element 208. The test system 100 may also include a composite analysis element 214 for analyzing data from more than one dataset. Each element 202, 206, 208, 214 suitably comprises a software module operating on the computer 108 to perform various tasks. Generally, the configuration element 202 prepares test system 100 for testing and analysis. In the supplementary data analysis element 206, output test data from the tester 102 is analyzed to generate supplementary test data, suitably at run time and automatically. The supplementary test data is then transmitted to the operator or another system, such as the composite analysis element, or the output element 208. As shown in FIG. 2, the data may also be substantially concurrently provided to the composite analysis element 214 and the output element 208. The configuration element 202 configures the test system 100 for testing the components 106 and analyzing the test data. The test system 100 suitably uses a predetermined set of initial parameters and, if desired, information from the operator to configure the test system 100. The test system 100 is suitably initially configured with predetermined or default parameters to minimize operator attendance to the test system 100. Adjustments may be made to the configuration by the operator, if desired, for example via the computer 108. Referring to FIG. 3, an exemplary configuration process 300 performed by the configuration element 202 begins with an initialization procedure (step 302) to set the computer 108 in an initial state. The configuration element 202 then obtains application configuration information (step 304), for example from the database 114, for the computer 108 and the tester 102. For example, the configuration element 202 may access a master configuration file for the enhanced test process and/or a tool configuration file relating to the tester 102. The master configuration file may contain data relating to the proper configuration for the computer 108 and other components of the test system 100 to execute the enhanced test process. Similarly, the tool configuration file suitably includes data relating to the tester 102 configuration, such as connection, directory, IP address, tester node identification, manufacturer, flags, prober identification, or any other pertinent information for the tester 102. The configuration element 202 may then configure the test system 100 according to the data contained in the master configuration file and/or the tool configuration file (step 306). In addition, the configuration element 202 may use the configuration data to retrieve further relevant information from the database 114, such as the tester's 102 identifier (step 308) for associating data like logistics instances for tester data with the tester 102. The test system 100 information also suitably includes one or more default parameters that may be accepted, declined, or adjusted by the operator. For example, the test system 100 information may include global statistical process control (SPC) rules and goals that are submitted to the operator upon installation, configuration, power-up, or other appropriate time for approval and/or modification. The test system 100 information may also include default wafer maps or other files that are suitably configured for each product, wafer, component 106, or other item that may affect or be affected by the test system 100. The configuration algorithms, parameters, and any other criteria may be stored in a recipe file for easy access, correlation to specific products and/or tests, and for traceability. When the initial configuration process is complete, the test system 100 commences a test run, for example in conjunction with a conventional series of tests, in accordance with a test program. The tester 102 suitably executes the test program to apply signals to connections on the components 106 and read output test data from the components 106. The tester 102 may perform multiple tests on each component 106 on a wafer, and each test may be repeated several times on the same component 106. Test data from the tester 102 is stored for quick access and supplemental analysis as the test data is acquired. The data may also be stored in a long-term memory for subsequent analysis and use. Each test generates at least one result for at least one of the components. Referring to FIG. 9, an exemplary set of test results for a single test of multiple components comprises a first set of test results having statistically similar values and a second set of test results characterized by values that stray from the first set. Each test result may be compared to an upper test limit and a lower test limit. If a particular result for a component exceeds either limit, the component may be classified as a “bad part”. Some of the test results in the second set that stray from the first set may exceed the control limits, while others do not. For the present purposes, those test results that stray from the first set but do not exceed the control limits or otherwise fail to be detected are referred to as “outliers”. The outliers in the test results may be identified and analyzed for any appropriate purpose, such as to identify potentially unreliable components. The outliers may also be used to identify a various potential problems and/or improvements in the test and manufacturing processes. As the tester 102 generates the test results, the output test data for each component, test, and repetition is stored by the tester 102 in a tester data file. The output test data received from each component 106 is analyzed by the tester 102 to classify the performance of the component 106, for example by comparison to the upper and lower test limits, and the results of the classification are also stored in the tester data file. The tester data file may include additional information as well, such as logistics data and test program identification data. The tester data file is then provided to the computer 108 in an output file, such as a standard tester data format (STDF) file, and stored in memory. The tester data file may also be stored in the storage system for longer term storage for later analysis, such as by the composite analysis element 214. When the computer 108 receives the tester data file, the supplementary data analysis element 206 analyzes the data to provide enhanced output results. The supplementary data analysis element 206 may provide any appropriate analysis of the tester data to achieve any suitable objective. For example, the supplementary data analysis element 206 may implement a statistical engine for analyzing the output test data at run time and identifying data and characteristics of the data of interest to the operator. The data and characteristics identified may be stored, while data that is not identified may be otherwise disposed of, such as discarded. The supplementary data analysis element 206 may, for example, calculate statistical figures according to the data and a set of statistical configuration data. The statistical configuration data may call for any suitable type of analysis according to the needs of the test system 100 and/or the operator, such as statistical process control, outlier identification and classification, signature analyses, and data correlation. Further, the supplementary data analysis element 206 suitably performs the analysis at run time, i.e., within a matter of seconds or minutes following generation of the test data. The supplementary data analysis element 206 may also perform the analysis automatically with minimal intervention from the operator and/or test engineer. In the present test system 100, after the computer 108 receives and stores the tester data file, the supplementary data analysis element 206 performs various preliminary tasks to prepare the computer 108 for analysis of the output test data and facilitate generation of supplementary data and preparation of an output report. Referring now to FIGS. 4A-C, in the present embodiment, the supplementary data analysis element 206 initially copies the tester data file to a tool input directory corresponding to the relevant tester 102 (step 402). The supplementary data analysis element 206 also retrieves configuration data to prepare the computer 108 for supplementary analysis of the output test data. The configuration data suitably includes a set of logistics data that may be retrieved from the tester data file (step 404). The supplementary data analysis element 206 also creates a logistics reference (step 406). The logistics reference may include tester 102 information, such as the tester 102 information derived from the tool configuration file. In addition, the logistics reference is assigned an identification. The configuration data may also include an identifier for the test program that generated the output test data. The test program may be identified in any suitable manner, such as looking it up in the database 114 (step 408), by association with the tester 102 identification, or reading it from the master configuration file. If no test program identification can be established (step 410), a test program identification may be created and associated with the tester identification (step 412). The configuration data further identifies the wafers in the test run to be processed by the supplementary data analysis element 206, if fewer than all of the wafers. In the present embodiment, the supplementary data analysis element 206 accesses a file indicating which wafers are to be analyzed (step 414). If no indication is provided, the computer 108 suitably defaults to analyzing all of the wafers in the test run. If the wafer for the current test data file is to be analyzed (step 416), the supplementary data analysis element 206 proceeds with performing the supplementary data analysis on the test data file for the wafer. Otherwise, the supplementary data analysis element 206 waits for or accesses the next test data file (step 418). The supplementary data analysis element 206 may establish one or more section groups to be analyzed for the various wafers to be tested (step 420). To identify the appropriate section group to apply to the output test data, the supplementary data analysis element 206 suitably identifies an appropriate section group definition, for example according to the test program and/or the tester identification. Each section group includes one or more section arrays, and each section array includes one or more sections of the same section types. Section types comprise various sorts of component 106 groups positioned in predetermined areas of the wafer. For example, referring to FIG. 5, a section type may include a row 502, a column 504, a stepper field 506, a circular band 508, a radial zone 510, a quadrant 512, or any other desired grouping of components. Different section types may be used according to the configuration of the components, such as order of components processed, sections of a tube, or the like. Such groups of components 106 are analyzed together to identify, for example, common defects or characteristics that may be associated with the group. For example, if a particular portion of the wafer does not conduct heat like other portions of the wafer, the test data for a particular group of components 106 may reflect common characteristics or defects associated with the uneven heating of the wafer. Upon identifying the section group for the current tester data file, the supplemental data analysis element 206 retrieves any further relevant configuration data, such as control limits and enable flags for the test program and/or tester 102 (step 422). In particular, the supplemental data analysis element 206 suitably retrieves a set of desired statistics or calculations associated with each section array in the section group (step 423). Desired statistics and calculations may be designated in any manner, such as by the operator or retrieved from a file. Further, the supplemental data analysis element 206 may also identify one or more signature analysis algorithms (step 424) for each relevant section type or other appropriate variation relating to the wafer and retrieve the signature algorithms from the database 114 as well. All of the configuration data may be provided by default or automatically accessed by the configuration element 202 or the supplemental data analysis element 206. Further, the configuration element 202 and the supplemental data analysis element 206 of the present embodiment suitably allow the operator to change the configuration data according to the operator's wishes or the test system 100 requirements. When the configuration data have been selected, the configuration data may be associated with relevant criteria and stored for future use as default configuration data. For example, if the operator selects a certain section group for a particular kind of components 106, the computer 108 may automatically use the same section group for all such components 106 unless instructed otherwise by the operator. The supplemental data analysis element 206 also provides for configuration and storage of the tester data file and additional data. The supplemental data analysis element 206 suitably allocates memory (step 426), such as a portion of the memory 112, for the data to be stored. The allocation suitably provides memory for all of the data to be stored by the supplemental data analysis element 206, including output test data from the tester data file, statistical data generated by the supplemental data analysis element 206, control parameters, and the like. The amount of memory allocated may be calculated according to, for example, the number of tests performed on the components 106, the number of section group arrays, the control limits, statistical calculations to be performed by the supplementary data analysis element 206, and the like. When all of the configuration data for performing the supplementary analysis are ready and upon receipt of the output test data, the supplementary data analysis element 206 loads the relevant test data into memory (step 428) and performs the supplementary analysis on the output test data. The supplementary data analysis element 206 may perform any number and types of data analyses according to the components 106, configuration of the test system 100, desires of the operator, or other relevant criteria. The supplemental data analysis element 206 may be configured to analyze the sections for selected characteristics identifying potentially defective components 106 and patterns, trends, or other characteristics in the output test data that may indicate manufacturing concerns or flaws. The present supplementary data analysis element 206, for example, smoothes the output test data, calculates and analyzes various statistics based on the output test data, and identifies data and/or components 106 corresponding to various criteria. The present supplementary data analysis element 206 may also classify and correlate the output test data to provide information to the operator and/or test engineer relating to the components 106 and the test system 100. For example, the present supplementary data analysis element 206 may perform output data correlations, for example to identify potentially related or redundant tests, and outlier incidence analyses to identify tests having frequent outliers. The supplementary data analysis element 206 may include a smoothing system to initially process the tester data to smooth the data and assist in the identification of outliers (step 429). The smoothing system may also identify significant changes in the data, trends, and the like, which may be provided to the operator by the output element 208. The smoothing system is suitably implemented, for example, as a program operating on the computer system 108. The smoothing system suitably comprises multiple phases for smoothing the data according to various criteria. The first phase may include a basic smoothing process. The supplemental phases conditionally provide for enhanced tracking and/or additional smoothing of the test data. The smoothing system suitably operates by initially adjusting an initial value of a selected tester datum according to a first smoothing technique, and supplementarily adjusting the value according to a second smoothing technique if at least one of the initial value and the initially adjusted value meets a threshold. The first smoothing technique tends to smooth the data. The second smoothing technique also tends to smooth the data and/or improve tracking of the data, but in a different manner from the first smoothing technique. Further, the threshold may comprise any suitable criteria for determining whether to apply supplemental smoothing. The smoothing system suitably compares a plurality of preceding adjusted data to a plurality of preceding raw data to generate a comparison result, and applies a second smoothing technique to the selected datum to adjust the value of the selected datum according to whether the comparison result meets a first threshold. Further, the smoothing system suitably calculates a predicted value of the selected datum, and may apply a third smoothing technique to the selected datum to adjust the value of the selected datum according to whether the predicted value meets a second threshold. Referring to FIG. 8, a first smoothed test data point is suitably set equal to a first raw test data point (step 802) and the smoothing system proceeds to the next raw test data point (step 804). Before performing smoothing operations, the smoothing system initially determines whether smoothing is appropriate for the data point and, if so, performs a basic smoothing operation on the data. Any criteria may be applied to determine whether smoothing is appropriate, such as according to the number of data points received, the deviation of the data point values from a selected value, or comparison of each data point value to a threshold. In the present embodiment, the smoothing system performs a threshold comparison. The threshold comparison determines whether data smoothing is appropriate. If so, the initial smoothing process is suitably configured to proceed to an initial smoothing of the data. More particularly, in the present embodiment, the process starts with an initial raw data point R0, which is also designated as the first smoothed data point S0. As additional data points are received and analyzed, a difference between each raw data point (Rn) and a preceding smoothed data point (Sn-1) is calculated and compared to a threshold (T1) (step 806). If the difference between the raw data point Rn and the preceding smoothed data point Sn-1 exceeds the threshold T1, it is assumed that the exceeded threshold corresponds to a significant departure from the smoothed data and indicates a shift in the data. Accordingly, the occurrence of the threshold crossing may be noted and the current smoothed data point Sn is set equal to the raw data point Rn (step 808). No smoothing is performed, and the process proceeds to the next raw data point. If the difference between the raw data point and the preceding smoothed data point does not exceed the threshold T1, the process calculates a current smoothed data point Sn in conjunction with an initial smoothing process (step 810). The initial smoothing process provides a basic smoothing of the data. For example, in the present embodiment, the basic smoothing process comprises a conventional exponential smoothing process, such as according to the following equation:Sn=(Rn−Sn-1)M1+Sn-1 where M1 is a selected smoothing coefficient, such as 0.2 or 0.3. The initial smoothing process suitably uses a relatively low coefficient M1 to provide a significant amount of smoothing for the data. The initial smoothing process and coefficients may be selected according to any criteria and configured in any manner, however, according to the application of the smoothing system, the data processed, requirements and capabilities of the smoothing system, and/or any other criteria. For example, the initial smoothing process may employ random, random walk, moving average, simple exponential, linear exponential, seasonal exponential, exponential weighted moving average, or any other appropriate type of smoothing to initially smooth the data. The data may be further analyzed for and/or subjected to smoothing. Supplementary smoothing may be performed on the data to enhance the smoothing of the data and/or improve the tracking of the smoothed data to the raw data. Multiple phases of supplementary smoothing may also be considered and, if appropriate, applied. The various phases may be independent, interdependent, or complementary. In addition, the data may be analyzed to determine whether supplementary smoothing is appropriate. In the present embodiment, the data is analyzed to determine whether to perform one or more additional phases of smoothing. The data is analyzed according to any appropriate criteria to determine whether supplemental smoothing may be applied (step 812). For example, the smoothing system identify trends in the data, such as by comparing a plurality of adjusted data points and raw data points for preceding data and generating a comparison result according to whether substantially all of the preceding adjusted data share a common relationship (such as less than, greater than, or equal to) with substantially all of the corresponding raw data. The smoothing system of the present embodiment compares a selected number P2 of raw data points to an equal number of smoothed data points. If the values of all of the P2 raw data points exceed (or are equal to) the corresponding smoothed data points, or if all raw data points are less than (or equal to) the corresponding smoothed data points, then the smoothing system may determine that the data is exhibiting a trend and should be tracked more closely. Accordingly, the occurrence may be noted and the smoothing applied to the data may be changed by applying supplementary smoothing. If, on the other hand, neither of these criteria is satisfied, then the current smoothed data point remains as originally calculated and the relevant supplementary data smoothing is not applied. In the present embodiment, the criterion for comparing the smoothed data to the raw data is selected to identify a trend in the data behind which the smoothed data may be lagging. Accordingly, the number of points P2 may be selected according to the desired sensitivity of the system to changing trends in the raw data. The supplementary smoothing changes the effect of the overall smoothing according to the data analysis. Any appropriate supplementary smoothing may be applied to the data to more effectively smooth the data or track a trend in the data. For example, in the present embodiment, if the data analysis indicates a trend in the data that should be tracked more closely, then the supplementary smoothing may be applied to reduce the degree of smoothing initially applied so that the smoothed data more closely tracks the raw data (step 814). In the present embodiment, the degree of smoothing is reduced by recalculating the value for the current smoothed data point using a reduced degree of smoothing. Any suitable smoothing system may be used to more effectively track the data or otherwise respond to the results of the data analysis. In the present embodiment, another conventional exponential smoothing process is applied to the data using a higher coefficient M2:Sn=(Rn−Sn-1)M2+Sn-1 The coefficients M1 and M2 may be selected according to the desired sensitivity of the system, both in the absence (M1) and the presence (M2) of trends in the raw data. In various applications, for example, the value of M1 may be higher than the value of M2. The supplementary data smoothing may include additional phases as well. The additional phases of data smoothing may similarly analyze the data in some manner to determine whether additional data smoothing should be applied. Any number of phases and types of data smoothing may be applied or considered according to the data analysis. For example, in the present embodiment, the data may be analyzed and potentially smoothed for noise control, such as using a predictive process based on the slope, or trend, of the smoothed data. The smoothing system computes a slope (step 816) based on a selected number P3 of smoothed data points preceding the current data point according to any appropriate process, such as line regression, N-points centered, or the like. In the present embodiment, the data smoothing system uses a “least squares fit through line” process to establish a slope of the preceding P3 smoothed data points. The smoothing system predicts a value of the current smoothed data point according to the calculated slope. The system then compares the difference between the previously calculated value for the current smoothed data point (Sn) to the predicted value for the current smoothed data point to a range number (R3) (step 818). If the difference is greater than the range R3, then the occurrence may be noted and the current smoothed data point is not adjusted. If the difference is within the range R3, then the current smoothed data point is set equal to the difference between the calculated current smoothed data point (Sn) and the predicted value for the current smoothed data point (Sn-pred) multiplied by a third multiplier M3 and added to the original value of the current smoothed data point (step 820). The equation:Sn=(Sn-pred−Sn)M3+Sn Thus, the current smoothed data point is set according to a modified difference between the original smoothed data point and the predicted smoothed data point, but reduced by a certain amount (when M3 is less than 1). Applying the predictive smoothing tends to reduce point-to-point noise sensitivity during relatively flat (or otherwise non-trending) portions of the signal. The limited application of the predictive smoothing process to the smoothed data points ensures that the calculated average based on the slope does not affect the smoothed data when significant changes are occurring in the raw data, i.e., when the raw data signal is not relatively flat. After smoothing the data, the supplementary data analysis element 206 may proceed with further analysis of the tester data. For example, the supplementary data analysis element 206 may conduct statistical process control (SPC) calculations and analyses on the output test data. More particularly, referring again to FIGS. 4A-C, the supplemental data analysis element 206 may calculate and store desired statistics for a particular component, test, and/or section (step 430). The statistics may comprise any statistics useful to the operator or the test system 100, such as SPC figures that may include averages, standard deviations, minima, maxima, sums, counts, Cp, Cpk, or any other appropriate statistics. The supplementary data analysis element 206 also suitably performs a signature analysis to dynamically and automatically identify trends and anomalies in the data, for example according to section, based on a combination of test results for that section and/or other data, such as historical data (step 442). The signature analysis identifies signatures and applies a weighting system, suitably configured by the operator, based on any suitable data, such as the test data or identification of defects. The signature analysis may cumulatively identify trends and anomalies that may correspond to problem areas or other characteristics of the wafer or the fabrication process. Signature analysis may be conducted for any desired signatures, such as noise peaks, waveform variations, mode shifts, and noise. In the present embodiment, the computer 108 suitably performs the signature analysis on the output test data for each desired test in each desired section. In the present embodiment, a signature analysis process may be performed in conjunction with the smoothing process. As the smoothing process analyzes the tester data, results of the analysis indicating a trend or anomaly in the data are stored as being indicative of a change in the data or an outlier that may be of significance to the operator and/or test engineer. For example, if a trend is indicated by a comparison of sets of data in the smoothing process, the occurrence of the trend may be noted and stored. Similarly, if a data point exceeds the threshold T1 in the data smoothing process, the occurrence may be noted and stored for later analysis and/or inclusion in the output report. For example, referring to FIGS. 6A-B, a signature analysis process 600 may initially calculate a count (step 602) for a particular set of test data and control limits corresponding to a particular section and test. The signature analysis process then applies an appropriate signature analysis algorithm to the data points (step 604). The signature analysis is performed for each desired signature algorithm, and then to each test and each section to be analyzed. Errors identified by the signature analysis, trend results, and signature results are also stored (step 606). The process is repeated for each signature algorithm (step 608), test (step 610), and section (step 612). Upon completion, the supplementary data analysis element 206 records the errors (step 614), trend results (step 616), signature results (step 618), and any other desired data in the storage system. Upon identification of each relevant data point, such as outliers and other data of importance identified by the supplementary analysis, each relevant data point may be associated with a value identifying the relevant characteristics (step 444). For example, each relevant components or data point may be associated with a series of values, suitably expressed as a hexadecimal figure, corresponding to the results of the supplementary analysis relating to the data point. Each value may operate as a flag or other designator of a particular characteristic. For example, if a particular data point has failed a particular test completely, a first flag in the corresponding hexadecimal value may be set. If a particular data point is the beginning of a trend in the data, another flag may be set. Another value in the hexadecimal figure may include information relating to the trend, such as the duration of the trend in the data. The supplementary data analysis element 206 may also be configured to classify and correlate the data (step 446). For example, the supplementary data analysis element 206 may utilize the information in the hexadecimal figures associated with the data points to identify the failures, outliers, trends, and other features of the data. The supplementary data analysis element 206 also suitably applies conventional correlation techniques to the data, for example to identify potentially redundant or related tests. The computer 108 may perform additional analysis functions upon the generated statistics and the output test data, such as automatically identifying and classifying outliers (step 432). Analyzing each relevant datum according to the selected algorithm suitably identifies the outliers. If a particular algorithm is inappropriate for a set of data, the supplementary data analysis element 206 may be configured to automatically abort the analysis and select a different algorithm. The supplementary data analysis element 206 may operate in any suitable manner to designate outliers, such as by comparison to selected values and/or according to treatment of the data in the data smoothing process. For example, an outlier identification element according to various aspects of the present invention initially automatically calibrates its sensitivity to outliers based on selected statistical relationships for each relevant datum (step 434). Some of these statistical relationships are then compared to a threshold or other reference point, such as the data mode, mean, or median, or combinations thereof, to define relative outlier threshold limits. In the present embodiment, the statistical relationships are scaled, for example by one, two, three, and six standard deviations of the data, to define the different outlier amplitudes (step 436). The output test data may then be compared to the outlier threshold limits to identify and classify the output test data as outliers (step 438). The supplementary data analysis element 206 stores the resulting statistics and outliers in memory and identifiers, such as the x-y wafer map coordinates, associated with any such statistics and outliers (step 440). Selected statistics, outliers, and/or failures may also trigger notification events, such as sending an electronic message to an operator, triggering a light tower, stopping the tester 102, or notifying a server. In the present embodiment, the supplementary data analysis element 206 includes a scaling element 210 and an outlier classification element 212. The scaling element 210 is configured to dynamically scale selected coefficients and other values according to the output test data. The outlier classification element 212 is configured to identify and/or classify the various outliers in the data according to selected algorithms. More particularly, the scaling element of the present embodiment suitably uses various statistical relationships for dynamically scaling outlier sensitivity and smoothing coefficients for noise filtering sensitivity. The scaling coefficients are suitably calculated by the scaling element and used to modify selected outlier sensitivity values and smoothing coefficients. Any appropriate criteria, such as suitable statistical relationships, may be used for scaling. For example, a sample statistical relationship for outlier sensitivity scaling is defined as:(√{square root over (1+Natural LogCpk2)}) Another sample statistical relationship for outlier sensitivity and smoothing coefficient scaling is defined as:(√{square root over (1+Natural LogCpk2)})Cpm Another sample statistical relationship for outlier sensitivity and smoothing coefficient scaling is defined as: ( σ * Cpk ) ( Max - Min ) , where ⁢ ⁢ σ = datum ⁢ ⁢ Standard ⁢ ⁢ Deviation A sample statistical relationship used in multiple algorithms for smoothing coefficient scaling is: σ μ * 10 ,where σ=datum Standard Deviation and μ=datum Mean Another sample statistical relationship used in multiple algorithms for smoothing coefficient scaling is: σ 2 μ 2 * 10 ,where σ=datum Standard Deviation and μ=datum Mean The outlier classification element is suitably configured to identify and/or classify components 106, output test data, and analysis results according to any suitable algorithm the outliers in the output test data. The outlier classification element may also identify and classify selected outliers and components 106 according to the test output test results and the information generated by the supplementary analysis element 206. For example, the outlier classification element is suitably configured to classify the components 106 into critical/marginal/good part categories, for example in conjunction with user-defined criteria; user-defined good/bad spatial patterns recognition; classification of pertinent data for tester data compression; test setup in-situ sensitivity qualifications and analyses; tester yield leveling analyses; dynamic wafer map and/or test strip mapping for part dispositions and dynamic retest; or test program optimization analyses. The outlier classification element may classify data in accordance with conventional SPC control rules, such as Western Electric rules or Nelson rules, to characterize the data. The outlier classification element suitably classifies the data using a selected set of classification limit calculation methods. Any appropriate classification methods may be used to characterize the data according to the needs of the operator. The present outlier classification element, for example, classifies outliers by comparing the output test data to selected thresholds, such as values corresponding to one, two, three, and six statistically scaled standard deviations from a threshold, such as the data mean, mode, and/or median. The identification of outliers in this manner tends to normalize any identified outliers for any test regardless of datum amplitude and relative noise. The outlier classification element analyzes and correlates the normalized outliers and/or the raw data points based on user-defined rules. Sample user-selectable methods for the purpose of part and pattern classification based on identified outliers are as follows: Cumulative Amplitude, Cumulative Count Method: Count LIMIT = μ OverallOutlierCount + ( 3 * ( σ OverallOutlierCount 2 ) ( Max OverallOutlierCount - Min OverallOutlierCount ) ) NormalizedOutlierAmplitude LIMIT = μ Overall ⁢ ⁢ Normalized ⁢ ⁢ Outlier ⁢ ⁢ Amplitude + ( 3 * ( σ Overall ⁢ ⁢ Normalized ⁢ ⁢ Outlier ⁢ ⁢ Amplitude 2 ) ( Max Overall ⁢ ⁢ Normalized ⁢ ⁢ Outlier ⁢ ⁢ Amplitude - Min Overall ⁢ ⁢ Normalized ⁢ ⁢ Outlier ⁢ ⁢ Amplitude ) ) Classification Rules:PartCRITICAL=True,If└(PartCumlative Outlier Count>CountLIMIT)AND(PartCumlative Normalized Outlier Amplitude>NormalizedOutlierAmplitudeLIMIT)┘PartMARGINAL:HighAmplitude=True,If└(PartCumlative Normalized Outlier Amplitude>NormalizedOutlierAmplitudeLIMIT)┘PartMARGINAL:HighCount=True,If(PartCumlativeOutlierCount>CountLIMIT) Cumulative Amplitude Squared, Cumulative Count Squared Method: Count LIMIT 2 = μ OverallOutlierCount 2 + ( 3 * ( σ OverallOutlierCount 2 2 ) ( Max OverallOutlierCount 2 - Min OverallOutlierCount 2 ) ) Normalized ⁢ ⁢ OutlierAmplitude LIMIT 2 = μ OverallNormalizedOutlierAmplitude 2 + ( 3 * ( σ Overall ⁢ ⁢ NormalizedOutlier ⁢ ⁢ Amplitude 2 2 ) ( Max OverallNormalizedOutlierAmplitude 2 - Min OverallNormalizedOutlierAmplitude 2 ) ) Classification Rules:PartCRITICAL=True,If└(PartCumlativeOutlierCount2>CountLIMIT2)AND(PartCumlativeNormalizedOutlierAmplitude2>Normalized OutlierAmplitudeLIMIT2)┘PartMARGINAL:HighAmplitude=True,If└(PartCumlativeNormalizedOutlierAmplitude2>Normalized OutlierAmplitudeLIMIT2)┘PartMARGINAL:HighCount=True,If└(PartCumlative Outlier Count2>CountLIMIT2)┘ N-points Method: The actual numbers and logic rules used in the following examples can be customized by the end user per scenario (test program, test node, tester, prober, handler, test setup, etc.). σ in these examples=σ relative to datum mean, mode, and/or median based on datum standard deviation scaled by key statistical relationships.PartCRITICAL=True,If[((PartCOUNT:6σ+PartCOUNT:3σ)≧2)OR((PartCOUNT:2σ+PartCOUNT:1σ)≧6)]PartCRITICAL=True,If[((PartCOUNT:6σ+PartCOUNT:3σ)≧1)AND((PartCOUNT:2σ+PartCOUNT:1σ)≧3)]PartMARGINAL=True,If[((PartCOUNT:6σ+PartCOUNT:3σ+PartCOUNT:2σ+PartCOUNT:1σ)≧3)]PartNOISY=True,If[((PartCOUNT:6σ+PartCOUNT:3σ+PartCOUNT:2σ+PartCOUNT:1σ)≧1)] The supplementary data analysis element 206 may be configured to perform additional analysis of the output test data and the information generated by the supplementary data analysis element 206. For example, the supplementary data analysis element 206 may identify tests having high incidences of failure or outliers, such as by comparing the total or average number of failures, outliers, or outliers in a particular classification to one or more threshold values. The supplementary data analysis element 206 may also be configured to correlate data from different tests to identify similar or dissimilar trends, for example by comparing cumulative counts, outliers, and/or correlating outliers between wafers or other data sets. The supplementary data analysis element 206 may also analyze and correlate data from different tests to identify and classify potential critical and/or marginal and/or good parts on the wafer. The supplementary data analysis element 206 may also analyze and correlate data from different tests to identify user-defined good part patterns and/or bad part patterns on a series of wafers for the purposes of dynamic test time reduction. The supplementary data analysis element 206 is also suitably configured to analyze and correlate data from different tests to identify user-defined pertinent raw data for the purposes of dynamically compressing the test data into memory. The supplementary data analysis element may also analyze and correlate statistical anomalies and test data results for test node in-situ setup qualification and sensitivity analysis. Further, the supplementary data analysis element may contribute to test node yield leveling analysis, for example by identifying whether a particular test node may be improperly calibrated or otherwise producing inappropriate results. The supplementary data analysis element may moreover analyze and correlate the data for the purposes of test program optimization including, but not limited to, automatic identification of redundant tests using correlated results and outlier analysis and providing additional data for use in analysis. The supplementary data analysis element is also suitably configured to identify critical tests, for example by identifying regularly failed or almost failed tests, tests that are almost never-fail, and/or tests exhibiting a very low Cpk. The supplementary data analysis may also provide identification of test sampling candidates, such as tests that are rarely or never failed or in which outliers are never detected. The supplementary data analysis element may also provide identification of the best order test sequence based on correlation techniques, such as conventional correlation techniques, combined with analysis and correlation of identified outliers and/or other statistical anomalies, number of failures, critical tests, longest/shortest tests, or basic functionality issues associated with failure of the test. The supplementary data analysis may also provide identification of critical, marginal, and good parts as defined by sensitivity parameters in a recipe configuration file. Part identification may provide disposition/classification before packaging and/or shipping the part that may represent a reliability risk, and/or test time reduction through dynamic probe mapping of bad and good parts during wafer probe. Identification of these parts may be represented and output in any appropriate manner, for example as good and bad parts on a dynamically generated prober control map (for dynamic mapping), a wafer map used for offline inking equipment, a test strip map for strip testing at final test, a results file, and/or a database results table. Supplemental data analysis at the cell controller level tends to increase quality control at the probe, and this final test yields. In addition, quality issues may be identified at product run time, not later. Furthermore, the supplemental data analysis and signature analysis tends to improve the quality of data provided to the downstream and offline analysis tools, as well as test engineers or other personnel, by identifying outliers. For example, the computer 108 may include information on the wafer map identifying a group of components having signature analyses indicating a fault in the manufacturing process. Thus, the signature analysis system may identify potentially defective goods that went undetected using conventional test analysis. Referring now to FIG. 10, an array of semiconductor devices are positioned on a wafer. In this wafer, the general resistivity of resistor components in the semiconductor devices varies across the wafer, for example due to uneven deposition of material or treatment of the wafer. The resistance of any particular component, however, may be within the control limits of the test. For example, the target resistance of a particular resistor component may be 1000Ω+/−10%. Near the ends of the wafer, the resistances of most of the resistors approach, but do not exceed, the normal distribution range of 900Ω and 1100Ω (FIG. 11). Components on the wafer may include defects, for example due to a contaminant or imperfection in the fabrication process. The defect may increase the resistance of resistors located near the low-resistivity edge of the wafer to 1080Ω. The resistance is well over the 1000Ω expected for a device near the middle of the wafer, but is still well within the normal distribution range. Referring to FIGS. 12A-B, the raw test data for each component may be plotted. The test data exhibits considerable variation, due in part to the varying resistivity among components on the wafer as the prober indexes across rows or columns of devices. The devices affected by the defect are not easily identifiable based on visual examination of the test data or comparison to the test limits. When the test data is processed according to various aspects of the present invention, the devices affected by the defect may be associated with outliers in the test data. The test data is largely confined to a certain range of values. The data associated with the defects, however, is unlike the data for the surrounding components. Accordingly, the data illustrates the departure from the values associated with the surrounding devices without the defect. The outlier classification element may identify and classify the outliers according to the magnitude of the departure of the outlier data from the surrounding data. The output element 208 collects data from the test system 100, suitably at run time, and provides an output report to a printer, database, operator interface, or other desired destination. Any form, such as graphical, numerical, textual, printed, or electronic form, may be used to present the output report for use or subsequent analysis. The output element 208 may provide any selected content, including selected output test data from the tester 102 and results of the supplementary data analysis. In the present embodiment, the output element 208 suitably provides a selection of data from the output test data specified by the operator as well as supplemental data at product run time via the dynamic datalog. Referring to FIG. 7, the output element 208 initially reads a sampling range from the database 114 (step 702). The sampling range identifies predetermined information to be included in the output report. In the present embodiment, the sampling range identifies components 106 on the wafer selected by the operator for review. The predetermined components may be selected according to any criteria, such as data for various circumferential zones, radial zones, random components, or individual stepper fields. The sampling range comprises a set of x-y coordinates corresponding to the positions of the predetermined components on the wafer or an identified portion of the available components in a batch. The output element 208 may also be configured to include information relating to the outliers, or other information generated or identified by the supplementary data analysis element, in the dynamic datalog (step 704). If so configured, the identifiers, such as x-y coordinates, for each of the outliers are assembled as well. The coordinates for the operator-selected components and the outliers are merged into the dynamic datalog (step 706), which in the current embodiment is in the format of the native tester data output format. Merging resulting data into the dynamic datalog facilitates compression of the original data into summary statistics and critical raw data values into a smaller native tester data file, reducing data storage requirements without compromising data integrity for subsequent customer analysis. The output element 208 retrieves selected information, such as the raw test data and one or more data from the supplementary data analysis element 206, for each entry in the merged x-y coordinate array of the dynamic datalog (step 708). The retrieved information is then suitably stored in an appropriate output report (step 710). The report may be prepared in any appropriate format or manner. In the present embodiment, the output report suitably includes the dynamic datalog having a wafer map indicating the selected components on the wafer and their classification. Further, the output element 208 may superimpose wafer map data corresponding to outliers on the wafer map of the preselected components. Additionally, the output element may include only the outliers from the wafer map or batch as the sampled output. The output report may also include a series of graphical representation of the data to highlight the occurrence of outliers and correlations in the data. The output report may further include recommendations and supporting data for the recommendations. For example, if two tests appear to generate identical sets of failures and/or outliers, the output report may include a suggestion that the tests are redundant and recommend that one of the tests be omitted from the test program. The recommendation may include a graphical representation of the data showing the identical results of the tests. The output report may be provided in any suitable manner, for example output to a local workstation, sent to a server, activation of an alarm, or any other appropriate manner (step 712). In one embodiment, the output report may be provided off-line such that the output does not affect the operation of the system or transfer to the main server. In this configuration, the computer 108 copies data files, performs the analysis, and generates results, for example for demonstration or verification purposes. In addition to the supplementary analysis of the data on each wafer, a testing system 100 according to various aspects of the present invention may also perform composite analysis of the data and generate additional data to identify patterns and trends over multiple datasets, such as using multiple wafers and/or lots. Composite analysis is suitably performed to identify selected characteristics, such as patterns or irregularities, among multiple datasets. For example, multiple datasets may be analyzed for common characteristics that may represent patterns, trends, or irregularities over two or more datasets. The composite analysis may comprise any appropriate analysis for analyzing test data for common characteristics among the datasets, and may be implemented in any suitable manner. For example, in the present testing system 100, the composite analysis element 214 performs composite analysis of data derived from multiple wafers and/or lots. The test data for each wafer, lot, or other grouping forms a dataset. The composite analysis element 214 is suitably implemented as a software module operating on the computer 108. The composite analysis element 214 may be implemented, however, in any appropriate configuration, such as in a hardware solution or a combined hardware and software solution. Further, the composite analysis element 214 may be executed as using software executed on the test system computer 108 or a remote computer, such as an independent workstation or a third party's separate computer system. The composite analysis may be performed at run time, following the generation of one or more complete datasets, or upon a collection of data generated well before the composite analysis, including historical data. The composite analysis may use any data from two or more datasets. Composite analysis can receive several sets of input data, including raw data and filtered or smoothed data, for each wafer, such as by executing multiple configurations through the classification engine. Once received, the input data is suitably filtered using a series of user-defined rules, which can be defined as mathematical expressions, formulas, or any other criteria. The data is then analyzed to identify patterns or irregularities in the data. The composite data may also be merged into other data, such as the raw data or analyzed data, to generate an enhanced overall dataset. The composite analysis element 214 may then provide an appropriate output report that may be used to improve the test process. For example, the output report may provide information relating to issues in a manufacturing and/or testing process. In the present system, the composite analysis element 214 analyzes sets of wafer data in conjunction with user expressions or other suitable processes and a spatial analysis to build and establish composite maps that illustrate significant patterns or trends. Composite analysis can receive several different datasets and/or composite maps for any one set of wafers by executing multiple user configurations on the set of wafers. Referring to FIG. 13, in the present embodiment in the semiconductor testing environment, the composite analysis element 214 receives data from multiple datasets, such as the data from multiple wafers or lots (1310). The data may comprise any suitable data for analysis, such as raw data, filtered data, smoothed data, historical data from prior test runs, or data received from the tester at run time. In the present embodiment, the composite analysis element 214 receives raw data and filtered data at run time. The filtered data may comprise any suitable data for analysis, such as smoothed data and/or signature analysis data. In the present embodiment, the composite analysis element 214 receives the raw dataset and supplementary data generated by the supplementary data analysis element 206, such as the smoothed data, identification of failures, identification of outliers, signature analysis data, and/or other data. After receiving the raw data and the supplementary data, the composite analysis element 214 generates composite data for analysis (1312). The composite data comprises data representative of information from more than one dataset. For example, the composite data may comprise summary information relating to the number of failures and/or outliers for a particular test occurring for corresponding test data in different datasets, such as data for components at identical or similar positions on different wafers or in different lots. The composite data may, however, comprise any appropriate data, such as data relating to areas having concentrations of outliers or failures, wafer locations generating a significant number of outliers or failures, or other data derived from two or more datasets. The composite data is suitably generated by comparing data from the various datasets to identify patterns and irregularities among the datasets. For example, the composite data may be generated by an analysis engine configured to provide and analyze the composite data according to any suitable algorithm or process. In the present embodiment, the composite analysis element 214 includes a proximity engine configured to generate one or more composite masks based on the datasets. The composite analysis element 214 may also process the composite mask data, for example to refine or emphasize information in the composite mask data. In the present embodiment, the proximity engine receives multiple datasets, either through a file, memory structure, database, or other data store, performs a spatial analysis on those datasets (1320), and outputs the results in the form of a composite mask. The proximity engine may generate the composite mask data, such as a composite image for an overall dataset, according to any appropriate process or technique using any appropriate methods. In particular, the proximity engine suitably merges the composite data with original data (1322) and generates an output report for use by the user or another system (1324). The proximity engine may also be configured to refine or enhance the composite mask data for analysis, such as by spatial analysis, analyzing the data for recurring characteristics in the datasets, or removing data that does not meet selected criteria. In the present embodiment, the proximity engine performs composite mask generation 1312, and may also be configured to determine exclusion areas 1314, perform proximity weighting 1316, and detect and filter clusters 1318. The proximity engine may also provide proximity adjustment or other operations using user-defined rules, criteria, thresholds, and precedence. The result of the analysis is a composite mask of the inputted datasets that illustrates spatial trends and/or patterns found throughout the datasets given. The proximity engine can utilize any appropriate output method or medium, including memory structures, databases, other applications, and file-based data stores such as text files or XML files in which to output the composite mask. The proximity engine may use any appropriate technique to generate the composite mask data, including cumulative squared methods, N-points formulas, Western Electrical rules, or other user defined criteria or rules. In the present embodiment, composite mask data may be considered as an overall encompassing or “stacked” view of multiple datasets. The present proximity engine collects and analyzes data for corresponding data from multiple datasets to identify potential relationships or common characteristics in the data for the particular set of corresponding data. The data analyzed may be any appropriate data, including the raw data, smoothed data, signature analysis data, and/or any other suitable data. In the present embodiment, the proximity engine analyzes data for corresponding locations on multiple wafers. Referring to FIG. 14, each wafer has devices in corresponding locations that may be designated using an appropriate identification system, such as an x, y coordinate system. Thus, the proximity engine compares data for devices at corresponding locations or data points, such as location 10, 12 as shown in FIG. 14, to identify patterns in the composite set of data. The proximity engine of the present embodiment uses at least one of two different techniques for generating the composite mask data, a cumulative squared method and a formula-based method. The proximity engine suitably identifies data of interest by comparing the data to selected or calculated thresholds. In one embodiment, the proximity engine compares the data points at corresponding locations on the various wafers and/or lots to thresholds to determine whether the data indicate potential patterns across the datasets. The proximity engine compares each datum to one or more thresholds, each of which may be selected in any appropriate manner, such as a predefined value, a value calculated based on the current data, or a value calculated from historical data. For example, a first embodiment of the present proximity engine implements a cumulative squared method to compare the data to thresholds. In particular, referring to FIG. 15, the proximity engine suitably selects a first data point (1512) in a first dataset (1510), such as a result for a particular test for a particular device on a particular wafer in a particular lot, and compares the data point value to a count threshold (1514). The threshold may comprise any suitable value, and any type of threshold, such as a range, a lower limit, an upper limit, and the like, and may be selected according to any appropriate criteria. If the data point value exceeds the threshold, i.e., is lower than the threshold, higher than the threshold, within the threshold limits, or whatever the particular qualifying relationship may be, an absolute counter is incremented (1516) to generate a summary value corresponding to the data point. The data point value is also compared to a cumulative value threshold (1518). If the data point value exceeds the cumulative value threshold, the data point value is added to a cumulative value for the data point (1520) to generate another summary value for the data point. The proximity engine repeats the process for every corresponding data point (1522) in every relevant dataset (1524), such as every wafer in the lot or other selected group of wafers. Any other desired tests or comparisons may be performed as well for the data points and datasets. When all of the relevant data points in the population have been processed, the proximity engine may calculate values based on the selected data, such as data exceeding particular thresholds. For example, the proximity engine may calculate overall cumulative thresholds for each set of corresponding data based on the cumulative value for the relevant data point (1526). The overall cumulative threshold may be calculated in any appropriate manner to identify desired or relevant characteristics, such as to identify sets of corresponding data points that bear a relationship to a threshold. For example, the overall cumulative threshold (Limit) may be defined according to the following equation: Limit = Average + ( ScaleFactor * Standard ⁢ ⁢ Deviation 2 ) ( Max - Min ) ⁢ where Average is the mean value of the data in the composite population of data, Scale Factor is a value or variable selected to adjust the sensitivity of the cumulative squared method, Standard Deviation is the standard deviation of data point values in the composite population of data, and (Max−Min) is the difference between the highest and lowest data point values in the complete population of data. Generally, the overall cumulative threshold is defined to establish a comparison value for identifying data points of interest in the particular data set. Upon calculation of the overall cumulative threshold, the proximity engine determines whether to designate each data point for inclusion in the composite data, for example by comparing the count and cumulative values to thresholds. The proximity engine of the present embodiment suitably selects a first data point (1528), squares the total cumulative value for the data point (1530), and compares the squared cumulative value for the data point to the dynamically generated overall cumulative threshold (1532). If the squared cumulative value exceeds the overall cumulative threshold, then the data point is designated for inclusion in the composite data (1534). The absolute counter value for the data point may also be compared to an overall count threshold (1536), such as a pre-selected threshold or a calculated threshold based on, for example, a percentage of the number of wafers or other datasets in the population. If the absolute counter value exceeds the overall count threshold, then the data point may again be designated for inclusion in the composite data (1538). The process is suitably performed for each data point (1540). The proximity engine may also generate the composite mask data using other additional or alternative techniques. The present proximity engine may also utilize a formula-based system for generating the composite mask data. A formula-based system according to various aspects of the present invention uses variables and formulas, or expressions, to define a composite wafer mask. For example, in an exemplary formula-based system, one or more variables may be user-defined according to any suitable criteria. The variables are suitably defined for each data point in the relevant group. For example, the proximity engine may analyze each value in the data population for the particular data point, for example to calculate a value for the data point or count the number of times a calculation provides a particular result. The variables may be calculated for each data point in the dataset for each defined variable. After calculating the variables, the data points may be analyzed, such as to determine whether the data point meets the user-defined criteria. For example, a user-defined formula may be resolved using the calculated variable values, and if the formula equates to a particular value or range of values, the data point may be designated for inclusion in the composite mask data. Thus, the proximity engine may generate a set of composite mask data according to any suitable process or technique. The resulting composite mask data comprises a set of data that corresponds to the results of the data population for each data point. Consequently, characteristics for the data point may be identified over multiple datasets. For example, in the present embodiment, the composite mask data may illustrate particular device locations that share characteristics on multiple wafers, such as widely variable test results or high failure rates. Such information may indicate issues or characteristics in the manufacturing or design process, and thus may be used to improve and control manufacturing and testing. The composite mask data may also be analyzed to generate additional information. For example, the composite mask data may be analyzed to illustrate spatial trends and/or patterns in the datasets and/or identify or filter significant patterns, such as filtering to reduce clutter from relatively isolated data points, enhancing or refining areas having particular characteristics, or filtering data having known characteristics. The composite mask data of the present embodiment, for example, may be subjected to spatial analyses to smooth the composite mask data and complete patterns in the composite mask data. Selected exclusion zones may receive particular treatment, such that composite mask data may be removed, ignored, enhanced, accorded lower significance, or otherwise distinguished from other composite mask data. A cluster detection process may also remove or downgrade the importance of data point clusters that are relatively insignificant or unreliable. In the present embodiment, the proximity engine may be configured to identify particular designated zones in the composite mask data such that data points from the designated zones are accorded particular designated treatment or ignored in various analyses. For example, referring to FIG. 16, the proximity engine may establish an exclusion zone at a selected location on the wafers, such as individual devices, groups of devices, or a band of devices around the perimeter of the wafer. The purpose of the exclusion zone is to provide a mechanism to exclude certain data points from affecting other data points in proximity analysis and/or weighting. The data points are designated as excluded in any suitable manner, such as by assigning values that are out of the range of subsequent processes. The relevant zone may be identified in any suitable manner. For example, excluded data points may be designated using a file listing of device identifications or coordinates, such as x,y coordinates, selecting a particular width of band around the perimeter, or other suitable process for defining a relevant zone in the composite data. In the present embodiment, the proximity engine may define a band of excluded devices on a wafer using a simple calculation that causes the proximity engine to ignore or otherwise specially treat data points within a user defined range of the edge of the data set. For example, all devices within this range, or listed in the file, are then subject to selected exclusion criteria. If the exclusion criteria are met, the data points in the exclusion zone or the devices meeting the exclusion criteria are excluded from one or more analyses. The proximity engine of the present embodiment is suitably configured to perform additional analyses upon the composite mask data. The additional analyses may be configured for any appropriate purpose, such as to enhance desired data, remove unwanted data, or identify selected characteristics in the composite mask data. For example, the proximity engine is suitably configured to perform a proximity weighting process, such as based on a point weighting system, to smooth and complete patterns in the composite mask data. Referring to FIGS. 17A-B and 18, the present proximity engine searches through all data points in the dataset (1730). The proximity engine selects a first point (1710) and cheeks the value of the data point against a criterion, such as a threshold or a range of values (1712). When a data point is found that exceeds the selected threshold or is within the selected range, the proximity engine searches data points surrounding the main data point for values (1714). The number of data points around the main data point may be any selected number, and may he selected according to any suitable criteria. The proximity engine searches the surrounding data points for data points exceeding an influence value or satisfying another suitable criterion indicating that the data point should be accorded weight (1716). If the data point exceeds the influence value, the proximity engine suitably assigns a weight to the main data point according to the values of the surrounding data points. In addition, the proximity engine may adjust the weight according to the relative position of the surrounding datapoint. For example, the amount of weight accorded to a surrounding data point can be determined according to whether the surrounding data point is adjacent (1718) or diagonal (1720) to the main data point. The total weight may also be adjusted if the data point is on the edge of the wafer (1722). When all surrounding data points around the main data point have been checked (1724), the main data point is assigned an overall weight, for example by adding the weight factors from the surrounding data points. The weight for the main data point may then be compared to a threshold, such as a user defined threshold (1726). If the weight meets or exceeds the threshold, the data point is so designated (1728). The composite mask data may also be further analyzed to filter data. For example, in the present embodiment, the proximity engine may be configured to identify, and suitably remove, groups of data points that are smaller than a threshold, such as a user-specified threshold. Referring to FIGS. 19 and 20, the proximity engine of the present embodiment may be configured to define the groups, size them, and remove smaller groups. To define the groups, the proximity engine searches through every data point (1922) in the composite mask data for a data point satisfying a criterion. For example, the data points in the composite mask data may be separated into ranges of values and assigned index numbers. The proximity engine begins by searching the composite mask data for a data point matching a certain index (1910). Upon encountering a data point meeting designated index (1912), the proximity engine designates the found point as the main data point and initiates a recursive program that searches in all directions from the main data point for other data points that are in the same index, or alternatively, have substantially the same value, also exceed the threshold, or meet other desired criteria (1914). As an example of a recursive function in the present embodiment, the proximity engine may begin searching for data points having a certain value, for instance five. If a data point with a value of five is found, the recursive program searches all data points around the main device until it finds another data point with the value of five. If another qualifying data point is found, the recursive program selects the encountered data point as the main data point and repeats the process. Thus, the recursive process analyzes and marks all data points having matching values that are adjacent or diagonal to each other and thus form a group. When the recursive program has found all devices in a group having a certain value, the group is assigned a unique group index and the proximity engine again searches through the entire composite mask data. When all of the data values have been searched, the composite mask data is fully separated into groups of contiguous data points having the same group index. The proximity engine may determine the size of each group. For example, the proximity engine may count the number of data points in the group (1916). The proximity engine may then compare the number of data points in each group to a threshold and remove groups that do not meet the threshold (1918). The groups may be removed from the grouping analysis in any suitable manner (1920), such as by resetting the index value for the relevant group to a default value. For example, if the threshold number of data points is five, the proximity engine changes the group index number for every group having fewer than five data points to a default value. Consequently, the only groups that remain classified with different group indices are those having five or more data points. The proximity engine may perform any appropriate additional operations to generate and refine the composite mask data. For example, the composite mask data, including the results of the additional filtering, processing, and analyzing of the original composite mask data, may be used to provide information relating to the multiple datasets and the original source of the data, such as the devices on the wafers or the fabrication process. The data may be provided to the user or otherwise used in any suitable manner. For example, the data may be provided to another system for further analysis or combination with other data, such as executing user-defined rules combined with a merging operation on the composite mask data, the raw data, and any other appropriate data to produce a data set that represents trends and patterns in the raw data. Further, the data may be provided to a user via an appropriate output system, such as a printer or visual interface. In the present embodiment, for example, the composite mask data is combined with other data and provided to the user for review. The composite mask data may be combined with any other appropriate data in any suitable manner. For example, the composite mask data may be merged with signature data, the raw data, hardware bin data, software bin data, and/or other composite data. The merging of the datasets may be performed in any suitable manner, such as using various user-defined rules including expressions, thresholds, and precedence. In the present system, the composite analysis element 214 performs the merging process using an appropriate process to merge the composite mask data with an original map of composite data, such as a map of composite raw data, composite signature data, or composite bin data. For example, referring to FIG. 21, the composite analysis element 214 may merge the composite mask data with the original individual wafer data using an absolute merge system in which the composite mask data is fully merged with the original data map. Consequently, the composite mask data is merged with the original data map regardless of overlap or encompassment of existing patterns. If only one composite mask illustrates a pattern out of multiple composite masks, the pattern is included in the overall composite mask. Alternatively, the composite analysis element 214 may merge the data in conjunction with additional analysis. The composite analysis element 214 may filter data that may be irrelevant or insignificant. For example, referring to FIG. 22, the composite analysis element 214 may merge only data in the composite mask data that overlaps data in the original data map or in another composite mask, which tends to emphasize potentially related information. The composite analysis element 214 may alternatively evaluate the composite mask data and the original data to determine whether a particular threshold number, percentage, or other value of data points overlap between maps. Depending on the configuration, the data merged may only include areas where data points, in this case corresponding to devices, overlapped sufficiently between the composite mask data and the original data to meet the required threshold value for overlapping data points. Referring to FIG. 23, the composite analysis element 214 may be configured to include only composite data patterns that overlaps to a sufficient degree with tester bin failures, i.e., failed devices, in the original data, such as 50% of the composite data overlapping with tester bin failure data. Thus, if less than the minimum amount of composite data overlaps with the original data, the composite data pattern may be ignored. Similarly, referring to FIG. 24, the composite analysis element 214 may compare two different sets of composite data, such as data from two different recipes, and determine whether the overlap between the two recipes satisfies selected criteria. Only the data that overlaps and/or satisfies the minimum criteria is merged. The merged data may be provided to an output element for output to the user or other system. The merged data may be passed as input to another process, such as a production error identification process or a large trend identification process. The merged data may also be outputted in any assortment or format, such as memory structures, database tables, flat text files, or XML files. In the present embodiment, the merged data and/or wafer maps are provided into an ink map generation engine. The ink map engine produces maps for offline inking equipment. In addition to offline inking maps, the merged data results may be utilized in generating binning results for inkless assembly of parts, or any other process or application that utilizes these types of results. The particular implementations shown and described are merely illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. For the sake of brevity, conventional signal processing, data transmission, and other functional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system. The present invention has been described above with reference to a preferred embodiment. Changes and modifications may be made, however, without departing from the scope of the present invention. These and other changes or modifications are intended to be included within the scope of the present invention, as expressed in the following claims.
	claims	1. A neutron absorbing apparatus for insertion into a fuel rack comprising:a sleeve having a first wall and a second wall, the first and second walls forming a chevron shape; andthe first and second wall being a single panel of a metal matrix composite having neutron absorbing particulate reinforcement bent into the chevron shape along a crease by a bending process. 2. The neutron absorbing apparatus of claim 1 further comprising an L-shaped reinforcement bar connected to a top end of the sleeve. 3. The neutron absorbing apparatus of claim 1 wherein the metal matrix composite having neutron absorbing particulate reinforcement is a boron carbide aluminum matrix composite material, a boron carbide steel matrix composite material, a carborundum aluminum matrix composite material or a carborundum steel matrix composite material. 4. The neutron absorbing apparatus of claim 1 wherein the metal matrix composite metal having neutron absorbing particulate reinforcement is at least 20% by volume neutron absorbing particulate. 5. The neutron absorbing apparatus of claim 1 wherein the metal matrix composite having neutron absorbing particulate reinforcement is a boron carbide aluminum matrix composite material that is at least 20% by volume boron carbide. 6. The neutron absorbing apparatus of claim 1 wherein the metal matrix composite having neutron absorbing particulate reinforcement is a boron carbide aluminum matrix composite material that is at least 25% by volume boron carbide. 7. The neutron absorbing apparatus of claim 6 wherein the crease has a radius of curvature between 0.375 to 0.625 inches, and the single panel has a gauge thickness between 0.065 to 0.120 inches. 8. The neutron absorbing apparatus of claim 1 further comprising at least one top flange at a top end of the sleeve, the flange formed by bending the single panel of the metal matrix composite having neutron absorbing particulate reinforcement. 9. The neutron absorbing apparatus of claim 8 further comprising at least one bottom flange at a bottom end of the sleeve, the flange formed by bending the single panel of the metal matrix composite having neutron absorbing particulate reinforcement. 10. The neutron absorbing apparatus of claim 9 wherein the sleeve has a central longitudinal axis, and wherein the at least one top flange extends from the sleeve away from the central longitudinal axis and the at least one bottom flange extends from the sleeve toward the central longitudinal axis. 11. The neutron absorbing apparatus of claim 1 further comprising:at least one bottom flange at a bottom end of the sleeve, the flange formed by bending the single panel of the metal matrix composite having neutron absorbing particulate reinforcement;wherein the sleeve has a central longitudinal axis; andwherein the at least one bottom flange extends from the sleeve toward the central longitudinal axis. 12. A system for supporting spent nuclear fuel in a submerged environment comprising:a fuel rack comprising a base plate and a gridwork of walls extending from the base plate so as to form an array of cells;a fuel assembly positioned within at least one of the cells of the fuel rack;at least one neutron absorbing insert comprising a sleeve having a first wall and a second wall, the first and second wall forming a chevron shape, and the first and second wall being a single panel of a metal matrix composite having neutron absorbing particulate reinforcement, the single panel bent into the chevron shape by a bending process; andthe neutron absorbing insert positioned within the cell of the fuel rack so that the sleeve is located between the fuel assembly and the walls of the fuel rack. 13. The system of claim 12 wherein the metal matrix composite having neutron absorbing particulate reinforcement is a boron carbide aluminum matrix composite material, a boron carbide steel matrix composite material, a carborundum aluminum matrix composite material or a carborundum steel matrix composite material. 14. The system of claim 12 wherein the metal matrix composite having neutron absorbing particulate reinforcement is a boron carbide aluminum matrix composite material that is at least 25% by volume boron carbide. 15. The system of claim 14 wherein the crease has a radius of curvature between 0.375 to 0.625 inches, and the single panel has a gauge thickness between 0.065 to 0.120 inches. 16. The system of claim 12 further comprising at least one top flange at a top end of the sleeve, the flange formed by bending the single panel of the metal matrix composite having neutron absorbing particulate reinforcement. 17. The system of claim 16 wherein the sleeve has a central longitudinal axis, and wherein the at least one top flange extends from the sleeve away from the central longitudinal axis in an inclined orientation so as to form a funnel into the cell. 18. The system of claim 12 further comprising further comprising:at least one bottom flange at a bottom end of the sleeve, the flange formed by bending the single panel of the metal matrix composite having neutron absorbing particulate reinforcement;wherein the sleeve has a central longitudinal axis;wherein the bottom flange extends from the sleeve toward the central longitudinal axis, the bottom flange resting on a top surface of the base plate of the fuel rack. 19. The system of claim 18 further comprising:a plate that is a separate and non-unitary structure from the neutron absorbing insert, the plate comprising a central hole and a plurality of barbs extending downward from plate about the central hole; andthe plate positioned within the cell below the fuel assembly and atop the bottom flange of the neutron absorbing insert so that the barbs extend into a flow hole in the base plate of the fuel rack and engage the base plate of the fuel rack, the bottom flange of the neutron absorbing insert being compressed between the plate and the base plate. 20. A method of manufacturing a neutron absorbing apparatus comprising:a) providing a roll of boron carbide aluminum matrix composite;b) hot rolling the roll of boron carbide aluminum matrix composite;c) straightening and flattening the roll of boron carbide aluminum matrix composite using a hot roll leveler to create a single panel of boron carbide aluminum matrix composite;d) shearing the single panel of boron carbide aluminum matrix composite to a desired geometry; ande) bending the single panel boron carbide aluminum matrix composite into a chevron shape having first and second longitudinal walls. 21. The method of claim 20 wherein the panel of boron carbide aluminum matrix composite is maintained at a temperature above 750 degrees Fahrenheit during the bending step. 22. The method of claim 21 wherein the bending is performed with a brake press having a brake punch and a die, and wherein the brake press and die are heated to a temperature greater than above 500 degrees Fahrenheit during the bending step.
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